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# (C) Copyright 2000 - 2013
# Wolfgang Denk, DENX Software Engineering,
# SPDX-License-Identifier: GPL-2.0+
This directory contains the source code for U-Boot, a boot loader for
Embedded boards based on PowerPC, ARM, MIPS and several other
processors, which can be installed in a boot ROM and used to
initialize and test the hardware or to download and run application
The development of U-Boot is closely related to Linux: some parts of
the source code originate in the Linux source tree, we have some
header files in common, and special provision has been made to
support booting of Linux images.
Some attention has been paid to make this software easily
configurable and extendable. For instance, all monitor commands are
implemented with the same call interface, so that it's very easy to
add new commands. Also, instead of permanently adding rarely used
code (for instance hardware test utilities) to the monitor, you can
load and run it dynamically.
In general, all boards for which a configuration option exists in the
Makefile have been tested to some extent and can be considered
"working". In fact, many of them are used in production systems.
In case of problems see the CHANGELOG file to find out who contributed
the specific port. In addition, there are various MAINTAINERS files
scattered throughout the U-Boot source identifying the people or
companies responsible for various boards and subsystems.
Note: As of August, 2010, there is no longer a CHANGELOG file in the
actual U-Boot source tree; however, it can be created dynamically
from the Git log using:
Where to get help:
In case you have questions about, problems with or contributions for
U-Boot, you should send a message to the U-Boot mailing list at
<>. There is also an archive of previous traffic
on the mailing list - please search the archive before asking FAQ's.
Please see and
Where to get source code:
The U-Boot source code is maintained in the Git repository at
git:// ; you can browse it online at;a=summary
The "snapshot" links on this page allow you to download tarballs of
any version you might be interested in. Official releases are also
available for FTP download from the
Pre-built (and tested) images are available from
Where we come from:
- start from 8xxrom sources
- create PPCBoot project (
- clean up code
- make it easier to add custom boards
- make it possible to add other [PowerPC] CPUs
- extend functions, especially:
* Provide extended interface to Linux boot loader
* S-Record download
* network boot
* PCMCIA / CompactFlash / ATA disk / SCSI ... boot
- create ARMBoot project (
- add other CPU families (starting with ARM)
- create U-Boot project (
- current project page: see
Names and Spelling:
The "official" name of this project is "Das U-Boot". The spelling
"U-Boot" shall be used in all written text (documentation, comments
in source files etc.). Example:
This is the README file for the U-Boot project.
File names etc. shall be based on the string "u-boot". Examples:
#include <asm/u-boot.h>
Variable names, preprocessor constants etc. shall be either based on
the string "u_boot" or on "U_BOOT". Example:
U_BOOT_VERSION u_boot_logo
IH_OS_U_BOOT u_boot_hush_start
Starting with the release in October 2008, the names of the releases
were changed from numerical release numbers without deeper meaning
into a time stamp based numbering. Regular releases are identified by
names consisting of the calendar year and month of the release date.
Additional fields (if present) indicate release candidates or bug fix
releases in "stable" maintenance trees.
U-Boot v2009.11 - Release November 2009
U-Boot v2009.11.1 - Release 1 in version November 2009 stable tree
U-Boot v2010.09-rc1 - Release candidate 1 for September 2010 release
Directory Hierarchy:
/arch Architecture specific files
/arc Files generic to ARC architecture
/arm Files generic to ARM architecture
/avr32 Files generic to AVR32 architecture
/blackfin Files generic to Analog Devices Blackfin architecture
/m68k Files generic to m68k architecture
/microblaze Files generic to microblaze architecture
/mips Files generic to MIPS architecture
/nds32 Files generic to NDS32 architecture
/nios2 Files generic to Altera NIOS2 architecture
/openrisc Files generic to OpenRISC architecture
/powerpc Files generic to PowerPC architecture
/sandbox Files generic to HW-independent "sandbox"
/sh Files generic to SH architecture
/sparc Files generic to SPARC architecture
/x86 Files generic to x86 architecture
/api Machine/arch independent API for external apps
/board Board dependent files
/cmd U-Boot commands functions
/common Misc architecture independent functions
/configs Board default configuration files
/disk Code for disk drive partition handling
/doc Documentation (don't expect too much)
/drivers Commonly used device drivers
/dts Contains Makefile for building internal U-Boot fdt.
/examples Example code for standalone applications, etc.
/fs Filesystem code (cramfs, ext2, jffs2, etc.)
/include Header Files
/lib Library routines generic to all architectures
/Licenses Various license files
/net Networking code
/post Power On Self Test
/scripts Various build scripts and Makefiles
/test Various unit test files
/tools Tools to build S-Record or U-Boot images, etc.
Software Configuration:
Configuration is usually done using C preprocessor defines; the
rationale behind that is to avoid dead code whenever possible.
There are two classes of configuration variables:
* Configuration _OPTIONS_:
These are selectable by the user and have names beginning with
* Configuration _SETTINGS_:
These depend on the hardware etc. and should not be meddled with if
you don't know what you're doing; they have names beginning with
Previously, all configuration was done by hand, which involved creating
symbolic links and editing configuration files manually. More recently,
U-Boot has added the Kbuild infrastructure used by the Linux kernel,
allowing you to use the "make menuconfig" command to configure your
Selection of Processor Architecture and Board Type:
For all supported boards there are ready-to-use default
configurations available; just type "make <board_name>_defconfig".
Example: For a TQM823L module type:
cd u-boot
make TQM823L_defconfig
Note: If you're looking for the default configuration file for a board
you're sure used to be there but is now missing, check the file
doc/README.scrapyard for a list of no longer supported boards.
Sandbox Environment:
U-Boot can be built natively to run on a Linux host using the 'sandbox'
board. This allows feature development which is not board- or architecture-
specific to be undertaken on a native platform. The sandbox is also used to
run some of U-Boot's tests.
See board/sandbox/README.sandbox for more details.
Board Initialisation Flow:
This is the intended start-up flow for boards. This should apply for both
SPL and U-Boot proper (i.e. they both follow the same rules).
Note: "SPL" stands for "Secondary Program Loader," which is explained in
more detail later in this file.
At present, SPL mostly uses a separate code path, but the function names
and roles of each function are the same. Some boards or architectures
may not conform to this. At least most ARM boards which use
CONFIG_SPL_FRAMEWORK conform to this.
Execution typically starts with an architecture-specific (and possibly
CPU-specific) start.S file, such as:
- arch/arm/cpu/armv7/start.S
- arch/powerpc/cpu/mpc83xx/start.S
- arch/mips/cpu/start.S
and so on. From there, three functions are called; the purpose and
limitations of each of these functions are described below.
- purpose: essential init to permit execution to reach board_init_f()
- no global_data or BSS
- there is no stack (ARMv7 may have one but it will soon be removed)
- must not set up SDRAM or use console
- must only do the bare minimum to allow execution to continue to
- this is almost never needed
- return normally from this function
- purpose: set up the machine ready for running board_init_r():
i.e. SDRAM and serial UART
- global_data is available
- stack is in SRAM
- BSS is not available, so you cannot use global/static variables,
only stack variables and global_data
Non-SPL-specific notes:
- dram_init() is called to set up DRAM. If already done in SPL this
can do nothing
SPL-specific notes:
- you can override the entire board_init_f() function with your own
version as needed.
- preloader_console_init() can be called here in extremis
- should set up SDRAM, and anything needed to make the UART work
- these is no need to clear BSS, it will be done by crt0.S
- must return normally from this function (don't call board_init_r()
Here the BSS is cleared. For SPL, if CONFIG_SPL_STACK_R is defined, then at
this point the stack and global_data are relocated to below
CONFIG_SPL_STACK_R_ADDR. For non-SPL, U-Boot is relocated to run at the top of
- purpose: main execution, common code
- global_data is available
- SDRAM is available
- BSS is available, all static/global variables can be used
- execution eventually continues to main_loop()
Non-SPL-specific notes:
- U-Boot is relocated to the top of memory and is now running from
SPL-specific notes:
- stack is optionally in SDRAM, if CONFIG_SPL_STACK_R is defined and
- preloader_console_init() can be called here - typically this is
done by defining CONFIG_SPL_BOARD_INIT and then supplying a
spl_board_init() function containing this call
- loads U-Boot or (in falcon mode) Linux
Configuration Options:
Configuration depends on the combination of board and CPU type; all
such information is kept in a configuration file
Example: For a TQM823L module, all configuration settings are in
Many of the options are named exactly as the corresponding Linux
kernel configuration options. The intention is to make it easier to
build a config tool - later.
The following options need to be configured:
- CPU Type: Define exactly one, e.g. CONFIG_MPC85XX.
- Board Type: Define exactly one, e.g. CONFIG_MPC8540ADS.
- CPU Daughterboard Type: (if CONFIG_ATSTK1000 is defined)
Define exactly one, e.g. CONFIG_ATSTK1002
- Marvell Family Member
CONFIG_SYS_MVFS - define it if you want to enable
multiple fs option at one time
for marvell soc family
- 8xx CPU Options: (if using an MPC8xx CPU)
CONFIG_8xx_GCLK_FREQ - deprecated: CPU clock if
get_gclk_freq() cannot work
e.g. if there is no 32KHz
reference PIT/RTC clock
CONFIG_8xx_OSCLK - PLL input clock (either EXTCLK
- 859/866/885 CPU options: (if using a MPC859 or MPC866 or MPC885 CPU):
See doc/README.MPC866
Define this to measure the actual CPU clock instead
of relying on the correctness of the configured
values. Mostly useful for board bringup to make sure
the PLL is locked at the intended frequency. Note
that this requires a (stable) reference clock (32 kHz
Define this option if you want to enable the
ICache only when Code runs from RAM.
- 85xx CPU Options:
Specifies that the core is a 64-bit PowerPC implementation (implements
the "64" category of the Power ISA). This is necessary for ePAPR
compliance, among other possible reasons.
Defines the core time base clock divider ratio compared to the
system clock. On most PQ3 devices this is 8, on newer QorIQ
devices it can be 16 or 32. The ratio varies from SoC to Soc.
Defines the string to utilize when trying to match PCIe device
tree nodes for the given platform.
Enables a workaround for erratum A004510. If set,
Defines one or two SoC revisions (low 8 bits of SVR)
for which the A004510 workaround should be applied.
The rest of SVR is either not relevant to the decision
of whether the erratum is present (e.g. p2040 versus
p2041) or is implied by the build target, which controls
whether CONFIG_SYS_FSL_ERRATUM_A004510 is set.
See Freescale App Note 4493 for more information about
this erratum.
Enables a workaround for IFC erratum A003399. It is only
required during NOR boot.
Enables a workaround for T1040/T1042 erratum A008044. It is only
required during NAND boot and valid for Rev 1.0 SoC revision
This is the value to write into CCSR offset 0x18600
according to the A004510 workaround.
This value denotes start offset of DDR memory which is
connected exclusively to the DSP cores.
This value denotes start offset of M2 memory
which is directly connected to the DSP core.
This value denotes start offset of M3 memory which is directly
connected to the DSP core.
This value denotes start offset of DSP CCSR space.
Single Source Clock is clocking mode present in some of FSL SoC's.
In this mode, a single differential clock is used to supply
clocks to the sysclock, ddrclock and usbclock.
This CONFIG is defined when the CPC is configured as SRAM at the
time of U-Boot entry and is required to be re-initialized.
Indicates this SoC supports deep sleep feature. If deep sleep is
supported, core will start to execute uboot when wakes up.
- Generic CPU options:
Defines global data is initialized in generic board board_init_f().
If this macro is defined, global data is created and cleared in
generic board board_init_f(). Without this macro, architecture/board
should initialize global data before calling board_init_f().
Defines the endianess of the CPU. Implementation of those
values is arch specific.
Freescale DDR driver in use. This type of DDR controller is
found in mpc83xx, mpc85xx, mpc86xx as well as some ARM core
Freescale DDR memory-mapped register base.
Specify emulator support for DDR. Some DDR features such as
deskew training are not available.
Freescale DDR1 controller.
Freescale DDR2 controller.
Freescale DDR3 controller.
Freescale DDR4 controller.
Freescale DDR3 controller for ARM-based SoCs.
Board config to use DDR1. It can be enabled for SoCs with
Freescale DDR1 or DDR2 controllers, depending on the board
Board config to use DDR2. It can be enabled for SoCs with
Freescale DDR2 or DDR3 controllers, depending on the board
Board config to use DDR3. It can be enabled for SoCs with
Freescale DDR3 or DDR3L controllers.
Board config to use DDR3L. It can be enabled for SoCs with
DDR3L controllers.
Board config to use DDR4. It can be enabled for SoCs with
DDR4 controllers.
Defines the IFC controller register space as Big Endian
Defines the IFC controller register space as Little Endian
Defines divider of platform clock(clock input to IFC controller).
Defines divider of platform clock(clock input to eLBC controller).
It enables addition of RCW (Power on reset configuration) in built image.
Please refer doc/README.pblimage for more details
It adds PBI(pre-boot instructions) commands in u-boot build image.
PBI commands can be used to configure SoC before it starts the execution.
Please refer doc/README.pblimage for more details
It adds a target to create boot binary having SPL binary in PBI format
concatenated with u-boot binary.
Defines the DDR controller register space as Big Endian
Defines the DDR controller register space as Little Endian
Physical address from the view of DDR controllers. It is the
same as CONFIG_SYS_DDR_SDRAM_BASE for all Power SoCs. But
it could be different for ARM SoCs.
DDR controller interleaving on 256-byte. This is a special
interleaving mode, handled by Dickens for Freescale layerscape
SoCs with ARM core.
Number of controllers used as main memory.
Number of controllers used for other than main memory.
Defines the SoC has DP-DDR used for DPAA.
Defines the SEC controller register space as Big Endian
Defines the SEC controller register space as Little Endian
- MIPS CPU options:
Offset relative to CONFIG_SYS_SDRAM_BASE for initial stack
pointer. This is needed for the temporary stack before
Cache operation mode for the MIPS CPU.
See also arch/mips/include/asm/mipsregs.h.
Possible values are:
Special option for Lantiq XWAY SoCs for booting from NOR flash.
See also arch/mips/cpu/mips32/start.S.
Enable compilation of tools/xway-swap-bytes needed for Lantiq
XWAY SoCs for booting from NOR flash. The U-Boot image needs to
be swapped if a flash programmer is used.
- ARM options:
Select high exception vectors of the ARM core, e.g., do not
clear the V bit of the c1 register of CP15.
Use this flag to build U-Boot using the Thumb instruction
set for ARM architectures. Thumb instruction set provides
better code density. For ARM architectures that support
Thumb2 this flag will result in Thumb2 code generated by
Generic timer clock source frequency.
Generic timer clock source frequency if the real clock is
different from COUNTER_FREQUENCY, and can only be determined
at run time.
- Tegra SoC options:
Support executing U-Boot in non-secure (NS) mode. Certain
impossible actions will be skipped if the CPU is in NS mode,
such as ARM architectural timer initialization.
- Linux Kernel Interface:
U-Boot stores all clock information in Hz
internally. For binary compatibility with older Linux
kernels (which expect the clocks passed in the
bd_info data to be in MHz) the environment variable
"clocks_in_mhz" can be defined so that U-Boot
converts clock data to MHZ before passing it to the
Linux kernel.
When CONFIG_CLOCKS_IN_MHZ is defined, a definition of
"clocks_in_mhz=1" is automatically included in the
default environment.
CONFIG_MEMSIZE_IN_BYTES [relevant for MIPS only]
When transferring memsize parameter to Linux, some versions
expect it to be in bytes, others in MB.
Define CONFIG_MEMSIZE_IN_BYTES to make it in bytes.
New kernel versions are expecting firmware settings to be
passed using flattened device trees (based on open firmware
* New libfdt-based support
* Adds the "fdt" command
* The bootm command automatically updates the fdt
OF_CPU - The proper name of the cpus node (only required for
MPC512X and MPC5xxx based boards).
OF_SOC - The proper name of the soc node (only required for
MPC512X and MPC5xxx based boards).
OF_TBCLK - The timebase frequency.
OF_STDOUT_PATH - The path to the console device
boards with QUICC Engines require OF_QE to set UCC MAC
Board code has addition modification that it wants to make
to the flat device tree before handing it off to the kernel
Other code has addition modification that it wants to make
to the flat device tree before handing it off to the kernel.
This causes ft_system_setup() to be called before booting
the kernel.
U-Boot can detect if an IDE device is present or not.
If not, and this new config option is activated, U-Boot
removes the ATA node from the DTS before booting Linux,
so the Linux IDE driver does not probe the device and
crash. This is needed for buggy hardware (uc101) where
no pull down resistor is connected to the signal IDE5V_DD7.
CONFIG_MACH_TYPE [relevant for ARM only][mandatory]
This setting is mandatory for all boards that have only one
machine type and must be used to specify the machine type
number as it appears in the ARM machine registry
Only boards that have multiple machine types supported
in a single configuration file and the machine type is
runtime discoverable, do not have to use this setting.
- vxWorks boot parameters:
bootvx constructs a valid bootline using the following
environments variables: bootdev, bootfile, ipaddr, netmask,
serverip, gatewayip, hostname, othbootargs.
It loads the vxWorks image pointed bootfile.
Note: If a "bootargs" environment is defined, it will overwride
the defaults discussed just above.
- Cache Configuration:
CONFIG_SYS_ICACHE_OFF - Do not enable instruction cache in U-Boot
CONFIG_SYS_DCACHE_OFF - Do not enable data cache in U-Boot
CONFIG_SYS_L2CACHE_OFF- Do not enable L2 cache in U-Boot
- Cache Configuration for ARM:
CONFIG_SYS_L2_PL310 - Enable support for ARM PL310 L2 cache
CONFIG_SYS_PL310_BASE - Physical base address of PL310
controller register space
- Serial Ports:
Define this if you want support for Amba PrimeCell PL010 UARTs.
Define this if you want support for Amba PrimeCell PL011 UARTs.
If you have Amba PrimeCell PL011 UARTs, set this variable to
the clock speed of the UARTs.
If you have Amba PrimeCell PL010 or PL011 UARTs on your board,
define this to a list of base addresses for each (supported)
port. See e.g. include/configs/versatile.h
Define this variable to enable hw flow control in serial driver.
Current user of this option is drivers/serial/nsl16550.c driver
- Console Interface:
Depending on board, define exactly one serial port
CONFIG_8xx_CONS_SCC1, ...), or switch off the serial
console by defining CONFIG_8xx_CONS_NONE
Note: if CONFIG_8xx_CONS_NONE is defined, the serial
port routines must be defined elsewhere
(i.e. serial_init(), serial_getc(), ...)
- Console Baudrate:
Select one of the baudrates listed in
- Console Rx buffer length
With CONFIG_SYS_SMC_RXBUFLEN it is possible to define
the maximum receive buffer length for the SMC.
This option is actual only for 82xx and 8xx possible.
must be defined, to setup the maximum idle timeout for
the SMC.
- Autoboot Command:
Only needed when CONFIG_BOOTDELAY is enabled;
define a command string that is automatically executed
when no character is read on the console interface
within "Boot Delay" after reset.
This can be used to pass arguments to the bootm
command. The value of CONFIG_BOOTARGS goes into the
environment value "bootargs".
The value of these goes into the environment as
"ramboot" and "nfsboot" respectively, and can be used
as a convenience, when switching between booting from
RAM and NFS.
- Bootcount:
Implements a mechanism for detecting a repeating reboot
cycle, see:
If no softreset save registers are found on the hardware
"bootcount" is stored in the environment. To prevent a
saveenv on all reboots, the environment variable
"upgrade_available" is used. If "upgrade_available" is
0, "bootcount" is always 0, if "upgrade_available" is
1 "bootcount" is incremented in the environment.
So the Userspace Applikation must set the "upgrade_available"
and "bootcount" variable to 0, if a boot was successfully.
- Pre-Boot Commands:
When this option is #defined, the existence of the
environment variable "preboot" will be checked
immediately before starting the CONFIG_BOOTDELAY
countdown and/or running the auto-boot command resp.
entering interactive mode.
This feature is especially useful when "preboot" is
automatically generated or modified. For an example
see the LWMON board specific code: here "preboot" is
modified when the user holds down a certain
combination of keys on the (special) keyboard when
booting the systems
- Serial Download Echo Mode:
If defined to 1, all characters received during a
serial download (using the "loads" command) are
echoed back. This might be needed by some terminal
emulations (like "cu"), but may as well just take
time on others. This setting #define's the initial
value of the "loads_echo" environment variable.
- Kgdb Serial Baudrate: (if CONFIG_CMD_KGDB is defined)
Select one of the baudrates listed in
- Monitor Functions:
Monitor commands can be included or excluded
from the build by using the #include files
<config_cmd_all.h> and #undef'ing unwanted
commands, or adding #define's for wanted commands.
The default command configuration includes all commands
except those marked below with a "*".
CONFIG_CMD_AES AES 128 CBC encrypt/decrypt
CONFIG_CMD_ASKENV * ask for env variable
CONFIG_CMD_BEDBUG * Include BedBug Debugger
CONFIG_CMD_BSP * Board specific commands
CONFIG_CMD_BOOTI * ARM64 Linux kernel Image support
CONFIG_CMD_CACHE * icache, dcache
CONFIG_CMD_CLK * clock command support
CONFIG_CMD_CRC32 * crc32
CONFIG_CMD_DATE * support for RTC, date/time...
CONFIG_CMD_DIAG * Diagnostics
CONFIG_CMD_DS4510 * ds4510 I2C gpio commands
CONFIG_CMD_DS4510_INFO * ds4510 I2C info command
CONFIG_CMD_DS4510_MEM * ds4510 I2C eeprom/sram commansd
CONFIG_CMD_DS4510_RST * ds4510 I2C rst command
CONFIG_CMD_DTT * Digital Therm and Thermostat
CONFIG_CMD_ECHO echo arguments
CONFIG_CMD_EDITENV edit env variable
CONFIG_CMD_EEPROM * EEPROM read/write support
CONFIG_CMD_EEPROM_LAYOUT* EEPROM layout aware commands
CONFIG_CMD_ELF * bootelf, bootvx
CONFIG_CMD_ENV_CALLBACK * display details about env callbacks
CONFIG_CMD_ENV_FLAGS * display details about env flags
CONFIG_CMD_ENV_EXISTS * check existence of env variable
CONFIG_CMD_EXPORTENV * export the environment
CONFIG_CMD_EXT2 * ext2 command support
CONFIG_CMD_EXT4 * ext4 command support
CONFIG_CMD_FS_GENERIC * filesystem commands (e.g. load, ls)
that work for multiple fs types
CONFIG_CMD_FS_UUID * Look up a filesystem UUID
CONFIG_CMD_FDC * Floppy Disk Support
CONFIG_CMD_FAT * FAT command support
CONFIG_CMD_FLASH flinfo, erase, protect
CONFIG_CMD_FPGA FPGA device initialization support
CONFIG_CMD_FUSE * Device fuse support
CONFIG_CMD_GETTIME * Get time since boot
CONFIG_CMD_GO * the 'go' command (exec code)
CONFIG_CMD_GREPENV * search environment
CONFIG_CMD_HASH * calculate hash / digest
CONFIG_CMD_I2C * I2C serial bus support
CONFIG_CMD_IDE * IDE harddisk support
CONFIG_CMD_IMLS List all images found in NOR flash
CONFIG_CMD_IMLS_NAND * List all images found in NAND flash
CONFIG_CMD_IMMAP * IMMR dump support
CONFIG_CMD_IOTRACE * I/O tracing for debugging
CONFIG_CMD_IMPORTENV * import an environment
CONFIG_CMD_INI * import data from an ini file into the env
CONFIG_CMD_IRQ * irqinfo
CONFIG_CMD_ITEST Integer/string test of 2 values
CONFIG_CMD_LDRINFO * ldrinfo (display Blackfin loader)
CONFIG_CMD_LINK_LOCAL * link-local IP address auto-configuration
CONFIG_CMD_MD5SUM * print md5 message digest
CONFIG_CMD_MEMINFO * Display detailed memory information
CONFIG_CMD_MEMORY md, mm, nm, mw, cp, cmp, crc, base,
loop, loopw
CONFIG_CMD_MISC Misc functions like sleep etc
CONFIG_CMD_MMC * MMC memory mapped support
CONFIG_CMD_MII * MII utility commands
CONFIG_CMD_MTDPARTS * MTD partition support
CONFIG_CMD_NET bootp, tftpboot, rarpboot
CONFIG_CMD_PCA953X * PCA953x I2C gpio commands
CONFIG_CMD_PCA953X_INFO * PCA953x I2C gpio info command
CONFIG_CMD_PCI * pciinfo
CONFIG_CMD_READ * Read raw data from partition
CONFIG_CMD_REGINFO * Register dump
CONFIG_CMD_RUN run command in env variable
CONFIG_CMD_SANDBOX * sb command to access sandbox features
CONFIG_CMD_SAVES * save S record dump
CONFIG_CMD_SDRAM * print SDRAM configuration information
(requires CONFIG_CMD_I2C)
CONFIG_CMD_SETGETDCR Support for DCR Register access
(4xx only)
CONFIG_CMD_SF * Read/write/erase SPI NOR flash
CONFIG_CMD_SHA1SUM * print sha1 memory digest
CONFIG_CMD_SOFTSWITCH * Soft switch setting command for BF60x
CONFIG_CMD_SOURCE "source" command Support
CONFIG_CMD_SPI * SPI serial bus support
CONFIG_CMD_TFTPSRV * TFTP transfer in server mode
CONFIG_CMD_TFTPPUT * TFTP put command (upload)
CONFIG_CMD_TIME * run command and report execution time (ARM specific)
CONFIG_CMD_TIMER * access to the system tick timer
CONFIG_CMD_CDP * Cisco Discover Protocol support
CONFIG_CMD_MFSL * Microblaze FSL support
CONFIG_CMD_XIMG Load part of Multi Image
CONFIG_CMD_UUID * Generate random UUID or GUID string
EXAMPLE: If you want all functions except of network
support you can write:
#include "config_cmd_all.h"
Other Commands:
fdt (flattened device tree) command: CONFIG_OF_LIBFDT
Note: Don't enable the "icache" and "dcache" commands
(configuration option CONFIG_CMD_CACHE) unless you know
what you (and your U-Boot users) are doing. Data
cache cannot be enabled on systems like the 8xx or
8260 (where accesses to the IMMR region must be
uncached), and it cannot be disabled on all other
systems where we (mis-) use the data cache to hold an
initial stack and some data.
XXX - this list needs to get updated!
- Removal of commands
If no commands are needed to boot, you can disable
CONFIG_CMDLINE to remove them. In this case, the command line
will not be available, and when U-Boot wants to execute the
boot command (on start-up) it will call board_run_command()
instead. This can reduce image size significantly for very
simple boot procedures.
- Regular expression support:
If this variable is defined, U-Boot is linked against
the SLRE (Super Light Regular Expression) library,
which adds regex support to some commands, as for
example "env grep" and "setexpr".
- Device tree:
If this variable is defined, U-Boot will use a device tree
to configure its devices, instead of relying on statically
compiled #defines in the board file. This option is
experimental and only available on a few boards. The device
tree is available in the global data as gd->fdt_blob.
U-Boot needs to get its device tree from somewhere. This can
be done using one of the two options below:
If this variable is defined, U-Boot will embed a device tree
binary in its image. This device tree file should be in the
board directory and called <soc>-<board>.dts. The binary file
is then picked up in board_init_f() and made available through
the global data structure as gd->blob.
If this variable is defined, U-Boot will build a device tree
binary. It will be called u-boot.dtb. Architecture-specific
code will locate it at run-time. Generally this works by:
cat u-boot.bin u-boot.dtb >image.bin
and in fact, U-Boot does this for you, creating a file called
u-boot-dtb.bin which is useful in the common case. You can
still use the individual files if you need something more
- Watchdog:
If this variable is defined, it enables watchdog
support for the SoC. There must be support in the SoC
specific code for a watchdog. For the 8xx and 8260
CPUs, the SIU Watchdog feature is enabled in the SYPCR
register. When supported for a specific SoC is
available, then no further board specific code should
be needed to use it.
When using a watchdog circuitry external to the used
SoC, then define this variable and provide board
specific code for the "hw_watchdog_reset" function.
specify the timeout in seconds. default 2 seconds.
- U-Boot Version:
If this variable is defined, an environment variable
named "ver" is created by U-Boot showing the U-Boot
version as printed by the "version" command.
Any change to this variable will be reverted at the
next reset.
- Real-Time Clock:
When CONFIG_CMD_DATE is selected, the type of the RTC
has to be selected, too. Define exactly one of the
following options:
CONFIG_RTC_MPC8xx - use internal RTC of MPC8xx
CONFIG_RTC_PCF8563 - use Philips PCF8563 RTC
CONFIG_RTC_MC13XXX - use MC13783 or MC13892 RTC
CONFIG_RTC_MC146818 - use MC146818 RTC
CONFIG_RTC_DS1307 - use Maxim, Inc. DS1307 RTC
CONFIG_RTC_DS1337 - use Maxim, Inc. DS1337 RTC
CONFIG_RTC_DS1338 - use Maxim, Inc. DS1338 RTC
CONFIG_RTC_DS1339 - use Maxim, Inc. DS1339 RTC
CONFIG_RTC_DS164x - use Dallas DS164x RTC
CONFIG_RTC_ISL1208 - use Intersil ISL1208 RTC
CONFIG_RTC_MAX6900 - use Maxim, Inc. MAX6900 RTC
CONFIG_SYS_RTC_DS1337_NOOSC - Turn off the OSC output for DS1337
CONFIG_SYS_RV3029_TCR - enable trickle charger on
RV3029 RTC.
Note that if the RTC uses I2C, then the I2C interface
must also be configured. See I2C Support, below.
- GPIO Support:
CONFIG_PCA953X - use NXP's PCA953X series I2C GPIO
The CONFIG_SYS_I2C_PCA953X_WIDTH option specifies a list of
chip-ngpio pairs that tell the PCA953X driver the number of
pins supported by a particular chip.
Note that if the GPIO device uses I2C, then the I2C interface
must also be configured. See I2C Support, below.
- I/O tracing:
When CONFIG_IO_TRACE is selected, U-Boot intercepts all I/O
accesses and can checksum them or write a list of them out
to memory. See the 'iotrace' command for details. This is
useful for testing device drivers since it can confirm that
the driver behaves the same way before and after a code
change. Currently this is supported on sandbox and arm. To
add support for your architecture, add '#include <iotrace.h>'
to the bottom of arch/<arch>/include/asm/io.h and test.
Example output from the 'iotrace stats' command is below.
Note that if the trace buffer is exhausted, the checksum will
still continue to operate.
iotrace is enabled
Start: 10000000 (buffer start address)
Size: 00010000 (buffer size)
Offset: 00000120 (current buffer offset)
Output: 10000120 (start + offset)
Count: 00000018 (number of trace records)
CRC32: 9526fb66 (CRC32 of all trace records)
- Timestamp Support:
When CONFIG_TIMESTAMP is selected, the timestamp
(date and time) of an image is printed by image
commands like bootm or iminfo. This option is
automatically enabled when you select CONFIG_CMD_DATE .
- Partition Labels (disklabels) Supported:
Zero or more of the following:
CONFIG_MAC_PARTITION Apple's MacOS partition table.
CONFIG_DOS_PARTITION MS Dos partition table, traditional on the
Intel architecture, USB sticks, etc.
CONFIG_ISO_PARTITION ISO partition table, used on CDROM etc.
CONFIG_EFI_PARTITION GPT partition table, common when EFI is the
bootloader. Note 2TB partition limit; see
CONFIG_MTD_PARTITIONS Memory Technology Device partition table.
If IDE or SCSI support is enabled (CONFIG_CMD_IDE or
CONFIG_SCSI) you must configure support for at
least one non-MTD partition type as well.
- IDE Reset method:
CONFIG_IDE_RESET_ROUTINE - this is defined in several
board configurations files but used nowhere!
CONFIG_IDE_RESET - is this is defined, IDE Reset will
be performed by calling the function
ide_set_reset(int reset)
which has to be defined in a board specific file
- ATAPI Support:
Set this to enable ATAPI support.
- LBA48 Support
Set this to enable support for disks larger than 137GB
Also look at CONFIG_SYS_64BIT_LBA.
Whithout these , LBA48 support uses 32bit variables and will 'only'
support disks up to 2.1TB.
When enabled, makes the IDE subsystem use 64bit sector addresses.
Default is 32bit.
- SCSI Support:
At the moment only there is only support for the
SYM53C8XX SCSI controller; define
CONFIG_SCSI_SYM53C8XX to enable it.
CONFIG_SYS_SCSI_MAX_LUN] can be adjusted to define the
maximum numbers of LUNs, SCSI ID's and target
CONFIG_SYS_SCSI_SYM53C8XX_CCF to fix clock timing (80Mhz)
The environment variable 'scsidevs' is set to the number of
SCSI devices found during the last scan.
- NETWORK Support (PCI):
Support for Intel 8254x/8257x gigabit chips.
Utility code for direct access to the SPI bus on Intel 8257x.
This does not do anything useful unless you set at least one
Allow generic access to the SPI bus on the Intel 8257x, for
example with the "sspi" command.
Management command for E1000 devices. When used on devices
with SPI support you can reprogram the EEPROM from U-Boot.
Support for Intel 82557/82559/82559ER chips.
write routine for first time initialisation.
Support for Digital 2114x chips.
Optional CONFIG_TULIP_SELECT_MEDIA for board specific
modem chip initialisation (KS8761/QS6611).
Support for National dp83815 chips.
Support for National dp8382[01] gigabit chips.
- NETWORK Support (other):
Support for AT91RM9200 EMAC.
Define this to use reduced MII inteface
If this defined, the driver is quiet.
The driver doen't show link status messages.
Support for the Calxeda XGMAC device
Support for SMSC's LAN91C96 chips.
Define this to enable 32 bit addressing
Support for SMSC's LAN91C111 chip
Define this to hold the physical address
of the device (I/O space)
Define this if data bus is 32 bits
Define this to use i/o functions instead of macros
(some hardware wont work with macros)
Support for davinci emac
Define this if you have more then 3 PHYs.
Support for Faraday's FTGMAC100 Gigabit SoC Ethernet
Define this to use GE link update with gigabit PHY.
Define this if FTGMAC100 is connected to gigabit PHY.
If your system has 10/100 PHY only, it might not occur
wrong behavior. Because PHY usually return timeout or
useless data when polling gigabit status and gigabit
control registers. This behavior won't affect the
correctnessof 10/100 link speed update.
Support for SMSC's LAN911x and LAN921x chips
Define this to hold the physical address
of the device (I/O space)
Define this if data bus is 32 bits
Define this if data bus is 16 bits. If your processor
automatically converts one 32 bit word to two 16 bit
words you may also try CONFIG_SMC911X_32_BIT.
Support for Renesas on-chip Ethernet controller
Define the number of ports to be used
Define the ETH PHY's address
If this option is set, the driver enables cache flush.
- PWM Support:
Support for PWM module on the imx6.
- TPM Support:
Support TPM devices.
Support for Infineon i2c bus TPM devices. Only one device
per system is supported at this time.
Define the burst count bytes upper limit
Support for STMicroelectronics TPM devices. Requires DM_TPM support.
Support for STMicroelectronics ST33ZP24 I2C devices.
Requires TPM_ST33ZP24 and I2C.
Support for STMicroelectronics ST33ZP24 SPI devices.
Requires TPM_ST33ZP24 and SPI.
Support for Atmel TWI TPM device. Requires I2C support.
Support for generic parallel port TPM devices. Only one device
per system is supported at this time.
Base address where the generic TPM device is mapped
to. Contemporary x86 systems usually map it at
Add tpm monitor functions.
provides monitor access to authorized functions.
Define this to enable the TPM support library which provides
functional interfaces to some TPM commands.
Requires support for a TPM device.
Define this to enable authorized functions in the TPM library.
- USB Support:
At the moment only the UHCI host controller is
supported (PIP405, MIP405, MPC5200); define
CONFIG_USB_UHCI to enable it.
define CONFIG_USB_KEYBOARD to enable the USB Keyboard
and define CONFIG_USB_STORAGE to enable the USB
storage devices.
Supported are USB Keyboards and USB Floppy drives
MPC5200 USB requires additional defines:
for 528 MHz Clock: 0x0001bbbb
for USB on PSC3
for differential drivers: 0x00001000
for single ended drivers: 0x00005000
for differential drivers on PSC3: 0x00000100
for single ended drivers on PSC3: 0x00004100
May be defined to allow interrupt polling
instead of using asynchronous interrupts
CONFIG_USB_EHCI_TXFIFO_THRESH enables setting of the
txfilltuning field in the EHCI controller on reset.
CONFIG_USB_DWC2_REG_ADDR the physical CPU address of the DWC2
HW module registers.
- USB Device:
Define the below if you wish to use the USB console.
Once firmware is rebuilt from a serial console issue the
command "setenv stdin usbtty; setenv stdout usbtty" and
attach your USB cable. The Unix command "dmesg" should print
it has found a new device. The environment variable usbtty
can be set to gserial or cdc_acm to enable your device to
appear to a USB host as a Linux gserial device or a
Common Device Class Abstract Control Model serial device.
If you select usbtty = gserial you should be able to enumerate
a Linux host by
# modprobe usbserial vendor=0xVendorID product=0xProductID
else if using cdc_acm, simply setting the environment
variable usbtty to be cdc_acm should suffice. The following
might be defined in YourBoardName.h
Define this to build a UDC device
Define this to have a tty type of device available to
talk to the UDC device
Define this to enable the high speed support for usb
device and usbtty. If this feature is enabled, a routine
int is_usbd_high_speed(void)
also needs to be defined by the driver to dynamically poll
whether the enumeration has succeded at high speed or full
Define this if you want stdin, stdout &/or stderr to
be set to usbtty.
Derive USB clock from external clock "blah"
If you have a USB-IF assigned VendorID then you may wish to
define your own vendor specific values either in BoardName.h
or directly in usbd_vendor_info.h. If you don't define
should pretend to be a Linux device to it's target host.
Define this string as the name of your company for
Define this string as the name of your product
- CONFIG_USBD_PRODUCT_NAME "acme usb device"
Define this as your assigned Vendor ID from the USB
Implementors Forum. This *must* be a genuine Vendor ID
to avoid polluting the USB namespace.
Define this as the unique Product ID
for your device
- ULPI Layer Support:
The ULPI (UTMI Low Pin (count) Interface) PHYs are supported via
the generic ULPI layer. The generic layer accesses the ULPI PHY
via the platform viewport, so you need both the genric layer and
the viewport enabled. Currently only Chipidea/ARC based
viewport is supported.
To enable the ULPI layer support, define CONFIG_USB_ULPI and
CONFIG_USB_ULPI_VIEWPORT in your board configuration file.
If your ULPI phy needs a different reference clock than the
standard 24 MHz then you have to define CONFIG_ULPI_REF_CLK to
the appropriate value in Hz.
- MMC Support:
The MMC controller on the Intel PXA is supported. To
enable this define CONFIG_MMC. The MMC can be
accessed from the boot prompt by mapping the device
to physical memory similar to flash. Command line is
enabled with CONFIG_CMD_MMC. The MMC driver also works with
the FAT fs. This is enabled with CONFIG_CMD_FAT.
Support for Renesas on-chip MMCIF controller
Define the base address of MMCIF registers
Define the clock frequency for MMCIF
Enable some additional features of the eMMC boot partitions.
Enable the commands for reading, writing and programming the
key for the Replay Protection Memory Block partition in eMMC.
- USB Device Firmware Update (DFU) class support:
This enables the USB portion of the DFU USB class
This enables the command "dfu" which is used to have
U-Boot create a DFU class device via USB. This command
requires that the "dfu_alt_info" environment variable be
set and define the alt settings to expose to the host.
This enables support for exposing (e)MMC devices via DFU.
This enables support for exposing NAND devices via DFU.
This enables support for exposing RAM via DFU.
Note: DFU spec refer to non-volatile memory usage, but
allow usages beyond the scope of spec - here RAM usage,
one that would help mostly the developer.
Dfu transfer uses a buffer before writing data to the
raw storage device. Make the size (in bytes) of this buffer
configurable. The size of this buffer is also configurable
through the "dfu_bufsiz" environment variable.
When updating files rather than the raw storage device,
we use a static buffer to copy the file into and then write
the buffer once we've been given the whole file. Define
this to the maximum filesize (in bytes) for the buffer.
Default is 4 MiB if undefined.
Poll timeout [ms], is the timeout a device can send to the
host. The host must wait for this timeout before sending
a subsequent DFU_GET_STATUS request to the device.
Poll timeout [ms], which the device sends to the host when
entering dfuMANIFEST state. Host waits this timeout, before
sending again an USB request to the device.
- USB Device Android Fastboot support:
This enables the USB part of the fastboot gadget
This enables the command "fastboot" which enables the Android
fastboot mode for the platform's USB device. Fastboot is a USB
protocol for downloading images, flashing and device control
used on Android devices.
See doc/ for more information.
This enables support for booting images which use the Android
image format header.
The fastboot protocol requires a large memory buffer for
downloads. Define this to the starting RAM address to use for
downloaded images.
The fastboot protocol requires a large memory buffer for
downloads. This buffer should be as large as possible for a
platform. Define this to the size available RAM for fastboot.
The fastboot protocol includes a "flash" command for writing
the downloaded image to a non-volatile storage device. Define
this to enable the "fastboot flash" command.
The fastboot "flash" command requires additional information
regarding the non-volatile storage device. Define this to
the eMMC device that fastboot should use to store the image.
The fastboot "flash" command supports writing the downloaded
image to the Protective MBR and the Primary GUID Partition
Table. (Additionally, this downloaded image is post-processed
to generate and write the Backup GUID Partition Table.)
This occurs when the specified "partition name" on the
"fastboot flash" command line matches this value.
The default is "gpt" if undefined.
The fastboot "flash" command supports writing the downloaded
image to DOS MBR.
This occurs when the "partition name" specified on the
"fastboot flash" command line matches this value.
If not defined the default value "mbr" is used.
- Journaling Flash filesystem support:
Define these for a default partition on a NAND device
Define these for a default partition on a NOR device
- FAT(File Allocation Table) filesystem write function support:
Define this to enable support for saving memory data as a
file in FAT formatted partition.
This will also enable the command "fatwrite" enabling the
user to write files to FAT.
- CBFS (Coreboot Filesystem) support:
Define this to enable support for reading from a Coreboot
filesystem. Available commands are cbfsinit, cbfsinfo, cbfsls
and cbfsload.
- FAT(File Allocation Table) filesystem cluster size:
Define the max cluster size for fat operations else
a default value of 65536 will be defined.
- Keyboard Support:
See Kconfig help for available keyboard drivers.
Define this to enable a custom keyboard support.
This simply calls drv_keyboard_init() which must be
defined in your board-specific files. This option is deprecated
and is only used by novena. For new boards, use driver model
- Video support:
Enable the Freescale DIU video driver. Reference boards for
SOCs that have a DIU should define this macro to enable DIU
support, and should also define these other macros:
The DIU driver will look for the 'video-mode' environment
variable, and if defined, enable the DIU as a console during
boot. See the documentation file doc/ for a
description of this variable.
Define this to enable LCD support (for output to LCD
display); also select one of the supported displays
by defining one of these:
HITACHI TX09D70VM1CCA, 3.5", 240x320.
NEC NL6448AC33-18. Active, color, single scan.
NEC NL6448BC20-08. 6.5", 640x480.
Active, color, single scan.
NEC NL6448BC33-54. 10.4", 640x480.
Active, color, single scan.
Sharp 320x240. Active, color, single scan.
It isn't 16x9, and I am not sure what it is.
Sharp LQ64D341 display, 640x480.
Active, color, single scan.
HLD1045 display, 640x480.
Active, color, single scan.
Optrex CBL50840-2 NF-FW 99 22 M5
Hitachi LMG6912RPFC-00T
Hitachi SP14Q002
320x240. Black & white.
Normally display is black on white background; define
CONFIG_SYS_WHITE_ON_BLACK to get it inverted.
Normally the LCD is page-aligned (typically 4KB). If this is
defined then the LCD will be aligned to this value instead.
For ARM it is sometimes useful to use MMU_SECTION_SIZE
here, since it is cheaper to change data cache settings on
a per-section basis.
Sometimes, for example if the display is mounted in portrait
mode or even if it's mounted landscape but rotated by 180degree,
we need to rotate our content of the display relative to the
framebuffer, so that user can read the messages which are
printed out.
Once CONFIG_LCD_ROTATION is defined, the lcd_console will be
initialized with a given rotation from "vl_rot" out of
"vidinfo_t" which is provided by the board specific code.
The value for vl_rot is coded as following (matching to
fbcon=rotate:<n> linux-kernel commandline):
0 = no rotation respectively 0 degree
1 = 90 degree rotation
2 = 180 degree rotation
3 = 270 degree rotation
If CONFIG_LCD_ROTATION is not defined, the console will be
initialized with 0degree rotation.
Support drawing of RLE8-compressed bitmaps on the LCD.
Enables an 'i2c edid' command which can read EDID
information over I2C from an attached LCD display.
- Splash Screen Support: CONFIG_SPLASH_SCREEN
If this option is set, the environment is checked for
a variable "splashimage". If found, the usual display
of logo, copyright and system information on the LCD
is suppressed and the BMP image at the address
specified in "splashimage" is loaded instead. The
console is redirected to the "nulldev", too. This
allows for a "silent" boot where a splash screen is
loaded very quickly after power-on.
If this option is set, then U-Boot will prevent the environment
variable "splashimage" from being set to a problematic address
(see doc/README.displaying-bmps).
This option is useful for targets where, due to alignment
restrictions, an improperly aligned BMP image will cause a data
abort. If you think you will not have problems with unaligned
accesses (for example because your toolchain prevents them)
there is no need to set this option.
If this option is set the splash image can be freely positioned
on the screen. Environment variable "splashpos" specifies the
position as "x,y". If a positive number is given it is used as
number of pixel from left/top. If a negative number is given it
is used as number of pixel from right/bottom. You can also
specify 'm' for centering the image.
setenv splashpos m,m
=> image at center of screen
setenv splashpos 30,20
=> image at x = 30 and y = 20
setenv splashpos -10,m
=> vertically centered image
at x = dspWidth - bmpWidth - 9
- Gzip compressed BMP image support: CONFIG_VIDEO_BMP_GZIP
If this option is set, additionally to standard BMP
images, gzipped BMP images can be displayed via the
splashscreen support or the bmp command.
- Run length encoded BMP image (RLE8) support: CONFIG_VIDEO_BMP_RLE8
If this option is set, 8-bit RLE compressed BMP images
can be displayed via the splashscreen support or the
bmp command.
- Compression support:
Enabled by default to support gzip compressed images.
If this option is set, support for bzip2 compressed
images is included. If not, only uncompressed and gzip
compressed images are supported.
NOTE: the bzip2 algorithm requires a lot of RAM, so
the malloc area (as defined by CONFIG_SYS_MALLOC_LEN) should
be at least 4MB.
If this option is set, support for lzma compressed
images is included.
Note: The LZMA algorithm adds between 2 and 4KB of code and it
requires an amount of dynamic memory that is given by the
(1846 + 768 << (lc + lp)) * sizeof(uint16)
Where lc and lp stand for, respectively, Literal context bits
and Literal pos bits.
This value is upper-bounded by 14MB in the worst case. Anyway,
for a ~4MB large kernel image, we have lc=3 and lp=0 for a
total amount of (1846 + 768 << (3 + 0)) * 2 = ~41KB... that is
a very small buffer.
Use the lzmainfo tool to determinate the lc and lp values and
then calculate the amount of needed dynamic memory (ensuring
the appropriate CONFIG_SYS_MALLOC_LEN value).
If this option is set, support for LZO compressed images
is included.
- MII/PHY support:
The address of PHY on MII bus.
The clock frequency of the MII bus
If this option is set, support for speed/duplex
detection of gigabit PHY is included.
Some PHY like Intel LXT971A need extra delay after
reset before any MII register access is possible.
For such PHY, set this option to the usec delay
required. (minimum 300usec for LXT971A)
Some PHY like Intel LXT971A need extra delay after
command issued before MII status register can be read
- IP address:
Define a default value for the IP address to use for
the default Ethernet interface, in case this is not
determined through e.g. bootp.
(Environment variable "ipaddr")
- Server IP address:
Defines a default value for the IP address of a TFTP
server to contact when using the "tftboot" command.
(Environment variable "serverip")
Keeps the server's MAC address, in the env 'serveraddr'
for passing to bootargs (like Linux's netconsole option)
- Gateway IP address:
Defines a default value for the IP address of the
default router where packets to other networks are
sent to.
(Environment variable "gatewayip")
- Subnet mask:
Defines a default value for the subnet mask (or
routing prefix) which is used to determine if an IP
address belongs to the local subnet or needs to be
forwarded through a router.
(Environment variable "netmask")
- Multicast TFTP Mode:
Defines whether you want to support multicast TFTP as per
rfc-2090; for example to work with atftp. Lets lots of targets
tftp down the same boot image concurrently. Note: the Ethernet
driver in use must provide a function: mcast() to join/leave a
multicast group.
- BOOTP Recovery Mode:
If you have many targets in a network that try to
boot using BOOTP, you may want to avoid that all
systems send out BOOTP requests at precisely the same
moment (which would happen for instance at recovery
from a power failure, when all systems will try to
boot, thus flooding the BOOTP server. Defining
CONFIG_BOOTP_RANDOM_DELAY causes a random delay to be
inserted before sending out BOOTP requests. The
following delays are inserted then:
1st BOOTP request: delay 0 ... 1 sec
2nd BOOTP request: delay 0 ... 2 sec
3rd BOOTP request: delay 0 ... 4 sec
4th and following
BOOTP requests: delay 0 ... 8 sec
BOOTP packets are uniquely identified using a 32-bit ID. The
server will copy the ID from client requests to responses and
U-Boot will use this to determine if it is the destination of
an incoming response. Some servers will check that addresses
aren't in use before handing them out (usually using an ARP
ping) and therefore take up to a few hundred milliseconds to
respond. Network congestion may also influence the time it
takes for a response to make it back to the client. If that
time is too long, U-Boot will retransmit requests. In order
to allow earlier responses to still be accepted after these
retransmissions, U-Boot's BOOTP client keeps a small cache of
IDs. The CONFIG_BOOTP_ID_CACHE_SIZE controls the size of this
cache. The default is to keep IDs for up to four outstanding
requests. Increasing this will allow U-Boot to accept offers
from a BOOTP client in networks with unusually high latency.
- DHCP Advanced Options:
You can fine tune the DHCP functionality by defining
CONFIG_BOOTP_* symbols:
CONFIG_BOOTP_SERVERIP - TFTP server will be the serverip
environment variable, not the BOOTP server.
CONFIG_BOOTP_MAY_FAIL - If the DHCP server is not found
after the configured retry count, the call will fail
instead of starting over. This can be used to fail over
to Link-local IP address configuration if the DHCP server
is not available.
CONFIG_BOOTP_DNS2 - If a DHCP client requests the DNS
serverip from a DHCP server, it is possible that more
than one DNS serverip is offered to the client.
If CONFIG_BOOTP_DNS2 is enabled, the secondary DNS
serverip will be stored in the additional environment
variable "dnsip2". The first DNS serverip is always
stored in the variable "dnsip", when CONFIG_BOOTP_DNS
is defined.
CONFIG_BOOTP_SEND_HOSTNAME - Some DHCP servers are capable
to do a dynamic update of a DNS server. To do this, they
need the hostname of the DHCP requester.
If CONFIG_BOOTP_SEND_HOSTNAME is defined, the content
of the "hostname" environment variable is passed as
option 12 to the DHCP server.
A 32bit value in microseconds for a delay between
receiving a "DHCP Offer" and sending the "DHCP Request".
This fixes a problem with certain DHCP servers that don't
respond 100% of the time to a "DHCP request". E.g. On an
AT91RM9200 processor running at 180MHz, this delay needed
to be *at least* 15,000 usec before a Windows Server 2003
DHCP server would reply 100% of the time. I recommend at
least 50,000 usec to be safe. The alternative is to hope
that one of the retries will be successful but note that
the DHCP timeout and retry process takes a longer than
this delay.
- Link-local IP address negotiation:
Negotiate with other link-local clients on the local network
for an address that doesn't require explicit configuration.
This is especially useful if a DHCP server cannot be guaranteed
to exist in all environments that the device must operate.
See doc/ for more information.
- CDP Options:
The device id used in CDP trigger frames.
A two character string which is prefixed to the MAC address
of the device.
A printf format string which contains the ascii name of
the port. Normally is set to "eth%d" which sets
eth0 for the first Ethernet, eth1 for the second etc.
A 32bit integer which indicates the device capabilities;
0x00000010 for a normal host which does not forwards.
An ascii string containing the version of the software.
An ascii string containing the name of the platform.
A 32bit integer sent on the trigger.
A 16bit integer containing the power consumption of the
device in .1 of milliwatts.
A byte containing the id of the VLAN.
Several configurations allow to display the current
status using a LED. For instance, the LED will blink
fast while running U-Boot code, stop blinking as
soon as a reply to a BOOTP request was received, and
start blinking slow once the Linux kernel is running
(supported by a status LED driver in the Linux
kernel). Defining CONFIG_LED_STATUS enables this
feature in U-Boot.
Additional options:
The status LED can be connected to a GPIO pin.
In such cases, the gpio_led driver can be used as a
status LED backend implementation. Define CONFIG_LED_STATUS_GPIO
to include the gpio_led driver in the U-Boot binary.
Some GPIO connected LEDs may have inverted polarity in which
case the GPIO high value corresponds to LED off state and
GPIO low value corresponds to LED on state.
In such cases CONFIG_GPIO_LED_INVERTED_TABLE may be defined
with a list of GPIO LEDs that have inverted polarity.
Defining CONFIG_CAN_DRIVER enables CAN driver support
on those systems that support this (optional)
feature, like the TQM8xxL modules.
- I2C Support: CONFIG_SYS_I2C
This enable the NEW i2c subsystem, and will allow you to use
i2c commands at the u-boot command line (as long as you set
CONFIG_CMD_I2C in CONFIG_COMMANDS) and communicate with i2c
based realtime clock chips or other i2c devices. See
common/cmd_i2c.c for a description of the command line
ported i2c driver to the new framework:
- drivers/i2c/soft_i2c.c:
- activate first bus with CONFIG_SYS_I2C_SOFT define
for defining speed and slave address
- activate second bus with I2C_SOFT_DECLARATIONS2 define
for defining speed and slave address
- activate third bus with I2C_SOFT_DECLARATIONS3 define
for defining speed and slave address
- activate fourth bus with I2C_SOFT_DECLARATIONS4 define
for defining speed and slave address
- drivers/i2c/fsl_i2c.c:
- activate i2c driver with CONFIG_SYS_I2C_FSL
define CONFIG_SYS_FSL_I2C_OFFSET for setting the register
offset CONFIG_SYS_FSL_I2C_SPEED for the i2c speed and
CONFIG_SYS_FSL_I2C_SLAVE for the slave addr of the first
- If your board supports a second fsl i2c bus, define
CONFIG_SYS_FSL_I2C2_OFFSET for the register offset
CONFIG_SYS_FSL_I2C2_SPEED for the speed and
CONFIG_SYS_FSL_I2C2_SLAVE for the slave address of the
second bus.
- drivers/i2c/tegra_i2c.c:
- activate this driver with CONFIG_SYS_I2C_TEGRA
- This driver adds 4 i2c buses with a fix speed from
100000 and the slave addr 0!
- drivers/i2c/ppc4xx_i2c.c
- activate this driver with CONFIG_SYS_I2C_PPC4XX
- CONFIG_SYS_I2C_PPC4XX_CH0 activate hardware channel 0
- CONFIG_SYS_I2C_PPC4XX_CH1 activate hardware channel 1
- drivers/i2c/i2c_mxc.c
- activate this driver with CONFIG_SYS_I2C_MXC
- enable bus 1 with CONFIG_SYS_I2C_MXC_I2C1
- enable bus 2 with CONFIG_SYS_I2C_MXC_I2C2
- enable bus 3 with CONFIG_SYS_I2C_MXC_I2C3
- enable bus 4 with CONFIG_SYS_I2C_MXC_I2C4
- define speed for bus 1 with CONFIG_SYS_MXC_I2C1_SPEED
- define slave for bus 1 with CONFIG_SYS_MXC_I2C1_SLAVE
- define speed for bus 2 with CONFIG_SYS_MXC_I2C2_SPEED
- define slave for bus 2 with CONFIG_SYS_MXC_I2C2_SLAVE
- define speed for bus 3 with CONFIG_SYS_MXC_I2C3_SPEED
- define slave for bus 3 with CONFIG_SYS_MXC_I2C3_SLAVE
- define speed for bus 4 with CONFIG_SYS_MXC_I2C4_SPEED
- define slave for bus 4 with CONFIG_SYS_MXC_I2C4_SLAVE
If those defines are not set, default value is 100000
for speed, and 0 for slave.
- drivers/i2c/rcar_i2c.c:
- activate this driver with CONFIG_SYS_I2C_RCAR
- This driver adds 4 i2c buses
- CONFIG_SYS_RCAR_I2C0_BASE for setting the register channel 0
- CONFIG_SYS_RCAR_I2C0_SPEED for for the speed channel 0
- CONFIG_SYS_RCAR_I2C1_BASE for setting the register channel 1
- CONFIG_SYS_RCAR_I2C1_SPEED for for the speed channel 1
- CONFIG_SYS_RCAR_I2C2_BASE for setting the register channel 2
- CONFIG_SYS_RCAR_I2C2_SPEED for for the speed channel 2
- CONFIG_SYS_RCAR_I2C3_BASE for setting the register channel 3
- CONFIG_SYS_RCAR_I2C3_SPEED for for the speed channel 3
- CONFIF_SYS_RCAR_I2C_NUM_CONTROLLERS for number of i2c buses
- drivers/i2c/sh_i2c.c:
- activate this driver with CONFIG_SYS_I2C_SH
- This driver adds from 2 to 5 i2c buses
- CONFIG_SYS_I2C_SH_BASE0 for setting the register channel 0
- CONFIG_SYS_I2C_SH_SPEED0 for for the speed channel 0
- CONFIG_SYS_I2C_SH_BASE1 for setting the register channel 1
- CONFIG_SYS_I2C_SH_SPEED1 for for the speed channel 1
- CONFIG_SYS_I2C_SH_BASE2 for setting the register channel 2
- CONFIG_SYS_I2C_SH_SPEED2 for for the speed channel 2
- CONFIG_SYS_I2C_SH_BASE3 for setting the register channel 3
- CONFIG_SYS_I2C_SH_SPEED3 for for the speed channel 3
- CONFIG_SYS_I2C_SH_BASE4 for setting the register channel 4
- CONFIG_SYS_I2C_SH_SPEED4 for for the speed channel 4
- CONFIG_SYS_I2C_SH_NUM_CONTROLLERS for number of i2c buses
- drivers/i2c/omap24xx_i2c.c
- activate this driver with CONFIG_SYS_I2C_OMAP24XX
- CONFIG_SYS_OMAP24_I2C_SPEED speed channel 0
- CONFIG_SYS_OMAP24_I2C_SLAVE slave addr channel 0
- CONFIG_SYS_OMAP24_I2C_SPEED1 speed channel 1
- CONFIG_SYS_OMAP24_I2C_SLAVE1 slave addr channel 1
- CONFIG_SYS_OMAP24_I2C_SPEED2 speed channel 2
- CONFIG_SYS_OMAP24_I2C_SLAVE2 slave addr channel 2
- CONFIG_SYS_OMAP24_I2C_SPEED3 speed channel 3
- CONFIG_SYS_OMAP24_I2C_SLAVE3 slave addr channel 3
- CONFIG_SYS_OMAP24_I2C_SPEED4 speed channel 4
- CONFIG_SYS_OMAP24_I2C_SLAVE4 slave addr channel 4
- drivers/i2c/zynq_i2c.c
- activate this driver with CONFIG_SYS_I2C_ZYNQ
- set CONFIG_SYS_I2C_ZYNQ_SPEED for speed setting
- set CONFIG_SYS_I2C_ZYNQ_SLAVE for slave addr
- drivers/i2c/s3c24x0_i2c.c:
- activate this driver with CONFIG_SYS_I2C_S3C24X0
- This driver adds i2c buses (11 for Exynos5250, Exynos5420
9 i2c buses for Exynos4 and 1 for S3C24X0 SoCs from Samsung)
with a fix speed from 100000 and the slave addr 0!
- drivers/i2c/ihs_i2c.c
- activate this driver with CONFIG_SYS_I2C_IHS
- CONFIG_SYS_I2C_IHS_CH0 activate hardware channel 0
- CONFIG_SYS_I2C_IHS_SPEED_0 speed channel 0
- CONFIG_SYS_I2C_IHS_SLAVE_0 slave addr channel 0
- CONFIG_SYS_I2C_IHS_CH1 activate hardware channel 1
- CONFIG_SYS_I2C_IHS_SPEED_1 speed channel 1
- CONFIG_SYS_I2C_IHS_SLAVE_1 slave addr channel 1
- CONFIG_SYS_I2C_IHS_CH2 activate hardware channel 2
- CONFIG_SYS_I2C_IHS_SPEED_2 speed channel 2
- CONFIG_SYS_I2C_IHS_SLAVE_2 slave addr channel 2
- CONFIG_SYS_I2C_IHS_CH3 activate hardware channel 3
- CONFIG_SYS_I2C_IHS_SPEED_3 speed channel 3
- CONFIG_SYS_I2C_IHS_SLAVE_3 slave addr channel 3
- activate dual channel with CONFIG_SYS_I2C_IHS_DUAL
- CONFIG_SYS_I2C_IHS_SPEED_0_1 speed channel 0_1
- CONFIG_SYS_I2C_IHS_SLAVE_0_1 slave addr channel 0_1
- CONFIG_SYS_I2C_IHS_SPEED_1_1 speed channel 1_1
- CONFIG_SYS_I2C_IHS_SLAVE_1_1 slave addr channel 1_1
- CONFIG_SYS_I2C_IHS_SPEED_2_1 speed channel 2_1
- CONFIG_SYS_I2C_IHS_SLAVE_2_1 slave addr channel 2_1
- CONFIG_SYS_I2C_IHS_SPEED_3_1 speed channel 3_1
- CONFIG_SYS_I2C_IHS_SLAVE_3_1 slave addr channel 3_1
additional defines:
Hold the number of i2c buses you want to use.
define this, if you don't use i2c muxes on your hardware.
if CONFIG_SYS_I2C_MAX_HOPS is not defined or == 0 you can
omit this define.
define how many muxes are maximal consecutively connected
on one i2c bus. If you not use i2c muxes, omit this
hold a list of buses you want to use, only used if
CONFIG_SYS_I2C_DIRECT_BUS is not defined, for example
a board with CONFIG_SYS_I2C_MAX_HOPS = 1 and
{0, {{I2C_MUX_PCA9547, 0x70, 1}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 2}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 3}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 4}}}, \
{0, {{I2C_MUX_PCA9547, 0x70, 5}}}, \
{1, {I2C_NULL_HOP}}, \
{1, {{I2C_MUX_PCA9544, 0x72, 1}}}, \
{1, {{I2C_MUX_PCA9544, 0x72, 2}}}, \
which defines
bus 0 on adapter 0 without a mux
bus 1 on adapter 0 with a PCA9547 on address 0x70 port 1
bus 2 on adapter 0 with a PCA9547 on address 0x70 port 2
bus 3 on adapter 0 with a PCA9547 on address 0x70 port 3
bus 4 on adapter 0 with a PCA9547 on address 0x70 port 4
bus 5 on adapter 0 with a PCA9547 on address 0x70 port 5
bus 6 on adapter 1 without a mux
bus 7 on adapter 1 with a PCA9544 on address 0x72 port 1
bus 8 on adapter 1 with a PCA9544 on address 0x72 port 2
If you do not have i2c muxes on your board, omit this define.
- Legacy I2C Support: CONFIG_HARD_I2C
NOTE: It is intended to move drivers to CONFIG_SYS_I2C which
provides the following compelling advantages:
- more than one i2c adapter is usable
- approved multibus support
- better i2c mux support
** Please consider updating your I2C driver now. **
These enable legacy I2C serial bus commands. Defining
CONFIG_HARD_I2C will include the appropriate I2C driver
for the selected CPU.
This will allow you to use i2c commands at the u-boot
command line (as long as you set CONFIG_CMD_I2C in
CONFIG_COMMANDS) and communicate with i2c based realtime
clock chips. See common/cmd_i2c.c for a description of the
command line interface.
CONFIG_HARD_I2C selects a hardware I2C controller.
There are several other quantities that must also be
defined when you define CONFIG_HARD_I2C.
In both cases you will need to define CONFIG_SYS_I2C_SPEED
to be the frequency (in Hz) at which you wish your i2c bus
to run and CONFIG_SYS_I2C_SLAVE to be the address of this node (ie
the CPU's i2c node address).
Now, the u-boot i2c code for the mpc8xx
(arch/powerpc/cpu/mpc8xx/i2c.c) sets the CPU up as a master node
and so its address should therefore be cleared to 0 (See,
eg, MPC823e User's Manual p.16-473). So, set
When a board is reset during an i2c bus transfer
chips might think that the current transfer is still
in progress. Reset the slave devices by sending start
commands until the slave device responds.
That's all that's required for CONFIG_HARD_I2C.
If you use the software i2c interface (CONFIG_SYS_I2C_SOFT)
then the following macros need to be defined (examples are
from include/configs/lwmon.h):
(Optional). Any commands necessary to enable the I2C
controller or configure ports.
eg: #define I2C_INIT (immr->im_cpm.cp_pbdir |= PB_SCL)
(Only for MPC8260 CPU). The I/O port to use (the code
assumes both bits are on the same port). Valid values
are 0..3 for ports A..D.
The code necessary to make the I2C data line active
(driven). If the data line is open collector, this
define can be null.
eg: #define I2C_ACTIVE (immr->im_cpm.cp_pbdir |= PB_SDA)
The code necessary to make the I2C data line tri-stated
(inactive). If the data line is open collector, this
define can be null.
eg: #define I2C_TRISTATE (immr->im_cpm.cp_pbdir &= ~PB_SDA)
Code that returns true if the I2C data line is high,
false if it is low.
eg: #define I2C_READ ((immr->im_cpm.cp_pbdat & PB_SDA) != 0)
If <bit> is true, sets the I2C data line high. If it
is false, it clears it (low).
eg: #define I2C_SDA(bit) \
if(bit) immr->im_cpm.cp_pbdat |= PB_SDA; \
else immr->im_cpm.cp_pbdat &= ~PB_SDA
If <bit> is true, sets the I2C clock line high. If it
is false, it clears it (low).
eg: #define I2C_SCL(bit) \
if(bit) immr->im_cpm.cp_pbdat |= PB_SCL; \
else immr->im_cpm.cp_pbdat &= ~PB_SCL
This delay is invoked four times per clock cycle so this
controls the rate of data transfer. The data rate thus
is 1 / (I2C_DELAY * 4). Often defined to be something
#define I2C_DELAY udelay(2)
If your arch supports the generic GPIO framework (asm/gpio.h),
then you may alternatively define the two GPIOs that are to be
used as SCL / SDA. Any of the previous I2C_xxx macros will
have GPIO-based defaults assigned to them as appropriate.
You should define these to the GPIO value as given directly to
the generic GPIO functions.
When a board is reset during an i2c bus transfer
chips might think that the current transfer is still
in progress. On some boards it is possible to access
the i2c SCLK line directly, either by using the
processor pin as a GPIO or by having a second pin
connected to the bus. If this option is defined a
custom i2c_init_board() routine in boards/xxx/board.c
is run early in the boot sequence.
An alternative to CONFIG_SYS_I2C_INIT_BOARD. If this option is
defined a custom i2c_board_late_init() routine in
boards/xxx/board.c is run AFTER the operations in i2c_init()
is completed. This callpoint can be used to unreset i2c bus
using CPU i2c controller register accesses for CPUs whose i2c
controller provide such a method. It is called at the end of
i2c_init() to allow i2c_init operations to setup the i2c bus
controller on the CPU (e.g. setting bus speed & slave address).
This option enables configuration of bi_iic_fast[] flags
in u-boot bd_info structure based on u-boot environment
variable "i2cfast". (see also i2cfast)
This option allows the use of multiple I2C buses, each of which
must have a controller. At any point in time, only one bus is
active. To switch to a different bus, use the 'i2c dev' command.
Note that bus numbering is zero-based.
This option specifies a list of I2C devices that will be skipped
when the 'i2c probe' command is issued. If CONFIG_I2C_MULTI_BUS
is set, specify a list of bus-device pairs. Otherwise, specify
a 1D array of device addresses
#define CONFIG_SYS_I2C_NOPROBES {0x50,0x68}
will skip addresses 0x50 and 0x68 on a board with one I2C bus
#define CONFIG_SYS_I2C_NOPROBES {{0,0x50},{0,0x68},{1,0x54}}
will skip addresses 0x50 and 0x68 on bus 0 and address 0x54 on bus 1
If defined, then this indicates the I2C bus number for DDR SPD.
If not defined, then U-Boot assumes that SPD is on I2C bus 0.
If defined, then this indicates the I2C bus number for the RTC.
If not defined, then U-Boot assumes that RTC is on I2C bus 0.
If defined, then this indicates the I2C bus number for the DTT.
If not defined, then U-Boot assumes that DTT is on I2C bus 0.
If defined, specifies the I2C address of the DTT device.
If not defined, then U-Boot uses predefined value for
specified DTT device.
defining this will force the i2c_read() function in
the soft_i2c driver to perform an I2C repeated start
between writing the address pointer and reading the
data. If this define is omitted the default behaviour
of doing a stop-start sequence will be used. Most I2C
devices can use either method, but some require one or
the other.
Enables SPI driver (so far only tested with
SPI EEPROM, also an instance works with Crystal A/D and
D/As on the SACSng board)
Enables the driver for SPI controller on SuperH. Currently
only SH7757 is supported.
Enables a software (bit-bang) SPI driver rather than
using hardware support. This is a general purpose
driver that only requires three general I/O port pins
(two outputs, one input) to function. If this is
defined, the board configuration must define several
SPI configuration items (port pins to use, etc). For
an example, see include/configs/sacsng.h.
Enables a hardware SPI driver for general-purpose reads
and writes. As with CONFIG_SOFT_SPI, the board configuration
must define a list of chip-select function pointers.
Currently supported on some MPC8xxx processors. For an
example, see include/configs/mpc8349emds.h.
Enables the driver for the SPI controllers on i.MX and MXC
SoCs. Currently i.MX31/35/51 are supported.
Timeout for waiting until spi transfer completed.
default: (CONFIG_SYS_HZ/100) /* 10 ms */
Enables FPGA subsystem.
Enables support for specific chip vendors.
Enables support for FPGA family.
Specify the number of FPGA devices to support.
Enable support for fpga loadmk command
Enable support for fpga loadp command - load partial bitstream
Enable support for fpga loadbp command - load partial bitstream
(Xilinx only)
Enable printing of hash marks during FPGA configuration.
Enable checks on FPGA configuration interface busy
status by the configuration function. This option
will require a board or device specific function to
be written.
If defined, a function that provides delays in the FPGA
configuration driver.
Allow Control-C to interrupt FPGA configuration
Check for configuration errors during FPGA bitfile
loading. For example, abort during Virtex II
configuration if the INIT_B line goes low (which
indicated a CRC error).
Maximum time to wait for the INIT_B line to de-assert
after PROB_B has been de-asserted during a Virtex II
FPGA configuration sequence. The default time is 500
Maximum time to wait for BUSY to de-assert during
Virtex II FPGA configuration. The default is 5 ms.
Time to wait after FPGA configuration. The default is
200 ms.
- Configuration Management:
Some SoCs need special image types (e.g. U-Boot binary
with a special header) as build targets. By defining
CONFIG_BUILD_TARGET in the SoC / board header, this
special image will be automatically built upon calling
make / buildman.
If defined, this string will be added to the U-Boot
version information (U_BOOT_VERSION)
- Vendor Parameter Protection:
U-Boot considers the values of the environment
variables "serial#" (Board Serial Number) and
"ethaddr" (Ethernet Address) to be parameters that
are set once by the board vendor / manufacturer, and
protects these variables from casual modification by
the user. Once set, these variables are read-only,
and write or delete attempts are rejected. You can
change this behaviour:
If CONFIG_ENV_OVERWRITE is #defined in your config
file, the write protection for vendor parameters is
completely disabled. Anybody can change or delete
these parameters.
Alternatively, if you define _both_ an ethaddr in the
default env _and_ CONFIG_OVERWRITE_ETHADDR_ONCE, a default
Ethernet address is installed in the environment,
which can be changed exactly ONCE by the user. [The
serial# is unaffected by this, i. e. it remains
The same can be accomplished in a more flexible way
for any variable by configuring the type of access
to allow for those variables in the ".flags" variable
- Protected RAM:
Define this variable to enable the reservation of
"protected RAM", i. e. RAM which is not overwritten
by U-Boot. Define CONFIG_PRAM to hold the number of
kB you want to reserve for pRAM. You can overwrite
this default value by defining an environment
variable "pram" to the number of kB you want to
reserve. Note that the board info structure will
still show the full amount of RAM. If pRAM is
reserved, a new environment variable "mem" will
automatically be defined to hold the amount of
remaining RAM in a form that can be passed as boot
argument to Linux, for instance like that:
setenv bootargs ... mem=\${mem}
This way you can tell Linux not to use this memory,
either, which results in a memory region that will
not be affected by reboots.
*WARNING* If your board configuration uses automatic
detection of the RAM size, you must make sure that
this memory test is non-destructive. So far, the
following board configurations are known to be
IVMS8, IVML24, SPD8xx, TQM8xxL,
- Access to physical memory region (> 4GB)
Some basic support is provided for operations on memory not
normally accessible to U-Boot - e.g. some architectures
support access to more than 4GB of memory on 32-bit
machines using physical address extension or similar.
Define CONFIG_PHYSMEM to access this basic support, which
currently only supports clearing the memory.
- Error Recovery:
Define this variable to stop the system in case of a
fatal error, so that you have to reset it manually.
This is probably NOT a good idea for an embedded
system where you want the system to reboot
automatically as fast as possible, but it may be
useful during development since you can try to debug
the conditions that lead to the situation.
This variable defines the number of retries for
network operations like ARP, RARP, TFTP, or BOOTP
before giving up the operation. If not defined, a
default value of 5 is used.
Timeout waiting for an ARP reply in milliseconds.
Timeout in milliseconds used in NFS protocol.
If you encounter "ERROR: Cannot umount" in nfs command,
try longer timeout such as
- Command Interpreter:
Enable auto completion of commands using TAB.
This defines the secondary prompt string, which is
printed when the command interpreter needs more input
to complete a command. Usually "> ".
In the current implementation, the local variables
space and global environment variables space are
separated. Local variables are those you define by
simply typing `name=value'. To access a local
variable later on, you have write `$name' or
`${name}'; to execute the contents of a variable
directly type `$name' at the command prompt.
Global environment variables are those you use
setenv/printenv to work with. To run a command stored
in such a variable, you need to use the run command,
and you must not use the '$' sign to access them.
To store commands and special characters in a
variable, please use double quotation marks
surrounding the whole text of the variable, instead
of the backslashes before semicolons and special
- Command Line Editing and History:
Enable editing and History functions for interactive
command line input operations
- Command Line PS1/PS2 support:
Enable support for changing the command prompt string
at run-time. Only static string is supported so far.
The string is obtained from environment variables PS1
and PS2.
- Default Environment:
Define this to contain any number of null terminated
strings (variable = value pairs) that will be part of
the default environment compiled into the boot image.
For example, place something like this in your
board's config file:
"myvar1=value1\0" \
Warning: This method is based on knowledge about the
internal format how the environment is stored by the
U-Boot code. This is NOT an official, exported
interface! Although it is unlikely that this format
will change soon, there is no guarantee either.
You better know what you are doing here.
Note: overly (ab)use of the default environment is
discouraged. Make sure to check other ways to preset
the environment like the "source" command or the
boot command first.
Define this in order to add variables describing the
U-Boot build configuration to the default environment.
These will be named arch, cpu, board, vendor, and soc.
Enabling this option will cause the following to be defined:
Define this in order to add variables describing certain
run-time determined information about the hardware to the
environment. These will be named board_name, board_rev.
Normally the environment is loaded when the board is
initialised so that it is available to U-Boot. This inhibits
that so that the environment is not available until
explicitly loaded later by U-Boot code. With CONFIG_OF_CONTROL
this is instead controlled by the value of
- DataFlash Support:
Defining this option enables DataFlash features and
allows to read/write in Dataflash via the standard
commands cp, md...
- Serial Flash support
Defining this option enables SPI flash commands
'sf probe/read/write/erase/update'.
Usage requires an initial 'probe' to define the serial
flash parameters, followed by read/write/erase/update
The following defaults may be provided by the platform
to handle the common case when only a single serial
flash is present on the system.
CONFIG_SF_DEFAULT_MODE (see include/spi.h)
Define this option to include a destructive SPI flash
test ('sf test').
CONFIG_SF_DUAL_FLASH Dual flash memories
Define this option to use dual flash support where two flash
memories can be connected with a given cs line.
Currently Xilinx Zynq qspi supports these type of connections.
- SystemACE Support:
Adding this option adds support for Xilinx SystemACE
chips attached via some sort of local bus. The address
of the chip must also be defined in the
#define CONFIG_SYS_SYSTEMACE_BASE 0xf0000000
When SystemACE support is added, the "ace" device type
becomes available to the fat commands, i.e. fatls.
- TFTP Fixed UDP Port:
If this is defined, the environment variable tftpsrcp
is used to supply the TFTP UDP source port value.
If tftpsrcp isn't defined, the normal pseudo-random port
number generator is used.
Also, the environment variable tftpdstp is used to supply
the TFTP UDP destination port value. If tftpdstp isn't
defined, the normal port 69 is used.
The purpose for tftpsrcp is to allow a TFTP server to
blindly start the TFTP transfer using the pre-configured
target IP address and UDP port. This has the effect of
"punching through" the (Windows XP) firewall, allowing
the remainder of the TFTP transfer to proceed normally.
A better solution is to properly configure the firewall,
but sometimes that is not allowed.
- Hashing support:
This enables a generic 'hash' command which can produce
hashes / digests from a few algorithms (e.g. SHA1, SHA256).
Enable the hash verify command (hash -v). This adds to code
size a little.
CONFIG_SHA1 - This option enables support of hashing using SHA1
algorithm. The hash is calculated in software.
CONFIG_SHA256 - This option enables support of hashing using
SHA256 algorithm. The hash is calculated in software.
CONFIG_SHA_HW_ACCEL - This option enables hardware acceleration
for SHA1/SHA256 hashing.
This affects the 'hash' command and also the
hash_lookup_algo() function.
CONFIG_SHA_PROG_HW_ACCEL - This option enables
hardware-acceleration for SHA1/SHA256 progressive hashing.
Data can be streamed in a block at a time and the hashing
is performed in hardware.
Note: There is also a sha1sum command, which should perhaps
be deprecated in favour of 'hash sha1'.
- Freescale i.MX specific commands:
This enables 'hdmidet' command which returns true if an
HDMI monitor is detected. This command is i.MX 6 specific.
This enables the 'bmode' (bootmode) command for forcing
a boot from specific media.
This is useful for forcing the ROM's usb downloader to
activate upon a watchdog reset which is nice when iterating
on U-Boot. Using the reset button or running bmode normal
will set it back to normal. This command currently
supports i.MX53 and i.MX6.
- bootcount support:
This enables the bootcounter support, see:
enable special bootcounter support on at91sam9xe based boards.
enable special bootcounter support on blackfin based boards.
enable special bootcounter support on da850 based boards.
enable support for the bootcounter in RAM
enable support for the bootcounter on an i2c (like RTC) device.
CONFIG_SYS_I2C_RTC_ADDR = i2c chip address
CONFIG_SYS_BOOTCOUNT_ADDR = i2c addr which is used for
the bootcounter.
- Show boot progress:
Defining this option allows to add some board-
specific code (calling a user-provided function
"show_boot_progress(int)") that enables you to show
the system's boot progress on some display (for
example, some LED's) on your board. At the moment,
the following checkpoints are implemented:
Legacy uImage format:
Arg Where When
1 common/cmd_bootm.c before attempting to boot an image
-1 common/cmd_bootm.c Image header has bad magic number
2 common/cmd_bootm.c Image header has correct magic number
-2 common/cmd_bootm.c Image header has bad checksum
3 common/cmd_bootm.c Image header has correct checksum
-3 common/cmd_bootm.c Image data has bad checksum
4 common/cmd_bootm.c Image data has correct checksum
-4 common/cmd_bootm.c Image is for unsupported architecture
5 common/cmd_bootm.c Architecture check OK
-5 common/cmd_bootm.c Wrong Image Type (not kernel, multi)
6 common/cmd_bootm.c Image Type check OK
-6 common/cmd_bootm.c gunzip uncompression error
-7 common/cmd_bootm.c Unimplemented compression type
7 common/cmd_bootm.c Uncompression OK
8 common/cmd_bootm.c No uncompress/copy overwrite error
-9 common/cmd_bootm.c Unsupported OS (not Linux, BSD, VxWorks, QNX)
9 common/image.c Start initial ramdisk verification
-10 common/image.c Ramdisk header has bad magic number
-11 common/image.c Ramdisk header has bad checksum
10 common/image.c Ramdisk header is OK
-12 common/image.c Ramdisk data has bad checksum
11 common/image.c Ramdisk data has correct checksum
12 common/image.c Ramdisk verification complete, start loading
-13 common/image.c Wrong Image Type (not PPC Linux ramdisk)
13 common/image.c Start multifile image verification
14 common/image.c No initial ramdisk, no multifile, continue.
15 arch/<arch>/lib/bootm.c All preparation done, transferring control to OS
-30 arch/powerpc/lib/board.c Fatal error, hang the system
-31 post/post.c POST test failed, detected by post_output_backlog()
-32 post/post.c POST test failed, detected by post_run_single()
34 common/cmd_doc.c before loading a Image from a DOC device
-35 common/cmd_doc.c Bad usage of "doc" command
35 common/cmd_doc.c correct usage of "doc" command
-36 common/cmd_doc.c No boot device
36 common/cmd_doc.c correct boot device
-37 common/cmd_doc.c Unknown Chip ID on boot device
37 common/cmd_doc.c correct chip ID found, device available
-38 common/cmd_doc.c Read Error on boot device
38 common/cmd_doc.c reading Image header from DOC device OK
-39 common/cmd_doc.c Image header has bad magic number
39 common/cmd_doc.c Image header has correct magic number
-40 common/cmd_doc.c Error reading Image from DOC device
40 common/cmd_doc.c Image header has correct magic number
41 common/cmd_ide.c before loading a Image from a IDE device
-42 common/cmd_ide.c Bad usage of "ide" command
42 common/cmd_ide.c correct usage of "ide" command
-43 common/cmd_ide.c No boot device
43 common/cmd_ide.c boot device found
-44 common/cmd_ide.c Device not available
44 common/cmd_ide.c Device available
-45 common/cmd_ide.c wrong partition selected
45 common/cmd_ide.c partition selected
-46 common/cmd_ide.c Unknown partition table
46 common/cmd_ide.c valid partition table found
-47 common/cmd_ide.c Invalid partition type
47 common/cmd_ide.c correct partition type
-48 common/cmd_ide.c Error reading Image Header on boot device
48 common/cmd_ide.c reading Image Header from IDE device OK
-49 common/cmd_ide.c Image header has bad magic number
49 common/cmd_ide.c Image header has correct magic number
-50 common/cmd_ide.c Image header has bad checksum
50 common/cmd_ide.c Image header has correct checksum
-51 common/cmd_ide.c Error reading Image from IDE device
51 common/cmd_ide.c reading Image from IDE device OK
52 common/cmd_nand.c before loading a Image from a NAND device
-53 common/cmd_nand.c Bad usage of "nand" command
53 common/cmd_nand.c correct usage of "nand" command
-54 common/cmd_nand.c No boot device
54 common/cmd_nand.c boot device found
-55 common/cmd_nand.c Unknown Chip ID on boot device
55 common/cmd_nand.c correct chip ID found, device available
-56 common/cmd_nand.c Error reading Image Header on boot device
56 common/cmd_nand.c reading Image Header from NAND device OK
-57 common/cmd_nand.c Image header has bad magic number
57 common/cmd_nand.c Image header has correct magic number
-58 common/cmd_nand.c Error reading Image from NAND device
58 common/cmd_nand.c reading Image from NAND device OK
-60 common/env_common.c Environment has a bad CRC, using default
64 net/eth.c starting with Ethernet configuration.
-64 net/eth.c no Ethernet found.
65 net/eth.c Ethernet found.
-80 common/cmd_net.c usage wrong
80 common/cmd_net.c before calling net_loop()
-81 common/cmd_net.c some error in net_loop() occurred
81 common/cmd_net.c net_loop() back without error
-82 common/cmd_net.c size == 0 (File with size 0 loaded)
82 common/cmd_net.c trying automatic boot
83 common/cmd_net.c running "source" command
-83 common/cmd_net.c some error in automatic boot or "source" command
84 common/cmd_net.c end without errors
FIT uImage format:
Arg Where When
100 common/cmd_bootm.c Kernel FIT Image has correct format
-100 common/cmd_bootm.c Kernel FIT Image has incorrect format
101 common/cmd_bootm.c No Kernel subimage unit name, using configuration
-101 common/cmd_bootm.c Can't get configuration for kernel subimage
102 common/cmd_bootm.c Kernel unit name specified
-103 common/cmd_bootm.c Can't get kernel subimage node offset
103 common/cmd_bootm.c Found configuration node
104 common/cmd_bootm.c Got kernel subimage node offset
-104 common/cmd_bootm.c Kernel subimage hash verification failed
105 common/cmd_bootm.c Kernel subimage hash verification OK
-105 common/cmd_bootm.c Kernel subimage is for unsupported architecture
106 common/cmd_bootm.c Architecture check OK
-106 common/cmd_bootm.c Kernel subimage has wrong type
107 common/cmd_bootm.c Kernel subimage type OK
-107 common/cmd_bootm.c Can't get kernel subimage data/size
108 common/cmd_bootm.c Got kernel subimage data/size
-108 common/cmd_bootm.c Wrong image type (not legacy, FIT)
-109 common/cmd_bootm.c Can't get kernel subimage type
-110 common/cmd_bootm.c Can't get kernel subimage comp
-111 common/cmd_bootm.c Can't get kernel subimage os
-112 common/cmd_bootm.c Can't get kernel subimage load address
-113 common/cmd_bootm.c Image uncompress/copy overwrite error
120 common/image.c Start initial ramdisk verification
-120 common/image.c Ramdisk FIT image has incorrect format
121 common/image.c Ramdisk FIT image has correct format
122 common/image.c No ramdisk subimage unit name, using configuration
-122 common/image.c Can't get configuration for ramdisk subimage
123 common/image.c Ramdisk unit name specified
-124 common/image.c Can't get ramdisk subimage node offset
125 common/image.c Got ramdisk subimage node offset
-125 common/image.c Ramdisk subimage hash verification failed
126 common/image.c Ramdisk subimage hash verification OK
-126 common/image.c Ramdisk subimage for unsupported architecture
127 common/image.c Architecture check OK
-127 common/image.c Can't get ramdisk subimage data/size
128 common/image.c Got ramdisk subimage data/size
129 common/image.c Can't get ramdisk load address
-129 common/image.c Got ramdisk load address
-130 common/cmd_doc.c Incorrect FIT image format
131 common/cmd_doc.c FIT image format OK
-140 common/cmd_ide.c Incorrect FIT image format
141 common/cmd_ide.c FIT image format OK
-150 common/cmd_nand.c Incorrect FIT image format
151 common/cmd_nand.c FIT image format OK
- legacy image format:
enables the legacy image format support in U-Boot.
enabled if CONFIG_FIT_SIGNATURE is not defined.
disable the legacy image format
This define is introduced, as the legacy image format is
enabled per default for backward compatibility.
- FIT image support:
Supporting SHA256 hashes has quite an impact on binary size.
For constrained systems sha256 hash support can be disabled
with this option.
TODO( Adjust this option to be positive,
and move it to Kconfig
- Standalone program support:
This option defines a board specific value for the
address where standalone program gets loaded, thus
overwriting the architecture dependent default
- Frame Buffer Address:
Define CONFIG_FB_ADDR if you want to use specific
address for frame buffer. This is typically the case
when using a graphics controller has separate video
memory. U-Boot will then place the frame buffer at
the given address instead of dynamically reserving it
in system RAM by calling lcd_setmem(), which grabs
the memory for the frame buffer depending on the
configured panel size.
Please see board_init_f function.
- Automatic software updates via TFTP server
These options enable and control the auto-update feature;
for a more detailed description refer to doc/README.update.
- MTD Support (mtdparts command, UBI support)
Adds the MTD device infrastructure from the Linux kernel.
Needed for mtdparts command support.
Adds the MTD partitioning infrastructure from the Linux
kernel. Needed for UBI support.
- UBI support
Adds commands for interacting with MTD partitions formatted
with the UBI flash translation layer
Requires also defining CONFIG_RBTREE
Make the verbose messages from UBI stop printing. This leaves
warnings and errors enabled.
This parameter defines the maximum difference between the highest
erase counter value and the lowest erase counter value of eraseblocks
of UBI devices. When this threshold is exceeded, UBI starts performing
wear leveling by means of moving data from eraseblock with low erase
counter to eraseblocks with high erase counter.
The default value should be OK for SLC NAND flashes, NOR flashes and
other flashes which have eraseblock life-cycle 100000 or more.
However, in case of MLC NAND flashes which typically have eraseblock
life-cycle less than 10000, the threshold should be lessened (e.g.,
to 128 or 256, although it does not have to be power of 2).
default: 4096
This option specifies the maximum bad physical eraseblocks UBI
expects on the MTD device (per 1024 eraseblocks). If the
underlying flash does not admit of bad eraseblocks (e.g. NOR
flash), this value is ignored.
NAND datasheets often specify the minimum and maximum NVM
(Number of Valid Blocks) for the flashes' endurance lifetime.
The maximum expected bad eraseblocks per 1024 eraseblocks
then can be calculated as "1024 * (1 - MinNVB / MaxNVB)",
which gives 20 for most NANDs (MaxNVB is basically the total
count of eraseblocks on the chip).
To put it differently, if this value is 20, UBI will try to
reserve about 1.9% of physical eraseblocks for bad blocks
handling. And that will be 1.9% of eraseblocks on the entire
NAND chip, not just the MTD partition UBI attaches. This means
that if you have, say, a NAND flash chip admits maximum 40 bad
eraseblocks, and it is split on two MTD partitions of the same
size, UBI will reserve 40 eraseblocks when attaching a
default: 20
Fastmap is a mechanism which allows attaching an UBI device
in nearly constant time. Instead of scanning the whole MTD device it
only has to locate a checkpoint (called fastmap) on the device.
The on-flash fastmap contains all information needed to attach
the device. Using fastmap makes only sense on large devices where
attaching by scanning takes long. UBI will not automatically install
a fastmap on old images, but you can set the UBI parameter
CONFIG_MTD_UBI_FASTMAP_AUTOCONVERT to 1 if you want so. Please note
that fastmap-enabled images are still usable with UBI implementations
without fastmap support. On typical flash devices the whole fastmap
fits into one PEB. UBI will reserve PEBs to hold two fastmaps.
Set this parameter to enable fastmap automatically on images
without a fastmap.
default: 0
Enable UBI fastmap debug
default: 0
- UBIFS support
Adds commands for interacting with UBI volumes formatted as
UBIFS. UBIFS is read-only in u-boot.
Requires UBI support as well as CONFIG_LZO
Make the verbose messages from UBIFS stop printing. This leaves
warnings and errors enabled.
- SPL framework
Enable building of SPL globally.
LDSCRIPT for linking the SPL binary.
Maximum size in memory allocated to the SPL, BSS included.
When defined, the linker checks that the actual memory
used by SPL from _start to __bss_end does not exceed it.
must not be both defined at the same time.
Maximum size of the SPL image (text, data, rodata, and
linker lists sections), BSS excluded.
When defined, the linker checks that the actual size does
not exceed it.
TEXT_BASE for linking the SPL binary.
Address to relocate to. If unspecified, this is equal to
CONFIG_SPL_TEXT_BASE (i.e. no relocation is done).
Link address for the BSS within the SPL binary.
Maximum size in memory allocated to the SPL BSS.
When defined, the linker checks that the actual memory used
by SPL from __bss_start to __bss_end does not exceed it.
must not be both defined at the same time.
Adress of the start of the stack SPL will use
When defined, SPL will panic() if the image it has
loaded does not have a signature.
Defining this is useful when code which loads images
in SPL cannot guarantee that absolutely all read errors
will be caught.
An example is the LPC32XX MLC NAND driver, which will
consider that a completely unreadable NAND block is bad,
and thus should be skipped silently.
When defined, SPL will proceed to another boot method
if the image it has loaded does not have a signature.
Adress of the start of the stack SPL will use after
relocation. If unspecified, this is equal to
Starting address of the malloc pool used in SPL.
When this option is set the full malloc is used in SPL and
it is set up by spl_init() and before that, the simple malloc()
can be used if CONFIG_SYS_MALLOC_F is defined.
The size of the malloc pool used in SPL.
Enable the SPL framework under common/. This framework
supports MMC, NAND and YMODEM loading of U-Boot and NAND
NAND loading of the Linux Kernel.
Enable booting directly to an OS from SPL.
See also: doc/README.falcon
For ARM, enable an optional function to print more information
about the running system.
Arch init code should be built for a very small image
Partition on the MMC to load U-Boot from when the MMC is being
used in raw mode
Sector to load kernel uImage from when MMC is being
used in raw mode (for Falcon mode)
Sector and number of sectors to load kernel argument
parameters from when MMC is being used in raw mode
(for falcon mode)
Partition on the MMC to load U-Boot from when the MMC is being
used in fs mode
Filename to read to load U-Boot when reading from filesystem
Filename to read to load kernel uImage when reading
from filesystem (for Falcon mode)
Filename to read to load kernel argument parameters
when reading from filesystem (for Falcon mode)
Set this for NAND SPL on PPC mpc83xx targets, so that
start.S waits for the rest of the SPL to load before
continuing (the hardware starts execution after just
loading the first page rather than the full 4K).
Avoid SPL relocation
Include nand_base.c in the SPL. Requires
SPL uses normal NAND drivers, not minimal drivers.
Include standard software ECC in the SPL
Support for NAND boot using simple NAND drivers that
expose the cmd_ctrl() interface.
Support for a lightweight UBI (fastmap) scanner and
Support to boot only raw u-boot.bin images. Use this only
if you need to save space.
Set for common ddr init with serial presence detect in
SPL binary.
Defines the size and behavior of the NAND that SPL uses
to read U-Boot
Add support NAND boot
Location in NAND to read U-Boot from
Location in memory to load U-Boot to
Size of image to load
Entry point in loaded image to jump to
Define this if you need to first read the OOB and then the
data. This is used, for example, on davinci platforms.
Support for an OMAP3-specific set of functions to return the
ID and MFR of the first attached NAND chip, if present.
Support for running image already present in ram, in SPL binary
Image offset to which the SPL should be padded before appending
the SPL payload. By default, this is defined as
CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
Final target image containing SPL and payload. Some SPLs
use an arch-specific makefile fragment instead, for
example if more than one image needs to be produced.
Printing information about a FIT image adds quite a bit of
code to SPL. So this is normally disabled in SPL. Use this
option to re-enable it. This will affect the output of the
bootm command when booting a FIT image.
- TPL framework
Enable building of TPL globally.
Image offset to which the TPL should be padded before appending
the TPL payload. By default, this is defined as
CONFIG_SPL_PAD_TO must be either 0, meaning to append the SPL
payload without any padding, or >= CONFIG_SPL_MAX_SIZE.
- Interrupt support (PPC):
There are common interrupt_init() and timer_interrupt()
for all PPC archs. interrupt_init() calls interrupt_init_cpu()
for CPU specific initialization. interrupt_init_cpu()
should set decrementer_count to appropriate value. If
CPU resets decrementer automatically after interrupt
(ppc4xx) it should set decrementer_count to zero.
timer_interrupt() calls timer_interrupt_cpu() for CPU
specific handling. If board has watchdog / status_led
/ other_activity_monitor it works automatically from
general timer_interrupt().
Board initialization settings:
During Initialization u-boot calls a number of board specific functions
to allow the preparation of board specific prerequisites, e.g. pin setup
before drivers are initialized. To enable these callbacks the
following configuration macros have to be defined. Currently this is
architecture specific, so please check arch/your_architecture/lib/board.c
typically in board_init_f() and board_init_r().
- CONFIG_BOARD_EARLY_INIT_F: Call board_early_init_f()
- CONFIG_BOARD_EARLY_INIT_R: Call board_early_init_r()
- CONFIG_BOARD_LATE_INIT: Call board_late_init()
- CONFIG_BOARD_POSTCLK_INIT: Call board_postclk_init()
Configuration Settings:
- CONFIG_SYS_SUPPORT_64BIT_DATA: Defined automatically if compiled as 64-bit.
Optionally it can be defined to support 64-bit memory commands.
- CONFIG_SYS_LONGHELP: Defined when you want long help messages included;
undefine this when you're short of memory.
- CONFIG_SYS_HELP_CMD_WIDTH: Defined when you want to override the default
width of the commands listed in the 'help' command output.
- CONFIG_SYS_PROMPT: This is what U-Boot prints on the console to
prompt for user input.
- CONFIG_SYS_CBSIZE: Buffer size for input from the Console
- CONFIG_SYS_PBSIZE: Buffer size for Console output
- CONFIG_SYS_MAXARGS: max. Number of arguments accepted for monitor commands
- CONFIG_SYS_BARGSIZE: Buffer size for Boot Arguments which are passed to
the application (usually a Linux kernel) when it is
List of legal baudrate settings for this board.
Begin and End addresses of the area used by the
simple memory test.
Enable an alternate, more extensive memory test.
Scratch address used by the alternate memory test
You only need to set this if address zero isn't writeable
Only implemented for ARMv8 for now.
If defined, the size of CONFIG_SYS_MEM_RESERVE_SECURE memory
is substracted from total RAM and won't be reported to OS.
This memory can be used as secure memory. A variable
gd->arch.secure_ram is used to track the location. In systems
the RAM base is not zero, or RAM is divided into banks,
this variable needs to be recalcuated to get the address.
If CONFIG_SYS_MEM_TOP_HIDE is defined in the board config header,
this specified memory area will get subtracted from the top
(end) of RAM and won't get "touched" at all by U-Boot. By
fixing up gd->ram_size the Linux kernel should gets passed
the now "corrected" memory size and won't touch it either.
This should work for arch/ppc and arch/powerpc. Only Linux
board ports in arch/powerpc with bootwrapper support that
recalculate the memory size from the SDRAM controller setup
will have to get fixed in Linux additionally.
This option can be used as a workaround for the 440EPx/GRx
CHIP 11 errata where the last 256 bytes in SDRAM shouldn't
be touched.
WARNING: Please make sure that this value is a multiple of
the Linux page size (normally 4k). If this is not the case,
then the end address of the Linux memory will be located at a
non page size aligned address and this could cause major
Enable temporary baudrate change while serial download
Physical start address of SDRAM. _Must_ be 0 here.
Physical start address of Flash memory.
Physical start address of boot monitor code (set by
make config files to be same as the text base address
(CONFIG_SYS_TEXT_BASE) used when linking) - same as
CONFIG_SYS_FLASH_BASE when booting from flash.
Size of memory reserved for monitor code, used to
determine _at_compile_time_ (!) if the environment is
embedded within the U-Boot image, or in a separate
flash sector.
Size of DRAM reserved for malloc() use.
Size of the malloc() pool for use before relocation. If
this is defined, then a very simple malloc() implementation
will become available before relocation. The address is just
below the global data, and the stack is moved down to make
This feature allocates regions with increasing addresses
within the region. calloc() is supported, but realloc()
is not available. free() is supported but does nothing.
The memory will be freed (or in fact just forgotten) when
U-Boot relocates itself.
Provides a simple and small malloc() and calloc() for those
boards which do not use the full malloc in SPL (which is
Size of non-cached memory area. This area of memory will be
typically located right below the malloc() area and mapped
uncached in the MMU. This is useful for drivers that would
otherwise require a lot of explicit cache maintenance. For
some drivers it's also impossible to properly maintain the
cache. For example if the regions that need to be flushed
are not a multiple of the cache-line size, *and* padding
cannot be allocated between the regions to align them (i.e.
if the HW requires a contiguous array of regions, and the
size of each region is not cache-aligned), then a flush of
one region may result in overwriting data that hardware has
written to another region in the same cache-line. This can
happen for example in network drivers where descriptors for
buffers are typically smaller than the CPU cache-line (e.g.
16 bytes vs. 32 or 64 bytes).
Non-cached memory is only supported on 32-bit ARM at present.
Normally compressed uImages are limited to an
uncompressed size of 8 MBytes. If this is not enough,
you can define CONFIG_SYS_BOOTM_LEN in your board config file
to adjust this setting to your needs.
Maximum size of memory mapped by the startup code of
the Linux kernel; all data that must be processed by
the Linux kernel (bd_info, boot arguments, FDT blob if
used) must be put below this limit, unless "bootm_low"
environment variable is defined and non-zero. In such case
all data for the Linux kernel must be between "bootm_low"
and "bootm_low" + CONFIG_SYS_BOOTMAPSZ. The environment
variable "bootm_mapsize" will override the value of
then the value in "bootm_size" will be used instead.
Enable initrd_high functionality. If defined then the
initrd_high feature is enabled and the bootm ramdisk subcommand
is enabled.
Enables allocating and saving kernel cmdline in space between
"bootm_low" and "bootm_low" + BOOTMAPSZ.
Enables allocating and saving a kernel copy of the bd_info in
space between "bootm_low" and "bootm_low" + BOOTMAPSZ.
Max number of Flash memory banks
Max number of sectors on a Flash chip
Timeout for Flash erase operations (in ms)
Timeout for Flash write operations (in ms)
Timeout for Flash set sector lock bit operation (in ms)
Timeout for Flash clear lock bits operation (in ms)
If defined, hardware flash sectors protection is used
instead of U-Boot software protection.
Enable TFTP transfers directly to flash memory;
without this option such a download has to be
performed in two steps: (1) download to RAM, and (2)
copy from RAM to flash.
The two-step approach is usually more reliable, since
you can check if the download worked before you erase
the flash, but in some situations (when system RAM is
too limited to allow for a temporary copy of the
downloaded image) this option may be very useful.
Define if the flash driver uses extra elements in the
common flash structure for storing flash geometry.
This option also enables the building of the cfi_flash driver
in the drivers directory
This option enables the building of the cfi_mtd driver
in the drivers directory. The driver exports CFI flash
to the MTD layer.
Use buffered writes to flash.
s29ws-n MirrorBit flash has non-standard addresses for buffered
write commands.
If this option is defined, the common CFI flash doesn't
print it's warning upon not recognized FLASH banks. This
is useful, if some of the configured banks are only
optionally available.
If defined (must be an integer), print out countdown
digits and dots. Recommended value: 45 (9..1) for 80
column displays, 15 (3..1) for 40 column displays.
If defined, the content of the flash (destination) is compared
against the source after the write operation. An error message
will be printed when the contents are not identical.
Please note that this option is useless in nearly all cases,
since such flash programming errors usually are detected earlier
while unprotecting/erasing/programming. Please only enable
this option if you really know what you are doing.
Defines the number of Ethernet receive buffers. On some
Ethernet controllers it is recommended to set this value
to 8 or even higher (EEPRO100 or 405 EMAC), since all
buffers can be full shortly after enabling the interface
on high Ethernet traffic.
Defaults to 4 if not defined.
Maximum number of entries in the hash table that is used
internally to store the environment settings. The default
setting is supposed to be generous and should work in most
cases. This setting can be used to tune behaviour; see
lib/hashtable.c for details.
Enable validation of the values given to environment variables when
calling env set. Variables can be restricted to only decimal,
hexadecimal, or boolean. If CONFIG_CMD_NET is also defined,
the variables can also be restricted to IP address or MAC address.
The format of the list is:
type_attribute = [s|d|x|b|i|m]
access_attribute = [a|r|o|c]
attributes = type_attribute[access_attribute]
entry = variable_name[:attributes]
list = entry[,list]
The type attributes are:
s - String (default)
d - Decimal
x - Hexadecimal
b - Boolean ([1yYtT|0nNfF])
i - IP address
m - MAC address
The access attributes are:
a - Any (default)
r - Read-only
o - Write-once
c - Change-default
Define this to a list (string) to define the ".flags"
environment variable in the default or embedded environment.
Define this to a list (string) to define validation that
should be done if an entry is not found in the ".flags"
environment variable. To override a setting in the static
list, simply add an entry for the same variable name to the
".flags" variable.
If CONFIG_REGEX is defined, the variable_name above is evaluated as a
regular expression. This allows multiple variables to define the same
flags without explicitly listing them for each variable.
If defined, don't allow the -f switch to env set override variable
access flags.
This is set by OMAP boards for the max time that reset should
be asserted. See doc/README.omap-reset-time for details on how
the value can be calculated on a given board.
If stdint.h is available with your toolchain you can define this
option to enable it. You can provide option 'USE_STDINT=1' when
building U-Boot to enable this.
The following definitions that deal with the placement and management
of environment data (variable area); in general, we support the
following configurations:
Builds up envcrc with the target environment so that external utils
may easily extract it and embed it in final U-Boot images.
Define this if the environment is in flash memory.
a) The environment occupies one whole flash sector, which is
"embedded" in the text segment with the U-Boot code. This
happens usually with "bottom boot sector" or "top boot
sector" type flash chips, which have several smaller
sectors at the start or the end. For instance, such a
layout can have sector sizes of 8, 2x4, 16, Nx32 kB. In
such a case you would place the environment in one of the
4 kB sectors - with U-Boot code before and after it. With
"top boot sector" type flash chips, you would put the
environment in one of the last sectors, leaving a gap
between U-Boot and the environment.
Offset of environment data (variable area) to the
beginning of flash memory; for instance, with bottom boot
type flash chips the second sector can be used: the offset
for this sector is given here.
This is just another way to specify the start address of
the flash sector containing the environment (instead of
Size of the sector containing the environment.
b) Sometimes flash chips have few, equal sized, BIG sectors.
In such a case you don't want to spend a whole sector for
the environment.
If you use this in combination with CONFIG_ENV_IS_IN_FLASH
and CONFIG_ENV_SECT_SIZE, you can specify to use only a part
of this flash sector for the environment. This saves
memory for the RAM copy of the environment.
It may also save flash memory if you decide to use this
when your environment is "embedded" within U-Boot code,
since then the remainder of the flash sector could be used
for U-Boot code. It should be pointed out that this is
STRONGLY DISCOURAGED from a robustness point of view:
updating the environment in flash makes it always
necessary to erase the WHOLE sector. If something goes
wrong before the contents has been restored from a copy in
RAM, your target system will be dead.
These settings describe a second storage area used to hold
a redundant copy of the environment data, so that there is
a valid backup copy in case there is a power failure during
a "saveenv" operation.
BE CAREFUL! Any changes to the flash layout, and some changes to the
source code will make it necessary to adapt <board>/*
Define this if you have some non-volatile memory device
(NVRAM, battery buffered SRAM) which you want to use for the
These two #defines are used to determine the memory area you
want to use for environment. It is assumed that this memory
can just be read and written to, without any special
BE CAREFUL! The first access to the environment happens quite early
in U-Boot initialization (when we try to get the setting of for the
console baudrate). You *MUST* have mapped your NVRAM area then, or
U-Boot will hang.
Please note that even with NVRAM we still use a copy of the
environment in RAM: we could work on NVRAM directly, but we want to
keep settings there always unmodified except somebody uses "saveenv"
to save the current settings.
Use this if you have an EEPROM or similar serial access
device and a driver for it.
These two #defines specify the offset and size of the
environment area within the total memory of your EEPROM.
If defined, specified the chip address of the EEPROM device.
The default address is zero.
If defined, specified the i2c bus of the EEPROM device.
If defined, the number of bits used to address bytes in a
single page in the EEPROM device. A 64 byte page, for example
would require six bits.
If defined, the number of milliseconds to delay between
page writes. The default is zero milliseconds.
The length in bytes of the EEPROM memory array address. Note
that this is NOT the chip address length!
EEPROM chips that implement "address overflow" are ones
like Catalyst 24WC04/08/16 which has 9/10/11 bits of
address and the extra bits end up in the "chip address" bit
slots. This makes a 24WC08 (1Kbyte) chip look like four 256
byte chips.
Note that we consider the length of the address field to
still be one byte because the extra address bits are hidden
in the chip address.
The size in bytes of the EEPROM device.
define this, if you have I2C and SPI activated, and your
EEPROM, which holds the environment, is on the I2C bus.
if you have an Environment on an EEPROM reached over
I2C muxes, you can define here, how to reach this
EEPROM. For example:
EEPROM which holds the environment, is reached over
a pca9547 i2c mux with address 0x70, channel 3.
Define this if you have a DataFlash memory device which you
want to use for the environment.
These three #defines specify the offset and size of the
environment area within the total memory of your DataFlash placed
at the specified address.
Define this if you have a SPI Flash memory device which you
want to use for the environment.
These two #defines specify the offset and size of the
environment area within the SPI Flash. CONFIG_ENV_OFFSET must be
aligned to an erase sector boundary.
Define the SPI flash's sector size.
This setting describes a second storage area of CONFIG_ENV_SIZE
size used to hold a redundant copy of the environment data, so
that there is a valid backup copy in case there is a power failure
during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
aligned to an erase sector boundary.
- CONFIG_ENV_SPI_BUS (optional):
- CONFIG_ENV_SPI_CS (optional):
Define the SPI bus and chip select. If not defined they will be 0.
- CONFIG_ENV_SPI_MAX_HZ (optional):
Define the SPI max work clock. If not defined then use 1MHz.
- CONFIG_ENV_SPI_MODE (optional):
Define the SPI work mode. If not defined then use SPI_MODE_3.
Define this if you have a remote memory space which you
want to use for the local device's environment.
These two #defines specify the address and size of the
environment area within the remote memory space. The
local device can get the environment from remote memory
space by SRIO or PCIE links.
BE CAREFUL! For some special cases, the local device can not use
"saveenv" command. For example, the local device will get the
environment stored in a remote NOR flash by SRIO or PCIE link,
but it can not erase, write this NOR flash by SRIO or PCIE interface.
Define this if you have a NAND device which you want to use
for the environment.
These two #defines specify the offset and size of the environment
area within the first NAND device. CONFIG_ENV_OFFSET must be
aligned to an erase block boundary.
This setting describes a second storage area of CONFIG_ENV_SIZE
size used to hold a redundant copy of the environment data, so
that there is a valid backup copy in case there is a power failure
during a "saveenv" operation. CONFIG_ENV_OFFSET_REDUND must be
aligned to an erase block boundary.
- CONFIG_ENV_RANGE (optional):
Specifies the length of the region in which the environment
can be written. This should be a multiple of the NAND device's
block size. Specifying a range with more erase blocks than
are needed to hold CONFIG_ENV_SIZE allows bad blocks within
the range to be avoided.
Enables support for dynamically retrieving the offset of the
environment from block zero's out-of-band data. The
"nand env.oob" command can be used to record this offset.
Currently, CONFIG_ENV_OFFSET_REDUND is not supported when
Defines address in RAM to which the nand_spl code should copy the
environment. If redundant environment is used, it will be copied to
Define this if you have an UBI volume that you want to use for the
environment. This has the benefit of wear-leveling the environment
accesses, which is important on NAND.
Define this to a string that is the mtd partition containing the UBI.
Define this to the name of the volume that you want to store the
environment in.
Define this to the name of another volume to store a second copy of
the environment in. This will enable redundant environments in UBI.
It is assumed that both volumes are in the same MTD partition.
You will probably want to define these to avoid a really noisy system
when storing the env in UBI.
Define this if you want to use the FAT file system for the environment.
Define this to a string that is the name of the block device.
Define this to a string to specify the partition of the device. It can
be as following:
"D:P", "D:0", "D", "D:" or "D:auto" (D, P are integers. And P >= 1)
- "D:P": device D partition P. Error occurs if device D has no
partition table.
- "D:0": device D.
- "D" or "D:": device D partition 1 if device D has partition
table, or the whole device D if has no partition
- "D:auto": first partition in device D with bootable flag set.
If none, first valid partition in device D. If no
partition table then means device D.
It's a string of the FAT file name. This file use to store the
This should be defined. Otherwise it cannot save the environment file.
Define this if you have an MMC device which you want to use for the
Specifies which MMC device the environment is stored in.
Specifies which MMC partition the environment is stored in. If not
set, defaults to partition 0, the user area. Common values might be
1 (first MMC boot partition), 2 (second MMC boot partition).
These two #defines specify the offset and size of the environment
area within the specified MMC device.
If offset is positive (the usual case), it is treated as relative to
the start of the MMC partition. If offset is negative, it is treated
as relative to the end of the MMC partition. This can be useful if
your board may be fitted with different MMC devices, which have
different sizes for the MMC partitions, and you always want the
environment placed at the very end of the partition, to leave the
maximum possible space before it, to store other data.
These two values are in units of bytes, but must be aligned to an
MMC sector boundary.
Specifies a second storage area, of CONFIG_ENV_SIZE size, used to
hold a redundant copy of the environment data. This provides a
valid backup copy in case the other copy is corrupted, e.g. due
to a power failure during a "saveenv" operation.
This value may also be positive or negative; this is handled in the
same way as CONFIG_ENV_OFFSET.
This value is also in units of bytes, but must also be aligned to
an MMC sector boundary.
This value need not be set, even when CONFIG_ENV_OFFSET_REDUND is
set. If this value is set, it must be set to the same value as
Defines offset to the initial SPI buffer area in DPRAM. The
area is used at an early stage (ROM part) if the environment
is configured to reside in the SPI EEPROM: We need a 520 byte
scratch DPRAM area. It is used between the two initialization
calls (spi_init_f() and spi_init_r()). A value of 0xB00 seems
to be a good choice since it makes it far enough from the
start of the data area as well as from the stack pointer.
Please note that the environment is read-only until the monitor
has been relocated to RAM and a RAM copy of the environment has been
created; also, when using EEPROM you will have to use getenv_f()
until then to read environment variables.
The environment is protected by a CRC32 checksum. Before the monitor
is relocated into RAM, as a result of a bad CRC you will be working
with the compiled-in default environment - *silently*!!! [This is
necessary, because the first environment variable we need is the
"baudrate" setting for the console - if we have a bad CRC, we don't
have any device yet where we could complain.]
Note: once the monitor has been relocated, then it will complain if
the default environment is used; a new CRC is computed as soon as you
use the "saveenv" command to store a valid environment.
Echo the inverted Ethernet link state to the fault LED.
Note: If this option is active, then CONFIG_SYS_FAULT_MII_ADDR
also needs to be defined.
MII address of the PHY to check for the Ethernet link state.
Define this if you desire to only have use of the NS16550_init
and NS16550_putc functions for the serial driver located at
drivers/serial/ns16550.c. This option is useful for saving
space for already greatly restricted images, including but not
limited to NAND_SPL configurations.
Display information about the board that U-Boot is running on
when U-Boot starts up. The board function checkboard() is called
to do this.
Similar to the previous option, but display this information
later, once stdio is running and output goes to the LCD, if
Maximum size of the U-Boot image. When defined, the
build system checks that the actual size does not
exceed it.
Low Level (hardware related) configuration options:
Cache Line Size of the CPU.
Default address of the IMMR after system reset.
Needed on some 8260 systems (MPC8260ADS, PQ2FADS-ZU,
and RPXsuper) to be able to adjust the position of
the IMMR register after a reset.
Default (power-on reset) physical address of CCSR on Freescale
PowerPC SOCs.
Virtual address of CCSR. On a 32-bit build, this is typically
CONFIG_SYS_DEFAULT_IMMR must also be set to this value,
for cross-platform code that uses that macro instead.
Physical address of CCSR. CCSR can be relocated to a new
physical address, if desired. In this case, this macro should
be set to that address. Otherwise, it should be set to the
same value as CONFIG_SYS_CCSRBAR_DEFAULT. For example, CCSR
is typically relocated on 36-bit builds. It is recommended
that this macro be defined via the _HIGH and _LOW macros:
Bits 33-36 of CONFIG_SYS_CCSRBAR_PHYS. This value is typically
either 0 (32-bit build) or 0xF (36-bit build). This macro is
used in assembly code, so it must not contain typecasts or
integer size suffixes (e.g. "ULL").
Lower 32-bits of CONFIG_SYS_CCSRBAR_PHYS. This macro is
used in assembly code, so it must not contain typecasts or
integer size suffixes (e.g. "ULL").
If this macro is defined, then CONFIG_SYS_CCSRBAR_PHYS will be
forced to a value that ensures that CCSR is not relocated.
- Floppy Disk Support:
the default drive number (default value 0)
defines the spacing between FDC chipset registers
(default value 1)
defines the offset of register from address. It
depends on which part of the data bus is connected to
the FDC chipset. (default value 0)
CONFIG_SYS_FDC_DRIVE_NUMBER are undefined, they take their
default value.
if CONFIG_SYS_FDC_HW_INIT is defined, then the function
fdc_hw_init() is called at the beginning of the FDC
setup. fdc_hw_init() must be provided by the board
source code. It is used to make hardware-dependent
Most IDE controllers were designed to be connected with PCI
interface. Only few of them were designed for AHB interface.
When software is doing ATA command and data transfer to
IDE devices through IDE-AHB controller, some additional
registers accessing to these kind of IDE-AHB controller
is required.
- CONFIG_SYS_IMMR: Physical address of the Internal Memory.
DO NOT CHANGE unless you know exactly what you're
doing! (11-4) [MPC8xx/82xx systems only]
Start address of memory area that can be used for
initial data and stack; please note that this must be
writable memory that is working WITHOUT special
initialization, i. e. you CANNOT use normal RAM which
will become available only after programming the
memory controller and running certain initialization
U-Boot uses the following memory types:
- MPC8xx and MPC8260: IMMR (internal memory of the CPU)
- MPC824X: data cache
- PPC4xx: data cache
Offset of the initial data structure in the memory
area defined by CONFIG_SYS_INIT_RAM_ADDR. Usually
CONFIG_SYS_GBL_DATA_OFFSET is chosen such that the initial
data is located at the end of the available space
(sometimes written as (CONFIG_SYS_INIT_RAM_SIZE -
GENERATED_GBL_DATA_SIZE), and the initial stack is just
below that area (growing from (CONFIG_SYS_INIT_RAM_ADDR +
On the MPC824X (or other systems that use the data
cache for initial memory) the address chosen for
CONFIG_SYS_INIT_RAM_ADDR is basically arbitrary - it must
point to an otherwise UNUSED address space between
the top of RAM and the start of the PCI space.