PSCI: Build option to enable D-Caches early in warmboot
This patch introduces a build option to enable D-cache early on the CPU
after warm boot. This is applicable for platforms which do not require
interconnect programming to enable cache coherency (eg: single cluster
platforms). If this option is enabled, then warm boot path enables
D-caches immediately after enabling MMU.
Fixes ARM-Software/tf-issues#456
Change-Id: I44c8787d116d7217837ced3bcf0b1d3441c8d80e
Signed-off-by: Soby Mathew <soby.mathew@arm.com>
diff --git a/Makefile b/Makefile
index 9f9061c..1c2dcb9 100644
--- a/Makefile
+++ b/Makefile
@@ -459,6 +459,7 @@
$(eval $(call assert_boolean,SPIN_ON_BL1_EXIT))
$(eval $(call assert_boolean,TRUSTED_BOARD_BOOT))
$(eval $(call assert_boolean,USE_COHERENT_MEM))
+$(eval $(call assert_boolean,WARMBOOT_ENABLE_DCACHE_EARLY))
$(eval $(call assert_numeric,ARM_ARCH_MAJOR))
$(eval $(call assert_numeric,ARM_ARCH_MINOR))
@@ -496,6 +497,7 @@
$(eval $(call add_define,SPIN_ON_BL1_EXIT))
$(eval $(call add_define,TRUSTED_BOARD_BOOT))
$(eval $(call add_define,USE_COHERENT_MEM))
+$(eval $(call add_define,WARMBOOT_ENABLE_DCACHE_EARLY))
# Define the EL3_PAYLOAD_BASE flag only if it is provided.
ifdef EL3_PAYLOAD_BASE
diff --git a/bl31/aarch64/bl31_entrypoint.S b/bl31/aarch64/bl31_entrypoint.S
index 6238329..a847ae3 100644
--- a/bl31/aarch64/bl31_entrypoint.S
+++ b/bl31/aarch64/bl31_entrypoint.S
@@ -185,26 +185,27 @@
*
* The PSCI implementation invokes platform routines that enable CPUs to
* participate in coherency. On a system where CPUs are not
- * cache-coherent out of reset, having caches enabled until such time
- * might lead to coherency issues (resulting from stale data getting
- * speculatively fetched, among others). Therefore we keep data caches
- * disabled while enabling the MMU, thereby forcing data accesses to
- * have non-cacheable, nGnRnE attributes (these will always be coherent
- * with main memory).
+ * cache-coherent without appropriate platform specific programming,
+ * having caches enabled until such time might lead to coherency issues
+ * (resulting from stale data getting speculatively fetched, among
+ * others). Therefore we keep data caches disabled even after enabling
+ * the MMU for such platforms.
*
- * On systems with hardware-assisted coherency, where CPUs are expected
- * to be cache-coherent out of reset without needing explicit software
- * intervention, PSCI need not invoke platform routines to enter
- * coherency (as CPUs already are); and there's no reason to have caches
- * disabled either.
+ * On systems with hardware-assisted coherency, or on single cluster
+ * platforms, such platform specific programming is not required to
+ * enter coherency (as CPUs already are); and there's no reason to have
+ * caches disabled either.
*/
-#if HW_ASSISTED_COHERENCY
- mov x0, #0
-#else
mov x0, #DISABLE_DCACHE
-#endif
bl bl31_plat_enable_mmu
+#if HW_ASSISTED_COHERENCY || WARMBOOT_ENABLE_DCACHE_EARLY
+ mrs x0, sctlr_el3
+ orr x0, x0, #SCTLR_C_BIT
+ msr sctlr_el3, x0
+ isb
+#endif
+
bl psci_warmboot_entrypoint
#if ENABLE_RUNTIME_INSTRUMENTATION
diff --git a/bl32/sp_min/aarch32/entrypoint.S b/bl32/sp_min/aarch32/entrypoint.S
index c7f60b5..477b55b 100644
--- a/bl32/sp_min/aarch32/entrypoint.S
+++ b/bl32/sp_min/aarch32/entrypoint.S
@@ -236,24 +236,27 @@
*
* The PSCI implementation invokes platform routines that enable CPUs to
* participate in coherency. On a system where CPUs are not
- * cache-coherent out of reset, having caches enabled until such time
- * might lead to coherency issues (resulting from stale data getting
- * speculatively fetched, among others). Therefore we keep data caches
- * disabled while enabling the MMU, thereby forcing data accesses to
- * have non-cacheable, nGnRnE attributes (these will always be coherent
- * with main memory).
+ * cache-coherent without appropriate platform specific programming,
+ * having caches enabled until such time might lead to coherency issues
+ * (resulting from stale data getting speculatively fetched, among
+ * others). Therefore we keep data caches disabled even after enabling
+ * the MMU for such platforms.
*
- * On systems where CPUs are cache-coherent out of reset, however, PSCI
- * need not invoke platform routines to enter coherency (as CPUs already
- * are), and there's no reason to have caches disabled either.
+ * On systems with hardware-assisted coherency, or on single cluster
+ * platforms, such platform specific programming is not required to
+ * enter coherency (as CPUs already are); and there's no reason to have
+ * caches disabled either.
*/
-#if HW_ASSISTED_COHERENCY
- mov r0, #0
-#else
mov r0, #DISABLE_DCACHE
-#endif
bl bl32_plat_enable_mmu
+#if HW_ASSISTED_COHERENCY || WARMBOOT_ENABLE_DCACHE_EARLY
+ ldcopr r0, SCTLR
+ orr r0, r0, #SCTLR_C_BIT
+ stcopr r0, SCTLR
+ isb
+#endif
+
bl sp_min_warm_boot
/* Program the registers in cpu_context and exit monitor mode */
diff --git a/docs/user-guide.md b/docs/user-guide.md
index a1df965..af7741e 100644
--- a/docs/user-guide.md
+++ b/docs/user-guide.md
@@ -349,7 +349,8 @@
initiate the operations, and the rest is managed in hardware, minimizing
active software management. In such systems, this boolean option enables ARM
Trusted Firmware to carry out build and run-time optimizations during boot
- and power management operations. This option defaults to 0.
+ and power management operations. This option defaults to 0 and if it is
+ enabled, then it implies `WARMBOOT_ENABLE_DCACHE_EARLY` is also enabled.
* `LOAD_IMAGE_V2`: Boolean option to enable support for new version (v2) of
image loading, which provides more flexibility and scalability around what
@@ -508,6 +509,12 @@
to a string formed by concatenating the version number, build type and build
string.
+* `WARMBOOT_ENABLE_DCACHE_EARLY` : Boolean option to enable D-cache early on
+ the CPU after warm boot. This is applicable for platforms which do not
+ require interconnect programming to enable cache coherency (eg: single
+ cluster platforms). If this option is enabled, then warm boot path
+ enables D-caches immediately after enabling MMU. This option defaults to 0.
+
#### ARM development platform specific build options
* `ARM_BL31_IN_DRAM`: Boolean option to select loading of BL31 in TZC secured
diff --git a/lib/psci/psci_on.c b/lib/psci/psci_on.c
index 675ed66..76e67a3 100644
--- a/lib/psci/psci_on.c
+++ b/lib/psci/psci_on.c
@@ -165,7 +165,7 @@
*/
psci_plat_pm_ops->pwr_domain_on_finish(state_info);
-#if !HW_ASSISTED_COHERENCY
+#if !(HW_ASSISTED_COHERENCY || WARMBOOT_ENABLE_DCACHE_EARLY)
/*
* Arch. management: Enable data cache and manage stack memory
*/
diff --git a/lib/psci/psci_suspend.c b/lib/psci/psci_suspend.c
index 08c8fd6..bf95df2 100644
--- a/lib/psci/psci_suspend.c
+++ b/lib/psci/psci_suspend.c
@@ -302,7 +302,7 @@
*/
psci_plat_pm_ops->pwr_domain_suspend_finish(state_info);
-#if !HW_ASSISTED_COHERENCY
+#if !(HW_ASSISTED_COHERENCY || WARMBOOT_ENABLE_DCACHE_EARLY)
/* Arch. management: Enable the data cache, stack memory maintenance. */
psci_do_pwrup_cache_maintenance();
#endif
diff --git a/make_helpers/defaults.mk b/make_helpers/defaults.mk
index e66f511..903363a 100644
--- a/make_helpers/defaults.mk
+++ b/make_helpers/defaults.mk
@@ -154,3 +154,9 @@
# Build verbosity
V := 0
+
+# Whether to enable D-Cache early during warm boot. This is usually
+# applicable for platforms wherein interconnect programming is not
+# required to enable cache coherency after warm reset (eg: single cluster
+# platforms).
+WARMBOOT_ENABLE_DCACHE_EARLY := 0
