/** @file | |
A Dxe Timer Library implementation which uses the Time Stamp Counter in the processor. | |
For Pentium 4 processors, Intel Xeon processors (family [0FH], models [03H and higher]); | |
for Intel Core Solo and Intel Core Duo processors (family [06H], model [0EH]); | |
for the Intel Xeon processor 5100 series and Intel Core 2 Duo processors (family [06H], model [0FH]); | |
for Intel Core 2 and Intel Xeon processors (family [06H], display_model [17H]); | |
for Intel Atom processors (family [06H], display_model [1CH]): | |
the time-stamp counter increments at a constant rate. | |
That rate may be set by the maximum core-clock to bus-clock ratio of the processor or may be set by | |
the maximum resolved frequency at which the processor is booted. The maximum resolved frequency may | |
differ from the maximum qualified frequency of the processor. | |
The specific processor configuration determines the behavior. Constant TSC behavior ensures that the | |
duration of each clock tick is uniform and supports the use of the TSC as a wall clock timer even if | |
the processor core changes frequency. This is the architectural behavior moving forward. | |
A Processor's support for invariant TSC is indicated by CPUID.0x80000007.EDX[8]. | |
Copyright (c) 2009 - 2011, Intel Corporation. All rights reserved.<BR> | |
This program and the accompanying materials | |
are licensed and made available under the terms and conditions of the BSD License | |
which accompanies this distribution. The full text of the license may be found at | |
http://opensource.org/licenses/bsd-license.php | |
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS, | |
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED. | |
**/ | |
#include <PiDxe.h> | |
#include <Library/UefiBootServicesTableLib.h> | |
#include <Library/UefiLib.h> | |
#include <Library/DebugLib.h> | |
#include <Guid/TscFrequency.h> | |
#include "TscTimerLibInternal.h" | |
UINT64 mTscFrequency; | |
/** The constructor function determines the actual TSC frequency. | |
First, Get TSC frequency from system configuration table with TSC frequency GUID, | |
if the table is not found, install it. | |
This function will always return EFI_SUCCESS. | |
@param ImageHandle The firmware allocated handle for the EFI image. | |
@param SystemTable A pointer to the EFI System Table. | |
@retval EFI_SUCCESS The constructor always returns EFI_SUCCESS. | |
**/ | |
EFI_STATUS | |
EFIAPI | |
DxeTscTimerLibConstructor ( | |
IN EFI_HANDLE ImageHandle, | |
IN EFI_SYSTEM_TABLE *SystemTable | |
) | |
{ | |
EFI_STATUS Status; | |
UINT64 *TscFrequency; | |
TscFrequency = NULL; | |
// | |
// Get TSC frequency from system configuration table with TSC frequency GUID. | |
// | |
Status = EfiGetSystemConfigurationTable (&gEfiTscFrequencyGuid, (VOID **) &TscFrequency); | |
if (Status == EFI_SUCCESS) { | |
ASSERT (TscFrequency != NULL); | |
mTscFrequency = *TscFrequency; | |
return EFI_SUCCESS; | |
} | |
// | |
// TSC frequency GUID system configuration table is not found, install it. | |
// | |
Status = gBS->AllocatePool (EfiBootServicesData, sizeof (UINT64), (VOID **) &TscFrequency); | |
ASSERT_EFI_ERROR (Status); | |
*TscFrequency = InternalCalculateTscFrequency (); | |
// | |
// TscFrequency now points to the number of TSC counts per second, install system configuration table for it. | |
// | |
gBS->InstallConfigurationTable (&gEfiTscFrequencyGuid, TscFrequency); | |
mTscFrequency = *TscFrequency; | |
return EFI_SUCCESS; | |
} | |
/** Get TSC frequency. | |
@return The number of TSC counts per second. | |
**/ | |
UINT64 | |
InternalGetTscFrequency ( | |
VOID | |
) | |
{ | |
return mTscFrequency; | |
} | |