df2ec2aab0
The DXE & MM standalone variant of AcpiTimerLib defines a global named mPerformanceCounterFrequency. A global with an identical name is also present in MdeModulePkg/Bus/Pci/XhciDxe/Xhci.c Since XhciDxe has a dependency on TimerLib, this can cause link errors due to the same symbol being defined twice if the platform DSC chooses to use AcpiTimerLib as the TimerLib implementation for any given platform. To resolve this, I have changed made the definition of mPerformanceCounterFrequency to static and renamed it to mAcpiTimerLibTscFrequency. Since this variable is not used outside of the DxeStandaloneMmAcpiTimerLib.c compilation unit, there is no reason to have it exported as a global. Reviewed-by: Ray Ni <ray.ni@intel.com> Cc: Michael D Kinney <michael.d.kinney@intel.com> Signed-off-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
102 lines
2.3 KiB
C
102 lines
2.3 KiB
C
/** @file
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ACPI Timer implements one instance of Timer Library.
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Copyright (c) 2013 - 2023, Intel Corporation. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#include <PiDxe.h>
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#include <Library/TimerLib.h>
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#include <Library/BaseLib.h>
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#include <Library/HobLib.h>
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//
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// Cached performance counter frequency
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//
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static UINT64 mAcpiTimerLibTscFrequency = 0;
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extern GUID mFrequencyHobGuid;
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/**
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The constructor function enables ACPI IO space.
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If ACPI I/O space not enabled, this function will enable it.
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It will always return RETURN_SUCCESS.
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@retval EFI_SUCCESS The constructor always returns RETURN_SUCCESS.
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**/
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RETURN_STATUS
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EFIAPI
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AcpiTimerLibConstructor (
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VOID
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);
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/**
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Calculate TSC frequency.
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The TSC counting frequency is determined by comparing how far it counts
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during a 101.4 us period as determined by the ACPI timer.
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The ACPI timer is used because it counts at a known frequency.
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The TSC is sampled, followed by waiting 363 counts of the ACPI timer,
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or 101.4 us. The TSC is then sampled again. The difference multiplied by
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9861 is the TSC frequency. There will be a small error because of the
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overhead of reading the ACPI timer. An attempt is made to determine and
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compensate for this error.
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@return The number of TSC counts per second.
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**/
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UINT64
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InternalCalculateTscFrequency (
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VOID
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);
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/**
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Internal function to retrieves the 64-bit frequency in Hz.
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Internal function to retrieves the 64-bit frequency in Hz.
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@return The frequency in Hz.
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**/
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UINT64
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InternalGetPerformanceCounterFrequency (
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VOID
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)
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{
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return mAcpiTimerLibTscFrequency;
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}
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/**
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The constructor function enables ACPI IO space, and caches PerformanceCounterFrequency.
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@retval EFI_SUCCESS The constructor always returns RETURN_SUCCESS.
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**/
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EFI_STATUS
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CommonAcpiTimerLibConstructor (
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VOID
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)
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{
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EFI_HOB_GUID_TYPE *GuidHob;
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//
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// Enable ACPI IO space.
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//
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AcpiTimerLibConstructor ();
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//
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// Initialize PerformanceCounterFrequency
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//
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GuidHob = GetFirstGuidHob (&mFrequencyHobGuid);
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if (GuidHob != NULL) {
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mAcpiTimerLibTscFrequency = *(UINT64 *)GET_GUID_HOB_DATA (GuidHob);
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} else {
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mAcpiTimerLibTscFrequency = InternalCalculateTscFrequency ();
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}
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return EFI_SUCCESS;
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}
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