source: vbox/trunk/src/VBox/Devices/EFI/Firmware/UefiCpuPkg/Library/CpuTimerLib/PeiCpuTimerLib.c@ 85788

/** @file
  CPUID Leaf 0x15 for Core Crystal Clock frequency instance as PEI Timer Library.

  Copyright (c) 2019 Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <PiPei.h>
#include <Library/TimerLib.h>
#include <Library/BaseLib.h>
#include <Library/HobLib.h>
#include <Library/DebugLib.h>

extern GUID mCpuCrystalFrequencyHobGuid;

/**
  CPUID Leaf 0x15 for Core Crystal Clock Frequency.

  The TSC counting frequency is determined by using CPUID leaf 0x15. Frequency in MHz = Core XTAL frequency * EBX/EAX.
  In newer flavors of the CPU, core xtal frequency is returned in ECX or 0 if not supported.
  @return The number of TSC counts per second.

**/
UINT64
CpuidCoreClockCalculateTscFrequency (
  VOID
  );

/**
  Internal function to retrieves the 64-bit frequency in Hz.

  Internal function to retrieves the 64-bit frequency in Hz.

  @return The frequency in Hz.

**/
UINT64
InternalGetPerformanceCounterFrequency (
  VOID
  )
{
  UINT64              *CpuCrystalCounterFrequency;
  EFI_HOB_GUID_TYPE   *GuidHob;

  CpuCrystalCounterFrequency = NULL;
  GuidHob = GetFirstGuidHob (&mCpuCrystalFrequencyHobGuid);
  if (GuidHob == NULL) {
    CpuCrystalCounterFrequency  = (UINT64*)BuildGuidHob(&mCpuCrystalFrequencyHobGuid, sizeof (*CpuCrystalCounterFrequency));
    ASSERT (CpuCrystalCounterFrequency != NULL);
    *CpuCrystalCounterFrequency = CpuidCoreClockCalculateTscFrequency ();
  } else {
    CpuCrystalCounterFrequency = (UINT64*)GET_GUID_HOB_DATA (GuidHob);
  }

  return  *CpuCrystalCounterFrequency;
}