UefiCpuPkg/Library/CpuTimerLib/BaseCpuTimerLib.c

   1 /** @file
   2   CPUID Leaf 0x15 for Core Crystal Clock frequency instance as Base Timer Library.
   3
   4   Copyright (c) 2019 Intel Corporation. All rights reserved.<BR>
   5   SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include <Base.h>
  10 #include <Library/TimerLib.h>
  11 #include <Library/BaseLib.h>
  12
  13 /**
  14   CPUID Leaf 0x15 for Core Crystal Clock Frequency.
  15
  16   The TSC counting frequency is determined by using CPUID leaf 0x15. Frequency in MHz = Core XTAL frequency * EBX/EAX.
  17   In newer flavors of the CPU, core xtal frequency is returned in ECX or 0 if not supported.
  18   @return The number of TSC counts per second.
  19
  20 **/
  21 UINT64
  22 CpuidCoreClockCalculateTscFrequency (
  23   VOID
  24   );
  25
  26 /**
  27   Internal function to retrieves the 64-bit frequency in Hz.
  28
  29   Internal function to retrieves the 64-bit frequency in Hz.
  30
  31   @return The frequency in Hz.
  32
  33 **/
  34 UINT64
  35 InternalGetPerformanceCounterFrequency (
  36   VOID
  37   )
  38 {
  39   return CpuidCoreClockCalculateTscFrequency ();
  40 }