PcAtChipsetPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.c

   1 /** @file
   2   ACPI Timer implements one instance of Timer Library.
   3
   4   Copyright (c) 2013 - 2014, Intel Corporation. All rights reserved.<BR>
   5   This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 #include <Base.h>
  16 #include <Library/TimerLib.h>
  17 #include <Library/BaseLib.h>
  18
  19 /**
  20   Internal function to retrieves the 64-bit frequency in Hz.
  21
  22   Internal function to retrieves the 64-bit frequency in Hz.
  23
  24   @return The frequency in Hz.
  25
  26 **/
  27 UINT64
  28 InternalGetPerformanceCounterFrequency (
  29   VOID
  30   )
  31 {
  32   BOOLEAN  InterruptState;
  33   UINT64   Count;
  34   UINT64   Frequency;
  35
  36   InterruptState = SaveAndDisableInterrupts ();
  37   Count = GetPerformanceCounter ();
  38   MicroSecondDelay (100);
  39   Frequency = MultU64x32 (GetPerformanceCounter () - Count, 10000);
  40   SetInterruptState (InterruptState);
  41   return Frequency;
  42 }