audk/UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c

/** @file
SMM Timer feature support

Copyright (c) 2009 - 2015, 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 "PiSmmCpuDxeSmm.h"

UINT64   mTimeoutTicker = 0;
//
//  Number of counts in a roll-over cycle of the performance counter.
//
UINT64   mCycle = 0;
//
// Flag to indicate the performance counter is count-up or count-down.
//
BOOLEAN  mCountDown;

/**
  Initialize Timer for SMM AP Sync.

**/
VOID
InitializeSmmTimer (
  VOID
  )
{
  UINT64  TimerFrequency;
  UINT64  Start;
  UINT64  End;

  TimerFrequency = GetPerformanceCounterProperties (&Start, &End);
  mTimeoutTicker = DivU64x32 (
                     MultU64x64(TimerFrequency, PcdGet64 (PcdCpuSmmApSyncTimeout)),
                     1000 * 1000
                     );
  if (End < Start) {
    mCountDown = TRUE;
    mCycle = Start - End;
  } else {
    mCountDown = FALSE;
    mCycle = End - Start;
  }
}

/**
  Start Timer for SMM AP Sync.

**/
UINT64
EFIAPI
StartSyncTimer (
  VOID
  )
{
  return GetPerformanceCounter ();
}


/**
  Check if the SMM AP Sync timer is timeout.

  @param Timer  The start timer from the begin.

**/
BOOLEAN
EFIAPI
IsSyncTimerTimeout (
  IN      UINT64                    Timer
  )
{
  UINT64  CurrentTimer;
  UINT64  Delta;

  CurrentTimer = GetPerformanceCounter ();
  //
  // We need to consider the case that CurrentTimer is equal to Timer
  // when some timer runs too slow and CPU runs fast. We think roll over
  // condition does not happen on this case.
  //
  if (mCountDown) {
    //
    // The performance counter counts down.  Check for roll over condition.
    //
    if (CurrentTimer <= Timer) {
      Delta = Timer - CurrentTimer;
    } else {
      //
      // Handle one roll-over.
      //
      Delta = mCycle - (CurrentTimer - Timer) + 1;
    }
  } else {
    //
    // The performance counter counts up.  Check for roll over condition.
    //
    if (CurrentTimer >= Timer) {
      Delta = CurrentTimer - Timer;
    } else {
      //
      // Handle one roll-over.
      //
      Delta = mCycle - (Timer - CurrentTimer) + 1;
    }
  }

  return (BOOLEAN) (Delta >= mTimeoutTicker);
}