UefiCpuPkg/PiSmmCpuDxeSmm/SyncTimer.c

   1 /** @file
   2 SMM Timer feature support
   3
   4 Copyright (c) 2009 - 2015, Intel Corporation. All rights reserved.<BR>
   5 SPDX-License-Identifier: BSD-2-Clause-Patent
   6
   7 **/
   8
   9 #include "PiSmmCpuDxeSmm.h"
  10
  11 UINT64  mTimeoutTicker = 0;
  12 //
  13 //  Number of counts in a roll-over cycle of the performance counter.
  14 //
  15 UINT64  mCycle = 0;
  16 //
  17 // Flag to indicate the performance counter is count-up or count-down.
  18 //
  19 BOOLEAN  mCountDown;
  20
  21 /**
  22   Initialize Timer for SMM AP Sync.
  23
  24 **/
  25 VOID
  26 InitializeSmmTimer (
  27   VOID
  28   )
  29 {
  30   UINT64  TimerFrequency;
  31   UINT64  Start;
  32   UINT64  End;
  33
  34   TimerFrequency = GetPerformanceCounterProperties (&Start, &End);
  35   mTimeoutTicker = DivU64x32 (
  36                      MultU64x64 (TimerFrequency, PcdGet64 (PcdCpuSmmApSyncTimeout)),
  37                      1000 * 1000
  38                      );
  39   if (End < Start) {
  40     mCountDown = TRUE;
  41     mCycle     = Start - End;
  42   } else {
  43     mCountDown = FALSE;
  44     mCycle     = End - Start;
  45   }
  46 }
  47
  48 /**
  49   Start Timer for SMM AP Sync.
  50
  51 **/
  52 UINT64
  53 EFIAPI
  54 StartSyncTimer (
  55   VOID
  56   )
  57 {
  58   return GetPerformanceCounter ();
  59 }
  60
  61 /**
  62   Check if the SMM AP Sync timer is timeout.
  63
  64   @param Timer  The start timer from the begin.
  65
  66 **/
  67 BOOLEAN
  68 EFIAPI
  69 IsSyncTimerTimeout (
  70   IN      UINT64  Timer
  71   )
  72 {
  73   UINT64  CurrentTimer;
  74   UINT64  Delta;
  75
  76   CurrentTimer = GetPerformanceCounter ();
  77   //
  78   // We need to consider the case that CurrentTimer is equal to Timer
  79   // when some timer runs too slow and CPU runs fast. We think roll over
  80   // condition does not happen on this case.
  81   //
  82   if (mCountDown) {
  83     //
  84     // The performance counter counts down.  Check for roll over condition.
  85     //
  86     if (CurrentTimer <= Timer) {
  87       Delta = Timer - CurrentTimer;
  88     } else {
  89       //
  90       // Handle one roll-over.
  91       //
  92       Delta = mCycle - (CurrentTimer - Timer) + 1;
  93     }
  94   } else {
  95     //
  96     // The performance counter counts up.  Check for roll over condition.
  97     //
  98     if (CurrentTimer >= Timer) {
  99       Delta = CurrentTimer - Timer;
 100     } else {
 101       //
 102       // Handle one roll-over.
 103       //
 104       Delta = mCycle - (Timer - CurrentTimer) + 1;
 105     }
 106   }
 107
 108   return (BOOLEAN)(Delta >= mTimeoutTicker);
 109 }