system76-edk2/SourceLevelDebugPkg/Library/DebugAgent/DebugAgentCommon/DebugTimer.c

/** @file
  Code for debug timer to support debug agent library implementation.

  Copyright (c) 2010 - 2015, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "DebugAgent.h"

/**
  Initialize CPU local APIC timer.

  @param[out] TimerFrequency  Local APIC timer frequency returned.
  @param[in]  DumpFlag        If TRUE, dump Local APIC timer's parameter.

  @return   32-bit Local APIC timer init count.
**/
UINT32
InitializeDebugTimer (
  OUT UINT32     *TimerFrequency,
  IN  BOOLEAN    DumpFlag
  )
{
  UINTN       ApicTimerDivisor;
  UINT32      InitialCount;
  UINT32      ApicTimerFrequency;

  InitializeLocalApicSoftwareEnable (TRUE);
  GetApicTimerState (&ApicTimerDivisor, NULL, NULL);
  ApicTimerFrequency = PcdGet32(PcdFSBClock) / (UINT32)ApicTimerDivisor;
  //
  // Cpu Local Apic timer interrupt frequency, it is set to 0.1s
  //
  InitialCount = (UINT32)DivU64x32 (
                   MultU64x64 (
                     ApicTimerFrequency,
                     DEBUG_TIMER_INTERVAL
                     ),
                   1000000u
                   );

  InitializeApicTimer (ApicTimerDivisor, InitialCount, TRUE, DEBUG_TIMER_VECTOR);
  //
  // Disable Debug Timer interrupt to avoid it is delivered before Debug Port
  // is initialized
  //
  DisableApicTimerInterrupt ();

  if (DumpFlag) {
    DEBUG ((EFI_D_INFO, "Debug Timer: FSB Clock    = %d\n", PcdGet32(PcdFSBClock)));
    DEBUG ((EFI_D_INFO, "Debug Timer: Divisor      = %d\n", ApicTimerDivisor));
    DEBUG ((EFI_D_INFO, "Debug Timer: Frequency    = %d\n", ApicTimerFrequency));
    DEBUG ((EFI_D_INFO, "Debug Timer: InitialCount = %d\n", InitialCount));
  }
  if (TimerFrequency != NULL) {
    *TimerFrequency = ApicTimerFrequency;
  }
  return InitialCount;
}

/**
  Enable/Disable the interrupt of debug timer and return the interrupt state
  prior to the operation.

  If EnableStatus is TRUE, enable the interrupt of debug timer.
  If EnableStatus is FALSE, disable the interrupt of debug timer.

  @param[in] EnableStatus    Enable/Disable.

  @retval TRUE  Debug timer interrupt were enabled on entry to this call.
  @retval FALSE Debug timer interrupt were disabled on entry to this call.

**/
BOOLEAN
EFIAPI
SaveAndSetDebugTimerInterrupt (
  IN BOOLEAN                EnableStatus
  )
{
  BOOLEAN     OldDebugTimerInterruptState;

  OldDebugTimerInterruptState = GetApicTimerInterruptState ();

  if (OldDebugTimerInterruptState != EnableStatus) {
    if (EnableStatus) {
      EnableApicTimerInterrupt ();
    } else {
      DisableApicTimerInterrupt ();
    }
    //
    // Validate the Debug Timer interrupt state
    // This will make additional delay after Local Apic Timer interrupt state is changed.
    // Thus, CPU could handle the potential pending interrupt of Local Apic timer.
    //
    while (GetApicTimerInterruptState () != EnableStatus) {
      CpuPause ();
    }
  }

  return OldDebugTimerInterruptState;
}

/**
  Check if the timer is time out.

  @param[in] TimerCycle             Timer initial count.
  @param[in] Timer                  The start timer from the begin.
  @param[in] TimeoutTicker          Ticker number need time out.

  @return TRUE  Timer time out occurs.
  @retval FALSE Timer does not time out.

**/
BOOLEAN
IsDebugTimerTimeout (
  IN UINT32                     TimerCycle,
  IN UINT32                     Timer,
  IN UINT32                     TimeoutTicker
  )
{
  UINT64  CurrentTimer;
  UINT64  Delta;

  CurrentTimer = GetApicTimerCurrentCount ();

  //
  // This timer counter counts down.  Check for roll over condition.
  // If CurrentTimer is equal to Timer, it does not mean that roll over
  // happened.
  //
  if (CurrentTimer <= Timer) {
    Delta = Timer - CurrentTimer;
  } else {
    //
    // Handle one roll-over.
    //
    Delta = TimerCycle - (CurrentTimer - Timer) + 1;
  }

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