system76-edk2/UefiCpuPkg/Library/SecPeiDxeTimerLibUefiCpu/X86TimerLib.c

/** @file
  Timer Library functions built upon local APIC on IA32/x64.

  This library uses the local APIC library so that it supports x2APIC mode.

  Copyright (c) 2010 - 2018, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include <Base.h>
#include <Library/TimerLib.h>
#include <Library/BaseLib.h>
#include <Library/PcdLib.h>
#include <Library/DebugLib.h>
#include <Library/LocalApicLib.h>

/**
  Internal function to return the frequency of the local APIC timer.

  @return The frequency of the timer in Hz.

**/
UINT32
EFIAPI
InternalX86GetTimerFrequency (
  VOID
  )
{
  UINTN  Divisor;

  GetApicTimerState (&Divisor, NULL, NULL);
  return PcdGet32 (PcdFSBClock) / (UINT32)Divisor;
}

/**
  Stalls the CPU for at least the given number of ticks.

  Stalls the CPU for at least the given number of ticks. It's invoked by
  MicroSecondDelay() and NanoSecondDelay().

  This function will ASSERT if the APIC timer intial count returned from
  GetApicTimerInitCount() is zero.

  @param  Delay     A period of time to delay in ticks.

**/
VOID
EFIAPI
InternalX86Delay (
  IN      UINT32  Delay
  )
{
  INT32   Ticks;
  UINT32  Times;
  UINT32  InitCount;
  UINT32  StartTick;

  //
  // In case Delay is too larger, separate it into several small delay slot.
  // Devided Delay by half value of Init Count is to avoid Delay close to
  // the Init Count, timeout maybe missing if the time consuming between 2
  // GetApicTimerCurrentCount() invoking is larger than the time gap between
  // Delay and the Init Count.
  //
  InitCount = GetApicTimerInitCount ();
  ASSERT (InitCount != 0);
  Times = Delay / (InitCount / 2);
  Delay = Delay % (InitCount / 2);

  //
  // Get Start Tick and do delay
  //
  StartTick = GetApicTimerCurrentCount ();
  do {
    //
    // Wait until time out by Delay value
    //
    do {
      CpuPause ();
      //
      // Get Ticks from Start to Current.
      //
      Ticks = StartTick - GetApicTimerCurrentCount ();
      //
      // Ticks < 0 means Timer wrap-arounds happens.
      //
      if (Ticks < 0) {
        Ticks += InitCount;
      }
    } while ((UINT32)Ticks < Delay);

    //
    // Update StartTick and Delay for next delay slot
    //
    StartTick -= (StartTick > Delay) ?  Delay : (Delay - InitCount);
    Delay      = InitCount / 2;
  } while (Times-- > 0);
}

/**
  Stalls the CPU for at least the given number of microseconds.

  Stalls the CPU for the number of microseconds specified by MicroSeconds.

  @param  MicroSeconds  The minimum number of microseconds to delay.

  @return The value of MicroSeconds inputted.

**/
UINTN
EFIAPI
MicroSecondDelay (
  IN      UINTN  MicroSeconds
  )
{
  InternalX86Delay (
    (UINT32)DivU64x32 (
              MultU64x64 (
                InternalX86GetTimerFrequency (),
                MicroSeconds
                ),
              1000000u
              )
    );
  return MicroSeconds;
}

/**
  Stalls the CPU for at least the given number of nanoseconds.

  Stalls the CPU for the number of nanoseconds specified by NanoSeconds.

  @param  NanoSeconds The minimum number of nanoseconds to delay.

  @return The value of NanoSeconds inputted.

**/
UINTN
EFIAPI
NanoSecondDelay (
  IN      UINTN  NanoSeconds
  )
{
  InternalX86Delay (
    (UINT32)DivU64x32 (
              MultU64x64 (
                InternalX86GetTimerFrequency (),
                NanoSeconds
                ),
              1000000000u
              )
    );
  return NanoSeconds;
}

/**
  Retrieves the current value of a 64-bit free running performance counter.

  The counter can either count up by 1 or count down by 1. If the physical
  performance counter counts by a larger increment, then the counter values
  must be translated. The properties of the counter can be retrieved from
  GetPerformanceCounterProperties().

  @return The current value of the free running performance counter.

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

/**
  Retrieves the 64-bit frequency in Hz and the range of performance counter
  values.

  If StartValue is not NULL, then the value that the performance counter starts
  with immediately after is it rolls over is returned in StartValue. If
  EndValue is not NULL, then the value that the performance counter end with
  immediately before it rolls over is returned in EndValue. The 64-bit
  frequency of the performance counter in Hz is always returned. If StartValue
  is less than EndValue, then the performance counter counts up. If StartValue
  is greater than EndValue, then the performance counter counts down. For
  example, a 64-bit free running counter that counts up would have a StartValue
  of 0 and an EndValue of 0xFFFFFFFFFFFFFFFF. A 24-bit free running counter
  that counts down would have a StartValue of 0xFFFFFF and an EndValue of 0.

  @param  StartValue  The value the performance counter starts with when it
                      rolls over.
  @param  EndValue    The value that the performance counter ends with before
                      it rolls over.

  @return The frequency in Hz.

**/
UINT64
EFIAPI
GetPerformanceCounterProperties (
  OUT      UINT64  *StartValue   OPTIONAL,
  OUT      UINT64  *EndValue     OPTIONAL
  )
{
  if (StartValue != NULL) {
    *StartValue = (UINT64)GetApicTimerInitCount ();
  }

  if (EndValue != NULL) {
    *EndValue = 0;
  }

  return (UINT64)InternalX86GetTimerFrequency ();
}

/**
  Converts elapsed ticks of performance counter to time in nanoseconds.

  This function converts the elapsed ticks of running performance counter to
  time value in unit of nanoseconds.

  @param  Ticks     The number of elapsed ticks of running performance counter.

  @return The elapsed time in nanoseconds.

**/
UINT64
EFIAPI
GetTimeInNanoSecond (
  IN      UINT64  Ticks
  )
{
  UINT64  Frequency;
  UINT64  NanoSeconds;
  UINT64  Remainder;
  INTN    Shift;

  Frequency = GetPerformanceCounterProperties (NULL, NULL);

  //
  //          Ticks
  // Time = --------- x 1,000,000,000
  //        Frequency
  //
  NanoSeconds = MultU64x32 (DivU64x64Remainder (Ticks, Frequency, &Remainder), 1000000000u);

  //
  // Ensure (Remainder * 1,000,000,000) will not overflow 64-bit.
  // Since 2^29 < 1,000,000,000 = 0x3B9ACA00 < 2^30, Remainder should < 2^(64-30) = 2^34,
  // i.e. highest bit set in Remainder should <= 33.
  //
  Shift        = MAX (0, HighBitSet64 (Remainder) - 33);
  Remainder    = RShiftU64 (Remainder, (UINTN)Shift);
  Frequency    = RShiftU64 (Frequency, (UINTN)Shift);
  NanoSeconds += DivU64x64Remainder (MultU64x32 (Remainder, 1000000000u), Frequency, NULL);

  return NanoSeconds;
}