ArmArchTimerLib.c

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#include <Base.h>
#include <Library/ArmLib.h>
#include <Library/BaseLib.h>
#include <Library/TimerLib.h>
#include <Library/DebugLib.h>
#include <Library/PcdLib.h>
#include <Library/ArmGenericTimerCounterLib.h>
 
#define TICKS_PER_MICRO_SEC  (PcdGet32 (PcdArmArchTimerFreqInHz)/1000000U)
 
// Select appropriate multiply function for platform architecture.
#ifdef MDE_CPU_ARM
#define MULT_U64_X_N  MultU64x32
#else
#define MULT_U64_X_N  MultU64x64
#endif
 
RETURN_STATUS
EFIAPI
TimerConstructor (
  VOID
  )
{
  //
  // Check if the ARM Generic Timer Extension is implemented.
  //
  if (ArmIsArchTimerImplemented ()) {
    //
    // Check if Architectural Timer frequency is pre-determined by the platform
    // (ie. nonzero).
    //
    if (PcdGet32 (PcdArmArchTimerFreqInHz) != 0) {
      //
      // Check if ticks/uS is not 0. The Architectural timer runs at constant
      // frequency, irrespective of CPU frequency. According to Generic Timer
      // Ref manual, lower bound of the frequency is in the range of 1-10MHz.
      //
      ASSERT (TICKS_PER_MICRO_SEC);
 
 #ifdef MDE_CPU_ARM
      //
      // Only set the frequency for ARMv7. We expect the secure firmware to
      // have already done it.
      // If the security extension is not implemented, set Timer Frequency
      // here.
      //
      if (ArmHasSecurityExtensions ()) {
        ArmGenericTimerSetTimerFreq (PcdGet32 (PcdArmArchTimerFreqInHz));
      }
 
 #endif
    }
 
    //
    // Architectural Timer Frequency must be set in Secure privileged
    // mode (if secure extension is supported).
    // If the reset value (0) is returned, just ASSERT.
    //
    ASSERT (ArmGenericTimerGetTimerFreq () != 0);
  } else {
    DEBUG ((DEBUG_ERROR, "ARM Architectural Timer is not available in the CPU, hence this library cannot be used.\n"));
    ASSERT (0);
  }
 
  return RETURN_SUCCESS;
}
 
STATIC
UINTN
EFIAPI
GetPlatformTimerFreq (
  )
{
  UINTN  TimerFreq;
 
  TimerFreq = PcdGet32 (PcdArmArchTimerFreqInHz);
  if (TimerFreq == 0) {
    TimerFreq = ArmGenericTimerGetTimerFreq ();
  }
 
  return TimerFreq;
}
 
UINTN
EFIAPI
MicroSecondDelay (
  IN      UINTN  MicroSeconds
  )
{
  UINT64  TimerTicks64;
  UINT64  SystemCounterVal;
 
  // Calculate counter ticks that represent requested delay:
  //  = MicroSeconds x TICKS_PER_MICRO_SEC
  //  = MicroSeconds x Frequency.10^-6
  TimerTicks64 = DivU64x32 (
                   MULT_U64_X_N (
                     MicroSeconds,
                     GetPlatformTimerFreq ()
                     ),
                   1000000U
                   );
 
  // Read System Counter value
  SystemCounterVal = ArmGenericTimerGetSystemCount ();
 
  TimerTicks64 += SystemCounterVal;
 
  // Wait until delay count expires.
  while (SystemCounterVal < TimerTicks64) {
    SystemCounterVal = ArmGenericTimerGetSystemCount ();
  }
 
  return MicroSeconds;
}
 
UINTN
EFIAPI
NanoSecondDelay (
  IN  UINTN  NanoSeconds
  )
{
  UINTN  MicroSeconds;
 
  // Round up to 1us Tick Number
  MicroSeconds  = NanoSeconds / 1000;
  MicroSeconds += ((NanoSeconds % 1000) == 0) ? 0 : 1;
 
  MicroSecondDelay (MicroSeconds);
 
  return NanoSeconds;
}
 
UINT64
EFIAPI
GetPerformanceCounter (
  VOID
  )
{
  // Just return the value of system count
  return ArmGenericTimerGetSystemCount ();
}
 
UINT64
EFIAPI
GetPerformanceCounterProperties (
  OUT      UINT64  *StartValue   OPTIONAL,
  OUT      UINT64  *EndValue     OPTIONAL
  )
{
  if (StartValue != NULL) {
    // Timer starts at 0
    *StartValue = (UINT64)0ULL;
  }
 
  if (EndValue != NULL) {
    // Timer counts up.
    *EndValue = 0xFFFFFFFFFFFFFFFFUL;
  }
 
  return (UINT64)ArmGenericTimerGetTimerFreq ();
}
 
UINT64
EFIAPI
GetTimeInNanoSecond (
  IN      UINT64  Ticks
  )
{
  UINT64  NanoSeconds;
  UINT32  Remainder;
  UINT32  TimerFreq;
 
  TimerFreq = GetPlatformTimerFreq ();
  //
  //          Ticks
  // Time = --------- x 1,000,000,000
  //        Frequency
  //
  NanoSeconds = MULT_U64_X_N (
                  DivU64x32Remainder (
                    Ticks,
                    TimerFreq,
                    &Remainder
                    ),
                  1000000000U
                  );
 
  //
  // Frequency < 0x100000000, so Remainder < 0x100000000, then (Remainder * 1,000,000,000)
  // will not overflow 64-bit.
  //
  NanoSeconds += DivU64x32 (
                   MULT_U64_X_N (
                     (UINT64)Remainder,
                     1000000000U
                     ),
                   TimerFreq
                   );
 
  return NanoSeconds;
}