smarttimer.c

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  interrupt fires. 

Arguments:

  This        - The EFI_TIMER_ARCH_PROTOCOL instance.

  TimerPeriod - The rate to program the timer interrupt in 100 nS units.  If 
                the timer hardware is not programmable, then EFI_UNSUPPORTED is 
                returned.  If the timer is programmable, then the timer period 
                will be rounded up to the nearest timer period that is supported 
                by the timer hardware.  If TimerPeriod is set to 0, then the 
                timer interrupts will be disabled.

Returns: 

  EFI_SUCCESS      - The timer period was changed.

  EFI_UNSUPPORTED  - The platform cannot change the period of the timer interrupt.

  EFI_DEVICE_ERROR - The timer period could not be changed due to a device error.

--*/
{
  UINT64  TimerCount;

  //
  //  The basic clock is 1.19318 MHz or 0.119318 ticks per 100 ns.
  //  TimerPeriod * 0.119318 = 8254 timer divisor. Using integer arithmetic
  //  TimerCount = (TimerPeriod * 119318)/1000000.
  //
  //  Round up to next highest integer. This guarantees that the timer is
  //  equal to or slightly longer than the requested time.
  //  TimerCount = ((TimerPeriod * 119318) + 500000)/1000000
  //
  // Note that a TimerCount of 0 is equivalent to a count of 65,536
  //
  // Since TimerCount is limited to 16 bits for IA32, TimerPeriod is limited
  // to 20 bits.
  //
  if (TimerPeriod == 0) {
    //
    // Disable timer interrupt for a TimerPeriod of 0
    //
    mLegacy8259->DisableIrq (mLegacy8259, Efi8259Irq0);
  } else {
    //
    // Convert TimerPeriod into 8254 counts
    //
    TimerCount = DivU64x32 (MultU64x32 (119318, (UINTN) TimerPeriod) + 500000, 1000000, 0);

    //
    // Check for overflow
    //
    if (TimerCount >= 65536) {
      TimerCount = 0;
      if (TimerPeriod >= DEFAULT_TIMER_TICK_DURATION) {
        TimerPeriod = DEFAULT_TIMER_TICK_DURATION;
      }
    }
    //
    // Program the 8254 timer with the new count value
    //
    SetPitCount ((UINT16) TimerCount);

    //
    // Enable timer interrupt
    //
    mLegacy8259->EnableIrq (mLegacy8259, Efi8259Irq0, FALSE);
  }
  //
  // Save the new timer period
  //
  mTimerPeriod = TimerPeriod;

  return EFI_SUCCESS;
}

EFI_STATUS
EFIAPI
TimerDriverGetTimerPeriod (
  IN EFI_TIMER_ARCH_PROTOCOL   *This,
  OUT UINT64                   *TimerPeriod
  )
/*++

Routine Description:

  This function retrieves the period of timer interrupts in 100 ns units, 
  returns that value in TimerPeriod, and returns EFI_SUCCESS.  If TimerPeriod 
  is NULL, then EFI_INVALID_PARAMETER is returned.  If a TimerPeriod of 0 is 
  returned, then the timer is currently disabled.

Arguments:

  This        - The EFI_TIMER_ARCH_PROTOCOL instance.

  TimerPeriod - A pointer to the timer period to retrieve in 100 ns units.  If 
                0 is returned, then the timer is currently disabled.

Returns: 

  EFI_SUCCESS           - The timer period was returned in TimerPeriod.

  EFI_INVALID_PARAMETER - TimerPeriod is NULL.

--*/
{
  if (TimerPeriod == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  *TimerPeriod = mTimerPeriod;

  return EFI_SUCCESS;
}

EFI_STATUS
EFIAPI
TimerDriverGenerateSoftInterrupt (
  IN EFI_TIMER_ARCH_PROTOCOL  *This
  )
/*++

Routine Description:

  This function generates a soft timer interrupt. If the platform does not support soft 
  timer interrupts, then EFI_UNSUPPORTED is returned. Otherwise, EFI_SUCCESS is returned. 
  If a handler has been registered through the EFI_TIMER_ARCH_PROTOCOL.RegisterHandler() 
  service, then a soft timer interrupt will be generated. If the timer interrupt is 
  enabled when this service is called, then the registered handler will be invoked. The 
  registered handler should not be able to distinguish a hardware-generated timer 
  interrupt from a software-generated timer interrupt.

Arguments:

  This  -  The EFI_TIMER_ARCH_PROTOCOL instance.

Returns: 

  EFI_SUCCESS       - The soft timer interrupt was generated.

  EFI_UNSUPPORTEDT  - The platform does not support the generation of soft timer interrupts.

--*/
{
  EFI_STATUS  Status;
  UINT16      IRQMask;
  EFI_TPL     OriginalTPL;

  //
  // If the timer interrupt is enabled, then the registered handler will be invoked.
  //
  Status = mLegacy8259->GetMask (mLegacy8259, NULL, NULL, &IRQMask, NULL);
  ASSERT_EFI_ERROR (Status);
  if ((IRQMask & 0x1) == 0) {
    //
    // Invoke the registered handler
    //
    OriginalTPL = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);

    if (mTimerNotifyFunction) {
      //
      // We use the platform ACPI time counter to determine
      // the amount of time that has passed
      //
      mTimerNotifyFunction (MeasureTimeLost (mTimerPeriod));
    }

    gBS->RestoreTPL (OriginalTPL);
  } else {
    return EFI_UNSUPPORTED;
  }

  return EFI_SUCCESS;
}

EFI_ACPI_DESCRIPTION *
GetAcpiDescription (
  VOID
  )
{
  VOID                                     *HobList;
  EFI_STATUS                               Status;
  EFI_ACPI_DESCRIPTION                     *AcpiDescription;
  UINTN                                    BufferSize;

  //
  // Get Hob List from configuration table
  //
  Status = EfiLibGetSystemConfigurationTable (&gEfiHobListGuid, &HobList);
  if (EFI_ERROR (Status)) {
    return NULL;
  }

  //
  // Get AcpiDescription Hob
  //
  AcpiDescription = NULL;
  Status = GetNextGuidHob (&HobList, &gEfiAcpiDescriptionGuid, &AcpiDescription, &BufferSize);
  if (EFI_ERROR (Status)) {
    return NULL;
  }

  return AcpiDescription;
}

EFI_DRIVER_ENTRY_POINT (TimerDriverInitialize)

EFI_STATUS
EFIAPI
TimerDriverInitialize (
  IN EFI_HANDLE        ImageHandle,
  IN EFI_SYSTEM_TABLE  *SystemTable
  )
/*++

Routine Description:

  Initialize the Timer Architectural Protocol driver

Arguments:

  ImageHandle - ImageHandle of the loaded driver

  SystemTable - Pointer to the System Table

Returns:

  EFI_SUCCESS           - Timer Architectural Protocol created

  EFI_OUT_OF_RESOURCES  - Not enough resources available to initialize driver.
  
  EFI_DEVICE_ERROR      - A device error occured attempting to initialize the driver.

--*/
{
  EFI_STATUS  Status;
  UINT32      TimerVector;

  EfiInitializeDriverLib (ImageHandle, SystemTable);

  //
  // Initialize AcpiDescription
  //
  mAcpiDescription = GetAcpiDescription ();
  if (mAcpiDescription == NULL) {
    return EFI_UNSUPPORTED;
  }

  if ((mAcpiDescription->PM_TMR_LEN != 4) ||
      (mAcpiDescription->PM_TMR_BLK.Address == 0) ||
      ((mAcpiDescription->PM_TMR_BLK.AddressSpaceId != ACPI_ADDRESS_ID_IO) &&
       (mAcpiDescription->PM_TMR_BLK.AddressSpaceId != ACPI_ADDRESS_ID_MEMORY))) {
    return EFI_UNSUPPORTED;
  }

  DEBUG ((EFI_D_ERROR, "ACPI Timer Base - %lx\n", mAcpiDescription->PM_TMR_BLK.Address));

  //
  // Initialize the pointer to our notify function.
  //
  mTimerNotifyFunction = NULL;

  //
  // Make sure the Timer Architectural Protocol is not already installed in the system
  //
  ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiTimerArchProtocolGuid);

  //
  // Find the CPU I/O Protocol.  ASSERT if not found.
  //
  Status = gBS->LocateProtocol (&gEfiCpuIoProtocolGuid, NULL, (VOID **) &mCpuIo);
  ASSERT_EFI_ERROR (Status);

  //
  // Find the CPU architectural protocol.  ASSERT if not found.
  //
  Status = gBS->LocateProtocol (&gEfiCpuArchProtocolGuid, NULL, (VOID **) &mCpu);
  ASSERT_EFI_ERROR (Status);

  //
  // Find the Legacy8259 protocol.  ASSERT if not found.
  //
  Status = gBS->LocateProtocol (&gEfiLegacy8259ProtocolGuid, NULL, (VOID **) &mLegacy8259);
  ASSERT_EFI_ERROR (Status);

  //
  // Force the timer to be disabled
  //
  Status = TimerDriverSetTimerPeriod (&mTimer, 0);
  ASSERT_EFI_ERROR (Status);

  //
  // Get the interrupt vector number corresponding to IRQ0 from the 8259 driver
  //
  TimerVector = 0;
  Status      = mLegacy8259->GetVector (mLegacy8259, Efi8259Irq0, (UINT8 *) &TimerVector);
  ASSERT_EFI_ERROR (Status);

  //
  // Install interrupt handler for 8254 Timer #0 (ISA IRQ0)
  //
  Status = mCpu->RegisterInterruptHandler (mCpu, TimerVector, TimerInterruptHandler);
  ASSERT_EFI_ERROR (Status);

  //
  // Force the timer to be enabled at its default period
  //
  Status = TimerDriverSetTimerPeriod (&mTimer, DEFAULT_TIMER_TICK_DURATION);
  ASSERT_EFI_ERROR (Status);

  //
  // Begin the ACPI timer counter
  //
  mPreAcpiTick = GetAcpiTick ();

  //
  // Install the Timer Architectural Protocol onto a new handle
  //
  Status = gBS->InstallMultipleProtocolInterfaces (
                  &mTimerHandle,
                  &gEfiTimerArchProtocolGuid,
                  &mTimer,
                  NULL
                  );
  ASSERT_EFI_ERROR (Status);

  return Status;
}