system76-edk2/MdeModulePkg/Core/Dxe/Event/Timer.c

/** @file
  Core Timer Services

Copyright (c) 2006 - 2013, Intel Corporation. All rights reserved.<BR>
This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution.  The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php

THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.

**/


#include "DxeMain.h"
#include "Event.h"

//
// Internal data
//

LIST_ENTRY       mEfiTimerList = INITIALIZE_LIST_HEAD_VARIABLE (mEfiTimerList);
EFI_LOCK         mEfiTimerLock = EFI_INITIALIZE_LOCK_VARIABLE (TPL_HIGH_LEVEL - 1);
EFI_EVENT        mEfiCheckTimerEvent = NULL;

EFI_LOCK         mEfiSystemTimeLock = EFI_INITIALIZE_LOCK_VARIABLE (TPL_HIGH_LEVEL);
UINT64           mEfiSystemTime = 0;

//
// Timer functions
//
/**
  Inserts the timer event.

  @param  Event                  Points to the internal structure of timer event
                                 to be installed

**/
VOID
CoreInsertEventTimer (
  IN IEVENT   *Event
  )
{
  UINT64          TriggerTime;
  LIST_ENTRY      *Link;
  IEVENT          *Event2;

  ASSERT_LOCKED (&mEfiTimerLock);

  //
  // Get the timer's trigger time
  //
  TriggerTime = Event->Timer.TriggerTime;

  //
  // Insert the timer into the timer database in assending sorted order
  //
  for (Link = mEfiTimerList.ForwardLink; Link != &mEfiTimerList; Link = Link->ForwardLink) {
    Event2 = CR (Link, IEVENT, Timer.Link, EVENT_SIGNATURE);

    if (Event2->Timer.TriggerTime > TriggerTime) {
      break;
    }
  }

  InsertTailList (Link, &Event->Timer.Link);
}

/**
  Returns the current system time.

  @return The current system time

**/
UINT64
CoreCurrentSystemTime (
  VOID
  )
{
  UINT64          SystemTime;

  CoreAcquireLock (&mEfiSystemTimeLock);
  SystemTime = mEfiSystemTime;
  CoreReleaseLock (&mEfiSystemTimeLock);

  return SystemTime;
}

/**
  Checks the sorted timer list against the current system time.
  Signals any expired event timer.

  @param  CheckEvent             Not used
  @param  Context                Not used

**/
VOID
EFIAPI
CoreCheckTimers (
  IN EFI_EVENT            CheckEvent,
  IN VOID                 *Context
  )
{
  UINT64                  SystemTime;
  IEVENT                  *Event;

  //
  // Check the timer database for expired timers
  //
  CoreAcquireLock (&mEfiTimerLock);
  SystemTime = CoreCurrentSystemTime ();

  while (!IsListEmpty (&mEfiTimerList)) {
    Event = CR (mEfiTimerList.ForwardLink, IEVENT, Timer.Link, EVENT_SIGNATURE);

    //
    // If this timer is not expired, then we're done
    //
    if (Event->Timer.TriggerTime > SystemTime) {
      break;
    }

    //
    // Remove this timer from the timer queue
    //

    RemoveEntryList (&Event->Timer.Link);
    Event->Timer.Link.ForwardLink = NULL;

    //
    // Signal it
    //
    CoreSignalEvent (Event);

    //
    // If this is a periodic timer, set it
    //
    if (Event->Timer.Period != 0) {
      //
      // Compute the timers new trigger time
      //
      Event->Timer.TriggerTime = Event->Timer.TriggerTime + Event->Timer.Period;

      //
      // If that's before now, then reset the timer to start from now
      //
      if (Event->Timer.TriggerTime <= SystemTime) {
        Event->Timer.TriggerTime = SystemTime;
        CoreSignalEvent (mEfiCheckTimerEvent);
      }

      //
      // Add the timer
      //
      CoreInsertEventTimer (Event);
    }
  }

  CoreReleaseLock (&mEfiTimerLock);
}


/**
  Initializes timer support.

**/
VOID
CoreInitializeTimer (
  VOID
  )
{
  EFI_STATUS  Status;

  Status = CoreCreateEventInternal (
             EVT_NOTIFY_SIGNAL,
             TPL_HIGH_LEVEL - 1,
             CoreCheckTimers,
             NULL,
             NULL,
             &mEfiCheckTimerEvent
             );
  ASSERT_EFI_ERROR (Status);
}


/**
  Called by the platform code to process a tick.

  @param  Duration               The number of 100ns elasped since the last call
                                 to TimerTick

**/
VOID
EFIAPI
CoreTimerTick (
  IN UINT64   Duration
  )
{
  IEVENT          *Event;

  //
  // Check runtiem flag in case there are ticks while exiting boot services
  //
  CoreAcquireLock (&mEfiSystemTimeLock);

  //
  // Update the system time
  //
  mEfiSystemTime += Duration;

  //
  // If the head of the list is expired, fire the timer event
  // to process it
  //
  if (!IsListEmpty (&mEfiTimerList)) {
    Event = CR (mEfiTimerList.ForwardLink, IEVENT, Timer.Link, EVENT_SIGNATURE);

    if (Event->Timer.TriggerTime <= mEfiSystemTime) {
      CoreSignalEvent (mEfiCheckTimerEvent);
    }
  }

  CoreReleaseLock (&mEfiSystemTimeLock);
}



/**
  Sets the type of timer and the trigger time for a timer event.

  @param  UserEvent              The timer event that is to be signaled at the
                                 specified time
  @param  Type                   The type of time that is specified in
                                 TriggerTime
  @param  TriggerTime            The number of 100ns units until the timer
                                 expires

  @retval EFI_SUCCESS            The event has been set to be signaled at the
                                 requested time
  @retval EFI_INVALID_PARAMETER  Event or Type is not valid

**/
EFI_STATUS
EFIAPI
CoreSetTimer (
  IN EFI_EVENT            UserEvent,
  IN EFI_TIMER_DELAY      Type,
  IN UINT64               TriggerTime
  )
{
  IEVENT      *Event;

  Event = UserEvent;

  if (Event == NULL) {
    return EFI_INVALID_PARAMETER;
  }

  if (Event->Signature != EVENT_SIGNATURE) {
    return EFI_INVALID_PARAMETER;
  }

  if ((UINT32)Type > TimerRelative  || (Event->Type & EVT_TIMER) == 0) {
    return EFI_INVALID_PARAMETER;
  }

  CoreAcquireLock (&mEfiTimerLock);

  //
  // If the timer is queued to the timer database, remove it
  //
  if (Event->Timer.Link.ForwardLink != NULL) {
    RemoveEntryList (&Event->Timer.Link);
    Event->Timer.Link.ForwardLink = NULL;
  }

  Event->Timer.TriggerTime = 0;
  Event->Timer.Period = 0;

  if (Type != TimerCancel) {

    if (Type == TimerPeriodic) {
      if (TriggerTime == 0) {
        gTimer->GetTimerPeriod (gTimer, &TriggerTime);
      }
      Event->Timer.Period = TriggerTime;
    }

    Event->Timer.TriggerTime = CoreCurrentSystemTime () + TriggerTime;
    CoreInsertEventTimer (Event);

    if (TriggerTime == 0) {
      CoreSignalEvent (mEfiCheckTimerEvent);
    }
  }

  CoreReleaseLock (&mEfiTimerLock);

  return EFI_SUCCESS;
}