timer.c

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/*++

Copyright (c) 2004, Intel Corporation                                                         
All rights reserved. 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.             

Module Name:

  Timer.c

Abstract:

  NT Emulation Timer Architectural Protocol Driver as defined in DXE CIS

  This Timer module uses an NT Thread to simulate the timer-tick driven
  timer service.  In the future, the Thread creation should possibly be 
  abstracted by the CPU architectural protocol

--*/

#include "Timer.h"

//
// Pointer to the CPU Architectural Protocol instance
//
EFI_CPU_ARCH_PROTOCOL   *mCpu;

//
// The Timer Architectural Protocol that this driver produces
//
EFI_TIMER_ARCH_PROTOCOL mTimer = {
  WinNtTimerDriverRegisterHandler,
  WinNtTimerDriverSetTimerPeriod,
  WinNtTimerDriverGetTimerPeriod,
  WinNtTimerDriverGenerateSoftInterrupt
};

//
// Define a global that we can use to shut down the NT timer thread when
// the timer is canceled.
//
BOOLEAN                 mCancelTimerThread = FALSE;

//
// The notification function to call on every timer interrupt
//
EFI_TIMER_NOTIFY        mTimerNotifyFunction = NULL;

//
// The current period of the timer interrupt
//
UINT64                  mTimerPeriod;

//
// The thread handle for this driver
//
HANDLE                  mNtMainThreadHandle;

//
// The timer value from the last timer interrupt
//
UINT32                  mNtLastTick;

//
// Critical section used to update varibles shared between the main thread and
// the timer interrupt thread.
//
CRITICAL_SECTION        mNtCriticalSection;

//
// Worker Functions
//
UINT                    mMMTimerThreadID = 0;

VOID
CALLBACK
MMTimerThread (
  UINT  wTimerID,
  UINT  msg,
  DWORD dwUser,
  DWORD dw1,
  DWORD dw2
  )
/*++

Routine Description:

  TODO: Add function description

Arguments:

  wTimerID  - TODO: add argument description
  msg       - TODO: add argument description
  dwUser    - TODO: add argument description
  dw1       - TODO: add argument description
  dw2       - TODO: add argument description

Returns:

  TODO: add return values

--*/
{
  EFI_TPL           OriginalTPL;
  UINT32            CurrentTick;
  UINT32            Delta;
  EFI_TIMER_NOTIFY  CallbackFunction;
  BOOLEAN           InterruptState;

  if (!mCancelTimerThread) {
  
    //
    //  Suspend the main thread until we are done
    //

    gWinNt->SuspendThread (mNtMainThreadHandle);

    //
    // If the timer thread is being canceled, then bail immediately.
    // We check again here because there's a small window of time from when
    // this thread was kicked off and when we suspended the main thread above.
    //
    if (mCancelTimerThread) {
      gWinNt->ResumeThread (mNtMainThreadHandle);
      gWinNt->timeKillEvent (wTimerID);
      mMMTimerThreadID = 0;
      return ;
    }

    mCpu->GetInterruptState (mCpu, &InterruptState);
    while (!InterruptState) {
      //
      //  Resume the main thread
      //
      gWinNt->ResumeThread (mNtMainThreadHandle);

      //
      //  Wait for interrupts to be enabled.
      //
      mCpu->GetInterruptState (mCpu, &InterruptState);
      while (!InterruptState) {
        gWinNt->Sleep (0);
        mCpu->GetInterruptState (mCpu, &InterruptState);
      }
       
      //
      //  Suspend the main thread until we are done
      //
      gWinNt->SuspendThread (mNtMainThreadHandle);
      mCpu->GetInterruptState (mCpu, &InterruptState);
    }

    //
    //  Get the current system tick
    //
    CurrentTick = gWinNt->GetTickCount ();
    Delta       = CurrentTick - mNtLastTick;
    mNtLastTick = CurrentTick;

    //
    //  If delay was more then 1 second, ignore it (probably debugging case)
    //
    if (Delta < 1000) {

      OriginalTPL = gBS->RaiseTPL (EFI_TPL_HIGH_LEVEL);

      //
      //  Inform the firmware of an "timer interrupt".  The time
      //  expired since the last call is 10,000 times the number
      //  of ms.  (or 100ns units)
      //
      gWinNt->EnterCriticalSection (&mNtCriticalSection);
      CallbackFunction = mTimerNotifyFunction;
      gWinNt->LeaveCriticalSection (&mNtCriticalSection);

      //
      // Only invoke the callback function if a Non-NULL handler has been
      // registered. Assume all other handlers are legal.
      //
      if (CallbackFunction != NULL) {
        CallbackFunction ((UINT64) (Delta * 10000));
      }

      gBS->RestoreTPL (OriginalTPL);

    }

    //
    //  Resume the main thread
    //
    gWinNt->ResumeThread (mNtMainThreadHandle);
  } else {
    gWinNt->timeKillEvent (wTimerID);
    mMMTimerThreadID = 0;
  }

}

UINT
CreateNtTimer (
  VOID
  )
/*++

Routine Description:

   It is used to emulate a platform 
  timer-driver interrupt handler.  

Returns:

  Timer ID

--*/
// TODO: function comment is missing 'Arguments:'
{
  UINT32  SleepCount;

  //
  //  Set our thread priority higher than the "main" thread.
  //
  gWinNt->SetThreadPriority (
            gWinNt->GetCurrentThread (),
            THREAD_PRIORITY_HIGHEST
            );

  //
  //  Calc the appropriate interval
  //
  gWinNt->EnterCriticalSection (&mNtCriticalSection);
  SleepCount = (UINT32) (mTimerPeriod + 5000) / 10000;
  gWinNt->LeaveCriticalSection (&mNtCriticalSection);

  return gWinNt->timeSetEvent (
                  SleepCount,
                  0,
                  MMTimerThread,
                  (DWORD_PTR) NULL,
                  TIME_PERIODIC | TIME_KILL_SYNCHRONOUS | TIME_CALLBACK_FUNCTION
                  );

}

EFI_STATUS
EFIAPI
WinNtTimerDriverRegisterHandler (
  IN EFI_TIMER_ARCH_PROTOCOL           *This,
  IN EFI_TIMER_NOTIFY                  NotifyFunction
  )
/*++

Routine Description:

  This function registers the handler NotifyFunction so it is called every time 
  the timer interrupt fires.  It also passes the amount of time since the last 
  handler call to the NotifyFunction.  If NotifyFunction is NULL, then the 
  handler is unregistered.  If the handler is registered, then EFI_SUCCESS is 
  returned.  If the CPU does not support registering a timer interrupt handler, 
  then EFI_UNSUPPORTED is returned.  If an attempt is made to register a handler 
  when a handler is already registered, then EFI_ALREADY_STARTED is returned.  
  If an attempt is made to unregister a handler when a handler is not registered, 
  then EFI_INVALID_PARAMETER is returned.  If an error occurs attempting to 
  register the NotifyFunction with the timer interrupt, then EFI_DEVICE_ERROR 
  is returned.

Arguments:

  This           - The EFI_TIMER_ARCH_PROTOCOL instance.

  NotifyFunction - The function to call when a timer interrupt fires.  This 
                   function executes at TPL_HIGH_LEVEL.  The DXE Core will 
                   register a handler for the timer interrupt, so it can know 
                   how much time has passed.  This information is used to 
                   signal timer based events.  NULL will unregister the handler.

Returns: 

  EFI_SUCCESS           - The timer handler was registered.

  EFI_UNSUPPORTED       - The platform does not support timer interrupts.

  EFI_ALREADY_STARTED   - NotifyFunction is not NULL, and a handler is already 
                          registered.

  EFI_INVALID_PARAMETER - NotifyFunction is NULL, and a handler was not 
                          previously registered.

  EFI_DEVICE_ERROR      - The timer handler could not be registered.

--*/
{
  //
  // Check for invalid parameters
  //
  if (NotifyFunction == NULL && mTimerNotifyFunction == NULL) {
    return EFI_INVALID_PARAMETER;
  }