audk/MdeModulePkg/Core/Dxe/Misc/Stall.c

/** @file
  UEFI Miscellaneous boot Services Stall service implementation

Copyright (c) 2006 - 2008, Intel Corporation. <BR>
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.

**/

//
// Include statements
//

#include "DxeMain.h"



/**
  Introduces a fine-grained stall.

  @param  Microseconds           The number of microseconds to stall execution.

  @retval EFI_SUCCESS            Execution was stalled for at least the requested
                                 amount of microseconds.
  @retval EFI_NOT_AVAILABLE_YET  gMetronome is not available yet

**/
EFI_STATUS
EFIAPI
CoreStall (
  IN UINTN            Microseconds
  )
{
  UINT32  Counter;
  UINT32  Remainder;

  if (gMetronome == NULL) {
    return EFI_NOT_AVAILABLE_YET;
  }

  //
  // Calculate the number of ticks by dividing the number of microseconds by
  // the TickPeriod.
  // Calcullation is based on 100ns unit.
  //
  Counter = (UINT32) DivU64x32Remainder (
                       Microseconds * 10,
                       gMetronome->TickPeriod,
                       &Remainder
                       );

  //
  // Call WaitForTick for Counter + 1 ticks to try to guarantee Counter tick
  // periods, thus attempting to ensure Microseconds of stall time.
  //
  if (Remainder != 0) {
    Counter++;
  }

  gMetronome->WaitForTick (gMetronome, Counter);

  return EFI_SUCCESS;
}