MdeModulePkg/Core/Dxe/Misc/Stall.c

   1 /** @file
   2   UEFI Miscellaneous boot Services Stall service implementation
   3
   4 Copyright (c) 2006 - 2008, Intel Corporation. <BR>
   5 All rights reserved. This program and the accompanying materials
   6 are licensed and made available under the terms and conditions of the BSD License
   7 which accompanies this distribution.  The full text of the license may be found at
   8 http://opensource.org/licenses/bsd-license.php
   9
  10 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 //
  16 // Include statements
  17 //
  18
  19 #include <DxeMain.h>
  20
  21
  22
  23 /**
  24   Introduces a fine-grained stall.
  25
  26   @param  Microseconds           The number of microseconds to stall execution.
  27
  28   @retval EFI_SUCCESS            Execution was stalled for at least the requested
  29                                  amount of microseconds.
  30   @retval EFI_NOT_AVAILABLE_YET  gMetronome is not available yet
  31
  32 **/
  33 EFI_STATUS
  34 EFIAPI
  35 CoreStall (
  36   IN UINTN            Microseconds
  37   )
  38 {
  39   UINT32  Counter;
  40   UINT32  Remainder;
  41
  42   if (gMetronome == NULL) {
  43     return EFI_NOT_AVAILABLE_YET;
  44   }
  45
  46   //
  47   // Calculate the number of ticks by dividing the number of microseconds by
  48   // the TickPeriod.
  49   // Calcullation is based on 100ns unit.
  50   //
  51   Counter = (UINT32) DivU64x32Remainder (
  52                        Microseconds * 10,
  53                        gMetronome->TickPeriod,
  54                        &Remainder
  55                        );
  56
  57   //
  58   // Call WaitForTick for Counter + 1 ticks to try to guarantee Counter tick
  59   // periods, thus attempting to ensure Microseconds of stall time.
  60   //
  61   if (Remainder != 0) {
  62     Counter++;
  63   }
  64
  65   gMetronome->WaitForTick (gMetronome, Counter);
  66
  67   return EFI_SUCCESS;
  68 }