MdeModulePkg/Core/Dxe/Misc/Stall.c

   1 /** @file
   2
   3   UEFI Miscellaneous boot Services Stall service implementation
   4
   5 Copyright (c) 2006 - 2008, Intel Corporation
   6 All rights reserved. This program and the accompanying materials
   7 are licensed and made available under the terms and conditions of the BSD License
   8 which accompanies this distribution.  The full text of the license may be found at
   9 http://opensource.org/licenses/bsd-license.php
  10
  11 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 //
  17 // Include statements
  18 //
  19
  20 #include <DxeMain.h>
  21
  22
  23
  24 /**
  25   Introduces a fine-grained stall.
  26
  27   @param  Microseconds           The number of microseconds to stall execution.
  28
  29   @retval EFI_SUCCESS            Execution was stalled for at least the requested
  30                                  amount of microseconds.
  31   @retval EFI_NOT_AVAILABLE_YET  gMetronome is not available yet
  32
  33 **/
  34 EFI_STATUS
  35 EFIAPI
  36 CoreStall (
  37   IN UINTN            Microseconds
  38   )
  39 {
  40   UINT32  Counter;
  41   UINT32  Remainder;
  42
  43   if (gMetronome == NULL) {
  44     return EFI_NOT_AVAILABLE_YET;
  45   }
  46
  47   //
  48   // Calculate the number of ticks by dividing the number of microseconds by
  49   // the TickPeriod.
  50   // Calcullation is based on 100ns unit.
  51   //
  52   Counter = (UINT32) DivU64x32Remainder (
  53                        Microseconds * 10,
  54                        gMetronome->TickPeriod,
  55                        &Remainder
  56                        );
  57
  58   //
  59   // Call WaitForTick for Counter + 1 ticks to try to guarantee Counter tick
  60   // periods, thus attempting to ensure Microseconds of stall time.
  61   //
  62   if (Remainder != 0) {
  63     Counter++;
  64   }
  65
  66   gMetronome->WaitForTick (gMetronome, Counter);
  67
  68   return EFI_SUCCESS;
  69 }