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 EFI_STATUS
  24 EFIAPI
  25 CoreStall (
  26   IN UINTN            Microseconds
  27   )
  28 /*++
  29
  30 Routine Description:
  31
  32   Introduces a fine-grained stall.
  33
  34 Arguments:
  35
  36   Microseconds      The number of microseconds to stall execution
  37
  38 Returns:
  39
  40   EFI_SUCCESS            - Execution was stalled for at least the requested amount
  41                            of microseconds.
  42
  43   EFI_NOT_AVAILABLE_YET  - gMetronome is not available yet
  44
  45 --*/
  46 {
  47   UINT32  Counter;
  48   UINT32  Remainder;
  49
  50   if (gMetronome == NULL) {
  51     return EFI_NOT_AVAILABLE_YET;
  52   }
  53
  54   //
  55   // Calculate the number of ticks by dividing the number of microseconds by
  56   // the TickPeriod.
  57   // Calcullation is based on 100ns unit.
  58   //
  59   Counter = (UINT32) DivU64x32Remainder (
  60                        Microseconds * 10,
  61                        gMetronome->TickPeriod,
  62                        &Remainder
  63                        );
  64
  65   //
  66   // Call WaitForTick for Counter + 1 ticks to try to guarantee Counter tick
  67   // periods, thus attempting to ensure Microseconds of stall time.
  68   //
  69   if (Remainder != 0) {
  70     Counter++;
  71   }
  72
  73   gMetronome->WaitForTick (gMetronome, Counter);
  74
  75   return EFI_SUCCESS;
  76 }