EdkModulePkg/Core/Dxe/Misc/Stall.c

   1 /*++
   2
   3 Copyright (c) 2006, Intel Corporation
   4 All rights reserved. This program and the accompanying materials
   5 are licensed and made available under the terms and conditions of the BSD License
   6 which accompanies this distribution.  The full text of the license may be found at
   7 http://opensource.org/licenses/bsd-license.php
   8
   9 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11
  12 Module Name:
  13
  14     Stall.c
  15
  16 Abstract:
  17
  18     Tiano Miscellaneous Services Stall service implementation
  19
  20 --*/
  21
  22 //
  23 // Include statements
  24 //
  25
  26 #include <DxeMain.h>
  27
  28
  29 EFI_STATUS
  30 EFIAPI
  31 CoreStall (
  32   IN UINTN            Microseconds
  33   )
  34 /*++
  35
  36 Routine Description:
  37
  38   Introduces a fine-grained stall.
  39
  40 Arguments:
  41
  42   Microseconds      The number of microseconds to stall execution
  43
  44 Returns:
  45
  46   EFI_SUCCESS            - Execution was stalled for at least the requested amount
  47                            of microseconds.
  48
  49   EFI_NOT_AVAILABLE_YET  - gMetronome is not available yet
  50
  51 --*/
  52 {
  53   UINT32  Counter;
  54   UINT32  Remainder;
  55
  56   if (gMetronome == NULL) {
  57     return EFI_NOT_AVAILABLE_YET;
  58   }
  59
  60   //
  61   // Calculate the number of ticks by dividing the number of microseconds by
  62   // the TickPeriod.
  63   // Calcullation is based on 100ns unit.
  64   //
  65   Counter = (UINT32) DivU64x32Remainder (
  66                        Microseconds * 10,
  67                        gMetronome->TickPeriod,
  68                        &Remainder
  69                        );
  70
  71   //
  72   // Call WaitForTick for Counter + 1 ticks to try to guarantee Counter tick
  73   // periods, thus attempting to ensure Microseconds of stall time.
  74   //
  75   if (Remainder != 0) {
  76     Counter++;
  77   }
  78
  79   gMetronome->WaitForTick (gMetronome, Counter);
  80
  81   return EFI_SUCCESS;
  82 }