MdeModulePkg/Core/Dxe/Event/Tpl.c

   1 /** @file
   2
   3   Task priority (TPL) function
   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 #include <DxeMain.h>
  17
  18
  19 /**
  20   Set Interrupt State.
  21
  22   @param  Enable  The state of enable or disable interrupt
  23
  24 **/
  25 STATIC
  26 VOID
  27 CoreSetInterruptState (
  28   IN BOOLEAN      Enable
  29   )
  30 {
  31   if (gCpu != NULL) {
  32     if (Enable) {
  33       gCpu->EnableInterrupt(gCpu);
  34     } else {
  35       gCpu->DisableInterrupt(gCpu);
  36     }
  37   }
  38 }
  39
  40 //
  41 // Return the highest set bit
  42 //
  43
  44 /**
  45   Return the highest set bit.
  46
  47   @param  Number  The value to check
  48
  49   @return Bit position of the highest set bit
  50
  51 **/
  52 UINTN
  53 CoreHighestSetBit (
  54   IN UINTN     Number
  55   )
  56 {
  57   UINTN   msb;
  58
  59   msb = 31;
  60   while ((msb > 0) && ((Number & (UINTN)(1 << msb)) == 0)) {
  61     msb--;
  62   }
  63
  64   return msb;
  65 }
  66
  67
  68
  69
  70 /**
  71   Raise the task priority level to the new level.
  72   High level is implemented by disabling processor interrupts.
  73
  74   @param  NewTpl  New task priority level
  75
  76   @return The previous task priority level
  77
  78 **/
  79 EFI_TPL
  80 EFIAPI
  81 CoreRaiseTpl (
  82   IN EFI_TPL      NewTpl
  83   )
  84 {
  85   EFI_TPL     OldTpl;
  86
  87   OldTpl = gEfiCurrentTpl;
  88   ASSERT (OldTpl <= NewTpl);
  89   ASSERT (VALID_TPL (NewTpl));
  90
  91   //
  92   // If raising to high level, disable interrupts
  93   //
  94   if (NewTpl >= TPL_HIGH_LEVEL  &&  OldTpl < TPL_HIGH_LEVEL) {
  95     CoreSetInterruptState (FALSE);
  96   }
  97
  98   //
  99   // Set the new value
 100   //
 101   gEfiCurrentTpl = NewTpl;
 102
 103   return OldTpl;
 104 }
 105
 106
 107
 108
 109 /**
 110   Lowers the task priority to the previous value.   If the new
 111   priority unmasks events at a higher priority, they are dispatched.
 112
 113   @param  NewTpl  New, lower, task priority
 114
 115 **/
 116 VOID
 117 EFIAPI
 118 CoreRestoreTpl (
 119   IN EFI_TPL NewTpl
 120   )
 121 {
 122   EFI_TPL     OldTpl;
 123
 124   OldTpl = gEfiCurrentTpl;
 125   ASSERT (NewTpl <= OldTpl);
 126   ASSERT (VALID_TPL (NewTpl));
 127
 128   //
 129   // If lowering below HIGH_LEVEL, make sure
 130   // interrupts are enabled
 131   //
 132
 133   if (OldTpl >= TPL_HIGH_LEVEL  &&  NewTpl < TPL_HIGH_LEVEL) {
 134     gEfiCurrentTpl = TPL_HIGH_LEVEL;
 135   }
 136
 137   //
 138   // Dispatch any pending events
 139   //
 140
 141   while ((-2 << NewTpl) & gEventPending) {
 142     gEfiCurrentTpl = CoreHighestSetBit (gEventPending);
 143     if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
 144       CoreSetInterruptState (TRUE);
 145     }
 146     CoreDispatchEventNotifies (gEfiCurrentTpl);
 147   }
 148
 149   //
 150   // Set the new value
 151   //
 152
 153   gEfiCurrentTpl = NewTpl;
 154
 155   //
 156   // If lowering below HIGH_LEVEL, make sure
 157   // interrupts are enabled
 158   //
 159   if (gEfiCurrentTpl < TPL_HIGH_LEVEL) {
 160     CoreSetInterruptState (TRUE);
 161   }
 162
 163 }