MdePkg/Include/Protocol/Metronome.h

   1 /** @file
   2   Metronome Architectural Protocol as defined in DXE CIS
   3
   4   This code abstracts the DXE core to provide delay services.
   5
   6   Copyright (c) 2006, Intel Corporation
   7   All rights reserved. This program and the accompanying materials
   8   are licensed and made available under the terms and conditions of the BSD License
   9   which accompanies this distribution.  The full text of the license may be found at
  10   http://opensource.org/licenses/bsd-license.php
  11
  12   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  13   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  14
  15   Module Name:  Metronome.h
  16
  17   @par Revision Reference:
  18   Version 0.91B.
  19
  20 **/
  21
  22 #ifndef __ARCH_PROTOCOL_METRONOME_H__
  23 #define __ARCH_PROTOCOL_METRONOME_H__
  24
  25 //
  26 // Global ID for the Metronome Architectural Protocol
  27 //
  28 #define EFI_METRONOME_ARCH_PROTOCOL_GUID \
  29   { 0x26baccb2, 0x6f42, 0x11d4, {0xbc, 0xe7, 0x0, 0x80, 0xc7, 0x3c, 0x88, 0x81 } }
  30
  31 //
  32 // Declare forward reference for the Metronome Architectural Protocol
  33 //
  34 typedef struct _EFI_METRONOME_ARCH_PROTOCOL   EFI_METRONOME_ARCH_PROTOCOL;
  35
  36 /**
  37   The WaitForTick() function waits for the number of ticks specified by
  38   TickNumber from a known time source in the platform.  If TickNumber of
  39   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  40   between entry of this function and the first tick is between 0 and
  41   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  42   time has elapsed, wait for two ticks.  This function waits for a hardware
  43   event to determine when a tick occurs.  It is possible for interrupt
  44   processing, or exception processing to interrupt the execution of the
  45   WaitForTick() function.  Depending on the hardware source for the ticks, it
  46   is possible for a tick to be missed.  This function cannot guarantee that
  47   ticks will not be missed.  If a timeout occurs waiting for the specified
  48   number of ticks, then EFI_TIMEOUT is returned.
  49
  50   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  51   @param  TickNumber       Number of ticks to wait.
  52
  53   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  54                                 succeeded.
  55   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  56
  57 **/
  58 typedef
  59 EFI_STATUS
  60 (EFIAPI *EFI_METRONOME_WAIT_FOR_TICK) (
  61    IN EFI_METRONOME_ARCH_PROTOCOL   *This,
  62    IN UINT32                        TickNumber
  63   );
  64
  65 //
  66 //
  67
  68 /**
  69   Interface stucture for the Metronome Architectural Protocol.
  70
  71   @par Protocol Description:
  72   This protocol provides access to a known time source in the platform to the
  73   core.  The core uses this known time source to produce core services that
  74   require calibrated delays.
  75
  76   @param WaitForTick
  77   Waits for a specified number of ticks from a known time source
  78   in the platform.  The actual time passed between entry of this
  79   function and the first tick is between 0 and TickPeriod 100 nS
  80   units.  If you want to guarantee that at least TickPeriod time
  81   has elapsed, wait for two ticks.
  82
  83   @param TickPeriod
  84   The period of platform's known time source in 100 nS units.
  85   This value on any platform must be at least 10 uS, and must not
  86   exceed 200 uS.  The value in this field is a constant that must
  87   not be modified after the Metronome architectural protocol is
  88   installed.  All consumers must treat this as a read-only field.
  89
  90 **/
  91 struct _EFI_METRONOME_ARCH_PROTOCOL {
  92   EFI_METRONOME_WAIT_FOR_TICK  WaitForTick;
  93   UINT32                       TickPeriod;
  94 };
  95
  96 extern EFI_GUID gEfiMetronomeArchProtocolGuid;
  97
  98 #endif