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   @par Revision Reference:
  16   Version 0.91B.
  17
  18 **/
  19
  20 #ifndef __ARCH_PROTOCOL_METRONOME_H__
  21 #define __ARCH_PROTOCOL_METRONOME_H__
  22
  23 //
  24 // Global ID for the Metronome Architectural Protocol
  25 //
  26 #define EFI_METRONOME_ARCH_PROTOCOL_GUID \
  27   { 0x26baccb2, 0x6f42, 0x11d4, {0xbc, 0xe7, 0x0, 0x80, 0xc7, 0x3c, 0x88, 0x81 } }
  28
  29 //
  30 // Declare forward reference for the Metronome Architectural Protocol
  31 //
  32 typedef struct _EFI_METRONOME_ARCH_PROTOCOL   EFI_METRONOME_ARCH_PROTOCOL;
  33
  34 /**
  35   The WaitForTick() function waits for the number of ticks specified by
  36   TickNumber from a known time source in the platform.  If TickNumber of
  37   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  38   between entry of this function and the first tick is between 0 and
  39   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  40   time has elapsed, wait for two ticks.  This function waits for a hardware
  41   event to determine when a tick occurs.  It is possible for interrupt
  42   processing, or exception processing to interrupt the execution of the
  43   WaitForTick() function.  Depending on the hardware source for the ticks, it
  44   is possible for a tick to be missed.  This function cannot guarantee that
  45   ticks will not be missed.  If a timeout occurs waiting for the specified
  46   number of ticks, then EFI_TIMEOUT is returned.
  47
  48   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  49   @param  TickNumber       Number of ticks to wait.
  50
  51   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  52                                 succeeded.
  53   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  54
  55 **/
  56 typedef
  57 EFI_STATUS
  58 (EFIAPI *EFI_METRONOME_WAIT_FOR_TICK) (
  59    IN EFI_METRONOME_ARCH_PROTOCOL   *This,
  60    IN UINT32                        TickNumber
  61   );
  62
  63 //
  64 //
  65
  66 /**
  67   Interface stucture for the Metronome Architectural Protocol.
  68
  69   @par Protocol Description:
  70   This protocol provides access to a known time source in the platform to the
  71   core.  The core uses this known time source to produce core services that
  72   require calibrated delays.
  73
  74   @param WaitForTick
  75   Waits for a specified number of ticks from a known time source
  76   in the platform.  The actual time passed between entry of this
  77   function and the first tick is between 0 and TickPeriod 100 nS
  78   units.  If you want to guarantee that at least TickPeriod time
  79   has elapsed, wait for two ticks.
  80
  81   @param TickPeriod
  82   The period of platform's known time source in 100 nS units.
  83   This value on any platform must be at least 10 uS, and must not
  84   exceed 200 uS.  The value in this field is a constant that must
  85   not be modified after the Metronome architectural protocol is
  86   installed.  All consumers must treat this as a read-only field.
  87
  88 **/
  89 struct _EFI_METRONOME_ARCH_PROTOCOL {
  90   EFI_METRONOME_WAIT_FOR_TICK  WaitForTick;
  91   UINT32                       TickPeriod;
  92 };
  93
  94 extern EFI_GUID gEfiMetronomeArchProtocolGuid;
  95
  96 #endif