MdePkg/Include/Protocol/Metronome.h

   1 /** @file
   2   Metronome Architectural Protocol as defined in PI SPEC VOLUME 2 DXE
   3
   4   This code abstracts the DXE core to provide delay services.
   5
   6   Copyright (c) 2006 - 2018, Intel Corporation. All rights reserved.<BR>
   7   SPDX-License-Identifier: BSD-2-Clause-Patent
   8
   9 **/
  10
  11 #ifndef __ARCH_PROTOCOL_METRONOME_H__
  12 #define __ARCH_PROTOCOL_METRONOME_H__
  13
  14 ///
  15 /// Global ID for the Metronome Architectural Protocol
  16 ///
  17 #define EFI_METRONOME_ARCH_PROTOCOL_GUID \
  18   { 0x26baccb2, 0x6f42, 0x11d4, {0xbc, 0xe7, 0x0, 0x80, 0xc7, 0x3c, 0x88, 0x81 } }
  19
  20 ///
  21 /// Declare forward reference for the Metronome Architectural Protocol
  22 ///
  23 typedef struct _EFI_METRONOME_ARCH_PROTOCOL   EFI_METRONOME_ARCH_PROTOCOL;
  24
  25 /**
  26   The WaitForTick() function waits for the number of ticks specified by
  27   TickNumber from a known time source in the platform.  If TickNumber of
  28   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  29   between entry of this function and the first tick is between 0 and
  30   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  31   time has elapsed, wait for two ticks.  This function waits for a hardware
  32   event to determine when a tick occurs.  It is possible for interrupt
  33   processing, or exception processing to interrupt the execution of the
  34   WaitForTick() function.  Depending on the hardware source for the ticks, it
  35   is possible for a tick to be missed.  This function cannot guarantee that
  36   ticks will not be missed.  If a timeout occurs waiting for the specified
  37   number of ticks, then EFI_TIMEOUT is returned.
  38
  39   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  40   @param  TickNumber       Number of ticks to wait.
  41
  42   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  43                                 succeeded.
  44   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  45
  46 **/
  47 typedef
  48 EFI_STATUS
  49 (EFIAPI *EFI_METRONOME_WAIT_FOR_TICK)(
  50    IN EFI_METRONOME_ARCH_PROTOCOL   *This,
  51    IN UINT32                        TickNumber
  52   );
  53
  54 ///
  55 /// This protocol provides access to a known time source in the platform to the
  56 /// core.  The core uses this known time source to produce core services that
  57 /// require calibrated delays.
  58 ///
  59 struct _EFI_METRONOME_ARCH_PROTOCOL {
  60   EFI_METRONOME_WAIT_FOR_TICK  WaitForTick;
  61
  62   ///
  63   /// The period of platform's known time source in 100 nS units.
  64   /// This value on any platform must be at least 10 uS, and must not
  65   /// exceed 200 uS.  The value in this field is a constant that must
  66   /// not be modified after the Metronome architectural protocol is
  67   /// installed.  All consumers must treat this as a read-only field.
  68   ///
  69   UINT32                       TickPeriod;
  70 };
  71
  72 extern EFI_GUID gEfiMetronomeArchProtocolGuid;
  73
  74 #endif