EmbeddedPkg/MetronomeDxe/Metronome.c

   1 /** @file
   2
   3   Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
   4   Copyright (c) 2013, ARM Ltd. All rights reserved.
   5
   6   SPDX-License-Identifier: BSD-2-Clause-Patent
   7
   8 **/
   9
  10 #include <PiDxe.h>
  11
  12 #include <Library/BaseLib.h>
  13 #include <Library/DebugLib.h>
  14 #include <Library/BaseMemoryLib.h>
  15 #include <Library/UefiBootServicesTableLib.h>
  16 #include <Library/UefiLib.h>
  17 #include <Library/PcdLib.h>
  18 #include <Library/TimerLib.h>
  19
  20 #include <Protocol/Metronome.h>
  21
  22 EFI_STATUS
  23 EFIAPI
  24 WaitForTick (
  25   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  26   IN UINT32                       TickNumber
  27   );
  28
  29 /**
  30   Interface structure for the Metronome Architectural Protocol.
  31
  32   @par Protocol Description:
  33   This protocol provides access to a known time source in the platform to the
  34   core.  The core uses this known time source to produce core services that
  35   require calibrated delays.
  36
  37   @param WaitForTick
  38   Waits for a specified number of ticks from a known time source
  39   in the platform.  The actual time passed between entry of this
  40   function and the first tick is between 0 and TickPeriod 100 nS
  41   units.  If you want to guarantee that at least TickPeriod time
  42   has elapsed, wait for two ticks.
  43
  44   @param TickPeriod
  45   The period of platform's known time source in 100 nS units.
  46   This value on any platform must be at least 10 uS, and must not
  47   exceed 200 uS.  The value in this field is a constant that must
  48   not be modified after the Metronome architectural protocol is
  49   installed.  All consumers must treat this as a read-only field.
  50
  51 **/
  52 EFI_METRONOME_ARCH_PROTOCOL  gMetronome = {
  53   WaitForTick,
  54   FixedPcdGet32 (PcdMetronomeTickPeriod)
  55 };
  56
  57 /**
  58   The WaitForTick() function waits for the number of ticks specified by
  59   TickNumber from a known time source in the platform.  If TickNumber of
  60   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  61   between entry of this function and the first tick is between 0 and
  62   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  63   time has elapsed, wait for two ticks.  This function waits for a hardware
  64   event to determine when a tick occurs.  It is possible for interrupt
  65   processing, or exception processing to interrupt the execution of the
  66   WaitForTick() function.  Depending on the hardware source for the ticks, it
  67   is possible for a tick to be missed.  This function cannot guarantee that
  68   ticks will not be missed.  If a timeout occurs waiting for the specified
  69   number of ticks, then EFI_TIMEOUT is returned.
  70
  71   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  72   @param  TickNumber       Number of ticks to wait.
  73
  74   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  75                                 succeeded.
  76   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  77
  78 **/
  79 EFI_STATUS
  80 EFIAPI
  81 WaitForTick (
  82   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  83   IN UINT32                       TickNumber
  84   )
  85 {
  86   //
  87   // Compute how long to stall the CPU.
  88   // gMetronome.TickPeriod is in 100 ns units so it needs to be divided by 10
  89   // to get it in microseconds units.
  90   //
  91   MicroSecondDelay (TickNumber * gMetronome.TickPeriod / 10);
  92   return EFI_SUCCESS;
  93 }
  94
  95 EFI_HANDLE  gMetronomeHandle = NULL;
  96
  97 /**
  98   Initialize the state information for the CPU Architectural Protocol
  99
 100   @param  ImageHandle   of the loaded driver
 101   @param  SystemTable   Pointer to the System Table
 102
 103   @retval EFI_SUCCESS           Protocol registered
 104   @retval EFI_OUT_OF_RESOURCES  Cannot allocate protocol data structure
 105   @retval EFI_DEVICE_ERROR      Hardware problems
 106
 107 **/
 108 EFI_STATUS
 109 EFIAPI
 110 MetronomeInitialize (
 111   IN EFI_HANDLE        ImageHandle,
 112   IN EFI_SYSTEM_TABLE  *SystemTable
 113   )
 114 {
 115   EFI_STATUS  Status;
 116
 117   //
 118   // Do any hardware init required to make WaitForTick () to work here.
 119   //
 120
 121   Status = gBS->InstallMultipleProtocolInterfaces (
 122                   &gMetronomeHandle,
 123                   &gEfiMetronomeArchProtocolGuid,
 124                   &gMetronome,
 125                   NULL
 126                   );
 127   ASSERT_EFI_ERROR (Status);
 128
 129   return Status;
 130 }