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 /**
  59   The WaitForTick() function waits for the number of ticks specified by
  60   TickNumber from a known time source in the platform.  If TickNumber of
  61   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  62   between entry of this function and the first tick is between 0 and
  63   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  64   time has elapsed, wait for two ticks.  This function waits for a hardware
  65   event to determine when a tick occurs.  It is possible for interrupt
  66   processing, or exception processing to interrupt the execution of the
  67   WaitForTick() function.  Depending on the hardware source for the ticks, it
  68   is possible for a tick to be missed.  This function cannot guarantee that
  69   ticks will not be missed.  If a timeout occurs waiting for the specified
  70   number of ticks, then EFI_TIMEOUT is returned.
  71
  72   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  73   @param  TickNumber       Number of ticks to wait.
  74
  75   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  76                                 succeeded.
  77   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  78
  79 **/
  80 EFI_STATUS
  81 EFIAPI
  82 WaitForTick (
  83   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  84   IN UINT32                       TickNumber
  85   )
  86 {
  87   //
  88   // Compute how long to stall the CPU.
  89   // gMetronome.TickPeriod is in 100 ns units so it needs to be divided by 10
  90   // to get it in microseconds units.
  91   //
  92   MicroSecondDelay (TickNumber * gMetronome.TickPeriod / 10);
  93   return EFI_SUCCESS;
  94 }
  95
  96
  97 EFI_HANDLE  gMetronomeHandle = NULL;
  98
  99
 100
 101 /**
 102   Initialize the state information for the CPU Architectural Protocol
 103
 104   @param  ImageHandle   of the loaded driver
 105   @param  SystemTable   Pointer to the System Table
 106
 107   @retval EFI_SUCCESS           Protocol registered
 108   @retval EFI_OUT_OF_RESOURCES  Cannot allocate protocol data structure
 109   @retval EFI_DEVICE_ERROR      Hardware problems
 110
 111 **/
 112 EFI_STATUS
 113 EFIAPI
 114 MetronomeInitialize (
 115   IN EFI_HANDLE         ImageHandle,
 116   IN EFI_SYSTEM_TABLE   *SystemTable
 117   )
 118 {
 119   EFI_STATUS  Status;
 120
 121   //
 122   // Do any hardware init required to make WaitForTick () to work here.
 123   //
 124
 125   Status = gBS->InstallMultipleProtocolInterfaces (
 126                   &gMetronomeHandle,
 127                   &gEfiMetronomeArchProtocolGuid,   &gMetronome,
 128                   NULL
 129                   );
 130   ASSERT_EFI_ERROR (Status);
 131
 132   return Status;
 133 }
 134