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   This program and the accompanying materials
   7   are licensed and made available under the terms and conditions of the BSD License
   8   which accompanies this distribution.  The full text of the license may be found at
   9   http://opensource.org/licenses/bsd-license.php
  10
  11   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  12   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  13
  14 **/
  15
  16 #include <PiDxe.h>
  17
  18 #include <Library/BaseLib.h>
  19 #include <Library/DebugLib.h>
  20 #include <Library/BaseMemoryLib.h>
  21 #include <Library/UefiBootServicesTableLib.h>
  22 #include <Library/UefiLib.h>
  23 #include <Library/PcdLib.h>
  24 #include <Library/TimerLib.h>
  25
  26 #include <Protocol/Metronome.h>
  27
  28 EFI_STATUS
  29 EFIAPI
  30 WaitForTick (
  31   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  32   IN UINT32                       TickNumber
  33   );
  34
  35 /**
  36   Interface structure for the Metronome Architectural Protocol.
  37
  38   @par Protocol Description:
  39   This protocol provides access to a known time source in the platform to the
  40   core.  The core uses this known time source to produce core services that
  41   require calibrated delays.
  42
  43   @param WaitForTick
  44   Waits for a specified number of ticks from a known time source
  45   in the platform.  The actual time passed between entry of this
  46   function and the first tick is between 0 and TickPeriod 100 nS
  47   units.  If you want to guarantee that at least TickPeriod time
  48   has elapsed, wait for two ticks.
  49
  50   @param TickPeriod
  51   The period of platform's known time source in 100 nS units.
  52   This value on any platform must be at least 10 uS, and must not
  53   exceed 200 uS.  The value in this field is a constant that must
  54   not be modified after the Metronome architectural protocol is
  55   installed.  All consumers must treat this as a read-only field.
  56
  57 **/
  58 EFI_METRONOME_ARCH_PROTOCOL gMetronome = {
  59   WaitForTick,
  60   FixedPcdGet32 (PcdMetronomeTickPeriod)
  61 };
  62
  63
  64 /**
  65   The WaitForTick() function waits for the number of ticks specified by
  66   TickNumber from a known time source in the platform.  If TickNumber of
  67   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  68   between entry of this function and the first tick is between 0 and
  69   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  70   time has elapsed, wait for two ticks.  This function waits for a hardware
  71   event to determine when a tick occurs.  It is possible for interrupt
  72   processing, or exception processing to interrupt the execution of the
  73   WaitForTick() function.  Depending on the hardware source for the ticks, it
  74   is possible for a tick to be missed.  This function cannot guarantee that
  75   ticks will not be missed.  If a timeout occurs waiting for the specified
  76   number of ticks, then EFI_TIMEOUT is returned.
  77
  78   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  79   @param  TickNumber       Number of ticks to wait.
  80
  81   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  82                                 succeeded.
  83   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  84
  85 **/
  86 EFI_STATUS
  87 EFIAPI
  88 WaitForTick (
  89   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  90   IN UINT32                       TickNumber
  91   )
  92 {
  93   //
  94   // Compute how long to stall the CPU.
  95   // gMetronome.TickPeriod is in 100 ns units so it needs to be divided by 10
  96   // to get it in microseconds units.
  97   //
  98   MicroSecondDelay (TickNumber * gMetronome.TickPeriod / 10);
  99   return EFI_SUCCESS;
 100 }
 101
 102
 103 EFI_HANDLE  gMetronomeHandle = NULL;
 104
 105
 106
 107 /**
 108   Initialize the state information for the CPU Architectural Protocol
 109
 110   @param  ImageHandle   of the loaded driver
 111   @param  SystemTable   Pointer to the System Table
 112
 113   @retval EFI_SUCCESS           Protocol registered
 114   @retval EFI_OUT_OF_RESOURCES  Cannot allocate protocol data structure
 115   @retval EFI_DEVICE_ERROR      Hardware problems
 116
 117 **/
 118 EFI_STATUS
 119 MetronomeInitialize (
 120   IN EFI_HANDLE         ImageHandle,
 121   IN EFI_SYSTEM_TABLE   *SystemTable
 122   )
 123 {
 124   EFI_STATUS  Status;
 125
 126   //
 127   // Do any hardware init required to make WaitForTick () to work here.
 128   //
 129
 130   Status = gBS->InstallMultipleProtocolInterfaces (
 131                   &gMetronomeHandle,
 132                   &gEfiMetronomeArchProtocolGuid,   &gMetronome,
 133                   NULL
 134                   );
 135   ASSERT_EFI_ERROR (Status);
 136
 137   return Status;
 138 }
 139