EmbeddedPkg/MetronomeDxe/Metronome.c

   1 /** @file
   2
   3   Copyright (c) 2008 - 2009, Apple Inc. All rights reserved.<BR>
   4   Copyright (c) 2012, 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
  29
  30 /**
  31   The WaitForTick() function waits for the number of ticks specified by
  32   TickNumber from a known time source in the platform.  If TickNumber of
  33   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  34   between entry of this function and the first tick is between 0 and
  35   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  36   time has elapsed, wait for two ticks.  This function waits for a hardware
  37   event to determine when a tick occurs.  It is possible for interrupt
  38   processing, or exception processing to interrupt the execution of the
  39   WaitForTick() function.  Depending on the hardware source for the ticks, it
  40   is possible for a tick to be missed.  This function cannot guarantee that
  41   ticks will not be missed.  If a timeout occurs waiting for the specified
  42   number of ticks, then EFI_TIMEOUT is returned.
  43
  44   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  45   @param  TickNumber       Number of ticks to wait.
  46
  47   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  48                                 succeeded.
  49   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  50
  51 **/
  52 EFI_STATUS
  53 EFIAPI
  54 WaitForTick (
  55   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  56   IN UINT32                       TickNumber
  57   )
  58 {
  59   //
  60   // Fill me in
  61   //
  62   MicroSecondDelay (10 * TickNumber);
  63   return EFI_UNSUPPORTED;
  64 }
  65
  66
  67
  68 /**
  69   Interface structure for the Metronome Architectural Protocol.
  70
  71   @par Protocol Description:
  72   This protocol provides access to a known time source in the platform to the
  73   core.  The core uses this known time source to produce core services that
  74   require calibrated delays.
  75
  76   @param WaitForTick
  77   Waits for a specified number of ticks from a known time source
  78   in the platform.  The actual time passed between entry of this
  79   function and the first tick is between 0 and TickPeriod 100 nS
  80   units.  If you want to guarantee that at least TickPeriod time
  81   has elapsed, wait for two ticks.
  82
  83   @param TickPeriod
  84   The period of platform's known time source in 100 nS units.
  85   This value on any platform must be at least 10 uS, and must not
  86   exceed 200 uS.  The value in this field is a constant that must
  87   not be modified after the Metronome architectural protocol is
  88   installed.  All consumers must treat this as a read-only field.
  89
  90 **/
  91 EFI_METRONOME_ARCH_PROTOCOL gMetronome = {
  92   WaitForTick,
  93   FixedPcdGet32 (PcdMetronomeTickPeriod)
  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 MetronomeInitialize (
 114   IN EFI_HANDLE         ImageHandle,
 115   IN EFI_SYSTEM_TABLE   *SystemTable
 116   )
 117 {
 118   EFI_STATUS  Status;
 119
 120   //
 121   // Do any hardware init required to make WaitForTick () to work here.
 122   //
 123
 124   Status = gBS->InstallMultipleProtocolInterfaces (
 125                   &gMetronomeHandle,
 126                   &gEfiMetronomeArchProtocolGuid,   &gMetronome,
 127                   NULL
 128                   );
 129   ASSERT_EFI_ERROR (Status);
 130
 131   return Status;
 132 }
 133