EmbeddedPkg/MetronomeDxe/Metronome.c

   1 /** @file
   2
   3   Copyright (c) 2008-2009, Apple Inc. All rights reserved.
   4
   5   All rights reserved. This program and the accompanying materials
   6   are licensed and made available under the terms and conditions of the BSD License
   7   which accompanies this distribution.  The full text of the license may be found at
   8   http://opensource.org/licenses/bsd-license.php
   9
  10   THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  11   WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  12
  13 **/
  14
  15 #include <PiDxe.h>
  16
  17 #include <Library/BaseLib.h>
  18 #include <Library/DebugLib.h>
  19 #include <Library/BaseMemoryLib.h>
  20 #include <Library/UefiBootServicesTableLib.h>
  21 #include <Library/UefiLib.h>
  22 #include <Library/PcdLib.h>
  23 #include <Library/TimerLib.h>
  24
  25 #include <Protocol/Metronome.h>
  26
  27
  28
  29 /**
  30   The WaitForTick() function waits for the number of ticks specified by
  31   TickNumber from a known time source in the platform.  If TickNumber of
  32   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  33   between entry of this function and the first tick is between 0 and
  34   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  35   time has elapsed, wait for two ticks.  This function waits for a hardware
  36   event to determine when a tick occurs.  It is possible for interrupt
  37   processing, or exception processing to interrupt the execution of the
  38   WaitForTick() function.  Depending on the hardware source for the ticks, it
  39   is possible for a tick to be missed.  This function cannot guarantee that
  40   ticks will not be missed.  If a timeout occurs waiting for the specified
  41   number of ticks, then EFI_TIMEOUT is returned.
  42
  43   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  44   @param  TickNumber       Number of ticks to wait.
  45
  46   @retval EFI_SUCCESS           The wait for the number of ticks specified by TickNumber
  47                                 succeeded.
  48   @retval EFI_TIMEOUT           A timeout occurred waiting for the specified number of ticks.
  49
  50 **/
  51 EFI_STATUS
  52 EFIAPI
  53 WaitForTick (
  54   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  55   IN UINT32                       TickNumber
  56   )
  57 {
  58   //
  59   // Fill me in
  60   //
  61   MicroSecondDelay (10 * TickNumber);
  62   return EFI_UNSUPPORTED;
  63 }
  64
  65
  66
  67 /**
  68   Interface stucture for the Metronome Architectural Protocol.
  69
  70   @par Protocol Description:
  71   This protocol provides access to a known time source in the platform to the
  72   core.  The core uses this known time source to produce core services that
  73   require calibrated delays.
  74
  75   @param WaitForTick
  76   Waits for a specified number of ticks from a known time source
  77   in the platform.  The actual time passed between entry of this
  78   function and the first tick is between 0 and TickPeriod 100 nS
  79   units.  If you want to guarantee that at least TickPeriod time
  80   has elapsed, wait for two ticks.
  81
  82   @param TickPeriod
  83   The period of platform's known time source in 100 nS units.
  84   This value on any platform must be at least 10 uS, and must not
  85   exceed 200 uS.  The value in this field is a constant that must
  86   not be modified after the Metronome architectural protocol is
  87   installed.  All consumers must treat this as a read-only field.
  88
  89 **/
  90 EFI_METRONOME_ARCH_PROTOCOL gMetronome = {
  91   WaitForTick,
  92   100
  93 };
  94
  95
  96 EFI_HANDLE  gMetronomeHandle = NULL;
  97
  98
  99
 100 /**
 101   Initialize the state information for the CPU Architectural Protocol
 102
 103   @param  ImageHandle   of the loaded driver
 104   @param  SystemTable   Pointer to the System Table
 105
 106   @retval EFI_SUCCESS           Protocol registered
 107   @retval EFI_OUT_OF_RESOURCES  Cannot allocate protocol data structure
 108   @retval EFI_DEVICE_ERROR      Hardware problems
 109
 110 **/
 111 EFI_STATUS
 112 MetronomeInitialize (
 113   IN EFI_HANDLE         ImageHandle,
 114   IN EFI_SYSTEM_TABLE   *SystemTable
 115   )
 116 {
 117   EFI_STATUS  Status;
 118
 119   //
 120   // Do any hardware init required to make WaitForTick () to work here.
 121   //
 122
 123   Status = gBS->InstallMultipleProtocolInterfaces (
 124                   &gMetronomeHandle,
 125                   &gEfiMetronomeArchProtocolGuid,   &gMetronome,
 126                   NULL
 127                   );
 128   ASSERT_EFI_ERROR (Status);
 129
 130   return Status;
 131 }
 132