MdeModulePkg/Universal/Metronome/Metronome.c

   1 /*++
   2
   3 Copyright (c) 2005, Intel Corporation
   4 All rights reserved. This program and the accompanying materials
   5 are licensed and made available under the terms and conditions of the BSD License
   6 which accompanies this distribution.  The full text of the license may be found at
   7 http://opensource.org/licenses/bsd-license.php
   8
   9 THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
  10 WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
  11
  12 Module Name:
  13
  14   Metronome.c
  15
  16 Abstract:
  17
  18   This is a generic implementation of the Metronome Architectural Protocol that
  19   layers on top of an instance of the Timer Library.  The Timer Library provides
  20   functions for nanosecond and microsecond delays.  This generic implementation
  21   produces a fixed TickPeriod of 1 100ns unit, and when the WaitForTick() service
  22   is called, the number of ticks passed in is converted to either nanosecond or
  23   microsecond units.  If the number of ticks is small, then nanoseconds are used.
  24   If the number of ticks is large, then microseconds are used.  This prevents
  25   overflows that could occur for long delays if only nanoseconds were used and also
  26   provides the greatest accuracy for small delays.
  27
  28 --*/
  29
  30 #include <PiDxe.h>
  31 #include <Protocol/Metronome.h>
  32 #include <Library/UefiBootServicesTableLib.h>
  33 #include <Library/TimerLib.h>
  34 #include <Library/DebugLib.h>
  35
  36 //
  37 // Function Prototypes
  38 //
  39 EFI_STATUS
  40 EFIAPI
  41 WaitForTick (
  42   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  43   IN UINT32                       TickNumber
  44   );
  45
  46 //
  47 // Handle for the Metronome Architectural Protocol instance produced by this driver
  48 //
  49 EFI_HANDLE  mMetronomeHandle = NULL;
  50
  51 //
  52 // The Metronome Architectural Protocol instance produced by this driver
  53 //
  54 EFI_METRONOME_ARCH_PROTOCOL mMetronome = {
  55   WaitForTick,
  56   1             // TickPeriod = 1*100 ns units
  57 };
  58
  59 /**
  60   The WaitForTick() function waits for the number of ticks specified by
  61   TickNumber from a known time source in the platform.  If TickNumber of
  62   ticks are detected, then EFI_SUCCESS is returned.  The actual time passed
  63   between entry of this function and the first tick is between 0 and
  64   TickPeriod 100 nS units.  If you want to guarantee that at least TickPeriod
  65   time has elapsed, wait for two ticks.  This function waits for a hardware
  66   event to determine when a tick occurs.  It is possible for interrupt
  67   processing, or exception processing to interrupt the execution of the
  68   WaitForTick() function.  Depending on the hardware source for the ticks, it
  69   is possible for a tick to be missed.  This function cannot guarantee that
  70   ticks will not be missed.  If a timeout occurs waiting for the specified
  71   number of ticks, then EFI_TIMEOUT is returned.
  72
  73   @param  This             The EFI_METRONOME_ARCH_PROTOCOL instance.
  74   @param  TickNumber       Number of ticks to wait.
  75
  76   @retval EFI_SUCCESS      The wait for the number of ticks specified by TickNumber
  77                            succeeded.
  78   @retval EFI_TIMEOUT      A timeout occurred waiting for the specified number of ticks.
  79
  80 **/
  81 EFI_STATUS
  82 EFIAPI
  83 WaitForTick (
  84   IN EFI_METRONOME_ARCH_PROTOCOL  *This,
  85   IN UINT32                       TickNumber
  86   )
  87 {
  88   //
  89   // Check the value of TickNumber, so a 32-bit overflow can be avoided
  90   // when TickNumber of converted to nanosecond units
  91   //
  92   if (TickNumber < 10000000) {
  93     //
  94     // If TickNumber is small, then use NanoSecondDelay()
  95     //
  96     NanoSecondDelay (TickNumber * 100);
  97   } else {
  98     //
  99     // If TickNumber is large, then use MicroSecondDelay()
 100     //
 101     MicroSecondDelay (TickNumber / 10);
 102   }
 103   return EFI_SUCCESS;
 104 }
 105
 106 /**
 107   The user Entry Point for module Metronome. The user code starts with this function.
 108
 109   @param[in] ImageHandle    The firmware allocated handle for the EFI image.
 110   @param[in] SystemTable    A pointer to the EFI System Table.
 111
 112   @retval EFI_SUCCESS       The entry point is executed successfully.
 113   @retval other             Some error occurs when executing this entry point.
 114
 115 **/
 116 EFI_STATUS
 117 EFIAPI
 118 InstallMetronome (
 119   IN EFI_HANDLE        ImageHandle,
 120   IN EFI_SYSTEM_TABLE  *SystemTable
 121   )
 122 {
 123   EFI_STATUS  Status;
 124
 125   //
 126   // Make sure the Metronome Architectural Protocol is not already installed in the system
 127   //
 128   ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiMetronomeArchProtocolGuid);
 129
 130   //
 131   // Install on a new handle
 132   //
 133   Status = gBS->InstallMultipleProtocolInterfaces (
 134                   &mMetronomeHandle,
 135                   &gEfiMetronomeArchProtocolGuid, &mMetronome,
 136                   NULL
 137                   );
 138   ASSERT_EFI_ERROR (Status);
 139
 140   return Status;
 141 }