| 1 | /** @file
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| 2 | Produces the Metronome Architectural Protocol on top of Timer Library.
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| 3 |
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| 4 | This is a generic implementation of the Metronome Architectural Protocol that
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| 5 | layers on top of an instance of the Timer Library. The Timer Library provides
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| 6 | functions for nanosecond and microsecond delays. This generic implementation
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| 7 | produces a fixed TickPeriod of 1 100ns unit, and when the WaitForTick() service
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| 8 | is called, the number of ticks passed in is converted to either nanosecond or
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| 9 | microsecond units. If the number of ticks is small, then nanoseconds are used.
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| 10 | If the number of ticks is large, then microseconds are used. This prevents
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| 11 | overflows that could occur for long delays if only nanoseconds were used and also
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| 12 | provides the greatest accuracy for small delays.
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| 13 |
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| 14 | Copyright (c) 2008 - 2018, Intel Corporation. All rights reserved.<BR>
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| 15 | SPDX-License-Identifier: BSD-2-Clause-Patent
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| 16 |
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| 17 | **/
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| 18 |
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| 19 | #include "Metronome.h"
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| 20 |
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| 21 | //
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| 22 | // Handle for the Metronome Architectural Protocol instance produced by this driver
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| 23 | //
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| 24 | EFI_HANDLE mMetronomeHandle = NULL;
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| 25 |
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| 26 | //
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| 27 | // The Metronome Architectural Protocol instance produced by this driver
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| 28 | //
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| 29 | EFI_METRONOME_ARCH_PROTOCOL mMetronome = {
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| 30 | WaitForTick,
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| 31 | 1 // TickPeriod = 1*100 ns units
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| 32 | };
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| 33 |
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| 34 | /**
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| 35 | Waits for the specified number of ticks.
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| 36 |
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| 37 | This function implements EFI_METRONOME_ARCH_PROTOCOL.WaitForTick().
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| 38 | The WaitForTick() function waits for the number of ticks specified by
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| 39 | TickNumber from a known time source in the platform. If TickNumber of
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| 40 | ticks are detected, then EFI_SUCCESS is returned. The actual time passed
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| 41 | between entry of this function and the first tick is between 0 and
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| 42 | TickPeriod 100 nS units. If you want to guarantee that at least TickPeriod
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| 43 | time has elapsed, wait for two ticks. This function waits for a hardware
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| 44 | event to determine when a tick occurs. It is possible for interrupt
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| 45 | processing, or exception processing to interrupt the execution of the
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| 46 | WaitForTick() function. Depending on the hardware source for the ticks, it
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| 47 | is possible for a tick to be missed. This function cannot guarantee that
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| 48 | ticks will not be missed. If a timeout occurs waiting for the specified
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| 49 | number of ticks, then EFI_TIMEOUT is returned.
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| 50 |
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| 51 | @param This The EFI_METRONOME_ARCH_PROTOCOL instance.
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| 52 | @param TickNumber Number of ticks to wait.
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| 53 |
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| 54 | @retval EFI_SUCCESS The wait for the number of ticks specified by TickNumber
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| 55 | succeeded.
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| 56 | @retval EFI_TIMEOUT A timeout occurred waiting for the specified number of ticks.
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| 57 |
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| 58 | **/
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| 59 | EFI_STATUS
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| 60 | EFIAPI
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| 61 | WaitForTick (
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| 62 | IN EFI_METRONOME_ARCH_PROTOCOL *This,
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| 63 | IN UINT32 TickNumber
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| 64 | )
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| 65 | {
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| 66 | //
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| 67 | // Check the value of TickNumber, so a 32-bit overflow can be avoided
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| 68 | // when TickNumber of converted to nanosecond units
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| 69 | //
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| 70 | if (TickNumber < 10000000) {
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| 71 | //
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| 72 | // If TickNumber is small, then use NanoSecondDelay()
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| 73 | //
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| 74 | NanoSecondDelay (TickNumber * 100);
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| 75 | } else {
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| 76 | //
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| 77 | // If TickNumber is large, then use MicroSecondDelay()
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| 78 | //
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| 79 | MicroSecondDelay (TickNumber / 10);
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| 80 | }
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| 81 |
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| 82 | return EFI_SUCCESS;
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| 83 | }
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| 84 |
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| 85 | /**
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| 86 | The user Entry Point for module Metronome. The user code starts with this function.
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| 87 |
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| 88 | @param[in] ImageHandle The firmware allocated handle for the EFI image.
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| 89 | @param[in] SystemTable A pointer to the EFI System Table.
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| 90 |
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| 91 | @retval EFI_SUCCESS The entry point is executed successfully.
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| 92 | @retval other Some error occurs when executing this entry point.
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| 93 |
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| 94 | **/
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| 95 | EFI_STATUS
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| 96 | EFIAPI
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| 97 | InstallMetronome (
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| 98 | IN EFI_HANDLE ImageHandle,
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| 99 | IN EFI_SYSTEM_TABLE *SystemTable
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| 100 | )
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| 101 | {
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| 102 | EFI_STATUS Status;
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| 103 |
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| 104 | //
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| 105 | // Make sure the Metronome Architectural Protocol is not already installed in the system
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| 106 | //
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| 107 | ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiMetronomeArchProtocolGuid);
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| 108 |
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| 109 | //
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| 110 | // Install on a new handle
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| 111 | //
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| 112 | Status = gBS->InstallMultipleProtocolInterfaces (
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| 113 | &mMetronomeHandle,
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| 114 | &gEfiMetronomeArchProtocolGuid,
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| 115 | &mMetronome,
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| 116 | NULL
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| 117 | );
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| 118 | ASSERT_EFI_ERROR (Status);
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| 119 |
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| 120 | return Status;
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| 121 | }
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