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120 lines
4.1 KiB
C
120 lines
4.1 KiB
C
/** @file
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Produces the Metronome Architectural Protocol on top of Timer Library.
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This is a generic implementation of the Metronome Architectural Protocol that
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layers on top of an instance of the Timer Library. The Timer Library provides
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functions for nanosecond and microsecond delays. This generic implementation
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produces a fixed TickPeriod of 1 100ns unit, and when the WaitForTick() service
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is called, the number of ticks passed in is converted to either nanosecond or
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microsecond units. If the number of ticks is small, then nanoseconds are used.
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If the number of ticks is large, then microseconds are used. This prevents
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overflows that could occur for long delays if only nanoseconds were used and also
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provides the greatest accuracy for small delays.
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Copyright (c) 2008 - 2018, Intel Corporation. All rights reserved.<BR>
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SPDX-License-Identifier: BSD-2-Clause-Patent
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**/
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#include "Metronome.h"
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//
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// Handle for the Metronome Architectural Protocol instance produced by this driver
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//
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EFI_HANDLE mMetronomeHandle = NULL;
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//
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// The Metronome Architectural Protocol instance produced by this driver
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//
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EFI_METRONOME_ARCH_PROTOCOL mMetronome = {
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WaitForTick,
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1 // TickPeriod = 1*100 ns units
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};
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/**
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Waits for the specified number of ticks.
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This function implements EFI_METRONOME_ARCH_PROTOCOL.WaitForTick().
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The WaitForTick() function waits for the number of ticks specified by
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TickNumber from a known time source in the platform. If TickNumber of
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ticks are detected, then EFI_SUCCESS is returned. The actual time passed
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between entry of this function and the first tick is between 0 and
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TickPeriod 100 nS units. If you want to guarantee that at least TickPeriod
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time has elapsed, wait for two ticks. This function waits for a hardware
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event to determine when a tick occurs. It is possible for interrupt
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processing, or exception processing to interrupt the execution of the
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WaitForTick() function. Depending on the hardware source for the ticks, it
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is possible for a tick to be missed. This function cannot guarantee that
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ticks will not be missed. If a timeout occurs waiting for the specified
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number of ticks, then EFI_TIMEOUT is returned.
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@param This The EFI_METRONOME_ARCH_PROTOCOL instance.
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@param TickNumber Number of ticks to wait.
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@retval EFI_SUCCESS The wait for the number of ticks specified by TickNumber
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succeeded.
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@retval EFI_TIMEOUT A timeout occurred waiting for the specified number of ticks.
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**/
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EFI_STATUS
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EFIAPI
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WaitForTick (
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IN EFI_METRONOME_ARCH_PROTOCOL *This,
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IN UINT32 TickNumber
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)
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{
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//
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// Check the value of TickNumber, so a 32-bit overflow can be avoided
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// when TickNumber of converted to nanosecond units
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//
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if (TickNumber < 10000000) {
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//
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// If TickNumber is small, then use NanoSecondDelay()
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//
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NanoSecondDelay (TickNumber * 100);
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} else {
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//
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// If TickNumber is large, then use MicroSecondDelay()
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//
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MicroSecondDelay (TickNumber / 10);
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}
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return EFI_SUCCESS;
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}
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/**
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The user Entry Point for module Metronome. The user code starts with this function.
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@param[in] ImageHandle The firmware allocated handle for the EFI image.
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@param[in] SystemTable A pointer to the EFI System Table.
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@retval EFI_SUCCESS The entry point is executed successfully.
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@retval other Some error occurs when executing this entry point.
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**/
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EFI_STATUS
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EFIAPI
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InstallMetronome (
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IN EFI_HANDLE ImageHandle,
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IN EFI_SYSTEM_TABLE *SystemTable
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)
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{
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EFI_STATUS Status;
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//
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// Make sure the Metronome Architectural Protocol is not already installed in the system
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//
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ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiMetronomeArchProtocolGuid);
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//
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// Install on a new handle
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//
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Status = gBS->InstallMultipleProtocolInterfaces (
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&mMetronomeHandle,
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&gEfiMetronomeArchProtocolGuid, &mMetronome,
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NULL
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);
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ASSERT_EFI_ERROR (Status);
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return Status;
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}
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