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/** @file
Produces the Metronome Architectural Protocol on top of Timer Library.
This is a generic implementation of the Metronome Architectural Protocol that
layers on top of an instance of the Timer Library. The Timer Library provides
functions for nanosecond and microsecond delays. This generic implementation
produces a fixed TickPeriod of 1 100ns unit, and when the WaitForTick() service
is called, the number of ticks passed in is converted to either nanosecond or
microsecond units. If the number of ticks is small, then nanoseconds are used.
If the number of ticks is large, then microseconds are used. This prevents
overflows that could occur for long delays if only nanoseconds were used and also
provides the greatest accuracy for small delays.
Copyright (c) 2008, Intel Corporation
All rights reserved. This program and the accompanying materials
are licensed and made available under the terms and conditions of the BSD License
which accompanies this distribution. The full text of the license may be found at
http://opensource.org/licenses/bsd-license.php
THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/
#include "Metronome.h"
//
// Handle for the Metronome Architectural Protocol instance produced by this driver
//
EFI_HANDLE mMetronomeHandle = NULL;
//
// The Metronome Architectural Protocol instance produced by this driver
//
EFI_METRONOME_ARCH_PROTOCOL mMetronome = {
WaitForTick,
1 // TickPeriod = 1*100 ns units
};
/**
Waits for the specified number of ticks.
This function implements EFI_METRONOME_ARCH_PROTOCOL.WaitForTick().
The WaitForTick() function waits for the number of ticks specified by
TickNumber from a known time source in the platform. If TickNumber of
ticks are detected, then EFI_SUCCESS is returned. The actual time passed
between entry of this function and the first tick is between 0 and
TickPeriod 100 nS units. If you want to guarantee that at least TickPeriod
time has elapsed, wait for two ticks. This function waits for a hardware
event to determine when a tick occurs. It is possible for interrupt
processing, or exception processing to interrupt the execution of the
WaitForTick() function. Depending on the hardware source for the ticks, it
is possible for a tick to be missed. This function cannot guarantee that
ticks will not be missed. If a timeout occurs waiting for the specified
number of ticks, then EFI_TIMEOUT is returned.
@param This The EFI_METRONOME_ARCH_PROTOCOL instance.
@param TickNumber Number of ticks to wait.
@retval EFI_SUCCESS The wait for the number of ticks specified by TickNumber
succeeded.
@retval EFI_TIMEOUT A timeout occurred waiting for the specified number of ticks.
**/
EFI_STATUS
EFIAPI
WaitForTick (
IN EFI_METRONOME_ARCH_PROTOCOL *This,
IN UINT32 TickNumber
)
{
//
// Check the value of TickNumber, so a 32-bit overflow can be avoided
// when TickNumber of converted to nanosecond units
//
if (TickNumber < 10000000) {
//
// If TickNumber is small, then use NanoSecondDelay()
//
NanoSecondDelay (TickNumber * 100);
} else {
//
// If TickNumber is large, then use MicroSecondDelay()
//
MicroSecondDelay (TickNumber / 10);
}
return EFI_SUCCESS;
}
/**
The user Entry Point for module Metronome. The user code starts with this function.
@param[in] ImageHandle The firmware allocated handle for the EFI image.
@param[in] SystemTable A pointer to the EFI System Table.
@retval EFI_SUCCESS The entry point is executed successfully.
@retval other Some error occurs when executing this entry point.
**/
EFI_STATUS
EFIAPI
InstallMetronome (
IN EFI_HANDLE ImageHandle,
IN EFI_SYSTEM_TABLE *SystemTable
)
{
EFI_STATUS Status;
//
// Make sure the Metronome Architectural Protocol is not already installed in the system
//
ASSERT_PROTOCOL_ALREADY_INSTALLED (NULL, &gEfiMetronomeArchProtocolGuid);
//
// Install on a new handle
//
Status = gBS->InstallMultipleProtocolInterfaces (
&mMetronomeHandle,
&gEfiMetronomeArchProtocolGuid, &mMetronome,
NULL
);
ASSERT_EFI_ERROR (Status);
return Status;
}
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