mirror of https://github.com/acidanthera/audk.git
49 lines
1.4 KiB
C
49 lines
1.4 KiB
C
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/** @file
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ACPI Timer implements one instance of Timer Library.
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Copyright (c) 2013 - 2014, Intel Corporation. All rights reserved.<BR>
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This program and the accompanying materials
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are licensed and made available under the terms and conditions of the BSD License
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which accompanies this distribution. The full text of the license may be found at
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http://opensource.org/licenses/bsd-license.php
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THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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**/
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#include <Base.h>
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#include <Library/TimerLib.h>
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#include <Library/BaseLib.h>
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//
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// Cached performance counter frequency
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//
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UINT64 mPerformanceCounterFrequency = 0;
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/**
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Internal function to retrieves the 64-bit frequency in Hz.
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Internal function to retrieves the 64-bit frequency in Hz.
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@return The frequency in Hz.
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**/
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UINT64
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InternalGetPerformanceCounterFrequency (
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VOID
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)
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{
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BOOLEAN InterruptState;
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UINT64 Count;
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if (mPerformanceCounterFrequency == 0) {
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InterruptState = SaveAndDisableInterrupts ();
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Count = GetPerformanceCounter ();
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MicroSecondDelay (100);
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mPerformanceCounterFrequency = MultU64x32 (GetPerformanceCounter () - Count, 10000);
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SetInterruptState (InterruptState);
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}
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return mPerformanceCounterFrequency;
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}
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