mirror of https://github.com/acidanthera/audk.git
56 lines
1.7 KiB
C
56 lines
1.7 KiB
C
/** @file
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Internal header file for TscTimerLib instances.
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Copyright (c) 2009 - 2011, 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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#ifndef _TSC_TIMER_LIB_INTERNAL_H_
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#define _TSC_TIMER_LIB_INTERNAL_H_
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#include <Ich/GenericIch.h>
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#include <Library/TimerLib.h>
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#include <Library/BaseLib.h>
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#include <Library/IoLib.h>
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#include <Library/PciLib.h>
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#include <Library/PcdLib.h>
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/** Get TSC frequency.
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@return The number of TSC counts per second.
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**/
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UINT64
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InternalGetTscFrequency (
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VOID
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);
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/** Calculate TSC frequency.
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The TSC counting frequency is determined by comparing how far it counts
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during a 1ms period as determined by the ACPI timer. The ACPI timer is
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used because it counts at a known frequency.
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If ACPI I/O space not enabled, this function will enable it. Then the
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TSC is sampled, followed by waiting for 3579 clocks of the ACPI timer, or 1ms.
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The TSC is then sampled again. The difference multiplied by 1000 is the TSC
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frequency. There will be a small error because of the overhead of reading
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the ACPI timer. An attempt is made to determine and compensate for this error.
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@return The number of TSC counts per second.
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**/
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UINT64
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InternalCalculateTscFrequency (
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VOID
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);
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#endif
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