5220bd211d
REF: https://bugzilla.tianocore.org/show_bug.cgi?id=3737 Apply uncrustify changes to .c/.h files in the PcAtChipsetPkg package Cc: Andrew Fish <afish@apple.com> Cc: Leif Lindholm <leif@nuviainc.com> Cc: Michael D Kinney <michael.d.kinney@intel.com> Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com> Reviewed-by: Ray Ni <ray.ni@intel.com>
65 lines
1.8 KiB
C
65 lines
1.8 KiB
C
/** @file
|
|
ACPI Timer implements one instance of Timer Library.
|
|
|
|
Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.<BR>
|
|
SPDX-License-Identifier: BSD-2-Clause-Patent
|
|
|
|
**/
|
|
|
|
#include <PiPei.h>
|
|
#include <Library/TimerLib.h>
|
|
#include <Library/BaseLib.h>
|
|
#include <Library/HobLib.h>
|
|
#include <Library/DebugLib.h>
|
|
|
|
extern GUID mFrequencyHobGuid;
|
|
|
|
/**
|
|
Calculate TSC frequency.
|
|
|
|
The TSC counting frequency is determined by comparing how far it counts
|
|
during a 101.4 us period as determined by the ACPI timer.
|
|
The ACPI timer is used because it counts at a known frequency.
|
|
The TSC is sampled, followed by waiting 363 counts of the ACPI timer,
|
|
or 101.4 us. The TSC is then sampled again. The difference multiplied by
|
|
9861 is the TSC frequency. There will be a small error because of the
|
|
overhead of reading the ACPI timer. An attempt is made to determine and
|
|
compensate for this error.
|
|
|
|
@return The number of TSC counts per second.
|
|
|
|
**/
|
|
UINT64
|
|
InternalCalculateTscFrequency (
|
|
VOID
|
|
);
|
|
|
|
/**
|
|
Internal function to retrieves the 64-bit frequency in Hz.
|
|
|
|
Internal function to retrieves the 64-bit frequency in Hz.
|
|
|
|
@return The frequency in Hz.
|
|
|
|
**/
|
|
UINT64
|
|
InternalGetPerformanceCounterFrequency (
|
|
VOID
|
|
)
|
|
{
|
|
UINT64 *PerformanceCounterFrequency;
|
|
EFI_HOB_GUID_TYPE *GuidHob;
|
|
|
|
PerformanceCounterFrequency = NULL;
|
|
GuidHob = GetFirstGuidHob (&mFrequencyHobGuid);
|
|
if (GuidHob == NULL) {
|
|
PerformanceCounterFrequency = (UINT64 *)BuildGuidHob (&mFrequencyHobGuid, sizeof (*PerformanceCounterFrequency));
|
|
ASSERT (PerformanceCounterFrequency != NULL);
|
|
*PerformanceCounterFrequency = InternalCalculateTscFrequency ();
|
|
} else {
|
|
PerformanceCounterFrequency = (UINT64 *)GET_GUID_HOB_DATA (GuidHob);
|
|
}
|
|
|
|
return *PerformanceCounterFrequency;
|
|
}
|