1 files changed, 64 insertions, 0 deletions
diff --git a/roms/edk2/PcAtChipsetPkg/Library/AcpiTimerLib/PeiAcpiTimerLib.c b/roms/edk2/PcAtChipsetPkg/Library/AcpiTimerLib/PeiAcpiTimerLib.c
new file mode 100644
index 000000000..a669794c3
--- /dev/null
+++ b/roms/edk2/PcAtChipsetPkg/Library/AcpiTimerLib/PeiAcpiTimerLib.c
@@ -0,0 +1,64 @@
+/** @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;
+}