1 files changed, 61 insertions, 0 deletions
diff --git a/Core/PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c b/Core/PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
new file mode 100644
index 0000000000..b141c680fb
--- /dev/null
+++ b/Core/PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
@@ -0,0 +1,61 @@
+/** @file
+  ACPI Timer implements one instance of Timer Library.
+
+  Copyright (c) 2013 - 2016, Intel Corporation. All rights reserved.<BR>
+  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 <Base.h>
+#include <Library/TimerLib.h>
+#include <Library/BaseLib.h>
+
+/**
+  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
+  );
+
+//
+// Cached performance counter frequency
+//
+UINT64  mPerformanceCounterFrequency = 0;
+
+/**
+  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
+  ) 
+{
+  if (mPerformanceCounterFrequency == 0) {
+    mPerformanceCounterFrequency = InternalCalculateTscFrequency ();
+  }
+  return  mPerformanceCounterFrequency;
+}