PcAtChipsetPkg: new AcpiTimerLib libraries.

Two library instances are added to support BASE type and DXE type. Those libraries provides basic timer support using the ACPI timer hardware.  The performance  counter features are provided by the processors time stamp counter.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Gao, Liming <liming.gao@intel.com>
Reviewed-by: Kinney, Michael D <michael.d.kinney@intel.com>


git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15803 6f19259b-4bc3-4df7-8a09-765794883524

PcAtChipsetPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.c

@@ -0,0 +1,42 @@
+/** @file
+  ACPI Timer implements one instance of Timer Library.
+
+  Copyright (c) 2013 - 2014, 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>
+
+/**
+  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
+  ) 
+{
+  BOOLEAN  InterruptState;
+  UINT64   Count;
+  UINT64   Frequency;
+  
+  InterruptState = SaveAndDisableInterrupts ();
+  Count = GetPerformanceCounter ();
+  MicroSecondDelay (100);
+  Frequency = MultU64x32 (GetPerformanceCounter () - Count, 10000);
+  SetInterruptState (InterruptState);
+  return Frequency;
+}