PcAtChipsetPkg: Add PeiAcpiTimerLib to save Frequency in HOB

[mirror_edk2.git] / PcAtChipsetPkg / Library / AcpiTimerLib / PeiAcpiTimerLib.c

diff --git a/PcAtChipsetPkg/Library/AcpiTimerLib/PeiAcpiTimerLib.c b/PcAtChipsetPkg/Library/AcpiTimerLib/PeiAcpiTimerLib.c
new file mode 100644 (file)
index 0000000..45a341f
--- /dev/null
+++ b/PcAtChipsetPkg/Library/AcpiTimerLib/PeiAcpiTimerLib.c
@@ -0,0 +1,69 @@
+/** @file\r
+  ACPI Timer implements one instance of Timer Library.\r
+\r
+  Copyright (c) 2013 - 2018, Intel Corporation. All rights reserved.<BR>\r
+  This program and the accompanying materials\r
+  are licensed and made available under the terms and conditions of the BSD License\r
+  which accompanies this distribution.  The full text of the license may be found at\r
+  http://opensource.org/licenses/bsd-license.php\r
+\r
+  THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,\r
+  WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.\r
+\r
+**/\r
+\r
+#include <PiPei.h>\r
+#include <Library/TimerLib.h>\r
+#include <Library/BaseLib.h>\r
+#include <Library/HobLib.h>\r
+\r
+extern GUID mFrequencyHobGuid;\r
+\r
+/**\r
+  Calculate TSC frequency.\r
+\r
+  The TSC counting frequency is determined by comparing how far it counts\r
+  during a 101.4 us period as determined by the ACPI timer.\r
+  The ACPI timer is used because it counts at a known frequency.\r
+  The TSC is sampled, followed by waiting 363 counts of the ACPI timer,\r
+  or 101.4 us. The TSC is then sampled again. The difference multiplied by\r
+  9861 is the TSC frequency. There will be a small error because of the\r
+  overhead of reading the ACPI timer. An attempt is made to determine and\r
+  compensate for this error.\r
+\r
+  @return The number of TSC counts per second.\r
+\r
+**/\r
+UINT64\r
+InternalCalculateTscFrequency (\r
+  VOID\r
+  );\r
+\r
+/**\r
+  Internal function to retrieves the 64-bit frequency in Hz.\r
+\r
+  Internal function to retrieves the 64-bit frequency in Hz.\r
+\r
+  @return The frequency in Hz.\r
+\r
+**/\r
+UINT64\r
+InternalGetPerformanceCounterFrequency (\r
+  VOID\r
+  )\r
+{\r
+  UINT64              *PerformanceCounterFrequency;\r
+  EFI_HOB_GUID_TYPE   *GuidHob;\r
+\r
+  PerformanceCounterFrequency = NULL;\r
+  GuidHob = GetFirstGuidHob (&mFrequencyHobGuid);\r
+  if (GuidHob == NULL) {\r
+    PerformanceCounterFrequency  = (UINT64*)BuildGuidHob(&mFrequencyHobGuid, sizeof (*PerformanceCounterFrequency));\r
+    ASSERT (PerformanceCounterFrequency != NULL);\r
+    *PerformanceCounterFrequency = InternalCalculateTscFrequency ();\r
+  } else {\r
+    PerformanceCounterFrequency = (UINT64*)GET_GUID_HOB_DATA (GuidHob);\r
+  }\r
+\r
+  return  *PerformanceCounterFrequency;\r
+}\r