X-Git-Url: https://git.proxmox.com/?p=mirror_edk2.git;a=blobdiff_plain;f=PcAtChipsetPkg%2FLibrary%2FAcpiTimerLib%2FDxeAcpiTimerLib.c;h=67e18a13607fbf82f55741d612e0eb844bab276d;hp=7f7b0f8f62947712e3a3a3d66df51ddeece1c14a;hb=fd501a798402fdc8ce3fe4e7de3927658889b555;hpb=62b8b5be713dd1f801cd44e4eb28f68585a9bd85

diff --git a/PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c b/PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
index 7f7b0f8f62..67e18a1360 100644
--- a/PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
+++ b/PcAtChipsetPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.c
@@ -12,21 +12,39 @@
 
 **/
 
-#include <Base.h>
+#include <PiDxe.h>
 #include <Library/TimerLib.h>
 #include <Library/BaseLib.h>
+#include <Library/HobLib.h>
+
+extern GUID mFrequencyHobGuid;
+
+/**
+  The constructor function enables ACPI IO space.
+
+  If ACPI I/O space not enabled, this function will enable it.
+  It will always return RETURN_SUCCESS.
+
+  @retval EFI_SUCCESS   The constructor always returns RETURN_SUCCESS.
+
+**/
+RETURN_STATUS
+EFIAPI
+AcpiTimerLibConstructor (
+  VOID
+  );
 
 /**
   Calculate TSC frequency.
 
   The TSC counting frequency is determined by comparing how far it counts
-  during a 100us 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 for ACPI_TIMER_FREQUENCY / 10000
-  clocks of the ACPI timer, or 100us. The TSC is then sampled again. The
-  difference multiplied by 10000 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.
+  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.
 
@@ -54,8 +72,41 @@ InternalGetPerformanceCounterFrequency (
   VOID
   ) 
 {
-  if (mPerformanceCounterFrequency == 0) {
+  return  mPerformanceCounterFrequency;
+}
+
+/**
+  The constructor function enables ACPI IO space, and caches PerformanceCounterFrequency. 
+
+  @param  ImageHandle   The firmware allocated handle for the EFI image.
+  @param  SystemTable   A pointer to the EFI System Table.
+
+  @retval EFI_SUCCESS   The constructor always returns RETURN_SUCCESS.
+
+**/
+EFI_STATUS
+EFIAPI
+DxeAcpiTimerLibConstructor (
+  IN EFI_HANDLE        ImageHandle,
+  IN EFI_SYSTEM_TABLE  *SystemTable
+  )
+{
+  EFI_HOB_GUID_TYPE   *GuidHob;
+
+  //
+  // Enable ACPI IO space.
+  //
+  AcpiTimerLibConstructor ();
+
+  //
+  // Initialize PerformanceCounterFrequency
+  //
+  GuidHob = GetFirstGuidHob (&mFrequencyHobGuid);
+  if (GuidHob != NULL) {
+    mPerformanceCounterFrequency = *(UINT64*)GET_GUID_HOB_DATA (GuidHob);
+  } else {
     mPerformanceCounterFrequency = InternalCalculateTscFrequency ();
   }
-  return  mPerformanceCounterFrequency;
+
+  return EFI_SUCCESS;
 }