Add new API GetTimeInNanoSecond() to TimerLib to convert elapsed ticks to time in...

[mirror_edk2.git] / OvmfPkg / Library / AcpiTimerLib / AcpiTimerLib.c

diff --git a/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c b/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c
index 7a6745caf0c5d4de584f32ab3dae8da98f1fb7af..a2f774f7ee6a8aa4c553c0402ba4c929a6460681 100644 (file)
--- a/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c
+++ b/OvmfPkg/Library/AcpiTimerLib/AcpiTimerLib.c
@@ -239,3 +239,39 @@ GetPerformanceCounterProperties (
 \r
   return ACPI_TIMER_FREQUENCY;\r
 }\r
+\r
+/**\r
+  Converts elapsed ticks of performance counter to time in nanoseconds.\r
+\r
+  This function converts the elapsed ticks of running performance counter to\r
+  time value in unit of nanoseconds.\r
+\r
+  @param  Ticks     The number of elapsed ticks of running performance counter.\r
+\r
+  @return The elapsed time in nanoseconds.\r
+\r
+**/\r
+UINT64\r
+EFIAPI\r
+GetTimeInNanoSecond (\r
+  IN      UINT64                     Ticks\r
+  )\r
+{\r
+  UINT64  NanoSeconds;\r
+  UINT32  Remainder;\r
+\r
+  //\r
+  //          Ticks\r
+  // Time = --------- x 1,000,000,000\r
+  //        Frequency\r
+  //\r
+  NanoSeconds = MultU64x32 (DivU64x32Remainder (Ticks, ACPI_TIMER_FREQUENCY, &Remainder), 1000000000u);\r
+\r
+  //\r
+  // Frequency < 0x100000000, so Remainder < 0x100000000, then (Remainder * 1,000,000,000)\r
+  // will not overflow 64-bit.\r
+  //\r
+  NanoSeconds += DivU64x32 (MultU64x32 ((UINT64) Remainder, 1000000000u), ACPI_TIMER_FREQUENCY);\r
+\r
+  return NanoSeconds;\r
+}\r