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

[mirror_edk2.git] / PerformancePkg / Library / PeiTscTimerLib / PeiTscTimerLib.c

diff --git a/PerformancePkg/Library/PeiTscTimerLib/PeiTscTimerLib.c b/PerformancePkg/Library/PeiTscTimerLib/PeiTscTimerLib.c
index be6b66e728769b39fc12ce1825c80b8e5474a82f..4c3796444531958590b6e5acda580e15e0b313fb 100644 (file)
--- a/PerformancePkg/Library/PeiTscTimerLib/PeiTscTimerLib.c
+++ b/PerformancePkg/Library/PeiTscTimerLib/PeiTscTimerLib.c
@@ -263,3 +263,47 @@ GetPerformanceCounterProperties (
 \r
   return InternalGetTscFrequency ();\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  Frequency;\r
+  UINT64  NanoSeconds;\r
+  UINT64  Remainder;\r
+  INTN    Shift;\r
+\r
+  Frequency = GetPerformanceCounterProperties (NULL, NULL);\r
+\r
+  //\r
+  //          Ticks\r
+  // Time = --------- x 1,000,000,000\r
+  //        Frequency\r
+  //\r
+  NanoSeconds = MultU64x32 (DivU64x64Remainder (Ticks, Frequency, &Remainder), 1000000000u);\r
+\r
+  //\r
+  // Ensure (Remainder * 1,000,000,000) will not overflow 64-bit.\r
+  // Since 2^29 < 1,000,000,000 = 0x3B9ACA00 < 2^30, Remainder should < 2^(64-30) = 2^34,\r
+  // i.e. highest bit set in Remainder should <= 33.\r
+  //\r
+  Shift = MAX (0, HighBitSet64 (Remainder) - 33);\r
+  Remainder = RShiftU64 (Remainder, (UINTN) Shift);\r
+  Frequency = RShiftU64 (Frequency, (UINTN) Shift);\r
+  NanoSeconds += DivU64x64Remainder (MultU64x32 (Remainder, 1000000000u), Frequency, NULL);\r
+\r
+  return NanoSeconds;\r
+}\r