diff options
| -rw-r--r-- | MdePkg/Library/DxeTimerLibEsal/DxeTimerLibEsal.c | 44 |
1 files changed, 44 insertions, 0 deletions
diff --git a/MdePkg/Library/DxeTimerLibEsal/DxeTimerLibEsal.c b/MdePkg/Library/DxeTimerLibEsal/DxeTimerLibEsal.c index 964f814bb2..8ca3ec6f8b 100644 --- a/MdePkg/Library/DxeTimerLibEsal/DxeTimerLibEsal.c +++ b/MdePkg/Library/DxeTimerLibEsal/DxeTimerLibEsal.c @@ -177,3 +177,47 @@ GetPerformanceCounterProperties ( return BaseFrequence * (PalRet.r11 >> 32) / (UINT32)PalRet.r11;
}
+
+/**
+ Converts elapsed ticks of performance counter to time in nanoseconds.
+
+ This function converts the elapsed ticks of running performance counter to
+ time value in unit of nanoseconds.
+
+ @param Ticks The number of elapsed ticks of running performance counter.
+
+ @return The elapsed time in nanoseconds.
+
+**/
+UINT64
+EFIAPI
+GetTimeInNanoSecond (
+ IN UINT64 Ticks
+ )
+{
+ UINT64 Frequency;
+ UINT64 NanoSeconds;
+ UINT64 Remainder;
+ INTN Shift;
+
+ Frequency = GetPerformanceCounterProperties (NULL, NULL);
+
+ //
+ // Ticks
+ // Time = --------- x 1,000,000,000
+ // Frequency
+ //
+ NanoSeconds = MultU64x32 (DivU64x64Remainder (Ticks, Frequency, &Remainder), 1000000000u);
+
+ //
+ // Ensure (Remainder * 1,000,000,000) will not overflow 64-bit.
+ // Since 2^29 < 1,000,000,000 = 0x3B9ACA00 < 2^30, Remainder should < 2^(64-30) = 2^34,
+ // i.e. highest bit set in Remainder should <= 33.
+ //
+ Shift = MAX (0, HighBitSet64 (Remainder) - 33);
+ Remainder = RShiftU64 (Remainder, (UINTN) Shift);
+ Frequency = RShiftU64 (Frequency, (UINTN) Shift);
+ NanoSeconds += DivU64x64Remainder (MultU64x32 (Remainder, 1000000000u), Frequency, NULL);
+
+ return NanoSeconds;
+}
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