REF:https://bugzilla.tianocore.org/show_bug.cgi?id=4578
The implementation of XhcGetElapsedTicks did not account for
non-zero start and stop values for the performance counter
timer, potentially resulting in an incorrect elapsed tick
count getting returned to the caller. Account for non-zero
start and stop values when calculating the elapsed tick
count.
Cc: Hao A Wu <hao.a...@intel.com>
Cc: Ray Ni <ray...@intel.com>
Signed-off-by: Patrick Henz <patrick.h...@hpe.com>
Reviewed-by:
---
MdeModulePkg/Bus/Pci/XhciDxe/Xhci.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/MdeModulePkg/Bus/Pci/XhciDxe/Xhci.c
b/MdeModulePkg/Bus/Pci/XhciDxe/Xhci.c
index 7a2e32a9dd..6cb97b7452 100644
--- a/MdeModulePkg/Bus/Pci/XhciDxe/Xhci.c
+++ b/MdeModulePkg/Bus/Pci/XhciDxe/Xhci.c
@@ -2389,7 +2389,7 @@ XhcGetElapsedTicks (
// Counter counts upwards, check for an overflow condition
//
if (*PreviousTick > CurrentTick) {
- Delta = (mPerformanceCounterEndValue - *PreviousTick) + CurrentTick;
+ Delta = (CurrentTick - mPerformanceCounterStartValue) +
(mPerformanceCounterEndValue - *PreviousTick);
} else {
Delta = CurrentTick - *PreviousTick;
}
@@ -2398,7 +2398,7 @@ XhcGetElapsedTicks (
// Counter counts downwards, check for an underflow condition
//
if (*PreviousTick < CurrentTick) {
- Delta = (mPerformanceCounterStartValue - CurrentTick) + *PreviousTick;
+ Delta = (mPerformanceCounterStartValue - CurrentTick) + (*PreviousTick -
mPerformanceCounterEndValue);
} else {
Delta = *PreviousTick - CurrentTick;
}
--
2.34.1
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