* [edk2-devel] [PATCH v3] MdeModulePkg/XhciDxe: Non-zero start/stop values in XhcGetElapsedTicks
@ 2024-02-13 16:18 Henz, Patrick
0 siblings, 0 replies; only message in thread
From: Henz, Patrick @ 2024-02-13 16:18 UTC (permalink / raw)
To: devel; +Cc: hao.a.wu, ray.ni, Patrick Henz, Laszlo Ersek
From: Patrick Henz <patrick.henz@hpe.com>
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.wu@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Signed-off-by: Patrick Henz <patrick.henz@hpe.com>
Acked-by: Hao A Wu <hao.a.wu@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---
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 f4e61d223c..ff641d0130 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 = (mXhciPerformanceCounterEndValue - *PreviousTick) + CurrentTick;
+ Delta = (CurrentTick - mXhciPerformanceCounterStartValue) + (mXhciPerformanceCounterEndValue - *PreviousTick);
} else {
Delta = CurrentTick - *PreviousTick;
}
@@ -2398,7 +2398,7 @@ XhcGetElapsedTicks (
// Counter counts downwards, check for an underflow condition
//
if (*PreviousTick < CurrentTick) {
- Delta = (mXhciPerformanceCounterStartValue - CurrentTick) + *PreviousTick;
+ Delta = (mXhciPerformanceCounterStartValue - CurrentTick) + (*PreviousTick - mXhciPerformanceCounterEndValue);
} else {
Delta = *PreviousTick - CurrentTick;
}
--
2.34.1
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2024-02-13 16:18 [edk2-devel] [PATCH v3] MdeModulePkg/XhciDxe: Non-zero start/stop values in XhcGetElapsedTicks Henz, Patrick
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