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* [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Non-zero start/stop values in XhcGetElapsedTicks
@ 2023-10-31 16:51 Henz, Patrick
  2023-10-31 20:51 ` Laszlo Ersek
                   ` (2 more replies)
  0 siblings, 3 replies; 8+ messages in thread
From: Henz, Patrick @ 2023-10-31 16:51 UTC (permalink / raw)
  To: devel; +Cc: hao.a.wu, ray.ni, Patrick Henz

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>
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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^ permalink raw reply related	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2023-11-03  6:40 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2023-10-31 16:51 [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Non-zero start/stop values in XhcGetElapsedTicks Henz, Patrick
2023-10-31 20:51 ` Laszlo Ersek
2023-11-01  1:12 ` Mike Maslenkin
2023-11-02 11:28   ` Laszlo Ersek
2023-11-02 13:06     ` Pedro Falcato
2023-11-03  6:40       ` Laszlo Ersek
2023-11-02 23:01     ` Henz, Patrick
2023-11-01  2:25 ` Wu, Hao A

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