Re: [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Non-zero start/stop values in XhcGetElapsedTicks

["Wu, Hao A" <hao.a.wu@intel.com>]

Acked-by: Hao A Wu <hao.a.wu@intel.com>

Best Regards,
Hao Wu

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Henz,
> Patrick
> Sent: Wednesday, November 1, 2023 12:51 AM
> To: devel@edk2.groups.io
> Cc: Wu, Hao A <hao.a.wu@intel.com>; Ni, Ray <ray.ni@intel.com>; Henz,
> Patrick <patrick.henz@hpe.com>
> Subject: [edk2-devel] [PATCH] MdeModulePkg/XhciDxe: Non-zero start/stop
> values in XhcGetElapsedTicks
> 
> 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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