Re: [edk2-devel] [PATCH 2/3] ArmPkg: Fix the calculation of the timer period in GenericWatchdogDxe

["Ard Biesheuvel" <ardb@kernel.org>]

Hi Rebecca,

On Wed, 3 Jan 2024 at 21:44, Rebecca Cran
<rebecca@os.amperecomputing.com> wrote:
>
> Fix the calculation of the timer period in GenericWatchdogDxe: we need
> to multiply before dividing to keep the values as integers.
>
> Signed-off-by: Rebecca Cran <rebecca@os.amperecomputing.com>
> ---
>  ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
> index 05df101d5f4b..8f02f38c64e3 100644
> --- a/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
> +++ b/ArmPkg/Drivers/GenericWatchdogDxe/GenericWatchdogDxe.c
> @@ -119,7 +119,7 @@ WatchdogInterruptHandler (
>    // the timer period plus 1.
>    //
>    if (mWatchdogNotify != NULL) {
> -    TimerPeriod = ((TIME_UNITS_PER_SECOND / mTimerFrequencyHz) * mNumTimerTicks);
> +    TimerPeriod = ((TIME_UNITS_PER_SECOND * mNumTimerTicks) / mTimerFrequencyHz);

Could we just store the timer period in a global mTimerPeriod, and get
rid of mNumTimerTicks entirely? AFAICT, that would get rid of these
calculations as well.

>      mWatchdogNotify (TimerPeriod + 1);
>    }
>
> @@ -260,7 +260,7 @@ WatchdogGetTimerPeriod (
>      return EFI_INVALID_PARAMETER;
>    }
>
> -  *TimerPeriod = ((TIME_UNITS_PER_SECOND / mTimerFrequencyHz) * mNumTimerTicks);
> +  *TimerPeriod = ((TIME_UNITS_PER_SECOND * mNumTimerTicks) / mTimerFrequencyHz);
>
>    return EFI_SUCCESS;
>  }
> --
> 2.34.1
>


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