[PATCH v2] drm/xe: Explicitly cast to u64 to avoid overflow

[Dixit, Ashutosh]

On Thu, 13 Jun 2024 23:24:15 -0700, Zbigniew Kempczyński wrote:
>

Hi Zbyzsek,

> Without casting whole expression will be calculated on u32 what
> means adding U32_MAX effectively decreases the result by one due to
> overflow. Fix this and use explicit cast to u64.
>
> Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
> Cc: Matthew Brost <matthew.brost at intel.com>
> ---
> v2: Fix spacing
> ---
>  drivers/gpu/drm/xe/xe_guc_submit.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_guc_submit.c b/drivers/gpu/drm/xe/xe_guc_submit.c
> index 74552391dc5a..f46d1e18f8e7 100644
> --- a/drivers/gpu/drm/xe/xe_guc_submit.c
> +++ b/drivers/gpu/drm/xe/xe_guc_submit.c
> @@ -967,7 +967,7 @@ static bool check_timeout(struct xe_exec_queue *q, struct xe_sched_job *job)
>	xe_gt_assert(gt, timeout_ms < 100 * MSEC_PER_SEC);
>
>	if (ctx_timestamp < ctx_job_timestamp)
> -		diff = ctx_timestamp + U32_MAX - ctx_job_timestamp;
> +		diff = (u64)ctx_timestamp + U32_MAX - ctx_job_timestamp;
>	else
>		diff = ctx_timestamp - ctx_job_timestamp;

Looks like the function expects to be called every 100 ms, and counter
wraps around 223 s, so previous code is fine with normal 2's complement
arithmetic?

Thanks.
--
Ashutosh