On Tue, Sep 29, 2026 at 12:20:37PM -0700, Alan Previn wrote:
> Check for overflow in udelay use in __xe_mmio_wait32 and
> avoid growing delays becoming intollerably large by capping the
> in-loop wait time.
>
> v7: - Change assisted-by to "LLM" (Rodrigo).
> - Move the max-wait macro to outside the function (Rodrigo).
> v6: - Fix commit message to remove items dropped in v5. Fix the
> use of MAX_UDELAY_MS for microsecond unit. (Shasiko review).
> v5: - Simplify: don't introduce additional redesign and
> use min_t with a backoff to cap wait. (Rodrigo).
> v4: - Simplify using poll_timeout_us and poll_timeout_us_atomic and
> update all callers to never use a param for atomic (Jani)
> v3: - Use div64_s64 kernel API for 32-bit vs 64-bit division.
> v2: - Fixed checkpatch failure.
> - Added helper for 64-bit DIV_ROUND_UP on 32-bit CPU (Shasiko
> review). Fixed bug max range in usleep_range(Shasiko review)
>
> Fixes: 5c09bd6ccd41 ("drm/xe/mmio: Move xe_mmio_wait32() to xe_mmio.c")
> Signed-off-by: Alan Previn <[email protected]>
> Reviewed-by: Rodrigo Vivi <[email protected]>
> Assisted-by: LLM
> ---
pushed to drm-xe-next.
Thanks a lot for the fix and the patience ;)
> drivers/gpu/drm/xe/xe_mmio.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> index 7fa18dfcb5a2..455a07d79cd9 100644
> --- a/drivers/gpu/drm/xe/xe_mmio.c
> +++ b/drivers/gpu/drm/xe/xe_mmio.c
> @@ -320,6 +320,7 @@ u64 xe_mmio_read64_2x32(struct xe_mmio *mmio, struct
> xe_reg reg)
> return (u64)udw << 32 | ldw;
> }
>
> +#define __XE_MMIO_WAIT_MAX_BACKOFF_100MS (100 * USEC_PER_MSEC)
> static int __xe_mmio_wait32(struct xe_mmio *mmio, struct xe_reg reg, u32
> mask, u32 val,
> u32 timeout_us, u32 *out_val, bool atomic, bool
> expect_match)
> {
> @@ -350,10 +351,10 @@ static int __xe_mmio_wait32(struct xe_mmio *mmio,
> struct xe_reg reg, u32 mask, u
> wait = ktime_us_delta(end, cur);
>
> if (atomic)
> - udelay(wait);
> + udelay(min_t(s64, wait, (MAX_UDELAY_MS * 1000)));
> else
> usleep_range(wait, wait << 1);
> - wait <<= 1;
> + wait = min_t(s64, wait << 1, __XE_MMIO_WAIT_MAX_BACKOFF_100MS);
> }
>
> if (ret != 0) {
> --
> 2.43.0
>
