Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> writes:
> During the reset of ring submission, we first stop the engine by
> clearing the HEAD/TAIL and marking the ring as disabled. However, it
> would be safer to disable the ring (after emptying) before resetting the
> HEAD/TAIL.
>
> Suggested-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
Reviewed-by: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/intel_ring_submission.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_ring_submission.c b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> index 44159595d909..8a5314b97b04 100644
> --- a/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> +++ b/drivers/gpu/drm/i915/gt/intel_ring_submission.c
> @@ -301,13 +301,17 @@ static void xcs_sanitize(struct intel_engine_cs *engine)
>
> static bool stop_ring(struct intel_engine_cs *engine)
> {
> + /* Empty the ring by skipping to the end */
> ENGINE_WRITE_FW(engine, RING_HEAD, ENGINE_READ_FW(engine, RING_TAIL));
> -
> - ENGINE_WRITE_FW(engine, RING_HEAD, 0);
> - ENGINE_WRITE_FW(engine, RING_TAIL, 0);
> + ENGINE_POSTING_READ(engine, RING_HEAD);
>
> /* The ring must be empty before it is disabled */
> ENGINE_WRITE_FW(engine, RING_CTL, 0);
> + ENGINE_POSTING_READ(engine, RING_CTL);
> +
> + /* Then reset the disabled ring */
> + ENGINE_WRITE_FW(engine, RING_HEAD, 0);
> + ENGINE_WRITE_FW(engine, RING_TAIL, 0);
>
> return (ENGINE_READ_FW(engine, RING_HEAD) & HEAD_ADDR) == 0;
> }
> --
> 2.20.1
>
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