[PATCH 12/47] drm/i915/guc: Add bypass tasklet submission path to GuC

[John Harrison]

On 6/24/2021 00:04, Matthew Brost wrote:
> Add bypass tasklet submission path to GuC. The tasklet is only used if H2G
> channel has backpresure.
>
> Signed-off-by: Matthew Brost <matthew.brost at intel.com>
Reviewed-by: John Harrison <John.C.Harrison at Intel.com>

> ---
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c | 37 +++++++++++++++----
>   1 file changed, 29 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index ee933efbf0ff..38aff83ee9fa 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -172,6 +172,12 @@ static int guc_add_request(struct intel_guc *guc, struct i915_request *rq)
>   	return err;
>   }
>   
> +static inline void guc_set_lrc_tail(struct i915_request *rq)
> +{
> +	rq->context->lrc_reg_state[CTX_RING_TAIL] =
> +		intel_ring_set_tail(rq->ring, rq->tail);
> +}
> +
>   static inline int rq_prio(const struct i915_request *rq)
>   {
>   	return rq->sched.attr.priority;
> @@ -215,8 +221,7 @@ static int guc_dequeue_one_context(struct intel_guc *guc)
>   	}
>   done:
>   	if (submit) {
> -		last->context->lrc_reg_state[CTX_RING_TAIL] =
> -			intel_ring_set_tail(last->ring, last->tail);
> +		guc_set_lrc_tail(last);
>   resubmit:
>   		/*
>   		 * We only check for -EBUSY here even though it is possible for
> @@ -496,20 +501,36 @@ static inline void queue_request(struct i915_sched_engine *sched_engine,
>   	set_bit(I915_FENCE_FLAG_PQUEUE, &rq->fence.flags);
>   }
>   
> +static int guc_bypass_tasklet_submit(struct intel_guc *guc,
> +				     struct i915_request *rq)
> +{
> +	int ret;
> +
> +	__i915_request_submit(rq);
> +
> +	trace_i915_request_in(rq, 0);
> +
> +	guc_set_lrc_tail(rq);
> +	ret = guc_add_request(guc, rq);
> +	if (ret == -EBUSY)
> +		guc->stalled_request = rq;
> +
> +	return ret;
> +}
> +
>   static void guc_submit_request(struct i915_request *rq)
>   {
>   	struct i915_sched_engine *sched_engine = rq->engine->sched_engine;
> +	struct intel_guc *guc = &rq->engine->gt->uc.guc;
>   	unsigned long flags;
>   
>   	/* Will be called from irq-context when using foreign fences. */
>   	spin_lock_irqsave(&sched_engine->lock, flags);
>   
> -	queue_request(sched_engine, rq, rq_prio(rq));
> -
> -	GEM_BUG_ON(i915_sched_engine_is_empty(sched_engine));
> -	GEM_BUG_ON(list_empty(&rq->sched.link));
> -
> -	tasklet_hi_schedule(&sched_engine->tasklet);
> +	if (guc->stalled_request || !i915_sched_engine_is_empty(sched_engine))
> +		queue_request(sched_engine, rq, rq_prio(rq));
> +	else if (guc_bypass_tasklet_submit(guc, rq) == -EBUSY)
> +		tasklet_hi_schedule(&sched_engine->tasklet);
>   
>   	spin_unlock_irqrestore(&sched_engine->lock, flags);
>   }