[RFC PATCH 45/97] drm/i915/guc: Add bypass tasklet submission path to GuC

[Matthew Brost]

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>
---
 .../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 0955a8b00ee8..2fd83562c1d1 100644
--- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
+++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
@@ -171,6 +171,12 @@ 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;
@@ -214,8 +220,7 @@ 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
@@ -499,20 +504,36 @@ 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));
-
-	i915_sched_engine_hi_kick(sched_engine);
+	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)
+		i915_sched_engine_hi_kick(sched_engine);
 
 	spin_unlock_irqrestore(&sched_engine->lock, flags);
 }
-- 
2.28.0