drm/i915: Add kick_backend function to i915_sched_engine

Not all back-ends require a kick after a  scheduling update, so make the
kick a call-back function that the  back-end can opt-in to. Also move
the current kick function from the scheduler to the execlists file as it
is specific to that back-end.

Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210618010638.98941-7-matthew.brost@intel.com

1 files changed, 52 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
index 8a3d4014fd2c..9487d9e0be62 100644
--- a/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
+++ b/drivers/gpu/drm/i915/gt/intel_execlists_submission.c
@@ -3116,10 +3116,61 @@ static bool can_preempt(struct intel_engine_cs *engine)
 	return engine->class != RENDER_CLASS;
 }
 
+static void kick_execlists(const struct i915_request *rq, int prio)
+{
+	struct intel_engine_cs *engine = rq->engine;
+	struct i915_sched_engine *sched_engine = engine->sched_engine;
+	const struct i915_request *inflight;
+
+	/*
+	 * We only need to kick the tasklet once for the high priority
+	 * new context we add into the queue.
+	 */
+	if (prio <= sched_engine->queue_priority_hint)
+		return;
+
+	rcu_read_lock();
+
+	/* Nothing currently active? We're overdue for a submission! */
+	inflight = execlists_active(&engine->execlists);
+	if (!inflight)
+		goto unlock;
+
+	/*
+	 * If we are already the currently executing context, don't
+	 * bother evaluating if we should preempt ourselves.
+	 */
+	if (inflight->context == rq->context)
+		goto unlock;
+
+	ENGINE_TRACE(engine,
+		     "bumping queue-priority-hint:%d for rq:%llx:%lld, inflight:%llx:%lld prio %d\n",
+		     prio,
+		     rq->fence.context, rq->fence.seqno,
+		     inflight->fence.context, inflight->fence.seqno,
+		     inflight->sched.attr.priority);
+
+	sched_engine->queue_priority_hint = prio;
+
+	/*
+	 * Allow preemption of low -> normal -> high, but we do
+	 * not allow low priority tasks to preempt other low priority
+	 * tasks under the impression that latency for low priority
+	 * tasks does not matter (as much as background throughput),
+	 * so kiss.
+	 */
+	if (prio >= max(I915_PRIORITY_NORMAL, rq_prio(inflight)))
+		tasklet_hi_schedule(&engine->execlists.tasklet);
+
+unlock:
+	rcu_read_unlock();
+}
+
 static void execlists_set_default_submission(struct intel_engine_cs *engine)
 {
 	engine->submit_request = execlists_submit_request;
 	engine->sched_engine->schedule = i915_schedule;
+	engine->sched_engine->kick_backend = kick_execlists;
 	engine->execlists.tasklet.callback = execlists_submission_tasklet;
 }
 
@@ -3702,6 +3753,7 @@ intel_execlists_create_virtual(struct intel_engine_cs **siblings,
 	ve->base.request_alloc = execlists_request_alloc;
 
 	ve->base.sched_engine->schedule = i915_schedule;
+	ve->base.sched_engine->kick_backend = kick_execlists;
 	ve->base.submit_request = virtual_submit_request;
 	ve->base.bond_execute = virtual_bond_execute;