drm/i915: Reset sched_engine.no_priolist immediately after dequeue

Rather than touching schedule state in the generic PM code, reset the
priolist allocation when empty in the submission code. Add a wrapper
function to do this and update the backends to call it in the correct
place.

v3:
 (Jason Ekstrand)
  Update patch commit message with a better description
Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210618010638.98941-4-matthew.brost@intel.com

drivers/gpu/drm/i915/gt/intel_engine_pm.c

@@ -280,8 +280,6 @@ static int __engine_park(struct intel_wakeref *wf)
 	if (engine->park)
 		engine->park(engine);
 
-	engine->sched_engine->no_priolist = false;
-
 	/* While gt calls i915_vma_parked(), we have to break the lock cycle */
 	intel_gt_pm_put_async(engine->gt);
 	return 0;

drivers/gpu/drm/i915/gt/intel_execlists_submission.c

@@ -1553,6 +1553,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 	 * interrupt for secondary ports).
 	 */
 	sched_engine->queue_priority_hint = queue_prio(sched_engine);
+	i915_sched_engine_reset_on_empty(sched_engine);
 	spin_unlock(&engine->active.lock);
 
 	/*

drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c

@@ -263,6 +263,8 @@ static void guc_submission_tasklet(struct tasklet_struct *t)
 
 	__guc_dequeue(engine);
 
+	i915_sched_engine_reset_on_empty(engine->sched_engine);
+
 	spin_unlock_irqrestore(&engine->active.lock, flags);
 }
 

drivers/gpu/drm/i915/i915_scheduler.h

@@ -72,6 +72,13 @@ i915_sched_engine_is_empty(struct i915_sched_engine *sched_engine)
 	return RB_EMPTY_ROOT(&sched_engine->queue.rb_root);
 }
 
+static inline void
+i915_sched_engine_reset_on_empty(struct i915_sched_engine *sched_engine)
+{
+	if (i915_sched_engine_is_empty(sched_engine))
+		sched_engine->no_priolist = false;
+}
+
 void i915_request_show_with_schedule(struct drm_printer *m,
 				     const struct i915_request *rq,
 				     const char *prefix,