drm/i915/gt: Always check to enable timeslicing if not submitting

We may choose not to submit for a number of reasons, yet not fill both
ELSP. In which case we must start timeslicing (there will be no ACK
event on which to hook the start) if the queue would benefit from the
currently active context being evicted.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200605122334.2798-2-chris@chris-wilson.co.uk

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

@@ -2362,10 +2362,8 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 				if (last->context == rq->context)
 					goto done;
 
-				if (i915_request_has_sentinel(last)) {
-					start_timeslice(engine, rq_prio(rq));
+				if (i915_request_has_sentinel(last))
 					goto done;
-				}
 
 				/*
 				 * If GVT overrides us we only ever submit
@@ -2446,6 +2444,7 @@ static void execlists_dequeue(struct intel_engine_cs *engine)
 		set_preempt_timeout(engine, *active);
 		execlists_submit_ports(engine);
 	} else {
+		start_timeslice(engine, execlists->queue_priority_hint);
 skip_submit:
 		ring_set_paused(engine, 0);
 	}