drm/i915: Assert the local engine->wakeref is active

Due to the asynchronous tasklet and recursive GT wakeref, it may happen
that we submit to the engine (underneath it's own wakeref) prior to the
central wakeref being marked as taken. Switch to checking the local wakeref
for greater consistency.

Fixes: 79ffac85 ("drm/i915: Invert the GEM wakeref hierarchy")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190503115225.30831-3-chris@chris-wilson.co.uk

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

@@ -1090,6 +1090,9 @@ bool intel_engine_is_idle(struct intel_engine_cs *engine)
 	if (i915_reset_failed(engine->i915))
 		return true;
 
+	if (!intel_wakeref_active(&engine->wakeref))
+		return true;
+
 	/* Waiting to drain ELSP? */
 	if (READ_ONCE(engine->execlists.active)) {
 		struct tasklet_struct *t = &engine->execlists.tasklet;

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

@@ -535,7 +535,7 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
 	 * that all ELSP are drained i.e. we have processed the CSB,
 	 * before allowing ourselves to idle and calling intel_runtime_pm_put().
 	 */
-	GEM_BUG_ON(!engine->i915->gt.awake);
+	GEM_BUG_ON(!intel_wakeref_active(&engine->wakeref));
 
 	/*
 	 * ELSQ note: the submit queue is not cleared after being submitted
@@ -1085,7 +1085,7 @@ static void execlists_submission_tasklet(unsigned long data)
 
 	GEM_TRACE("%s awake?=%d, active=%x\n",
 		  engine->name,
-		  !!engine->i915->gt.awake,
+		  !!intel_wakeref_active(&engine->wakeref),
 		  engine->execlists.active);
 
 	spin_lock_irqsave(&engine->timeline.lock, flags);