drm/i915/selftests: Flush the active callbacks

Before checking the current i915_active state for the asynchronous work
we submitted, flush any ongoing callback. This ensures that our sampling
is robust and does not sporadically fail due to bad timing as the work
is running on another cpu.

v2: Drop the fence callback sync, retiring under the lock should be good
enough to synchronize with engine_retire() and the
intel_gt_retire_requests() background worker.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191122132404.690440-1-chris@chris-wilson.co.uk

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

@@ -48,20 +48,22 @@ static int context_sync(struct intel_context *ce)
 
 	mutex_lock(&tl->mutex);
 	do {
-		struct dma_fence *fence;
+		struct i915_request *rq;
 		long timeout;
 
-		fence = i915_active_fence_get(&tl->last_request);
-		if (!fence)
+		if (list_empty(&tl->requests))
 			break;
 
-		timeout = dma_fence_wait_timeout(fence, false, HZ / 10);
+		rq = list_last_entry(&tl->requests, typeof(*rq), link);
+		i915_request_get(rq);
+
+		timeout = i915_request_wait(rq, 0, HZ / 10);
 		if (timeout < 0)
 			err = timeout;
 		else
-			i915_request_retire_upto(to_request(fence));
+			i915_request_retire_upto(rq);
 
-		dma_fence_put(fence);
+		i915_request_put(rq);
 	} while (!err);
 	mutex_unlock(&tl->mutex);
 
@@ -273,6 +275,7 @@ static int __live_active_context(struct intel_engine_cs *engine,
 	if (err)
 		goto err;
 
+	/* Wait for the barrier and in the process wait for engine to park */
 	err = context_sync(engine->kernel_context);
 	if (err)
 		goto err;
@@ -282,6 +285,8 @@ static int __live_active_context(struct intel_engine_cs *engine,
 		err = -EINVAL;
 	}
 
+	intel_engine_pm_flush(engine);
+
 	if (intel_engine_pm_is_awake(engine)) {
 		struct drm_printer p = drm_debug_printer(__func__);