drm/i915/selftests: Wait only on the expected barrier

Wait on only the last request on the kernel_context after emitting a
barrier so that we do not wait for everything in general and by doing so
cause an accidental emission of the barrier!

Bugzilla; https://bugs.freedesktop.org/show_bug.cgi?id=112405Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191129103455.744389-1-chris@chris-wilson.co.uk

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

@@ -11,6 +11,28 @@
 #include "intel_gt_requests.h"
 #include "i915_selftest.h"
 
+static int timeline_sync(struct intel_timeline *tl)
+{
+	struct dma_fence *fence;
+	long timeout;
+
+	fence = i915_active_fence_get(&tl->last_request);
+	if (!fence)
+		return 0;
+
+	timeout = dma_fence_wait_timeout(fence, true, HZ / 2);
+	dma_fence_put(fence);
+	if (timeout < 0)
+		return timeout;
+
+	return 0;
+}
+
+static int engine_sync_barrier(struct intel_engine_cs *engine)
+{
+	return timeline_sync(engine->kernel_context->timeline);
+}
+
 struct pulse {
 	struct i915_active active;
 	struct kref kref;
@@ -90,7 +112,7 @@ static int __live_idle_pulse(struct intel_engine_cs *engine,
 
 	GEM_BUG_ON(!llist_empty(&engine->barrier_tasks));
 
-	if (intel_gt_retire_requests_timeout(engine->gt, HZ / 5)) {
+	if (engine_sync_barrier(engine)) {
 		struct drm_printer m = drm_err_printer("pulse");
 
 		pr_err("%s: no heartbeat pulse?\n", engine->name);