drm/i915/selftests: Wait for idle between idle resets as well

Even though we weren't injecting guilty requests to be reset, we could
still fall over the issue of resetting the same request too fast -- where
the GPU refuses to start again. (Although it is interesting to note that
reloading the driver is sufficient, suggesting that we could recover if
we delayed the setup after reset?) Continue to paper over the problem by
adding a small delay by waiting for the engine to idle between tests,
and ensure that the engines are idle before starting the idle tests.

v2: Replace single instance of 50 with a magic macro.

References: 028666793a02 ("drm/i915/selftests: Avoid repeatedly harming the same innocent context")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Michał Winiarski <michal.winiarski@intel.com>
Cc: Michel Thierry <michel.thierry@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180411120346.27618-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/selftests/intel_hangcheck.c

@@ -30,6 +30,8 @@
 #include "mock_context.h"
 #include "mock_drm.h"
 
+#define IGT_IDLE_TIMEOUT 50 /* ms; time to wait after flushing between tests */
+
 struct hang {
 	struct drm_i915_private *i915;
 	struct drm_i915_gem_object *hws;
@@ -454,6 +456,11 @@ static int igt_global_reset(void *arg)
 	return err;
 }
 
+static bool wait_for_idle(struct intel_engine_cs *engine)
+{
+	return wait_for(intel_engine_is_idle(engine), IGT_IDLE_TIMEOUT) == 0;
+}
+
 static int __igt_reset_engine(struct drm_i915_private *i915, bool active)
 {
 	struct intel_engine_cs *engine;
@@ -481,6 +488,13 @@ static int __igt_reset_engine(struct drm_i915_private *i915, bool active)
 		if (active && !intel_engine_can_store_dword(engine))
 			continue;
 
+		if (!wait_for_idle(engine)) {
+			pr_err("%s failed to idle before reset\n",
+			       engine->name);
+			err = -EIO;
+			break;
+		}
+
 		reset_count = i915_reset_count(&i915->gpu_error);
 		reset_engine_count = i915_reset_engine_count(&i915->gpu_error,
 							     engine);
@@ -542,6 +556,19 @@ static int __igt_reset_engine(struct drm_i915_private *i915, bool active)
 				err = -EINVAL;
 				break;
 			}
+
+			if (!wait_for_idle(engine)) {
+				struct drm_printer p =
+					drm_info_printer(i915->drm.dev);
+
+				pr_err("%s failed to idle after reset\n",
+				       engine->name);
+				intel_engine_dump(engine, &p,
+						  "%s\n", engine->name);
+
+				err = -EIO;
+				break;
+			}
 		} while (time_before(jiffies, end_time));
 		clear_bit(I915_RESET_ENGINE + id, &i915->gpu_error.flags);
 
@@ -696,6 +723,13 @@ static int __igt_reset_engines(struct drm_i915_private *i915,
 		    !intel_engine_can_store_dword(engine))
 			continue;
 
+		if (!wait_for_idle(engine)) {
+			pr_err("i915_reset_engine(%s:%s): failed to idle before reset\n",
+			       engine->name, test_name);
+			err = -EIO;
+			break;
+		}
+
 		memset(threads, 0, sizeof(threads));
 		for_each_engine(other, i915, tmp) {
 			struct task_struct *tsk;
@@ -772,6 +806,20 @@ static int __igt_reset_engines(struct drm_i915_private *i915,
 				i915_request_wait(rq, 0, MAX_SCHEDULE_TIMEOUT);
 				i915_request_put(rq);
 			}
+
+			if (!(flags & TEST_SELF) && !wait_for_idle(engine)) {
+				struct drm_printer p =
+					drm_info_printer(i915->drm.dev);
+
+				pr_err("i915_reset_engine(%s:%s):"
+				       " failed to idle after reset\n",
+				       engine->name, test_name);
+				intel_engine_dump(engine, &p,
+						  "%s\n", engine->name);
+
+				err = -EIO;
+				break;
+			}
 		} while (time_before(jiffies, end_time));
 		clear_bit(I915_RESET_ENGINE + id, &i915->gpu_error.flags);
 		pr_info("i915_reset_engine(%s:%s): %lu resets\n",
@@ -981,7 +1029,7 @@ static int wait_for_others(struct drm_i915_private *i915,
 		if (engine == exclude)
 			continue;
 
-		if (wait_for(intel_engine_is_idle(engine), 10))
+		if (!wait_for_idle(engine))
 			return -EIO;
 	}