drm/i915: Dump the engine state before declaring wedged from wait_for_engines()

If wait_for_engines() fails and we resort to declaring the HW wedged,
dump the engine state for debugging.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171211194135.27095-2-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_gem.c

@@ -3534,7 +3534,18 @@ static int wait_for_timeline(struct i915_gem_timeline *tl, unsigned int flags)
 static int wait_for_engines(struct drm_i915_private *i915)
 {
 	if (wait_for(intel_engines_are_idle(i915), I915_IDLE_ENGINES_TIMEOUT)) {
-		DRM_ERROR("Failed to idle engines, declaring wedged!\n");
+		dev_err(i915->drm.dev,
+			"Failed to idle engines, declaring wedged!\n");
+		if (drm_debug & DRM_UT_DRIVER) {
+			struct drm_printer p = drm_debug_printer(__func__);
+			struct intel_engine_cs *engine;
+			enum intel_engine_id id;
+
+			for_each_engine(engine, i915, id)
+				intel_engine_dump(engine, &p,
+						  "%s", engine->name);
+		}
+
 		i915_gem_set_wedged(i915);
 		return -EIO;
 	}