drm/i915: Cancel reset preparations on failed resets

Our reset handling has a retry layer further up in the
chain. As we have told the engine to prepare for reset,
and failed it, make sure to remove that preparation so
that the next attempted reset has a clean slate by triggering
another full prepare cycle for the engines.

v2: ret as int, simplified cleanup (Chris)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20180605160357.32591-1-mika.kuoppala@linux.intel.com

drivers/gpu/drm/i915/intel_uncore.c

@@ -2093,21 +2093,25 @@ static int gen8_reset_engines(struct drm_i915_private *dev_priv,
 {
 	struct intel_engine_cs *engine;
 	unsigned int tmp;
+	int ret;
 
-	for_each_engine_masked(engine, dev_priv, engine_mask, tmp)
-		if (gen8_reset_engine_start(engine))
+	for_each_engine_masked(engine, dev_priv, engine_mask, tmp) {
+		if (gen8_reset_engine_start(engine)) {
+			ret = -EIO;
 			goto not_ready;
+		}
+	}
 
 	if (INTEL_GEN(dev_priv) >= 11)
-		return gen11_reset_engines(dev_priv, engine_mask);
+		ret = gen11_reset_engines(dev_priv, engine_mask);
 	else
-		return gen6_reset_engines(dev_priv, engine_mask);
+		ret = gen6_reset_engines(dev_priv, engine_mask);
 
 not_ready:
 	for_each_engine_masked(engine, dev_priv, engine_mask, tmp)
 		gen8_reset_engine_cancel(engine);
 
-	return -EIO;
+	return ret;
 }
 
 typedef int (*reset_func)(struct drm_i915_private *, unsigned engine_mask);