drm/i915: Onion unwind for intel_init_ring_common()

Rather than call intel_engine_cleanup() with a partially constructed
engine, unwind the error during intel_init_ring_common().
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170403113426.25707-2-chris@chris-wilson.co.ukReviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1259,6 +1259,8 @@ static int init_phys_status_page(struct intel_engine_cs *engine)
 {
 	struct drm_i915_private *dev_priv = engine->i915;
 
+	GEM_BUG_ON(engine->id != RCS);
+
 	dev_priv->status_page_dmah =
 		drm_pci_alloc(&dev_priv->drm, PAGE_SIZE, PAGE_SIZE);
 	if (!dev_priv->status_page_dmah)
@@ -1481,76 +1483,69 @@ static void intel_ring_context_unpin(struct intel_engine_cs *engine,
 static int intel_init_ring_buffer(struct intel_engine_cs *engine)
 {
 	struct intel_ring *ring;
-	int ret;
-
-	WARN_ON(engine->buffer);
+	int err;
 
 	intel_engine_setup_common(engine);
 
-	ret = intel_engine_init_common(engine);
-	if (ret)
-		goto error;
+	err = intel_engine_init_common(engine);
+	if (err)
+		goto err;
 
-	if (HWS_NEEDS_PHYSICAL(engine->i915)) {
-		WARN_ON(engine->id != RCS);
-		ret = init_phys_status_page(engine);
-		if (ret)
-			goto error;
-	} else {
-		ret = init_status_page(engine);
-		if (ret)
-			goto error;
-	}
+	if (HWS_NEEDS_PHYSICAL(engine->i915))
+		err = init_phys_status_page(engine);
+	else
+		err = init_status_page(engine);
+	if (err)
+		goto err;
 
 	ring = intel_engine_create_ring(engine, 32 * PAGE_SIZE);
 	if (IS_ERR(ring)) {
-		ret = PTR_ERR(ring);
-		goto error;
+		err = PTR_ERR(ring);
+		goto err_hws;
 	}
 
 	/* Ring wraparound at offset 0 sometimes hangs. No idea why. */
-	ret = intel_ring_pin(ring, engine->i915, I915_GTT_PAGE_SIZE);
-	if (ret) {
-		intel_ring_free(ring);
-		goto error;
-	}
+	err = intel_ring_pin(ring, engine->i915, I915_GTT_PAGE_SIZE);
+	if (err)
+		goto err_ring;
+
+	GEM_BUG_ON(engine->buffer);
 	engine->buffer = ring;
 
 	return 0;
 
-error:
-	intel_engine_cleanup(engine);
-	return ret;
+err_ring:
+	intel_ring_free(ring);
+err_hws:
+	if (HWS_NEEDS_PHYSICAL(engine->i915))
+		cleanup_phys_status_page(engine);
+	else
+		cleanup_status_page(engine);
+err:
+	intel_engine_cleanup_common(engine);
+	return err;
 }
 
 void intel_engine_cleanup(struct intel_engine_cs *engine)
 {
-	struct drm_i915_private *dev_priv;
-
-	dev_priv = engine->i915;
+	struct drm_i915_private *dev_priv = engine->i915;
 
-	if (engine->buffer) {
-		WARN_ON(INTEL_GEN(dev_priv) > 2 &&
-			(I915_READ_MODE(engine) & MODE_IDLE) == 0);
+	WARN_ON(INTEL_GEN(dev_priv) > 2 &&
+		(I915_READ_MODE(engine) & MODE_IDLE) == 0);
 
-		intel_ring_unpin(engine->buffer);
-		intel_ring_free(engine->buffer);
-		engine->buffer = NULL;
-	}
+	intel_ring_unpin(engine->buffer);
+	intel_ring_free(engine->buffer);
 
 	if (engine->cleanup)
 		engine->cleanup(engine);
 
-	if (HWS_NEEDS_PHYSICAL(dev_priv)) {
-		WARN_ON(engine->id != RCS);
+	if (HWS_NEEDS_PHYSICAL(dev_priv))
 		cleanup_phys_status_page(engine);
-	} else {
+	else
 		cleanup_status_page(engine);
-	}
 
 	intel_engine_cleanup_common(engine);
 
-	engine->i915 = NULL;
 	dev_priv->engine[engine->id] = NULL;
 	kfree(engine);
 }