drm/i915: Consolidate common error handling in intel_pin_and_map_ringbuffer_obj

After we pin the ringbuffer into the GGTT, all error paths need to unpin
it again. Move this common step into one block, and make the unable to
iomap error code consistent (i.e. treat it as out of memory to avoid
confusing it with a invalid argument).

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1460113874-17366-3-git-send-email-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -2126,15 +2126,13 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 			return ret;
 
 		ret = i915_gem_object_set_to_cpu_domain(obj, true);
-		if (ret) {
-			i915_gem_object_ggtt_unpin(obj);
-			return ret;
-		}
+		if (ret)
+			goto err_unpin;
 
 		ringbuf->virtual_start = vmap_obj(obj);
 		if (ringbuf->virtual_start == NULL) {
-			i915_gem_object_ggtt_unpin(obj);
-			return -ENOMEM;
+			ret = -ENOMEM;
+			goto err_unpin;
 		}
 	} else {
 		ret = i915_gem_obj_ggtt_pin(obj, PAGE_SIZE, PIN_MAPPABLE);
@@ -2142,10 +2140,8 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 			return ret;
 
 		ret = i915_gem_object_set_to_gtt_domain(obj, true);
-		if (ret) {
-			i915_gem_object_ggtt_unpin(obj);
-			return ret;
-		}
+		if (ret)
+			goto err_unpin;
 
 		/* Access through the GTT requires the device to be awake. */
 		assert_rpm_wakelock_held(dev_priv);
@@ -2153,14 +2149,17 @@ int intel_pin_and_map_ringbuffer_obj(struct drm_device *dev,
 		ringbuf->virtual_start = ioremap_wc(ggtt->mappable_base +
 						    i915_gem_obj_ggtt_offset(obj), ringbuf->size);
 		if (ringbuf->virtual_start == NULL) {
-			i915_gem_object_ggtt_unpin(obj);
-			return -EINVAL;
+			ret = -ENOMEM;
+			goto err_unpin;
 		}
 	}
 
 	ringbuf->vma = i915_gem_obj_to_ggtt(obj);
-
 	return 0;
+
+err_unpin:
+	i915_gem_object_ggtt_unpin(obj);
+	return ret;
 }
 
 static void intel_destroy_ringbuffer_obj(struct intel_ringbuffer *ringbuf)