drm/i915: Allocate rings from stolen

If we have stolen available, make use of it for ringbuffer allocation.
Previously this was restricted to !llc platforms, as writing to stolen
requires a GGTT mapping - but now that we have partial mappable support,
the mappable aperture isn't quite so precious so we can use it more
freely and ringbuffers are a good user for the otherwise wasted stolen.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20160818161718.27187-18-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/intel_ringbuffer.c

@@ -1952,10 +1952,8 @@ intel_ring_create_vma(struct drm_i915_private *dev_priv, int size)
 	struct drm_i915_gem_object *obj;
 	struct i915_vma *vma;
 
-	obj = ERR_PTR(-ENODEV);
-	if (!HAS_LLC(dev_priv))
-		obj = i915_gem_object_create_stolen(&dev_priv->drm, size);
-	if (IS_ERR(obj))
+	obj = i915_gem_object_create_stolen(&dev_priv->drm, size);
+	if (!obj)
 		obj = i915_gem_object_create(&dev_priv->drm, size);
 	if (IS_ERR(obj))
 		return ERR_CAST(obj);