drm/i915: Check whether the ring is initialised prior to dispatch

Rather than use the magic feature tests HAS_BLT/HAS_BSD just check
whether the ring we are about to dispatch the execbuffer on is
initialised.

v2: Use intel_ring_initialized()

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_execbuffer.c

@@ -1064,24 +1064,21 @@ i915_gem_do_execbuffer(struct drm_device *dev, void *data,
 		ring = &dev_priv->ring[RCS];
 		break;
 	case I915_EXEC_BSD:
-		if (!HAS_BSD(dev)) {
-			DRM_DEBUG("execbuf with invalid ring (BSD)\n");
-			return -EINVAL;
-		}
 		ring = &dev_priv->ring[VCS];
 		break;
 	case I915_EXEC_BLT:
-		if (!HAS_BLT(dev)) {
-			DRM_DEBUG("execbuf with invalid ring (BLT)\n");
-			return -EINVAL;
-		}
 		ring = &dev_priv->ring[BCS];
 		break;
 	default:
 		DRM_DEBUG("execbuf with unknown ring: %d\n",
 			  (int)(args->flags & I915_EXEC_RING_MASK));
 		return -EINVAL;
 	}
+	if (!intel_ring_initialized(ring)) {
+		DRM_DEBUG("execbuf with invalid ring: %d\n",
+			  (int)(args->flags & I915_EXEC_RING_MASK));
+		return -EINVAL;
+	}
 
 	mode = args->flags & I915_EXEC_CONSTANTS_MASK;
 	mask = I915_EXEC_CONSTANTS_MASK;