drm/ttm: remove the backing store if no placement is given

Pipeline removal of the BOs backing store when no placement is given
during validation.
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/353994/?series=73646&rev=1

drivers/gpu/drm/ttm/ttm_bo.c

@@ -1196,6 +1196,18 @@ int ttm_bo_validate(struct ttm_buffer_object *bo,
 	uint32_t new_flags;
 
 	dma_resv_assert_held(bo->base.resv);
+
+	/*
+	 * Remove the backing store if no placement is given.
+	 */
+	if (!placement->num_placement && !placement->num_busy_placement) {
+		ret = ttm_bo_pipeline_gutting(bo);
+		if (ret)
+			return ret;
+
+		return ttm_tt_create(bo, false);
+	}
+
 	/*
 	 * Check whether we need to move buffer.
 	 */