drm: use dma_fence_unwrap_merge() in drm_syncobj

The unwrap merge function is now intended for this use case.
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20220518135844.3338-6-christian.koenig@amd.com

drivers/gpu/drm/drm_syncobj.c

@@ -184,6 +184,7 @@
  */
 
 #include <linux/anon_inodes.h>
+#include <linux/dma-fence-unwrap.h>
 #include <linux/file.h>
 #include <linux/fs.h>
 #include <linux/sched/signal.h>
@@ -853,57 +854,12 @@ drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev, void *data,
 					&args->handle);
 }
 
-
-/*
- * Try to flatten a dma_fence_chain into a dma_fence_array so that it can be
- * added as timeline fence to a chain again.
- */
-static int drm_syncobj_flatten_chain(struct dma_fence **f)
-{
-	struct dma_fence_chain *chain = to_dma_fence_chain(*f);
-	struct dma_fence *tmp, **fences;
-	struct dma_fence_array *array;
-	unsigned int count;
-
-	if (!chain)
-		return 0;
-
-	count = 0;
-	dma_fence_chain_for_each(tmp, &chain->base)
-		++count;
-
-	fences = kmalloc_array(count, sizeof(*fences), GFP_KERNEL);
-	if (!fences)
-		return -ENOMEM;
-
-	count = 0;
-	dma_fence_chain_for_each(tmp, &chain->base)
-		fences[count++] = dma_fence_get(tmp);
-
-	array = dma_fence_array_create(count, fences,
-				       dma_fence_context_alloc(1),
-				       1, false);
-	if (!array)
-		goto free_fences;
-
-	dma_fence_put(*f);
-	*f = &array->base;
-	return 0;
-
-free_fences:
-	while (count--)
-		dma_fence_put(fences[count]);
-
-	kfree(fences);
-	return -ENOMEM;
-}
-
 static int drm_syncobj_transfer_to_timeline(struct drm_file *file_private,
 					    struct drm_syncobj_transfer *args)
 {
 	struct drm_syncobj *timeline_syncobj = NULL;
+	struct dma_fence *fence, *tmp;
 	struct dma_fence_chain *chain;
-	struct dma_fence *fence;
 	int ret;
 
 	timeline_syncobj = drm_syncobj_find(file_private, args->dst_handle);
@@ -912,13 +868,14 @@ static int drm_syncobj_transfer_to_timeline(struct drm_file *file_private,
 	}
 	ret = drm_syncobj_find_fence(file_private, args->src_handle,
 				     args->src_point, args->flags,
-				     &fence);
+				     &tmp);
 	if (ret)
 		goto err_put_timeline;
 
-	ret = drm_syncobj_flatten_chain(&fence);
-	if (ret)
-		goto err_free_fence;
+	fence = dma_fence_unwrap_merge(tmp);
+	dma_fence_put(tmp);
+	if (!fence)
+		goto err_put_timeline;
 
 	chain = dma_fence_chain_alloc();
 	if (!chain) {