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Commit 251a79f8 authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
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[media] vb2: use dma_map_sg_attrs to prevent unnecessary sync 



By default dma_map_sg syncs the mapped buffer to the device. But
buf_prepare expects a buffer syncs for the cpu and the buffer
will be synced to the device in the prepare memop.

The reverse is true for dma_unmap_sg, buf_finish and the finish
memop.

To prevent unnecessary syncs we ask dma_(un)map_sg to skip the
sync.

Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Acked-by: default avatarPawel Osciak <pawel@osciak.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@osg.samsung.com>
parent f5294f45

drivers/media/v4l2-core/videobuf2-dma-contig.c

+20 −4
Original line number Diff line number Diff line
@@ -511,7 +511,15 @@ static void vb2_dc_put_userptr(void *buf_priv) 
	struct sg_table *sgt = buf->dma_sgt;



	if (sgt) {

		dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);

		DEFINE_DMA_ATTRS(attrs);



		dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

		/*

		 * No need to sync to CPU, it's already synced to the CPU

		 * since the finish() memop will have been called before this.

		 */

		dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,

				   buf->dma_dir, &attrs);

		if (!vma_is_io(buf->vma))

			vb2_dc_sgt_foreach_page(sgt, vb2_dc_put_dirty_page);
@@ -568,6 +576,9 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr, 
	struct sg_table *sgt;

	unsigned long contig_size;

	unsigned long dma_align = dma_get_cache_alignment();

	DEFINE_DMA_ATTRS(attrs);



	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);



	/* Only cache aligned DMA transfers are reliable */

	if (!IS_ALIGNED(vaddr | size, dma_align)) {
@@ -654,8 +665,12 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr, 
	kfree(pages);

	pages = NULL;



	sgt->nents = dma_map_sg(buf->dev, sgt->sgl, sgt->orig_nents,

		buf->dma_dir);

	/*

	 * No need to sync to the device, this will happen later when the

	 * prepare() memop is called.

	 */

	sgt->nents = dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,

				      buf->dma_dir, &attrs);

	if (sgt->nents <= 0) {

		pr_err("failed to map scatterlist\n");

		ret = -EIO;
@@ -677,7 +692,8 @@ static void *vb2_dc_get_userptr(void *alloc_ctx, unsigned long vaddr, 
	return buf;



fail_map_sg:

	dma_unmap_sg(buf->dev, sgt->sgl, sgt->orig_nents, buf->dma_dir);

	dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->orig_nents,

			   buf->dma_dir, &attrs);



fail_sgt_init:

	if (!vma_is_io(buf->vma))

drivers/media/v4l2-core/videobuf2-dma-sg.c

+27 −6
Original line number Diff line number Diff line
@@ -107,6 +107,9 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size, 
	struct sg_table *sgt;

	int ret;

	int num_pages;

	DEFINE_DMA_ATTRS(attrs);



	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);



	if (WARN_ON(alloc_ctx == NULL))

		return NULL;
@@ -140,9 +143,13 @@ static void *vb2_dma_sg_alloc(void *alloc_ctx, unsigned long size, 
	buf->dev = get_device(conf->dev);



	sgt = &buf->sg_table;

	if (dma_map_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir) == 0)

	/*

	 * No need to sync to the device, this will happen later when the

	 * prepare() memop is called.

	 */

	if (dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->nents,

			     buf->dma_dir, &attrs) == 0)

		goto fail_map;

	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);



	buf->handler.refcount = &buf->refcount;

	buf->handler.put = vb2_dma_sg_put;
@@ -175,9 +182,13 @@ static void vb2_dma_sg_put(void *buf_priv) 
	int i = buf->num_pages;



	if (atomic_dec_and_test(&buf->refcount)) {

		DEFINE_DMA_ATTRS(attrs);



		dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);

		dprintk(1, "%s: Freeing buffer of %d pages\n", __func__,

			buf->num_pages);

		dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);

		dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->nents,

				   buf->dma_dir, &attrs);

		if (buf->vaddr)

			vm_unmap_ram(buf->vaddr, buf->num_pages);

		sg_free_table(buf->dma_sgt);
@@ -228,6 +239,9 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr, 
	int num_pages_from_user;

	struct vm_area_struct *vma;

	struct sg_table *sgt;

	DEFINE_DMA_ATTRS(attrs);



	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);



	buf = kzalloc(sizeof *buf, GFP_KERNEL);

	if (!buf)
@@ -296,9 +310,13 @@ static void *vb2_dma_sg_get_userptr(void *alloc_ctx, unsigned long vaddr, 
		goto userptr_fail_alloc_table_from_pages;



	sgt = &buf->sg_table;

	if (dma_map_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir) == 0)

	/*

	 * No need to sync to the device, this will happen later when the

	 * prepare() memop is called.

	 */

	if (dma_map_sg_attrs(buf->dev, sgt->sgl, sgt->nents,

			     buf->dma_dir, &attrs) == 0)

		goto userptr_fail_map;

	dma_sync_sg_for_cpu(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);

	return buf;



userptr_fail_map:
@@ -327,10 +345,13 @@ static void vb2_dma_sg_put_userptr(void *buf_priv) 
	struct vb2_dma_sg_buf *buf = buf_priv;

	struct sg_table *sgt = &buf->sg_table;

	int i = buf->num_pages;

	DEFINE_DMA_ATTRS(attrs);



	dma_set_attr(DMA_ATTR_SKIP_CPU_SYNC, &attrs);



	dprintk(1, "%s: Releasing userspace buffer of %d pages\n",

	       __func__, buf->num_pages);

	dma_unmap_sg(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir);

	dma_unmap_sg_attrs(buf->dev, sgt->sgl, sgt->nents, buf->dma_dir, &attrs);

	if (buf->vaddr)

		vm_unmap_ram(buf->vaddr, buf->num_pages);

	sg_free_table(buf->dma_sgt);