Commit 2cc1802f authored Jan 24, 2019 by Pawel Osciak Committed by Mauro Carvalho Chehab Jan 31, 2019

media: vb2: Keep dma-buf buffers mapped until they are freed

When using vb2 for video decoding, dequeued capture buffers may still
be accessed by the hardware: this is the case when they are used as
reference frames for decoding subsequent frames.

When the buffer is imported with dma-buf, it needs to be mapped before
access. Until now, it was mapped when queuing and unmapped when
dequeuing, which doesn't work for access as a reference frames.

One way to solve this would be to map the buffer again when it is
needed as a reference, but the mapping/unmapping operations can
seriously impact performance. As a result, map the buffer once (when it
is first needed when queued) and keep it mapped until it is freed.

Reviewed-on: https://chromium-review.googlesource.com/334103


[Paul: Updated for mainline and changed commit message]

Signed-off-by: Pawel Osciak <posciak@chromium.org>
Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

parent 826ef750

drivers/media/common/videobuf2/videobuf2-core.c

+3 −8

Original line number	Diff line number	Diff line
		@@ -1196,6 +1196,9 @@ static int __prepare_dmabuf(struct vb2_buffer *vb)
		* userspace knows sooner rather than later if the dma-buf map fails.
		*/
		for (plane = 0; plane < vb->num_planes; ++plane) {
		if (vb->planes[plane].dbuf_mapped)
		continue;

		ret = call_memop(vb, map_dmabuf, vb->planes[plane].mem_priv);
		if (ret) {
		dprintk(1, "failed to map dmabuf for plane %d\n",
		@@ -1758,14 +1761,6 @@ static void __vb2_dqbuf(struct vb2_buffer *vb)

		vb->state = VB2_BUF_STATE_DEQUEUED;

		/* unmap DMABUF buffer */
		if (q->memory == VB2_MEMORY_DMABUF)
		for (i = 0; i < vb->num_planes; ++i) {
		if (!vb->planes[i].dbuf_mapped)
		continue;
		call_void_memop(vb, unmap_dmabuf, vb->planes[i].mem_priv);
		vb->planes[i].dbuf_mapped = 0;
		}
		call_void_bufop(q, init_buffer, vb);
		}

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