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

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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>
This commit is contained in:
Pawel Osciak 2019-01-24 07:51:55 -02:00 committed by Mauro Carvalho Chehab
parent 826ef75088
commit 2cc1802f62
1 changed files with 3 additions and 8 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

11
drivers/media/common/videobuf2/videobuf2-core.c
View file

@ -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);
}