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SubjectRe: [RFC][PATCH 13/15] videobuf2: do not sync buffers for DMABUF queues
On (20/01/10 11:30), Hans Verkuil wrote:
[..]
> > diff --git a/drivers/media/common/videobuf2/videobuf2-v4l2.c b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > index 1762849288ae..2b9d3318e6fb 100644
> > --- a/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > +++ b/drivers/media/common/videobuf2/videobuf2-v4l2.c
> > @@ -341,8 +341,22 @@ static void set_buffer_cache_hints(struct vb2_queue *q,
> > struct vb2_buffer *vb,
> > struct v4l2_buffer *b)
> > {
> > - vb->need_cache_sync_on_prepare = 1;
> > + /*
> > + * DMA exporter should take care of cache syncs, so we can avoid
> > + * explicit ->prepare()/->finish() syncs.
> > + */
> > + if (q->memory == VB2_MEMORY_DMABUF) {
> > + vb->need_cache_sync_on_finish = 0;
> > + vb->need_cache_sync_on_prepare = 0;
> > + return;
> > + }
> >
> > + /*
> > + * For other ->memory types we always need ->prepare() cache
> > + * sync. ->finish() cache sync, however, can be avoided when queue
> > + * direction is TO_DEVICE.
> > + */
> > + vb->need_cache_sync_on_prepare = 1;
>
> I'm trying to remember: what needs to be done in prepare()
> for a capture buffer? I thought that for capture you only
> needed to invalidate the cache in finish(), but nothing needs
> to be done in the prepare().

Hmm. Not sure. A precaution in case if user-space wrote to that buffer?

+ if (q->dma_dir == DMA_FROM_DEVICE)
+ q->need_cache_sync_on_prepare = 0;

?

-ss

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