Re: [RFC v2 03/11] vb2: Move cache synchronisation from buffer done to dqbuf handler

Laurent Pinchart
2017-03-28T12:54:12Z

Hi Shuah,

On Monday 27 Mar 2017 15:27:36 Shuah Khan wrote:
> On Thu, Dec 15, 2016 at 6:24 PM, Laurent Pinchart wrote:
> > From: Sakari Ailus <sakari.ailus@linux.intel.com>
> >
> > The cache synchronisation may be a time consuming operation and thus not
> > best performed in an interrupt which is a typical context for
> > vb2_buffer_done() calls. This may consume up to tens of ms on some
> > machines, depending on the buffer size.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > ---
> > Changes since v1:
> >
> > - Don't rename the 'i' loop counter to 'plane'
> > ---
> >
> > drivers/media/v4l2-core/videobuf2-core.c | 9 ++++-----
> > 1 file changed, 4 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/media/v4l2-core/videobuf2-core.c
> > b/drivers/media/v4l2-core/videobuf2-core.c index
> > 8ba48703b189..15a83f338072 100644
> > --- a/drivers/media/v4l2-core/videobuf2-core.c
> > +++ b/drivers/media/v4l2-core/videobuf2-core.c
> > @@ -889,7 +889,6 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum
> > vb2_buffer_state state)>
> > {
> > struct vb2_queue *q = vb->vb2_queue;
> > unsigned long flags;
> > - unsigned int plane;
> >
> > if (WARN_ON(vb->state != VB2_BUF_STATE_ACTIVE))
> > return;
> > @@ -910,10 +909,6 @@ void vb2_buffer_done(struct vb2_buffer *vb, enum
> > vb2_buffer_state state)
> > dprintk(4, "done processing on buffer %d, state: %d\n",
> > vb->index, state);
> >
> > - /* sync buffers */
> > - for (plane = 0; plane < vb->num_planes; ++plane)
> > - call_void_memop(vb, finish, vb->planes[plane].mem_priv);
> > -
> > spin_lock_irqsave(&q->done_lock, flags);
> > if (state == VB2_BUF_STATE_QUEUED ||
> > state == VB2_BUF_STATE_REQUEUEING) {
> > @@ -1571,6 +1566,10 @@ static void __vb2_dqbuf(struct vb2_buffer *vb)
> >
> > vb->state = VB2_BUF_STATE_DEQUEUED;
> >
> > + /* sync buffers */
> > + for (i = 0; i < vb->num_planes; ++i)
> > + call_void_memop(vb, finish, vb->planes[i].mem_priv);
> > +
>
> Does this compile?? Where is "i" defined? Looks like it needs to be added
> back in.

It's already defined at the beginning of the __vb2_dqbuf() function.

> > /* unmap DMABUF buffer */
> > if (q->memory == VB2_MEMORY_DMABUF)
> > for (i = 0; i < vb->num_planes; ++i) {