Re: [RFC PATCH v6 6/9] media: tegra: Add Tegra210 Video input driver

[Sowjanya Komatineni]

On 4/6/20 1:53 PM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 06.04.2020 23:50, Sowjanya Komatineni ÐÐÑÐÑ:
> > On 4/6/20 1:45 PM, Dmitry Osipenko wrote:
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > 04.04.2020 04:25, Sowjanya Komatineni ÐÐÑÐÑ:
> > > > +static int chan_capture_kthread_start(void *data)
> > > > +{
> > > > +     struct tegra_vi_channel *chan = data;
> > > > +     struct tegra_channel_buffer *buf;
> > > > +     int err = 0;
> > > > +     int caps_inflight;
> > > > +
> > > > +     set_freezable();
> > > > +
> > > > +     while (1) {
> > > > +             try_to_freeze();
> > > > +
> > > > +             wait_event_interruptible(chan->start_wait,
> > > > +                                      !list_empty(&chan->capture) ||
> > > > +                                      kthread_should_stop());
> > > > +             /*
> > > > +              * Frame start and MW_ACK_DONE syncpoint condition
> > > > FIFOs are
> > > > +              * of max depth 2. So make sure max 2 capture requests are
> > > > +              * in process by the hardware at a time.
> > > > +              */
> > > > +             while (!(kthread_should_stop() ||
> > > > list_empty(&chan->capture))) {
> > > > +                     caps_inflight = chan->capture_reqs -
> > > > chan->sequence;
> > > > +                     /*
> > > > +                      * Source is not streaming if error is non-zero.
> > > > +                      * So, do not dequeue buffers on capture error
> > > > or when
> > > > +                      * syncpoint requests in FIFO are full.
> > > > +                      */
> > > > +                     if (err || caps_inflight >= SYNCPT_FIFO_DEPTH)
> > > > +                             break;
> > > Am I understanding correctly that this thread will take 100% CPU,
> > > spinning here, if more than 2 frame-captures queued?
> > on more than 2 frames captures, it breaks thread and on next wakeup it
> > continues
> The wait_event() won't wait if condition is true.
condition is checked when waitqueue is woken up