Re: [RFC PATCH v1 3/5] media: tegra-video: Move PM runtime handle to streaming

[Sowjanya Komatineni]

On 4/28/20 6:59 AM, Dmitry Osipenko wrote:
> External email: Use caution opening links or attachments
>
>
> 28.04.2020 07:20, Sowjanya Komatineni ÐÐÑÐÑ:
> > diff --git a/drivers/staging/media/tegra-video/csi.c b/drivers/staging/media/tegra-video/csi.c
> > index b3dd0c3..29ccdae 100644
> > --- a/drivers/staging/media/tegra-video/csi.c
> > +++ b/drivers/staging/media/tegra-video/csi.c
> > @@ -272,8 +272,25 @@ static int tegra_csi_s_stream(struct v4l2_subdev *subdev, int enable)
> >        struct tegra_vi_channel *chan = v4l2_get_subdev_hostdata(subdev);
> >        struct tegra_csi_channel *csi_chan = to_csi_chan(subdev);
> >        struct tegra_csi *csi = csi_chan->csi;
> > +     int ret;
> > +
> > +     if (enable && atomic_add_return(1, &csi->clk_refcnt) == 1) {
> > +             ret = pm_runtime_get_sync(csi->dev);
> > +             if (ret < 0) {
> > +                     dev_err(csi->dev,
> > +                             "failed to get runtime PM: %d\n", ret);
> > +                     pm_runtime_put_noidle(csi->dev);
> > +                     atomic_dec(&csi->clk_refcnt);
> > +                     return ret;
> > +             }
> > +     }
> > +
> > +     ret = csi->ops->csi_streaming(csi_chan, chan->pg_mode, enable);
> >
> > -     return csi->ops->csi_streaming(csi_chan, chan->pg_mode, enable);
> > +     if ((ret < 0 || !enable) && atomic_dec_and_test(&csi->clk_refcnt))
> > +             pm_runtime_put_sync(csi->dev);
> Runtime PM maintains its own refcount, why these
> clk_refcnt/power_on_refcnt are needed?

Streaming is per channel and we can't turn power/clocks off while other 
channels may still be running.