Re: [PATCH v2 37/66] media: sun6i-csi: Move power management to runtime pm in capture

Sakari Ailus
2022-02-15T21:21:13Z

Hi Paul,

On Tue, Feb 15, 2022 at 11:21:17AM +0100, Paul Kocialkowski wrote:
> Hi Laurent,
>
> On Tue 15 Feb 22, 12:04, Laurent Pinchart wrote:
> > Hi Paul,
> >
> > On Tue, Feb 15, 2022 at 10:56:22AM +0100, Paul Kocialkowski wrote:
> > > On Mon 14 Feb 22, 20:30, Sakari Ailus wrote:
> > > > On Sat, Feb 05, 2022 at 07:54:00PM +0100, Paul Kocialkowski wrote:
> > > > > Let's just enable the module when we start using it (at stream on)
> > > > > and benefit from runtime pm instead of enabling it at first open.
> > > > >
> > > > > Also reorder the call to v4l2_pipeline_pm_get.
> > > > >
> > > > > Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
> > > >
> > > > Nice patch!
> > >
> > > Thanks!
> > >
> > > > Do you still need v4l2_pipeline_pm_put()? Removing it would be a separate
> > > > patch of course.
> > >
> > > My understanding is that this is still useful if there are drivers in the
> > > pipeline that rely on s_power instead of rpm (a typical case could be an
> > > old sensor driver). So that's why this is kept around, but all other components
> > > of the pipeline (isp/csi/mipi csi-2) are using rpm now.
> >
> > If that's not the case on your test platforms, I think it would be
> > better to drop support for this old API, and convert drivers that still
> > use .s_power() if someone needs to use one on an Allwinner platform.
>
> I agree this is the path to follow but it feels like we're not quite there
> yet and a bunch of driver were not converted at this point, including some
> popular ones like ov5640, which I know for sure is used with Allwinner devices.
>
> Honestly I'd be happy to get rid of these legacy functions as soon as the
> transition is done, but doing it now would mean breaking a significant number
> of use cases (which I'm trying to avoid here despite all the changes).
>
> I definitely wouldn't be confident making that transition here and it
> probably wouldn't be a good idea to make that a requirement to merge this
> (already quite big) series.
>
> What do you think?

Feel free to keep it if you prefer that.

All sensor drivers that implement s_power are old but there are quite a few
of them. Converting them isn't trivial so best done by someone who has
access to the hardware.

--
Regards,

Sakari Ailus