linux-kernel - Re: [PATCH v5] Driver for ON Semi AR0521 camera sensor

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Date:   Tue, 12 Oct 2021 23:30:00 +0300
From:   Sakari Ailus <sakari.ailus@....fi>
To:     Krzysztof Hałasa <khalasa@...p.pl>
Cc:     Jacopo Mondi <jacopo@...ndi.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Matteo Lisi <matteo.lisi@...icam.com>
Subject: Re: [PATCH v5] Driver for ON Semi AR0521 camera sensor

Hi Krzysztof,

On Tue, Oct 12, 2021 at 02:24:17PM +0200, Krzysztof Hałasa wrote:
> Jacopo,
> 
> > I'll pretend I haven't read this not to be dragged in tangential
> > discussions. My whole point was such a commit message is useless as I
> > assume if you submit a driver for inclusion you have tested it.
> 
> Fine, I will remove that very commit comment.
> 
> > I think the clock rate should be assigned in DTS and you should verify
> > it falls in the supported clock ranges.
> 
> Which driver does that, please?
> clk_set_rate() appears to be used by multiple drivers, I was thinking
> I can use it.
> I can see clock frequencies in DTS, but they usually refer to fixed
> clocks (e.g. crystal-based). The clock I use is IMX6QDL_CLK_CKO, some
> sort of a shared generic clock from inside of the CPU. I don't know if
> I could even set its frequency in DTS.

Please see:

	https://hverkuil.home.xs4all.nl/spec/driver-api/camera-sensor.html

Generally camera sensor drivers that set the clock in drivers themselves
are (very) old.

-- 
Regards,

Sakari Ailus