linux-kernel - Re: [PATCH 1/2] dt-bindings: media: renesas,vin: Document renesas-vin-ycbcr-8b-g property

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Message-ID: <CA+V-a8s7UkhCGcP8eiiH_jd8hhnpLJA6QqfL7jXo_sAgRMfy8g@mail.gmail.com>
Date:   Fri, 24 Jul 2020 22:11:31 +0100
From:   "Lad, Prabhakar" <prabhakar.csengg@...il.com>
To:     Niklas <niklas.soderlund@...natech.se>
Cc:     Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        linux-media <linux-media@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>,
        Biju Das <biju.das.jz@...renesas.com>,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: Re: [PATCH 1/2] dt-bindings: media: renesas,vin: Document
 renesas-vin-ycbcr-8b-g property

Hi Niklas,

Thank you for the review.

On Fri, Jul 24, 2020 at 8:37 PM Niklas <niklas.soderlund@...natech.se> wrote:
>
> Hi Lad,
>
> Thanks for your patch.
>
> On 2020-07-24 15:58:51 +0100, Lad Prabhakar wrote:
> > Add a DT property "renesas-vin-ycbcr-8b-g" to select YCbCr422 8-bit data
> > input pins.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>
> > Reviewed-by: Biju Das <biju.das.jz@...renesas.com>
> > ---
> >  Documentation/devicetree/bindings/media/renesas,vin.yaml | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/media/renesas,vin.yaml b/Documentation/devicetree/bindings/media/renesas,vin.yaml
> > index 53c0a72..7dfb781 100644
> > --- a/Documentation/devicetree/bindings/media/renesas,vin.yaml
> > +++ b/Documentation/devicetree/bindings/media/renesas,vin.yaml
> > @@ -106,6 +106,12 @@ properties:
> >
> >            remote-endpoint: true
> >
> > +          renesas-vin-ycbcr-8b-g:
>
> I think the preferred format for vendor specific properties are
> "<vendor>,<property>".
>
Indeed and I had it as renesas,vin-ycbcr-8b-g but dt_bindings_check
complained about it.

> This nit apart I'm not sure a property is the right way here. Could it
> not be possible on some designs to have two different sensors one wired
> to DATA[7:0] and the other to DATA[15:8] and by controlling the
> VNDRM2_YDS register at runtime switch between the two? If so adding a DT
> property to hard-code one of the two options would prevent this. I fear
> we need to think of a runtime way to deal with this.
>
Aha Gen2 and Gen3 hardware manuals have a bit different description
about the YDS field. (I was working R8a7742 SoC so I referred Gen2
manual)

> The best way to do that I think is to extend the port@0 node to allow
> for two endpoints, one for each of the two possible parallel sensors.
> This would then have to be expressed in the media graph and selection if
> YDS should be set or not depend on which media links are enabled.
>
In that case how do we handle endpoint matching each would have two
subdevs to be matched. And in case non media-ctl cases we cannot
switch between subdevs.

Cheers,
--Prabhakar

> > +            type: boolean
> > +            description:
> > +              If present this property specifies to selects VIN_G[7:0] as data pins for YCbCr422 8-bit data.
> > +            default: false
> > +
> >          required:
> >            - remote-endpoint
> >
> > @@ -168,6 +174,13 @@ properties:
> >
> >                remote-endpoint: true
> >
> > +              renesas-vin-ycbcr-8b-g:
> > +                type: boolean
> > +                description:
> > +                  If present this property specifies to selects VIN_G[7:0] as data pins for
> > +                  YCbCr422 8-bit data.
> > +                default: false
> > +
> >              required:
> >                - remote-endpoint
> >
> > --
> > 2.7.4
> >
>
> --
> Regards,
> Niklas Söderlund