Subject: Re: [PATCH v15 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings

From: Rob Herring <[email-masked]>
Date: Fri, 16 Oct 2020 12:21:29 -0500

On Wed, Oct 14, 2020 at 01:48:00PM +0200, Tomasz Figa wrote:
> On Wed, Oct 14, 2020 at 10:31 AM Sakari Ailus
> <[email-masked]> wrote:
> >
> > On Wed, Oct 14, 2020 at 10:10:18AM +0800, Dongchun Zhu wrote:
> > > Hello Sakari,
> > >
> > > Thanks for your timely review.
> > >
> > > On Tue, 2020-10-13 at 19:19 +0300, Sakari Ailus wrote:
> > > > Hi Dongchun,
> > > >
> > > > On Tue, Oct 13, 2020 at 09:05:02PM +0800, Dongchun Zhu wrote:
> > > > > Add YAML device tree binding for OV02A10 CMOS image sensor, and the
> > > > > relevant MAINTAINERS entries.
> > > > >
> > > > > Signed-off-by: Dongchun Zhu <[email-masked]>
> > > > > ---
> > > > >  .../bindings/media/i2c/ovti,ov02a10.yaml           | 162 +++++++++++++++++++++
> > > > >  MAINTAINERS                                        |   7 +
> > > > >  2 files changed, 169 insertions(+)
> > > > >  create mode 100644 Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml
> > > > >
> > >
> > > [snip]...
> > >
> > > > > +  ovti,mipi-clock-voltage:
> > > > > +    description:
> > > > > +      An array of 2-tuples items, and each item consists of link frequency and
> > > > > +      MIPI clock voltage unit like <freq-kHz volt-unit>. Clock voltage unit is
> > > > > +      dependent upon link speed, indicating MIPI transmission speed select that
> > > > > +      controls D-PHY timing setting by adjusting MIPI clock voltage to improve
> > > > > +      the clock driver capability.
> > > > > +    $ref: "/schemas/types.yaml#/definitions/uint32-array"
> > > > > +    minItems: 2
> > > > > +    default: [390000, 4]
> > > >
> > > > Why do you have the link frequency here as well?
> > > >
> > > > In principle this does belong to the endpoint as link frequencies are
> > > > specific to that, but I don't mind; there's just a single port anyway.
> > > >
> > >
> > > This is an optional property which we model as an array of <link speed,
> > > clock voltage> pairs. An example to have all link speeds up to 390MHz
> > > use the value 4 for current driver. If one wants to select different
> > > voltage for different link, they could do so as well.
> >
> > If you think you'd need that, then you need to put this to the endpoint.
> 
> The mipi-clock-voltage property is not a property of the endpoint. The
> link frequency there does not set the link frequency - it only
> specifies which link frequency the given voltage should be used for.

Seems to me it's in the right place.

Rob

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