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

From: Tomasz Figa <tfiga@chromium.org>
To: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: "Dongchun Zhu" <dongchun.zhu@mediatek.com>,
	"Mauro Carvalho Chehab" <mchehab@kernel.org>,
	"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Mark Rutland" <mark.rutland@arm.com>,
	"Nicolas Boichat" <drinkcat@chromium.org>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	"Cao Bing Bu" <bingbu.cao@intel.com>,
	srv_heupstream <srv_heupstream@mediatek.com>,
	"moderated list:ARM/Mediatek SoC support"
	<linux-mediatek@lists.infradead.org>,
	"list@263.net:IOMMU DRIVERS <iommu@lists.linux-foundation.org>,
	Joerg Roedel <joro@8bytes.org>,"
	<linux-arm-kernel@lists.infradead.org>,
	"Sj Huang" <sj.huang@mediatek.com>,
	"Linux Media Mailing List" <linux-media@vger.kernel.org>,
	linux-devicetree <devicetree@vger.kernel.org>,
	"Louis Kuo" <louis.kuo@mediatek.com>,
	"Shengnan Wang (王圣男)" <shengnan.wang@mediatek.com>
Subject: Re: [PATCH v15 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings
Date: Wed, 14 Oct 2020 13:48:00 +0200	[thread overview]
Message-ID: <CAAFQd5BVzN=49s4S98E9mGNuxzOt4633dAw9mbyu3Sr-rA61qw@mail.gmail.com> (raw)
In-Reply-To: <20201014083139.GG13341@paasikivi.fi.intel.com>

On Wed, Oct 14, 2020 at 10:31 AM Sakari Ailus
<sakari.ailus@linux.intel.com> 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 <dongchun.zhu@mediatek.com>
> > > > ---
> > > >  .../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.

Best regards,
Tomasz