Re: [PATCH v5 2/4] dt-bindings: media: add Maxim MAX96714 GMSL2 Deserializer

[Julien Massot]

Hi Conor,

Thanks for your review.
On 3/17/24 16:18, Conor Dooley wrote:
> On Wed, Mar 13, 2024 at 10:49:20AM +0100, Julien Massot wrote:
> > Add DT bindings for Maxim MAX96714 GMSL2 Deserializer.
> >
> > Signed-off-by: Julien Massot <julien.massot@xxxxxxxxxxxxx>
> > ---
> > Change since v4:
> >   - Add compatible for MAX96714 and use it as a fallback for MAX96714F
> >   - Remove extra '|' for decriptions
> >   - Reference 'i2c-gate' instead of 'i2c-controller'
> >
> > Change since v3:
> >   - Renamed file to maxim,max96714.yaml dropped the 'f' suffix
> >   - Removed mention to C-PHY since it's not supported by MAX96714 deserializers
> >   - Removed bus-type requirement on CSI endpoint since the device only support D-PHY
> >   - Removed the clock-lanes property in the dt example
> >
> > Change since v2:
> >   - remove reg description
> >   - rename enable gpio to powerdown
> >   - use generic node name: i2c, serializer, deserializer
> > ---
> >   .../bindings/media/i2c/maxim,max96714.yaml    | 176 ++++++++++++++++++
> >   1 file changed, 176 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml
> > new file mode 100644
> > index 000000000000..59b116092834
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max96714.yaml
> > @@ -0,0 +1,176 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +# Copyright (C) 2024 Collabora Ltd.
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/media/i2c/maxim,max96714.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Maxim MAX96714 GMSL2 to CSI-2 Deserializer
> > +
> > +maintainers:
> > +  - Julien Massot <julien.massot@xxxxxxxxxxxxx>
> > +
> > +description:
> > +  The MAX96714 deserializer converts GMSL2 serial inputs into MIPI
> > +  CSI-2 D-PHY formatted output. The device allows the GMSL2 link to
> > +  simultaneously transmit bidirectional control-channel data while forward
> > +  video transmissions are in progress. The MAX96714 can connect to one
> > +  remotely located serializer using industry-standard coax or STP
> > +  interconnects. The device cans operate in pixel or tunnel mode. In pixel mode
> > +  the MAX96714 can select individual video stream, while the tunnel mode forward all
> > +  the MIPI data received by the serializer.
> > +
> > +  The GMSL2 serial link operates at a fixed rate of 3Gbps or 6Gbps in the
> > +  forward direction and 187.5Mbps in the reverse direction.
> > +  MAX96714F only supports a fixed rate of 3Gbps in the forward direction.
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - enum:
> > +          - maxim,max96714
>
> There's only once device here, make it const rather than enum.

Okay fixed in v6

> > +      - items:
> > +          - enum:
> > +              - maxim,max96714f
> > +          - const: maxim,max96714 # fallback for 'f' variant
>
> Drop the comment btw, it doesn't make sense given you have an enum that
> will allow for more devices and it being a fallback is obvious. That
> said, given what you told me on the last version
> | Yes there are a few differences visible to the software, for example the
> | GMSL
> | link rate since MAX96714 support 6 and 3 Gbps, while MAX96714F only
> | supports 3Gbps.
> | the registers map is the same, but a few values are not possible with
> | the 'f' version.
> I don't think your ordering here is correct. The 96714 should fall back
> to the 96714f, not the opposite that you have here, as the f is the
> version which supports fewer features.
>
> I think this should be:
>
> oneOf:
>    - const: maxim,max96714f
>    - items:
>        - enum:
>            - maxim,max96714
>        - const: maxim,max96714f

I just sent a v6 version with your suggestion. Indeed it makes more sense
to use max96714/7f as a fallback for the non f variant.

Best regards,
Julien