Re: [PATCH v6 1/4] dt-bindings: media: add Maxim MAX96717 GMSL2 Serializer

[Julien Massot]

Hi Sakari,

Thanks for the review

On 4/12/24 13:10, Sakari Ailus wrote:
> Hi Julien,
>
> On Mon, Mar 25, 2024 at 02:16:31PM +0100, Julien Massot wrote:
> > Add DT bindings for Maxim MAX96717 GMSL2 Serializer.
> >
> > Signed-off-by: Julien Massot <julien.massot@xxxxxxxxxxxxx>
> > ---
> > Change since v5:
> >   - Reverse the fallback MAX96717 can fallback to MAX96717F
> >   - Use const instead of enum for MAX96717F compatible
> >   
> > Change since v4:
> >   - Add compatible for MAX96717 and use it as a fallback for MAX96717F
> >   - Remove extra '|' for decriptions
> >   - Reference 'i2c-gate' instead of 'i2c-controller'
> >
> > Change since v3:
> >   - Renamed file to maxim,max96717.yaml dropped the 'f' suffix
> >   - Added lane-polarities and bus type properties to the CSI endpoint
> >
> > Change since v2:
> >   - remove reg description
> >   - add data lanes min/maxItems
> >   - Use generic node name
> > ---
> >   .../bindings/media/i2c/maxim,max96717.yaml    | 164 ++++++++++++++++++
> >   1 file changed, 164 insertions(+)
> >   create mode 100644 Documentation/devicetree/bindings/media/i2c/maxim,max96717.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max96717.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max96717.yaml
> > new file mode 100644
> > index 000000000000..ac8bf11a6fa5
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max96717.yaml
> > @@ -0,0 +1,164 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +# Copyright (C) 2024 Collabora Ltd.
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/media/i2c/maxim,max96717.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: MAX96717 CSI-2 to GMSL2 Serializer
> > +
> > +maintainers:
> > +  - Julien Massot <julien.massot@xxxxxxxxxxxxx>
> > +
> > +description:
> > +  The MAX96717 serializer converts MIPI CSI-2 D-PHY or C-PHY formatted input
> > +  into GMSL2 serial outputs. The device allows the GMSL2 link to
> > +  simultaneously transmit bidirectional control-channel data while forward
> > +  video transmissions are in progress. The MAX96717 can connect to one
> > +  remotely located deserializer using industry-standard coax or STP
> > +  interconnects. The device cans operate in pixel or tunnel mode. In pixel mode
> > +  the MAX96717 can select the MIPI datatype, while the tunnel mode forward all the MIPI
> > +  data received by the serializer.
> > +  The MAX96717 supports Reference Over Reverse (channel),
> > +  to generate a clock output for the sensor from the GMSL reverse channel.
> > +
> > +  The GMSL2 serial link operates at a fixed rate of 3Gbps or 6Gbps in the
> > +  forward direction and 187.5Mbps in the reverse direction.
> > +  MAX96717F only supports a fixed rate of 3Gbps in the forward direction.
> > +
> > +properties:
> > +  compatible:
> > +    oneOf:
> > +      - const: maxim,max96717f
> > +      - items:
> > +          - enum:
> > +              - maxim,max96717
> > +          - const: maxim,max96717f
> > +
> > +  '#gpio-cells':
> > +    const: 2
> > +    description:
> > +      First cell is the GPIO pin number, second cell is the flags. The GPIO pin
> > +      number must be in range of [0, 10].
> > +
> > +  gpio-controller: true
> > +
> > +  '#clock-cells':
> > +    const: 0
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  ports:
> > +    $ref: /schemas/graph.yaml#/properties/ports
> > +
> > +    properties:
> > +      port@0:
> > +        $ref: /schemas/graph.yaml#/$defs/port-base
> > +        unevaluatedProperties: false
> > +        description: CSI-2 Input port
> > +
> > +        properties:
> > +          endpoint:
> > +            $ref: /schemas/media/video-interfaces.yaml#
> > +            unevaluatedProperties: false
> > +
> > +            properties:
> > +              data-lanes:
> > +                minItems: 1
> > +                maxItems: 4
> > +
> > +              lane-polarities:
> > +                minItems: 1
> > +                maxItems: 5
> > +
> > +              bus-type:
> > +                enum:
> > +                  - 1 # MEDIA_BUS_TYPE_CSI2_CPHY
> > +                  - 4 # MEDIA_BUS_TYPE_CSI2_DPHY
>
> Now that you have C-PHY here, does the hardware support data line order
> mapping? Just wondering. The bindings can be added without that and support
> added later on---that's what the video-interfaces.yaml is currently
> missing.
>
> lane-polarities is only valid for D-PHY. What about the data-lanes, the
> maximum is probably different for C-PHY?
My mistake here; MAX96717 doesn't support C-PHY; I think I was confused 
by some of the schemas implying a deserializer with C-PHY support.
I will drop the bus-type property in v7.

Regards,
--
Julien