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

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Message-ID: <f5a178b9-2eeb-4737-a051-b43cde9fae20@collabora.com>
Date: Tue, 23 Apr 2024 15:36:39 +0200
From: Julien Massot <julien.massot@...labora.com>
To: Sakari Ailus <sakari.ailus@....fi>
Cc: linux-media@...r.kernel.org, devicetree@...r.kernel.org,
 kernel@...labora.com, linux-kernel@...r.kernel.org, mchehab@...nel.org,
 robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org
Subject: Re: [PATCH v6 1/4] dt-bindings: media: add Maxim MAX96717 GMSL2
 Serializer

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@...labora.com>
>> ---
>> 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@...labora.com>
>> +
>> +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