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Date: Wed, 21 Feb 2024 11:10:49 +0100
From: Julien Massot <julien.massot@...labora.com>
To: Sakari Ailus <sakari.ailus@....fi>
Cc: linux-media@...r.kernel.org, kernel@...labora.com,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
mchehab@...nel.org, robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
conor+dt@...nel.org
Subject: Re: [PATCH v3 2/4] dt-bindings: media: add Maxim MAX96714F GMSL2
Deserializer
Hi Sakari,
Thanks for the review!
On 2/9/24 10:48, Sakari Ailus wrote:
> Hi Julien,
>
> On Thu, Jan 11, 2024 at 02:03:47PM +0100, Julien Massot wrote:
>> Add DT bindings for Maxim MAX96714F GMSL2 Deserializer.
>>
>> Signed-off-by: Julien Massot <julien.massot@...labora.com>
>>
>> ---
>> Change since v2:
>> - remove reg description
>> - rename enable gpio to powerdown
>> - use generic node name: i2c, serializer, deserializer
>> ---
>> .../bindings/media/i2c/maxim,max96714f.yaml | 171 ++++++++++++++++++
>> 1 file changed, 171 insertions(+)
>> create mode 100644 Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
>>
>> diff --git a/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml b/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
>> new file mode 100644
>> index 000000000000..2423d166c954
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/media/i2c/maxim,max96714f.yaml
>> @@ -0,0 +1,171 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +# Copyright (C) 2024 Collabora Ltd.
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/media/i2c/maxim,max96714f.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: Maxim MAX96714 GMSL2 to CSI-2 Deserializer
>> +
>> +maintainers:
>> + - Julien Massot <julien.massot@...labora.com>
>> +
>> +description: |
>> + The MAX96714F deserializer converts GMSL2 serial inputs into MIPI
>> + CSI-2 D-PHY or C-PHY formatted output. The device allows the GMSL2 link to
Description is wrong if the MAX96717F is supporting C-PHY MAX96714F doesn't.
I will remove the mention to C-PHY sorry for the confusion.
>> + simultaneously transmit bidirectional control-channel data while forward
>> + video transmissions are in progress. The MAX96714F 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 MAX96714F 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 in the
>> + forward direction and 187.5Mbps in the reverse direction.
>> +
>> +properties:
>> + compatible:
>> + const: maxim,max96714f
>> +
>> + reg:
>> + maxItems: 1
>> +
>> + powerdown-gpios:
>> + maxItems: 1
>> + description:
>> + Specifier for the GPIO connected to the PWDNB pin.
>> +
>> + ports:
>> + $ref: /schemas/graph.yaml#/properties/ports
>> +
>> + properties:
>> + port@0:
>> + $ref: /schemas/graph.yaml#/properties/port
>> + unevaluatedProperties: false
>> + description: GMSL Input
>> + properties:
>> + endpoint:
>> + $ref: /schemas/media/video-interfaces.yaml#
>> + unevaluatedProperties: false
>> + description:
>> + Endpoint for GMSL2-Link port.
>> +
>> + port@1:
>> + $ref: /schemas/graph.yaml#/$defs/port-base
>> + unevaluatedProperties: false
>> + description: CSI-2 Output port
>> +
>> + properties:
>> + endpoint:
>> + $ref: /schemas/media/video-interfaces.yaml#
>> + unevaluatedProperties: false
>> +
>> + properties:
>> + data-lanes:
>> + minItems: 1
>> + maxItems: 4
>> +
>> + link-frequencies:
>> + maxItems: 1
>> +
>> + bus-type:
>> + enum:
>> + - 4 # MEDIA_BUS_TYPE_CSI2_DPHY
>
> MEDIA_BUS_TYPE_CSI2_CPHY (1) is missing. Even if the driver doesn't support
> it, it would be best to list it here.
After verification the hardware only support D-PHY and not C-PHY, will
drop the required
property for 'bus-type'.
>
>> +
>> + required:
>> + - data-lanes
>> + - bus-type
>> +
>> + required:
>> + - port@1
>
> Why port@1 but not port@0?
The device can be used as a pattern generator, so this is fine not to
have a serializer connected to the port@0, but it makes no sense to
leave the deserializer CSI port not connected.
>
>> +
>> + i2c-gate:
>> + $ref: /schemas/i2c/i2c-controller.yaml
>> + unevaluatedProperties: false
>> + description: |
>> + The MAX96714 will pass through and forward the I2C requests from the
>> + incoming I2C bus over the GMSL2 link. Therefore it supports an i2c-gate
>> + subnode to configure a serializer.
>> +
>> + port0-poc-supply:
>> + description: Regulator providing Power over Coax for the GMSL port
>> +
>> +required:
>> + - compatible
>> + - reg
>> + - ports
>> +
>> +additionalProperties: false
>> +
>> +examples:
>> + - |
>> + #include <dt-bindings/gpio/gpio.h>
>> + #include <dt-bindings/media/video-interfaces.h>
>> +
>> + i2c {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + deserializer@28 {
>> + compatible = "maxim,max96714f";
>> + reg = <0x28>;
>> + powerdown-gpios = <&main_gpio0 37 GPIO_ACTIVE_LOW>;
>> +
>> + ports {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> + port@0 {
>> + reg = <0>;
>> + max96714_gmsl_in: endpoint {
>> + remote-endpoint = <&max96917f_gmsl_out>;
>> + };
>> + };
>> +
>> + port@1 {
>> + reg = <1>;
>> + max96714_csi_out: endpoint {
>> + bus-type = <MEDIA_BUS_TYPE_CSI2_DPHY>;
>> + clock-lanes = <0>;
>
> clock-lanes isn't listed in bindings. You can drop it from here.
Ok
>
>> + data-lanes = <1 2 3 4>;
>> + link-frequencies = /bits/ 64 <400000000>;
>> + remote-endpoint = <&csi_in>;
>> + };
>> + };
>> + };
>> +
>> + i2c-gate {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + serializer@40 {
>> + compatible = "maxim,max96717f";
>> + reg = <0x40>;
>> + gpio-controller;
>> + #gpio-cells = <2>;
>> + #clock-cells = <0>;
>> +
>> + ports {
>> + #address-cells = <1>;
>> + #size-cells = <0>;
>> +
>> + port@0 {
>> + reg = <0>;
>> + max96717f_csi_in: endpoint {
>> + data-lanes = <1 2>;
>> + lane-polarities = <1 0 1>;
>
> Shouldn't lane-polarities be mentioned in bindings, too?
You are right I will add lane-polarities to my next patchset.
>
>> + remote-endpoint = <&sensor_out>;
>> + };
>> + };
>> +
>> + port@1 {
>> + reg = <1>;
>> + max96917f_gmsl_out: endpoint {
>> + remote-endpoint = <&max96714_gmsl_in>;
>> + };
>> + };
>> + };
>> + };
>> + };
>> + };
>> + };
>> +...
>
Best regards,
--
Julien Massot
Senior Software Engineer
Collabora Ltd.
Platinum Building, St John's Innovation Park, Cambridge CB4 0DS, UK
Registered in England & Wales, no. 5513718
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