Re: [PATCH v6 1/5] dt-bindings: remoteproc: imx_rproc: Add "rpmsg" subnode support

[Rob Herring <robh@kernel.org>]

On Fri, Dec 12, 2025 at 01:43:37PM -0600, Shenwei Wang wrote:
> Remote processors may announce multiple devices (e.g., I2C, GPIO) over
> an RPMSG channel. 

Which channel does that happen on?

> These devices may require corresponding device tree
> nodes, especially when acting as providers, to supply phandles for their
> consumers.
> 
> Define an RPMSG node to work as a container for a group of RPMSG channels
> under the imx_rproc node.
> 
> Each subnode within "rpmsg" represents an individual RPMSG channel. The
> name of each subnode corresponds to the channel name as defined by the
> remote processor.
> 
> All remote devices associated with a given channel are defined as child
> nodes under the corresponding channel node.
> 
> Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
> ---
>  .../devicetree/bindings/gpio/gpio-rpmsg.yaml  | 49 +++++++++++++++++
>  .../bindings/remoteproc/fsl,imx-rproc.yaml    | 54 +++++++++++++++++++
>  2 files changed, 103 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/gpio/gpio-rpmsg.yaml
> 
> diff --git a/Documentation/devicetree/bindings/gpio/gpio-rpmsg.yaml b/Documentation/devicetree/bindings/gpio/gpio-rpmsg.yaml
> new file mode 100644
> index 000000000000..b3e1a5dbf731
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/gpio/gpio-rpmsg.yaml
> @@ -0,0 +1,49 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/gpio/gpio-rpmsg.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Generic GPIO driver over RPMSG

The driver doesn't go over RPMSG. It's a GPIO provider or protocol.

> +
> +maintainers:
> +  - Shenwei Wang <shenwei.wang@nxp.com>
> +
> +description:
> +  On an AMP platform, some GPIO controllers are exposed by the remote processor
> +  through the RPMSG bus. The RPMSG GPIO transport protocol defines the packet
> +  structure and communication flow between Linux and the remote firmware. Those
> +  controllers are managed via this transport protocol.

Got a reference to where any of this is defined?

> +
> +properties:
> +  compatible:
> +    oneOf:
> +      - items:
> +          - enum:
> +              - fsl,rpmsg-gpio
> +          - const: rpmsg-gpio
> +      - const: rpmsg-gpio
> +
> +  reg:
> +    maxItems: 1

I still don't understand how 'reg' is determined. You may have explained 
it previously, but *this* patch needs to make me understand.

> +
> +  "#gpio-cells":
> +    const: 2
> +
> +  gpio-controller: true
> +
> +  interrupt-controller: true
> +
> +  "#interrupt-cells":
> +    const: 2
> +
> +required:
> +  - compatible
> +  - reg
> +  - "#gpio-cells"
> +  - "#interrupt-cells"
> +
> +allOf:
> +  - $ref: /schemas/gpio/gpio.yaml#
> +
> +unevaluatedProperties: false
> diff --git a/Documentation/devicetree/bindings/remoteproc/fsl,imx-rproc.yaml b/Documentation/devicetree/bindings/remoteproc/fsl,imx-rproc.yaml
> index 57d75acb0b5e..fd8e5a61a459 100644
> --- a/Documentation/devicetree/bindings/remoteproc/fsl,imx-rproc.yaml
> +++ b/Documentation/devicetree/bindings/remoteproc/fsl,imx-rproc.yaml
> @@ -84,6 +84,33 @@ properties:
>        This property is to specify the resource id of the remote processor in SoC
>        which supports SCFW
>  
> +  rpmsg:
> +    type: object
> +    additionalProperties: false
> +    description:
> +      Present a group of RPMSG channel devices.
> +
> +    properties:
> +      rpmsg-io-channel:
> +        type: object
> +        additionalProperties: false
> +        properties:
> +          '#address-cells':
> +            const: 1
> +
> +          '#size-cells':
> +            const: 0
> +
> +        patternProperties:
> +          "gpio@[0-9a-f]+$":
> +            type: object
> +            $ref: /schemas/gpio/gpio-rpmsg.yaml#
> +            unevaluatedProperties: false
> +
> +        required:
> +          - '#address-cells'
> +          - '#size-cells'
> +
>  required:
>    - compatible
>  
> @@ -146,5 +173,32 @@ examples:
>                  &mu 3 1>;
>        memory-region = <&vdev0buffer>, <&vdev0vring0>, <&vdev0vring1>, <&rsc_table>;
>        syscon = <&src>;
> +
> +      rpmsg {

What's the purpose of this node? Is it going to contain things other 
than "rpmsg io channels"?

> +        rpmsg-io-channel {
> +          #address-cells = <1>;
> +          #size-cells = <0>;
> +
> +          gpio@0 {
> +            compatible = "rpmsg-gpio";
> +            reg = <0>;
> +            gpio-controller;
> +            #gpio-cells = <2>;
> +            #interrupt-cells = <2>;
> +            interrupt-controller;
> +            interrupt-parent = <&rpmsg_gpioa>;
> +          };
> +
> +          gpio@1 {
> +            compatible = "rpmsg-gpio";
> +            reg = <1>;
> +            gpio-controller;
> +            #gpio-cells = <2>;
> +            #interrupt-cells = <2>;
> +            interrupt-controller;
> +            interrupt-parent = <&rpmsg_gpiob>;
> +          };
> +        };
> +      };
>      };
>  ...
> -- 
> 2.43.0
>