linux-kernel - Re: [PATCH v6 1/5] dt-bindings: remoteproc: imx

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Message-ID:
 <PAXPR04MB9185E86CB81C111DAB5B329D89ABA@PAXPR04MB9185.eurprd04.prod.outlook.com>
Date: Wed, 17 Dec 2025 19:45:10 +0000
From: Shenwei Wang <shenwei.wang@....com>
To: Rob Herring <robh@...nel.org>
CC: Linus Walleij <linusw@...nel.org>, Bartosz Golaszewski <brgl@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>,
	Bjorn Andersson <andersson@...nel.org>, Mathieu Poirier
	<mathieu.poirier@...aro.org>, Shawn Guo <shawnguo@...nel.org>, Sascha Hauer
	<s.hauer@...gutronix.de>, Jonathan Corbet <corbet@....net>, Pengutronix
 Kernel Team <kernel@...gutronix.de>, Fabio Estevam <festevam@...il.com>, Peng
 Fan <peng.fan@....com>, "linux-gpio@...r.kernel.org"
	<linux-gpio@...r.kernel.org>, "devicetree@...r.kernel.org"
	<devicetree@...r.kernel.org>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "linux-remoteproc@...r.kernel.org"
	<linux-remoteproc@...r.kernel.org>, "imx@...ts.linux.dev"
	<imx@...ts.linux.dev>, "linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "linux-doc@...r.kernel.org"
	<linux-doc@...r.kernel.org>, dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v6 1/5] dt-bindings: remoteproc: imx_rproc: Add "rpmsg"
 subnode support



> -----Original Message-----
> Subject: [EXT] Re: [PATCH v6 1/5] dt-bindings: remoteproc: imx_rproc: Add
> "rpmsg" subnode support
> 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?

It runs on the RPMSG  Control channel.

> 
> > 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@....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
> > +---
> > +
> > +title: Generic GPIO driver over RPMSG
> 
> The driver doesn't go over RPMSG. It's a GPIO provider or protocol.
> 

Yes, it might be clearer to phrase it as 'Generic RPMSG GPIO Controller,' since this is 
a GPIO controller driver that operates over the RPMsg bus.

> > +
> > +maintainers:
> > +  - Shenwei Wang <shenwei.wang@....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?

Will add a ref to the gpio-rpmsg.rst doc.

> 
> > +
> > +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.
> 

I see. Will add a description for this item.

> > +
> > +  "#gpio-cells":
> > +    const: 2
> > +
> > +  gpio-controller: true
> >        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"?

It represents the RPMSG bus between Linux and the remote processor, and will eventually 
host additional channels such as rpmsg-i2c-channel and rpmsg-pwm-channel.

Thanks,
Shenwei

> 
> > +        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
> >