Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg GPIO driver

-----Original Message-----
From: Mathieu Poirier <mathieu.poirier@linaro.org>
Sent: Tuesday, February 24, 2026 4:47 PM
To: Shenwei Wang <shenwei.wang@nxp.com>
Cc: Andrew Lunn <andrew@lunn.ch>; Arnaud POULIQUEN
[off-list ref]; Linus Walleij [off-list ref]; Bartosz
Golaszewski [off-list ref]; Jonathan Corbet [off-list ref]; Rob Herring
[off-list ref]; Krzysztof Kozlowski [off-list ref]; Conor Dooley
[off-list ref]; Bjorn Andersson [off-list ref]; Frank Li
[off-list ref]; Sascha Hauer [off-list ref]; Shuah Khan
[off-list ref]; linux-gpio@vger.kernel.org; linux-
doc@vger.kernel.org; linux-kernel@vger.kernel.org; Pengutronix Kernel Team
[off-list ref]; Fabio Estevam [off-list ref]; Peng Fan
[off-list ref]; devicetree@vger.kernel.org; linux-
remoteproc@vger.kernel.org; imx@lists.linux.dev; linux-arm-
kernel@lists.infradead.org; dl-linux-imx [off-list ref]; Bartosz
Golaszewski [off-list ref]
Subject: [EXT] Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg GPIO driver

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-----Original Message-----
From: Andrew Lunn <andrew@lunn.ch>
Sent: Tuesday, February 24, 2026 4:23 PM
To: Shenwei Wang <shenwei.wang@nxp.com>
Cc: Arnaud POULIQUEN <arnaud.pouliquen@foss.st.com>; Linus Walleij
[off-list ref]; Bartosz Golaszewski [off-list ref]; Jonathan
Corbet [off-list ref]; Rob Herring [off-list ref]; Krzysztof
Kozlowski [off-list ref]; Conor Dooley [off-list ref];
Bjorn Andersson [off-list ref]; Mathieu Poirier
[off-list ref]; Frank Li [off-list ref]; Sascha
Hauer [off-list ref]; Shuah Khan
[off-list ref]; linux-gpio@vger.kernel.org; linux-
doc@vger.kernel.org; linux-kernel@vger.kernel.org; Pengutronix
Kernel Team [off-list ref]; Fabio Estevam
[off-list ref]; Peng Fan [off-list ref];
devicetree@vger.kernel.org; linux- remoteproc@vger.kernel.org;
imx@lists.linux.dev; linux-arm- kernel@lists.infradead.org;
dl-linux-imx [off-list ref]; Bartosz Golaszewski
[off-list ref]
Subject: Re: [EXT] Re: [PATCH v8 3/4] gpio: rpmsg: add generic rpmsg
GPIO driver

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button

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+ remote_cm33{
+     rpmsg {
+        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;
+          };
+          gpio@1 {
+            compatible = "rpmsg-gpio";
+            reg = <1>;
+            gpio-controller;
+            #gpio-cells = <2>;
+            #interrupt-cells = <2>;
+            interrupt-controller;
+          };

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Then how would you distinguish gpio@0 from gpio@1 on the CM33
RPMSG bus

in the example above?

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They are running on the same transport.

Doesn't reg indicate the channel number? gpio@0 is on rpmsg channel
0. gpio@1 is on channel 1? The reg value gets filled into struct
rpmsg_channel_info when the endpoints are created?

There is only a single RPMSG channel for the CM33 remoteproc in this
example-its name is "rpmsg-io-channel". As I mentioned above, both gpio@0

and gpio@1 run over this same transport.

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The transport here is the RPMSG channel, so multiple GPIO controllers share

that channel.

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That is one of my main problem with this proposal - multiplexing several GPIO
controllers over the same RPMSG channel adds complexity.

Multiplexing multiple GPIO controllers over a single RPMSG channel does not inherently 
add complexity. Even if we implement a “one GPIO controller per RPMSG channel” model, 
the core logic in the driver remains essentially the same.

In fact, the current implementation already supports your preferred “one RPMSG channel 
per GPIO controller” approach through simple DTS configuration. For example:

+ remote_cm33{
+     rpmsg {
+        channel0 {    
+          gpio@0 {
+            compatible = "rpmsg-gpio";
+            reg = <0>;
+            gpio-controller;
+            #gpio-cells = <2>;
+            #interrupt-cells = <2>;
+            interrupt-controller;
+          };
+       };
+
+        channel1 {
+          gpio@1 {
+            compatible = "rpmsg-gpio";
+            reg = <1>;
+            gpio-controller;
+            #gpio-cells = <2>;
+            #interrupt-cells = <2>;
+            interrupt-controller;
+          };
+        };
+      };
+};
+

RPMSG can already handle multiplexing via channels, use one RPMSG channel
per GPIO controller.

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Thanks,
Shenwei

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   Andrew