linux-kernel - Re: [PATCH 1/2] arm64: dts: rockchip: correct uart mux for Radxa ZERO 3

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Message-ID: <FBB5B30DE8FEABD7+59ee6f48-2ad1-45dd-8cf1-8b58a03513a9@radxa.com>
Date: Thu, 18 Sep 2025 13:53:15 +0900
From: FUKAUMI Naoki <naoki@...xa.com>
To: Ed Wildgoose <lists@...dgooses.com>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
 <conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
 devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] arm64: dts: rockchip: correct uart mux for Radxa ZERO
 3

Hi Ed,

Thank you very much for your work.

On 9/17/25 20:49, Ed Wildgoose wrote:
> The rk3566 has multiplexed pins and the uarts can be moved to a choice
> of 2 pin groups. The default rk356x-base.dtsi appears to default to mux0
> for all uarts, however, specific hardware might choose to implement
> alternatives
> 
> The Radxa zero 3 shows that is uses M1 for uarts:
> - uart4
> - uart5
> - uart9
> 
> These aren't normally enabled, but we should at least correct the
> default pinctrl definitions. Without these changes there will be
> conflicts with mmc0/mmc1, leading to the SD or eMMC going missing.

Sorry, but why do we need these definitions for disabled nodes?

Or why don't we do similar definitions for nodes other than uart?
For example, PWM12, I2S3, and SPI3 also use M1. Are they not related to 
SD/eMMC and therefore don't need to be defined?

If users want to use UARTs on pin headers, they will refer to the 
correct documentation[1] to determine which pins are UARTs and will of 
course write the correct pinctrl definition.

[1] 
https://docs.radxa.com/en/zero/zero3/hardware-design/hardware-interface#gpio-interface

Best regards,

--
FUKAUMI Naoki
Radxa Computer (Shenzhen) Co., Ltd.

> 
> Signed-off-by: Ed Wildgoose <lists@...dgooses.com>
> ---
>   .../boot/dts/rockchip/rk3566-radxa-zero-3.dtsi    | 15 +++++++++++++++
>   1 file changed, 15 insertions(+)
> 
> diff --git a/arch/arm64/boot/dts/rockchip/rk3566-radxa-zero-3.dtsi b/arch/arm64/boot/dts/rockchip/rk3566-radxa-zero-3.dtsi
> index 1ee5d96a4..41b3c4403 100644
> --- a/arch/arm64/boot/dts/rockchip/rk3566-radxa-zero-3.dtsi
> +++ b/arch/arm64/boot/dts/rockchip/rk3566-radxa-zero-3.dtsi
> @@ -492,6 +492,21 @@ &uart2 {
>   	status = "okay";
>   };
>   
> +&uart4{
> +    pinctrl-names = "default";
> +    pinctrl-0 = <&uart4m1_xfer>;
> +};
> +
> +&uart5 {
> +    pinctrl-names = "default";
> +    pinctrl-0 = <&uart5m1_xfer>;
> +};
> +
> +&uart9 {
> +    pinctrl-names = "default";
> +    pinctrl-0 = <&uart9m1_xfer>;
> +};
> +
>   &usb_host0_xhci {
>   	status = "okay";
>   };