linux-kernel - Re: [PATCH 1/3] dt-binding: pinctrl: Document Loongson 2K0300 pin controller

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Message-ID: <20250818175827.GA1507697-robh@kernel.org>
Date: Mon, 18 Aug 2025 12:58:27 -0500
From: Rob Herring <robh@...nel.org>
To: Yao Zi <ziyao@...root.org>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Huacai Chen <chenhuacai@...nel.org>,
	WANG Xuerui <kernel@...0n.name>, linux-gpio@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	loongarch@...ts.linux.dev, Mingcong Bai <jeffbai@...c.io>,
	Kexy Biscuit <kexybiscuit@...c.io>
Subject: Re: [PATCH 1/3] dt-binding: pinctrl: Document Loongson 2K0300 pin
 controller

On Mon, Aug 11, 2025 at 04:37:48PM +0000, Yao Zi wrote:
> The pincontroller integarted in Loongson 2K0300 is able to configure
> function multiplexing for all the pins. It could also configure drive
> strength on basis of functions, which means all pins set to the same
> function share drive-strength setting. Drive-strength configuration
> isn't available for all functions, either.
> 
> This binding utilizes two levels of subnodes, where the outer represents
> function and the inner represents groups. Drive-strength is allowed in
> the outer since it's shared among all groups configured to the function.
> 
> Signed-off-by: Yao Zi <ziyao@...root.org>
> ---
>  .../pinctrl/loongson,ls2k0300-pinctrl.yaml    | 92 +++++++++++++++++++
>  MAINTAINERS                                   |  6 ++
>  2 files changed, 98 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/pinctrl/loongson,ls2k0300-pinctrl.yaml
> 
> diff --git a/Documentation/devicetree/bindings/pinctrl/loongson,ls2k0300-pinctrl.yaml b/Documentation/devicetree/bindings/pinctrl/loongson,ls2k0300-pinctrl.yaml
> new file mode 100644
> index 000000000000..cbd74cb45342
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/pinctrl/loongson,ls2k0300-pinctrl.yaml
> @@ -0,0 +1,92 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/pinctrl/loongson,ls2k0300-pinctrl.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Loongson-2K0300 SoC Pinctrl Controller
> +
> +maintainers:
> +  - Yao Zi <ziyao@...root.org>
> +
> +allOf:
> +  - $ref: pinctrl.yaml#
> +
> +properties:
> +  compatible:
> +    const: loongson,ls2k0300-pinctrl
> +
> +  reg:
> +    items:
> +      - description: Pin function-multiplexing configuration registers
> +      - description: Pin drive-strength configuration registers
> +
> +  reg-names:
> +    items:
> +      - const: mux
> +      - const: drive
> +
> +patternProperties:
> +  '^func-':
> +    type: object
> +
> +    $ref: pincfg-node.yaml#
> +
> +    properties:
> +      drive-strength:
> +        description:
> +          Maximum sink or source current as defined in pincfg-node.yaml. Note
> +          that drive strength could only be configured on function basis, i.e.,
> +          all pins multiplexed to the same function share the same
> +          configuration.
> +
> +          This could only be configured for several functions, including jtag,
> +          dvo, uart, gmac, sdio, spi, i2s, timer, usb and emmc.
> +        enum: [2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]

How do you know what pin this drive strength corresponds to without any 
other properties? Node names generally aren't important, so you 
shouldn't be using that. 

> +
> +    additionalProperties: false
> +
> +    patternProperties:
> +      '-pins$':
> +        type: object
> +        $ref: pinmux-node.yaml#

Generally the pin config and muxing are in 1 node if you can control 
both.

> +
> +        properties:
> +          pinmux:
> +            description:
> +              Integer array, represents GPIO pin number and multiplexing
> +              setting. Configuration for each pin takes one cell. The pin
> +              number locates at the high 24 bits, and the setting locates at
> +              the low 8 bits.
> +
> +        additionalProperties: false
> +
> +        required:
> +          - pinmux
> +
> +required:
> +  - compatible
> +  - reg
> +  - reg-names
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    pinctrl@...00420 {
> +        compatible = "loongson,ls2k0300-pinctrl";
> +        reg = <0x16000490 0x20>, <0x16000110 0x4>;
> +        reg-names = "mux", "drive";
> +
> +        func-uart {
> +            drive-strength = <2>;
> +
> +            uart0-pins {
> +                pinmux = <((40 << 8) | 0x3)>, <((41 << 8) | 0x3)>;
> +            };
> +
> +            uart1_pins: uart1-pins {
> +                pinmux = <((42 << 8) | 0x3)>, <((43 << 8) | 0x3)>;
> +            };
> +        };
> +    };
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 7960e65d7dfc..dd50571b4072 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14414,6 +14414,12 @@ S:	Maintained
>  F:	Documentation/devicetree/bindings/thermal/loongson,ls2k-thermal.yaml
>  F:	drivers/thermal/loongson2_thermal.c
>  
> +LOONGSON-2K0300 SOC PINCTRL DRIVER
> +M:	Yao Zi <ziyao@...root.org>
> +L:	linux-gpio@...r.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/pinctrl/loongson,ls2k0300-pinctrl.yaml
> +
>  LOONGSON EDAC DRIVER
>  M:	Zhao Qunqin <zhaoqunqin@...ngson.cn>
>  L:	linux-edac@...r.kernel.org
> -- 
> 2.50.1
>