Re: [PATCH v7 2/6] dt-bindings: mfd: Binding for RTL8231

[Rob Herring]

On Mon, Nov 17, 2025 at 3:52 PM Sander Vanheule <sander@xxxxxxxxxxxxx> wrote:
>
> Add a binding description for the Realtek RTL8231, a GPIO and LED
> expander chip commonly used in ethernet switches based on a Realtek
> switch SoC. These chips can be addressed via an MDIO or SMI bus, or used
> as a plain 36-bit shift register.
>
> This binding only describes the feature set provided by the MDIO/SMI
> configuration, and covers the GPIO, PWM, and pin control properties. The
> LED properties are defined in a separate binding.
>
> Signed-off-by: Sander Vanheule <sander@xxxxxxxxxxxxx>
> ---
> Changes since v6:
> - Relax description formatting
> - Use absolute paths for schema references
> - Add pinctrl properties to led-controller node in example
> ---
>  .../bindings/mfd/realtek,rtl8231.yaml         | 193 ++++++++++++++++++
>  1 file changed, 193 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/mfd/realtek,rtl8231.yaml
>
> diff --git a/Documentation/devicetree/bindings/mfd/realtek,rtl8231.yaml b/Documentation/devicetree/bindings/mfd/realtek,rtl8231.yaml
> new file mode 100644
> index 000000000000..5669dd58654e
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/mfd/realtek,rtl8231.yaml
> @@ -0,0 +1,193 @@
> +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/mfd/realtek,rtl8231.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Realtek RTL8231 GPIO and LED expander.
> +
> +maintainers:
> +  - Sander Vanheule <sander@xxxxxxxxxxxxx>
> +
> +description: |
> +  The RTL8231 is a GPIO and LED expander chip, providing up to 37 GPIOs, up to
> +  88 LEDs, and up to one PWM output. This device is frequently used alongside
> +  Realtek switch SoCs, to provide additional I/O capabilities.
> +
> +  To manage the RTL8231's features, its strapping pins can be used to configure
> +  it in one of three modes: shift register, MDIO device, or SMI device. The
> +  shift register mode does not need special support. In MDIO or SMI mode, most
> +  pins can be configured as a GPIO output or LED matrix scan line/column. One
> +  pin can be used as PWM output.
> +
> +  The GPIO, PWM, and pin control are part of the main node. LED support is
> +  configured as a sub-node.
> +
> +properties:
> +  compatible:
> +    const: realtek,rtl8231
> +
> +  reg:
> +    description: MDIO or SMI device address.
> +    maxItems: 1
> +
> +  # GPIO support
> +  gpio-controller: true
> +
> +  "#gpio-cells":
> +    const: 2
> +    description:
> +      The first cell is the pin number and the second cell is used to specify
> +      the GPIO active state.
> +
> +  gpio-ranges:
> +    description:
> +      Must reference itself, and provide a zero-based mapping for 37 pins.
> +    maxItems: 1
> +
> +  # Pin muxing and configuration
> +  drive-strength:
> +    description:
> +      Common drive strength used for all GPIO output pins, must be 4mA or 8mA.
> +      On reset, this value will default to 8mA.
> +    enum: [4, 8]
> +
> +  # LED scanning matrix
> +  led-controller:
> +    $ref: /schemas/leds/realtek,rtl8231-leds.yaml#
> +
> +  # PWM output
> +  "#pwm-cells":
> +    description:
> +      Twos cells with PWM index (must be 0) and PWM frequency in Hz. To use
> +      the PWM output, gpio35 must be muxed to its "pwm" function. Valid
> +      frequency values for consumers are 1200, 1600, 2000, 2400, 2800, 3200,
> +      4000, and 4800.
> +    const: 2
> +
> +patternProperties:
> +  "-pins$":
> +    type: object
> +    $ref: /schemas/pinctrl/pinmux-node.yaml#

         additionalProperties: false

> +
> +    properties:
> +      pins:
> +        items:
> +          enum: [gpio0, gpio1, gpio2, gpio3, gpio4, gpio5, gpio6, gpio7,
> +                 gpio8, gpio9, gpio10, gpio11, gpio12, gpio13, gpio14, gpio15,
> +                 gpio16, gpio17, gpio18, gpio19, gpio20, gpio21, gpio22, gpio23,
> +                 gpio24, gpio25, gpio26, gpio27, gpio28, gpio29, gpio30, gpio31,
> +                 gpio32, gpio33, gpio34, gpio35, gpio36]
> +        minItems: 1
> +        maxItems: 37
> +
> +      function:
> +        description:
> +          Select which function to use. "gpio" is supported for all pins, "led" is supported
> +          for pins 0-34, "pwm" is supported for pin 35.
> +        enum: [gpio, led, pwm]
> +
> +    required:
> +      - pins
> +      - function
> +
> +required:
> +  - compatible
> +  - reg
> +  - gpio-controller
> +  - "#gpio-cells"
> +  - gpio-ranges
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    // Minimal example
> +    mdio {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        expander0: expander@0 {
> +            compatible = "realtek,rtl8231";
> +            reg = <0>;
> +
> +            gpio-controller;
> +            #gpio-cells = <2>;
> +            gpio-ranges = <&expander0 0 0 37>;
> +        };
> +    };
> +  - |
> +    // All bells and whistles included
> +    #include <dt-bindings/leds/common.h>
> +    mdio {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        expander1: expander@1 {
> +            compatible = "realtek,rtl8231";
> +            reg = <1>;
> +
> +            gpio-controller;
> +            #gpio-cells = <2>;
> +            gpio-ranges = <&expander1 0 0 37>;
> +
> +            #pwm-cells = <2>;
> +
> +            drive-strength = <4>;
> +
> +            button-pins {
> +                pins = "gpio36";
> +                function = "gpio";
> +                input-debounce = <100000>;
> +            };
> +
> +            pwm-pins {
> +                pins = "gpio35";
> +                function = "pwm";
> +            };
> +
> +            led_matrix: led-pins {
> +                pins = "gpio0", "gpio1", "gpio3", "gpio4";
> +                function = "led";
> +            };
> +
> +            led-controller {
> +                compatible = "realtek,rtl8231-leds";
> +                #address-cells = <2>;
> +                #size-cells = <0>;
> +
> +                pinctrl-names = "default";
> +                pinctrl-0 = <&led_matrix>;
> +
> +                realtek,led-scan-mode = "single-color";
> +
> +                led@0,0 {
> +                    reg = <0 0>;
> +                    color = <LED_COLOR_ID_GREEN>;
> +                    function = LED_FUNCTION_LAN;
> +                    function-enumerator = <0>;
> +                };
> +
> +                led@0,1 {
> +                    reg = <0 1>;
> +                    color = <LED_COLOR_ID_AMBER>;
> +                    function = LED_FUNCTION_LAN;
> +                    function-enumerator = <0>;
> +                };
> +
> +                led@1,0 {
> +                    reg = <1 0>;
> +                    color = <LED_COLOR_ID_GREEN>;
> +                    function = LED_FUNCTION_LAN;
> +                    function-enumerator = <1>;
> +                };
> +
> +                led@1,1 {
> +                    reg = <1 1>;
> +                    color = <LED_COLOR_ID_AMBER>;
> +                    function = LED_FUNCTION_LAN;
> +                    function-enumerator = <1>;
> +                };
> +            };
> +        };
> +    };
> --
> 2.51.1
>
>