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Message-ID: <20251021142407.307753-5-sander@svanheule.net>
Date: Tue, 21 Oct 2025 16:23:59 +0200
From: Sander Vanheule <sander@...nheule.net>
To: Michael Walle <mwalle@...nel.org>,
Linus Walleij <linus.walleij@...aro.org>,
Bartosz Golaszewski <brgl@...ev.pl>,
linux-gpio@...r.kernel.org,
Lee Jones <lee@...nel.org>,
Pavel Machek <pavel@...nel.org>,
Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>,
linux-leds@...r.kernel.org,
devicetree@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
Sander Vanheule <sander@...nheule.net>
Subject: [PATCH v6 4/8] dt-bindings: mfd: Binding for RTL8231
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@...nheule.net>
---
.../bindings/mfd/realtek,rtl8231.yaml | 189 ++++++++++++++++++
1 file changed, 189 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..25135917d3f2
--- /dev/null
+++ b/Documentation/devicetree/bindings/mfd/realtek,rtl8231.yaml
@@ -0,0 +1,189 @@
+# 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@...nheule.net>
+
+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:
+ $ref: ../leds/realtek,rtl8231-leds.yaml#
+
+ # PWM output
+ "#pwm-cells":
+ description: |
+ Twos cells with PWM index (must be 0) and PWM frequency in Hz. To use
+ the PWM output, gpio35 must be muxed to its 'pwm' function. Valid
+ frequency values for consumers are 1200, 1600, 2000, 2400, 2800, 3200,
+ 4000, and 4800.
+ const: 2
+
+patternProperties:
+ "-pins$":
+ type: object
+ $ref: ../pinctrl/pinmux-node.yaml#
+
+ 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-pins {
+ pins = "gpio0", "gpio1", "gpio3", "gpio4";
+ function = "led";
+ };
+
+ led-controller {
+ compatible = "realtek,rtl8231-leds";
+ #address-cells = <2>;
+ #size-cells = <0>;
+
+ 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>;
+ };
+ };
+ };
+ };
--
2.51.0
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