STM32MP157A驱动开发 | 01- 板载LED作为系统心跳指示灯

一、板载LED

此用户LED连接到PA13。

二、pinctrl描述

绑定文档：Documentation/devicetree/bindings/pinctrl/st,stm32-pinctrl.yaml。

必要的属性：

- compatible
  - '#address-cells'
  - '#size-cells'
  - ranges
  - pins-are-numbered

可用值如下：

:
    enum:
      - st,stm32f429-pinctrl
      - st,stm32f469-pinctrl
      - st,stm32f746-pinctrl
      - st,stm32f769-pinctrl
      - st,stm32h743-pinctrl
      - st,stm32mp157-pinctrl
      - st,stm32mp157-z-pinctrl

  '#address-cells':
    const: 1
  '#size-cells':
    const: 1

  ranges: true
  pins-are-numbered:

文档里给出了一个描述串口引脚的示例：

{
        usart1_pins_a: usart1-0 {
                pins1 {
                        pinmux = <STM32_PINMUX('A', 9, AF7)>;
                        bias-disable;
                        drive-push-pull;
                        slew-rate = <0>;
                };
                pins2 {
                        pinmux = <STM32_PINMUX('A', 10, AF7)>;
                        bias-disable;
                };
        };
    };

    usart1 {
                pinctrl-0 = <&usart1_pins_a>;
                pinctrl-names = "default";
    };

二、作为用户LED

1. 设备树描述

添加pinctrl描述，将PA13作为普通gpio：

&pinctrl {
  led_pins_a: led-0 {
    pins {
      pinmux = <STM32_PINMUX('A', 13, GPIO)>; /* USER_LED */
    };
  };
};

添加led节点描述：

{
    compatible = "gpio-leds";
    pinctrl-0 = <&led_pins_a>;

    blue {
      label = "blue";
      gpios = <&gpioa 13 GPIO_ACTIVE_LOW>;
      default-state = "off";
    };
  };

2. 测试

重新编译设备树，启动。

三、作为系统心跳LED

{
    compatible = "gpio-leds";
    pinctrl-0 = <&led_pins_a>;

    heartled {
      label = "heartled";
      gpios = <&gpioa 13 GPIO_ACTIVE_LOW>;
      linux,default-trigger = "heartbeat";
      default-state = "off";
    };
  };