Milk-V Duo开发板免费体验 GPIO分析

设备树

下面截取gpio0的设备树，复制自：linux_5.10/arch/riscv/boot/dts/cvitek/cv180x_base.dtsi

gpio0: gpio@03020000 {
	compatible = "snps,dw-apb-gpio";
	reg = < 0x0 0x03020000 0x0 0x1000 >;
	#address-cells = < 1 >;
	#size-cells = < 0 >;

	porta: gpio-controller@0 {
		compatible = "snps,dw-apb-gpio-port";
		bank-name = "porta";
		gpio-controller;
		#gpio-cells = < 2 >;
		snps,nr-gpios = < 32 >;
		reg = < 0 >;
	};
};

以下是复制自：linux_5.10/arch/riscv/boot/dts/cvitek/cv180x_base_riscv.dtsi

gpio0: gpio@03020000 {
		porta: gpio-controller@0 {
			interrupt-controller;
			interrupts = < 60 IRQ_TYPE_LEVEL_HIGH >;
			interrupt-parent = < &plic0 >;
		};
	};

驱动

cv180x的GPIO控制器用到是dw-apb-gpio控制器驱动，驱动代码位于：linux_5.10/drivers/gpio/gpio-dwapb.c

#define DWAPB_DRIVER_NAME	"gpio-dwapb"

// 省略其他代码

static struct platform_driver dwapb_gpio_driver = {
	.driver		= {
		.name	= DWAPB_DRIVER_NAME,
		.pm	= &dwapb_gpio_pm_ops,
		.of_match_table = dwapb_of_match,
		.acpi_match_table = dwapb_acpi_match,
	},
	.probe		= dwapb_gpio_probe,
};

module_platform_driver(dwapb_gpio_driver);

关键函数是probe函数

// drivers/gpio/gpio-dwapb.c
dwapb_gpio_probe:

	dwapb_gpio_get_pdata(dev)

		device_for_each_child_node(dev, fwnode)  { //遍历设备树节点

			fwnode_property_read_u32(fwnode, "snps,nr-gpios", &pp->ngpio)

			fwnode_property_read_u32(fwnode, "reg", &pp->idx)

		}

		dwapb_gpio_add_port

			devm_gpiochip_add_data

				devm_gpiochip_add_data_with_key

					gpiochip_add_data_with_key //注册到gpiolib的gpio_devices中

gpio子系统

// drivers/gpio/gpiolib.c
struct gpio_desc *gpio_to_desc(unsigned gpio) //从gpio_devices获取gpio_desc

// include/asm-generic/gpio.h
// drivers/gpio/gpiolib-sysfs.c
gpio_export:
	gpiod_export(gpio_to_desc(gpio), direction_may_change)
		device_create_with_groups
			device_create_groups_vargs
				device_add
					kobject_add //添加到相关的设备模型子系统
					device_create_file //创建/sys下的设备属性文件
					... //其他相关设置

小结

通过上面的3块，就实现了/sys/class/gpio/export导出gpio的过程即对gpio的操作。

关于gpio的相关操作函数就在gpiolib.c里面。

审核编辑 黄宇