GPIO 实例

本节适配硬件才能观察 GPIO 的情况, 因此需要开发板.

1 基本模板

首先改变原本的设备树.

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 // LED
leds {
	compatible = "gpio-leds";
	// status = "okay";
       // we will test our driver
       status = "disabled";
	heart_led {
		label = "run";
		gpios = <&gpio1 RK_PB3 GPIO_ACTIVE_LOW>;
		linux,default-trigger = "heartbeat";
		default-state = "off";
	};
};

   my_managed_device {
       compatible = "my,pin-manager";
       my-run-gpios = <&gpio1 RK_PB3 GPIO_ACTIVE_LOW>;
       status = "okay";
   };

内核程序.

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#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/gpio/consumer.h>
#include <linux/slab.h>    // for kzalloc, kfree
#include <linux/device.h>  // for device attributes
#include <linux/of.h>

/*
 * my_managed_device {
 *     compatible = "my,pin-manager";
 *     my-run-gpios = <&gpio1 RK_PB3 GPIO_ACTIVE_LOW>;
 *     status = "okay";
 * };
 */
struct led_data {
    struct gpio_desc *led_desc;
};

/* sysfs store function */
static ssize_t led_ctrl_store(struct device *dev, struct device_attribute *attr,
                              const char *buf, size_t count)
{
    struct led_data *priv = dev_get_drvdata(dev);
    int ret, state;

    ret = kstrtoint(buf, 10, &state);
    if (ret < 0) return ret;

    gpiod_set_value(priv->led_desc, state);
    dev_info(dev, "User set LED to %d\n", state);

    return count;
}

/* sysfs show function */
static ssize_t led_ctrl_show(struct device *dev, struct device_attribute *attr,
                             char *buf)
{
    struct led_data *priv = dev_get_drvdata(dev);
    int val = gpiod_get_value(priv->led_desc);
    return sprintf(buf, "%d\n", val);
}

static DEVICE_ATTR(ctrl, 0644, led_ctrl_show, led_ctrl_store);

static int led_probe(struct platform_device *pdev)
{
    struct device *dev = &pdev->dev;
    struct led_data *priv;
    int ret;

    dev_info(dev, "LED Driver: Probing (Manual Mode)...\n");

    /* 
     * [devm version]: priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
     */
    priv = kzalloc(sizeof(*priv), GFP_KERNEL);
    if (!priv)
        return -ENOMEM;

    /*
     * [devm version]: priv->led_desc = devm_gpiod_get(dev, "my_led", GPIOD_OUT_LOW);
     */
    priv->led_desc = gpiod_get(dev, "my-run", GPIOD_OUT_LOW);
    if (IS_ERR(priv->led_desc)) {
        dev_err(dev, "Failed to get GPIO resource\n");
        ret = PTR_ERR(priv->led_desc);
        goto err_free_mem; 
    }

    platform_set_drvdata(pdev, priv);

    // create sysfs node
    ret = device_create_file(dev, &dev_attr_ctrl);
    if (ret) {
        dev_err(dev, "Failed to create sysfs node\n");
        goto err_free_gpio;
    }

    dev_info(dev, "Probe successful.\n");
    return 0;

err_free_gpio:
    gpiod_put(priv->led_desc);
err_free_mem:
    kfree(priv);
    return ret;
}

static int led_remove(struct platform_device *pdev)
{
    struct led_data *priv = platform_get_drvdata(pdev);
    struct device *dev = &pdev->dev;

    device_remove_file(dev, &dev_attr_ctrl);

    gpiod_set_value(priv->led_desc, 0);


    // [devm version]: don't need to put GPIO
    gpiod_put(priv->led_desc);
    dev_info(dev, "GPIO released.\n");

    // [devm version]: don't need to free memory
    kfree(priv);
    dev_info(dev, "Memory freed.\n");
    return 0;
}

static const struct of_device_id led_match[] = {
    { .compatible = "my,pin-manager" },
    { },
};

MODULE_DEVICE_TABLE(of, led_match);

static struct platform_driver led_driver = {
    .probe  = led_probe,
    .remove = led_remove,
    .driver = {
        .name = "demo-led-driver",
        .of_match_table = led_match,
    },
};

module_platform_driver(led_driver);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Jvle");

芯片的 GPIO 控制器开发厂商已经帮我们完成了.

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pinctrl: pinctrl {
    compatible = "rockchip,rk3506-pinctrl";
    rockchip,grf = <&ioc_grf>;
    rockchip,ioc1 = <&ioc1>;
    rockchip,pmu = <&ioc_pmu>;
    rockchip,rmio = <&grf_pmu>;
    #address-cells = <1>;
    #size-cells = <1>;
    ranges;

    gpio0: gpio@ff940000 {
        compatible = "rockchip,gpio-bank";
        reg = <0xff940000 0x200>;
        interrupts = <GIC_SPI 0 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 1 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 2 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 3 IRQ_TYPE_LEVEL_HIGH>;
        clocks = <&cru PCLK_GPIO0>, <&cru DBCLK_GPIO0>;

        gpio-controller;
        #gpio-cells = <2>; 
        gpio-ranges = <&pinctrl 0 0 32>;
        interrupt-controller;
        #interrupt-cells = <2>; 
    };

    gpio1: gpio@ff870000 {                                                                                                                                                          
        compatible = "rockchip,gpio-bank";
        reg = <0xff870000 0x200>;
        interrupts = <GIC_SPI 4 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 5 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 6 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 7 IRQ_TYPE_LEVEL_HIGH>;

        clocks = <&cru PCLK_GPIO1>, <&cru DBCLK_GPIO1>;

        gpio-controller;
        #gpio-cells = <2>;
        gpio-ranges = <&pinctrl 0 32 32>;
        interrupt-controller;
        #interrupt-cells = <2>;
    };

    gpio2: gpio@ff1c0000 {
        compatible = "rockchip,gpio-bank";
        reg = <0xff1c0000 0x200>;
        interrupts = <GIC_SPI 8 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 9 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 10 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 11 IRQ_TYPE_LEVEL_HIGH>;
        clocks = <&cru PCLK_GPIO2>, <&cru DBCLK_GPIO2>;

        gpio-controller;
        #gpio-cells = <2>;
        gpio-ranges = <&pinctrl 0 64 32>;
        interrupt-controller;
        #interrupt-cells = <2>;
    };

    gpio3: gpio@ff1d0000 {
        compatible = "rockchip,gpio-bank";
        reg = <0xff1d0000 0x200>;
        interrupts = <GIC_SPI 12 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 13 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 14 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 15 IRQ_TYPE_LEVEL_HIGH>;
        clocks = <&cru PCLK_GPIO3>, <&cru DBCLK_GPIO3>;

        gpio-controller;
        #gpio-cells = <2>;
        gpio-ranges = <&pinctrl 0 96 32>;
        interrupt-controller;
        #interrupt-cells = <2>;
    };

    gpio4: gpio@ff1e0000 {
        compatible = "rockchip,gpio-bank";
        reg = <0xff1e0000 0x200>;
        interrupts = <GIC_SPI 16 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 17 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 18 IRQ_TYPE_LEVEL_HIGH>,
                 <GIC_SPI 19 IRQ_TYPE_LEVEL_HIGH>;
        clocks = <&cru PCLK_GPIO4>, <&cru DBCLK_GPIO4>;

        gpio-controller;
        #gpio-cells = <2>;
        gpio-ranges = <&pinctrl 0 128 32>;
        interrupt-controller;
        #interrupt-cells = <2>;
    };
};

以 RK3506G 为例. 这里有 4 组 GPIO.

对 Rockchip 的 GPIO 编号计算公式为:

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GPIO_ID = (Bank * 32) + (Group * 8) + Index

对于开发板上的 LED, 查看手册得知, 编号为 GPIO1_B3, 即 gpiochip1 的 11 号.

可以看看 GPIO 现在的情况.

加载.

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$ insmod /tmp/gpio.ko
$ gpioinfo
...
gpiochip1 - 32 lines:
	line   0:      unnamed       unused   input  active-high 
	line   1:      unnamed       unused   input  active-high 
	line   2:      unnamed       unused   input  active-high 
	line   3:      unnamed       unused   input  active-high 
	line   4:      unnamed       unused   input  active-high 
	line   5:      unnamed       unused   input  active-high 
	line   6:      unnamed       unused   input  active-high 
	line   7:      unnamed       unused   input  active-high 
	line   8:      unnamed       unused   input  active-high 
	line   9:      unnamed       unused   input  active-high 
	line  10:      unnamed       unused   input  active-high 
	line  11:      unnamed     "my-run"  output   active-low [used]
...

卸载.

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$ rmmod /tmp/gpio.ko
$ gpioinfo
...
gpiochip1 - 32 lines:
	line   0:      unnamed       unused   input  active-high 
	line   1:      unnamed       unused   input  active-high 
	line   2:      unnamed       unused   input  active-high 
	line   3:      unnamed       unused   input  active-high 
	line   4:      unnamed       unused   input  active-high 
	line   5:      unnamed       unused   input  active-high 
	line   6:      unnamed       unused   input  active-high 
	line   7:      unnamed       unused   input  active-high 
	line   8:      unnamed       unused   input  active-high 
	line   9:      unnamed       unused   input  active-high 
	line  10:      unnamed       unused   input  active-high 
	line  11:      unnamed       unused  output  active-high

查看内核打印信息.

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# dmesg
[ 1057.636134] demo-led-driver my_managed_device: LED Driver: Probing (Manual Mode)...
[ 1057.636284] demo-led-driver my_managed_device: Probe successful.
[ 1070.288399] demo-led-driver my_managed_device: User set LED to 1
[ 1084.954286] demo-led-driver my_managed_device: User set LED to 0
[ 1091.455914] demo-led-driver my_managed_device: GPIO released.
[ 1091.455960] demo-led-driver my_managed_device: Memory freed.

指令执行情况.

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$ echo 1 >> /sys/devices/platform/my_managed_device/ctrl
# 灯亮
$ echo 0 >> /sys/devices/platform/my_managed_device/ctrl
# 灯灭