全志A64 设备树里的gpio应用开发

通过A64手册可以看出共有两个普通gpio控制器:

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gpio控制器是由厂商负责驱动好的，在设备树里关于gpio控制器的描述:

  pio: [e-mail]01c20800 {
   compatible = "allwinner,sun50i-pinctrl";
   reg = <0x0 0x01c20800 0x0 0x400>;
   interrupts = <0 11 4>,
         <0 17 4>,
         <0 21 4>;
   device_type = "pio";
   clocks = <&clk_pio>;
   gpio-controller;
   interrupt-controller;
   #interrupt-cells = <2>;
   #size-cells = <0>;
   #gpio-cells = <6>;   

  r_pio: [e-mail]01f02c00 {
   compatible = "allwinner,sun50i-r-pinctrl";
   reg = <0x0 0x01f02c00 0x0 0x400>;
   interrupts = <0 45 4>;
   clocks = <&clk_cpurpio>;
   device_type = "r_pio";

   gpio-controller;
   interrupt-controller;
   #interrupt-cells = <2>;
   #size-cells = <0>;
   #gpio-cells = <6>;

其中“ #gpio-cells ＝ <6>”表示在设备树里描述使用一个gpio口需要提供6个指定的参数.

通过文档，可以得知6个参数的分别作用:

 gpio = <&pio   1   1   1   1   1  0>;
    |      |    |   |   |   |   |  |-------------------表示有效电平
    |      |    |   |   |   |   |----------------------上下拉, 0关闭功能, 1上拉, 2下拉, 3保留
    |      |    |   |   |   |-------------------------驱动力,电流等级(0 - 3)，级别越高，输出电流越大
    |      |    |   |   |----------------------------gpio功能类型,0输入, 1输出, 6和外部中断,7关闭功能(具体查手册)
    |      |    |   |------------------------------pin bank 内偏移(即组内第几个io口).
    |      |    |---------------------------------哪组gpio, PA(0),PB(1),PC(2),PD(3),PE(4),PF(5),PG(6),PH(7),PI(8),PJ(9),PK(10),PL(11)
    |      |--------------------------------------指向哪个gpio控制器,  pio / r_pio(PL组)
    |-----------------------------------------------------属性名字(随便命名)

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获取设备树里设备节点的gpio口信息:

#include <linux/of_gpio.h>

//只需一个函数即可
int of_get_named_gpio_flags(struct device_node *np, const char *propname,
    int index, enum of_gpio_flags *flags);

//返回值为int类型的gpio口.
//np为设备或设备子节点对象, propname为指定的属性名字, index表示获取属性里的第几个值
// 其中flags一定得注意，按文档里的说明应就是一个int类型的值，但根本就不能为int参数(会导致kernel panic)，
// 通过阅读内核里的代码得出， flags的参数应为struct gpio_config类型. 定义在下面文件:
"include/linux/sys_config.h"
struct gpio_config {
     u32 gpio;       /* gpio global index, must be unique */
     u32     mul_sel;    /* multi sel val: 0 - input, 1 - output... */
     u32     pull;       /* pull val: 0 - pull up/down disable, 1 - pull up... */
     u32     drv_level;  /* driver level val: 0 - level 0, 1 - level 1... */
     u32 data;       /* data val: 0 - low, 1 - high, only vaild when mul_sel is input/output */
 };

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获取到int类型的gpio口后，就可以使用linux/gpio.h里的gpio口操作函数:

#include <linux/gpio.h> //里面声明io口的操作函数

int gpio_request(unsigned gpio, const char *label);//每个io只能被请求一次,可防止多个驱动来控制同一个IO口
void gpio_free(unsigned gpio); //释放已请求的io口

int gpio_direction_input(unsigned gpio); //把指定的IO口作输入功能, gpio用于指定具体哪个io口
int gpio_direction_output(unsigned gpio, int value); //作输出功能，并根据value的值输出高低电平

int gpio_get_value(unsigned gpio); //获取指定IO口的电平
void gpio_set_value(unsigned gpio, int value); //设置IO口的电平为value(0/1)

int gpio_to_irq(unsigned gpio);  //根据io口，获取到它对应的中断号(io口大都有外部中断功能)

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应用例子，如图板上有两个led,和一个蜂鸣器:

设备树里的描述:

 jkbuzzer {
   compatible = "jk,buzzer";
   gpios = <&pio 3 24 1 1 1 1>; 
 };

 jkleds {
   compatible = "jk,leds";
   gpios = <&r_pio 11 10 1 1 1 1>, <&r_pio 11 12 1 1 1 1>;
 };

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蜂鸣器的测试代码 ：

#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/gpio.h>
#include <linux/sys_config.h>
#include <linux/delay.h>

int myprobe(struct platform_device *pdev)
{
    struct device_node *nd = pdev->dev.of_node;
    int gpio;   
    struct gpio_config config;


    printk("gpio count:%d\n", of_gpio_named_count(nd, "gpios"));
    gpio = of_get_named_gpio_flags(nd, "gpios", 0, (enum of_gpio_flags *)&config);
    if (!gpio_is_valid(gpio))
        printk("gpio isn't valid\n");
    if (gpio_request(gpio, pdev->name) < 0)
            printk("gpio request failed %d\n", gpio);

    gpio_direction_output(gpio, 1);
    msleep(3000);
    gpio_direction_input(gpio);
    gpio_free(gpio);
    return 0;
}

int myremove(struct platform_device *pdev)
{
    printk("in myremove ...\n");
    return 0;
}

struct of_device_id ids[] = {
    {.compatible = "jk,buzzer"},
    {},
};

struct platform_driver mydrv = {
    .probe = myprobe,
    .remove = myremove,

    .driver = {
        .owner = THIS_MODULE,
        .name = "mydrv" ,

        .of_match_table = ids,
    },
};

module_platform_driver(mydrv);
MODULE_LICENSE("GPL");

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两个led灯的测试代码:

#include <linux/init.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/of.h>
#include <linux/of_gpio.h>
#include <linux/gpio.h>
#include <linux/sys_config.h>
#include <linux/delay.h>

int myprobe(struct platform_device *pdev)
{
    struct device_node *nd = pdev->dev.of_node;
    int gpio, n, i; 
    struct gpio_config config;


    n = of_gpio_named_count(nd, "gpios");
    for (i = 0; i < n ; i++)
    {
        gpio = of_get_named_gpio_flags(nd, "gpios", i, (enum of_gpio_flags *)&config);
        if (!gpio_is_valid(gpio))
            printk("gpio isn't valid\n");
        if (gpio_request(gpio, pdev->name) < 0)
            printk("gpio request failed %d\n", gpio);

        gpio_direction_output(gpio, 1);
        msleep(3000);
        gpio_direction_input(gpio);
        gpio_free(gpio);
    }
    return 0;
}

int myremove(struct platform_device *pdev)
{
    printk("in myremove ...\n");
    return 0;
}

struct of_device_id ids[] = {
    {.compatible = "jk,leds"},
    {},
};

struct platform_driver mydrv = {
    .probe = myprobe,
    .remove = myremove,

    .driver = {
        .owner = THIS_MODULE,
        .name = "mydrv" ,

        .of_match_table = ids,
    },
};

module_platform_driver(mydrv);
MODULE_LICENSE("GPL");