imx6ull Linux使用设备树配置LED

Posted 2023-03-03 Wireless_Link

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我们基于寄存器的方式已经编写了LED驱动，实现点亮/熄灭LED，但是你有没有发现一个问题，就是假设LED修改了一个GPIO，那么需要对应的修改寄存器代码，非常繁琐，而且随着改板次数增加，那么会带来一个灾难性的重复性没有技术含量的重复工作的弊端。

在之前的文档我们已经介绍了LED寄存器实现方式：https://blog.csdn.net/XiaoXiaoPengBo/article/details/128684419?spm=1001.2014.3001.5501

并且我们之前文档也写过了设备树相关的概念内容：

https://blog.csdn.net/XiaoXiaoPengBo/article/details/128734828?spm=1001.2014.3001.5501

那么本节，我们就结合之前的内容把他利用起来！！！我们还是用之前的LED GPIO1_3

一. 修改设备树dts文件

1.修改dts文件内容

在根节点下增加一下内容

wireless_link_led
    #address-cells = <1>;
    #size-cells = <1>;
    compatible = "wl_led";
    status = "ok";
    reg = < 0X020C406C 0X04 /* CCM_CCGR1_BASE */
            0X020E0068 0X04 /* SW_MUX_GPIO1_IO03_BASE */
            0X020E02F4 0X04 /* SW_PAD_GPIO1_IO03_BASE */
            0X0209C000 0X04 /* GPIO1_DR_BASE */
            0X0209C004 0X04 >; /* GPIO1_GDIR_BASE */
;

2.编译dts验证

make dtbs

二. 实现LED基于设备树的驱动

#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/ide.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/errno.h>
#include <linux/gpio.h>
#include <linux/of_address.h>
#include <linux/of.h>
#include <asm/mach/map.h>
#include <asm/uaccess.h>
#include <asm/io.h>


#define LED_MAJOR        200
#define LED_NAME        "led"

static struct class *led_class;
struct device_node *led_nd;



static void __iomem *IMX6U_CCM_CCGR1;
static void __iomem *SW_MUX_GPIO1_IO03;
static void __iomem *SW_PAD_GPIO1_IO03;
static void __iomem *GPIO1_DR;
static void __iomem *GPIO1_GDIR;


static int led_open(struct inode *inode, struct file *filp)

    printk("led_open\\r\\n");
    return 0;



static ssize_t led_read(struct file *filp, char __user *buf, size_t cnt, loff_t *offt)

    printk("led_read\\r\\n");
    return 0;


static ssize_t led_write(struct file *filp, const char __user *buf, size_t cnt, loff_t *offt)

    printk("led_write\\r\\n");
    int retvalue;
    u32 val = 0;
    unsigned char databuf[1];
    unsigned char ledstat;

    retvalue = copy_from_user(databuf, buf, cnt);
    if(retvalue < 0) 
        printk("kernel write failed!\\r\\n");
        return -EFAULT;
    

    ledstat = databuf[0];

    printk("ledstat:%d\\r\\n",ledstat);

    if(ledstat == 1)
    
        val = readl(GPIO1_DR);
        val &= ~(1 << 3);    
        writel(val, GPIO1_DR);
    
    else if(ledstat == 0)
    
        val = readl(GPIO1_DR);
        val|= (1 << 3);    
        writel(val, GPIO1_DR);
    

    return 1;



static int led_release(struct inode *inode, struct file *filp)

    printk("led_release\\r\\n");
    return 0;




static struct file_operations led_fops = 
    .owner = THIS_MODULE,
    .open = led_open,
    .read = led_read,
    .write = led_write,
    .release =     led_release,
;


static int __init led_driver_init(void)

    u8 index;
    u32 val = 0;
    int ret = 0;
    const char *str;
    u32 regdata[14];
    struct property *proper;
    printk("led_driver_init\\r\\n");

    led_nd = of_find_node_by_path("/wireless_link_led");
    if(led_nd)
        printk("led nd found\\r\\n");
    else
    
        printk("led nd is not found\\r\\n");
        return -1;
    

    proper = of_find_property(led_nd, "compatible", NULL);
    if(proper)
        printk("compatible = %s\\r\\n", (char*)proper->value);
    else
        printk("compatible property find failed\\r\\n");

    ret = of_property_read_string(led_nd, "status", &str);
    printk("of_property_read_string ret:%d\\r\\n",ret);
    if(ret >= 0)
        printk("status = %s\\r\\n",str);

    ret = of_property_read_u32_array(led_nd, "reg", regdata, 10);
    printk("of_property_read_string ret:%d\\r\\n",ret);

    printk("---------------------------\\r\\n");
    for(index = 0; index < 10; index++)
        printk("%#X ", regdata[index]);
    printk("\\r\\n---------------------------\\r\\n");

    IMX6U_CCM_CCGR1 = of_iomap(led_nd, 0);
    SW_MUX_GPIO1_IO03 = of_iomap(led_nd, 1);
    SW_PAD_GPIO1_IO03 = of_iomap(led_nd, 2);
    GPIO1_DR = of_iomap(led_nd, 3);
    GPIO1_GDIR = of_iomap(led_nd, 4);

    val = readl(IMX6U_CCM_CCGR1);
    val &= ~(3 << 26);
    val |= (3 << 26);
    writel(val, IMX6U_CCM_CCGR1);

    writel(5, SW_MUX_GPIO1_IO03);

    writel(0x10B0, SW_PAD_GPIO1_IO03);

    val = readl(GPIO1_GDIR);
    val &= ~(1 << 3);
    val |= (1 << 3);
    writel(val, GPIO1_GDIR);

    val = readl(GPIO1_DR);
    val |= (1 << 3);    
    writel(val, GPIO1_DR);
    
    ret = register_chrdev(LED_MAJOR, LED_NAME, &led_fops);
    if(ret < 0)
        printk("register chrdev failed!\\r\\n");
        return -EIO;
    
    
    led_class = class_create(THIS_MODULE,"led_class");

    device_create(led_class,NULL,MKDEV(LED_MAJOR,0),NULL,"led"); /* /dev/led */
    
    return 0;


static void __exit led_driver_exit(void)

    printk("led_driver_exit\\r\\n");

    iounmap(IMX6U_CCM_CCGR1);
    iounmap(SW_MUX_GPIO1_IO03);
    iounmap(SW_PAD_GPIO1_IO03);
    iounmap(GPIO1_DR);
    iounmap(GPIO1_GDIR);
    device_destroy(led_class,MKDEV(LED_MAJOR,0));
    class_destroy(led_class);
    unregister_chrdev(LED_MAJOR, LED_NAME);


module_init(led_driver_init);
module_exit(led_driver_exit);
MODULE_LICENSE("GPL");

三. 实现APP验证程序

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>



int main(int argc, char *argv[])

    int fd;
    int ret;
    uint8_t led;
    fd  = open(argv[1], O_RDWR);

    if(!strcmp("led_on",argv[2]))
    
        printf("led on\\r\\n");
        led = 1;
        write(fd,&led,sizeof(led));
    

    if(!strcmp("led_off",argv[2]))
    
        led = 0;
        printf("led on\\r\\n");
        write(fd,&led,sizeof(led));
    

    
    close(fd);

四. 验证

点亮 LED灯 ./test_app /dev/led led_on

熄灭 LED灯 ./test_app /dev/led led_on

五.总结

其实到了这一步虽然不需要配对寄存器地址，但是代码还在编写寄存器代码，也就是说换了一个GPIO还是要修改代码，是的！！！别急，后续我们看了GPIO子系统以及pinctl子系统后相信会有答案！！！