1. 环境：
1.1 开发板：正点原子 I.MX6U ALPHA V2.2
1.2 开发PC：Ubuntu20.04
1.3 U-boot：uboot-imx-rel_imx_4.1.15_2.1.0_ga.tar.bz2
1.4 LInux内核：linux-imx-rel_imx_4.1.15_2.1.0_ga.tar.bz2
1.5 rootfs：busybox-1.29.0.tar.bz2制作
1.6 交叉编译工具链：gcc-linaro-4.9.4-2017.01-x86_64_arm-linux-gnueabihf.tar.xz
2. 硬件控制说明
2.1 由GPIO1 PIN3控制，高---熄灭， 低---点亮
3. 驱动代码
3.1 新建led.h头文件，添加如下代码
1 #ifndef __LED_H
2 #define __LED_H
3 #include <linux/cdev.h>
4
5 //GPIO寄存器地址，参考"i.MX 6ULL Applications Processor Reference Manual"
6 #define LED_GPIO1_3_BASE 0x0209c000
7 #define GPIO_DR 0x0
8 #define GPIO_GDIR 0x4
9 #define GPIO_PSR 0x8 //本驱动未使用到
10 #define GPIO_ICR1 0xc //本驱动未使用到
11 #define GPIO_ICR2 0x10 //本驱动未使用到
12 #define GPIO_IMR 0x14 //本驱动未使用到
13 #define GPIO_ISR 0x18 //本驱动未使用到
14 #define GPIO_EDGE_SEL 0x1c //本驱动未使用到
15
16 #define LED_GPIO1_3_MUX 0X020E0068 //GPIO复用功能选择寄存器地址
17 #define LED_GPIO1_3_PAD 0X020E02F4 //GPIO驱动方式选择寄存器地址
18 #define LED_GPIO1_3_CCM 0X020C406C //GPIO时钟寄存器地址
19
20 //led控制
21 #define LED_ON 1
22 #define LED_OFF 0
23 #define LED_MAJOR 249 //用于静态设备号申请
24
25
26 //自定义一个结构体，将一些需要的变量放在其中，以便管理
27 struct led_device
28 {
29 struct class *led_class;
30 struct device *led_device;
31 struct cdev led_cdev;
32 dev_t devno;
33 int major; //用于保存主设备号
34 void __iomem *led_dr; //保存GPIO数据寄存器内存映射后的地址
35 void __iomem *led_gdir; //保存GPIO输入输出方向选择寄存器内存映射后的地址
36 void __iomem *led_pd; //保存GPIO驱动方式选择寄存器内存映射后的地址
37 void __iomem *led_mux; //保存GPIO复用功能选择寄存器内存映射后的地址
38 void __iomem *led_ccm; //保存GPIO时钟寄存器内存映射后的地址
39 };
40
41
42 #endif
View Code
3.2 新建led_dev_platform.c文件，添加平台设备代码
1 #include <linux/init.h>
2 #include <linux/module.h>
3 #include <linux/ioport.h>
4 #include <linux/platform_device.h>
5 #include "led.h"
6
7 //填充平台资源结构体
8 struct resource led_resource[] = {
9 [0] = { //GPIO数据寄存器
10 .start = LED_GPIO1_3_BASE + GPIO_DR,
11 .end = LED_GPIO1_3_BASE + GPIO_DR + 4 -1,
12 .flags = IORESOURCE_MEM
13 },
14
15 [1] = { //GPIO方向寄存器
16 .start = LED_GPIO1_3_BASE + GPIO_GDIR,
17 .end = LED_GPIO1_3_BASE + GPIO_GDIR + 4 -1,
18 .flags = IORESOURCE_MEM
19 },
20
21 [2] = { //GPIO复用功能寄存器
22 .start = LED_GPIO1_3_MUX,
23 .end = LED_GPIO1_3_MUX + 4 -1,
24 .flags = IORESOURCE_MEM
25 },
26
27 [3] = { //GPIO驱动方式寄存器
28 .start = LED_GPIO1_3_PAD,
29 .end = LED_GPIO1_3_PAD + 4 -1,
30 .flags = IORESOURCE_MEM
31 },
32
33 [4] = { //GPIO时钟寄存器
34 .start = LED_GPIO1_3_CCM,
35 .end = LED_GPIO1_3_CCM + 4 -1,
36 .flags = IORESOURCE_MEM
37 },
38
39 };
40
41
42 static void led_release(struct device *dev)
43 {
44
45 }
46
47 //填充平台结构体
48 struct platform_device led_gpio_device = {
49 .name = "led_gpio",
50 // .name = "imx6ul-led",
51 .id = 1,
52 .resource = led_resource,
53 .num_resources = ARRAY_SIZE(led_resource),
54 .dev = {
55 .release = led_release,
56 },
57 };
58
59
60 static int __init led_dev_platform_init(void)
61 {
62 //注册平台设备
63 platform_device_register(&led_gpio_device);
64 return 0;
65 }
66
67
68 static void __exit led_dev_platform_exit(void)
69 {
70 //注销平台设备
71 platform_device_unregister(&led_gpio_device);
72 }
73
74
75 module_init(led_dev_platform_init);
76 module_exit(led_dev_platform_exit);
77 MODULE_LICENSE("Dual BSD/GPL");
View Code
3.3 新建led_drv_platform.c文件，添加平台驱动代码
1 #include <linux/init.h>
2 #include <linux/module.h>
3 #include <linux/fs.h> //文件操作函数,file_operarions
4 #include <linux/device.h> //设备申请函数,device_create
5 #include <linux/platform_device.h>
6 #include <linux/slab.h> //内核空间申请函数件,kmalloc
7 #include <asm/uaccess.h> //内核与用户空间消息拷贝函数,copy_to_usser & copy_from_user
8 #include <asm/io.h> //内存地址映射函数,ioremap
9 #include <linux/cdev.h>
10 #include "led.h"
11
12
13 static struct led_device *imx_led_gpio1_3;
14
15 //设备文件的open操作函数
16 static int led_open(struct inode *inode, struct file *file)
17 {
18
19 return 0;
20 }
21
22 //设备文件的close操作函数
23 static int led_close(struct inode *inode, struct file *file)
24 {
25 return 0;
26 }
27
28 //设备文件的read操作函数
29 static ssize_t led_read(struct file *file, char __user *buf, size_t size, loff_t *f_ops)
30 {
31 return 0;
32 }
33
34 //设备文件的write操作函数
35 static ssize_t led_write(struct file *file, const char __user *buf, size_t size, loff_t *f_ops)
36 {
37 int ret;
38 unsigned char cmd[1];
39 u32 val = 0;
40
41 ret = copy_from_user(cmd, buf, size);
42 if(ret < 0)
43 {
44 printk("kernel write failed!\r\n");
45 return -EFAULT;
46 }
47
48
49 if(*cmd == LED_ON)
50 {
51 val = readl(imx_led_gpio1_3->led_dr);
52 val &= ~(1 << 3);
53 writel(val, imx_led_gpio1_3->led_dr);
54 }
55 else if(*cmd == LED_OFF)
56 {
57 val = readl(imx_led_gpio1_3->led_dr);
58 val|= (1 << 3);
59 writel(val, imx_led_gpio1_3->led_dr);
60 }
61 else
62 {
63 printk("led command is invalid!\n");
64 return -2;
65 }
66
67 return 0;
68 }
69
70 static long led_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
71 {
72 u32 val = 0;
73 switch (cmd)
74 {
75 case LED_OFF:
76 val = readl(imx_led_gpio1_3->led_dr);
77 val|= (1 << 3);
78 writel(val, imx_led_gpio1_3->led_dr);
79 break;
80 case LED_ON:
81 val = readl(imx_led_gpio1_3->led_dr);
82 val &= ~(1 << 3);
83 writel(val, imx_led_gpio1_3->led_dr);
84 break;
85 default:
86 val = readl(imx_led_gpio1_3->led_dr);
87 val|= (1 << 3);
88 writel(val, imx_led_gpio1_3->led_dr);
89 break;
90 }
91
92
93 return 0;
94 }
95
96 //填充file_operations结构体
97 static const struct file_operations led_fops = {
98 .owner = THIS_MODULE,
99 .open = led_open,
100 .release = led_close,
101 .write = led_write,
102 .read = led_read,
103 .unlocked_ioctl = led_ioctl,
104 };
105
106
107 static int led_gpio_probe(struct platform_device *pdev)
108 {
109 int ret = -2;
110 int i;
111 u32 val = 0;
112 struct resource *res[5];
113 int ressize[5];
114
115 //为自定义机构提申请内核内存
116 imx_led_gpio1_3 = kmalloc(sizeof(struct led_device), GFP_KERNEL);
117 if(imx_led_gpio1_3 == NULL)
118 {
119 printk(KERN_ERR "kmalloc fail!\n");
120 return -ENOMEM;
121 }
122
123
124 //ret = register_chrdev(LED_MAJOR, "led", &led_fops);
125 //如果使用动态申请，则必须使用cdev_init() & cdev_add()这两个函数；静态则不需要
126 ret = alloc_chrdev_region(&imx_led_gpio1_3->devno, 0, 1, "led");
127 if(ret < 0)
128 {
129 printk(KERN_ERR "register major failed!\n");
130 ret = -EINVAL;
131 goto err1;
132 }
133
134
135 imx_led_gpio1_3->major = MAJOR(imx_led_gpio1_3->devno);
136 imx_led_gpio1_3->led_cdev.owner = THIS_MODULE;
137
138 //dev_major = MAJOR(devno);
139 imx_led_gpio1_3->led_cdev.owner = THIS_MODULE;
140
141 //将设备与文件操作函数关联
142 cdev_init(&imx_led_gpio1_3->led_cdev, &led_fops);
143
144 //注册设备
145 cdev_add(&imx_led_gpio1_3->led_cdev,imx_led_gpio1_3->devno, 1);
146
147 //创建设备类
148 imx_led_gpio1_3->led_class = class_create(THIS_MODULE, "led_class");
149 if(IS_ERR(imx_led_gpio1_3->led_class))
150 {
151 printk(KERN_ERR "failed to create class!\n");
152 ret = PTR_ERR(imx_led_gpio1_3->led_class);
153 goto err2;
154 }
155
156
157 //创建设备文件，此函数最后一个参数led，其实就是设备名，应用程序open打开的也是这个文件名
158 imx_led_gpio1_3->led_device = device_create(imx_led_gpio1_3->led_class, NULL, imx_led_gpio1_3->devno, NULL, "led");
159 if(IS_ERR(imx_led_gpio1_3->led_device))
160 {
161 printk(KERN_ERR "failed to create device!\n");
162 ret = PTR_ERR(imx_led_gpio1_3->led_device);
163 goto err3;
164 }
165
166 //获取设备资源
167 for(i = 0; i < 5; i++)
168 {
169 res[i] = platform_get_resource(pdev, IORESOURCE_MEM, i);
170 if(!res[i])
171 {
172 dev_err(&pdev->dev, "No MEM resource for always on \n");
173 return -ENXIO;
174 }
175 ressize[i] = resource_size(res[i]);
176 }
177
178
179 //对物理地址进行内存映射,以便后面操作
180 imx_led_gpio1_3->led_dr = ioremap(res[0]->start, ressize[0]);
181 if(imx_led_gpio1_3->led_dr == NULL)
182 {
183 printk(KERN_ERR "led_dr ioremap fail!\n");
184 ret = -ENOMEM;
185 goto err4;
186 }
187
188 imx_led_gpio1_3->led_gdir = ioremap(res[1]->start, ressize[1]);
189 if(imx_led_gpio1_3->led_gdir == NULL)
190 {
191 printk(KERN_ERR "led_gdir ioremap fail!\n");
192 ret = -ENOMEM;
193 goto err4;
194 }
195
196 imx_led_gpio1_3->led_mux = ioremap(res[2]->start, ressize[2]);
197 if(imx_led_gpio1_3->led_mux == NULL)
198 {
199 printk(KERN_ERR "led_mux ioremap fail!\n");
200 ret = -ENOMEM;
201 goto err4;
202 }
203
204 imx_led_gpio1_3->led_pd = ioremap(res[3]->start, ressize[3]);
205 if(imx_led_gpio1_3->led_pd == NULL)
206 {
207 printk(KERN_ERR "led_pd ioremap fail!\n");
208 ret = -ENOMEM;
209 goto err4;
210 }
211
212
213 imx_led_gpio1_3->led_ccm = ioremap(res[4]->start, ressize[4]);
214 if(imx_led_gpio1_3->led_ccm == NULL)
215 {
216 printk(KERN_ERR "led_ccm ioremap fail!\n");
217 ret = -ENOMEM;
218 goto err4;
219 }
220
221 // 使能GPIO1时钟
222 val = readl(imx_led_gpio1_3->led_ccm);
223 val &= ~(3 << 26); //清掉旧值
224 val |= (3 << 26); // 设置新值
225 writel(val, imx_led_gpio1_3->led_ccm);
226
227 // 将GPIO1_IO03复用功能设置为GPIO
228 writel(5, imx_led_gpio1_3->led_mux);
229
230 // 设置GPIO的电流驱动能力
231 writel(0x10B0, imx_led_gpio1_3->led_pd);
232
233 // 设置GPIO的输入输出方向
234 val = readl(imx_led_gpio1_3->led_gdir);
235 val &= ~(1 << 3); // 清除以前的设置
236 val |= (1 << 3); // 设置为输出
237 writel(val, imx_led_gpio1_3->led_gdir);
238
239
240 //设置LED的默认状态:LED熄灭
241 val = readl(imx_led_gpio1_3->led_dr);
242 val |= (1 << 3);
243 writel(val, imx_led_gpio1_3->led_dr);
244
245 return 0;
246
247 //注销设备节点
248 err4:
249 device_destroy(imx_led_gpio1_3->led_class, imx_led_gpio1_3->major);
250
251 //注销设备类
252 err3:
253 class_destroy(imx_led_gpio1_3->led_class);
254
255 //注销设备号
256 err2:
257 unregister_chrdev(imx_led_gpio1_3->major, "led");
258
259 //释放由kmalloc申请的内存
260 err1:
261 kfree(imx_led_gpio1_3);
262 return ret;
263
264 }
265
266
267 static int led_gpio_remove(struct platform_device *pdev)
268 {
269 device_destroy(imx_led_gpio1_3->led_class, imx_led_gpio1_3->major);
270 class_destroy(imx_led_gpio1_3->led_class);
271 unregister_chrdev(imx_led_gpio1_3->major, "led");
272 iounmap(imx_led_gpio1_3->led_dr);
273 iounmap(imx_led_gpio1_3->led_gdir);
274 iounmap(imx_led_gpio1_3->led_pd);
275 iounmap(imx_led_gpio1_3->led_mux);
276 iounmap(imx_led_gpio1_3->led_ccm);
277 kfree(imx_led_gpio1_3);
278
279 return 0;
280 }
281
282 struct platform_device_id led_ids[] = {
283 [0] = {
284 .name = "led_gpio",
285 .driver_data = 0,
286 },
287 };
288
289 struct platform_driver led_gpio_driver = {
290 .probe = led_gpio_probe,
291 .remove = led_gpio_remove,
292 .driver = {
293 .owner = THIS_MODULE,
294 .name = "led_gpio"
295 },
296 .id_table = led_ids //当成员driver中的name成员不匹配时，从成员id_table中寻找
297 };
298
299 static int __init led_init(void)
300 {
301 platform_driver_register(&led_gpio_driver);
302 return 0;
303 }
304
305 static void __exit led_exit(void)
306 {
307 platform_driver_unregister(&led_gpio_driver);
308 }
309
310 module_init(led_init);
311 module_exit(led_exit);
312 MODULE_LICENSE("Dual BSD/GPL");
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4. 测试代码
1 #include <stdio.h>
2 #include <stdlib.h>
3 #include <sys/types.h>
4 #include <sys/stat.h>
5 #include <fcntl.h>
6
7 #define LED_ON 1
8 #define LED_OFF 0
9
10
11 int main(int argc, char **argv)
12 {
13 int fd;
14 int buf = 0;
15
16 fd = open("/dev/led", O_RDWR);
17
18 printf("fd = %d\n", fd);
19 if(fd < 0)
20 {
21 perror("open fail!\n");
22
23 exit(1);
24 }
25
26 #if 0
27
28 if(strcmp(argv[1], "on") == 0)
29 {
30 if(ioctl(fd, LED_ON) < 0)
31 perror("ioctrl fail:led on\n");
32 else
33 printf("ioctl ok:led on\n");
34 }
35 else if(strcmp(argv[1], "off") == 0)
36 {
37 if(ioctl(fd, LED_OFF) < 0)
38 perror("ioctrl fail:led off\n");
39 else
40 printf("ioctl ok:led off\n");
41 }
42 else
43 {
44 perror("command is invalid!\n");
45 }
46
47
48 #else
49 if(strcmp(argv[1], "on") == 0)
50 {
51 buf = 1;
52 if(write(fd, &buf, sizeof(buf)) < 0)
53 {
54 perror("write fail:led on!\n");
55 exit(1);
56 }
57 else
58 {
59 printf("write ok:led on!\n");
60 }
61 }
62 else if(strcmp(argv[1], "off") == 0)
63 {
64 buf = 0;
65 if(write(fd, &buf, sizeof(buf)) < 0)
66 {
67 perror("write fail:led off!\n");
68 exit(1);
69 }
70 else
71 {
72 printf("write ok:led off!\n");
73 }
74 }
75 else
76 {
77 perror("command is invalid!\n");
78 }
79
80
81 #endif
82
83 close(fd);
84 return 0;
85 }
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总结：
1. 当平台设备有多个资源时，平台驱动需要逐个获取
2. 注意平台设备驱动与平台驱动匹配的条件