Linux PWM驱动调试
CPU:RK3288
系统:Linux
客户需求是通过 pwm 控制激光的强弱,写驱动前,需要先了解几个相关的概念和相关函数
概念:
PWM:脉冲宽度调试(Pulse width modulation),最典型的应用是调节 LED 的亮度
占空比:高电平或者低电平时间占一个周期时间的比例
驱动中 pwm 相关函数:
/*
* 功能:申请pwm设备
* pwm_id:pwm编号
* label:自定义名称
*/
struct pwm_device *pwm_request(int pwm_id, const char *label);
/*
* 功能:释放pwm设备
* pwm:pwm申请到的设备
*/
void pwm_free(struct pwm_device *pwm);
/*
* 功能:使能pwm
* pwm:pwm申请到的设备
*/
int pwm_enable(struct pwm_device *pwm);
/*
* 功能:失能pwm
* pwm:pwm申请到的设备
*/
void pwm_disable(struct pwm_device *pwm);
/*
* 功能:设置pwm周期
* pwm:pwm申请到的设备
* period:pwm周期时间,单位为ns
*/
void pwm_set_period(struct pwm_device *pwm, unsigned int period);
/*
* 功能:获取pwm周期
* pwm:pwm申请到的设备
* 返回值:pwm周期时间,单位为ns
*/
unsigned int pwm_get_period(struct pwm_device *pwm);
/*
* 功能:设置pwm有效极性
* pwm:pwm申请到的设备
* polarity:pwm有效极性 PWM_POLARITY_NORMAL / PWM_POLARITY_INVERSED
*/
int pwm_set_polarity(struct pwm_device *pwm, enum pwm_polarity polarity);
/*
* 功能:配置pwm
* pwm:pwm申请到的设备
* duty_ns:pwm占空比时间,单位为ns
* period_ns:pwm周期时间,单位为ns
*/
int pwm_config(struct pwm_device *pwm, int duty_ns, int period_ns);
根据需求,底层给用户提供四个功能接口,包括设置周期时间、获取当前周期时间、设置占空比、获取当前占空比
1、在 dts 中配置 pwm 默认参数
pwm-laser {
compatible = "pwm-laser";
status = "okay";
/* pwm1 */
pwm-id = <1>;
/* pwm1周期为1ms */
period = <1000000>;
/* 占空比默认为0 */
default-level = <0>;
};
&pwm1 {
status = "okay";
};
2、编写 pwm 驱动,按照需求为用户提供接口
#include <linux/gpio.h>
#include <linux/of_gpio.h>
#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/uaccess.h>
#include <linux/fs.h>
#include <linux/platform_device.h>
#include <linux/fb.h>
#include <linux/err.h>
#include <linux/pwm.h>
#include <linux/slab.h>
#include <linux/miscdevice.h>
#include <linux/delay.h>
#define PWM_LASER_SET_PERIOD _IOW('A', 0x11, unsigned int)
#define PWM_LASER_GET_PERIOD _IOR('A', 0x12, unsigned int)
#define PWM_LASER_SET_DUTY _IOW('A', 0x13, unsigned int)
#define PWM_LASER_GET_DUTY _IOR('A', 0x14, unsigned int)
#define PWM_LASER_ENABLE _IO('A', 0x15)
#define PWM_LASER_DISABLE _IO('A', 0x16)
struct pwm_para {
int pwm_id;
unsigned int period;
unsigned int level;
unsigned int duty;
struct pwm_device *pwm;
};
struct pwm_para laser;
static void pwm_laser_update(void)
{
laser.duty = laser.level * laser.period / 100;
pwm_config(laser.pwm, laser.duty, laser.period);
}
static void pwm_laser_enable(void)
{
pwm_enable(laser.pwm);
}
static void pwm_laser_disable(void)
{
// 关闭pwm之前将占空比设置为0
laser.level = 0;
pwm_laser_update();
pwm_disable(laser.pwm);
}
static void pwm_laser_set_period(unsigned int period)
{
laser.period = period * 1000000;
pwm_set_period(laser.pwm, laser.period);
}
static unsigned int pwm_laser_get_period(void)
{
return (laser.period / 1000000);
}
static int pwm_laser_open(struct inode *inode, struct file *filp)
{
return 0;
}
static int pwm_laser_release(struct inode *inode, struct file *filp)
{
pwm_laser_disable();
return 0;
}
static ssize_t pwm_laser_read(struct file *filp, char __user *buf, size_t len, loff_t *pos)
{
return 0;
}
static ssize_t pwm_laser_write(struct file *filp, const char __user *buf, size_t len, loff_t *pos)
{
return 0;
}
static long pwm_laser_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
unsigned int period;
unsigned int level;
void __user *argp = (void __user *)arg;
switch (cmd)
{
case PWM_LASER_SET_PERIOD:
if (argp == NULL) {
printk("laser: invalid argument.");
return -EINVAL;
}
if (copy_from_user(&period, argp, sizeof(unsigned int))) {
printk("copy_from_user failed.");
return -EFAULT;
}
pwm_laser_set_period(period);
break;
case PWM_LASER_GET_PERIOD:
period = pwm_laser_get_period();
if (copy_to_user(argp, &period, sizeof(unsigned int))) {
printk("copy_to_user failed.");
return -EFAULT;
}
break;
case PWM_LASER_SET_DUTY :
if (argp == NULL) {
printk("laser: invalid argument.");
return -EINVAL;
}
if (copy_from_user(&level, argp, sizeof(unsigned int))) {
printk("copy_from_user failed.");
return -EFAULT;
}
if ((level < 0) || (level > 100)) {
printk("laser: invalid argument.");
return -EINVAL;
}
laser.level = level;
pwm_laser_update();
break;
case PWM_LASER_GET_DUTY :
if (copy_to_user(argp, &laser.level, sizeof(unsigned int))) {
printk("copy_to_user failed.");
return -EFAULT;
}
break;
case PWM_LASER_ENABLE:
pwm_laser_update();
pwm_laser_enable();
break;
case PWM_LASER_DISABLE:
pwm_laser_disable();
break;
default:
printk("laser: cmd error!\n");
return -EFAULT;
}
return 0;
}
struct file_operations pwm_laser_fops = {
.owner = THIS_MODULE,
.open = pwm_laser_open,
.release = pwm_laser_release,
.write = pwm_laser_write,
.read = pwm_laser_read,
.unlocked_ioctl = pwm_laser_ioctl,
};
struct miscdevice pwm_laser_dev =
{
.minor = MISC_DYNAMIC_MINOR,
.fops = &pwm_laser_fops,
.name = "pwm-laser",
};
static ssize_t pwm_laser_parse_dt(struct platform_device *pdev)
{
struct device_node *node = pdev->dev.of_node;
int ret;
if (!node) {
dev_err(&pdev->dev, "laser: Device Tree node missing\n");
return -EINVAL;
}
ret = of_property_read_u32(node, "pwm-id", &laser.pwm_id);
if (ret < 0) {
dev_err(&pdev->dev, "laser: pwm-id missing\n");
return ret;
}
ret = of_property_read_u32(node, "period", &laser.period);
if (ret < 0) {
dev_err(&pdev->dev, "laser: period missing\n");
return ret;
}
ret = of_property_read_u32(node, "default-level", &laser.level);
if (ret < 0) {
dev_err(&pdev->dev, "laser: default-level missing\n");
return ret;
}
return 0;
}
static void pwm_laser_test(void)
{
int i = 0, dir = 0;
pwm_laser_enable();
while (1)
{
if (dir == 0) {
laser.level = i++;
if (i == 100)
dir = 1;
} else {
laser.level = i--;
if (i == 0)
dir = 0;
}
pwm_laser_update();
msleep(100);
}
pwm_laser_disable();
}
static int pwm_laser_probe(struct platform_device *pdev)
{
int ret;
ret = pwm_laser_parse_dt(pdev);
if (ret < 0) {
dev_err(&pdev->dev, "laser: Device not found\n");
return -ENODEV;
}
laser.pwm = pwm_request(laser.pwm_id, "pwm-laser");
if (IS_ERR(laser.pwm)) {
dev_err(&pdev->dev, "laser: unable to request legacy PWM\n");
ret = PTR_ERR(laser.pwm);
return ret;
}
// 设置pwm参数
pwm_laser_update();
// 设置极性必须在设置参数之后,pwm使能之前,否则会设置失败
ret = pwm_set_polarity(laser.pwm, PWM_POLARITY_NORMAL);
if (ret < 0)
printk("pwm set polarity fail, ret = %d\n", ret);
// 调试完屏蔽使能函数,交由app控制
// pwm_laser_enable();
misc_register(&pwm_laser_dev);
// 调试完屏蔽测试函数
// pwm_laser_test();
return 0;
}
static int pwm_laser_remove(struct platform_device *pdev)
{
pwm_disable(laser.pwm);
pwm_free(laser.pwm);
misc_deregister(&pwm_laser_dev);
return 0;
}
int pwm_laser_suspend(struct device *dev)
{
return 0;
}
int pwm_laser_resume(struct device *dev)
{
return 0;
}
const struct dev_pm_ops pwm_laser_pm_ops = {
.suspend = pwm_laser_suspend,
.resume = pwm_laser_resume,
};
static const struct of_device_id of_pwm_laser_match[] = {
{.compatible = "pwm-laser", },
{},
};
static struct platform_driver pwm_laser = {
.probe = pwm_laser_probe,
.remove = pwm_laser_remove,
.driver = {
.name = "pwm-laser",
.owner = THIS_MODULE,
.pm = &pwm_laser_pm_ops,
.of_match_table = of_match_ptr(of_pwm_laser_match),
},
};
module_platform_driver(pwm_laser);
MODULE_DESCRIPTION("pwm control driver");
MODULE_LICENSE("GPL");
MODULE_AUTHOR("AaronLee");
3、编写用户测试 demo,测试需求中的所有接口
#include <stdio.h>
#include <stdlib.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <unistd.h>
#include <fcntl.h>
#define PWM_LASER_SET_PERIOD _IOW('A', 0x11, unsigned int)
#define PWM_LASER_GET_PERIOD _IOR('A', 0x12, unsigned int)
#define PWM_LASER_SET_DUTY _IOW('A', 0x13, unsigned int)
#define PWM_LASER_GET_DUTY _IOR('A', 0x14, unsigned int)
#define PWM_LASER_ENABLE _IO('A', 0x15)
#define PWM_LASER_DISABLE _IO('A', 0x16)
int main(void)
{
unsigned int i = 0;
int dir = 0;
int duty, period;
int fd;
fd = open("/dev/pwm-laser", O_RDWR);
if (fd < 0)
{
perror("open pwm-laser fail");
exit(1);
}
/* 获取pwm周期 */
ioctl(fd, PWM_LASER_GET_PERIOD, &period);
printf("pwm: period = %d\n", period);
/* 设置pwm周期为2ms */
period = 2;
ioctl(fd, PWM_LASER_SET_PERIOD, &period);
/* 获取pwm占空比 */
ioctl(fd, PWM_LASER_GET_DUTY, &duty);
printf("pwm: duty = %d\n", duty);
/* 使能pwm */
ioctl(fd, PWM_LASER_ENABLE);
while(1)
{
/* 设置pwm占空比 */
ioctl(fd, PWM_LASER_SET_DUTY, &i);
if (dir == 0) {
i++;
if (i == 100)
dir = 1;
} else {
i--;
if (i == 0)
dir = 0;
}
sleep(1);
}
/* 关闭pwm */
ioctl(fd, PWM_LASER_DISABLE);
close(fd);
return 0;
}
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