Mini2440开发板PWM驱动与测试程序简要分析

文章由LinuxBoy分享于2019-03-31 01:03:37热评（459）

Mini2440开发板PWM驱动与测试程序简要分析

先看下电路原理图

#include <linux/module.h>

#include <linux/kernel.h>

#include <linux/fs.h>

#include <linux/init.h>

#include <linux/delay.h>

#include <linux/poll.h>

#include <linux/interrupt.h>

#include <linux/gpio.h>

#include <asm/irq.h>

#include <asm/io.h>

#include <asm/uaccess.h>

#include <mach/regs-gpio.h>

#include <mach/hardware.h>

#include <plat/regs-timer.h>

#include <mach/regs-irq.h>

#include <asm/mach/time.h>

#include <linux/clk.h>

#include <linux/cdev.h>

#include <linux/device.h>

#include <linux/miscdevice.h>

#define DEVICE_NAME "pwm"

#define PWM_IOCTL_SET_FREQ 1 //设置pwm的频率

#define PWM_IOCTL_STOP 0 //停止pwm

static struct semaphore lock;

//定义信号量，此处的信号量是一个互斥信号量，用于PWM设备之多只能被一个进程打开

/* freq: pclk/50/16/65536 ~ pclk/50/16

* if pclk = 50MHz, freq is 1Hz to 62500Hz

* human ear : 20Hz~ 20000Hz

static void PWM_Set_Freq( unsigned long freq )

{

unsigned long tcon;

unsigned long tcnt;

unsigned long tcfg1;

unsigned long tcfg0;

struct clk *clk_p;

unsigned long pclk;

//set GPB0 as tout0, pwm output

s3c2410_gpio_cfgpin(S3C2410_GPB(0), S3C2410_GPB0_TOUT0);//功能配置

tcon = __raw_readl(S3C2410_TCON); //获得定时器控制寄存器的数值

tcfg1 = __raw_readl(S3C2410_TCFG1); //获得定时器配置寄存器0的值

tcfg0 = __raw_readl(S3C2410_TCFG0); //获得定时器配置寄存器1的值

//prescaler = 50

tcfg0 &= ~S3C2410_TCFG_PRESCALER0_MASK;

tcfg0 |= (50 - 1);

//mux = 1/16

tcfg1 &= ~S3C2410_TCFG1_MUX0_MASK;

tcfg1 |= S3C2410_TCFG1_MUX0_DIV16;

__raw_writel(tcfg1, S3C2410_TCFG1);

__raw_writel(tcfg0, S3C2410_TCFG0);

clk_p = clk_get(NULL, "pclk");

pclk = clk_get_rate(clk_p);

tcnt = (pclk/50/16)/freq;

__raw_writel(tcnt, S3C2410_TCNTB(0));

__raw_writel(tcnt/2, S3C2410_TCMPB(0));

tcon &= ~0x1f;

tcon |= 0xb; //disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 0

__raw_writel(tcon, S3C2410_TCON);

tcon &= ~2; //clear manual update bit

__raw_writel(tcon, S3C2410_TCON);

}

static void PWM_Stop(void)

{

s3c2410_gpio_cfgpin(S3C2410_GPB(0), S3C2410_GPIO_OUTPUT);

s3c2410_gpio_setpin(S3C2410_GPB(0), 0);

}

static int s3c24xx_pwm_open(struct inode *inode, struct file *file)

{

if (!down_trylock(&lock))//判断是否设备已经打开，已打开返回EBUSY

return 0;

else

return -EBUSY;

}

static int s3c24xx_pwm_close(struct inode *inode, struct file *file)

{

PWM_Stop();//停止PWM

up(&lock);//释放信号量

return 0;

}

static int s3c24xx_pwm_ioctl(struct inode *inode, struct file *file, unsigned int cmd, unsigned long arg)

{

//printk("ioctl pwm: %x %lx\n", cmd, arg);

switch (cmd) {

case PWM_IOCTL_SET_FREQ:

if (arg == 0)

return -EINVAL;

PWM_Set_Freq(arg);

break;

case PWM_IOCTL_STOP:

PWM_Stop();

break;

}

return 0;

}

static struct file_operations dev_fops = {

.owner = THIS_MODULE,

.open = s3c24xx_pwm_open,

.release = s3c24xx_pwm_close,

.ioctl = s3c24xx_pwm_ioctl,

};

static struct miscdevice misc = {

.minor = MISC_DYNAMIC_MINOR,

.name = DEVICE_NAME,

.fops = &dev_fops,

};

static int __init dev_init(void)

{

int ret;

init_MUTEX(&lock);

ret = misc_register(&misc);

printk (DEVICE_NAME"\tinitialized\n");

return ret;

}

static void __exit dev_exit(void)

{

misc_deregister(&misc);

}

module_init(dev_init);

module_exit(dev_exit);

MODULE_LICENSE("GPL");

MODULE_AUTHOR("FriendlyARM Inc.");

MODULE_DESCRIPTION("S3C2410/S3C2440 PWM Driver");

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