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 ", 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" initialized "）; 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"）;