OK6410之蜂鸣器驱动软件分析---PWM定时器

#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 <asm/irq.h>#include <asm/io.h>#include <linux/interrupt.h>#include <asm/uaccess.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>#include <mach/map.h>#include <mach/regs-clock.h>#include <mach/regs-gpio.h>#include <plat/gpio-cfg.h>#include <mach/gpio-bank-e.h>#include <mach/gpio-bank-f.h>#include <mach/gpio-bank-k.h>#define DEVICE_NAME     "pwm"#define PWM_IOCTL_SET_FREQ1#define PWM_IOCTL_STOP0static struct semaphore lock; //信号量/* 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;unsigned tmp;tmp = readl(S3C64XX_GPFCON);  //tmp &= ~(0x3U << 28);//tmp |=  (0x2U << 28);         tmp &=~(0x3U << 30);  //GPF15  [31:30]    10 = PWM TOUT[1]          tmp |=  (0x2U << 30);writel(tmp, S3C64XX_GPFCON);tcon = __raw_readl(S3C_TCON);  //定时器控制寄存器tcfg1 = __raw_readl(S3C_TCFG1); //时钟多路复用器和 DMA模式的选择tcfg0 = __raw_readl(S3C_TCFG0); //时钟预定标器和死区结构//prescaler = 50   Prescaler 0 [7:0] R/W Prescaler 0 value for timer 0 & 1 tcfg0 &= ~S3C_TCFG_PRESCALER0_MASK;  //{prescaler value} = 1~255  tcfg0 |= (50 - 1);  //prescaler value=50//mux = 1/16  TCFG1  Divider MUX0 [3:0] R/W Select Mux input for PWM Timer 0 tcfg1 &= ~S3C_TCFG1_MUX0_MASK;tcfg1 |= S3C_TCFG1_MUX0_DIV16; // 0100: 1/16  __raw_writel(tcfg1, S3C_TCFG1);__raw_writel(tcfg0, S3C_TCFG0);/* clk_get获取一个名为id的时针 * 输入参数dev:   可以为NULL * 输入参数id:    时针名称,如fclk、hclk、pclk等 * 返回值:        返回该时钟的clk结构体 * *再将clk_get返回的clk结构体传递给clk_get_rate，获取该时钟的频率 *//*PCLK is used for APB bus, which is used by the peripherals  *such as WDT, IIS, I2C, PWM timer, MMC */ clk_p = clk_get(NULL, "pclk");  //获取一个名为id的时针pclk  = clk_get_rate(clk_p);  //获取该时钟的频率//定时器输入时钟频率 //Timer input clock Frequency = PCLK / ( {prescaler value + 1} ) / {divider value} tcnt  = (pclk/50/16)/freq;  __raw_writel(tcnt, S3C_TCNTB(0)); //TCNTB0:定时器0计数缓冲器。 __raw_writel(tcnt/2, S3C_TCMPB(0));//TCMPB0:定时器0比较缓冲寄存器。 tcon &= ~0x1f;tcon |= 0xb;//disable deadzone, auto-reload, inv-off, update TCNTB0&TCMPB0, start timer 0__raw_writel(tcon, S3C_TCON);/*Note: Manual update bit must be 1’b0 before Start/Stop bit is 1’b1.    If Manual update bit is 1’b1 and Start/Stop bit is 1’b1,    timer counter is not update by new value.    Timer counter value is last value. */tcon &= ~2;//clear manual update bit__raw_writel(tcon, S3C_TCON);}void PWM_Stop( void ){unsigned tmp;tmp = readl(S3C64XX_GPFCON);//tmp &= ~(0x3U << 28);        tmp &= ~(0x3U << 30);writel(tmp, S3C64XX_GPFCON);}/*　该函数尝试获得信号量sem，如果能够立刻获得，它就获得该信号量并返回0，否则，返回非0值。它不会导致调用者睡眠，可以在中断上下文使用。*/static int s3c64xx_pwm_open(struct inode *inode, struct file *file){if (!down_trylock(&lock))return 0;elsereturn -EBUSY;}static int s3c64xx_pwm_close(struct inode *inode, struct file *file){up(&lock);  //该函数释放信号量sem，唤醒等待者return 0;}static long s3c64xx_pwm_ioctl(struct file *filep, unsigned int cmd, unsigned long arg){switch (cmd) {case PWM_IOCTL_SET_FREQ:if (arg == 0)return -EINVAL;PWM_Set_Freq(arg);break;case PWM_IOCTL_STOP:default:PWM_Stop();break;}return 0;}static struct file_operations dev_fops = {    .owner= THIS_MODULE,    .open= s3c64xx_pwm_open,    .release= s3c64xx_pwm_close,     .unlocked_ioctl= s3c64xx_pwm_ioctl,};static struct miscdevice misc = {.minor = MISC_DYNAMIC_MINOR,.name = DEVICE_NAME,.fops = &dev_fops,};static int __init dev_init(void){int ret;/*　该函数用于初始化一个互斥锁，即它把信号量sem的值设置为1，等同于sema_init (struct semaphore *sem, 1)*/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("FORLINX Inc.");MODULE_DESCRIPTION("S3C6410 PWM Driver");