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_FREQ		1
#define PWM_IOCTL_STOP			0

static 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;
	else
		return -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");