1、使用示例：

#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
#include <linux/timer.h>
#include <linux/miscdevice.h>
#include <linux/watchdog.h>
#include <linux/fs.h>
#include <linux/notifier.h>
#include <linux/reboot.h>
#include <linux/init.h>
#include <asm/uaccess.h>
#include <asm/io.h>
//#include <asm/arch/hardware.h>
#include <linux/kthread.h>
//#include <asm/arch/clock.h>
#include <linux/string.h>
#include <linux/sched.h>

#define OSDRV_MODULE_VERSION_STRING "HISI_WDT-MDC030001 @Hi3518v100"

#define HISILICON_SCTL_BASE 0x20050000
/* define watchdog IO */
#define HIWDT_BASE      0x20040000
#define HIWDT_REG(x)    (HIWDT_BASE + (x))

#define HIWDT_LOAD      0x000
#define HIWDT_VALUE     0x004
#define HIWDT_CTRL      0x008
#define HIWDT_INTCLR    0x00C
#define HIWDT_RIS       0x010
#define HIWDT_MIS       0x014
#define HIWDT_LOCK      0xC00

#define HIWDT_UNLOCK_VAL    0x1ACCE551

void __iomem *reg_ctl_base_va;
void __iomem *reg_wdt_base_va;
#define IO_WDT_ADDRESS(x) (reg_wdt_base_va + ((x)-(HIWDT_BASE)))

#define hiwdt_readl(x)      readl(IO_WDT_ADDRESS(HIWDT_REG(x)))
#define hiwdt_writel(v,x)   writel(v, IO_WDT_ADDRESS(HIWDT_REG(x)))

/* debug */
#define HIDOG_PFX "HiDog: "
#define hidog_dbg(params...) printk(KERN_INFO HIDOG_PFX params)

/* module param */
#define HIDOG_TIMER_MARGIN    60
static int default_margin = HIDOG_TIMER_MARGIN;    /* in seconds */
#define HIDOG_TIMER_DEMULTIPLY  9
module_param(default_margin, int, 0);
MODULE_PARM_DESC(default_margin, "Watchdog default_margin in seconds. (0<default_margin<80, default=" __MODULE_STRING(HIDOG_TIMER_MARGIN) ")");

static int nowayout = WATCHDOG_NOWAYOUT;
module_param(nowayout, int, 0);
MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=CONFIG_WATCHDOG_NOWAYOUT)");

static int nodeamon = 0;
module_param(nodeamon, int, 0);
MODULE_PARM_DESC(nodeamon, "By default, a kernel deamon feed watchdog when idle, set 'nodeamon=1' to disable this. (default=0)");

/* watchdog info */
static struct watchdog_info ident = {
    .options =  WDIOF_SETTIMEOUT |
                WDIOF_KEEPALIVEPING |
                WDIOF_MAGICCLOSE,
    .firmware_version = 0,
    .identity = "Hisilicon Watchdog",
};

/* local var */
static DEFINE_SPINLOCK(hidog_lock);
static int cur_margin = HIDOG_TIMER_MARGIN;
//static pid_t pid_hidog_deamon = -1;
struct task_struct *task_hidog_deamon = NULL;


#define HIDOG_EXIT    0
#define HIDOG_SELFCLR    1
#define HIDOG_EXTCLR    2
volatile static unsigned int hidog_state = 0;

static unsigned long driver_open = 0, orphan_timer = 0;
static int options = WDIOS_ENABLECARD;

#ifndef MHZ
#define MHZ (1000*1000)
#endif

static unsigned long rate = 3*MHZ;

static inline void hidog_set_timeout(unsigned int nr)
{
    unsigned long cnt = (~0x0)/rate;        /* max cnt */
    unsigned long flags; 

    spin_lock_irqsave(&hidog_lock, flags); 

    if( nr==0 || nr>cnt)
        cnt=~0x0; 
    else
        cnt = nr*rate;
    /* unlock watchdog registers */ 
    hiwdt_writel(HIWDT_UNLOCK_VAL, HIWDT_LOCK); 
    hiwdt_writel(cnt, HIWDT_LOAD); 
    hiwdt_writel(cnt, HIWDT_VALUE); 
    /* lock watchdog registers */ 
    hiwdt_writel(0, HIWDT_LOCK); 
    spin_unlock_irqrestore(&hidog_lock, flags); 
};

static inline void hidog_feed(void)
{
    unsigned long flags; 

    spin_lock_irqsave(&hidog_lock, flags); 
    /* unlock watchdog registers */ 
    hiwdt_writel(HIWDT_UNLOCK_VAL, HIWDT_LOCK); 
    /* clear watchdog */ 
    hiwdt_writel(0x00, HIWDT_INTCLR); 
    /* lock watchdog registers */ 
    hiwdt_writel(0, HIWDT_LOCK); 
    spin_unlock_irqrestore(&hidog_lock, flags); 
};

static int hidog_set_heartbeat(int t)
{
    int ret = 0;
    unsigned int cnt = (~0x0)/rate; 

    if( t==0 ) {
        printk(KERN_ERR HIDOG_PFX "set heartbeat to 0, heartbeat will not be changed.\n");
        t = cur_margin;
        ret = 1;
    } else if( t>cnt ) {
        printk(KERN_ERR HIDOG_PFX "set heartbeat range error, t = %d\n", t);
        printk(KERN_ERR HIDOG_PFX "force heartbeat to %d\n", cnt);
        t = cnt;
        ret = -1;
    }

    cur_margin = t;

    hidog_set_timeout(t);
    hidog_feed();

    if(NULL != task_hidog_deamon)
        wake_up_process(task_hidog_deamon);    

    return ret;
}

static int hidog_keepalive(void)
{
    hidog_feed();
    return 0;
} 
 

自旋鎖詳解：

自旋鎖與互斥鎖有點類似，只是自旋鎖不會引起呼叫者睡眠，如果自旋鎖已經被別的執行單元保持，呼叫者就一直迴圈在那裡看是否該自旋鎖的保持者已經釋放了鎖，"自旋"一詞就是因此而得名。