timer event

/* linux/kernel/time/jiffies.c*/
static cycle_t jiffies_read(struct clocksource *cs)
{
    return (cycle_t) jiffies;
}

struct clocksource clocksource_jiffies = {
    .name        = "jiffies",
    .rating        = 1, /* lowest valid rating*/
    .read        = jiffies_read,
    .mask        = 0xffffffff, /*32bits*/
    .mult        = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */
    .mult_orig    = NSEC_PER_JIFFY << JIFFIES_SHIFT,
    .shift        = JIFFIES_SHIFT,
};

static int __init init_jiffies_clocksource(void)
{
    return clocksource_register(&clocksource_jiffies);
}

core_initcall(init_jiffies_clocksource);


int clocksource_register(struct clocksource *c)
    -->ret = clocksource_enqueue(c);
    /*静态全局变量存储下一个精度最高的时钟源
    static struct clocksource *next_clocksource;*/
    -->next_clocksource = select_clocksource();

struct clocksource *clocksource_get_next(void)
    /*静态全局变量存储当前使用的时钟源
    static struct clocksource *curr_clocksource = &clocksource_jiffies;*/
    -->curr_clocksource = next_clocksource;

/*什么时间更换时钟源，以下两种方法选择其一*/
/*1.jiffies时间中断处理函数*/
static irqreturn_t s3c2410_timer_interrupt(int irq, void *dev_id)
    -->void timer_tick(void)
        -->void do_timer(unsigned long ticks)
            -->jiffies_64 += ticks;
            -->update_times(ticks);
                -->void update_wall_time(void)
                    /* check to see if there is a new clocksource to use */
                    -->change_clocksource();
/*2.jiffies时间中断处理函数*/
void clockevents_register_device(struct clock_event_device *dev)
    /*内核通知链触发*/
    -->clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);

/*通知链注册*/
void __init tick_init(void)
    /*static struct notifier_block tick_notifier = {
    .notifier_call = tick_notify,
    };*/
    -->clockevents_register_notifier(&tick_notifier);
/*通知链回调*/    
static int tick_notify(struct notifier_block *nb, unsigned long reason,void *dev)
    -->static int tick_check_new_device(struct clock_event_device *newdev)
        -->static void tick_setup_device(struct tick_device *td,struct clock_event_device *newdev, int cpu,const struct cpumask *cpumask)
            -->void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
                -->void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
                    -->dev->event_handler = tick_handle_periodic;
/*event时间处理函数调用*/
void tick_handle_periodic(struct clock_event_device *dev)
    -->static void tick_periodic(int cpu)
        -->void do_timer(unsigned long ticks)
            -->jiffies_64 += ticks;
            -->update_times(ticks);
                -->void update_wall_time(void)
                    /* check to see if there is a new clocksource to use */
                    -->change_clocksource();

/* linux/kernel/time/jiffies.c*/static cycle_t jiffies_read(struct clocksource *cs){return (cycle_t) jiffies;}
struct clocksource clocksource_jiffies = {.name= "jiffies",.rating= 1, /* lowest valid rating*/.read= jiffies_read,.mask= 0xffffffff, /*32bits*/.mult= NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */.mult_orig= NSEC_PER_JIFFY << JIFFIES_SHIFT,.shift= JIFFIES_SHIFT,};
static int __init init_jiffies_clocksource(void){return clocksource_register(&clocksource_jiffies);}
core_initcall(init_jiffies_clocksource);

int clocksource_register(struct clocksource *c)-->ret = clocksource_enqueue(c);/*静态全局变量存储下一个精度最高的时钟源static struct clocksource *next_clocksource;*/-->next_clocksource = select_clocksource();
struct clocksource *clocksource_get_next(void)/*静态全局变量存储当前使用的时钟源static struct clocksource *curr_clocksource = &clocksource_jiffies;*/-->curr_clocksource = next_clocksource;
/*什么时间更换时钟源，以下两种方法选择其一*//*1.jiffies时间中断处理函数*/static irqreturn_t s3c2410_timer_interrupt(int irq, void *dev_id)-->void timer_tick(void)-->void do_timer(unsigned long ticks)-->jiffies_64 += ticks;-->update_times(ticks);-->void update_wall_time(void)/* check to see if there is a new clocksource to use */-->change_clocksource();/*2.jiffies时间中断处理函数*/void clockevents_register_device(struct clock_event_device *dev)/*内核通知链触发*/-->clockevents_do_notify(CLOCK_EVT_NOTIFY_ADD, dev);
/*通知链注册*/void __init tick_init(void)/*static struct notifier_block tick_notifier = {.notifier_call = tick_notify,};*/-->clockevents_register_notifier(&tick_notifier);/*通知链回调*/static int tick_notify(struct notifier_block *nb, unsigned long reason,void *dev)-->static int tick_check_new_device(struct clock_event_device *newdev)-->static void tick_setup_device(struct tick_device *td,struct clock_event_device *newdev, int cpu,const struct cpumask *cpumask)-->void tick_setup_periodic(struct clock_event_device *dev, int broadcast)-->void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)-->dev->event_handler = tick_handle_periodic;/*event时间处理函数调用*/void tick_handle_periodic(struct clock_event_device *dev)-->static void tick_periodic(int cpu)-->void do_timer(unsigned long ticks)-->jiffies_64 += ticks;-->update_times(ticks);-->void update_wall_time(void)/* check to see if there is a new clocksource to use */-->change_clocksource();