include/linux/clocksource.h

#ifndef _LINUX_CLOCKSOURCE_H
#define _LINUX_CLOCKSOURCE_H

#include <linux/types.h>
#include <linux/timex.h>
#include <linux/time.h>
#include <linux/list.h>
#include <linux/cache.h>
#include <linux/timer.h>
#include <linux/init.h>
#include <asm/div64.h>
#include <asm/io.h>

typedef u64 cycle_t;
struct clocksource;

#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
#include <asm/clocksource.h>
#endif

struct cyclecounter {
	cycle_t (*read)(const struct cyclecounter *cc);
	cycle_t mask;
	u32 mult;
	u32 shift;
};

struct timecounter {
	const struct cyclecounter *cc;
	cycle_t cycle_last;
	u64 nsec;
};

static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc,
				      cycle_t cycles)
{
	u64 ret = (u64)cycles;
	ret = (ret * cc->mult) >> cc->shift;
	return ret;
}

extern void timecounter_init(struct timecounter *tc,
			     const struct cyclecounter *cc,
			     u64 start_tstamp);

extern u64 timecounter_read(struct timecounter *tc);

extern u64 timecounter_cyc2time(struct timecounter *tc,
				cycle_t cycle_tstamp);

struct clocksource {
	cycle_t (*read)(struct clocksource *cs);
	cycle_t cycle_last;
	cycle_t mask;
	u32 mult;
	u32 shift;
	u64 max_idle_ns;
	u32 maxadj;
#ifdef CONFIG_ARCH_CLOCKSOURCE_DATA
	struct arch_clocksource_data archdata;
#endif

	const char *name;
	struct list_head list;
	int rating;
	int (*enable)(struct clocksource *cs);
	void (*disable)(struct clocksource *cs);
	unsigned long flags;
	void (*suspend)(struct clocksource *cs);
	void (*resume)(struct clocksource *cs);

	
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
	
	struct list_head wd_list;
	cycle_t cs_last;
	cycle_t wd_last;
#endif
} ____cacheline_aligned;

#define CLOCK_SOURCE_IS_CONTINUOUS		0x01
#define CLOCK_SOURCE_MUST_VERIFY		0x02

#define CLOCK_SOURCE_WATCHDOG			0x10
#define CLOCK_SOURCE_VALID_FOR_HRES		0x20
#define CLOCK_SOURCE_UNSTABLE			0x40

#define CLOCKSOURCE_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)

static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
{
	u64 tmp = ((u64)1000000) << shift_constant;

	tmp += khz/2; 
	do_div(tmp, khz);

	return (u32)tmp;
}

static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
{
	u64 tmp = ((u64)1000000000) << shift_constant;

	tmp += hz/2; 
	do_div(tmp, hz);

	return (u32)tmp;
}

static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift)
{
	return ((u64) cycles * mult) >> shift;
}


extern int clocksource_register(struct clocksource*);
extern void clocksource_unregister(struct clocksource*);
extern void clocksource_touch_watchdog(void);
extern struct clocksource* clocksource_get_next(void);
extern void clocksource_change_rating(struct clocksource *cs, int rating);
extern void clocksource_suspend(void);
extern void clocksource_resume(void);
extern struct clocksource * __init __weak clocksource_default_clock(void);
extern void clocksource_mark_unstable(struct clocksource *cs);

extern void
clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec);

extern int
__clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq);
extern void
__clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq);

static inline int clocksource_register_hz(struct clocksource *cs, u32 hz)
{
	return __clocksource_register_scale(cs, 1, hz);
}

static inline int clocksource_register_khz(struct clocksource *cs, u32 khz)
{
	return __clocksource_register_scale(cs, 1000, khz);
}

static inline void __clocksource_updatefreq_hz(struct clocksource *cs, u32 hz)
{
	__clocksource_updatefreq_scale(cs, 1, hz);
}

static inline void __clocksource_updatefreq_khz(struct clocksource *cs, u32 khz)
{
	__clocksource_updatefreq_scale(cs, 1000, khz);
}

#ifdef CONFIG_GENERIC_TIME_VSYSCALL
extern void
update_vsyscall(struct timespec *ts, struct timespec *wtm,
			struct clocksource *c, u32 mult);
extern void update_vsyscall_tz(void);
#else
static inline void
update_vsyscall(struct timespec *ts, struct timespec *wtm,
			struct clocksource *c, u32 mult)
{
}

static inline void update_vsyscall_tz(void)
{
}
#endif

extern void timekeeping_notify(struct clocksource *clock);

extern cycle_t clocksource_mmio_readl_up(struct clocksource *);
extern cycle_t clocksource_mmio_readl_down(struct clocksource *);
extern cycle_t clocksource_mmio_readw_up(struct clocksource *);
extern cycle_t clocksource_mmio_readw_down(struct clocksource *);

extern int clocksource_mmio_init(void __iomem *, const char *,
	unsigned long, int, unsigned, cycle_t (*)(struct clocksource *));

extern int clocksource_i8253_init(void);

#endif