[mirror_ubuntu-zesty-kernel.git] / include / linux / clocksource.h

/*  linux/include/linux/clocksource.h
 *
 *  This file contains the structure definitions for clocksources.
 *
 *  If you are not a clocksource, or timekeeping code, you should
 *  not be including this file!
 */
#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 <asm/div64.h>
#include <asm/io.h>

/* clocksource cycle base type */
typedef u64 cycle_t;

/**
 * struct clocksource - hardware abstraction for a free running counter
 *	Provides mostly state-free accessors to the underlying hardware.
 *
 * @name:		ptr to clocksource name
 * @list:		list head for registration
 * @rating:		rating value for selection (higher is better)
 *			To avoid rating inflation the following
 *			list should give you a guide as to how
 *			to assign your clocksource a rating
 *			1-99: Unfit for real use
 *				Only available for bootup and testing purposes.
 *			100-199: Base level usability.
 *				Functional for real use, but not desired.
 *			200-299: Good.
 *				A correct and usable clocksource.
 *			300-399: Desired.
 *				A reasonably fast and accurate clocksource.
 *			400-499: Perfect
 *				The ideal clocksource. A must-use where
 *				available.
 * @read:		returns a cycle value
 * @mask:		bitmask for two's complement
 *			subtraction of non 64 bit counters
 * @mult:		cycle to nanosecond multiplier
 * @shift:		cycle to nanosecond divisor (power of two)
 * @update_callback:	called when safe to alter clocksource values
 * @is_continuous:	defines if clocksource is free-running.
 * @cycle_interval:	Used internally by timekeeping core, please ignore.
 * @xtime_interval:	Used internally by timekeeping core, please ignore.
 */
struct clocksource {
	char *name;
	struct list_head list;
	int rating;
	cycle_t (*read)(void);
	cycle_t mask;
	u32 mult;
	u32 shift;
	int (*update_callback)(void);
	int is_continuous;

	/* timekeeping specific data, ignore */
	cycle_t cycle_last, cycle_interval;
	u64 xtime_nsec, xtime_interval;
	s64 error;
};

/* simplify initialization of mask field */
#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)

/**
 * clocksource_khz2mult - calculates mult from khz and shift
 * @khz:		Clocksource frequency in KHz
 * @shift_constant:	Clocksource shift factor
 *
 * Helper functions that converts a khz counter frequency to a timsource
 * multiplier, given the clocksource shift value
 */
static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
{
	/*  khz = cyc/(Million ns)
	 *  mult/2^shift  = ns/cyc
	 *  mult = ns/cyc * 2^shift
	 *  mult = 1Million/khz * 2^shift
	 *  mult = 1000000 * 2^shift / khz
	 *  mult = (1000000<<shift) / khz
	 */
	u64 tmp = ((u64)1000000) << shift_constant;

	tmp += khz/2; /* round for do_div */
	do_div(tmp, khz);

	return (u32)tmp;
}

/**
 * clocksource_hz2mult - calculates mult from hz and shift
 * @hz:			Clocksource frequency in Hz
 * @shift_constant:	Clocksource shift factor
 *
 * Helper functions that converts a hz counter
 * frequency to a timsource multiplier, given the
 * clocksource shift value
 */
static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
{
	/*  hz = cyc/(Billion ns)
	 *  mult/2^shift  = ns/cyc
	 *  mult = ns/cyc * 2^shift
	 *  mult = 1Billion/hz * 2^shift
	 *  mult = 1000000000 * 2^shift / hz
	 *  mult = (1000000000<<shift) / hz
	 */
	u64 tmp = ((u64)1000000000) << shift_constant;

	tmp += hz/2; /* round for do_div */
	do_div(tmp, hz);

	return (u32)tmp;
}

/**
 * clocksource_read: - Access the clocksource's current cycle value
 * @cs:		pointer to clocksource being read
 *
 * Uses the clocksource to return the current cycle_t value
 */
static inline cycle_t clocksource_read(struct clocksource *cs)
{
	return cs->read();
}

/**
 * cyc2ns - converts clocksource cycles to nanoseconds
 * @cs:		Pointer to clocksource
 * @cycles:	Cycles
 *
 * Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
 *
 * XXX - This could use some mult_lxl_ll() asm optimization
 */
static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
{
	u64 ret = (u64)cycles;
	ret = (ret * cs->mult) >> cs->shift;
	return ret;
}

/**
 * clocksource_calculate_interval - Calculates a clocksource interval struct
 *
 * @c:		Pointer to clocksource.
 * @length_nsec: Desired interval length in nanoseconds.
 *
 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
 * pair and interval request.
 *
 * Unless you're the timekeeping code, you should not be using this!
 */
static inline void clocksource_calculate_interval(struct clocksource *c,
						unsigned long length_nsec)
{
	u64 tmp;

	/* XXX - All of this could use a whole lot of optimization */
	tmp = length_nsec;
	tmp <<= c->shift;
	tmp += c->mult/2;
	do_div(tmp, c->mult);

	c->cycle_interval = (cycle_t)tmp;
	if (c->cycle_interval == 0)
		c->cycle_interval = 1;

	c->xtime_interval = (u64)c->cycle_interval * c->mult;
}


/* used to install a new clocksource */
int clocksource_register(struct clocksource*);
void clocksource_reselect(void);
struct clocksource* clocksource_get_next(void);

#endif /* _LINUX_CLOCKSOURCE_H */
Commit	Line	Data
734efb46 JS	1	/* linux/include/linux/clocksource.h
	2	*
	3	* This file contains the structure definitions for clocksources.
	4	*
	5	* If you are not a clocksource, or timekeeping code, you should
	6	* not be including this file!
	7	*/
	8	#ifndef _LINUX_CLOCKSOURCE_H
	9	#define _LINUX_CLOCKSOURCE_H
	10
	11	#include <linux/types.h>
	12	#include <linux/timex.h>
	13	#include <linux/time.h>
	14	#include <linux/list.h>
	15	#include <asm/div64.h>
	16	#include <asm/io.h>
	17
	18	/* clocksource cycle base type */
	19	typedef u64 cycle_t;
	20
	21	/**
	22	* struct clocksource - hardware abstraction for a free running counter
	23	* Provides mostly state-free accessors to the underlying hardware.
	24	*
	25	* @name: ptr to clocksource name
	26	* @list: list head for registration
	27	* @rating: rating value for selection (higher is better)
	28	* To avoid rating inflation the following
	29	* list should give you a guide as to how
	30	* to assign your clocksource a rating
	31	* 1-99: Unfit for real use
	32	* Only available for bootup and testing purposes.
	33	* 100-199: Base level usability.
	34	* Functional for real use, but not desired.
	35	* 200-299: Good.
	36	* A correct and usable clocksource.
	37	* 300-399: Desired.
	38	* A reasonably fast and accurate clocksource.
	39	* 400-499: Perfect
	40	* The ideal clocksource. A must-use where
	41	* available.
	42	* @read: returns a cycle value
	43	* @mask: bitmask for two's complement
	44	* subtraction of non 64 bit counters
	45	* @mult: cycle to nanosecond multiplier
	46	* @shift: cycle to nanosecond divisor (power of two)
	47	* @update_callback: called when safe to alter clocksource values
	48	* @is_continuous: defines if clocksource is free-running.
19923c19 RZ	49	* @cycle_interval: Used internally by timekeeping core, please ignore.
19923c19 RZ	50	* @xtime_interval: Used internally by timekeeping core, please ignore.
734efb46 JS	51	*/
	52	struct clocksource {
	53	char *name;
	54	struct list_head list;
	55	int rating;
	56	cycle_t (*read)(void);
	57	cycle_t mask;
	58	u32 mult;
	59	u32 shift;
	60	int (*update_callback)(void);
	61	int is_continuous;
	62
	63	/* timekeeping specific data, ignore */
19923c19 RZ	64	cycle_t cycle_last, cycle_interval;
	65	u64 xtime_nsec, xtime_interval;
	66	s64 error;
734efb46 JS	67	};
734efb46 JS	68
7f9f303a JC	69	/* simplify initialization of mask field */
7f9f303a JC	70	#define CLOCKSOURCE_MASK(bits) (cycle_t)(bits<64 ? ((1ULL<<bits)-1) : -1)
734efb46 JS	71
	72	/**
	73	* clocksource_khz2mult - calculates mult from khz and shift
	74	* @khz: Clocksource frequency in KHz
	75	* @shift_constant: Clocksource shift factor
	76	*
	77	* Helper functions that converts a khz counter frequency to a timsource
	78	* multiplier, given the clocksource shift value
	79	*/
	80	static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
	81	{
	82	/* khz = cyc/(Million ns)
	83	* mult/2^shift = ns/cyc
	84	* mult = ns/cyc * 2^shift
	85	* mult = 1Million/khz * 2^shift
	86	* mult = 1000000 * 2^shift / khz
	87	* mult = (1000000<<shift) / khz
	88	*/
	89	u64 tmp = ((u64)1000000) << shift_constant;
	90
	91	tmp += khz/2; /* round for do_div */
	92	do_div(tmp, khz);
	93
	94	return (u32)tmp;
	95	}
	96
	97	/**
	98	* clocksource_hz2mult - calculates mult from hz and shift
	99	* @hz: Clocksource frequency in Hz
	100	* @shift_constant: Clocksource shift factor
	101	*
	102	* Helper functions that converts a hz counter
	103	* frequency to a timsource multiplier, given the
	104	* clocksource shift value
	105	*/
	106	static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
	107	{
	108	/* hz = cyc/(Billion ns)
	109	* mult/2^shift = ns/cyc
	110	* mult = ns/cyc * 2^shift
	111	* mult = 1Billion/hz * 2^shift
	112	* mult = 1000000000 * 2^shift / hz
	113	* mult = (1000000000<<shift) / hz
	114	*/
	115	u64 tmp = ((u64)1000000000) << shift_constant;
	116
	117	tmp += hz/2; /* round for do_div */
	118	do_div(tmp, hz);
	119
	120	return (u32)tmp;
	121	}
	122
	123	/**
a2752549	124	* clocksource_read: - Access the clocksource's current cycle value
734efb46 JS	125	* @cs: pointer to clocksource being read
	126	*
	127	* Uses the clocksource to return the current cycle_t value
	128	*/
a2752549	129	static inline cycle_t clocksource_read(struct clocksource *cs)
734efb46 JS	130	{
	131	return cs->read();
	132	}
	133
	134	/**
	135	* cyc2ns - converts clocksource cycles to nanoseconds
	136	* @cs: Pointer to clocksource
	137	* @cycles: Cycles
	138	*
	139	* Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
	140	*
	141	* XXX - This could use some mult_lxl_ll() asm optimization
	142	*/
	143	static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
	144	{
	145	u64 ret = (u64)cycles;
	146	ret = (ret * cs->mult) >> cs->shift;
	147	return ret;
	148	}
	149
	150	/**
a2752549	151	* clocksource_calculate_interval - Calculates a clocksource interval struct
734efb46 JS	152	*
	153	* @c: Pointer to clocksource.
	154	* @length_nsec: Desired interval length in nanoseconds.
	155	*
	156	* Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
	157	* pair and interval request.
	158	*
	159	* Unless you're the timekeeping code, you should not be using this!
	160	*/
a2752549	161	static inline void clocksource_calculate_interval(struct clocksource *c,
734efb46 JS	162	unsigned long length_nsec)
	163	{
	164	u64 tmp;
	165
	166	/* XXX - All of this could use a whole lot of optimization */
	167	tmp = length_nsec;
	168	tmp <<= c->shift;
	169	tmp += c->mult/2;
	170	do_div(tmp, c->mult);
	171
19923c19 RZ	172	c->cycle_interval = (cycle_t)tmp;
	173	if (c->cycle_interval == 0)
	174	c->cycle_interval = 1;
734efb46	175
19923c19	176	c->xtime_interval = (u64)c->cycle_interval * c->mult;
5eb6d205 JS	177	}
	178
	179
734efb46	180	/* used to install a new clocksource */
a2752549 JS	181	int clocksource_register(struct clocksource*);
	182	void clocksource_reselect(void);
	183	struct clocksource* clocksource_get_next(void);
734efb46 JS	184
734efb46 JS	185	#endif /* _LINUX_CLOCKSOURCE_H */