[mirror_ubuntu-bionic-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.
 * @interval_cycles:	Used internally by timekeeping core, please ignore.
 * @interval_snsecs:	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 interval_cycles;
	u64 interval_snsecs;
};


/**
 * 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;
}

/**
 * read_clocksource: - 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 read_clocksource(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;
}

/**
 * calculate_clocksource_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 calculate_clocksource_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->interval_cycles = (cycle_t)tmp;
	if(c->interval_cycles == 0)
		c->interval_cycles = 1;

	c->interval_snsecs = (u64)c->interval_cycles * c->mult;
}

/* used to install a new clocksource */
int register_clocksource(struct clocksource*);
void reselect_clocksource(void);
struct clocksource* get_next_clocksource(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.
	49	* @interval_cycles: Used internally by timekeeping core, please ignore.
	50	* @interval_snsecs: Used internally by timekeeping core, please ignore.
	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 */
	64	cycle_t interval_cycles;
65	u64 interval_snsecs;
66	};
67
68
69	/**
70	* clocksource_khz2mult - calculates mult from khz and shift
71	* @khz: Clocksource frequency in KHz
72	* @shift_constant: Clocksource shift factor
73	*
74	* Helper functions that converts a khz counter frequency to a timsource
75	* multiplier, given the clocksource shift value
76	*/
77	static inline u32 clocksource_khz2mult(u32 khz, u32 shift_constant)
78	{
79	/* khz = cyc/(Million ns)
80	* mult/2^shift = ns/cyc
81	* mult = ns/cyc * 2^shift
82	* mult = 1Million/khz * 2^shift
83	* mult = 1000000 * 2^shift / khz
84	* mult = (1000000<<shift) / khz
85	*/
86	u64 tmp = ((u64)1000000) << shift_constant;
87
88	tmp += khz/2; /* round for do_div */
89	do_div(tmp, khz);
90
91	return (u32)tmp;
92	}
93
94	/**
95	* clocksource_hz2mult - calculates mult from hz and shift
96	* @hz: Clocksource frequency in Hz
97	* @shift_constant: Clocksource shift factor
98	*
99	* Helper functions that converts a hz counter
100	* frequency to a timsource multiplier, given the
101	* clocksource shift value
102	*/
103	static inline u32 clocksource_hz2mult(u32 hz, u32 shift_constant)
104	{
105	/* hz = cyc/(Billion ns)
106	* mult/2^shift = ns/cyc
107	* mult = ns/cyc * 2^shift
108	* mult = 1Billion/hz * 2^shift
109	* mult = 1000000000 * 2^shift / hz
110	* mult = (1000000000<<shift) / hz
111	*/
112	u64 tmp = ((u64)1000000000) << shift_constant;
113
114	tmp += hz/2; /* round for do_div */
115	do_div(tmp, hz);
116
117	return (u32)tmp;
118	}
119
120	/**
121	* read_clocksource: - Access the clocksource's current cycle value
122	* @cs: pointer to clocksource being read
123	*
124	* Uses the clocksource to return the current cycle_t value
125	*/
126	static inline cycle_t read_clocksource(struct clocksource *cs)
127	{
128	return cs->read();
129	}
130
131	/**
132	* cyc2ns - converts clocksource cycles to nanoseconds
133	* @cs: Pointer to clocksource
134	* @cycles: Cycles
135	*
136	* Uses the clocksource and ntp ajdustment to convert cycle_ts to nanoseconds.
137	*
138	* XXX - This could use some mult_lxl_ll() asm optimization
139	*/
140	static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
141	{
142	u64 ret = (u64)cycles;
143	ret = (ret * cs->mult) >> cs->shift;
144	return ret;
145	}
146
147	/**
148	* calculate_clocksource_interval - Calculates a clocksource interval struct
149	*
150	* @c: Pointer to clocksource.
151	* @length_nsec: Desired interval length in nanoseconds.
152	*
153	* Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
154	* pair and interval request.
155	*
156	* Unless you're the timekeeping code, you should not be using this!
157	*/
158	static inline void calculate_clocksource_interval(struct clocksource *c,
159	unsigned long length_nsec)
160	{
161	u64 tmp;
162
163	/* XXX - All of this could use a whole lot of optimization */
164	tmp = length_nsec;
165	tmp <<= c->shift;
166	tmp += c->mult/2;
167	do_div(tmp, c->mult);
168
169	c->interval_cycles = (cycle_t)tmp;
170	if(c->interval_cycles == 0)
171	c->interval_cycles = 1;
172
173	c->interval_snsecs = (u64)c->interval_cycles * c->mult;
174	}
175
176	/* used to install a new clocksource */
177	int register_clocksource(struct clocksource*);
178	void reselect_clocksource(void);
179	struct clocksource* get_next_clocksource(void);
180
181	#endif /* _LINUX_CLOCKSOURCE_H */