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- /* 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 <linux/timer.h>
- #include <asm/div64.h>
- #include <asm/io.h>
- /* clocksource cycle base type */
- typedef u64 cycle_t;
- struct clocksource;
- /**
- * 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)
- * @flags: flags describing special properties
- * @vread: vsyscall based read
- * @resume: resume function for the clocksource, if necessary
- * @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;
- unsigned long flags;
- cycle_t (*vread)(void);
- void (*resume)(void);
- /* timekeeping specific data, ignore */
- cycle_t cycle_last, cycle_interval;
- u64 xtime_nsec, xtime_interval;
- s64 error;
- #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
- /* Watchdog related data, used by the framework */
- struct list_head wd_list;
- cycle_t wd_last;
- #endif
- };
- /*
- * Clock source flags bits::
- */
- #define CLOCK_SOURCE_IS_CONTINUOUS 0x01
- #define CLOCK_SOURCE_MUST_VERIFY 0x02
- #define CLOCK_SOURCE_WATCHDOG 0x10
- #define CLOCK_SOURCE_VALID_FOR_HRES 0x20
- /* 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 */
- extern int clocksource_register(struct clocksource*);
- extern struct clocksource* clocksource_get_next(void);
- extern void clocksource_change_rating(struct clocksource *cs, int rating);
- extern void clocksource_resume(void);
- #ifdef CONFIG_GENERIC_TIME_VSYSCALL
- extern void update_vsyscall(struct timespec *ts, struct clocksource *c);
- #else
- static inline void update_vsyscall(struct timespec *ts, struct clocksource *c)
- {
- }
- #endif
- #endif /* _LINUX_CLOCKSOURCE_H */
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