/* 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 */