/* 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 #include #include #include #include #include #include #include #include /* clocksource cycle base type */ typedef u64 cycle_t; struct clocksource; /** * struct cyclecounter - hardware abstraction for a free running counter * Provides completely state-free accessors to the underlying hardware. * Depending on which hardware it reads, the cycle counter may wrap * around quickly. Locking rules (if necessary) have to be defined * by the implementor and user of specific instances of this API. * * @read: returns the current cycle value * @mask: bitmask for two's complement * subtraction of non 64 bit counters, * see CLOCKSOURCE_MASK() helper macro * @mult: cycle to nanosecond multiplier * @shift: cycle to nanosecond divisor (power of two) */ struct cyclecounter { cycle_t (*read)(const struct cyclecounter *cc); cycle_t mask; u32 mult; u32 shift; }; /** * struct timecounter - layer above a %struct cyclecounter which counts nanoseconds * Contains the state needed by timecounter_read() to detect * cycle counter wrap around. Initialize with * timecounter_init(). Also used to convert cycle counts into the * corresponding nanosecond counts with timecounter_cyc2time(). Users * of this code are responsible for initializing the underlying * cycle counter hardware, locking issues and reading the time * more often than the cycle counter wraps around. The nanosecond * counter will only wrap around after ~585 years. * * @cc: the cycle counter used by this instance * @cycle_last: most recent cycle counter value seen by * timecounter_read() * @nsec: continuously increasing count */ struct timecounter { const struct cyclecounter *cc; cycle_t cycle_last; u64 nsec; }; /** * cyclecounter_cyc2ns - converts cycle counter cycles to nanoseconds * @tc: Pointer to cycle counter. * @cycles: Cycles * * XXX - This could use some mult_lxl_ll() asm optimization. Same code * as in cyc2ns, but with unsigned result. */ static inline u64 cyclecounter_cyc2ns(const struct cyclecounter *cc, cycle_t cycles) { u64 ret = (u64)cycles; ret = (ret * cc->mult) >> cc->shift; return ret; } /** * timecounter_init - initialize a time counter * @tc: Pointer to time counter which is to be initialized/reset * @cc: A cycle counter, ready to be used. * @start_tstamp: Arbitrary initial time stamp. * * After this call the current cycle register (roughly) corresponds to * the initial time stamp. Every call to timecounter_read() increments * the time stamp counter by the number of elapsed nanoseconds. */ extern void timecounter_init(struct timecounter *tc, const struct cyclecounter *cc, u64 start_tstamp); /** * timecounter_read - return nanoseconds elapsed since timecounter_init() * plus the initial time stamp * @tc: Pointer to time counter. * * In other words, keeps track of time since the same epoch as * the function which generated the initial time stamp. */ extern u64 timecounter_read(struct timecounter *tc); /** * timecounter_cyc2time - convert a cycle counter to same * time base as values returned by * timecounter_read() * @tc: Pointer to time counter. * @cycle: a value returned by tc->cc->read() * * Cycle counts that are converted correctly as long as they * fall into the interval [-1/2 max cycle count, +1/2 max cycle count], * with "max cycle count" == cs->mask+1. * * This allows conversion of cycle counter values which were generated * in the past. */ extern u64 timecounter_cyc2time(struct timecounter *tc, cycle_t cycle_tstamp); /** * struct clocksource - hardware abstraction for a free running counter * Provides mostly state-free accessors to the underlying hardware. * This is the structure used for system time. * * @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, passes clocksource as argument * @enable: optional function to enable the clocksource * @disable: optional function to disable the clocksource * @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) * @max_idle_ns: max idle time permitted by the clocksource (nsecs) * @flags: flags describing special properties * @vread: vsyscall based read * @resume: resume function for the clocksource, if necessary */ struct clocksource { /* * First part of structure is read mostly */ char *name; struct list_head list; int rating; cycle_t (*read)(struct clocksource *cs); int (*enable)(struct clocksource *cs); void (*disable)(struct clocksource *cs); cycle_t mask; u32 mult; u32 shift; u64 max_idle_ns; unsigned long flags; cycle_t (*vread)(void); void (*resume)(void); #ifdef CONFIG_IA64 void *fsys_mmio; /* used by fsyscall asm code */ #define CLKSRC_FSYS_MMIO_SET(mmio, addr) ((mmio) = (addr)) #else #define CLKSRC_FSYS_MMIO_SET(mmio, addr) do { } while (0) #endif /* * Second part is written at each timer interrupt * Keep it in a different cache line to dirty no * more than one cache line. */ cycle_t cycle_last ____cacheline_aligned_in_smp; #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 #define CLOCK_SOURCE_UNSTABLE 0x40 /* 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; } /* used to install a new clocksource */ 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_resume(void); extern struct clocksource * __init __weak clocksource_default_clock(void); extern void clocksource_mark_unstable(struct clocksource *cs); #ifdef CONFIG_GENERIC_TIME_VSYSCALL extern void update_vsyscall(struct timespec *ts, struct clocksource *c); extern void update_vsyscall_tz(void); #else static inline void update_vsyscall(struct timespec *ts, struct clocksource *c) { } static inline void update_vsyscall_tz(void) { } #endif extern void timekeeping_notify(struct clocksource *clock); #endif /* _LINUX_CLOCKSOURCE_H */