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Diffstat (limited to 'include/linux/clocksource.h')
| -rw-r--r-- | include/linux/clocksource.h | 311 |
1 files changed, 311 insertions, 0 deletions
diff --git a/include/linux/clocksource.h b/include/linux/clocksource.h new file mode 100644 index 00000000000..8a4a130cc19 --- /dev/null +++ b/include/linux/clocksource.h @@ -0,0 +1,311 @@ +/* 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/cache.h> +#include <linux/timer.h> +#include <linux/init.h> +#include <asm/div64.h> +#include <asm/io.h> + +/* 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) / 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_cyc2ns - converts clocksource cycles to nanoseconds + * + * Converts cycles to nanoseconds, using the given mult and shift. + * + * XXX - This could use some mult_lxl_ll() asm optimization + */ +static inline s64 clocksource_cyc2ns(cycle_t cycles, u32 mult, u32 shift) +{ + return ((u64) cycles * mult) >> 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); + +extern void +clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec); + +static inline void +clocksource_calc_mult_shift(struct clocksource *cs, u32 freq, u32 minsec) +{ + return clocks_calc_mult_shift(&cs->mult, &cs->shift, freq, + NSEC_PER_SEC, minsec); +} + +#ifdef CONFIG_GENERIC_TIME_VSYSCALL +extern void +update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult); +extern void update_vsyscall_tz(void); +#else +static inline void +update_vsyscall(struct timespec *ts, struct clocksource *c, u32 mult) +{ +} + +static inline void update_vsyscall_tz(void) +{ +} +#endif + +extern void timekeeping_notify(struct clocksource *clock); + +#endif /* _LINUX_CLOCKSOURCE_H */ |