/* * linux/kernel/time/timekeeping.c * * Kernel timekeeping code and accessor functions * * This code was moved from linux/kernel/timer.c. * Please see that file for copyright and history logs. * */ #include <linux/module.h> #include <linux/interrupt.h> #include <linux/percpu.h> #include <linux/init.h> #include <linux/mm.h> #include <linux/sched.h> #include <linux/sysdev.h> #include <linux/clocksource.h> #include <linux/jiffies.h> #include <linux/time.h> #include <linux/tick.h> #include <linux/stop_machine.h> /* Structure holding internal timekeeping values. */ struct timekeeper { /* Current clocksource used for timekeeping. */ struct clocksource *clock; /* The shift value of the current clocksource. */ int shift; /* Number of clock cycles in one NTP interval. */ cycle_t cycle_interval; /* Number of clock shifted nano seconds in one NTP interval. */ u64 xtime_interval; /* Raw nano seconds accumulated per NTP interval. */ u32 raw_interval; /* Clock shifted nano seconds remainder not stored in xtime.tv_nsec. */ u64 xtime_nsec; /* Difference between accumulated time and NTP time in ntp * shifted nano seconds. */ s64 ntp_error; /* Shift conversion between clock shifted nano seconds and * ntp shifted nano seconds. */ int ntp_error_shift; /* NTP adjusted clock multiplier */ u32 mult; }; struct timekeeper timekeeper; /** * timekeeper_setup_internals - Set up internals to use clocksource clock. * * @clock: Pointer to clocksource. * * 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 void timekeeper_setup_internals(struct clocksource *clock) { cycle_t interval; u64 tmp; timekeeper.clock = clock; clock->cycle_last = clock->read(clock); /* Do the ns -> cycle conversion first, using original mult */ tmp = NTP_INTERVAL_LENGTH; tmp <<= clock->shift; tmp += clock->mult/2; do_div(tmp, clock->mult); if (tmp == 0) tmp = 1; interval = (cycle_t) tmp; timekeeper.cycle_interval = interval; /* Go back from cycles -> shifted ns */ timekeeper.xtime_interval = (u64) interval * clock->mult; timekeeper.raw_interval = ((u64) interval * clock->mult) >> clock->shift; timekeeper.xtime_nsec = 0; timekeeper.shift = clock->shift; timekeeper.ntp_error = 0; timekeeper.ntp_error_shift = NTP_SCALE_SHIFT - clock->shift; /* * The timekeeper keeps its own mult values for the currently * active clocksource. These value will be adjusted via NTP * to counteract clock drifting. */ timekeeper.mult = clock->mult; } /* Timekeeper helper functions. */ static inline s64 timekeeping_get_ns(void) { cycle_t cycle_now, cycle_delta; struct clocksource *clock; /* read clocksource: */ clock = timekeeper.clock; cycle_now = clock->read(clock); /* calculate the delta since the last update_wall_time: */ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; /* return delta convert to nanoseconds using ntp adjusted mult. */ return clocksource_cyc2ns(cycle_delta, timekeeper.mult, timekeeper.shift); } static inline s64 timekeeping_get_ns_raw(void) { cycle_t cycle_now, cycle_delta; struct clocksource *clock; /* read clocksource: */ clock = timekeeper.clock; cycle_now = clock->read(clock); /* calculate the delta since the last update_wall_time: */ cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; /* return delta convert to nanoseconds using ntp adjusted mult. */ return clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift); } /* * This read-write spinlock protects us from races in SMP while * playing with xtime. */ __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); /* * The current time * wall_to_monotonic is what we need to add to xtime (or xtime corrected * for sub jiffie times) to get to monotonic time. Monotonic is pegged * at zero at system boot time, so wall_to_monotonic will be negative, * however, we will ALWAYS keep the tv_nsec part positive so we can use * the usual normalization. * * wall_to_monotonic is moved after resume from suspend for the monotonic * time not to jump. We need to add total_sleep_time to wall_to_monotonic * to get the real boot based time offset. * * - wall_to_monotonic is no longer the boot time, getboottime must be * used instead. */ struct timespec xtime __attribute__ ((aligned (16))); struct timespec wall_to_monotonic __attribute__ ((aligned (16))); static struct timespec total_sleep_time; /* * The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */ struct timespec raw_time; /* flag for if timekeeping is suspended */ int __read_mostly timekeeping_suspended; static struct timespec xtime_cache __attribute__ ((aligned (16))); void update_xtime_cache(u64 nsec) { xtime_cache = xtime; timespec_add_ns(&xtime_cache, nsec); } /* must hold xtime_lock */ void timekeeping_leap_insert(int leapsecond) { xtime.tv_sec += leapsecond; wall_to_monotonic.tv_sec -= leapsecond; update_vsyscall(&xtime, timekeeper.clock); } #ifdef CONFIG_GENERIC_TIME /** * timekeeping_forward_now - update clock to the current time * * Forward the current clock to update its state since the last call to * update_wall_time(). This is useful before significant clock changes, * as it avoids having to deal with this time offset explicitly. */ static void timekeeping_forward_now(void) { cycle_t cycle_now, cycle_delta; struct clocksource *clock; s64 nsec; clock = timekeeper.clock; cycle_now = clock->read(clock); cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; clock->cycle_last = cycle_now; nsec = clocksource_cyc2ns(cycle_delta, timekeeper.mult, timekeeper.shift); /* If arch requires, add in gettimeoffset() */ nsec += arch_gettimeoffset(); timespec_add_ns(&xtime, nsec); nsec = clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift); timespec_add_ns(&raw_time, nsec); } /** * getnstimeofday - Returns the time of day in a timespec * @ts: pointer to the timespec to be set * * Returns the time of day in a timespec. */ void getnstimeofday(struct timespec *ts) { unsigned long seq; s64 nsecs; WARN_ON(timekeeping_suspended); do { seq = read_seqbegin(&xtime_lock); *ts = xtime; nsecs = timekeeping_get_ns(); /* If arch requires, add in gettimeoffset() */ nsecs += arch_gettimeoffset(); } while (read_seqretry(&xtime_lock, seq)); timespec_add_ns(ts, nsecs); } EXPORT_SYMBOL(getnstimeofday); ktime_t ktime_get(void) { unsigned int seq; s64 secs, nsecs; WARN_ON(timekeeping_suspended); do { seq = read_seqbegin(&xtime_lock); secs = xtime.tv_sec + wall_to_monotonic.tv_sec; nsecs = xtime.tv_nsec + wall_to_monotonic.tv_nsec; nsecs += timekeeping_get_ns(); } while (read_seqretry(&xtime_lock, seq)); /* * Use ktime_set/ktime_add_ns to create a proper ktime on * 32-bit architectures without CONFIG_KTIME_SCALAR. */ return ktime_add_ns(ktime_set(secs, 0), nsecs); } EXPORT_SYMBOL_GPL(ktime_get); /** * ktime_get_ts - get the monotonic clock in timespec format * @ts: pointer to timespec variable * * The function calculates the monotonic clock from the realtime * clock and the wall_to_monotonic offset and stores the result * in normalized timespec format in the variable pointed to by @ts. */ void ktime_get_ts(struct timespec *ts) { struct timespec tomono; unsigned int seq; s64 nsecs; WARN_ON(timekeeping_suspended); do { seq = read_seqbegin(&xtime_lock); *ts = xtime; tomono = wall_to_monotonic; nsecs = timekeeping_get_ns(); } while (read_seqretry(&xtime_lock, seq)); set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec, ts->tv_nsec + tomono.tv_nsec + nsecs); } EXPORT_SYMBOL_GPL(ktime_get_ts); /** * do_gettimeofday - Returns the time of day in a timeval * @tv: pointer to the timeval to be set * * NOTE: Users should be converted to using getnstimeofday() */ void do_gettimeofday(struct timeval *tv) { struct timespec now; getnstimeofday(&now); tv->tv_sec = now.tv_sec; tv->tv_usec = now.tv_nsec/1000; } EXPORT_SYMBOL(do_gettimeofday); /** * do_settimeofday - Sets the time of day * @tv: pointer to the timespec variable containing the new time * * Sets the time of day to the new time and update NTP and notify hrtimers */ int do_settimeofday(struct timespec *tv) { struct timespec ts_delta; unsigned long flags; if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) return -EINVAL; write_seqlock_irqsave(&xtime_lock, flags); timekeeping_forward_now(); ts_delta.tv_sec = tv->tv_sec - xtime.tv_sec; ts_delta.tv_nsec = tv->tv_nsec - xtime.tv_nsec; wall_to_monotonic = timespec_sub(wall_to_monotonic, ts_delta); xtime = *tv; update_xtime_cache(0); timekeeper.ntp_error = 0; ntp_clear(); update_vsyscall(&xtime, timekeeper.clock); write_sequnlock_irqrestore(&xtime_lock, flags); /* signal hrtimers about time change */ clock_was_set(); return 0; } EXPORT_SYMBOL(do_settimeofday); /** * change_clocksource - Swaps clocksources if a new one is available * * Accumulates current time interval and initializes new clocksource */ static int change_clocksource(void *data) { struct clocksource *new, *old; new = (struct clocksource *) data; timekeeping_forward_now(); if (!new->enable || new->enable(new) == 0) { old = timekeeper.clock; timekeeper_setup_internals(new); if (old->disable) old->disable(old); } return 0; } /** * timekeeping_notify - Install a new clock source * @clock: pointer to the clock source * * This function is called from clocksource.c after a new, better clock * source has been registered. The caller holds the clocksource_mutex. */ void timekeeping_notify(struct clocksource *clock) { if (timekeeper.clock == clock) return; stop_machine(change_clocksource, clock, NULL); tick_clock_notify(); } #else /* GENERIC_TIME */ static inline void timekeeping_forward_now(void) { } /** * ktime_get - get the monotonic time in ktime_t format * * returns the time in ktime_t format */ ktime_t ktime_get(void) { struct timespec now; ktime_get_ts(&now); return timespec_to_ktime(now); } EXPORT_SYMBOL_GPL(ktime_get); /** * ktime_get_ts - get the monotonic clock in timespec format * @ts: pointer to timespec variable * * The function calculates the monotonic clock from the realtime * clock and the wall_to_monotonic offset and stores the result * in normalized timespec format in the variable pointed to by @ts. */ void ktime_get_ts(struct timespec *ts) { struct timespec tomono; unsigned long seq; do { seq = read_seqbegin(&xtime_lock); getnstimeofday(ts); tomono = wall_to_monotonic; } while (read_seqretry(&xtime_lock, seq)); set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec, ts->tv_nsec + tomono.tv_nsec); } EXPORT_SYMBOL_GPL(ktime_get_ts); #endif /* !GENERIC_TIME */ /** * ktime_get_real - get the real (wall-) time in ktime_t format * * returns the time in ktime_t format */ ktime_t ktime_get_real(void) { struct timespec now; getnstimeofday(&now); return timespec_to_ktime(now); } EXPORT_SYMBOL_GPL(ktime_get_real); /** * getrawmonotonic - Returns the raw monotonic time in a timespec * @ts: pointer to the timespec to be set * * Returns the raw monotonic time (completely un-modified by ntp) */ void getrawmonotonic(struct timespec *ts) { unsigned long seq; s64 nsecs; do { seq = read_seqbegin(&xtime_lock); nsecs = timekeeping_get_ns_raw(); *ts = raw_time; } while (read_seqretry(&xtime_lock, seq)); timespec_add_ns(ts, nsecs); } EXPORT_SYMBOL(getrawmonotonic); /** * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres */ int timekeeping_valid_for_hres(void) { unsigned long seq; int ret; do { seq = read_seqbegin(&xtime_lock); ret = timekeeper.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES; } while (read_seqretry(&xtime_lock, seq)); return ret; } /** * read_persistent_clock - Return time from the persistent clock. * * Weak dummy function for arches that do not yet support it. * Reads the time from the battery backed persistent clock. * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported. * * XXX - Do be sure to remove it once all arches implement it. */ void __attribute__((weak)) read_persistent_clock(struct timespec *ts) { ts->tv_sec = 0; ts->tv_nsec = 0; } /** * read_boot_clock - Return time of the system start. * * Weak dummy function for arches that do not yet support it. * Function to read the exact time the system has been started. * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported. * * XXX - Do be sure to remove it once all arches implement it. */ void __attribute__((weak)) read_boot_clock(struct timespec *ts) { ts->tv_sec = 0; ts->tv_nsec = 0; } /* * timekeeping_init - Initializes the clocksource and common timekeeping values */ void __init timekeeping_init(void) { struct clocksource *clock; unsigned long flags; struct timespec now, boot; read_persistent_clock(&now); read_boot_clock(&boot); write_seqlock_irqsave(&xtime_lock, flags); ntp_init(); clock = clocksource_default_clock(); if (clock->enable) clock->enable(clock); timekeeper_setup_internals(clock); xtime.tv_sec = now.tv_sec; xtime.tv_nsec = now.tv_nsec; raw_time.tv_sec = 0; raw_time.tv_nsec = 0; if (boot.tv_sec == 0 && boot.tv_nsec == 0) { boot.tv_sec = xtime.tv_sec; boot.tv_nsec = xtime.tv_nsec; } set_normalized_timespec(&wall_to_monotonic, -boot.tv_sec, -boot.tv_nsec); update_xtime_cache(0); total_sleep_time.tv_sec = 0; total_sleep_time.tv_nsec = 0; write_sequnlock_irqrestore(&xtime_lock, flags); } /* time in seconds when suspend began */ static struct timespec timekeeping_suspend_time; /** * timekeeping_resume - Resumes the generic timekeeping subsystem. * @dev: unused * * This is for the generic clocksource timekeeping. * xtime/wall_to_monotonic/jiffies/etc are * still managed by arch specific suspend/resume code. */ static int timekeeping_resume(struct sys_device *dev) { unsigned long flags; struct timespec ts; read_persistent_clock(&ts); clocksource_resume(); write_seqlock_irqsave(&xtime_lock, flags); if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) { ts = timespec_sub(ts, timekeeping_suspend_time); xtime = timespec_add_safe(xtime, ts); wall_to_monotonic = timespec_sub(wall_to_monotonic, ts); total_sleep_time = timespec_add_safe(total_sleep_time, ts); } update_xtime_cache(0); /* re-base the last cycle value */ timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock); timekeeper.ntp_error = 0; timekeeping_suspended = 0; write_sequnlock_irqrestore(&xtime_lock, flags); touch_softlockup_watchdog(); clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL); /* Resume hrtimers */ hres_timers_resume(); return 0; } static int timekeeping_suspend(struct sys_device *dev, pm_message_t state) { unsigned long flags; read_persistent_clock(&timekeeping_suspend_time); write_seqlock_irqsave(&xtime_lock, flags); timekeeping_forward_now(); timekeeping_suspended = 1; write_sequnlock_irqrestore(&xtime_lock, flags); clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL); return 0; } /* sysfs resume/suspend bits for timekeeping */ static struct sysdev_class timekeeping_sysclass = { .name = "timekeeping", .resume = timekeeping_resume, .suspend = timekeeping_suspend, }; static struct sys_device device_timer = { .id = 0, .cls = &timekeeping_sysclass, }; static int __init timekeeping_init_device(void) { int error = sysdev_class_register(&timekeeping_sysclass); if (!error) error = sysdev_register(&device_timer); return error; } device_initcall(timekeeping_init_device); /* * If the error is already larger, we look ahead even further * to compensate for late or lost adjustments. */ static __always_inline int timekeeping_bigadjust(s64 error, s64 *interval, s64 *offset) { s64 tick_error, i; u32 look_ahead, adj; s32 error2, mult; /* * Use the current error value to determine how much to look ahead. * The larger the error the slower we adjust for it to avoid problems * with losing too many ticks, otherwise we would overadjust and * produce an even larger error. The smaller the adjustment the * faster we try to adjust for it, as lost ticks can do less harm * here. This is tuned so that an error of about 1 msec is adjusted * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks). */ error2 = timekeeper.ntp_error >> (NTP_SCALE_SHIFT + 22 - 2 * SHIFT_HZ); error2 = abs(error2); for (look_ahead = 0; error2 > 0; look_ahead++) error2 >>= 2; /* * Now calculate the error in (1 << look_ahead) ticks, but first * remove the single look ahead already included in the error. */ tick_error = tick_length >> (timekeeper.ntp_error_shift + 1); tick_error -= timekeeper.xtime_interval >> 1; error = ((error - tick_error) >> look_ahead) + tick_error; /* Finally calculate the adjustment shift value. */ i = *interval; mult = 1; if (error < 0) { error = -error; *interval = -*interval; *offset = -*offset; mult = -1; } for (adj = 0; error > i; adj++) error >>= 1; *interval <<= adj; *offset <<= adj; return mult << adj; } /* * Adjust the multiplier to reduce the error value, * this is optimized for the most common adjustments of -1,0,1, * for other values we can do a bit more work. */ static void timekeeping_adjust(s64 offset) { s64 error, interval = timekeeper.cycle_interval; int adj; error = timekeeper.ntp_error >> (timekeeper.ntp_error_shift - 1); if (error > interval) { error >>= 2; if (likely(error <= interval)) adj = 1; else adj = timekeeping_bigadjust(error, &interval, &offset); } else if (error < -interval) { error >>= 2; if (likely(error >= -interval)) { adj = -1; interval = -interval; offset = -offset; } else adj = timekeeping_bigadjust(error, &interval, &offset); } else return; timekeeper.mult += adj; timekeeper.xtime_interval += interval; timekeeper.xtime_nsec -= offset; timekeeper.ntp_error -= (interval - offset) << timekeeper.ntp_error_shift; } /** * update_wall_time - Uses the current clocksource to increment the wall time * * Called from the timer interrupt, must hold a write on xtime_lock. */ void update_wall_time(void) { struct clocksource *clock; cycle_t offset; u64 nsecs; /* Make sure we're fully resumed: */ if (unlikely(timekeeping_suspended)) return; clock = timekeeper.clock; #ifdef CONFIG_GENERIC_TIME offset = (clock->read(clock) - clock->cycle_last) & clock->mask; #else offset = timekeeper.cycle_interval; #endif timekeeper.xtime_nsec = (s64)xtime.tv_nsec << timekeeper.shift; /* normally this loop will run just once, however in the * case of lost or late ticks, it will accumulate correctly. */ while (offset >= timekeeper.cycle_interval) { u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift; /* accumulate one interval */ offset -= timekeeper.cycle_interval; clock->cycle_last += timekeeper.cycle_interval; timekeeper.xtime_nsec += timekeeper.xtime_interval; if (timekeeper.xtime_nsec >= nsecps) { timekeeper.xtime_nsec -= nsecps; xtime.tv_sec++; second_overflow(); } raw_time.tv_nsec += timekeeper.raw_interval; if (raw_time.tv_nsec >= NSEC_PER_SEC) { raw_time.tv_nsec -= NSEC_PER_SEC; raw_time.tv_sec++; } /* accumulate error between NTP and clock interval */ timekeeper.ntp_error += tick_length; timekeeper.ntp_error -= timekeeper.xtime_interval << timekeeper.ntp_error_shift; } /* correct the clock when NTP error is too big */ timekeeping_adjust(offset); /* * Since in the loop above, we accumulate any amount of time * in xtime_nsec over a second into xtime.tv_sec, its possible for * xtime_nsec to be fairly small after the loop. Further, if we're * slightly speeding the clocksource up in timekeeping_adjust(), * its possible the required corrective factor to xtime_nsec could * cause it to underflow. * * Now, we cannot simply roll the accumulated second back, since * the NTP subsystem has been notified via second_overflow. So * instead we push xtime_nsec forward by the amount we underflowed, * and add that amount into the error. * * We'll correct this error next time through this function, when * xtime_nsec is not as small. */ if (unlikely((s64)timekeeper.xtime_nsec < 0)) { s64 neg = -(s64)timekeeper.xtime_nsec; timekeeper.xtime_nsec = 0; timekeeper.ntp_error += neg << timekeeper.ntp_error_shift; } /* store full nanoseconds into xtime after rounding it up and * add the remainder to the error difference. */ xtime.tv_nsec = ((s64) timekeeper.xtime_nsec >> timekeeper.shift) + 1; timekeeper.xtime_nsec -= (s64) xtime.tv_nsec << timekeeper.shift; timekeeper.ntp_error += timekeeper.xtime_nsec << timekeeper.ntp_error_shift; nsecs = clocksource_cyc2ns(offset, timekeeper.mult, timekeeper.shift); update_xtime_cache(nsecs); /* check to see if there is a new clocksource to use */ update_vsyscall(&xtime, timekeeper.clock); } /** * getboottime - Return the real time of system boot. * @ts: pointer to the timespec to be set * * Returns the time of day in a timespec. * * This is based on the wall_to_monotonic offset and the total suspend * time. Calls to settimeofday will affect the value returned (which * basically means that however wrong your real time clock is at boot time, * you get the right time here). */ void getboottime(struct timespec *ts) { struct timespec boottime = { .tv_sec = wall_to_monotonic.tv_sec + total_sleep_time.tv_sec, .tv_nsec = wall_to_monotonic.tv_nsec + total_sleep_time.tv_nsec }; set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec); } /** * monotonic_to_bootbased - Convert the monotonic time to boot based. * @ts: pointer to the timespec to be converted */ void monotonic_to_bootbased(struct timespec *ts) { *ts = timespec_add_safe(*ts, total_sleep_time); } unsigned long get_seconds(void) { return xtime_cache.tv_sec; } EXPORT_SYMBOL(get_seconds); struct timespec __current_kernel_time(void) { return xtime_cache; } struct timespec current_kernel_time(void) { struct timespec now; unsigned long seq; do { seq = read_seqbegin(&xtime_lock); now = xtime_cache; } while (read_seqretry(&xtime_lock, seq)); return now; } EXPORT_SYMBOL(current_kernel_time); struct timespec get_monotonic_coarse(void) { struct timespec now, mono; unsigned long seq; do { seq = read_seqbegin(&xtime_lock); now = xtime_cache; mono = wall_to_monotonic; } while (read_seqretry(&xtime_lock, seq)); set_normalized_timespec(&now, now.tv_sec + mono.tv_sec, now.tv_nsec + mono.tv_nsec); return now; }