2 * linux/kernel/time/timekeeping.c
4 * Kernel timekeeping code and accessor functions
6 * This code was moved from linux/kernel/timer.c.
7 * Please see that file for copyright and history logs.
11 #include <linux/module.h>
12 #include <linux/interrupt.h>
13 #include <linux/percpu.h>
14 #include <linux/init.h>
16 #include <linux/sched.h>
17 #include <linux/syscore_ops.h>
18 #include <linux/clocksource.h>
19 #include <linux/jiffies.h>
20 #include <linux/time.h>
21 #include <linux/tick.h>
22 #include <linux/stop_machine.h>
24 /* Structure holding internal timekeeping values. */
26 /* Current clocksource used for timekeeping. */
27 struct clocksource *clock;
28 /* NTP adjusted clock multiplier */
30 /* The shift value of the current clocksource. */
33 /* Number of clock cycles in one NTP interval. */
34 cycle_t cycle_interval;
35 /* Number of clock shifted nano seconds in one NTP interval. */
37 /* shifted nano seconds left over when rounding cycle_interval */
39 /* Raw nano seconds accumulated per NTP interval. */
42 /* Clock shifted nano seconds remainder not stored in xtime.tv_nsec. */
44 /* Difference between accumulated time and NTP time in ntp
45 * shifted nano seconds. */
47 /* Shift conversion between clock shifted nano seconds and
48 * ntp shifted nano seconds. */
51 /* The current time */
52 struct timespec xtime;
54 * wall_to_monotonic is what we need to add to xtime (or xtime corrected
55 * for sub jiffie times) to get to monotonic time. Monotonic is pegged
56 * at zero at system boot time, so wall_to_monotonic will be negative,
57 * however, we will ALWAYS keep the tv_nsec part positive so we can use
58 * the usual normalization.
60 * wall_to_monotonic is moved after resume from suspend for the
61 * monotonic time not to jump. We need to add total_sleep_time to
62 * wall_to_monotonic to get the real boot based time offset.
64 * - wall_to_monotonic is no longer the boot time, getboottime must be
67 struct timespec wall_to_monotonic;
68 /* time spent in suspend */
69 struct timespec total_sleep_time;
70 /* The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock. */
71 struct timespec raw_time;
73 /* Seqlock for all timekeeper values */
77 static struct timekeeper timekeeper;
80 * This read-write spinlock protects us from races in SMP while
83 __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
86 /* flag for if timekeeping is suspended */
87 int __read_mostly timekeeping_suspended;
92 * timekeeper_setup_internals - Set up internals to use clocksource clock.
94 * @clock: Pointer to clocksource.
96 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
97 * pair and interval request.
99 * Unless you're the timekeeping code, you should not be using this!
101 static void timekeeper_setup_internals(struct clocksource *clock)
104 u64 tmp, ntpinterval;
106 timekeeper.clock = clock;
107 clock->cycle_last = clock->read(clock);
109 /* Do the ns -> cycle conversion first, using original mult */
110 tmp = NTP_INTERVAL_LENGTH;
111 tmp <<= clock->shift;
113 tmp += clock->mult/2;
114 do_div(tmp, clock->mult);
118 interval = (cycle_t) tmp;
119 timekeeper.cycle_interval = interval;
121 /* Go back from cycles -> shifted ns */
122 timekeeper.xtime_interval = (u64) interval * clock->mult;
123 timekeeper.xtime_remainder = ntpinterval - timekeeper.xtime_interval;
124 timekeeper.raw_interval =
125 ((u64) interval * clock->mult) >> clock->shift;
127 timekeeper.xtime_nsec = 0;
128 timekeeper.shift = clock->shift;
130 timekeeper.ntp_error = 0;
131 timekeeper.ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
134 * The timekeeper keeps its own mult values for the currently
135 * active clocksource. These value will be adjusted via NTP
136 * to counteract clock drifting.
138 timekeeper.mult = clock->mult;
141 /* Timekeeper helper functions. */
142 static inline s64 timekeeping_get_ns(void)
144 cycle_t cycle_now, cycle_delta;
145 struct clocksource *clock;
147 /* read clocksource: */
148 clock = timekeeper.clock;
149 cycle_now = clock->read(clock);
151 /* calculate the delta since the last update_wall_time: */
152 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
154 /* return delta convert to nanoseconds using ntp adjusted mult. */
155 return clocksource_cyc2ns(cycle_delta, timekeeper.mult,
159 static inline s64 timekeeping_get_ns_raw(void)
161 cycle_t cycle_now, cycle_delta;
162 struct clocksource *clock;
164 /* read clocksource: */
165 clock = timekeeper.clock;
166 cycle_now = clock->read(clock);
168 /* calculate the delta since the last update_wall_time: */
169 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
171 /* return delta convert to nanoseconds. */
172 return clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
175 /* must hold write on timekeeper.lock */
176 static void timekeeping_update(bool clearntp)
179 timekeeper.ntp_error = 0;
182 update_vsyscall(&timekeeper.xtime, &timekeeper.wall_to_monotonic,
183 timekeeper.clock, timekeeper.mult);
187 void timekeeping_leap_insert(int leapsecond)
191 write_seqlock_irqsave(&timekeeper.lock, flags);
192 timekeeper.xtime.tv_sec += leapsecond;
193 timekeeper.wall_to_monotonic.tv_sec -= leapsecond;
194 timekeeping_update(false);
195 write_sequnlock_irqrestore(&timekeeper.lock, flags);
200 * timekeeping_forward_now - update clock to the current time
202 * Forward the current clock to update its state since the last call to
203 * update_wall_time(). This is useful before significant clock changes,
204 * as it avoids having to deal with this time offset explicitly.
206 static void timekeeping_forward_now(void)
208 cycle_t cycle_now, cycle_delta;
209 struct clocksource *clock;
212 clock = timekeeper.clock;
213 cycle_now = clock->read(clock);
214 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
215 clock->cycle_last = cycle_now;
217 nsec = clocksource_cyc2ns(cycle_delta, timekeeper.mult,
220 /* If arch requires, add in gettimeoffset() */
221 nsec += arch_gettimeoffset();
223 timespec_add_ns(&timekeeper.xtime, nsec);
225 nsec = clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
226 timespec_add_ns(&timekeeper.raw_time, nsec);
230 * getnstimeofday - Returns the time of day in a timespec
231 * @ts: pointer to the timespec to be set
233 * Returns the time of day in a timespec.
235 void getnstimeofday(struct timespec *ts)
240 WARN_ON(timekeeping_suspended);
243 seq = read_seqbegin(&timekeeper.lock);
245 *ts = timekeeper.xtime;
246 nsecs = timekeeping_get_ns();
248 /* If arch requires, add in gettimeoffset() */
249 nsecs += arch_gettimeoffset();
251 } while (read_seqretry(&timekeeper.lock, seq));
253 timespec_add_ns(ts, nsecs);
256 EXPORT_SYMBOL(getnstimeofday);
258 ktime_t ktime_get(void)
263 WARN_ON(timekeeping_suspended);
266 seq = read_seqbegin(&timekeeper.lock);
267 secs = timekeeper.xtime.tv_sec +
268 timekeeper.wall_to_monotonic.tv_sec;
269 nsecs = timekeeper.xtime.tv_nsec +
270 timekeeper.wall_to_monotonic.tv_nsec;
271 nsecs += timekeeping_get_ns();
272 /* If arch requires, add in gettimeoffset() */
273 nsecs += arch_gettimeoffset();
275 } while (read_seqretry(&timekeeper.lock, seq));
277 * Use ktime_set/ktime_add_ns to create a proper ktime on
278 * 32-bit architectures without CONFIG_KTIME_SCALAR.
280 return ktime_add_ns(ktime_set(secs, 0), nsecs);
282 EXPORT_SYMBOL_GPL(ktime_get);
285 * ktime_get_ts - get the monotonic clock in timespec format
286 * @ts: pointer to timespec variable
288 * The function calculates the monotonic clock from the realtime
289 * clock and the wall_to_monotonic offset and stores the result
290 * in normalized timespec format in the variable pointed to by @ts.
292 void ktime_get_ts(struct timespec *ts)
294 struct timespec tomono;
298 WARN_ON(timekeeping_suspended);
301 seq = read_seqbegin(&timekeeper.lock);
302 *ts = timekeeper.xtime;
303 tomono = timekeeper.wall_to_monotonic;
304 nsecs = timekeeping_get_ns();
305 /* If arch requires, add in gettimeoffset() */
306 nsecs += arch_gettimeoffset();
308 } while (read_seqretry(&timekeeper.lock, seq));
310 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
311 ts->tv_nsec + tomono.tv_nsec + nsecs);
313 EXPORT_SYMBOL_GPL(ktime_get_ts);
315 #ifdef CONFIG_NTP_PPS
318 * getnstime_raw_and_real - get day and raw monotonic time in timespec format
319 * @ts_raw: pointer to the timespec to be set to raw monotonic time
320 * @ts_real: pointer to the timespec to be set to the time of day
322 * This function reads both the time of day and raw monotonic time at the
323 * same time atomically and stores the resulting timestamps in timespec
326 void getnstime_raw_and_real(struct timespec *ts_raw, struct timespec *ts_real)
329 s64 nsecs_raw, nsecs_real;
331 WARN_ON_ONCE(timekeeping_suspended);
336 seq = read_seqbegin(&timekeeper.lock);
338 *ts_raw = timekeeper.raw_time;
339 *ts_real = timekeeper.xtime;
341 nsecs_raw = timekeeping_get_ns_raw();
342 nsecs_real = timekeeping_get_ns();
344 /* If arch requires, add in gettimeoffset() */
345 arch_offset = arch_gettimeoffset();
346 nsecs_raw += arch_offset;
347 nsecs_real += arch_offset;
349 } while (read_seqretry(&timekeeper.lock, seq));
351 timespec_add_ns(ts_raw, nsecs_raw);
352 timespec_add_ns(ts_real, nsecs_real);
354 EXPORT_SYMBOL(getnstime_raw_and_real);
356 #endif /* CONFIG_NTP_PPS */
359 * do_gettimeofday - Returns the time of day in a timeval
360 * @tv: pointer to the timeval to be set
362 * NOTE: Users should be converted to using getnstimeofday()
364 void do_gettimeofday(struct timeval *tv)
368 getnstimeofday(&now);
369 tv->tv_sec = now.tv_sec;
370 tv->tv_usec = now.tv_nsec/1000;
373 EXPORT_SYMBOL(do_gettimeofday);
375 * do_settimeofday - Sets the time of day
376 * @tv: pointer to the timespec variable containing the new time
378 * Sets the time of day to the new time and update NTP and notify hrtimers
380 int do_settimeofday(const struct timespec *tv)
382 struct timespec ts_delta;
385 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
388 write_seqlock_irqsave(&timekeeper.lock, flags);
390 timekeeping_forward_now();
392 ts_delta.tv_sec = tv->tv_sec - timekeeper.xtime.tv_sec;
393 ts_delta.tv_nsec = tv->tv_nsec - timekeeper.xtime.tv_nsec;
394 timekeeper.wall_to_monotonic =
395 timespec_sub(timekeeper.wall_to_monotonic, ts_delta);
397 timekeeper.xtime = *tv;
398 timekeeping_update(true);
400 write_sequnlock_irqrestore(&timekeeper.lock, flags);
402 /* signal hrtimers about time change */
408 EXPORT_SYMBOL(do_settimeofday);
412 * timekeeping_inject_offset - Adds or subtracts from the current time.
413 * @tv: pointer to the timespec variable containing the offset
415 * Adds or subtracts an offset value from the current time.
417 int timekeeping_inject_offset(struct timespec *ts)
421 if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
424 write_seqlock_irqsave(&timekeeper.lock, flags);
426 timekeeping_forward_now();
428 timekeeper.xtime = timespec_add(timekeeper.xtime, *ts);
429 timekeeper.wall_to_monotonic =
430 timespec_sub(timekeeper.wall_to_monotonic, *ts);
432 timekeeping_update(true);
434 write_sequnlock_irqrestore(&timekeeper.lock, flags);
436 /* signal hrtimers about time change */
441 EXPORT_SYMBOL(timekeeping_inject_offset);
444 * change_clocksource - Swaps clocksources if a new one is available
446 * Accumulates current time interval and initializes new clocksource
448 static int change_clocksource(void *data)
450 struct clocksource *new, *old;
453 new = (struct clocksource *) data;
455 write_seqlock_irqsave(&timekeeper.lock, flags);
457 timekeeping_forward_now();
458 if (!new->enable || new->enable(new) == 0) {
459 old = timekeeper.clock;
460 timekeeper_setup_internals(new);
464 timekeeping_update(true);
466 write_sequnlock_irqrestore(&timekeeper.lock, flags);
472 * timekeeping_notify - Install a new clock source
473 * @clock: pointer to the clock source
475 * This function is called from clocksource.c after a new, better clock
476 * source has been registered. The caller holds the clocksource_mutex.
478 void timekeeping_notify(struct clocksource *clock)
480 if (timekeeper.clock == clock)
482 stop_machine(change_clocksource, clock, NULL);
487 * ktime_get_real - get the real (wall-) time in ktime_t format
489 * returns the time in ktime_t format
491 ktime_t ktime_get_real(void)
495 getnstimeofday(&now);
497 return timespec_to_ktime(now);
499 EXPORT_SYMBOL_GPL(ktime_get_real);
502 * getrawmonotonic - Returns the raw monotonic time in a timespec
503 * @ts: pointer to the timespec to be set
505 * Returns the raw monotonic time (completely un-modified by ntp)
507 void getrawmonotonic(struct timespec *ts)
513 seq = read_seqbegin(&timekeeper.lock);
514 nsecs = timekeeping_get_ns_raw();
515 *ts = timekeeper.raw_time;
517 } while (read_seqretry(&timekeeper.lock, seq));
519 timespec_add_ns(ts, nsecs);
521 EXPORT_SYMBOL(getrawmonotonic);
525 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
527 int timekeeping_valid_for_hres(void)
533 seq = read_seqbegin(&timekeeper.lock);
535 ret = timekeeper.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
537 } while (read_seqretry(&timekeeper.lock, seq));
543 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
545 u64 timekeeping_max_deferment(void)
550 seq = read_seqbegin(&timekeeper.lock);
552 ret = timekeeper.clock->max_idle_ns;
554 } while (read_seqretry(&timekeeper.lock, seq));
560 * read_persistent_clock - Return time from the persistent clock.
562 * Weak dummy function for arches that do not yet support it.
563 * Reads the time from the battery backed persistent clock.
564 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
566 * XXX - Do be sure to remove it once all arches implement it.
568 void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
575 * read_boot_clock - Return time of the system start.
577 * Weak dummy function for arches that do not yet support it.
578 * Function to read the exact time the system has been started.
579 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
581 * XXX - Do be sure to remove it once all arches implement it.
583 void __attribute__((weak)) read_boot_clock(struct timespec *ts)
590 * timekeeping_init - Initializes the clocksource and common timekeeping values
592 void __init timekeeping_init(void)
594 struct clocksource *clock;
596 struct timespec now, boot;
598 read_persistent_clock(&now);
599 read_boot_clock(&boot);
601 seqlock_init(&timekeeper.lock);
605 write_seqlock_irqsave(&timekeeper.lock, flags);
606 clock = clocksource_default_clock();
608 clock->enable(clock);
609 timekeeper_setup_internals(clock);
611 timekeeper.xtime.tv_sec = now.tv_sec;
612 timekeeper.xtime.tv_nsec = now.tv_nsec;
613 timekeeper.raw_time.tv_sec = 0;
614 timekeeper.raw_time.tv_nsec = 0;
615 if (boot.tv_sec == 0 && boot.tv_nsec == 0) {
616 boot.tv_sec = timekeeper.xtime.tv_sec;
617 boot.tv_nsec = timekeeper.xtime.tv_nsec;
619 set_normalized_timespec(&timekeeper.wall_to_monotonic,
620 -boot.tv_sec, -boot.tv_nsec);
621 timekeeper.total_sleep_time.tv_sec = 0;
622 timekeeper.total_sleep_time.tv_nsec = 0;
623 write_sequnlock_irqrestore(&timekeeper.lock, flags);
626 /* time in seconds when suspend began */
627 static struct timespec timekeeping_suspend_time;
630 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
631 * @delta: pointer to a timespec delta value
633 * Takes a timespec offset measuring a suspend interval and properly
634 * adds the sleep offset to the timekeeping variables.
636 static void __timekeeping_inject_sleeptime(struct timespec *delta)
638 if (!timespec_valid(delta)) {
639 printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid "
640 "sleep delta value!\n");
644 timekeeper.xtime = timespec_add(timekeeper.xtime, *delta);
645 timekeeper.wall_to_monotonic =
646 timespec_sub(timekeeper.wall_to_monotonic, *delta);
647 timekeeper.total_sleep_time = timespec_add(
648 timekeeper.total_sleep_time, *delta);
653 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
654 * @delta: pointer to a timespec delta value
656 * This hook is for architectures that cannot support read_persistent_clock
657 * because their RTC/persistent clock is only accessible when irqs are enabled.
659 * This function should only be called by rtc_resume(), and allows
660 * a suspend offset to be injected into the timekeeping values.
662 void timekeeping_inject_sleeptime(struct timespec *delta)
667 /* Make sure we don't set the clock twice */
668 read_persistent_clock(&ts);
669 if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
672 write_seqlock_irqsave(&timekeeper.lock, flags);
674 timekeeping_forward_now();
676 __timekeeping_inject_sleeptime(delta);
678 timekeeping_update(true);
680 write_sequnlock_irqrestore(&timekeeper.lock, flags);
682 /* signal hrtimers about time change */
688 * timekeeping_resume - Resumes the generic timekeeping subsystem.
690 * This is for the generic clocksource timekeeping.
691 * xtime/wall_to_monotonic/jiffies/etc are
692 * still managed by arch specific suspend/resume code.
694 static void timekeeping_resume(void)
699 read_persistent_clock(&ts);
701 clocksource_resume();
703 write_seqlock_irqsave(&timekeeper.lock, flags);
705 if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
706 ts = timespec_sub(ts, timekeeping_suspend_time);
707 __timekeeping_inject_sleeptime(&ts);
709 /* re-base the last cycle value */
710 timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
711 timekeeper.ntp_error = 0;
712 timekeeping_suspended = 0;
713 write_sequnlock_irqrestore(&timekeeper.lock, flags);
715 touch_softlockup_watchdog();
717 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
719 /* Resume hrtimers */
723 static int timekeeping_suspend(void)
726 struct timespec delta, delta_delta;
727 static struct timespec old_delta;
729 read_persistent_clock(&timekeeping_suspend_time);
731 write_seqlock_irqsave(&timekeeper.lock, flags);
732 timekeeping_forward_now();
733 timekeeping_suspended = 1;
736 * To avoid drift caused by repeated suspend/resumes,
737 * which each can add ~1 second drift error,
738 * try to compensate so the difference in system time
739 * and persistent_clock time stays close to constant.
741 delta = timespec_sub(timekeeper.xtime, timekeeping_suspend_time);
742 delta_delta = timespec_sub(delta, old_delta);
743 if (abs(delta_delta.tv_sec) >= 2) {
745 * if delta_delta is too large, assume time correction
746 * has occured and set old_delta to the current delta.
750 /* Otherwise try to adjust old_system to compensate */
751 timekeeping_suspend_time =
752 timespec_add(timekeeping_suspend_time, delta_delta);
754 write_sequnlock_irqrestore(&timekeeper.lock, flags);
756 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
757 clocksource_suspend();
762 /* sysfs resume/suspend bits for timekeeping */
763 static struct syscore_ops timekeeping_syscore_ops = {
764 .resume = timekeeping_resume,
765 .suspend = timekeeping_suspend,
768 static int __init timekeeping_init_ops(void)
770 register_syscore_ops(&timekeeping_syscore_ops);
774 device_initcall(timekeeping_init_ops);
777 * If the error is already larger, we look ahead even further
778 * to compensate for late or lost adjustments.
780 static __always_inline int timekeeping_bigadjust(s64 error, s64 *interval,
788 * Use the current error value to determine how much to look ahead.
789 * The larger the error the slower we adjust for it to avoid problems
790 * with losing too many ticks, otherwise we would overadjust and
791 * produce an even larger error. The smaller the adjustment the
792 * faster we try to adjust for it, as lost ticks can do less harm
793 * here. This is tuned so that an error of about 1 msec is adjusted
794 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
796 error2 = timekeeper.ntp_error >> (NTP_SCALE_SHIFT + 22 - 2 * SHIFT_HZ);
797 error2 = abs(error2);
798 for (look_ahead = 0; error2 > 0; look_ahead++)
802 * Now calculate the error in (1 << look_ahead) ticks, but first
803 * remove the single look ahead already included in the error.
805 tick_error = ntp_tick_length() >> (timekeeper.ntp_error_shift + 1);
806 tick_error -= timekeeper.xtime_interval >> 1;
807 error = ((error - tick_error) >> look_ahead) + tick_error;
809 /* Finally calculate the adjustment shift value. */
814 *interval = -*interval;
818 for (adj = 0; error > i; adj++)
827 * Adjust the multiplier to reduce the error value,
828 * this is optimized for the most common adjustments of -1,0,1,
829 * for other values we can do a bit more work.
831 static void timekeeping_adjust(s64 offset)
833 s64 error, interval = timekeeper.cycle_interval;
837 * The point of this is to check if the error is greater then half
840 * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
842 * Note we subtract one in the shift, so that error is really error*2.
843 * This "saves" dividing(shifting) interval twice, but keeps the
844 * (error > interval) comparison as still measuring if error is
845 * larger then half an interval.
847 * Note: It does not "save" on aggravation when reading the code.
849 error = timekeeper.ntp_error >> (timekeeper.ntp_error_shift - 1);
850 if (error > interval) {
852 * We now divide error by 4(via shift), which checks if
853 * the error is greater then twice the interval.
854 * If it is greater, we need a bigadjust, if its smaller,
855 * we can adjust by 1.
859 * XXX - In update_wall_time, we round up to the next
860 * nanosecond, and store the amount rounded up into
861 * the error. This causes the likely below to be unlikely.
863 * The proper fix is to avoid rounding up by using
864 * the high precision timekeeper.xtime_nsec instead of
865 * xtime.tv_nsec everywhere. Fixing this will take some
868 if (likely(error <= interval))
871 adj = timekeeping_bigadjust(error, &interval, &offset);
872 } else if (error < -interval) {
873 /* See comment above, this is just switched for the negative */
875 if (likely(error >= -interval)) {
877 interval = -interval;
880 adj = timekeeping_bigadjust(error, &interval, &offset);
881 } else /* No adjustment needed */
884 WARN_ONCE(timekeeper.clock->maxadj &&
885 (timekeeper.mult + adj > timekeeper.clock->mult +
886 timekeeper.clock->maxadj),
887 "Adjusting %s more then 11%% (%ld vs %ld)\n",
888 timekeeper.clock->name, (long)timekeeper.mult + adj,
889 (long)timekeeper.clock->mult +
890 timekeeper.clock->maxadj);
892 * So the following can be confusing.
894 * To keep things simple, lets assume adj == 1 for now.
896 * When adj != 1, remember that the interval and offset values
897 * have been appropriately scaled so the math is the same.
899 * The basic idea here is that we're increasing the multiplier
900 * by one, this causes the xtime_interval to be incremented by
901 * one cycle_interval. This is because:
902 * xtime_interval = cycle_interval * mult
903 * So if mult is being incremented by one:
904 * xtime_interval = cycle_interval * (mult + 1)
906 * xtime_interval = (cycle_interval * mult) + cycle_interval
907 * Which can be shortened to:
908 * xtime_interval += cycle_interval
910 * So offset stores the non-accumulated cycles. Thus the current
911 * time (in shifted nanoseconds) is:
912 * now = (offset * adj) + xtime_nsec
913 * Now, even though we're adjusting the clock frequency, we have
914 * to keep time consistent. In other words, we can't jump back
915 * in time, and we also want to avoid jumping forward in time.
917 * So given the same offset value, we need the time to be the same
918 * both before and after the freq adjustment.
919 * now = (offset * adj_1) + xtime_nsec_1
920 * now = (offset * adj_2) + xtime_nsec_2
922 * (offset * adj_1) + xtime_nsec_1 =
923 * (offset * adj_2) + xtime_nsec_2
927 * (offset * adj_1) + xtime_nsec_1 =
928 * (offset * (adj_1+1)) + xtime_nsec_2
929 * (offset * adj_1) + xtime_nsec_1 =
930 * (offset * adj_1) + offset + xtime_nsec_2
931 * Canceling the sides:
932 * xtime_nsec_1 = offset + xtime_nsec_2
934 * xtime_nsec_2 = xtime_nsec_1 - offset
935 * Which simplfies to:
936 * xtime_nsec -= offset
938 * XXX - TODO: Doc ntp_error calculation.
940 timekeeper.mult += adj;
941 timekeeper.xtime_interval += interval;
942 timekeeper.xtime_nsec -= offset;
943 timekeeper.ntp_error -= (interval - offset) <<
944 timekeeper.ntp_error_shift;
949 * logarithmic_accumulation - shifted accumulation of cycles
951 * This functions accumulates a shifted interval of cycles into
952 * into a shifted interval nanoseconds. Allows for O(log) accumulation
955 * Returns the unconsumed cycles.
957 static cycle_t logarithmic_accumulation(cycle_t offset, int shift)
959 u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift;
962 /* If the offset is smaller then a shifted interval, do nothing */
963 if (offset < timekeeper.cycle_interval<<shift)
966 /* Accumulate one shifted interval */
967 offset -= timekeeper.cycle_interval << shift;
968 timekeeper.clock->cycle_last += timekeeper.cycle_interval << shift;
970 timekeeper.xtime_nsec += timekeeper.xtime_interval << shift;
971 while (timekeeper.xtime_nsec >= nsecps) {
972 timekeeper.xtime_nsec -= nsecps;
973 timekeeper.xtime.tv_sec++;
977 /* Accumulate raw time */
978 raw_nsecs = timekeeper.raw_interval << shift;
979 raw_nsecs += timekeeper.raw_time.tv_nsec;
980 if (raw_nsecs >= NSEC_PER_SEC) {
981 u64 raw_secs = raw_nsecs;
982 raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
983 timekeeper.raw_time.tv_sec += raw_secs;
985 timekeeper.raw_time.tv_nsec = raw_nsecs;
987 /* Accumulate error between NTP and clock interval */
988 timekeeper.ntp_error += ntp_tick_length() << shift;
989 timekeeper.ntp_error -=
990 (timekeeper.xtime_interval + timekeeper.xtime_remainder) <<
991 (timekeeper.ntp_error_shift + shift);
998 * update_wall_time - Uses the current clocksource to increment the wall time
1001 static void update_wall_time(void)
1003 struct clocksource *clock;
1005 int shift = 0, maxshift;
1006 unsigned long flags;
1008 write_seqlock_irqsave(&timekeeper.lock, flags);
1010 /* Make sure we're fully resumed: */
1011 if (unlikely(timekeeping_suspended))
1014 clock = timekeeper.clock;
1016 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
1017 offset = timekeeper.cycle_interval;
1019 offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
1021 timekeeper.xtime_nsec = (s64)timekeeper.xtime.tv_nsec <<
1025 * With NO_HZ we may have to accumulate many cycle_intervals
1026 * (think "ticks") worth of time at once. To do this efficiently,
1027 * we calculate the largest doubling multiple of cycle_intervals
1028 * that is smaller then the offset. We then accumulate that
1029 * chunk in one go, and then try to consume the next smaller
1032 shift = ilog2(offset) - ilog2(timekeeper.cycle_interval);
1033 shift = max(0, shift);
1034 /* Bound shift to one less then what overflows tick_length */
1035 maxshift = (64 - (ilog2(ntp_tick_length())+1)) - 1;
1036 shift = min(shift, maxshift);
1037 while (offset >= timekeeper.cycle_interval) {
1038 offset = logarithmic_accumulation(offset, shift);
1039 if(offset < timekeeper.cycle_interval<<shift)
1043 /* correct the clock when NTP error is too big */
1044 timekeeping_adjust(offset);
1047 * Since in the loop above, we accumulate any amount of time
1048 * in xtime_nsec over a second into xtime.tv_sec, its possible for
1049 * xtime_nsec to be fairly small after the loop. Further, if we're
1050 * slightly speeding the clocksource up in timekeeping_adjust(),
1051 * its possible the required corrective factor to xtime_nsec could
1052 * cause it to underflow.
1054 * Now, we cannot simply roll the accumulated second back, since
1055 * the NTP subsystem has been notified via second_overflow. So
1056 * instead we push xtime_nsec forward by the amount we underflowed,
1057 * and add that amount into the error.
1059 * We'll correct this error next time through this function, when
1060 * xtime_nsec is not as small.
1062 if (unlikely((s64)timekeeper.xtime_nsec < 0)) {
1063 s64 neg = -(s64)timekeeper.xtime_nsec;
1064 timekeeper.xtime_nsec = 0;
1065 timekeeper.ntp_error += neg << timekeeper.ntp_error_shift;
1070 * Store full nanoseconds into xtime after rounding it up and
1071 * add the remainder to the error difference.
1073 timekeeper.xtime.tv_nsec = ((s64)timekeeper.xtime_nsec >>
1074 timekeeper.shift) + 1;
1075 timekeeper.xtime_nsec -= (s64)timekeeper.xtime.tv_nsec <<
1077 timekeeper.ntp_error += timekeeper.xtime_nsec <<
1078 timekeeper.ntp_error_shift;
1081 * Finally, make sure that after the rounding
1082 * xtime.tv_nsec isn't larger then NSEC_PER_SEC
1084 if (unlikely(timekeeper.xtime.tv_nsec >= NSEC_PER_SEC)) {
1085 timekeeper.xtime.tv_nsec -= NSEC_PER_SEC;
1086 timekeeper.xtime.tv_sec++;
1090 timekeeping_update(false);
1093 write_sequnlock_irqrestore(&timekeeper.lock, flags);
1098 * getboottime - Return the real time of system boot.
1099 * @ts: pointer to the timespec to be set
1101 * Returns the wall-time of boot in a timespec.
1103 * This is based on the wall_to_monotonic offset and the total suspend
1104 * time. Calls to settimeofday will affect the value returned (which
1105 * basically means that however wrong your real time clock is at boot time,
1106 * you get the right time here).
1108 void getboottime(struct timespec *ts)
1110 struct timespec boottime = {
1111 .tv_sec = timekeeper.wall_to_monotonic.tv_sec +
1112 timekeeper.total_sleep_time.tv_sec,
1113 .tv_nsec = timekeeper.wall_to_monotonic.tv_nsec +
1114 timekeeper.total_sleep_time.tv_nsec
1117 set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
1119 EXPORT_SYMBOL_GPL(getboottime);
1123 * get_monotonic_boottime - Returns monotonic time since boot
1124 * @ts: pointer to the timespec to be set
1126 * Returns the monotonic time since boot in a timespec.
1128 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
1129 * includes the time spent in suspend.
1131 void get_monotonic_boottime(struct timespec *ts)
1133 struct timespec tomono, sleep;
1137 WARN_ON(timekeeping_suspended);
1140 seq = read_seqbegin(&timekeeper.lock);
1141 *ts = timekeeper.xtime;
1142 tomono = timekeeper.wall_to_monotonic;
1143 sleep = timekeeper.total_sleep_time;
1144 nsecs = timekeeping_get_ns();
1146 } while (read_seqretry(&timekeeper.lock, seq));
1148 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec,
1149 ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec + nsecs);
1151 EXPORT_SYMBOL_GPL(get_monotonic_boottime);
1154 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1156 * Returns the monotonic time since boot in a ktime
1158 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1159 * includes the time spent in suspend.
1161 ktime_t ktime_get_boottime(void)
1165 get_monotonic_boottime(&ts);
1166 return timespec_to_ktime(ts);
1168 EXPORT_SYMBOL_GPL(ktime_get_boottime);
1171 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1172 * @ts: pointer to the timespec to be converted
1174 void monotonic_to_bootbased(struct timespec *ts)
1176 *ts = timespec_add(*ts, timekeeper.total_sleep_time);
1178 EXPORT_SYMBOL_GPL(monotonic_to_bootbased);
1180 unsigned long get_seconds(void)
1182 return timekeeper.xtime.tv_sec;
1184 EXPORT_SYMBOL(get_seconds);
1186 struct timespec __current_kernel_time(void)
1188 return timekeeper.xtime;
1191 struct timespec current_kernel_time(void)
1193 struct timespec now;
1197 seq = read_seqbegin(&timekeeper.lock);
1199 now = timekeeper.xtime;
1200 } while (read_seqretry(&timekeeper.lock, seq));
1204 EXPORT_SYMBOL(current_kernel_time);
1206 struct timespec get_monotonic_coarse(void)
1208 struct timespec now, mono;
1212 seq = read_seqbegin(&timekeeper.lock);
1214 now = timekeeper.xtime;
1215 mono = timekeeper.wall_to_monotonic;
1216 } while (read_seqretry(&timekeeper.lock, seq));
1218 set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,
1219 now.tv_nsec + mono.tv_nsec);
1224 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1225 * without sampling the sequence number in xtime_lock.
1226 * jiffies is defined in the linker script...
1228 void do_timer(unsigned long ticks)
1230 jiffies_64 += ticks;
1232 calc_global_load(ticks);
1236 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1237 * and sleep offsets.
1238 * @xtim: pointer to timespec to be set with xtime
1239 * @wtom: pointer to timespec to be set with wall_to_monotonic
1240 * @sleep: pointer to timespec to be set with time in suspend
1242 void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
1243 struct timespec *wtom, struct timespec *sleep)
1248 seq = read_seqbegin(&timekeeper.lock);
1249 *xtim = timekeeper.xtime;
1250 *wtom = timekeeper.wall_to_monotonic;
1251 *sleep = timekeeper.total_sleep_time;
1252 } while (read_seqretry(&timekeeper.lock, seq));
1256 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1258 ktime_t ktime_get_monotonic_offset(void)
1261 struct timespec wtom;
1264 seq = read_seqbegin(&timekeeper.lock);
1265 wtom = timekeeper.wall_to_monotonic;
1266 } while (read_seqretry(&timekeeper.lock, seq));
1268 return timespec_to_ktime(wtom);
1272 * xtime_update() - advances the timekeeping infrastructure
1273 * @ticks: number of ticks, that have elapsed since the last call.
1275 * Must be called with interrupts disabled.
1277 void xtime_update(unsigned long ticks)
1279 write_seqlock(&xtime_lock);
1281 write_sequnlock(&xtime_lock);