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 /* The shift value of the current clocksource. */
31 /* Number of clock cycles in one NTP interval. */
32 cycle_t cycle_interval;
33 /* Number of clock shifted nano seconds in one NTP interval. */
35 /* shifted nano seconds left over when rounding cycle_interval */
37 /* Raw nano seconds accumulated per NTP interval. */
40 /* Clock shifted nano seconds remainder not stored in xtime.tv_nsec. */
42 /* Difference between accumulated time and NTP time in ntp
43 * shifted nano seconds. */
45 /* Shift conversion between clock shifted nano seconds and
46 * ntp shifted nano seconds. */
48 /* NTP adjusted clock multiplier */
52 static struct timekeeper timekeeper;
55 * timekeeper_setup_internals - Set up internals to use clocksource clock.
57 * @clock: Pointer to clocksource.
59 * Calculates a fixed cycle/nsec interval for a given clocksource/adjustment
60 * pair and interval request.
62 * Unless you're the timekeeping code, you should not be using this!
64 static void timekeeper_setup_internals(struct clocksource *clock)
69 timekeeper.clock = clock;
70 clock->cycle_last = clock->read(clock);
72 /* Do the ns -> cycle conversion first, using original mult */
73 tmp = NTP_INTERVAL_LENGTH;
77 do_div(tmp, clock->mult);
81 interval = (cycle_t) tmp;
82 timekeeper.cycle_interval = interval;
84 /* Go back from cycles -> shifted ns */
85 timekeeper.xtime_interval = (u64) interval * clock->mult;
86 timekeeper.xtime_remainder = ntpinterval - timekeeper.xtime_interval;
87 timekeeper.raw_interval =
88 ((u64) interval * clock->mult) >> clock->shift;
90 timekeeper.xtime_nsec = 0;
91 timekeeper.shift = clock->shift;
93 timekeeper.ntp_error = 0;
94 timekeeper.ntp_error_shift = NTP_SCALE_SHIFT - clock->shift;
97 * The timekeeper keeps its own mult values for the currently
98 * active clocksource. These value will be adjusted via NTP
99 * to counteract clock drifting.
101 timekeeper.mult = clock->mult;
104 /* Timekeeper helper functions. */
105 static inline s64 timekeeping_get_ns(void)
107 cycle_t cycle_now, cycle_delta;
108 struct clocksource *clock;
110 /* read clocksource: */
111 clock = timekeeper.clock;
112 cycle_now = clock->read(clock);
114 /* calculate the delta since the last update_wall_time: */
115 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
117 /* return delta convert to nanoseconds using ntp adjusted mult. */
118 return clocksource_cyc2ns(cycle_delta, timekeeper.mult,
122 static inline s64 timekeeping_get_ns_raw(void)
124 cycle_t cycle_now, cycle_delta;
125 struct clocksource *clock;
127 /* read clocksource: */
128 clock = timekeeper.clock;
129 cycle_now = clock->read(clock);
131 /* calculate the delta since the last update_wall_time: */
132 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
134 /* return delta convert to nanoseconds using ntp adjusted mult. */
135 return clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
139 * This read-write spinlock protects us from races in SMP while
140 * playing with xtime.
142 __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
147 * wall_to_monotonic is what we need to add to xtime (or xtime corrected
148 * for sub jiffie times) to get to monotonic time. Monotonic is pegged
149 * at zero at system boot time, so wall_to_monotonic will be negative,
150 * however, we will ALWAYS keep the tv_nsec part positive so we can use
151 * the usual normalization.
153 * wall_to_monotonic is moved after resume from suspend for the monotonic
154 * time not to jump. We need to add total_sleep_time to wall_to_monotonic
155 * to get the real boot based time offset.
157 * - wall_to_monotonic is no longer the boot time, getboottime must be
160 static struct timespec xtime __attribute__ ((aligned (16)));
161 static struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
162 static struct timespec total_sleep_time;
164 /* Offset clock monotonic -> clock realtime */
165 static ktime_t offs_real;
167 /* Offset clock monotonic -> clock boottime */
168 static ktime_t offs_boot;
171 * The raw monotonic time for the CLOCK_MONOTONIC_RAW posix clock.
173 static struct timespec raw_time;
175 /* must hold write on xtime_lock */
176 static void update_rt_offset(void)
178 struct timespec tmp, *wtm = &wall_to_monotonic;
180 set_normalized_timespec(&tmp, -wtm->tv_sec, -wtm->tv_nsec);
181 offs_real = timespec_to_ktime(tmp);
184 /* must hold write on xtime_lock */
185 static void timekeeping_update(bool clearntp)
188 timekeeper.ntp_error = 0;
192 update_vsyscall(&xtime, &wall_to_monotonic,
193 timekeeper.clock, timekeeper.mult);
198 /* flag for if timekeeping is suspended */
199 int __read_mostly timekeeping_suspended;
202 * timekeeping_forward_now - update clock to the current time
204 * Forward the current clock to update its state since the last call to
205 * update_wall_time(). This is useful before significant clock changes,
206 * as it avoids having to deal with this time offset explicitly.
208 static void timekeeping_forward_now(void)
210 cycle_t cycle_now, cycle_delta;
211 struct clocksource *clock;
214 clock = timekeeper.clock;
215 cycle_now = clock->read(clock);
216 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
217 clock->cycle_last = cycle_now;
219 nsec = clocksource_cyc2ns(cycle_delta, timekeeper.mult,
222 /* If arch requires, add in gettimeoffset() */
223 nsec += arch_gettimeoffset();
225 timespec_add_ns(&xtime, nsec);
227 nsec = clocksource_cyc2ns(cycle_delta, clock->mult, clock->shift);
228 timespec_add_ns(&raw_time, nsec);
232 * getnstimeofday - Returns the time of day in a timespec
233 * @ts: pointer to the timespec to be set
235 * Returns the time of day in a timespec.
237 void getnstimeofday(struct timespec *ts)
242 WARN_ON(timekeeping_suspended);
245 seq = read_seqbegin(&xtime_lock);
248 nsecs = timekeeping_get_ns();
250 /* If arch requires, add in gettimeoffset() */
251 nsecs += arch_gettimeoffset();
253 } while (read_seqretry(&xtime_lock, seq));
255 timespec_add_ns(ts, nsecs);
258 EXPORT_SYMBOL(getnstimeofday);
260 ktime_t ktime_get(void)
265 WARN_ON(timekeeping_suspended);
268 seq = read_seqbegin(&xtime_lock);
269 secs = xtime.tv_sec + wall_to_monotonic.tv_sec;
270 nsecs = xtime.tv_nsec + 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(&xtime_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(&xtime_lock);
303 tomono = wall_to_monotonic;
304 nsecs = timekeeping_get_ns();
305 /* If arch requires, add in gettimeoffset() */
306 nsecs += arch_gettimeoffset();
308 } while (read_seqretry(&xtime_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(&xtime_lock);
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(&xtime_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 (!timespec_valid(tv))
388 write_seqlock_irqsave(&xtime_lock, flags);
390 timekeeping_forward_now();
392 ts_delta.tv_sec = tv->tv_sec - xtime.tv_sec;
393 ts_delta.tv_nsec = tv->tv_nsec - xtime.tv_nsec;
394 wall_to_monotonic = timespec_sub(wall_to_monotonic, ts_delta);
398 timekeeping_update(true);
400 write_sequnlock_irqrestore(&xtime_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)
423 if ((unsigned long)ts->tv_nsec >= NSEC_PER_SEC)
426 write_seqlock_irqsave(&xtime_lock, flags);
428 timekeeping_forward_now();
430 tmp = timespec_add(xtime, *ts);
431 if (!timespec_valid(&tmp)) {
436 xtime = timespec_add(xtime, *ts);
437 wall_to_monotonic = timespec_sub(wall_to_monotonic, *ts);
439 error: /* even if we error out, we forwarded the time, so call update */
440 timekeeping_update(true);
442 write_sequnlock_irqrestore(&xtime_lock, flags);
444 /* signal hrtimers about time change */
449 EXPORT_SYMBOL(timekeeping_inject_offset);
452 * change_clocksource - Swaps clocksources if a new one is available
454 * Accumulates current time interval and initializes new clocksource
456 static int change_clocksource(void *data)
458 struct clocksource *new, *old;
460 new = (struct clocksource *) data;
462 timekeeping_forward_now();
463 if (!new->enable || new->enable(new) == 0) {
464 old = timekeeper.clock;
465 timekeeper_setup_internals(new);
473 * timekeeping_notify - Install a new clock source
474 * @clock: pointer to the clock source
476 * This function is called from clocksource.c after a new, better clock
477 * source has been registered. The caller holds the clocksource_mutex.
479 void timekeeping_notify(struct clocksource *clock)
481 if (timekeeper.clock == clock)
483 stop_machine(change_clocksource, clock, NULL);
488 * ktime_get_real - get the real (wall-) time in ktime_t format
490 * returns the time in ktime_t format
492 ktime_t ktime_get_real(void)
496 getnstimeofday(&now);
498 return timespec_to_ktime(now);
500 EXPORT_SYMBOL_GPL(ktime_get_real);
503 * getrawmonotonic - Returns the raw monotonic time in a timespec
504 * @ts: pointer to the timespec to be set
506 * Returns the raw monotonic time (completely un-modified by ntp)
508 void getrawmonotonic(struct timespec *ts)
514 seq = read_seqbegin(&xtime_lock);
515 nsecs = timekeeping_get_ns_raw();
518 } while (read_seqretry(&xtime_lock, seq));
520 timespec_add_ns(ts, nsecs);
522 EXPORT_SYMBOL(getrawmonotonic);
526 * timekeeping_valid_for_hres - Check if timekeeping is suitable for hres
528 int timekeeping_valid_for_hres(void)
534 seq = read_seqbegin(&xtime_lock);
536 ret = timekeeper.clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
538 } while (read_seqretry(&xtime_lock, seq));
544 * timekeeping_max_deferment - Returns max time the clocksource can be deferred
546 * Caller must observe xtime_lock via read_seqbegin/read_seqretry to
547 * ensure that the clocksource does not change!
549 u64 timekeeping_max_deferment(void)
551 return timekeeper.clock->max_idle_ns;
555 * read_persistent_clock - Return time from the persistent clock.
557 * Weak dummy function for arches that do not yet support it.
558 * Reads the time from the battery backed persistent clock.
559 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
561 * XXX - Do be sure to remove it once all arches implement it.
563 void __attribute__((weak)) read_persistent_clock(struct timespec *ts)
570 * read_boot_clock - Return time of the system start.
572 * Weak dummy function for arches that do not yet support it.
573 * Function to read the exact time the system has been started.
574 * Returns a timespec with tv_sec=0 and tv_nsec=0 if unsupported.
576 * XXX - Do be sure to remove it once all arches implement it.
578 void __attribute__((weak)) read_boot_clock(struct timespec *ts)
585 * timekeeping_init - Initializes the clocksource and common timekeeping values
587 void __init timekeeping_init(void)
589 struct clocksource *clock;
591 struct timespec now, boot;
593 read_persistent_clock(&now);
594 if (!timespec_valid(&now)) {
595 pr_warn("WARNING: Persistent clock returned invalid value!\n"
596 " Check your CMOS/BIOS settings.\n");
601 read_boot_clock(&boot);
602 if (!timespec_valid(&boot)) {
603 pr_warn("WARNING: Boot clock returned invalid value!\n"
604 " Check your CMOS/BIOS settings.\n");
609 write_seqlock_irqsave(&xtime_lock, flags);
613 clock = clocksource_default_clock();
615 clock->enable(clock);
616 timekeeper_setup_internals(clock);
618 xtime.tv_sec = now.tv_sec;
619 xtime.tv_nsec = now.tv_nsec;
621 raw_time.tv_nsec = 0;
622 if (boot.tv_sec == 0 && boot.tv_nsec == 0) {
623 boot.tv_sec = xtime.tv_sec;
624 boot.tv_nsec = xtime.tv_nsec;
626 set_normalized_timespec(&wall_to_monotonic,
627 -boot.tv_sec, -boot.tv_nsec);
629 total_sleep_time.tv_sec = 0;
630 total_sleep_time.tv_nsec = 0;
631 write_sequnlock_irqrestore(&xtime_lock, flags);
634 /* time in seconds when suspend began */
635 static struct timespec timekeeping_suspend_time;
637 static void update_sleep_time(struct timespec t)
639 total_sleep_time = t;
640 offs_boot = timespec_to_ktime(t);
644 * __timekeeping_inject_sleeptime - Internal function to add sleep interval
645 * @delta: pointer to a timespec delta value
647 * Takes a timespec offset measuring a suspend interval and properly
648 * adds the sleep offset to the timekeeping variables.
650 static void __timekeeping_inject_sleeptime(struct timespec *delta)
652 if (!timespec_valid(delta)) {
653 printk(KERN_WARNING "__timekeeping_inject_sleeptime: Invalid "
654 "sleep delta value!\n");
658 xtime = timespec_add(xtime, *delta);
659 wall_to_monotonic = timespec_sub(wall_to_monotonic, *delta);
660 update_sleep_time(timespec_add(total_sleep_time, *delta));
665 * timekeeping_inject_sleeptime - Adds suspend interval to timeekeeping values
666 * @delta: pointer to a timespec delta value
668 * This hook is for architectures that cannot support read_persistent_clock
669 * because their RTC/persistent clock is only accessible when irqs are enabled.
671 * This function should only be called by rtc_resume(), and allows
672 * a suspend offset to be injected into the timekeeping values.
674 void timekeeping_inject_sleeptime(struct timespec *delta)
679 /* Make sure we don't set the clock twice */
680 read_persistent_clock(&ts);
681 if (!(ts.tv_sec == 0 && ts.tv_nsec == 0))
684 write_seqlock_irqsave(&xtime_lock, flags);
685 timekeeping_forward_now();
687 __timekeeping_inject_sleeptime(delta);
689 timekeeping_update(true);
691 write_sequnlock_irqrestore(&xtime_lock, flags);
693 /* signal hrtimers about time change */
699 * timekeeping_resume - Resumes the generic timekeeping subsystem.
701 * This is for the generic clocksource timekeeping.
702 * xtime/wall_to_monotonic/jiffies/etc are
703 * still managed by arch specific suspend/resume code.
705 static void timekeeping_resume(void)
710 read_persistent_clock(&ts);
712 clocksource_resume();
714 write_seqlock_irqsave(&xtime_lock, flags);
716 if (timespec_compare(&ts, &timekeeping_suspend_time) > 0) {
717 ts = timespec_sub(ts, timekeeping_suspend_time);
718 __timekeeping_inject_sleeptime(&ts);
720 /* re-base the last cycle value */
721 timekeeper.clock->cycle_last = timekeeper.clock->read(timekeeper.clock);
722 timekeeper.ntp_error = 0;
723 timekeeping_suspended = 0;
724 timekeeping_update(false);
725 write_sequnlock_irqrestore(&xtime_lock, flags);
727 touch_softlockup_watchdog();
729 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
731 /* Resume hrtimers */
735 static int timekeeping_suspend(void)
738 struct timespec delta, delta_delta;
739 static struct timespec old_delta;
741 read_persistent_clock(&timekeeping_suspend_time);
743 write_seqlock_irqsave(&xtime_lock, flags);
744 timekeeping_forward_now();
745 timekeeping_suspended = 1;
748 * To avoid drift caused by repeated suspend/resumes,
749 * which each can add ~1 second drift error,
750 * try to compensate so the difference in system time
751 * and persistent_clock time stays close to constant.
753 delta = timespec_sub(xtime, timekeeping_suspend_time);
754 delta_delta = timespec_sub(delta, old_delta);
755 if (abs(delta_delta.tv_sec) >= 2) {
757 * if delta_delta is too large, assume time correction
758 * has occured and set old_delta to the current delta.
762 /* Otherwise try to adjust old_system to compensate */
763 timekeeping_suspend_time =
764 timespec_add(timekeeping_suspend_time, delta_delta);
766 write_sequnlock_irqrestore(&xtime_lock, flags);
768 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
769 clocksource_suspend();
774 /* sysfs resume/suspend bits for timekeeping */
775 static struct syscore_ops timekeeping_syscore_ops = {
776 .resume = timekeeping_resume,
777 .suspend = timekeeping_suspend,
780 static int __init timekeeping_init_ops(void)
782 register_syscore_ops(&timekeeping_syscore_ops);
786 device_initcall(timekeeping_init_ops);
789 * If the error is already larger, we look ahead even further
790 * to compensate for late or lost adjustments.
792 static __always_inline int timekeeping_bigadjust(s64 error, s64 *interval,
800 * Use the current error value to determine how much to look ahead.
801 * The larger the error the slower we adjust for it to avoid problems
802 * with losing too many ticks, otherwise we would overadjust and
803 * produce an even larger error. The smaller the adjustment the
804 * faster we try to adjust for it, as lost ticks can do less harm
805 * here. This is tuned so that an error of about 1 msec is adjusted
806 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
808 error2 = timekeeper.ntp_error >> (NTP_SCALE_SHIFT + 22 - 2 * SHIFT_HZ);
809 error2 = abs(error2);
810 for (look_ahead = 0; error2 > 0; look_ahead++)
814 * Now calculate the error in (1 << look_ahead) ticks, but first
815 * remove the single look ahead already included in the error.
817 tick_error = tick_length >> (timekeeper.ntp_error_shift + 1);
818 tick_error -= timekeeper.xtime_interval >> 1;
819 error = ((error - tick_error) >> look_ahead) + tick_error;
821 /* Finally calculate the adjustment shift value. */
826 *interval = -*interval;
830 for (adj = 0; error > i; adj++)
839 * Adjust the multiplier to reduce the error value,
840 * this is optimized for the most common adjustments of -1,0,1,
841 * for other values we can do a bit more work.
843 static void timekeeping_adjust(s64 offset)
845 s64 error, interval = timekeeper.cycle_interval;
849 * The point of this is to check if the error is greater then half
852 * First we shift it down from NTP_SHIFT to clocksource->shifted nsecs.
854 * Note we subtract one in the shift, so that error is really error*2.
855 * This "saves" dividing(shifting) intererval twice, but keeps the
856 * (error > interval) comparision as still measuring if error is
857 * larger then half an interval.
859 * Note: It does not "save" on aggrivation when reading the code.
861 error = timekeeper.ntp_error >> (timekeeper.ntp_error_shift - 1);
862 if (error > interval) {
864 * We now divide error by 4(via shift), which checks if
865 * the error is greater then twice the interval.
866 * If it is greater, we need a bigadjust, if its smaller,
867 * we can adjust by 1.
871 * XXX - In update_wall_time, we round up to the next
872 * nanosecond, and store the amount rounded up into
873 * the error. This causes the likely below to be unlikely.
875 * The properfix is to avoid rounding up by using
876 * the high precision timekeeper.xtime_nsec instead of
877 * xtime.tv_nsec everywhere. Fixing this will take some
880 if (likely(error <= interval))
883 adj = timekeeping_bigadjust(error, &interval, &offset);
884 } else if (error < -interval) {
885 /* See comment above, this is just switched for the negative */
887 if (likely(error >= -interval)) {
889 interval = -interval;
892 adj = timekeeping_bigadjust(error, &interval, &offset);
893 } else /* No adjustment needed */
896 WARN_ONCE(timekeeper.clock->maxadj &&
897 (timekeeper.mult + adj > timekeeper.clock->mult +
898 timekeeper.clock->maxadj),
899 "Adjusting %s more then 11%% (%ld vs %ld)\n",
900 timekeeper.clock->name, (long)timekeeper.mult + adj,
901 (long)timekeeper.clock->mult +
902 timekeeper.clock->maxadj);
904 * So the following can be confusing.
906 * To keep things simple, lets assume adj == 1 for now.
908 * When adj != 1, remember that the interval and offset values
909 * have been appropriately scaled so the math is the same.
911 * The basic idea here is that we're increasing the multiplier
912 * by one, this causes the xtime_interval to be incremented by
913 * one cycle_interval. This is because:
914 * xtime_interval = cycle_interval * mult
915 * So if mult is being incremented by one:
916 * xtime_interval = cycle_interval * (mult + 1)
918 * xtime_interval = (cycle_interval * mult) + cycle_interval
919 * Which can be shortened to:
920 * xtime_interval += cycle_interval
922 * So offset stores the non-accumulated cycles. Thus the current
923 * time (in shifted nanoseconds) is:
924 * now = (offset * adj) + xtime_nsec
925 * Now, even though we're adjusting the clock frequency, we have
926 * to keep time consistent. In other words, we can't jump back
927 * in time, and we also want to avoid jumping forward in time.
929 * So given the same offset value, we need the time to be the same
930 * both before and after the freq adjustment.
931 * now = (offset * adj_1) + xtime_nsec_1
932 * now = (offset * adj_2) + xtime_nsec_2
934 * (offset * adj_1) + xtime_nsec_1 =
935 * (offset * adj_2) + xtime_nsec_2
939 * (offset * adj_1) + xtime_nsec_1 =
940 * (offset * (adj_1+1)) + xtime_nsec_2
941 * (offset * adj_1) + xtime_nsec_1 =
942 * (offset * adj_1) + offset + xtime_nsec_2
943 * Canceling the sides:
944 * xtime_nsec_1 = offset + xtime_nsec_2
946 * xtime_nsec_2 = xtime_nsec_1 - offset
947 * Which simplfies to:
948 * xtime_nsec -= offset
950 * XXX - TODO: Doc ntp_error calculation.
952 timekeeper.mult += adj;
953 timekeeper.xtime_interval += interval;
954 timekeeper.xtime_nsec -= offset;
955 timekeeper.ntp_error -= (interval - offset) <<
956 timekeeper.ntp_error_shift;
961 * logarithmic_accumulation - shifted accumulation of cycles
963 * This functions accumulates a shifted interval of cycles into
964 * into a shifted interval nanoseconds. Allows for O(log) accumulation
967 * Returns the unconsumed cycles.
969 static cycle_t logarithmic_accumulation(cycle_t offset, int shift)
971 u64 nsecps = (u64)NSEC_PER_SEC << timekeeper.shift;
974 /* If the offset is smaller then a shifted interval, do nothing */
975 if (offset < timekeeper.cycle_interval<<shift)
978 /* Accumulate one shifted interval */
979 offset -= timekeeper.cycle_interval << shift;
980 timekeeper.clock->cycle_last += timekeeper.cycle_interval << shift;
982 timekeeper.xtime_nsec += timekeeper.xtime_interval << shift;
983 while (timekeeper.xtime_nsec >= nsecps) {
985 timekeeper.xtime_nsec -= nsecps;
987 leap = second_overflow(xtime.tv_sec);
988 xtime.tv_sec += leap;
989 wall_to_monotonic.tv_sec -= leap;
991 clock_was_set_delayed();
994 /* Accumulate raw time */
995 raw_nsecs = timekeeper.raw_interval << shift;
996 raw_nsecs += raw_time.tv_nsec;
997 if (raw_nsecs >= NSEC_PER_SEC) {
998 u64 raw_secs = raw_nsecs;
999 raw_nsecs = do_div(raw_secs, NSEC_PER_SEC);
1000 raw_time.tv_sec += raw_secs;
1002 raw_time.tv_nsec = raw_nsecs;
1004 /* Accumulate error between NTP and clock interval */
1005 timekeeper.ntp_error += tick_length << shift;
1006 timekeeper.ntp_error -=
1007 (timekeeper.xtime_interval + timekeeper.xtime_remainder) <<
1008 (timekeeper.ntp_error_shift + shift);
1015 * update_wall_time - Uses the current clocksource to increment the wall time
1017 * Called from the timer interrupt, must hold a write on xtime_lock.
1019 static void update_wall_time(void)
1021 struct clocksource *clock;
1023 int shift = 0, maxshift;
1025 /* Make sure we're fully resumed: */
1026 if (unlikely(timekeeping_suspended))
1029 clock = timekeeper.clock;
1031 #ifdef CONFIG_ARCH_USES_GETTIMEOFFSET
1032 offset = timekeeper.cycle_interval;
1034 offset = (clock->read(clock) - clock->cycle_last) & clock->mask;
1036 /* Check if there's really nothing to do */
1037 if (offset < timekeeper.cycle_interval)
1040 timekeeper.xtime_nsec = (s64)xtime.tv_nsec << timekeeper.shift;
1043 * With NO_HZ we may have to accumulate many cycle_intervals
1044 * (think "ticks") worth of time at once. To do this efficiently,
1045 * we calculate the largest doubling multiple of cycle_intervals
1046 * that is smaller then the offset. We then accumulate that
1047 * chunk in one go, and then try to consume the next smaller
1050 shift = ilog2(offset) - ilog2(timekeeper.cycle_interval);
1051 shift = max(0, shift);
1052 /* Bound shift to one less then what overflows tick_length */
1053 maxshift = (8*sizeof(tick_length) - (ilog2(tick_length)+1)) - 1;
1054 shift = min(shift, maxshift);
1055 while (offset >= timekeeper.cycle_interval) {
1056 offset = logarithmic_accumulation(offset, shift);
1057 if(offset < timekeeper.cycle_interval<<shift)
1061 /* correct the clock when NTP error is too big */
1062 timekeeping_adjust(offset);
1065 * Since in the loop above, we accumulate any amount of time
1066 * in xtime_nsec over a second into xtime.tv_sec, its possible for
1067 * xtime_nsec to be fairly small after the loop. Further, if we're
1068 * slightly speeding the clocksource up in timekeeping_adjust(),
1069 * its possible the required corrective factor to xtime_nsec could
1070 * cause it to underflow.
1072 * Now, we cannot simply roll the accumulated second back, since
1073 * the NTP subsystem has been notified via second_overflow. So
1074 * instead we push xtime_nsec forward by the amount we underflowed,
1075 * and add that amount into the error.
1077 * We'll correct this error next time through this function, when
1078 * xtime_nsec is not as small.
1080 if (unlikely((s64)timekeeper.xtime_nsec < 0)) {
1081 s64 neg = -(s64)timekeeper.xtime_nsec;
1082 timekeeper.xtime_nsec = 0;
1083 timekeeper.ntp_error += neg << timekeeper.ntp_error_shift;
1088 * Store full nanoseconds into xtime after rounding it up and
1089 * add the remainder to the error difference.
1091 xtime.tv_nsec = ((s64) timekeeper.xtime_nsec >> timekeeper.shift) + 1;
1092 timekeeper.xtime_nsec -= (s64) xtime.tv_nsec << timekeeper.shift;
1093 timekeeper.ntp_error += timekeeper.xtime_nsec <<
1094 timekeeper.ntp_error_shift;
1097 * Finally, make sure that after the rounding
1098 * xtime.tv_nsec isn't larger then NSEC_PER_SEC
1100 if (unlikely(xtime.tv_nsec >= NSEC_PER_SEC)) {
1102 xtime.tv_nsec -= NSEC_PER_SEC;
1104 leap = second_overflow(xtime.tv_sec);
1105 xtime.tv_sec += leap;
1106 wall_to_monotonic.tv_sec -= leap;
1108 clock_was_set_delayed();
1111 timekeeping_update(false);
1115 * getboottime - Return the real time of system boot.
1116 * @ts: pointer to the timespec to be set
1118 * Returns the wall-time of boot in a timespec.
1120 * This is based on the wall_to_monotonic offset and the total suspend
1121 * time. Calls to settimeofday will affect the value returned (which
1122 * basically means that however wrong your real time clock is at boot time,
1123 * you get the right time here).
1125 void getboottime(struct timespec *ts)
1127 struct timespec boottime = {
1128 .tv_sec = wall_to_monotonic.tv_sec + total_sleep_time.tv_sec,
1129 .tv_nsec = wall_to_monotonic.tv_nsec + total_sleep_time.tv_nsec
1132 set_normalized_timespec(ts, -boottime.tv_sec, -boottime.tv_nsec);
1134 EXPORT_SYMBOL_GPL(getboottime);
1138 * get_monotonic_boottime - Returns monotonic time since boot
1139 * @ts: pointer to the timespec to be set
1141 * Returns the monotonic time since boot in a timespec.
1143 * This is similar to CLOCK_MONTONIC/ktime_get_ts, but also
1144 * includes the time spent in suspend.
1146 void get_monotonic_boottime(struct timespec *ts)
1148 struct timespec tomono, sleep;
1152 WARN_ON(timekeeping_suspended);
1155 seq = read_seqbegin(&xtime_lock);
1157 tomono = wall_to_monotonic;
1158 sleep = total_sleep_time;
1159 nsecs = timekeeping_get_ns();
1161 } while (read_seqretry(&xtime_lock, seq));
1163 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec + sleep.tv_sec,
1164 ts->tv_nsec + tomono.tv_nsec + sleep.tv_nsec + nsecs);
1166 EXPORT_SYMBOL_GPL(get_monotonic_boottime);
1169 * ktime_get_boottime - Returns monotonic time since boot in a ktime
1171 * Returns the monotonic time since boot in a ktime
1173 * This is similar to CLOCK_MONTONIC/ktime_get, but also
1174 * includes the time spent in suspend.
1176 ktime_t ktime_get_boottime(void)
1180 get_monotonic_boottime(&ts);
1181 return timespec_to_ktime(ts);
1183 EXPORT_SYMBOL_GPL(ktime_get_boottime);
1186 * monotonic_to_bootbased - Convert the monotonic time to boot based.
1187 * @ts: pointer to the timespec to be converted
1189 void monotonic_to_bootbased(struct timespec *ts)
1191 *ts = timespec_add(*ts, total_sleep_time);
1193 EXPORT_SYMBOL_GPL(monotonic_to_bootbased);
1195 unsigned long get_seconds(void)
1197 return xtime.tv_sec;
1199 EXPORT_SYMBOL(get_seconds);
1201 struct timespec __current_kernel_time(void)
1206 struct timespec current_kernel_time(void)
1208 struct timespec now;
1212 seq = read_seqbegin(&xtime_lock);
1215 } while (read_seqretry(&xtime_lock, seq));
1219 EXPORT_SYMBOL(current_kernel_time);
1221 struct timespec get_monotonic_coarse(void)
1223 struct timespec now, mono;
1227 seq = read_seqbegin(&xtime_lock);
1230 mono = wall_to_monotonic;
1231 } while (read_seqretry(&xtime_lock, seq));
1233 set_normalized_timespec(&now, now.tv_sec + mono.tv_sec,
1234 now.tv_nsec + mono.tv_nsec);
1239 * The 64-bit jiffies value is not atomic - you MUST NOT read it
1240 * without sampling the sequence number in xtime_lock.
1241 * jiffies is defined in the linker script...
1243 void do_timer(unsigned long ticks)
1245 jiffies_64 += ticks;
1247 calc_global_load(ticks);
1251 * get_xtime_and_monotonic_and_sleep_offset() - get xtime, wall_to_monotonic,
1252 * and sleep offsets.
1253 * @xtim: pointer to timespec to be set with xtime
1254 * @wtom: pointer to timespec to be set with wall_to_monotonic
1255 * @sleep: pointer to timespec to be set with time in suspend
1257 void get_xtime_and_monotonic_and_sleep_offset(struct timespec *xtim,
1258 struct timespec *wtom, struct timespec *sleep)
1263 seq = read_seqbegin(&xtime_lock);
1265 *wtom = wall_to_monotonic;
1266 *sleep = total_sleep_time;
1267 } while (read_seqretry(&xtime_lock, seq));
1270 #ifdef CONFIG_HIGH_RES_TIMERS
1272 * ktime_get_update_offsets - hrtimer helper
1273 * @real: pointer to storage for monotonic -> realtime offset
1274 * @_boot: pointer to storage for monotonic -> boottime offset
1276 * Returns current monotonic time and updates the offsets
1277 * Called from hrtimer_interupt() or retrigger_next_event()
1279 ktime_t ktime_get_update_offsets(ktime_t *real, ktime_t *boot)
1286 seq = read_seqbegin(&xtime_lock);
1288 secs = xtime.tv_sec;
1289 nsecs = xtime.tv_nsec;
1290 nsecs += timekeeping_get_ns();
1291 /* If arch requires, add in gettimeoffset() */
1292 nsecs += arch_gettimeoffset();
1296 } while (read_seqretry(&xtime_lock, seq));
1298 now = ktime_add_ns(ktime_set(secs, 0), nsecs);
1299 now = ktime_sub(now, *real);
1305 * ktime_get_monotonic_offset() - get wall_to_monotonic in ktime_t format
1307 ktime_t ktime_get_monotonic_offset(void)
1310 struct timespec wtom;
1313 seq = read_seqbegin(&xtime_lock);
1314 wtom = wall_to_monotonic;
1315 } while (read_seqretry(&xtime_lock, seq));
1316 return timespec_to_ktime(wtom);
1320 * xtime_update() - advances the timekeeping infrastructure
1321 * @ticks: number of ticks, that have elapsed since the last call.
1323 * Must be called with interrupts disabled.
1325 void xtime_update(unsigned long ticks)
1327 write_seqlock(&xtime_lock);
1329 write_sequnlock(&xtime_lock);