2 * NTP state machine interfaces and logic.
4 * This code was mainly moved from kernel/timer.c and kernel/time.c
5 * Please see those files for relevant copyright info and historical
8 #include <linux/capability.h>
9 #include <linux/clocksource.h>
10 #include <linux/workqueue.h>
11 #include <linux/hrtimer.h>
12 #include <linux/jiffies.h>
13 #include <linux/math64.h>
14 #include <linux/timex.h>
15 #include <linux/time.h>
17 #include <linux/module.h>
19 #include "tick-internal.h"
22 * NTP timekeeping variables:
25 DEFINE_SPINLOCK(ntp_lock);
28 /* USER_HZ period (usecs): */
29 unsigned long tick_usec = TICK_USEC;
31 /* ACTHZ period (nsecs): */
32 unsigned long tick_nsec;
34 static u64 tick_length;
35 static u64 tick_length_base;
37 static struct hrtimer leap_timer;
39 #define MAX_TICKADJ 500LL /* usecs */
40 #define MAX_TICKADJ_SCALED \
41 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
44 * phase-lock loop variables
48 * clock synchronization status
50 * (TIME_ERROR prevents overwriting the CMOS clock)
52 static int time_state = TIME_OK;
54 /* clock status bits: */
55 static int time_status = STA_UNSYNC;
57 /* TAI offset (secs): */
60 /* time adjustment (nsecs): */
61 static s64 time_offset;
63 /* pll time constant: */
64 static long time_constant = 2;
66 /* maximum error (usecs): */
67 static long time_maxerror = NTP_PHASE_LIMIT;
69 /* estimated error (usecs): */
70 static long time_esterror = NTP_PHASE_LIMIT;
72 /* frequency offset (scaled nsecs/secs): */
75 /* time at last adjustment (secs): */
76 static long time_reftime;
78 static long time_adjust;
80 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
81 static s64 ntp_tick_adj;
86 * The following variables are used when a pulse-per-second (PPS) signal
87 * is available. They establish the engineering parameters of the clock
88 * discipline loop when controlled by the PPS signal.
90 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
91 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
92 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
93 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
94 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
95 increase pps_shift or consecutive bad
96 intervals to decrease it */
97 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
99 static int pps_valid; /* signal watchdog counter */
100 static long pps_tf[3]; /* phase median filter */
101 static long pps_jitter; /* current jitter (ns) */
102 static struct timespec pps_fbase; /* beginning of the last freq interval */
103 static int pps_shift; /* current interval duration (s) (shift) */
104 static int pps_intcnt; /* interval counter */
105 static s64 pps_freq; /* frequency offset (scaled ns/s) */
106 static long pps_stabil; /* current stability (scaled ns/s) */
109 * PPS signal quality monitors
111 static long pps_calcnt; /* calibration intervals */
112 static long pps_jitcnt; /* jitter limit exceeded */
113 static long pps_stbcnt; /* stability limit exceeded */
114 static long pps_errcnt; /* calibration errors */
117 /* PPS kernel consumer compensates the whole phase error immediately.
118 * Otherwise, reduce the offset by a fixed factor times the time constant.
120 static inline s64 ntp_offset_chunk(s64 offset)
122 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
125 return shift_right(offset, SHIFT_PLL + time_constant);
128 static inline void pps_reset_freq_interval(void)
130 /* the PPS calibration interval may end
131 surprisingly early */
132 pps_shift = PPS_INTMIN;
137 * pps_clear - Clears the PPS state variables
139 * Must be called while holding a write on the ntp_lock
141 static inline void pps_clear(void)
143 pps_reset_freq_interval();
147 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
151 /* Decrease pps_valid to indicate that another second has passed since
152 * the last PPS signal. When it reaches 0, indicate that PPS signal is
155 * Must be called while holding a write on the ntp_lock
157 static inline void pps_dec_valid(void)
162 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
163 STA_PPSWANDER | STA_PPSERROR);
168 static inline void pps_set_freq(s64 freq)
173 static inline int is_error_status(int status)
175 return (time_status & (STA_UNSYNC|STA_CLOCKERR))
176 /* PPS signal lost when either PPS time or
177 * PPS frequency synchronization requested
179 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
180 && !(time_status & STA_PPSSIGNAL))
181 /* PPS jitter exceeded when
182 * PPS time synchronization requested */
183 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
184 == (STA_PPSTIME|STA_PPSJITTER))
185 /* PPS wander exceeded or calibration error when
186 * PPS frequency synchronization requested
188 || ((time_status & STA_PPSFREQ)
189 && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
192 static inline void pps_fill_timex(struct timex *txc)
194 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
195 PPM_SCALE_INV, NTP_SCALE_SHIFT);
196 txc->jitter = pps_jitter;
197 if (!(time_status & STA_NANO))
198 txc->jitter /= NSEC_PER_USEC;
199 txc->shift = pps_shift;
200 txc->stabil = pps_stabil;
201 txc->jitcnt = pps_jitcnt;
202 txc->calcnt = pps_calcnt;
203 txc->errcnt = pps_errcnt;
204 txc->stbcnt = pps_stbcnt;
207 #else /* !CONFIG_NTP_PPS */
209 static inline s64 ntp_offset_chunk(s64 offset)
211 return shift_right(offset, SHIFT_PLL + time_constant);
214 static inline void pps_reset_freq_interval(void) {}
215 static inline void pps_clear(void) {}
216 static inline void pps_dec_valid(void) {}
217 static inline void pps_set_freq(s64 freq) {}
219 static inline int is_error_status(int status)
221 return status & (STA_UNSYNC|STA_CLOCKERR);
224 static inline void pps_fill_timex(struct timex *txc)
226 /* PPS is not implemented, so these are zero */
237 #endif /* CONFIG_NTP_PPS */
241 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
244 static inline int ntp_synced(void)
246 return !(time_status & STA_UNSYNC);
255 * Update (tick_length, tick_length_base, tick_nsec), based
256 * on (tick_usec, ntp_tick_adj, time_freq):
258 static void ntp_update_frequency(void)
263 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
266 second_length += ntp_tick_adj;
267 second_length += time_freq;
269 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
270 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
273 * Don't wait for the next second_overflow, apply
274 * the change to the tick length immediately:
276 tick_length += new_base - tick_length_base;
277 tick_length_base = new_base;
280 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
282 time_status &= ~STA_MODE;
287 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
290 time_status |= STA_MODE;
292 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
295 static void ntp_update_offset(long offset)
301 if (!(time_status & STA_PLL))
304 if (!(time_status & STA_NANO))
305 offset *= NSEC_PER_USEC;
308 * Scale the phase adjustment and
309 * clamp to the operating range.
311 offset = min(offset, MAXPHASE);
312 offset = max(offset, -MAXPHASE);
315 * Select how the frequency is to be controlled
316 * and in which mode (PLL or FLL).
318 secs = get_seconds() - time_reftime;
319 if (unlikely(time_status & STA_FREQHOLD))
322 time_reftime = get_seconds();
325 freq_adj = ntp_update_offset_fll(offset64, secs);
328 * Clamp update interval to reduce PLL gain with low
329 * sampling rate (e.g. intermittent network connection)
330 * to avoid instability.
332 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
333 secs = 1 << (SHIFT_PLL + 1 + time_constant);
335 freq_adj += (offset64 * secs) <<
336 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
338 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
340 time_freq = max(freq_adj, -MAXFREQ_SCALED);
342 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
346 * ntp_clear - Clears the NTP state variables
352 spin_lock_irqsave(&ntp_lock, flags);
354 time_adjust = 0; /* stop active adjtime() */
355 time_status |= STA_UNSYNC;
356 time_maxerror = NTP_PHASE_LIMIT;
357 time_esterror = NTP_PHASE_LIMIT;
359 ntp_update_frequency();
361 tick_length = tick_length_base;
364 /* Clear PPS state variables */
366 spin_unlock_irqrestore(&ntp_lock, flags);
371 u64 ntp_tick_length(void)
376 spin_lock_irqsave(&ntp_lock, flags);
378 spin_unlock_irqrestore(&ntp_lock, flags);
384 * Leap second processing. If in leap-insert state at the end of the
385 * day, the system clock is set back one second; if in leap-delete
386 * state, the system clock is set ahead one second.
388 static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
390 enum hrtimer_restart res = HRTIMER_NORESTART;
394 spin_lock_irqsave(&ntp_lock, flags);
395 switch (time_state) {
400 time_state = TIME_OOP;
402 "Clock: inserting leap second 23:59:60 UTC\n");
403 hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
404 res = HRTIMER_RESTART;
409 time_state = TIME_WAIT;
411 "Clock: deleting leap second 23:59:59 UTC\n");
415 time_state = TIME_WAIT;
418 if (!(time_status & (STA_INS | STA_DEL)))
419 time_state = TIME_OK;
422 spin_unlock_irqrestore(&ntp_lock, flags);
425 * We have to call this outside of the ntp_lock to keep
426 * the proper locking hierarchy
429 timekeeping_leap_insert(leap);
435 * this routine handles the overflow of the microsecond field
437 * The tricky bits of code to handle the accurate clock support
438 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
439 * They were originally developed for SUN and DEC kernels.
440 * All the kudos should go to Dave for this stuff.
442 void second_overflow(void)
447 spin_lock_irqsave(&ntp_lock, flags);
449 /* Bump the maxerror field */
450 time_maxerror += MAXFREQ / NSEC_PER_USEC;
451 if (time_maxerror > NTP_PHASE_LIMIT) {
452 time_maxerror = NTP_PHASE_LIMIT;
453 time_status |= STA_UNSYNC;
456 /* Compute the phase adjustment for the next second */
457 tick_length = tick_length_base;
459 delta = ntp_offset_chunk(time_offset);
460 time_offset -= delta;
461 tick_length += delta;
463 /* Check PPS signal */
469 if (time_adjust > MAX_TICKADJ) {
470 time_adjust -= MAX_TICKADJ;
471 tick_length += MAX_TICKADJ_SCALED;
475 if (time_adjust < -MAX_TICKADJ) {
476 time_adjust += MAX_TICKADJ;
477 tick_length -= MAX_TICKADJ_SCALED;
481 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
485 spin_unlock_irqrestore(&ntp_lock, flags);
488 #ifdef CONFIG_GENERIC_CMOS_UPDATE
490 /* Disable the cmos update - used by virtualization and embedded */
491 int no_sync_cmos_clock __read_mostly;
493 static void sync_cmos_clock(struct work_struct *work);
495 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
497 static void sync_cmos_clock(struct work_struct *work)
499 struct timespec now, next;
503 * If we have an externally synchronized Linux clock, then update
504 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
505 * called as close as possible to 500 ms before the new second starts.
506 * This code is run on a timer. If the clock is set, that timer
507 * may not expire at the correct time. Thus, we adjust...
511 * Not synced, exit, do not restart a timer (if one is
512 * running, let it run out).
517 getnstimeofday(&now);
518 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
519 fail = update_persistent_clock(now);
521 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
522 if (next.tv_nsec <= 0)
523 next.tv_nsec += NSEC_PER_SEC;
530 if (next.tv_nsec >= NSEC_PER_SEC) {
532 next.tv_nsec -= NSEC_PER_SEC;
534 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
537 static void notify_cmos_timer(void)
539 if (!no_sync_cmos_clock)
540 schedule_delayed_work(&sync_cmos_work, 0);
544 static inline void notify_cmos_timer(void) { }
548 * Start the leap seconds timer:
550 static inline void ntp_start_leap_timer(struct timespec *ts)
552 long now = ts->tv_sec;
554 if (time_status & STA_INS) {
555 time_state = TIME_INS;
556 now += 86400 - now % 86400;
557 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
562 if (time_status & STA_DEL) {
563 time_state = TIME_DEL;
564 now += 86400 - (now + 1) % 86400;
565 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
570 * Propagate a new txc->status value into the NTP state:
572 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
574 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
575 time_state = TIME_OK;
576 time_status = STA_UNSYNC;
577 /* restart PPS frequency calibration */
578 pps_reset_freq_interval();
582 * If we turn on PLL adjustments then reset the
583 * reference time to current time.
585 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
586 time_reftime = get_seconds();
588 /* only set allowed bits */
589 time_status &= STA_RONLY;
590 time_status |= txc->status & ~STA_RONLY;
592 switch (time_state) {
594 ntp_start_leap_timer(ts);
598 time_state = TIME_OK;
599 ntp_start_leap_timer(ts);
601 if (!(time_status & (STA_INS | STA_DEL)))
602 time_state = TIME_OK;
605 hrtimer_restart(&leap_timer);
610 * Called with the xtime lock held, so we can access and modify
611 * all the global NTP state:
613 static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
615 if (txc->modes & ADJ_STATUS)
616 process_adj_status(txc, ts);
618 if (txc->modes & ADJ_NANO)
619 time_status |= STA_NANO;
621 if (txc->modes & ADJ_MICRO)
622 time_status &= ~STA_NANO;
624 if (txc->modes & ADJ_FREQUENCY) {
625 time_freq = txc->freq * PPM_SCALE;
626 time_freq = min(time_freq, MAXFREQ_SCALED);
627 time_freq = max(time_freq, -MAXFREQ_SCALED);
628 /* update pps_freq */
629 pps_set_freq(time_freq);
632 if (txc->modes & ADJ_MAXERROR)
633 time_maxerror = txc->maxerror;
635 if (txc->modes & ADJ_ESTERROR)
636 time_esterror = txc->esterror;
638 if (txc->modes & ADJ_TIMECONST) {
639 time_constant = txc->constant;
640 if (!(time_status & STA_NANO))
642 time_constant = min(time_constant, (long)MAXTC);
643 time_constant = max(time_constant, 0l);
646 if (txc->modes & ADJ_TAI && txc->constant > 0)
647 time_tai = txc->constant;
649 if (txc->modes & ADJ_OFFSET)
650 ntp_update_offset(txc->offset);
652 if (txc->modes & ADJ_TICK)
653 tick_usec = txc->tick;
655 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
656 ntp_update_frequency();
660 * adjtimex mainly allows reading (and writing, if superuser) of
661 * kernel time-keeping variables. used by xntpd.
663 int do_adjtimex(struct timex *txc)
668 /* Validate the data before disabling interrupts */
669 if (txc->modes & ADJ_ADJTIME) {
670 /* singleshot must not be used with any other mode bits */
671 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
673 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
674 !capable(CAP_SYS_TIME))
677 /* In order to modify anything, you gotta be super-user! */
678 if (txc->modes && !capable(CAP_SYS_TIME))
682 * if the quartz is off by more than 10% then
683 * something is VERY wrong!
685 if (txc->modes & ADJ_TICK &&
686 (txc->tick < 900000/USER_HZ ||
687 txc->tick > 1100000/USER_HZ))
690 if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
691 hrtimer_cancel(&leap_timer);
694 if (txc->modes & ADJ_SETOFFSET) {
695 struct timespec delta;
696 delta.tv_sec = txc->time.tv_sec;
697 delta.tv_nsec = txc->time.tv_usec;
698 if (!capable(CAP_SYS_TIME))
700 if (!(txc->modes & ADJ_NANO))
701 delta.tv_nsec *= 1000;
702 result = timekeeping_inject_offset(&delta);
709 spin_lock_irq(&ntp_lock);
711 if (txc->modes & ADJ_ADJTIME) {
712 long save_adjust = time_adjust;
714 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
715 /* adjtime() is independent from ntp_adjtime() */
716 time_adjust = txc->offset;
717 ntp_update_frequency();
719 txc->offset = save_adjust;
722 /* If there are input parameters, then process them: */
724 process_adjtimex_modes(txc, &ts);
726 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
728 if (!(time_status & STA_NANO))
729 txc->offset /= NSEC_PER_USEC;
732 result = time_state; /* mostly `TIME_OK' */
733 /* check for errors */
734 if (is_error_status(time_status))
737 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
738 PPM_SCALE_INV, NTP_SCALE_SHIFT);
739 txc->maxerror = time_maxerror;
740 txc->esterror = time_esterror;
741 txc->status = time_status;
742 txc->constant = time_constant;
744 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
745 txc->tick = tick_usec;
748 /* fill PPS status fields */
751 spin_unlock_irq(&ntp_lock);
753 txc->time.tv_sec = ts.tv_sec;
754 txc->time.tv_usec = ts.tv_nsec;
755 if (!(time_status & STA_NANO))
756 txc->time.tv_usec /= NSEC_PER_USEC;
763 #ifdef CONFIG_NTP_PPS
765 /* actually struct pps_normtime is good old struct timespec, but it is
766 * semantically different (and it is the reason why it was invented):
767 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
768 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
769 struct pps_normtime {
770 __kernel_time_t sec; /* seconds */
771 long nsec; /* nanoseconds */
774 /* normalize the timestamp so that nsec is in the
775 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
776 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
778 struct pps_normtime norm = {
783 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
784 norm.nsec -= NSEC_PER_SEC;
791 /* get current phase correction and jitter */
792 static inline long pps_phase_filter_get(long *jitter)
794 *jitter = pps_tf[0] - pps_tf[1];
798 /* TODO: test various filters */
802 /* add the sample to the phase filter */
803 static inline void pps_phase_filter_add(long err)
805 pps_tf[2] = pps_tf[1];
806 pps_tf[1] = pps_tf[0];
810 /* decrease frequency calibration interval length.
811 * It is halved after four consecutive unstable intervals.
813 static inline void pps_dec_freq_interval(void)
815 if (--pps_intcnt <= -PPS_INTCOUNT) {
816 pps_intcnt = -PPS_INTCOUNT;
817 if (pps_shift > PPS_INTMIN) {
824 /* increase frequency calibration interval length.
825 * It is doubled after four consecutive stable intervals.
827 static inline void pps_inc_freq_interval(void)
829 if (++pps_intcnt >= PPS_INTCOUNT) {
830 pps_intcnt = PPS_INTCOUNT;
831 if (pps_shift < PPS_INTMAX) {
838 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
841 * At the end of the calibration interval the difference between the
842 * first and last MONOTONIC_RAW clock timestamps divided by the length
843 * of the interval becomes the frequency update. If the interval was
844 * too long, the data are discarded.
845 * Returns the difference between old and new frequency values.
847 static long hardpps_update_freq(struct pps_normtime freq_norm)
849 long delta, delta_mod;
852 /* check if the frequency interval was too long */
853 if (freq_norm.sec > (2 << pps_shift)) {
854 time_status |= STA_PPSERROR;
856 pps_dec_freq_interval();
857 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
862 /* here the raw frequency offset and wander (stability) is
863 * calculated. If the wander is less than the wander threshold
864 * the interval is increased; otherwise it is decreased.
866 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
868 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
870 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
871 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
872 time_status |= STA_PPSWANDER;
874 pps_dec_freq_interval();
875 } else { /* good sample */
876 pps_inc_freq_interval();
879 /* the stability metric is calculated as the average of recent
880 * frequency changes, but is used only for performance
885 delta_mod = -delta_mod;
886 pps_stabil += (div_s64(((s64)delta_mod) <<
887 (NTP_SCALE_SHIFT - SHIFT_USEC),
888 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
890 /* if enabled, the system clock frequency is updated */
891 if ((time_status & STA_PPSFREQ) != 0 &&
892 (time_status & STA_FREQHOLD) == 0) {
893 time_freq = pps_freq;
894 ntp_update_frequency();
900 /* correct REALTIME clock phase error against PPS signal */
901 static void hardpps_update_phase(long error)
903 long correction = -error;
906 /* add the sample to the median filter */
907 pps_phase_filter_add(correction);
908 correction = pps_phase_filter_get(&jitter);
910 /* Nominal jitter is due to PPS signal noise. If it exceeds the
911 * threshold, the sample is discarded; otherwise, if so enabled,
912 * the time offset is updated.
914 if (jitter > (pps_jitter << PPS_POPCORN)) {
915 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
916 jitter, (pps_jitter << PPS_POPCORN));
917 time_status |= STA_PPSJITTER;
919 } else if (time_status & STA_PPSTIME) {
920 /* correct the time using the phase offset */
921 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
923 /* cancel running adjtime() */
927 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
931 * hardpps() - discipline CPU clock oscillator to external PPS signal
933 * This routine is called at each PPS signal arrival in order to
934 * discipline the CPU clock oscillator to the PPS signal. It takes two
935 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
936 * is used to correct clock phase error and the latter is used to
937 * correct the frequency.
939 * This code is based on David Mills's reference nanokernel
940 * implementation. It was mostly rewritten but keeps the same idea.
942 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
944 struct pps_normtime pts_norm, freq_norm;
947 pts_norm = pps_normalize_ts(*phase_ts);
949 spin_lock_irqsave(&ntp_lock, flags);
951 /* clear the error bits, they will be set again if needed */
952 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
954 /* indicate signal presence */
955 time_status |= STA_PPSSIGNAL;
956 pps_valid = PPS_VALID;
958 /* when called for the first time,
959 * just start the frequency interval */
960 if (unlikely(pps_fbase.tv_sec == 0)) {
962 spin_unlock_irqrestore(&ntp_lock, flags);
966 /* ok, now we have a base for frequency calculation */
967 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
969 /* check that the signal is in the range
970 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
971 if ((freq_norm.sec == 0) ||
972 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
973 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
974 time_status |= STA_PPSJITTER;
975 /* restart the frequency calibration interval */
977 spin_unlock_irqrestore(&ntp_lock, flags);
978 pr_err("hardpps: PPSJITTER: bad pulse\n");
984 /* check if the current frequency interval is finished */
985 if (freq_norm.sec >= (1 << pps_shift)) {
987 /* restart the frequency calibration interval */
989 hardpps_update_freq(freq_norm);
992 hardpps_update_phase(pts_norm.nsec);
994 spin_unlock_irqrestore(&ntp_lock, flags);
996 EXPORT_SYMBOL(hardpps);
998 #endif /* CONFIG_NTP_PPS */
1000 static int __init ntp_tick_adj_setup(char *str)
1002 ntp_tick_adj = simple_strtol(str, NULL, 0);
1003 ntp_tick_adj <<= NTP_SCALE_SHIFT;
1008 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1010 void __init ntp_init(void)
1013 hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
1014 leap_timer.function = ntp_leap_second;