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 /* USER_HZ period (usecs): */
26 unsigned long tick_usec = TICK_USEC;
28 /* ACTHZ period (nsecs): */
29 unsigned long tick_nsec;
31 static u64 tick_length;
32 static u64 tick_length_base;
34 static struct hrtimer leap_timer;
36 #define MAX_TICKADJ 500LL /* usecs */
37 #define MAX_TICKADJ_SCALED \
38 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
41 * phase-lock loop variables
45 * clock synchronization status
47 * (TIME_ERROR prevents overwriting the CMOS clock)
49 static int time_state = TIME_OK;
51 /* clock status bits: */
52 static int time_status = STA_UNSYNC;
54 /* TAI offset (secs): */
57 /* time adjustment (nsecs): */
58 static s64 time_offset;
60 /* pll time constant: */
61 static long time_constant = 2;
63 /* maximum error (usecs): */
64 static long time_maxerror = NTP_PHASE_LIMIT;
66 /* estimated error (usecs): */
67 static long time_esterror = NTP_PHASE_LIMIT;
69 /* frequency offset (scaled nsecs/secs): */
72 /* time at last adjustment (secs): */
73 static long time_reftime;
75 static long time_adjust;
77 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
78 static s64 ntp_tick_adj;
83 * The following variables are used when a pulse-per-second (PPS) signal
84 * is available. They establish the engineering parameters of the clock
85 * discipline loop when controlled by the PPS signal.
87 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
88 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
89 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
90 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
91 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
92 increase pps_shift or consecutive bad
93 intervals to decrease it */
94 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
96 static int pps_valid; /* signal watchdog counter */
97 static long pps_tf[3]; /* phase median filter */
98 static long pps_jitter; /* current jitter (ns) */
99 static struct timespec pps_fbase; /* beginning of the last freq interval */
100 static int pps_shift; /* current interval duration (s) (shift) */
101 static int pps_intcnt; /* interval counter */
102 static s64 pps_freq; /* frequency offset (scaled ns/s) */
103 static long pps_stabil; /* current stability (scaled ns/s) */
106 * PPS signal quality monitors
108 static long pps_calcnt; /* calibration intervals */
109 static long pps_jitcnt; /* jitter limit exceeded */
110 static long pps_stbcnt; /* stability limit exceeded */
111 static long pps_errcnt; /* calibration errors */
114 /* PPS kernel consumer compensates the whole phase error immediately.
115 * Otherwise, reduce the offset by a fixed factor times the time constant.
117 static inline s64 ntp_offset_chunk(s64 offset)
119 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
122 return shift_right(offset, SHIFT_PLL + time_constant);
125 static inline void pps_reset_freq_interval(void)
127 /* the PPS calibration interval may end
128 surprisingly early */
129 pps_shift = PPS_INTMIN;
134 * pps_clear - Clears the PPS state variables
136 * Must be called while holding a write on the xtime_lock
138 static inline void pps_clear(void)
140 pps_reset_freq_interval();
144 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
148 /* Decrease pps_valid to indicate that another second has passed since
149 * the last PPS signal. When it reaches 0, indicate that PPS signal is
152 * Must be called while holding a write on the xtime_lock
154 static inline void pps_dec_valid(void)
159 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
160 STA_PPSWANDER | STA_PPSERROR);
165 static inline void pps_set_freq(s64 freq)
170 static inline int is_error_status(int status)
172 return (time_status & (STA_UNSYNC|STA_CLOCKERR))
173 /* PPS signal lost when either PPS time or
174 * PPS frequency synchronization requested
176 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
177 && !(time_status & STA_PPSSIGNAL))
178 /* PPS jitter exceeded when
179 * PPS time synchronization requested */
180 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
181 == (STA_PPSTIME|STA_PPSJITTER))
182 /* PPS wander exceeded or calibration error when
183 * PPS frequency synchronization requested
185 || ((time_status & STA_PPSFREQ)
186 && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
189 static inline void pps_fill_timex(struct timex *txc)
191 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
192 PPM_SCALE_INV, NTP_SCALE_SHIFT);
193 txc->jitter = pps_jitter;
194 if (!(time_status & STA_NANO))
195 txc->jitter /= NSEC_PER_USEC;
196 txc->shift = pps_shift;
197 txc->stabil = pps_stabil;
198 txc->jitcnt = pps_jitcnt;
199 txc->calcnt = pps_calcnt;
200 txc->errcnt = pps_errcnt;
201 txc->stbcnt = pps_stbcnt;
204 #else /* !CONFIG_NTP_PPS */
206 static inline s64 ntp_offset_chunk(s64 offset)
208 return shift_right(offset, SHIFT_PLL + time_constant);
211 static inline void pps_reset_freq_interval(void) {}
212 static inline void pps_clear(void) {}
213 static inline void pps_dec_valid(void) {}
214 static inline void pps_set_freq(s64 freq) {}
216 static inline int is_error_status(int status)
218 return status & (STA_UNSYNC|STA_CLOCKERR);
221 static inline void pps_fill_timex(struct timex *txc)
223 /* PPS is not implemented, so these are zero */
234 #endif /* CONFIG_NTP_PPS */
238 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
241 static inline int ntp_synced(void)
243 return !(time_status & STA_UNSYNC);
252 * Update (tick_length, tick_length_base, tick_nsec), based
253 * on (tick_usec, ntp_tick_adj, time_freq):
255 static void ntp_update_frequency(void)
260 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
263 second_length += ntp_tick_adj;
264 second_length += time_freq;
266 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
267 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
270 * Don't wait for the next second_overflow, apply
271 * the change to the tick length immediately:
273 tick_length += new_base - tick_length_base;
274 tick_length_base = new_base;
277 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
279 time_status &= ~STA_MODE;
284 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
287 time_status |= STA_MODE;
289 return div_s64(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
292 static void ntp_update_offset(long offset)
298 if (!(time_status & STA_PLL))
301 if (!(time_status & STA_NANO))
302 offset *= NSEC_PER_USEC;
305 * Scale the phase adjustment and
306 * clamp to the operating range.
308 offset = min(offset, MAXPHASE);
309 offset = max(offset, -MAXPHASE);
312 * Select how the frequency is to be controlled
313 * and in which mode (PLL or FLL).
315 secs = get_seconds() - time_reftime;
316 if (unlikely(time_status & STA_FREQHOLD))
319 time_reftime = get_seconds();
322 freq_adj = ntp_update_offset_fll(offset64, secs);
325 * Clamp update interval to reduce PLL gain with low
326 * sampling rate (e.g. intermittent network connection)
327 * to avoid instability.
329 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
330 secs = 1 << (SHIFT_PLL + 1 + time_constant);
332 freq_adj += (offset64 * secs) <<
333 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
335 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
337 time_freq = max(freq_adj, -MAXFREQ_SCALED);
339 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
343 * ntp_clear - Clears the NTP state variables
345 * Must be called while holding a write on the xtime_lock
349 time_adjust = 0; /* stop active adjtime() */
350 time_status |= STA_UNSYNC;
351 time_maxerror = NTP_PHASE_LIMIT;
352 time_esterror = NTP_PHASE_LIMIT;
354 ntp_update_frequency();
356 tick_length = tick_length_base;
359 /* Clear PPS state variables */
364 u64 ntp_tick_length(void)
371 * Leap second processing. If in leap-insert state at the end of the
372 * day, the system clock is set back one second; if in leap-delete
373 * state, the system clock is set ahead one second.
375 static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
377 enum hrtimer_restart res = HRTIMER_NORESTART;
379 write_seqlock(&xtime_lock);
381 switch (time_state) {
385 timekeeping_leap_insert(-1);
386 time_state = TIME_OOP;
388 "Clock: inserting leap second 23:59:60 UTC\n");
389 hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
390 res = HRTIMER_RESTART;
393 timekeeping_leap_insert(1);
395 time_state = TIME_WAIT;
397 "Clock: deleting leap second 23:59:59 UTC\n");
401 time_state = TIME_WAIT;
404 if (!(time_status & (STA_INS | STA_DEL)))
405 time_state = TIME_OK;
409 write_sequnlock(&xtime_lock);
415 * this routine handles the overflow of the microsecond field
417 * The tricky bits of code to handle the accurate clock support
418 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
419 * They were originally developed for SUN and DEC kernels.
420 * All the kudos should go to Dave for this stuff.
422 void second_overflow(void)
426 /* Bump the maxerror field */
427 time_maxerror += MAXFREQ / NSEC_PER_USEC;
428 if (time_maxerror > NTP_PHASE_LIMIT) {
429 time_maxerror = NTP_PHASE_LIMIT;
430 time_status |= STA_UNSYNC;
433 /* Compute the phase adjustment for the next second */
434 tick_length = tick_length_base;
436 delta = ntp_offset_chunk(time_offset);
437 time_offset -= delta;
438 tick_length += delta;
440 /* Check PPS signal */
446 if (time_adjust > MAX_TICKADJ) {
447 time_adjust -= MAX_TICKADJ;
448 tick_length += MAX_TICKADJ_SCALED;
452 if (time_adjust < -MAX_TICKADJ) {
453 time_adjust += MAX_TICKADJ;
454 tick_length -= MAX_TICKADJ_SCALED;
458 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
463 #ifdef CONFIG_GENERIC_CMOS_UPDATE
465 /* Disable the cmos update - used by virtualization and embedded */
466 int no_sync_cmos_clock __read_mostly;
468 static void sync_cmos_clock(struct work_struct *work);
470 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
472 static void sync_cmos_clock(struct work_struct *work)
474 struct timespec now, next;
478 * If we have an externally synchronized Linux clock, then update
479 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
480 * called as close as possible to 500 ms before the new second starts.
481 * This code is run on a timer. If the clock is set, that timer
482 * may not expire at the correct time. Thus, we adjust...
486 * Not synced, exit, do not restart a timer (if one is
487 * running, let it run out).
492 getnstimeofday(&now);
493 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
494 fail = update_persistent_clock(now);
496 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
497 if (next.tv_nsec <= 0)
498 next.tv_nsec += NSEC_PER_SEC;
505 if (next.tv_nsec >= NSEC_PER_SEC) {
507 next.tv_nsec -= NSEC_PER_SEC;
509 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
512 static void notify_cmos_timer(void)
514 if (!no_sync_cmos_clock)
515 schedule_delayed_work(&sync_cmos_work, 0);
519 static inline void notify_cmos_timer(void) { }
523 * Start the leap seconds timer:
525 static inline void ntp_start_leap_timer(struct timespec *ts)
527 long now = ts->tv_sec;
529 if (time_status & STA_INS) {
530 time_state = TIME_INS;
531 now += 86400 - now % 86400;
532 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
537 if (time_status & STA_DEL) {
538 time_state = TIME_DEL;
539 now += 86400 - (now + 1) % 86400;
540 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
545 * Propagate a new txc->status value into the NTP state:
547 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
549 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
550 time_state = TIME_OK;
551 time_status = STA_UNSYNC;
552 /* restart PPS frequency calibration */
553 pps_reset_freq_interval();
557 * If we turn on PLL adjustments then reset the
558 * reference time to current time.
560 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
561 time_reftime = get_seconds();
563 /* only set allowed bits */
564 time_status &= STA_RONLY;
565 time_status |= txc->status & ~STA_RONLY;
567 switch (time_state) {
569 ntp_start_leap_timer(ts);
573 time_state = TIME_OK;
574 ntp_start_leap_timer(ts);
576 if (!(time_status & (STA_INS | STA_DEL)))
577 time_state = TIME_OK;
580 hrtimer_restart(&leap_timer);
585 * Called with the xtime lock held, so we can access and modify
586 * all the global NTP state:
588 static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
590 if (txc->modes & ADJ_STATUS)
591 process_adj_status(txc, ts);
593 if (txc->modes & ADJ_NANO)
594 time_status |= STA_NANO;
596 if (txc->modes & ADJ_MICRO)
597 time_status &= ~STA_NANO;
599 if (txc->modes & ADJ_FREQUENCY) {
600 time_freq = txc->freq * PPM_SCALE;
601 time_freq = min(time_freq, MAXFREQ_SCALED);
602 time_freq = max(time_freq, -MAXFREQ_SCALED);
603 /* update pps_freq */
604 pps_set_freq(time_freq);
607 if (txc->modes & ADJ_MAXERROR)
608 time_maxerror = txc->maxerror;
610 if (txc->modes & ADJ_ESTERROR)
611 time_esterror = txc->esterror;
613 if (txc->modes & ADJ_TIMECONST) {
614 time_constant = txc->constant;
615 if (!(time_status & STA_NANO))
617 time_constant = min(time_constant, (long)MAXTC);
618 time_constant = max(time_constant, 0l);
621 if (txc->modes & ADJ_TAI && txc->constant > 0)
622 time_tai = txc->constant;
624 if (txc->modes & ADJ_OFFSET)
625 ntp_update_offset(txc->offset);
627 if (txc->modes & ADJ_TICK)
628 tick_usec = txc->tick;
630 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
631 ntp_update_frequency();
635 * adjtimex mainly allows reading (and writing, if superuser) of
636 * kernel time-keeping variables. used by xntpd.
638 int do_adjtimex(struct timex *txc)
643 /* Validate the data before disabling interrupts */
644 if (txc->modes & ADJ_ADJTIME) {
645 /* singleshot must not be used with any other mode bits */
646 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
648 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
649 !capable(CAP_SYS_TIME))
652 /* In order to modify anything, you gotta be super-user! */
653 if (txc->modes && !capable(CAP_SYS_TIME))
657 * if the quartz is off by more than 10% then
658 * something is VERY wrong!
660 if (txc->modes & ADJ_TICK &&
661 (txc->tick < 900000/USER_HZ ||
662 txc->tick > 1100000/USER_HZ))
665 if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
666 hrtimer_cancel(&leap_timer);
669 if (txc->modes & ADJ_SETOFFSET) {
670 struct timespec delta;
671 delta.tv_sec = txc->time.tv_sec;
672 delta.tv_nsec = txc->time.tv_usec;
673 if (!capable(CAP_SYS_TIME))
675 if (!(txc->modes & ADJ_NANO))
676 delta.tv_nsec *= 1000;
677 result = timekeeping_inject_offset(&delta);
684 write_seqlock_irq(&xtime_lock);
686 if (txc->modes & ADJ_ADJTIME) {
687 long save_adjust = time_adjust;
689 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
690 /* adjtime() is independent from ntp_adjtime() */
691 time_adjust = txc->offset;
692 ntp_update_frequency();
694 txc->offset = save_adjust;
697 /* If there are input parameters, then process them: */
699 process_adjtimex_modes(txc, &ts);
701 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
703 if (!(time_status & STA_NANO))
704 txc->offset /= NSEC_PER_USEC;
707 result = time_state; /* mostly `TIME_OK' */
708 /* check for errors */
709 if (is_error_status(time_status))
712 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
713 PPM_SCALE_INV, NTP_SCALE_SHIFT);
714 txc->maxerror = time_maxerror;
715 txc->esterror = time_esterror;
716 txc->status = time_status;
717 txc->constant = time_constant;
719 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
720 txc->tick = tick_usec;
723 /* fill PPS status fields */
726 write_sequnlock_irq(&xtime_lock);
728 txc->time.tv_sec = ts.tv_sec;
729 txc->time.tv_usec = ts.tv_nsec;
730 if (!(time_status & STA_NANO))
731 txc->time.tv_usec /= NSEC_PER_USEC;
738 #ifdef CONFIG_NTP_PPS
740 /* actually struct pps_normtime is good old struct timespec, but it is
741 * semantically different (and it is the reason why it was invented):
742 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
743 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
744 struct pps_normtime {
745 __kernel_time_t sec; /* seconds */
746 long nsec; /* nanoseconds */
749 /* normalize the timestamp so that nsec is in the
750 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
751 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
753 struct pps_normtime norm = {
758 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
759 norm.nsec -= NSEC_PER_SEC;
766 /* get current phase correction and jitter */
767 static inline long pps_phase_filter_get(long *jitter)
769 *jitter = pps_tf[0] - pps_tf[1];
773 /* TODO: test various filters */
777 /* add the sample to the phase filter */
778 static inline void pps_phase_filter_add(long err)
780 pps_tf[2] = pps_tf[1];
781 pps_tf[1] = pps_tf[0];
785 /* decrease frequency calibration interval length.
786 * It is halved after four consecutive unstable intervals.
788 static inline void pps_dec_freq_interval(void)
790 if (--pps_intcnt <= -PPS_INTCOUNT) {
791 pps_intcnt = -PPS_INTCOUNT;
792 if (pps_shift > PPS_INTMIN) {
799 /* increase frequency calibration interval length.
800 * It is doubled after four consecutive stable intervals.
802 static inline void pps_inc_freq_interval(void)
804 if (++pps_intcnt >= PPS_INTCOUNT) {
805 pps_intcnt = PPS_INTCOUNT;
806 if (pps_shift < PPS_INTMAX) {
813 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
816 * At the end of the calibration interval the difference between the
817 * first and last MONOTONIC_RAW clock timestamps divided by the length
818 * of the interval becomes the frequency update. If the interval was
819 * too long, the data are discarded.
820 * Returns the difference between old and new frequency values.
822 static long hardpps_update_freq(struct pps_normtime freq_norm)
824 long delta, delta_mod;
827 /* check if the frequency interval was too long */
828 if (freq_norm.sec > (2 << pps_shift)) {
829 time_status |= STA_PPSERROR;
831 pps_dec_freq_interval();
832 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
837 /* here the raw frequency offset and wander (stability) is
838 * calculated. If the wander is less than the wander threshold
839 * the interval is increased; otherwise it is decreased.
841 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
843 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
845 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
846 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
847 time_status |= STA_PPSWANDER;
849 pps_dec_freq_interval();
850 } else { /* good sample */
851 pps_inc_freq_interval();
854 /* the stability metric is calculated as the average of recent
855 * frequency changes, but is used only for performance
860 delta_mod = -delta_mod;
861 pps_stabil += (div_s64(((s64)delta_mod) <<
862 (NTP_SCALE_SHIFT - SHIFT_USEC),
863 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
865 /* if enabled, the system clock frequency is updated */
866 if ((time_status & STA_PPSFREQ) != 0 &&
867 (time_status & STA_FREQHOLD) == 0) {
868 time_freq = pps_freq;
869 ntp_update_frequency();
875 /* correct REALTIME clock phase error against PPS signal */
876 static void hardpps_update_phase(long error)
878 long correction = -error;
881 /* add the sample to the median filter */
882 pps_phase_filter_add(correction);
883 correction = pps_phase_filter_get(&jitter);
885 /* Nominal jitter is due to PPS signal noise. If it exceeds the
886 * threshold, the sample is discarded; otherwise, if so enabled,
887 * the time offset is updated.
889 if (jitter > (pps_jitter << PPS_POPCORN)) {
890 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
891 jitter, (pps_jitter << PPS_POPCORN));
892 time_status |= STA_PPSJITTER;
894 } else if (time_status & STA_PPSTIME) {
895 /* correct the time using the phase offset */
896 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
898 /* cancel running adjtime() */
902 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
906 * hardpps() - discipline CPU clock oscillator to external PPS signal
908 * This routine is called at each PPS signal arrival in order to
909 * discipline the CPU clock oscillator to the PPS signal. It takes two
910 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
911 * is used to correct clock phase error and the latter is used to
912 * correct the frequency.
914 * This code is based on David Mills's reference nanokernel
915 * implementation. It was mostly rewritten but keeps the same idea.
917 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
919 struct pps_normtime pts_norm, freq_norm;
922 pts_norm = pps_normalize_ts(*phase_ts);
924 write_seqlock_irqsave(&xtime_lock, flags);
926 /* clear the error bits, they will be set again if needed */
927 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
929 /* indicate signal presence */
930 time_status |= STA_PPSSIGNAL;
931 pps_valid = PPS_VALID;
933 /* when called for the first time,
934 * just start the frequency interval */
935 if (unlikely(pps_fbase.tv_sec == 0)) {
937 write_sequnlock_irqrestore(&xtime_lock, flags);
941 /* ok, now we have a base for frequency calculation */
942 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
944 /* check that the signal is in the range
945 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
946 if ((freq_norm.sec == 0) ||
947 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
948 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
949 time_status |= STA_PPSJITTER;
950 /* restart the frequency calibration interval */
952 write_sequnlock_irqrestore(&xtime_lock, flags);
953 pr_err("hardpps: PPSJITTER: bad pulse\n");
959 /* check if the current frequency interval is finished */
960 if (freq_norm.sec >= (1 << pps_shift)) {
962 /* restart the frequency calibration interval */
964 hardpps_update_freq(freq_norm);
967 hardpps_update_phase(pts_norm.nsec);
969 write_sequnlock_irqrestore(&xtime_lock, flags);
971 EXPORT_SYMBOL(hardpps);
973 #endif /* CONFIG_NTP_PPS */
975 static int __init ntp_tick_adj_setup(char *str)
977 ntp_tick_adj = simple_strtol(str, NULL, 0);
978 ntp_tick_adj <<= NTP_SCALE_SHIFT;
983 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
985 void __init ntp_init(void)
988 hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
989 leap_timer.function = ntp_leap_second;