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;
32 static u64 tick_length_base;
34 #define MAX_TICKADJ 500LL /* usecs */
35 #define MAX_TICKADJ_SCALED \
36 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
39 * phase-lock loop variables
43 * clock synchronization status
45 * (TIME_ERROR prevents overwriting the CMOS clock)
47 static int time_state = TIME_OK;
49 /* clock status bits: */
50 int time_status = STA_UNSYNC;
52 /* TAI offset (secs): */
55 /* time adjustment (nsecs): */
56 static s64 time_offset;
58 /* pll time constant: */
59 static long time_constant = 2;
61 /* maximum error (usecs): */
62 static long time_maxerror = NTP_PHASE_LIMIT;
64 /* estimated error (usecs): */
65 static long time_esterror = NTP_PHASE_LIMIT;
67 /* frequency offset (scaled nsecs/secs): */
70 /* time at last adjustment (secs): */
71 static long time_reftime;
73 static long time_adjust;
75 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
76 static s64 ntp_tick_adj;
81 * The following variables are used when a pulse-per-second (PPS) signal
82 * is available. They establish the engineering parameters of the clock
83 * discipline loop when controlled by the PPS signal.
85 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
86 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
87 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
88 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
89 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
90 increase pps_shift or consecutive bad
91 intervals to decrease it */
92 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
94 static int pps_valid; /* signal watchdog counter */
95 static long pps_tf[3]; /* phase median filter */
96 static long pps_jitter; /* current jitter (ns) */
97 static struct timespec pps_fbase; /* beginning of the last freq interval */
98 static int pps_shift; /* current interval duration (s) (shift) */
99 static int pps_intcnt; /* interval counter */
100 static s64 pps_freq; /* frequency offset (scaled ns/s) */
101 static long pps_stabil; /* current stability (scaled ns/s) */
104 * PPS signal quality monitors
106 static long pps_calcnt; /* calibration intervals */
107 static long pps_jitcnt; /* jitter limit exceeded */
108 static long pps_stbcnt; /* stability limit exceeded */
109 static long pps_errcnt; /* calibration errors */
112 /* PPS kernel consumer compensates the whole phase error immediately.
113 * Otherwise, reduce the offset by a fixed factor times the time constant.
115 static inline s64 ntp_offset_chunk(s64 offset)
117 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
120 return shift_right(offset, SHIFT_PLL + time_constant);
123 static inline void pps_reset_freq_interval(void)
125 /* the PPS calibration interval may end
126 surprisingly early */
127 pps_shift = PPS_INTMIN;
132 * pps_clear - Clears the PPS state variables
134 * Must be called while holding a write on the xtime_lock
136 static inline void pps_clear(void)
138 pps_reset_freq_interval();
142 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
146 /* Decrease pps_valid to indicate that another second has passed since
147 * the last PPS signal. When it reaches 0, indicate that PPS signal is
150 * Must be called while holding a write on the xtime_lock
152 static inline void pps_dec_valid(void)
157 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
158 STA_PPSWANDER | STA_PPSERROR);
163 static inline void pps_set_freq(s64 freq)
168 static inline int is_error_status(int status)
170 return (time_status & (STA_UNSYNC|STA_CLOCKERR))
171 /* PPS signal lost when either PPS time or
172 * PPS frequency synchronization requested
174 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
175 && !(time_status & STA_PPSSIGNAL))
176 /* PPS jitter exceeded when
177 * PPS time synchronization requested */
178 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
179 == (STA_PPSTIME|STA_PPSJITTER))
180 /* PPS wander exceeded or calibration error when
181 * PPS frequency synchronization requested
183 || ((time_status & STA_PPSFREQ)
184 && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
187 static inline void pps_fill_timex(struct timex *txc)
189 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
190 PPM_SCALE_INV, NTP_SCALE_SHIFT);
191 txc->jitter = pps_jitter;
192 if (!(time_status & STA_NANO))
193 txc->jitter /= NSEC_PER_USEC;
194 txc->shift = pps_shift;
195 txc->stabil = pps_stabil;
196 txc->jitcnt = pps_jitcnt;
197 txc->calcnt = pps_calcnt;
198 txc->errcnt = pps_errcnt;
199 txc->stbcnt = pps_stbcnt;
202 #else /* !CONFIG_NTP_PPS */
204 static inline s64 ntp_offset_chunk(s64 offset)
206 return shift_right(offset, SHIFT_PLL + time_constant);
209 static inline void pps_reset_freq_interval(void) {}
210 static inline void pps_clear(void) {}
211 static inline void pps_dec_valid(void) {}
212 static inline void pps_set_freq(s64 freq) {}
214 static inline int is_error_status(int status)
216 return status & (STA_UNSYNC|STA_CLOCKERR);
219 static inline void pps_fill_timex(struct timex *txc)
221 /* PPS is not implemented, so these are zero */
232 #endif /* CONFIG_NTP_PPS */
239 * Update (tick_length, tick_length_base, tick_nsec), based
240 * on (tick_usec, ntp_tick_adj, time_freq):
242 static void ntp_update_frequency(void)
247 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
250 second_length += ntp_tick_adj;
251 second_length += time_freq;
253 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
254 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
257 * Don't wait for the next second_overflow, apply
258 * the change to the tick length immediately:
260 tick_length += new_base - tick_length_base;
261 tick_length_base = new_base;
264 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
266 time_status &= ~STA_MODE;
271 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
274 time_status |= STA_MODE;
276 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
279 static void ntp_update_offset(long offset)
285 if (!(time_status & STA_PLL))
288 if (!(time_status & STA_NANO))
289 offset *= NSEC_PER_USEC;
292 * Scale the phase adjustment and
293 * clamp to the operating range.
295 offset = min(offset, MAXPHASE);
296 offset = max(offset, -MAXPHASE);
299 * Select how the frequency is to be controlled
300 * and in which mode (PLL or FLL).
302 secs = get_seconds() - time_reftime;
303 if (unlikely(time_status & STA_FREQHOLD))
306 time_reftime = get_seconds();
309 freq_adj = ntp_update_offset_fll(offset64, secs);
312 * Clamp update interval to reduce PLL gain with low
313 * sampling rate (e.g. intermittent network connection)
314 * to avoid instability.
316 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
317 secs = 1 << (SHIFT_PLL + 1 + time_constant);
319 freq_adj += (offset64 * secs) <<
320 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
322 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
324 time_freq = max(freq_adj, -MAXFREQ_SCALED);
326 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
330 * ntp_clear - Clears the NTP state variables
332 * Must be called while holding a write on the xtime_lock
336 time_adjust = 0; /* stop active adjtime() */
337 time_status |= STA_UNSYNC;
338 time_maxerror = NTP_PHASE_LIMIT;
339 time_esterror = NTP_PHASE_LIMIT;
341 ntp_update_frequency();
343 tick_length = tick_length_base;
346 /* Clear PPS state variables */
351 * this routine handles the overflow of the microsecond field
353 * The tricky bits of code to handle the accurate clock support
354 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
355 * They were originally developed for SUN and DEC kernels.
356 * All the kudos should go to Dave for this stuff.
358 * Also handles leap second processing, and returns leap offset
360 int second_overflow(unsigned long secs)
366 * Leap second processing. If in leap-insert state at the end of the
367 * day, the system clock is set back one second; if in leap-delete
368 * state, the system clock is set ahead one second.
370 switch (time_state) {
372 if (time_status & STA_INS)
373 time_state = TIME_INS;
374 else if (time_status & STA_DEL)
375 time_state = TIME_DEL;
378 if (secs % 86400 == 0) {
380 time_state = TIME_OOP;
383 "Clock: inserting leap second 23:59:60 UTC\n");
387 if ((secs + 1) % 86400 == 0) {
390 time_state = TIME_WAIT;
392 "Clock: deleting leap second 23:59:59 UTC\n");
396 time_state = TIME_WAIT;
400 if (!(time_status & (STA_INS | STA_DEL)))
401 time_state = TIME_OK;
406 /* Bump the maxerror field */
407 time_maxerror += MAXFREQ / NSEC_PER_USEC;
408 if (time_maxerror > NTP_PHASE_LIMIT) {
409 time_maxerror = NTP_PHASE_LIMIT;
410 time_status |= STA_UNSYNC;
413 /* Compute the phase adjustment for the next second */
414 tick_length = tick_length_base;
416 delta = ntp_offset_chunk(time_offset);
417 time_offset -= delta;
418 tick_length += delta;
420 /* Check PPS signal */
426 if (time_adjust > MAX_TICKADJ) {
427 time_adjust -= MAX_TICKADJ;
428 tick_length += MAX_TICKADJ_SCALED;
432 if (time_adjust < -MAX_TICKADJ) {
433 time_adjust += MAX_TICKADJ;
434 tick_length -= MAX_TICKADJ_SCALED;
438 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
445 #ifdef CONFIG_GENERIC_CMOS_UPDATE
447 /* Disable the cmos update - used by virtualization and embedded */
448 int no_sync_cmos_clock __read_mostly;
450 static void sync_cmos_clock(struct work_struct *work);
452 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
454 static void sync_cmos_clock(struct work_struct *work)
456 struct timespec now, next;
460 * If we have an externally synchronized Linux clock, then update
461 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
462 * called as close as possible to 500 ms before the new second starts.
463 * This code is run on a timer. If the clock is set, that timer
464 * may not expire at the correct time. Thus, we adjust...
468 * Not synced, exit, do not restart a timer (if one is
469 * running, let it run out).
474 getnstimeofday(&now);
475 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
476 fail = update_persistent_clock(now);
478 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
479 if (next.tv_nsec <= 0)
480 next.tv_nsec += NSEC_PER_SEC;
487 if (next.tv_nsec >= NSEC_PER_SEC) {
489 next.tv_nsec -= NSEC_PER_SEC;
491 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
494 static void notify_cmos_timer(void)
496 if (!no_sync_cmos_clock)
497 schedule_delayed_work(&sync_cmos_work, 0);
501 static inline void notify_cmos_timer(void) { }
506 * Propagate a new txc->status value into the NTP state:
508 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
510 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
511 time_state = TIME_OK;
512 time_status = STA_UNSYNC;
513 /* restart PPS frequency calibration */
514 pps_reset_freq_interval();
518 * If we turn on PLL adjustments then reset the
519 * reference time to current time.
521 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
522 time_reftime = get_seconds();
524 /* only set allowed bits */
525 time_status &= STA_RONLY;
526 time_status |= txc->status & ~STA_RONLY;
530 * Called with the xtime lock held, so we can access and modify
531 * all the global NTP state:
533 static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
535 if (txc->modes & ADJ_STATUS)
536 process_adj_status(txc, ts);
538 if (txc->modes & ADJ_NANO)
539 time_status |= STA_NANO;
541 if (txc->modes & ADJ_MICRO)
542 time_status &= ~STA_NANO;
544 if (txc->modes & ADJ_FREQUENCY) {
545 time_freq = txc->freq * PPM_SCALE;
546 time_freq = min(time_freq, MAXFREQ_SCALED);
547 time_freq = max(time_freq, -MAXFREQ_SCALED);
548 /* update pps_freq */
549 pps_set_freq(time_freq);
552 if (txc->modes & ADJ_MAXERROR)
553 time_maxerror = txc->maxerror;
555 if (txc->modes & ADJ_ESTERROR)
556 time_esterror = txc->esterror;
558 if (txc->modes & ADJ_TIMECONST) {
559 time_constant = txc->constant;
560 if (!(time_status & STA_NANO))
562 time_constant = min(time_constant, (long)MAXTC);
563 time_constant = max(time_constant, 0l);
566 if (txc->modes & ADJ_TAI && txc->constant > 0)
567 time_tai = txc->constant;
569 if (txc->modes & ADJ_OFFSET)
570 ntp_update_offset(txc->offset);
572 if (txc->modes & ADJ_TICK)
573 tick_usec = txc->tick;
575 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
576 ntp_update_frequency();
580 * adjtimex mainly allows reading (and writing, if superuser) of
581 * kernel time-keeping variables. used by xntpd.
583 int do_adjtimex(struct timex *txc)
588 /* Validate the data before disabling interrupts */
589 if (txc->modes & ADJ_ADJTIME) {
590 /* singleshot must not be used with any other mode bits */
591 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
593 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
594 !capable(CAP_SYS_TIME))
597 /* In order to modify anything, you gotta be super-user! */
598 if (txc->modes && !capable(CAP_SYS_TIME))
602 * if the quartz is off by more than 10% then
603 * something is VERY wrong!
605 if (txc->modes & ADJ_TICK &&
606 (txc->tick < 900000/USER_HZ ||
607 txc->tick > 1100000/USER_HZ))
612 * Check for potential multiplication overflows that can
613 * only happen on 64-bit systems:
615 if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
616 if (LLONG_MIN / PPM_SCALE > txc->freq)
618 if (LLONG_MAX / PPM_SCALE < txc->freq)
622 if (txc->modes & ADJ_SETOFFSET) {
623 struct timespec delta;
624 delta.tv_sec = txc->time.tv_sec;
625 delta.tv_nsec = txc->time.tv_usec;
626 if (!capable(CAP_SYS_TIME))
628 if (!(txc->modes & ADJ_NANO))
629 delta.tv_nsec *= 1000;
630 result = timekeeping_inject_offset(&delta);
637 write_seqlock_irq(&xtime_lock);
639 if (txc->modes & ADJ_ADJTIME) {
640 long save_adjust = time_adjust;
642 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
643 /* adjtime() is independent from ntp_adjtime() */
644 time_adjust = txc->offset;
645 ntp_update_frequency();
647 txc->offset = save_adjust;
650 /* If there are input parameters, then process them: */
652 process_adjtimex_modes(txc, &ts);
654 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
656 if (!(time_status & STA_NANO))
657 txc->offset /= NSEC_PER_USEC;
660 result = time_state; /* mostly `TIME_OK' */
661 /* check for errors */
662 if (is_error_status(time_status))
665 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
666 PPM_SCALE_INV, NTP_SCALE_SHIFT);
667 txc->maxerror = time_maxerror;
668 txc->esterror = time_esterror;
669 txc->status = time_status;
670 txc->constant = time_constant;
672 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
673 txc->tick = tick_usec;
676 /* fill PPS status fields */
679 write_sequnlock_irq(&xtime_lock);
681 txc->time.tv_sec = ts.tv_sec;
682 txc->time.tv_usec = ts.tv_nsec;
683 if (!(time_status & STA_NANO))
684 txc->time.tv_usec /= NSEC_PER_USEC;
691 #ifdef CONFIG_NTP_PPS
693 /* actually struct pps_normtime is good old struct timespec, but it is
694 * semantically different (and it is the reason why it was invented):
695 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
696 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
697 struct pps_normtime {
698 __kernel_time_t sec; /* seconds */
699 long nsec; /* nanoseconds */
702 /* normalize the timestamp so that nsec is in the
703 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
704 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
706 struct pps_normtime norm = {
711 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
712 norm.nsec -= NSEC_PER_SEC;
719 /* get current phase correction and jitter */
720 static inline long pps_phase_filter_get(long *jitter)
722 *jitter = pps_tf[0] - pps_tf[1];
726 /* TODO: test various filters */
730 /* add the sample to the phase filter */
731 static inline void pps_phase_filter_add(long err)
733 pps_tf[2] = pps_tf[1];
734 pps_tf[1] = pps_tf[0];
738 /* decrease frequency calibration interval length.
739 * It is halved after four consecutive unstable intervals.
741 static inline void pps_dec_freq_interval(void)
743 if (--pps_intcnt <= -PPS_INTCOUNT) {
744 pps_intcnt = -PPS_INTCOUNT;
745 if (pps_shift > PPS_INTMIN) {
752 /* increase frequency calibration interval length.
753 * It is doubled after four consecutive stable intervals.
755 static inline void pps_inc_freq_interval(void)
757 if (++pps_intcnt >= PPS_INTCOUNT) {
758 pps_intcnt = PPS_INTCOUNT;
759 if (pps_shift < PPS_INTMAX) {
766 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
769 * At the end of the calibration interval the difference between the
770 * first and last MONOTONIC_RAW clock timestamps divided by the length
771 * of the interval becomes the frequency update. If the interval was
772 * too long, the data are discarded.
773 * Returns the difference between old and new frequency values.
775 static long hardpps_update_freq(struct pps_normtime freq_norm)
777 long delta, delta_mod;
780 /* check if the frequency interval was too long */
781 if (freq_norm.sec > (2 << pps_shift)) {
782 time_status |= STA_PPSERROR;
784 pps_dec_freq_interval();
785 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
790 /* here the raw frequency offset and wander (stability) is
791 * calculated. If the wander is less than the wander threshold
792 * the interval is increased; otherwise it is decreased.
794 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
796 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
798 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
799 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
800 time_status |= STA_PPSWANDER;
802 pps_dec_freq_interval();
803 } else { /* good sample */
804 pps_inc_freq_interval();
807 /* the stability metric is calculated as the average of recent
808 * frequency changes, but is used only for performance
813 delta_mod = -delta_mod;
814 pps_stabil += (div_s64(((s64)delta_mod) <<
815 (NTP_SCALE_SHIFT - SHIFT_USEC),
816 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
818 /* if enabled, the system clock frequency is updated */
819 if ((time_status & STA_PPSFREQ) != 0 &&
820 (time_status & STA_FREQHOLD) == 0) {
821 time_freq = pps_freq;
822 ntp_update_frequency();
828 /* correct REALTIME clock phase error against PPS signal */
829 static void hardpps_update_phase(long error)
831 long correction = -error;
834 /* add the sample to the median filter */
835 pps_phase_filter_add(correction);
836 correction = pps_phase_filter_get(&jitter);
838 /* Nominal jitter is due to PPS signal noise. If it exceeds the
839 * threshold, the sample is discarded; otherwise, if so enabled,
840 * the time offset is updated.
842 if (jitter > (pps_jitter << PPS_POPCORN)) {
843 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
844 jitter, (pps_jitter << PPS_POPCORN));
845 time_status |= STA_PPSJITTER;
847 } else if (time_status & STA_PPSTIME) {
848 /* correct the time using the phase offset */
849 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
851 /* cancel running adjtime() */
855 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
859 * hardpps() - discipline CPU clock oscillator to external PPS signal
861 * This routine is called at each PPS signal arrival in order to
862 * discipline the CPU clock oscillator to the PPS signal. It takes two
863 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
864 * is used to correct clock phase error and the latter is used to
865 * correct the frequency.
867 * This code is based on David Mills's reference nanokernel
868 * implementation. It was mostly rewritten but keeps the same idea.
870 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
872 struct pps_normtime pts_norm, freq_norm;
875 pts_norm = pps_normalize_ts(*phase_ts);
877 write_seqlock_irqsave(&xtime_lock, flags);
879 /* clear the error bits, they will be set again if needed */
880 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
882 /* indicate signal presence */
883 time_status |= STA_PPSSIGNAL;
884 pps_valid = PPS_VALID;
886 /* when called for the first time,
887 * just start the frequency interval */
888 if (unlikely(pps_fbase.tv_sec == 0)) {
890 write_sequnlock_irqrestore(&xtime_lock, flags);
894 /* ok, now we have a base for frequency calculation */
895 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
897 /* check that the signal is in the range
898 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
899 if ((freq_norm.sec == 0) ||
900 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
901 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
902 time_status |= STA_PPSJITTER;
903 /* restart the frequency calibration interval */
905 write_sequnlock_irqrestore(&xtime_lock, flags);
906 pr_err("hardpps: PPSJITTER: bad pulse\n");
912 /* check if the current frequency interval is finished */
913 if (freq_norm.sec >= (1 << pps_shift)) {
915 /* restart the frequency calibration interval */
917 hardpps_update_freq(freq_norm);
920 hardpps_update_phase(pts_norm.nsec);
922 write_sequnlock_irqrestore(&xtime_lock, flags);
924 EXPORT_SYMBOL(hardpps);
926 #endif /* CONFIG_NTP_PPS */
928 static int __init ntp_tick_adj_setup(char *str)
930 ntp_tick_adj = simple_strtol(str, NULL, 0);
931 ntp_tick_adj <<= NTP_SCALE_SHIFT;
936 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
938 void __init ntp_init(void)