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>
18 #include <linux/rtc.h>
19 #include <linux/math64.h>
21 #include "ntp_internal.h"
22 #include "timekeeping_internal.h"
26 * NTP timekeeping variables:
28 * Note: All of the NTP state is protected by the timekeeping locks.
32 /* USER_HZ period (usecs): */
33 unsigned long tick_usec = TICK_USEC;
35 /* SHIFTED_HZ period (nsecs): */
36 unsigned long tick_nsec;
38 static u64 tick_length;
39 static u64 tick_length_base;
41 #define SECS_PER_DAY 86400
42 #define MAX_TICKADJ 500LL /* usecs */
43 #define MAX_TICKADJ_SCALED \
44 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
47 * phase-lock loop variables
51 * clock synchronization status
53 * (TIME_ERROR prevents overwriting the CMOS clock)
55 static int time_state = TIME_OK;
57 /* clock status bits: */
58 static int time_status = STA_UNSYNC;
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 time64_t time_reftime;
78 static long time_adjust;
80 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
81 static s64 ntp_tick_adj;
83 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */
84 static time64_t ntp_next_leap_sec = TIME64_MAX;
89 * The following variables are used when a pulse-per-second (PPS) signal
90 * is available. They establish the engineering parameters of the clock
91 * discipline loop when controlled by the PPS signal.
93 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
94 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
95 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
96 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
97 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
98 increase pps_shift or consecutive bad
99 intervals to decrease it */
100 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
102 static int pps_valid; /* signal watchdog counter */
103 static long pps_tf[3]; /* phase median filter */
104 static long pps_jitter; /* current jitter (ns) */
105 static struct timespec64 pps_fbase; /* beginning of the last freq interval */
106 static int pps_shift; /* current interval duration (s) (shift) */
107 static int pps_intcnt; /* interval counter */
108 static s64 pps_freq; /* frequency offset (scaled ns/s) */
109 static long pps_stabil; /* current stability (scaled ns/s) */
112 * PPS signal quality monitors
114 static long pps_calcnt; /* calibration intervals */
115 static long pps_jitcnt; /* jitter limit exceeded */
116 static long pps_stbcnt; /* stability limit exceeded */
117 static long pps_errcnt; /* calibration errors */
120 /* PPS kernel consumer compensates the whole phase error immediately.
121 * Otherwise, reduce the offset by a fixed factor times the time constant.
123 static inline s64 ntp_offset_chunk(s64 offset)
125 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
128 return shift_right(offset, SHIFT_PLL + time_constant);
131 static inline void pps_reset_freq_interval(void)
133 /* the PPS calibration interval may end
134 surprisingly early */
135 pps_shift = PPS_INTMIN;
140 * pps_clear - Clears the PPS state variables
142 static inline void pps_clear(void)
144 pps_reset_freq_interval();
148 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
152 /* Decrease pps_valid to indicate that another second has passed since
153 * the last PPS signal. When it reaches 0, indicate that PPS signal is
156 static inline void pps_dec_valid(void)
161 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
162 STA_PPSWANDER | STA_PPSERROR);
167 static inline void pps_set_freq(s64 freq)
172 static inline int is_error_status(int status)
174 return (status & (STA_UNSYNC|STA_CLOCKERR))
175 /* PPS signal lost when either PPS time or
176 * PPS frequency synchronization requested
178 || ((status & (STA_PPSFREQ|STA_PPSTIME))
179 && !(status & STA_PPSSIGNAL))
180 /* PPS jitter exceeded when
181 * PPS time synchronization requested */
182 || ((status & (STA_PPSTIME|STA_PPSJITTER))
183 == (STA_PPSTIME|STA_PPSJITTER))
184 /* PPS wander exceeded or calibration error when
185 * PPS frequency synchronization requested
187 || ((status & STA_PPSFREQ)
188 && (status & (STA_PPSWANDER|STA_PPSERROR)));
191 static inline void pps_fill_timex(struct timex *txc)
193 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
194 PPM_SCALE_INV, NTP_SCALE_SHIFT);
195 txc->jitter = pps_jitter;
196 if (!(time_status & STA_NANO))
197 txc->jitter /= NSEC_PER_USEC;
198 txc->shift = pps_shift;
199 txc->stabil = pps_stabil;
200 txc->jitcnt = pps_jitcnt;
201 txc->calcnt = pps_calcnt;
202 txc->errcnt = pps_errcnt;
203 txc->stbcnt = pps_stbcnt;
206 #else /* !CONFIG_NTP_PPS */
208 static inline s64 ntp_offset_chunk(s64 offset)
210 return shift_right(offset, SHIFT_PLL + time_constant);
213 static inline void pps_reset_freq_interval(void) {}
214 static inline void pps_clear(void) {}
215 static inline void pps_dec_valid(void) {}
216 static inline void pps_set_freq(s64 freq) {}
218 static inline int is_error_status(int status)
220 return status & (STA_UNSYNC|STA_CLOCKERR);
223 static inline void pps_fill_timex(struct timex *txc)
225 /* PPS is not implemented, so these are zero */
236 #endif /* CONFIG_NTP_PPS */
240 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
243 static inline int ntp_synced(void)
245 return !(time_status & STA_UNSYNC);
254 * Update (tick_length, tick_length_base, tick_nsec), based
255 * on (tick_usec, ntp_tick_adj, time_freq):
257 static void ntp_update_frequency(void)
262 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
265 second_length += ntp_tick_adj;
266 second_length += time_freq;
268 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
269 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
272 * Don't wait for the next second_overflow, apply
273 * the change to the tick length immediately:
275 tick_length += new_base - tick_length_base;
276 tick_length_base = new_base;
279 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
281 time_status &= ~STA_MODE;
286 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
289 time_status |= STA_MODE;
291 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
294 static void ntp_update_offset(long offset)
300 if (!(time_status & STA_PLL))
303 if (!(time_status & STA_NANO)) {
304 /* Make sure the multiplication below won't overflow */
305 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
306 offset *= NSEC_PER_USEC;
310 * Scale the phase adjustment and
311 * clamp to the operating range.
313 offset = clamp(offset, -MAXPHASE, MAXPHASE);
316 * Select how the frequency is to be controlled
317 * and in which mode (PLL or FLL).
319 secs = (long)(__ktime_get_real_seconds() - time_reftime);
320 if (unlikely(time_status & STA_FREQHOLD))
323 time_reftime = __ktime_get_real_seconds();
326 freq_adj = ntp_update_offset_fll(offset64, secs);
329 * Clamp update interval to reduce PLL gain with low
330 * sampling rate (e.g. intermittent network connection)
331 * to avoid instability.
333 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
334 secs = 1 << (SHIFT_PLL + 1 + time_constant);
336 freq_adj += (offset64 * secs) <<
337 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
339 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
341 time_freq = max(freq_adj, -MAXFREQ_SCALED);
343 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
347 * ntp_clear - Clears the NTP state variables
351 time_adjust = 0; /* stop active adjtime() */
352 time_status |= STA_UNSYNC;
353 time_maxerror = NTP_PHASE_LIMIT;
354 time_esterror = NTP_PHASE_LIMIT;
356 ntp_update_frequency();
358 tick_length = tick_length_base;
361 ntp_next_leap_sec = TIME64_MAX;
362 /* Clear PPS state variables */
367 u64 ntp_tick_length(void)
373 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
375 * Provides the time of the next leapsecond against CLOCK_REALTIME in
376 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
378 ktime_t ntp_get_next_leap(void)
382 if ((time_state == TIME_INS) && (time_status & STA_INS))
383 return ktime_set(ntp_next_leap_sec, 0);
384 ret.tv64 = KTIME_MAX;
389 * this routine handles the overflow of the microsecond field
391 * The tricky bits of code to handle the accurate clock support
392 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
393 * They were originally developed for SUN and DEC kernels.
394 * All the kudos should go to Dave for this stuff.
396 * Also handles leap second processing, and returns leap offset
398 int second_overflow(time64_t secs)
405 * Leap second processing. If in leap-insert state at the end of the
406 * day, the system clock is set back one second; if in leap-delete
407 * state, the system clock is set ahead one second.
409 switch (time_state) {
411 if (time_status & STA_INS) {
412 time_state = TIME_INS;
413 div_s64_rem(secs, SECS_PER_DAY, &rem);
414 ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
415 } else if (time_status & STA_DEL) {
416 time_state = TIME_DEL;
417 div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
418 ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
422 if (!(time_status & STA_INS)) {
423 ntp_next_leap_sec = TIME64_MAX;
424 time_state = TIME_OK;
425 } else if (secs == ntp_next_leap_sec) {
427 time_state = TIME_OOP;
429 "Clock: inserting leap second 23:59:60 UTC\n");
433 if (!(time_status & STA_DEL)) {
434 ntp_next_leap_sec = TIME64_MAX;
435 time_state = TIME_OK;
436 } else if (secs == ntp_next_leap_sec) {
438 ntp_next_leap_sec = TIME64_MAX;
439 time_state = TIME_WAIT;
441 "Clock: deleting leap second 23:59:59 UTC\n");
445 ntp_next_leap_sec = TIME64_MAX;
446 time_state = TIME_WAIT;
449 if (!(time_status & (STA_INS | STA_DEL)))
450 time_state = TIME_OK;
455 /* Bump the maxerror field */
456 time_maxerror += MAXFREQ / NSEC_PER_USEC;
457 if (time_maxerror > NTP_PHASE_LIMIT) {
458 time_maxerror = NTP_PHASE_LIMIT;
459 time_status |= STA_UNSYNC;
462 /* Compute the phase adjustment for the next second */
463 tick_length = tick_length_base;
465 delta = ntp_offset_chunk(time_offset);
466 time_offset -= delta;
467 tick_length += delta;
469 /* Check PPS signal */
475 if (time_adjust > MAX_TICKADJ) {
476 time_adjust -= MAX_TICKADJ;
477 tick_length += MAX_TICKADJ_SCALED;
481 if (time_adjust < -MAX_TICKADJ) {
482 time_adjust += MAX_TICKADJ;
483 tick_length -= MAX_TICKADJ_SCALED;
487 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
495 #ifdef CONFIG_GENERIC_CMOS_UPDATE
496 int __weak update_persistent_clock(struct timespec now)
501 int __weak update_persistent_clock64(struct timespec64 now64)
505 now = timespec64_to_timespec(now64);
506 return update_persistent_clock(now);
510 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
511 static void sync_cmos_clock(struct work_struct *work);
513 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
515 static void sync_cmos_clock(struct work_struct *work)
517 struct timespec64 now;
518 struct timespec64 next;
522 * If we have an externally synchronized Linux clock, then update
523 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
524 * called as close as possible to 500 ms before the new second starts.
525 * This code is run on a timer. If the clock is set, that timer
526 * may not expire at the correct time. Thus, we adjust...
527 * We want the clock to be within a couple of ticks from the target.
531 * Not synced, exit, do not restart a timer (if one is
532 * running, let it run out).
537 getnstimeofday64(&now);
538 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) {
539 struct timespec64 adjust = now;
542 if (persistent_clock_is_local)
543 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
544 #ifdef CONFIG_GENERIC_CMOS_UPDATE
545 fail = update_persistent_clock64(adjust);
548 #ifdef CONFIG_RTC_SYSTOHC
550 fail = rtc_set_ntp_time(adjust);
554 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
555 if (next.tv_nsec <= 0)
556 next.tv_nsec += NSEC_PER_SEC;
558 if (!fail || fail == -ENODEV)
563 if (next.tv_nsec >= NSEC_PER_SEC) {
565 next.tv_nsec -= NSEC_PER_SEC;
567 queue_delayed_work(system_power_efficient_wq,
568 &sync_cmos_work, timespec64_to_jiffies(&next));
571 void ntp_notify_cmos_timer(void)
573 queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0);
577 void ntp_notify_cmos_timer(void) { }
582 * Propagate a new txc->status value into the NTP state:
584 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts)
586 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
587 time_state = TIME_OK;
588 time_status = STA_UNSYNC;
589 ntp_next_leap_sec = TIME64_MAX;
590 /* restart PPS frequency calibration */
591 pps_reset_freq_interval();
595 * If we turn on PLL adjustments then reset the
596 * reference time to current time.
598 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
599 time_reftime = __ktime_get_real_seconds();
601 /* only set allowed bits */
602 time_status &= STA_RONLY;
603 time_status |= txc->status & ~STA_RONLY;
607 static inline void process_adjtimex_modes(struct timex *txc,
608 struct timespec64 *ts,
611 if (txc->modes & ADJ_STATUS)
612 process_adj_status(txc, ts);
614 if (txc->modes & ADJ_NANO)
615 time_status |= STA_NANO;
617 if (txc->modes & ADJ_MICRO)
618 time_status &= ~STA_NANO;
620 if (txc->modes & ADJ_FREQUENCY) {
621 time_freq = txc->freq * PPM_SCALE;
622 time_freq = min(time_freq, MAXFREQ_SCALED);
623 time_freq = max(time_freq, -MAXFREQ_SCALED);
624 /* update pps_freq */
625 pps_set_freq(time_freq);
628 if (txc->modes & ADJ_MAXERROR)
629 time_maxerror = txc->maxerror;
631 if (txc->modes & ADJ_ESTERROR)
632 time_esterror = txc->esterror;
634 if (txc->modes & ADJ_TIMECONST) {
635 time_constant = txc->constant;
636 if (!(time_status & STA_NANO))
638 time_constant = min(time_constant, (long)MAXTC);
639 time_constant = max(time_constant, 0l);
642 if (txc->modes & ADJ_TAI && txc->constant > 0)
643 *time_tai = txc->constant;
645 if (txc->modes & ADJ_OFFSET)
646 ntp_update_offset(txc->offset);
648 if (txc->modes & ADJ_TICK)
649 tick_usec = txc->tick;
651 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
652 ntp_update_frequency();
658 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
660 int ntp_validate_timex(struct timex *txc)
662 if (txc->modes & ADJ_ADJTIME) {
663 /* singleshot must not be used with any other mode bits */
664 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
666 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
667 !capable(CAP_SYS_TIME))
670 /* In order to modify anything, you gotta be super-user! */
671 if (txc->modes && !capable(CAP_SYS_TIME))
674 * if the quartz is off by more than 10% then
675 * something is VERY wrong!
677 if (txc->modes & ADJ_TICK &&
678 (txc->tick < 900000/USER_HZ ||
679 txc->tick > 1100000/USER_HZ))
683 if (txc->modes & ADJ_SETOFFSET) {
684 /* In order to inject time, you gotta be super-user! */
685 if (!capable(CAP_SYS_TIME))
688 if (txc->modes & ADJ_NANO) {
691 ts.tv_sec = txc->time.tv_sec;
692 ts.tv_nsec = txc->time.tv_usec;
693 if (!timespec_inject_offset_valid(&ts))
697 if (!timeval_inject_offset_valid(&txc->time))
703 * Check for potential multiplication overflows that can
704 * only happen on 64-bit systems:
706 if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
707 if (LLONG_MIN / PPM_SCALE > txc->freq)
709 if (LLONG_MAX / PPM_SCALE < txc->freq)
718 * adjtimex mainly allows reading (and writing, if superuser) of
719 * kernel time-keeping variables. used by xntpd.
721 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai)
725 if (txc->modes & ADJ_ADJTIME) {
726 long save_adjust = time_adjust;
728 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
729 /* adjtime() is independent from ntp_adjtime() */
730 time_adjust = txc->offset;
731 ntp_update_frequency();
733 txc->offset = save_adjust;
736 /* If there are input parameters, then process them: */
738 process_adjtimex_modes(txc, ts, time_tai);
740 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
742 if (!(time_status & STA_NANO))
743 txc->offset /= NSEC_PER_USEC;
746 result = time_state; /* mostly `TIME_OK' */
747 /* check for errors */
748 if (is_error_status(time_status))
751 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
752 PPM_SCALE_INV, NTP_SCALE_SHIFT);
753 txc->maxerror = time_maxerror;
754 txc->esterror = time_esterror;
755 txc->status = time_status;
756 txc->constant = time_constant;
758 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
759 txc->tick = tick_usec;
760 txc->tai = *time_tai;
762 /* fill PPS status fields */
765 txc->time.tv_sec = (time_t)ts->tv_sec;
766 txc->time.tv_usec = ts->tv_nsec;
767 if (!(time_status & STA_NANO))
768 txc->time.tv_usec /= NSEC_PER_USEC;
770 /* Handle leapsec adjustments */
771 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
772 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
777 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
782 if ((time_state == TIME_OOP) &&
783 (ts->tv_sec == ntp_next_leap_sec)) {
791 #ifdef CONFIG_NTP_PPS
793 /* actually struct pps_normtime is good old struct timespec, but it is
794 * semantically different (and it is the reason why it was invented):
795 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
796 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
797 struct pps_normtime {
798 s64 sec; /* seconds */
799 long nsec; /* nanoseconds */
802 /* normalize the timestamp so that nsec is in the
803 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
804 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
806 struct pps_normtime norm = {
811 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
812 norm.nsec -= NSEC_PER_SEC;
819 /* get current phase correction and jitter */
820 static inline long pps_phase_filter_get(long *jitter)
822 *jitter = pps_tf[0] - pps_tf[1];
826 /* TODO: test various filters */
830 /* add the sample to the phase filter */
831 static inline void pps_phase_filter_add(long err)
833 pps_tf[2] = pps_tf[1];
834 pps_tf[1] = pps_tf[0];
838 /* decrease frequency calibration interval length.
839 * It is halved after four consecutive unstable intervals.
841 static inline void pps_dec_freq_interval(void)
843 if (--pps_intcnt <= -PPS_INTCOUNT) {
844 pps_intcnt = -PPS_INTCOUNT;
845 if (pps_shift > PPS_INTMIN) {
852 /* increase frequency calibration interval length.
853 * It is doubled after four consecutive stable intervals.
855 static inline void pps_inc_freq_interval(void)
857 if (++pps_intcnt >= PPS_INTCOUNT) {
858 pps_intcnt = PPS_INTCOUNT;
859 if (pps_shift < PPS_INTMAX) {
866 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
869 * At the end of the calibration interval the difference between the
870 * first and last MONOTONIC_RAW clock timestamps divided by the length
871 * of the interval becomes the frequency update. If the interval was
872 * too long, the data are discarded.
873 * Returns the difference between old and new frequency values.
875 static long hardpps_update_freq(struct pps_normtime freq_norm)
877 long delta, delta_mod;
880 /* check if the frequency interval was too long */
881 if (freq_norm.sec > (2 << pps_shift)) {
882 time_status |= STA_PPSERROR;
884 pps_dec_freq_interval();
885 printk_deferred(KERN_ERR
886 "hardpps: PPSERROR: interval too long - %lld s\n",
891 /* here the raw frequency offset and wander (stability) is
892 * calculated. If the wander is less than the wander threshold
893 * the interval is increased; otherwise it is decreased.
895 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
897 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
899 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
900 printk_deferred(KERN_WARNING
901 "hardpps: PPSWANDER: change=%ld\n", delta);
902 time_status |= STA_PPSWANDER;
904 pps_dec_freq_interval();
905 } else { /* good sample */
906 pps_inc_freq_interval();
909 /* the stability metric is calculated as the average of recent
910 * frequency changes, but is used only for performance
915 delta_mod = -delta_mod;
916 pps_stabil += (div_s64(((s64)delta_mod) <<
917 (NTP_SCALE_SHIFT - SHIFT_USEC),
918 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
920 /* if enabled, the system clock frequency is updated */
921 if ((time_status & STA_PPSFREQ) != 0 &&
922 (time_status & STA_FREQHOLD) == 0) {
923 time_freq = pps_freq;
924 ntp_update_frequency();
930 /* correct REALTIME clock phase error against PPS signal */
931 static void hardpps_update_phase(long error)
933 long correction = -error;
936 /* add the sample to the median filter */
937 pps_phase_filter_add(correction);
938 correction = pps_phase_filter_get(&jitter);
940 /* Nominal jitter is due to PPS signal noise. If it exceeds the
941 * threshold, the sample is discarded; otherwise, if so enabled,
942 * the time offset is updated.
944 if (jitter > (pps_jitter << PPS_POPCORN)) {
945 printk_deferred(KERN_WARNING
946 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
947 jitter, (pps_jitter << PPS_POPCORN));
948 time_status |= STA_PPSJITTER;
950 } else if (time_status & STA_PPSTIME) {
951 /* correct the time using the phase offset */
952 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
954 /* cancel running adjtime() */
958 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
962 * __hardpps() - discipline CPU clock oscillator to external PPS signal
964 * This routine is called at each PPS signal arrival in order to
965 * discipline the CPU clock oscillator to the PPS signal. It takes two
966 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
967 * is used to correct clock phase error and the latter is used to
968 * correct the frequency.
970 * This code is based on David Mills's reference nanokernel
971 * implementation. It was mostly rewritten but keeps the same idea.
973 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
975 struct pps_normtime pts_norm, freq_norm;
977 pts_norm = pps_normalize_ts(*phase_ts);
979 /* clear the error bits, they will be set again if needed */
980 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
982 /* indicate signal presence */
983 time_status |= STA_PPSSIGNAL;
984 pps_valid = PPS_VALID;
986 /* when called for the first time,
987 * just start the frequency interval */
988 if (unlikely(pps_fbase.tv_sec == 0)) {
993 /* ok, now we have a base for frequency calculation */
994 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
996 /* check that the signal is in the range
997 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
998 if ((freq_norm.sec == 0) ||
999 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1000 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1001 time_status |= STA_PPSJITTER;
1002 /* restart the frequency calibration interval */
1003 pps_fbase = *raw_ts;
1004 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1010 /* check if the current frequency interval is finished */
1011 if (freq_norm.sec >= (1 << pps_shift)) {
1013 /* restart the frequency calibration interval */
1014 pps_fbase = *raw_ts;
1015 hardpps_update_freq(freq_norm);
1018 hardpps_update_phase(pts_norm.nsec);
1021 #endif /* CONFIG_NTP_PPS */
1023 static int __init ntp_tick_adj_setup(char *str)
1025 int rc = kstrtol(str, 0, (long *)&ntp_tick_adj);
1029 ntp_tick_adj <<= NTP_SCALE_SHIFT;
1034 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1036 void __init ntp_init(void)