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>
20 #include "tick-internal.h"
21 #include "ntp_internal.h"
24 * NTP timekeeping variables:
27 DEFINE_RAW_SPINLOCK(ntp_lock);
30 /* USER_HZ period (usecs): */
31 unsigned long tick_usec = TICK_USEC;
33 /* SHIFTED_HZ period (nsecs): */
34 unsigned long tick_nsec;
36 static u64 tick_length;
37 static u64 tick_length_base;
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 /* 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 ntp_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 ntp_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 div64_long(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
349 raw_spin_lock_irqsave(&ntp_lock, flags);
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 /* Clear PPS state variables */
363 raw_spin_unlock_irqrestore(&ntp_lock, flags);
368 u64 ntp_tick_length(void)
373 raw_spin_lock_irqsave(&ntp_lock, flags);
375 raw_spin_unlock_irqrestore(&ntp_lock, flags);
381 * this routine handles the overflow of the microsecond field
383 * The tricky bits of code to handle the accurate clock support
384 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
385 * They were originally developed for SUN and DEC kernels.
386 * All the kudos should go to Dave for this stuff.
388 * Also handles leap second processing, and returns leap offset
390 int second_overflow(unsigned long secs)
396 raw_spin_lock_irqsave(&ntp_lock, flags);
399 * Leap second processing. If in leap-insert state at the end of the
400 * day, the system clock is set back one second; if in leap-delete
401 * state, the system clock is set ahead one second.
403 switch (time_state) {
405 if (time_status & STA_INS)
406 time_state = TIME_INS;
407 else if (time_status & STA_DEL)
408 time_state = TIME_DEL;
411 if (!(time_status & STA_INS))
412 time_state = TIME_OK;
413 else if (secs % 86400 == 0) {
415 time_state = TIME_OOP;
417 "Clock: inserting leap second 23:59:60 UTC\n");
421 if (!(time_status & STA_DEL))
422 time_state = TIME_OK;
423 else if ((secs + 1) % 86400 == 0) {
425 time_state = TIME_WAIT;
427 "Clock: deleting leap second 23:59:59 UTC\n");
431 time_state = TIME_WAIT;
435 if (!(time_status & (STA_INS | STA_DEL)))
436 time_state = TIME_OK;
441 /* Bump the maxerror field */
442 time_maxerror += MAXFREQ / NSEC_PER_USEC;
443 if (time_maxerror > NTP_PHASE_LIMIT) {
444 time_maxerror = NTP_PHASE_LIMIT;
445 time_status |= STA_UNSYNC;
448 /* Compute the phase adjustment for the next second */
449 tick_length = tick_length_base;
451 delta = ntp_offset_chunk(time_offset);
452 time_offset -= delta;
453 tick_length += delta;
455 /* Check PPS signal */
461 if (time_adjust > MAX_TICKADJ) {
462 time_adjust -= MAX_TICKADJ;
463 tick_length += MAX_TICKADJ_SCALED;
467 if (time_adjust < -MAX_TICKADJ) {
468 time_adjust += MAX_TICKADJ;
469 tick_length -= MAX_TICKADJ_SCALED;
473 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
478 raw_spin_unlock_irqrestore(&ntp_lock, flags);
483 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
484 static void sync_cmos_clock(struct work_struct *work);
486 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
488 static void sync_cmos_clock(struct work_struct *work)
490 struct timespec now, next;
494 * If we have an externally synchronized Linux clock, then update
495 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
496 * called as close as possible to 500 ms before the new second starts.
497 * This code is run on a timer. If the clock is set, that timer
498 * may not expire at the correct time. Thus, we adjust...
502 * Not synced, exit, do not restart a timer (if one is
503 * running, let it run out).
508 getnstimeofday(&now);
509 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2) {
510 struct timespec adjust = now;
513 if (persistent_clock_is_local)
514 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
515 #ifdef CONFIG_GENERIC_CMOS_UPDATE
516 fail = update_persistent_clock(adjust);
518 #ifdef CONFIG_RTC_SYSTOHC
520 fail = rtc_set_ntp_time(adjust);
524 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
525 if (next.tv_nsec <= 0)
526 next.tv_nsec += NSEC_PER_SEC;
528 if (!fail || fail == -ENODEV)
533 if (next.tv_nsec >= NSEC_PER_SEC) {
535 next.tv_nsec -= NSEC_PER_SEC;
537 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
540 static void notify_cmos_timer(void)
542 schedule_delayed_work(&sync_cmos_work, 0);
546 static inline void notify_cmos_timer(void) { }
551 * Propagate a new txc->status value into the NTP state:
553 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
555 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
556 time_state = TIME_OK;
557 time_status = STA_UNSYNC;
558 /* restart PPS frequency calibration */
559 pps_reset_freq_interval();
563 * If we turn on PLL adjustments then reset the
564 * reference time to current time.
566 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
567 time_reftime = get_seconds();
569 /* only set allowed bits */
570 time_status &= STA_RONLY;
571 time_status |= txc->status & ~STA_RONLY;
575 * Called with ntp_lock held, so we can access and modify
576 * all the global NTP state:
578 static inline void process_adjtimex_modes(struct timex *txc,
582 if (txc->modes & ADJ_STATUS)
583 process_adj_status(txc, ts);
585 if (txc->modes & ADJ_NANO)
586 time_status |= STA_NANO;
588 if (txc->modes & ADJ_MICRO)
589 time_status &= ~STA_NANO;
591 if (txc->modes & ADJ_FREQUENCY) {
592 time_freq = txc->freq * PPM_SCALE;
593 time_freq = min(time_freq, MAXFREQ_SCALED);
594 time_freq = max(time_freq, -MAXFREQ_SCALED);
595 /* update pps_freq */
596 pps_set_freq(time_freq);
599 if (txc->modes & ADJ_MAXERROR)
600 time_maxerror = txc->maxerror;
602 if (txc->modes & ADJ_ESTERROR)
603 time_esterror = txc->esterror;
605 if (txc->modes & ADJ_TIMECONST) {
606 time_constant = txc->constant;
607 if (!(time_status & STA_NANO))
609 time_constant = min(time_constant, (long)MAXTC);
610 time_constant = max(time_constant, 0l);
613 if (txc->modes & ADJ_TAI && txc->constant > 0)
614 *time_tai = txc->constant;
616 if (txc->modes & ADJ_OFFSET)
617 ntp_update_offset(txc->offset);
619 if (txc->modes & ADJ_TICK)
620 tick_usec = txc->tick;
622 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
623 ntp_update_frequency();
629 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
631 int ntp_validate_timex(struct timex *txc)
633 if (txc->modes & ADJ_ADJTIME) {
634 /* singleshot must not be used with any other mode bits */
635 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
637 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
638 !capable(CAP_SYS_TIME))
641 /* In order to modify anything, you gotta be super-user! */
642 if (txc->modes && !capable(CAP_SYS_TIME))
645 * if the quartz is off by more than 10% then
646 * something is VERY wrong!
648 if (txc->modes & ADJ_TICK &&
649 (txc->tick < 900000/USER_HZ ||
650 txc->tick > 1100000/USER_HZ))
654 if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
662 * adjtimex mainly allows reading (and writing, if superuser) of
663 * kernel time-keeping variables. used by xntpd.
665 int __do_adjtimex(struct timex *txc)
668 u32 time_tai, orig_tai;
671 if (txc->modes & ADJ_SETOFFSET) {
672 struct timespec delta;
673 delta.tv_sec = txc->time.tv_sec;
674 delta.tv_nsec = txc->time.tv_usec;
675 if (!(txc->modes & ADJ_NANO))
676 delta.tv_nsec *= 1000;
677 result = timekeeping_inject_offset(&delta);
683 orig_tai = time_tai = timekeeping_get_tai_offset();
685 raw_spin_lock_irq(&ntp_lock);
687 if (txc->modes & ADJ_ADJTIME) {
688 long save_adjust = time_adjust;
690 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
691 /* adjtime() is independent from ntp_adjtime() */
692 time_adjust = txc->offset;
693 ntp_update_frequency();
695 txc->offset = save_adjust;
698 /* If there are input parameters, then process them: */
700 process_adjtimex_modes(txc, &ts, &time_tai);
702 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
704 if (!(time_status & STA_NANO))
705 txc->offset /= NSEC_PER_USEC;
708 result = time_state; /* mostly `TIME_OK' */
709 /* check for errors */
710 if (is_error_status(time_status))
713 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
714 PPM_SCALE_INV, NTP_SCALE_SHIFT);
715 txc->maxerror = time_maxerror;
716 txc->esterror = time_esterror;
717 txc->status = time_status;
718 txc->constant = time_constant;
720 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
721 txc->tick = tick_usec;
724 /* fill PPS status fields */
727 raw_spin_unlock_irq(&ntp_lock);
729 if (time_tai != orig_tai)
730 timekeeping_set_tai_offset(time_tai);
732 txc->time.tv_sec = ts.tv_sec;
733 txc->time.tv_usec = ts.tv_nsec;
734 if (!(time_status & STA_NANO))
735 txc->time.tv_usec /= NSEC_PER_USEC;
742 #ifdef CONFIG_NTP_PPS
744 /* actually struct pps_normtime is good old struct timespec, but it is
745 * semantically different (and it is the reason why it was invented):
746 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
747 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
748 struct pps_normtime {
749 __kernel_time_t sec; /* seconds */
750 long nsec; /* nanoseconds */
753 /* normalize the timestamp so that nsec is in the
754 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
755 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
757 struct pps_normtime norm = {
762 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
763 norm.nsec -= NSEC_PER_SEC;
770 /* get current phase correction and jitter */
771 static inline long pps_phase_filter_get(long *jitter)
773 *jitter = pps_tf[0] - pps_tf[1];
777 /* TODO: test various filters */
781 /* add the sample to the phase filter */
782 static inline void pps_phase_filter_add(long err)
784 pps_tf[2] = pps_tf[1];
785 pps_tf[1] = pps_tf[0];
789 /* decrease frequency calibration interval length.
790 * It is halved after four consecutive unstable intervals.
792 static inline void pps_dec_freq_interval(void)
794 if (--pps_intcnt <= -PPS_INTCOUNT) {
795 pps_intcnt = -PPS_INTCOUNT;
796 if (pps_shift > PPS_INTMIN) {
803 /* increase frequency calibration interval length.
804 * It is doubled after four consecutive stable intervals.
806 static inline void pps_inc_freq_interval(void)
808 if (++pps_intcnt >= PPS_INTCOUNT) {
809 pps_intcnt = PPS_INTCOUNT;
810 if (pps_shift < PPS_INTMAX) {
817 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
820 * At the end of the calibration interval the difference between the
821 * first and last MONOTONIC_RAW clock timestamps divided by the length
822 * of the interval becomes the frequency update. If the interval was
823 * too long, the data are discarded.
824 * Returns the difference between old and new frequency values.
826 static long hardpps_update_freq(struct pps_normtime freq_norm)
828 long delta, delta_mod;
831 /* check if the frequency interval was too long */
832 if (freq_norm.sec > (2 << pps_shift)) {
833 time_status |= STA_PPSERROR;
835 pps_dec_freq_interval();
836 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
841 /* here the raw frequency offset and wander (stability) is
842 * calculated. If the wander is less than the wander threshold
843 * the interval is increased; otherwise it is decreased.
845 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
847 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
849 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
850 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
851 time_status |= STA_PPSWANDER;
853 pps_dec_freq_interval();
854 } else { /* good sample */
855 pps_inc_freq_interval();
858 /* the stability metric is calculated as the average of recent
859 * frequency changes, but is used only for performance
864 delta_mod = -delta_mod;
865 pps_stabil += (div_s64(((s64)delta_mod) <<
866 (NTP_SCALE_SHIFT - SHIFT_USEC),
867 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
869 /* if enabled, the system clock frequency is updated */
870 if ((time_status & STA_PPSFREQ) != 0 &&
871 (time_status & STA_FREQHOLD) == 0) {
872 time_freq = pps_freq;
873 ntp_update_frequency();
879 /* correct REALTIME clock phase error against PPS signal */
880 static void hardpps_update_phase(long error)
882 long correction = -error;
885 /* add the sample to the median filter */
886 pps_phase_filter_add(correction);
887 correction = pps_phase_filter_get(&jitter);
889 /* Nominal jitter is due to PPS signal noise. If it exceeds the
890 * threshold, the sample is discarded; otherwise, if so enabled,
891 * the time offset is updated.
893 if (jitter > (pps_jitter << PPS_POPCORN)) {
894 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
895 jitter, (pps_jitter << PPS_POPCORN));
896 time_status |= STA_PPSJITTER;
898 } else if (time_status & STA_PPSTIME) {
899 /* correct the time using the phase offset */
900 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
902 /* cancel running adjtime() */
906 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
910 * __hardpps() - discipline CPU clock oscillator to external PPS signal
912 * This routine is called at each PPS signal arrival in order to
913 * discipline the CPU clock oscillator to the PPS signal. It takes two
914 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
915 * is used to correct clock phase error and the latter is used to
916 * correct the frequency.
918 * This code is based on David Mills's reference nanokernel
919 * implementation. It was mostly rewritten but keeps the same idea.
921 void __hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
923 struct pps_normtime pts_norm, freq_norm;
926 pts_norm = pps_normalize_ts(*phase_ts);
928 raw_spin_lock_irqsave(&ntp_lock, flags);
930 /* clear the error bits, they will be set again if needed */
931 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
933 /* indicate signal presence */
934 time_status |= STA_PPSSIGNAL;
935 pps_valid = PPS_VALID;
937 /* when called for the first time,
938 * just start the frequency interval */
939 if (unlikely(pps_fbase.tv_sec == 0)) {
941 raw_spin_unlock_irqrestore(&ntp_lock, flags);
945 /* ok, now we have a base for frequency calculation */
946 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
948 /* check that the signal is in the range
949 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
950 if ((freq_norm.sec == 0) ||
951 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
952 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
953 time_status |= STA_PPSJITTER;
954 /* restart the frequency calibration interval */
956 raw_spin_unlock_irqrestore(&ntp_lock, flags);
957 pr_err("hardpps: PPSJITTER: bad pulse\n");
963 /* check if the current frequency interval is finished */
964 if (freq_norm.sec >= (1 << pps_shift)) {
966 /* restart the frequency calibration interval */
968 hardpps_update_freq(freq_norm);
971 hardpps_update_phase(pts_norm.nsec);
973 raw_spin_unlock_irqrestore(&ntp_lock, flags);
975 #endif /* CONFIG_NTP_PPS */
977 static int __init ntp_tick_adj_setup(char *str)
979 ntp_tick_adj = simple_strtol(str, NULL, 0);
980 ntp_tick_adj <<= NTP_SCALE_SHIFT;
985 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
987 void __init ntp_init(void)