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 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 * Leap second processing. If in leap-insert state at the end of the
365 * day, the system clock is set back one second; if in leap-delete
366 * state, the system clock is set ahead one second.
368 static enum hrtimer_restart
ntp_leap_second(struct hrtimer
*timer
)
370 enum hrtimer_restart res
= HRTIMER_NORESTART
;
372 write_seqlock(&xtime_lock
);
374 switch (time_state
) {
378 timekeeping_leap_insert(-1);
379 time_state
= TIME_OOP
;
381 "Clock: inserting leap second 23:59:60 UTC\n");
382 hrtimer_add_expires_ns(&leap_timer
, NSEC_PER_SEC
);
383 res
= HRTIMER_RESTART
;
386 timekeeping_leap_insert(1);
388 time_state
= TIME_WAIT
;
390 "Clock: deleting leap second 23:59:59 UTC\n");
394 time_state
= TIME_WAIT
;
397 if (!(time_status
& (STA_INS
| STA_DEL
)))
398 time_state
= TIME_OK
;
402 write_sequnlock(&xtime_lock
);
408 * this routine handles the overflow of the microsecond field
410 * The tricky bits of code to handle the accurate clock support
411 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
412 * They were originally developed for SUN and DEC kernels.
413 * All the kudos should go to Dave for this stuff.
415 void second_overflow(void)
419 /* Bump the maxerror field */
420 time_maxerror
+= MAXFREQ
/ NSEC_PER_USEC
;
421 if (time_maxerror
> NTP_PHASE_LIMIT
) {
422 time_maxerror
= NTP_PHASE_LIMIT
;
423 time_status
|= STA_UNSYNC
;
426 /* Compute the phase adjustment for the next second */
427 tick_length
= tick_length_base
;
429 delta
= ntp_offset_chunk(time_offset
);
430 time_offset
-= delta
;
431 tick_length
+= delta
;
433 /* Check PPS signal */
439 if (time_adjust
> MAX_TICKADJ
) {
440 time_adjust
-= MAX_TICKADJ
;
441 tick_length
+= MAX_TICKADJ_SCALED
;
445 if (time_adjust
< -MAX_TICKADJ
) {
446 time_adjust
+= MAX_TICKADJ
;
447 tick_length
-= MAX_TICKADJ_SCALED
;
451 tick_length
+= (s64
)(time_adjust
* NSEC_PER_USEC
/ NTP_INTERVAL_FREQ
)
456 #ifdef CONFIG_GENERIC_CMOS_UPDATE
458 /* Disable the cmos update - used by virtualization and embedded */
459 int no_sync_cmos_clock __read_mostly
;
461 static void sync_cmos_clock(struct work_struct
*work
);
463 static DECLARE_DELAYED_WORK(sync_cmos_work
, sync_cmos_clock
);
465 static void sync_cmos_clock(struct work_struct
*work
)
467 struct timespec now
, next
;
471 * If we have an externally synchronized Linux clock, then update
472 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
473 * called as close as possible to 500 ms before the new second starts.
474 * This code is run on a timer. If the clock is set, that timer
475 * may not expire at the correct time. Thus, we adjust...
479 * Not synced, exit, do not restart a timer (if one is
480 * running, let it run out).
485 getnstimeofday(&now
);
486 if (abs(now
.tv_nsec
- (NSEC_PER_SEC
/ 2)) <= tick_nsec
/ 2)
487 fail
= update_persistent_clock(now
);
489 next
.tv_nsec
= (NSEC_PER_SEC
/ 2) - now
.tv_nsec
- (TICK_NSEC
/ 2);
490 if (next
.tv_nsec
<= 0)
491 next
.tv_nsec
+= NSEC_PER_SEC
;
498 if (next
.tv_nsec
>= NSEC_PER_SEC
) {
500 next
.tv_nsec
-= NSEC_PER_SEC
;
502 schedule_delayed_work(&sync_cmos_work
, timespec_to_jiffies(&next
));
505 static void notify_cmos_timer(void)
507 if (!no_sync_cmos_clock
)
508 schedule_delayed_work(&sync_cmos_work
, 0);
512 static inline void notify_cmos_timer(void) { }
516 * Start the leap seconds timer:
518 static inline void ntp_start_leap_timer(struct timespec
*ts
)
520 long now
= ts
->tv_sec
;
522 if (time_status
& STA_INS
) {
523 time_state
= TIME_INS
;
524 now
+= 86400 - now
% 86400;
525 hrtimer_start(&leap_timer
, ktime_set(now
, 0), HRTIMER_MODE_ABS
);
530 if (time_status
& STA_DEL
) {
531 time_state
= TIME_DEL
;
532 now
+= 86400 - (now
+ 1) % 86400;
533 hrtimer_start(&leap_timer
, ktime_set(now
, 0), HRTIMER_MODE_ABS
);
538 * Propagate a new txc->status value into the NTP state:
540 static inline void process_adj_status(struct timex
*txc
, struct timespec
*ts
)
542 if ((time_status
& STA_PLL
) && !(txc
->status
& STA_PLL
)) {
543 time_state
= TIME_OK
;
544 time_status
= STA_UNSYNC
;
545 /* restart PPS frequency calibration */
546 pps_reset_freq_interval();
550 * If we turn on PLL adjustments then reset the
551 * reference time to current time.
553 if (!(time_status
& STA_PLL
) && (txc
->status
& STA_PLL
))
554 time_reftime
= get_seconds();
556 /* only set allowed bits */
557 time_status
&= STA_RONLY
;
558 time_status
|= txc
->status
& ~STA_RONLY
;
560 switch (time_state
) {
562 ntp_start_leap_timer(ts
);
566 time_state
= TIME_OK
;
567 ntp_start_leap_timer(ts
);
569 if (!(time_status
& (STA_INS
| STA_DEL
)))
570 time_state
= TIME_OK
;
573 hrtimer_restart(&leap_timer
);
578 * Called with the xtime lock held, so we can access and modify
579 * all the global NTP state:
581 static inline void process_adjtimex_modes(struct timex
*txc
, struct timespec
*ts
)
583 if (txc
->modes
& ADJ_STATUS
)
584 process_adj_status(txc
, ts
);
586 if (txc
->modes
& ADJ_NANO
)
587 time_status
|= STA_NANO
;
589 if (txc
->modes
& ADJ_MICRO
)
590 time_status
&= ~STA_NANO
;
592 if (txc
->modes
& ADJ_FREQUENCY
) {
593 time_freq
= txc
->freq
* PPM_SCALE
;
594 time_freq
= min(time_freq
, MAXFREQ_SCALED
);
595 time_freq
= max(time_freq
, -MAXFREQ_SCALED
);
596 /* update pps_freq */
597 pps_set_freq(time_freq
);
600 if (txc
->modes
& ADJ_MAXERROR
)
601 time_maxerror
= txc
->maxerror
;
603 if (txc
->modes
& ADJ_ESTERROR
)
604 time_esterror
= txc
->esterror
;
606 if (txc
->modes
& ADJ_TIMECONST
) {
607 time_constant
= txc
->constant
;
608 if (!(time_status
& STA_NANO
))
610 time_constant
= min(time_constant
, (long)MAXTC
);
611 time_constant
= max(time_constant
, 0l);
614 if (txc
->modes
& ADJ_TAI
&& txc
->constant
> 0)
615 time_tai
= txc
->constant
;
617 if (txc
->modes
& ADJ_OFFSET
)
618 ntp_update_offset(txc
->offset
);
620 if (txc
->modes
& ADJ_TICK
)
621 tick_usec
= txc
->tick
;
623 if (txc
->modes
& (ADJ_TICK
|ADJ_FREQUENCY
|ADJ_OFFSET
))
624 ntp_update_frequency();
628 * adjtimex mainly allows reading (and writing, if superuser) of
629 * kernel time-keeping variables. used by xntpd.
631 int do_adjtimex(struct timex
*txc
)
636 /* Validate the data before disabling interrupts */
637 if (txc
->modes
& ADJ_ADJTIME
) {
638 /* singleshot must not be used with any other mode bits */
639 if (!(txc
->modes
& ADJ_OFFSET_SINGLESHOT
))
641 if (!(txc
->modes
& ADJ_OFFSET_READONLY
) &&
642 !capable(CAP_SYS_TIME
))
645 /* In order to modify anything, you gotta be super-user! */
646 if (txc
->modes
&& !capable(CAP_SYS_TIME
))
650 * if the quartz is off by more than 10% then
651 * something is VERY wrong!
653 if (txc
->modes
& ADJ_TICK
&&
654 (txc
->tick
< 900000/USER_HZ
||
655 txc
->tick
> 1100000/USER_HZ
))
658 if (txc
->modes
& ADJ_STATUS
&& time_state
!= TIME_OK
)
659 hrtimer_cancel(&leap_timer
);
662 if (txc
->modes
& ADJ_SETOFFSET
) {
663 struct timespec delta
;
664 delta
.tv_sec
= txc
->time
.tv_sec
;
665 delta
.tv_nsec
= txc
->time
.tv_usec
;
666 if (!capable(CAP_SYS_TIME
))
668 if (!(txc
->modes
& ADJ_NANO
))
669 delta
.tv_nsec
*= 1000;
670 result
= timekeeping_inject_offset(&delta
);
677 write_seqlock_irq(&xtime_lock
);
679 if (txc
->modes
& ADJ_ADJTIME
) {
680 long save_adjust
= time_adjust
;
682 if (!(txc
->modes
& ADJ_OFFSET_READONLY
)) {
683 /* adjtime() is independent from ntp_adjtime() */
684 time_adjust
= txc
->offset
;
685 ntp_update_frequency();
687 txc
->offset
= save_adjust
;
690 /* If there are input parameters, then process them: */
692 process_adjtimex_modes(txc
, &ts
);
694 txc
->offset
= shift_right(time_offset
* NTP_INTERVAL_FREQ
,
696 if (!(time_status
& STA_NANO
))
697 txc
->offset
/= NSEC_PER_USEC
;
700 result
= time_state
; /* mostly `TIME_OK' */
701 /* check for errors */
702 if (is_error_status(time_status
))
705 txc
->freq
= shift_right((time_freq
>> PPM_SCALE_INV_SHIFT
) *
706 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
707 txc
->maxerror
= time_maxerror
;
708 txc
->esterror
= time_esterror
;
709 txc
->status
= time_status
;
710 txc
->constant
= time_constant
;
712 txc
->tolerance
= MAXFREQ_SCALED
/ PPM_SCALE
;
713 txc
->tick
= tick_usec
;
716 /* fill PPS status fields */
719 write_sequnlock_irq(&xtime_lock
);
721 txc
->time
.tv_sec
= ts
.tv_sec
;
722 txc
->time
.tv_usec
= ts
.tv_nsec
;
723 if (!(time_status
& STA_NANO
))
724 txc
->time
.tv_usec
/= NSEC_PER_USEC
;
731 #ifdef CONFIG_NTP_PPS
733 /* actually struct pps_normtime is good old struct timespec, but it is
734 * semantically different (and it is the reason why it was invented):
735 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
736 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
737 struct pps_normtime
{
738 __kernel_time_t sec
; /* seconds */
739 long nsec
; /* nanoseconds */
742 /* normalize the timestamp so that nsec is in the
743 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
744 static inline struct pps_normtime
pps_normalize_ts(struct timespec ts
)
746 struct pps_normtime norm
= {
751 if (norm
.nsec
> (NSEC_PER_SEC
>> 1)) {
752 norm
.nsec
-= NSEC_PER_SEC
;
759 /* get current phase correction and jitter */
760 static inline long pps_phase_filter_get(long *jitter
)
762 *jitter
= pps_tf
[0] - pps_tf
[1];
766 /* TODO: test various filters */
770 /* add the sample to the phase filter */
771 static inline void pps_phase_filter_add(long err
)
773 pps_tf
[2] = pps_tf
[1];
774 pps_tf
[1] = pps_tf
[0];
778 /* decrease frequency calibration interval length.
779 * It is halved after four consecutive unstable intervals.
781 static inline void pps_dec_freq_interval(void)
783 if (--pps_intcnt
<= -PPS_INTCOUNT
) {
784 pps_intcnt
= -PPS_INTCOUNT
;
785 if (pps_shift
> PPS_INTMIN
) {
792 /* increase frequency calibration interval length.
793 * It is doubled after four consecutive stable intervals.
795 static inline void pps_inc_freq_interval(void)
797 if (++pps_intcnt
>= PPS_INTCOUNT
) {
798 pps_intcnt
= PPS_INTCOUNT
;
799 if (pps_shift
< PPS_INTMAX
) {
806 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
809 * At the end of the calibration interval the difference between the
810 * first and last MONOTONIC_RAW clock timestamps divided by the length
811 * of the interval becomes the frequency update. If the interval was
812 * too long, the data are discarded.
813 * Returns the difference between old and new frequency values.
815 static long hardpps_update_freq(struct pps_normtime freq_norm
)
817 long delta
, delta_mod
;
820 /* check if the frequency interval was too long */
821 if (freq_norm
.sec
> (2 << pps_shift
)) {
822 time_status
|= STA_PPSERROR
;
824 pps_dec_freq_interval();
825 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
830 /* here the raw frequency offset and wander (stability) is
831 * calculated. If the wander is less than the wander threshold
832 * the interval is increased; otherwise it is decreased.
834 ftemp
= div_s64(((s64
)(-freq_norm
.nsec
)) << NTP_SCALE_SHIFT
,
836 delta
= shift_right(ftemp
- pps_freq
, NTP_SCALE_SHIFT
);
838 if (delta
> PPS_MAXWANDER
|| delta
< -PPS_MAXWANDER
) {
839 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta
);
840 time_status
|= STA_PPSWANDER
;
842 pps_dec_freq_interval();
843 } else { /* good sample */
844 pps_inc_freq_interval();
847 /* the stability metric is calculated as the average of recent
848 * frequency changes, but is used only for performance
853 delta_mod
= -delta_mod
;
854 pps_stabil
+= (div_s64(((s64
)delta_mod
) <<
855 (NTP_SCALE_SHIFT
- SHIFT_USEC
),
856 NSEC_PER_USEC
) - pps_stabil
) >> PPS_INTMIN
;
858 /* if enabled, the system clock frequency is updated */
859 if ((time_status
& STA_PPSFREQ
) != 0 &&
860 (time_status
& STA_FREQHOLD
) == 0) {
861 time_freq
= pps_freq
;
862 ntp_update_frequency();
868 /* correct REALTIME clock phase error against PPS signal */
869 static void hardpps_update_phase(long error
)
871 long correction
= -error
;
874 /* add the sample to the median filter */
875 pps_phase_filter_add(correction
);
876 correction
= pps_phase_filter_get(&jitter
);
878 /* Nominal jitter is due to PPS signal noise. If it exceeds the
879 * threshold, the sample is discarded; otherwise, if so enabled,
880 * the time offset is updated.
882 if (jitter
> (pps_jitter
<< PPS_POPCORN
)) {
883 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
884 jitter
, (pps_jitter
<< PPS_POPCORN
));
885 time_status
|= STA_PPSJITTER
;
887 } else if (time_status
& STA_PPSTIME
) {
888 /* correct the time using the phase offset */
889 time_offset
= div_s64(((s64
)correction
) << NTP_SCALE_SHIFT
,
891 /* cancel running adjtime() */
895 pps_jitter
+= (jitter
- pps_jitter
) >> PPS_INTMIN
;
899 * hardpps() - discipline CPU clock oscillator to external PPS signal
901 * This routine is called at each PPS signal arrival in order to
902 * discipline the CPU clock oscillator to the PPS signal. It takes two
903 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
904 * is used to correct clock phase error and the latter is used to
905 * correct the frequency.
907 * This code is based on David Mills's reference nanokernel
908 * implementation. It was mostly rewritten but keeps the same idea.
910 void hardpps(const struct timespec
*phase_ts
, const struct timespec
*raw_ts
)
912 struct pps_normtime pts_norm
, freq_norm
;
915 pts_norm
= pps_normalize_ts(*phase_ts
);
917 write_seqlock_irqsave(&xtime_lock
, flags
);
919 /* clear the error bits, they will be set again if needed */
920 time_status
&= ~(STA_PPSJITTER
| STA_PPSWANDER
| STA_PPSERROR
);
922 /* indicate signal presence */
923 time_status
|= STA_PPSSIGNAL
;
924 pps_valid
= PPS_VALID
;
926 /* when called for the first time,
927 * just start the frequency interval */
928 if (unlikely(pps_fbase
.tv_sec
== 0)) {
930 write_sequnlock_irqrestore(&xtime_lock
, flags
);
934 /* ok, now we have a base for frequency calculation */
935 freq_norm
= pps_normalize_ts(timespec_sub(*raw_ts
, pps_fbase
));
937 /* check that the signal is in the range
938 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
939 if ((freq_norm
.sec
== 0) ||
940 (freq_norm
.nsec
> MAXFREQ
* freq_norm
.sec
) ||
941 (freq_norm
.nsec
< -MAXFREQ
* freq_norm
.sec
)) {
942 time_status
|= STA_PPSJITTER
;
943 /* restart the frequency calibration interval */
945 write_sequnlock_irqrestore(&xtime_lock
, flags
);
946 pr_err("hardpps: PPSJITTER: bad pulse\n");
952 /* check if the current frequency interval is finished */
953 if (freq_norm
.sec
>= (1 << pps_shift
)) {
955 /* restart the frequency calibration interval */
957 hardpps_update_freq(freq_norm
);
960 hardpps_update_phase(pts_norm
.nsec
);
962 write_sequnlock_irqrestore(&xtime_lock
, flags
);
964 EXPORT_SYMBOL(hardpps
);
966 #endif /* CONFIG_NTP_PPS */
968 static int __init
ntp_tick_adj_setup(char *str
)
970 ntp_tick_adj
= simple_strtol(str
, NULL
, 0);
971 ntp_tick_adj
<<= NTP_SCALE_SHIFT
;
976 __setup("ntp_tick_adj=", ntp_tick_adj_setup
);
978 void __init
ntp_init(void)
981 hrtimer_init(&leap_timer
, CLOCK_REALTIME
, HRTIMER_MODE_ABS
);
982 leap_timer
.function
= ntp_leap_second
;