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 DEFINE_SPINLOCK(ntp_lock
);
28 /* USER_HZ period (usecs): */
29 unsigned long tick_usec
= TICK_USEC
;
31 /* ACTHZ period (nsecs): */
32 unsigned long tick_nsec
;
34 static u64 tick_length
;
35 static u64 tick_length_base
;
37 static struct hrtimer leap_timer
;
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 /* TAI offset (secs): */
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 long time_reftime
;
78 static long time_adjust
;
80 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
81 static s64 ntp_tick_adj
;
86 * The following variables are used when a pulse-per-second (PPS) signal
87 * is available. They establish the engineering parameters of the clock
88 * discipline loop when controlled by the PPS signal.
90 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
91 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
92 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
93 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
94 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
95 increase pps_shift or consecutive bad
96 intervals to decrease it */
97 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
99 static int pps_valid
; /* signal watchdog counter */
100 static long pps_tf
[3]; /* phase median filter */
101 static long pps_jitter
; /* current jitter (ns) */
102 static struct timespec pps_fbase
; /* beginning of the last freq interval */
103 static int pps_shift
; /* current interval duration (s) (shift) */
104 static int pps_intcnt
; /* interval counter */
105 static s64 pps_freq
; /* frequency offset (scaled ns/s) */
106 static long pps_stabil
; /* current stability (scaled ns/s) */
109 * PPS signal quality monitors
111 static long pps_calcnt
; /* calibration intervals */
112 static long pps_jitcnt
; /* jitter limit exceeded */
113 static long pps_stbcnt
; /* stability limit exceeded */
114 static long pps_errcnt
; /* calibration errors */
117 /* PPS kernel consumer compensates the whole phase error immediately.
118 * Otherwise, reduce the offset by a fixed factor times the time constant.
120 static inline s64
ntp_offset_chunk(s64 offset
)
122 if (time_status
& STA_PPSTIME
&& time_status
& STA_PPSSIGNAL
)
125 return shift_right(offset
, SHIFT_PLL
+ time_constant
);
128 static inline void pps_reset_freq_interval(void)
130 /* the PPS calibration interval may end
131 surprisingly early */
132 pps_shift
= PPS_INTMIN
;
137 * pps_clear - Clears the PPS state variables
139 * Must be called while holding a write on the ntp_lock
141 static inline void pps_clear(void)
143 pps_reset_freq_interval();
147 pps_fbase
.tv_sec
= pps_fbase
.tv_nsec
= 0;
151 /* Decrease pps_valid to indicate that another second has passed since
152 * the last PPS signal. When it reaches 0, indicate that PPS signal is
155 * Must be called while holding a write on the ntp_lock
157 static inline void pps_dec_valid(void)
162 time_status
&= ~(STA_PPSSIGNAL
| STA_PPSJITTER
|
163 STA_PPSWANDER
| STA_PPSERROR
);
168 static inline void pps_set_freq(s64 freq
)
173 static inline int is_error_status(int status
)
175 return (time_status
& (STA_UNSYNC
|STA_CLOCKERR
))
176 /* PPS signal lost when either PPS time or
177 * PPS frequency synchronization requested
179 || ((time_status
& (STA_PPSFREQ
|STA_PPSTIME
))
180 && !(time_status
& STA_PPSSIGNAL
))
181 /* PPS jitter exceeded when
182 * PPS time synchronization requested */
183 || ((time_status
& (STA_PPSTIME
|STA_PPSJITTER
))
184 == (STA_PPSTIME
|STA_PPSJITTER
))
185 /* PPS wander exceeded or calibration error when
186 * PPS frequency synchronization requested
188 || ((time_status
& STA_PPSFREQ
)
189 && (time_status
& (STA_PPSWANDER
|STA_PPSERROR
)));
192 static inline void pps_fill_timex(struct timex
*txc
)
194 txc
->ppsfreq
= shift_right((pps_freq
>> PPM_SCALE_INV_SHIFT
) *
195 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
196 txc
->jitter
= pps_jitter
;
197 if (!(time_status
& STA_NANO
))
198 txc
->jitter
/= NSEC_PER_USEC
;
199 txc
->shift
= pps_shift
;
200 txc
->stabil
= pps_stabil
;
201 txc
->jitcnt
= pps_jitcnt
;
202 txc
->calcnt
= pps_calcnt
;
203 txc
->errcnt
= pps_errcnt
;
204 txc
->stbcnt
= pps_stbcnt
;
207 #else /* !CONFIG_NTP_PPS */
209 static inline s64
ntp_offset_chunk(s64 offset
)
211 return shift_right(offset
, SHIFT_PLL
+ time_constant
);
214 static inline void pps_reset_freq_interval(void) {}
215 static inline void pps_clear(void) {}
216 static inline void pps_dec_valid(void) {}
217 static inline void pps_set_freq(s64 freq
) {}
219 static inline int is_error_status(int status
)
221 return status
& (STA_UNSYNC
|STA_CLOCKERR
);
224 static inline void pps_fill_timex(struct timex
*txc
)
226 /* PPS is not implemented, so these are zero */
237 #endif /* CONFIG_NTP_PPS */
241 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
244 static inline int ntp_synced(void)
246 return !(time_status
& STA_UNSYNC
);
255 * Update (tick_length, tick_length_base, tick_nsec), based
256 * on (tick_usec, ntp_tick_adj, time_freq):
258 static void ntp_update_frequency(void)
263 second_length
= (u64
)(tick_usec
* NSEC_PER_USEC
* USER_HZ
)
266 second_length
+= ntp_tick_adj
;
267 second_length
+= time_freq
;
269 tick_nsec
= div_u64(second_length
, HZ
) >> NTP_SCALE_SHIFT
;
270 new_base
= div_u64(second_length
, NTP_INTERVAL_FREQ
);
273 * Don't wait for the next second_overflow, apply
274 * the change to the tick length immediately:
276 tick_length
+= new_base
- tick_length_base
;
277 tick_length_base
= new_base
;
280 static inline s64
ntp_update_offset_fll(s64 offset64
, long secs
)
282 time_status
&= ~STA_MODE
;
287 if (!(time_status
& STA_FLL
) && (secs
<= MAXSEC
))
290 time_status
|= STA_MODE
;
292 return div_s64(offset64
<< (NTP_SCALE_SHIFT
- SHIFT_FLL
), secs
);
295 static void ntp_update_offset(long offset
)
301 if (!(time_status
& STA_PLL
))
304 if (!(time_status
& STA_NANO
))
305 offset
*= NSEC_PER_USEC
;
308 * Scale the phase adjustment and
309 * clamp to the operating range.
311 offset
= min(offset
, MAXPHASE
);
312 offset
= max(offset
, -MAXPHASE
);
315 * Select how the frequency is to be controlled
316 * and in which mode (PLL or FLL).
318 secs
= get_seconds() - time_reftime
;
319 if (unlikely(time_status
& STA_FREQHOLD
))
322 time_reftime
= get_seconds();
325 freq_adj
= ntp_update_offset_fll(offset64
, secs
);
328 * Clamp update interval to reduce PLL gain with low
329 * sampling rate (e.g. intermittent network connection)
330 * to avoid instability.
332 if (unlikely(secs
> 1 << (SHIFT_PLL
+ 1 + time_constant
)))
333 secs
= 1 << (SHIFT_PLL
+ 1 + time_constant
);
335 freq_adj
+= (offset64
* secs
) <<
336 (NTP_SCALE_SHIFT
- 2 * (SHIFT_PLL
+ 2 + time_constant
));
338 freq_adj
= min(freq_adj
+ time_freq
, MAXFREQ_SCALED
);
340 time_freq
= max(freq_adj
, -MAXFREQ_SCALED
);
342 time_offset
= div_s64(offset64
<< NTP_SCALE_SHIFT
, NTP_INTERVAL_FREQ
);
346 * ntp_clear - Clears the NTP state variables
352 spin_lock_irqsave(&ntp_lock
, flags
);
354 time_adjust
= 0; /* stop active adjtime() */
355 time_status
|= STA_UNSYNC
;
356 time_maxerror
= NTP_PHASE_LIMIT
;
357 time_esterror
= NTP_PHASE_LIMIT
;
359 ntp_update_frequency();
361 tick_length
= tick_length_base
;
364 /* Clear PPS state variables */
366 spin_unlock_irqrestore(&ntp_lock
, flags
);
371 u64
ntp_tick_length(void)
376 spin_lock_irqsave(&ntp_lock
, flags
);
378 spin_unlock_irqrestore(&ntp_lock
, flags
);
384 * Leap second processing. If in leap-insert state at the end of the
385 * day, the system clock is set back one second; if in leap-delete
386 * state, the system clock is set ahead one second.
388 static enum hrtimer_restart
ntp_leap_second(struct hrtimer
*timer
)
390 enum hrtimer_restart res
= HRTIMER_NORESTART
;
394 spin_lock_irqsave(&ntp_lock
, flags
);
395 switch (time_state
) {
400 time_state
= TIME_OOP
;
402 "Clock: inserting leap second 23:59:60 UTC\n");
403 hrtimer_add_expires_ns(&leap_timer
, NSEC_PER_SEC
);
404 res
= HRTIMER_RESTART
;
409 time_state
= TIME_WAIT
;
411 "Clock: deleting leap second 23:59:59 UTC\n");
415 time_state
= TIME_WAIT
;
418 if (!(time_status
& (STA_INS
| STA_DEL
)))
419 time_state
= TIME_OK
;
422 spin_unlock_irqrestore(&ntp_lock
, flags
);
425 * We have to call this outside of the ntp_lock to keep
426 * the proper locking hierarchy
429 timekeeping_leap_insert(leap
);
435 * this routine handles the overflow of the microsecond field
437 * The tricky bits of code to handle the accurate clock support
438 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
439 * They were originally developed for SUN and DEC kernels.
440 * All the kudos should go to Dave for this stuff.
442 void second_overflow(void)
447 spin_lock_irqsave(&ntp_lock
, flags
);
449 /* Bump the maxerror field */
450 time_maxerror
+= MAXFREQ
/ NSEC_PER_USEC
;
451 if (time_maxerror
> NTP_PHASE_LIMIT
) {
452 time_maxerror
= NTP_PHASE_LIMIT
;
453 time_status
|= STA_UNSYNC
;
456 /* Compute the phase adjustment for the next second */
457 tick_length
= tick_length_base
;
459 delta
= ntp_offset_chunk(time_offset
);
460 time_offset
-= delta
;
461 tick_length
+= delta
;
463 /* Check PPS signal */
469 if (time_adjust
> MAX_TICKADJ
) {
470 time_adjust
-= MAX_TICKADJ
;
471 tick_length
+= MAX_TICKADJ_SCALED
;
475 if (time_adjust
< -MAX_TICKADJ
) {
476 time_adjust
+= MAX_TICKADJ
;
477 tick_length
-= MAX_TICKADJ_SCALED
;
481 tick_length
+= (s64
)(time_adjust
* NSEC_PER_USEC
/ NTP_INTERVAL_FREQ
)
485 spin_unlock_irqrestore(&ntp_lock
, flags
);
488 #ifdef CONFIG_GENERIC_CMOS_UPDATE
490 /* Disable the cmos update - used by virtualization and embedded */
491 int no_sync_cmos_clock __read_mostly
;
493 static void sync_cmos_clock(struct work_struct
*work
);
495 static DECLARE_DELAYED_WORK(sync_cmos_work
, sync_cmos_clock
);
497 static void sync_cmos_clock(struct work_struct
*work
)
499 struct timespec now
, next
;
503 * If we have an externally synchronized Linux clock, then update
504 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
505 * called as close as possible to 500 ms before the new second starts.
506 * This code is run on a timer. If the clock is set, that timer
507 * may not expire at the correct time. Thus, we adjust...
511 * Not synced, exit, do not restart a timer (if one is
512 * running, let it run out).
517 getnstimeofday(&now
);
518 if (abs(now
.tv_nsec
- (NSEC_PER_SEC
/ 2)) <= tick_nsec
/ 2)
519 fail
= update_persistent_clock(now
);
521 next
.tv_nsec
= (NSEC_PER_SEC
/ 2) - now
.tv_nsec
- (TICK_NSEC
/ 2);
522 if (next
.tv_nsec
<= 0)
523 next
.tv_nsec
+= NSEC_PER_SEC
;
530 if (next
.tv_nsec
>= NSEC_PER_SEC
) {
532 next
.tv_nsec
-= NSEC_PER_SEC
;
534 schedule_delayed_work(&sync_cmos_work
, timespec_to_jiffies(&next
));
537 static void notify_cmos_timer(void)
539 if (!no_sync_cmos_clock
)
540 schedule_delayed_work(&sync_cmos_work
, 0);
544 static inline void notify_cmos_timer(void) { }
548 * Start the leap seconds timer:
550 static inline void ntp_start_leap_timer(struct timespec
*ts
)
552 long now
= ts
->tv_sec
;
554 if (time_status
& STA_INS
) {
555 time_state
= TIME_INS
;
556 now
+= 86400 - now
% 86400;
557 hrtimer_start(&leap_timer
, ktime_set(now
, 0), HRTIMER_MODE_ABS
);
562 if (time_status
& STA_DEL
) {
563 time_state
= TIME_DEL
;
564 now
+= 86400 - (now
+ 1) % 86400;
565 hrtimer_start(&leap_timer
, ktime_set(now
, 0), HRTIMER_MODE_ABS
);
570 * Propagate a new txc->status value into the NTP state:
572 static inline void process_adj_status(struct timex
*txc
, struct timespec
*ts
)
574 if ((time_status
& STA_PLL
) && !(txc
->status
& STA_PLL
)) {
575 time_state
= TIME_OK
;
576 time_status
= STA_UNSYNC
;
577 /* restart PPS frequency calibration */
578 pps_reset_freq_interval();
582 * If we turn on PLL adjustments then reset the
583 * reference time to current time.
585 if (!(time_status
& STA_PLL
) && (txc
->status
& STA_PLL
))
586 time_reftime
= get_seconds();
588 /* only set allowed bits */
589 time_status
&= STA_RONLY
;
590 time_status
|= txc
->status
& ~STA_RONLY
;
592 switch (time_state
) {
594 ntp_start_leap_timer(ts
);
598 time_state
= TIME_OK
;
599 ntp_start_leap_timer(ts
);
601 if (!(time_status
& (STA_INS
| STA_DEL
)))
602 time_state
= TIME_OK
;
605 hrtimer_restart(&leap_timer
);
610 * Called with the xtime lock held, so we can access and modify
611 * all the global NTP state:
613 static inline void process_adjtimex_modes(struct timex
*txc
, struct timespec
*ts
)
615 if (txc
->modes
& ADJ_STATUS
)
616 process_adj_status(txc
, ts
);
618 if (txc
->modes
& ADJ_NANO
)
619 time_status
|= STA_NANO
;
621 if (txc
->modes
& ADJ_MICRO
)
622 time_status
&= ~STA_NANO
;
624 if (txc
->modes
& ADJ_FREQUENCY
) {
625 time_freq
= txc
->freq
* PPM_SCALE
;
626 time_freq
= min(time_freq
, MAXFREQ_SCALED
);
627 time_freq
= max(time_freq
, -MAXFREQ_SCALED
);
628 /* update pps_freq */
629 pps_set_freq(time_freq
);
632 if (txc
->modes
& ADJ_MAXERROR
)
633 time_maxerror
= txc
->maxerror
;
635 if (txc
->modes
& ADJ_ESTERROR
)
636 time_esterror
= txc
->esterror
;
638 if (txc
->modes
& ADJ_TIMECONST
) {
639 time_constant
= txc
->constant
;
640 if (!(time_status
& STA_NANO
))
642 time_constant
= min(time_constant
, (long)MAXTC
);
643 time_constant
= max(time_constant
, 0l);
646 if (txc
->modes
& ADJ_TAI
&& txc
->constant
> 0)
647 time_tai
= txc
->constant
;
649 if (txc
->modes
& ADJ_OFFSET
)
650 ntp_update_offset(txc
->offset
);
652 if (txc
->modes
& ADJ_TICK
)
653 tick_usec
= txc
->tick
;
655 if (txc
->modes
& (ADJ_TICK
|ADJ_FREQUENCY
|ADJ_OFFSET
))
656 ntp_update_frequency();
660 * adjtimex mainly allows reading (and writing, if superuser) of
661 * kernel time-keeping variables. used by xntpd.
663 int do_adjtimex(struct timex
*txc
)
668 /* Validate the data before disabling interrupts */
669 if (txc
->modes
& ADJ_ADJTIME
) {
670 /* singleshot must not be used with any other mode bits */
671 if (!(txc
->modes
& ADJ_OFFSET_SINGLESHOT
))
673 if (!(txc
->modes
& ADJ_OFFSET_READONLY
) &&
674 !capable(CAP_SYS_TIME
))
677 /* In order to modify anything, you gotta be super-user! */
678 if (txc
->modes
&& !capable(CAP_SYS_TIME
))
682 * if the quartz is off by more than 10% then
683 * something is VERY wrong!
685 if (txc
->modes
& ADJ_TICK
&&
686 (txc
->tick
< 900000/USER_HZ
||
687 txc
->tick
> 1100000/USER_HZ
))
690 if (txc
->modes
& ADJ_STATUS
&& time_state
!= TIME_OK
)
691 hrtimer_cancel(&leap_timer
);
694 if (txc
->modes
& ADJ_SETOFFSET
) {
695 struct timespec delta
;
696 delta
.tv_sec
= txc
->time
.tv_sec
;
697 delta
.tv_nsec
= txc
->time
.tv_usec
;
698 if (!capable(CAP_SYS_TIME
))
700 if (!(txc
->modes
& ADJ_NANO
))
701 delta
.tv_nsec
*= 1000;
702 result
= timekeeping_inject_offset(&delta
);
709 spin_lock_irq(&ntp_lock
);
711 if (txc
->modes
& ADJ_ADJTIME
) {
712 long save_adjust
= time_adjust
;
714 if (!(txc
->modes
& ADJ_OFFSET_READONLY
)) {
715 /* adjtime() is independent from ntp_adjtime() */
716 time_adjust
= txc
->offset
;
717 ntp_update_frequency();
719 txc
->offset
= save_adjust
;
722 /* If there are input parameters, then process them: */
724 process_adjtimex_modes(txc
, &ts
);
726 txc
->offset
= shift_right(time_offset
* NTP_INTERVAL_FREQ
,
728 if (!(time_status
& STA_NANO
))
729 txc
->offset
/= NSEC_PER_USEC
;
732 result
= time_state
; /* mostly `TIME_OK' */
733 /* check for errors */
734 if (is_error_status(time_status
))
737 txc
->freq
= shift_right((time_freq
>> PPM_SCALE_INV_SHIFT
) *
738 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
739 txc
->maxerror
= time_maxerror
;
740 txc
->esterror
= time_esterror
;
741 txc
->status
= time_status
;
742 txc
->constant
= time_constant
;
744 txc
->tolerance
= MAXFREQ_SCALED
/ PPM_SCALE
;
745 txc
->tick
= tick_usec
;
748 /* fill PPS status fields */
751 spin_unlock_irq(&ntp_lock
);
753 txc
->time
.tv_sec
= ts
.tv_sec
;
754 txc
->time
.tv_usec
= ts
.tv_nsec
;
755 if (!(time_status
& STA_NANO
))
756 txc
->time
.tv_usec
/= NSEC_PER_USEC
;
763 #ifdef CONFIG_NTP_PPS
765 /* actually struct pps_normtime is good old struct timespec, but it is
766 * semantically different (and it is the reason why it was invented):
767 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
768 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
769 struct pps_normtime
{
770 __kernel_time_t sec
; /* seconds */
771 long nsec
; /* nanoseconds */
774 /* normalize the timestamp so that nsec is in the
775 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
776 static inline struct pps_normtime
pps_normalize_ts(struct timespec ts
)
778 struct pps_normtime norm
= {
783 if (norm
.nsec
> (NSEC_PER_SEC
>> 1)) {
784 norm
.nsec
-= NSEC_PER_SEC
;
791 /* get current phase correction and jitter */
792 static inline long pps_phase_filter_get(long *jitter
)
794 *jitter
= pps_tf
[0] - pps_tf
[1];
798 /* TODO: test various filters */
802 /* add the sample to the phase filter */
803 static inline void pps_phase_filter_add(long err
)
805 pps_tf
[2] = pps_tf
[1];
806 pps_tf
[1] = pps_tf
[0];
810 /* decrease frequency calibration interval length.
811 * It is halved after four consecutive unstable intervals.
813 static inline void pps_dec_freq_interval(void)
815 if (--pps_intcnt
<= -PPS_INTCOUNT
) {
816 pps_intcnt
= -PPS_INTCOUNT
;
817 if (pps_shift
> PPS_INTMIN
) {
824 /* increase frequency calibration interval length.
825 * It is doubled after four consecutive stable intervals.
827 static inline void pps_inc_freq_interval(void)
829 if (++pps_intcnt
>= PPS_INTCOUNT
) {
830 pps_intcnt
= PPS_INTCOUNT
;
831 if (pps_shift
< PPS_INTMAX
) {
838 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
841 * At the end of the calibration interval the difference between the
842 * first and last MONOTONIC_RAW clock timestamps divided by the length
843 * of the interval becomes the frequency update. If the interval was
844 * too long, the data are discarded.
845 * Returns the difference between old and new frequency values.
847 static long hardpps_update_freq(struct pps_normtime freq_norm
)
849 long delta
, delta_mod
;
852 /* check if the frequency interval was too long */
853 if (freq_norm
.sec
> (2 << pps_shift
)) {
854 time_status
|= STA_PPSERROR
;
856 pps_dec_freq_interval();
857 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
862 /* here the raw frequency offset and wander (stability) is
863 * calculated. If the wander is less than the wander threshold
864 * the interval is increased; otherwise it is decreased.
866 ftemp
= div_s64(((s64
)(-freq_norm
.nsec
)) << NTP_SCALE_SHIFT
,
868 delta
= shift_right(ftemp
- pps_freq
, NTP_SCALE_SHIFT
);
870 if (delta
> PPS_MAXWANDER
|| delta
< -PPS_MAXWANDER
) {
871 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta
);
872 time_status
|= STA_PPSWANDER
;
874 pps_dec_freq_interval();
875 } else { /* good sample */
876 pps_inc_freq_interval();
879 /* the stability metric is calculated as the average of recent
880 * frequency changes, but is used only for performance
885 delta_mod
= -delta_mod
;
886 pps_stabil
+= (div_s64(((s64
)delta_mod
) <<
887 (NTP_SCALE_SHIFT
- SHIFT_USEC
),
888 NSEC_PER_USEC
) - pps_stabil
) >> PPS_INTMIN
;
890 /* if enabled, the system clock frequency is updated */
891 if ((time_status
& STA_PPSFREQ
) != 0 &&
892 (time_status
& STA_FREQHOLD
) == 0) {
893 time_freq
= pps_freq
;
894 ntp_update_frequency();
900 /* correct REALTIME clock phase error against PPS signal */
901 static void hardpps_update_phase(long error
)
903 long correction
= -error
;
906 /* add the sample to the median filter */
907 pps_phase_filter_add(correction
);
908 correction
= pps_phase_filter_get(&jitter
);
910 /* Nominal jitter is due to PPS signal noise. If it exceeds the
911 * threshold, the sample is discarded; otherwise, if so enabled,
912 * the time offset is updated.
914 if (jitter
> (pps_jitter
<< PPS_POPCORN
)) {
915 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
916 jitter
, (pps_jitter
<< PPS_POPCORN
));
917 time_status
|= STA_PPSJITTER
;
919 } else if (time_status
& STA_PPSTIME
) {
920 /* correct the time using the phase offset */
921 time_offset
= div_s64(((s64
)correction
) << NTP_SCALE_SHIFT
,
923 /* cancel running adjtime() */
927 pps_jitter
+= (jitter
- pps_jitter
) >> PPS_INTMIN
;
931 * hardpps() - discipline CPU clock oscillator to external PPS signal
933 * This routine is called at each PPS signal arrival in order to
934 * discipline the CPU clock oscillator to the PPS signal. It takes two
935 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
936 * is used to correct clock phase error and the latter is used to
937 * correct the frequency.
939 * This code is based on David Mills's reference nanokernel
940 * implementation. It was mostly rewritten but keeps the same idea.
942 void hardpps(const struct timespec
*phase_ts
, const struct timespec
*raw_ts
)
944 struct pps_normtime pts_norm
, freq_norm
;
947 pts_norm
= pps_normalize_ts(*phase_ts
);
949 spin_lock_irqsave(&ntp_lock
, flags
);
951 /* clear the error bits, they will be set again if needed */
952 time_status
&= ~(STA_PPSJITTER
| STA_PPSWANDER
| STA_PPSERROR
);
954 /* indicate signal presence */
955 time_status
|= STA_PPSSIGNAL
;
956 pps_valid
= PPS_VALID
;
958 /* when called for the first time,
959 * just start the frequency interval */
960 if (unlikely(pps_fbase
.tv_sec
== 0)) {
962 spin_unlock_irqrestore(&ntp_lock
, flags
);
966 /* ok, now we have a base for frequency calculation */
967 freq_norm
= pps_normalize_ts(timespec_sub(*raw_ts
, pps_fbase
));
969 /* check that the signal is in the range
970 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
971 if ((freq_norm
.sec
== 0) ||
972 (freq_norm
.nsec
> MAXFREQ
* freq_norm
.sec
) ||
973 (freq_norm
.nsec
< -MAXFREQ
* freq_norm
.sec
)) {
974 time_status
|= STA_PPSJITTER
;
975 /* restart the frequency calibration interval */
977 spin_unlock_irqrestore(&ntp_lock
, flags
);
978 pr_err("hardpps: PPSJITTER: bad pulse\n");
984 /* check if the current frequency interval is finished */
985 if (freq_norm
.sec
>= (1 << pps_shift
)) {
987 /* restart the frequency calibration interval */
989 hardpps_update_freq(freq_norm
);
992 hardpps_update_phase(pts_norm
.nsec
);
994 spin_unlock_irqrestore(&ntp_lock
, flags
);
996 EXPORT_SYMBOL(hardpps
);
998 #endif /* CONFIG_NTP_PPS */
1000 static int __init
ntp_tick_adj_setup(char *str
)
1002 ntp_tick_adj
= simple_strtol(str
, NULL
, 0);
1003 ntp_tick_adj
<<= NTP_SCALE_SHIFT
;
1008 __setup("ntp_tick_adj=", ntp_tick_adj_setup
);
1010 void __init
ntp_init(void)
1013 hrtimer_init(&leap_timer
, CLOCK_REALTIME
, HRTIMER_MODE_ABS
);
1014 leap_timer
.function
= ntp_leap_second
;