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"
23 * NTP timekeeping variables:
26 DEFINE_RAW_SPINLOCK(ntp_lock
);
29 /* USER_HZ period (usecs): */
30 unsigned long tick_usec
= TICK_USEC
;
32 /* SHIFTED_HZ period (nsecs): */
33 unsigned long tick_nsec
;
35 static u64 tick_length
;
36 static u64 tick_length_base
;
38 #define MAX_TICKADJ 500LL /* usecs */
39 #define MAX_TICKADJ_SCALED \
40 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
43 * phase-lock loop variables
47 * clock synchronization status
49 * (TIME_ERROR prevents overwriting the CMOS clock)
51 static int time_state
= TIME_OK
;
53 /* clock status bits: */
54 static int time_status
= STA_UNSYNC
;
56 /* time adjustment (nsecs): */
57 static s64 time_offset
;
59 /* pll time constant: */
60 static long time_constant
= 2;
62 /* maximum error (usecs): */
63 static long time_maxerror
= NTP_PHASE_LIMIT
;
65 /* estimated error (usecs): */
66 static long time_esterror
= NTP_PHASE_LIMIT
;
68 /* frequency offset (scaled nsecs/secs): */
71 /* time at last adjustment (secs): */
72 static long time_reftime
;
74 static long time_adjust
;
76 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
77 static s64 ntp_tick_adj
;
82 * The following variables are used when a pulse-per-second (PPS) signal
83 * is available. They establish the engineering parameters of the clock
84 * discipline loop when controlled by the PPS signal.
86 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
87 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
88 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
89 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
90 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
91 increase pps_shift or consecutive bad
92 intervals to decrease it */
93 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
95 static int pps_valid
; /* signal watchdog counter */
96 static long pps_tf
[3]; /* phase median filter */
97 static long pps_jitter
; /* current jitter (ns) */
98 static struct timespec pps_fbase
; /* beginning of the last freq interval */
99 static int pps_shift
; /* current interval duration (s) (shift) */
100 static int pps_intcnt
; /* interval counter */
101 static s64 pps_freq
; /* frequency offset (scaled ns/s) */
102 static long pps_stabil
; /* current stability (scaled ns/s) */
105 * PPS signal quality monitors
107 static long pps_calcnt
; /* calibration intervals */
108 static long pps_jitcnt
; /* jitter limit exceeded */
109 static long pps_stbcnt
; /* stability limit exceeded */
110 static long pps_errcnt
; /* calibration errors */
113 /* PPS kernel consumer compensates the whole phase error immediately.
114 * Otherwise, reduce the offset by a fixed factor times the time constant.
116 static inline s64
ntp_offset_chunk(s64 offset
)
118 if (time_status
& STA_PPSTIME
&& time_status
& STA_PPSSIGNAL
)
121 return shift_right(offset
, SHIFT_PLL
+ time_constant
);
124 static inline void pps_reset_freq_interval(void)
126 /* the PPS calibration interval may end
127 surprisingly early */
128 pps_shift
= PPS_INTMIN
;
133 * pps_clear - Clears the PPS state variables
135 * Must be called while holding a write on the ntp_lock
137 static inline void pps_clear(void)
139 pps_reset_freq_interval();
143 pps_fbase
.tv_sec
= pps_fbase
.tv_nsec
= 0;
147 /* Decrease pps_valid to indicate that another second has passed since
148 * the last PPS signal. When it reaches 0, indicate that PPS signal is
151 * Must be called while holding a write on the ntp_lock
153 static inline void pps_dec_valid(void)
158 time_status
&= ~(STA_PPSSIGNAL
| STA_PPSJITTER
|
159 STA_PPSWANDER
| STA_PPSERROR
);
164 static inline void pps_set_freq(s64 freq
)
169 static inline int is_error_status(int status
)
171 return (time_status
& (STA_UNSYNC
|STA_CLOCKERR
))
172 /* PPS signal lost when either PPS time or
173 * PPS frequency synchronization requested
175 || ((time_status
& (STA_PPSFREQ
|STA_PPSTIME
))
176 && !(time_status
& STA_PPSSIGNAL
))
177 /* PPS jitter exceeded when
178 * PPS time synchronization requested */
179 || ((time_status
& (STA_PPSTIME
|STA_PPSJITTER
))
180 == (STA_PPSTIME
|STA_PPSJITTER
))
181 /* PPS wander exceeded or calibration error when
182 * PPS frequency synchronization requested
184 || ((time_status
& STA_PPSFREQ
)
185 && (time_status
& (STA_PPSWANDER
|STA_PPSERROR
)));
188 static inline void pps_fill_timex(struct timex
*txc
)
190 txc
->ppsfreq
= shift_right((pps_freq
>> PPM_SCALE_INV_SHIFT
) *
191 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
192 txc
->jitter
= pps_jitter
;
193 if (!(time_status
& STA_NANO
))
194 txc
->jitter
/= NSEC_PER_USEC
;
195 txc
->shift
= pps_shift
;
196 txc
->stabil
= pps_stabil
;
197 txc
->jitcnt
= pps_jitcnt
;
198 txc
->calcnt
= pps_calcnt
;
199 txc
->errcnt
= pps_errcnt
;
200 txc
->stbcnt
= pps_stbcnt
;
203 #else /* !CONFIG_NTP_PPS */
205 static inline s64
ntp_offset_chunk(s64 offset
)
207 return shift_right(offset
, SHIFT_PLL
+ time_constant
);
210 static inline void pps_reset_freq_interval(void) {}
211 static inline void pps_clear(void) {}
212 static inline void pps_dec_valid(void) {}
213 static inline void pps_set_freq(s64 freq
) {}
215 static inline int is_error_status(int status
)
217 return status
& (STA_UNSYNC
|STA_CLOCKERR
);
220 static inline void pps_fill_timex(struct timex
*txc
)
222 /* PPS is not implemented, so these are zero */
233 #endif /* CONFIG_NTP_PPS */
237 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
240 static inline int ntp_synced(void)
242 return !(time_status
& STA_UNSYNC
);
251 * Update (tick_length, tick_length_base, tick_nsec), based
252 * on (tick_usec, ntp_tick_adj, time_freq):
254 static void ntp_update_frequency(void)
259 second_length
= (u64
)(tick_usec
* NSEC_PER_USEC
* USER_HZ
)
262 second_length
+= ntp_tick_adj
;
263 second_length
+= time_freq
;
265 tick_nsec
= div_u64(second_length
, HZ
) >> NTP_SCALE_SHIFT
;
266 new_base
= div_u64(second_length
, NTP_INTERVAL_FREQ
);
269 * Don't wait for the next second_overflow, apply
270 * the change to the tick length immediately:
272 tick_length
+= new_base
- tick_length_base
;
273 tick_length_base
= new_base
;
276 static inline s64
ntp_update_offset_fll(s64 offset64
, long secs
)
278 time_status
&= ~STA_MODE
;
283 if (!(time_status
& STA_FLL
) && (secs
<= MAXSEC
))
286 time_status
|= STA_MODE
;
288 return div64_long(offset64
<< (NTP_SCALE_SHIFT
- SHIFT_FLL
), secs
);
291 static void ntp_update_offset(long offset
)
297 if (!(time_status
& STA_PLL
))
300 if (!(time_status
& STA_NANO
))
301 offset
*= NSEC_PER_USEC
;
304 * Scale the phase adjustment and
305 * clamp to the operating range.
307 offset
= min(offset
, MAXPHASE
);
308 offset
= max(offset
, -MAXPHASE
);
311 * Select how the frequency is to be controlled
312 * and in which mode (PLL or FLL).
314 secs
= get_seconds() - time_reftime
;
315 if (unlikely(time_status
& STA_FREQHOLD
))
318 time_reftime
= get_seconds();
321 freq_adj
= ntp_update_offset_fll(offset64
, secs
);
324 * Clamp update interval to reduce PLL gain with low
325 * sampling rate (e.g. intermittent network connection)
326 * to avoid instability.
328 if (unlikely(secs
> 1 << (SHIFT_PLL
+ 1 + time_constant
)))
329 secs
= 1 << (SHIFT_PLL
+ 1 + time_constant
);
331 freq_adj
+= (offset64
* secs
) <<
332 (NTP_SCALE_SHIFT
- 2 * (SHIFT_PLL
+ 2 + time_constant
));
334 freq_adj
= min(freq_adj
+ time_freq
, MAXFREQ_SCALED
);
336 time_freq
= max(freq_adj
, -MAXFREQ_SCALED
);
338 time_offset
= div_s64(offset64
<< NTP_SCALE_SHIFT
, NTP_INTERVAL_FREQ
);
342 * ntp_clear - Clears the NTP state variables
348 raw_spin_lock_irqsave(&ntp_lock
, flags
);
350 time_adjust
= 0; /* stop active adjtime() */
351 time_status
|= STA_UNSYNC
;
352 time_maxerror
= NTP_PHASE_LIMIT
;
353 time_esterror
= NTP_PHASE_LIMIT
;
355 ntp_update_frequency();
357 tick_length
= tick_length_base
;
360 /* Clear PPS state variables */
362 raw_spin_unlock_irqrestore(&ntp_lock
, flags
);
367 u64
ntp_tick_length(void)
372 raw_spin_lock_irqsave(&ntp_lock
, flags
);
374 raw_spin_unlock_irqrestore(&ntp_lock
, flags
);
380 * this routine handles the overflow of the microsecond field
382 * The tricky bits of code to handle the accurate clock support
383 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
384 * They were originally developed for SUN and DEC kernels.
385 * All the kudos should go to Dave for this stuff.
387 * Also handles leap second processing, and returns leap offset
389 int second_overflow(unsigned long secs
)
395 raw_spin_lock_irqsave(&ntp_lock
, flags
);
398 * Leap second processing. If in leap-insert state at the end of the
399 * day, the system clock is set back one second; if in leap-delete
400 * state, the system clock is set ahead one second.
402 switch (time_state
) {
404 if (time_status
& STA_INS
)
405 time_state
= TIME_INS
;
406 else if (time_status
& STA_DEL
)
407 time_state
= TIME_DEL
;
410 if (!(time_status
& STA_INS
))
411 time_state
= TIME_OK
;
412 else if (secs
% 86400 == 0) {
414 time_state
= TIME_OOP
;
416 "Clock: inserting leap second 23:59:60 UTC\n");
420 if (!(time_status
& STA_DEL
))
421 time_state
= TIME_OK
;
422 else if ((secs
+ 1) % 86400 == 0) {
424 time_state
= TIME_WAIT
;
426 "Clock: deleting leap second 23:59:59 UTC\n");
430 time_state
= TIME_WAIT
;
434 if (!(time_status
& (STA_INS
| STA_DEL
)))
435 time_state
= TIME_OK
;
440 /* Bump the maxerror field */
441 time_maxerror
+= MAXFREQ
/ NSEC_PER_USEC
;
442 if (time_maxerror
> NTP_PHASE_LIMIT
) {
443 time_maxerror
= NTP_PHASE_LIMIT
;
444 time_status
|= STA_UNSYNC
;
447 /* Compute the phase adjustment for the next second */
448 tick_length
= tick_length_base
;
450 delta
= ntp_offset_chunk(time_offset
);
451 time_offset
-= delta
;
452 tick_length
+= delta
;
454 /* Check PPS signal */
460 if (time_adjust
> MAX_TICKADJ
) {
461 time_adjust
-= MAX_TICKADJ
;
462 tick_length
+= MAX_TICKADJ_SCALED
;
466 if (time_adjust
< -MAX_TICKADJ
) {
467 time_adjust
+= MAX_TICKADJ
;
468 tick_length
-= MAX_TICKADJ_SCALED
;
472 tick_length
+= (s64
)(time_adjust
* NSEC_PER_USEC
/ NTP_INTERVAL_FREQ
)
477 raw_spin_unlock_irqrestore(&ntp_lock
, flags
);
482 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
483 static void sync_cmos_clock(struct work_struct
*work
);
485 static DECLARE_DELAYED_WORK(sync_cmos_work
, sync_cmos_clock
);
487 static void sync_cmos_clock(struct work_struct
*work
)
489 struct timespec now
, next
;
493 * If we have an externally synchronized Linux clock, then update
494 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
495 * called as close as possible to 500 ms before the new second starts.
496 * This code is run on a timer. If the clock is set, that timer
497 * may not expire at the correct time. Thus, we adjust...
501 * Not synced, exit, do not restart a timer (if one is
502 * running, let it run out).
507 getnstimeofday(&now
);
508 if (abs(now
.tv_nsec
- (NSEC_PER_SEC
/ 2)) <= tick_nsec
/ 2) {
509 struct timespec adjust
= now
;
512 if (persistent_clock_is_local
)
513 adjust
.tv_sec
-= (sys_tz
.tz_minuteswest
* 60);
514 #ifdef CONFIG_GENERIC_CMOS_UPDATE
515 fail
= update_persistent_clock(adjust
);
517 #ifdef CONFIG_RTC_SYSTOHC
519 fail
= rtc_set_ntp_time(adjust
);
523 next
.tv_nsec
= (NSEC_PER_SEC
/ 2) - now
.tv_nsec
- (TICK_NSEC
/ 2);
524 if (next
.tv_nsec
<= 0)
525 next
.tv_nsec
+= NSEC_PER_SEC
;
527 if (!fail
|| fail
== -ENODEV
)
532 if (next
.tv_nsec
>= NSEC_PER_SEC
) {
534 next
.tv_nsec
-= NSEC_PER_SEC
;
536 schedule_delayed_work(&sync_cmos_work
, timespec_to_jiffies(&next
));
539 static void notify_cmos_timer(void)
541 schedule_delayed_work(&sync_cmos_work
, 0);
545 static inline void notify_cmos_timer(void) { }
550 * Propagate a new txc->status value into the NTP state:
552 static inline void process_adj_status(struct timex
*txc
, struct timespec
*ts
)
554 if ((time_status
& STA_PLL
) && !(txc
->status
& STA_PLL
)) {
555 time_state
= TIME_OK
;
556 time_status
= STA_UNSYNC
;
557 /* restart PPS frequency calibration */
558 pps_reset_freq_interval();
562 * If we turn on PLL adjustments then reset the
563 * reference time to current time.
565 if (!(time_status
& STA_PLL
) && (txc
->status
& STA_PLL
))
566 time_reftime
= get_seconds();
568 /* only set allowed bits */
569 time_status
&= STA_RONLY
;
570 time_status
|= txc
->status
& ~STA_RONLY
;
574 * Called with ntp_lock held, so we can access and modify
575 * all the global NTP state:
577 static inline void process_adjtimex_modes(struct timex
*txc
,
581 if (txc
->modes
& ADJ_STATUS
)
582 process_adj_status(txc
, ts
);
584 if (txc
->modes
& ADJ_NANO
)
585 time_status
|= STA_NANO
;
587 if (txc
->modes
& ADJ_MICRO
)
588 time_status
&= ~STA_NANO
;
590 if (txc
->modes
& ADJ_FREQUENCY
) {
591 time_freq
= txc
->freq
* PPM_SCALE
;
592 time_freq
= min(time_freq
, MAXFREQ_SCALED
);
593 time_freq
= max(time_freq
, -MAXFREQ_SCALED
);
594 /* update pps_freq */
595 pps_set_freq(time_freq
);
598 if (txc
->modes
& ADJ_MAXERROR
)
599 time_maxerror
= txc
->maxerror
;
601 if (txc
->modes
& ADJ_ESTERROR
)
602 time_esterror
= txc
->esterror
;
604 if (txc
->modes
& ADJ_TIMECONST
) {
605 time_constant
= txc
->constant
;
606 if (!(time_status
& STA_NANO
))
608 time_constant
= min(time_constant
, (long)MAXTC
);
609 time_constant
= max(time_constant
, 0l);
612 if (txc
->modes
& ADJ_TAI
&& txc
->constant
> 0)
613 *time_tai
= txc
->constant
;
615 if (txc
->modes
& ADJ_OFFSET
)
616 ntp_update_offset(txc
->offset
);
618 if (txc
->modes
& ADJ_TICK
)
619 tick_usec
= txc
->tick
;
621 if (txc
->modes
& (ADJ_TICK
|ADJ_FREQUENCY
|ADJ_OFFSET
))
622 ntp_update_frequency();
626 * adjtimex mainly allows reading (and writing, if superuser) of
627 * kernel time-keeping variables. used by xntpd.
629 int do_adjtimex(struct timex
*txc
)
632 u32 time_tai
, orig_tai
;
635 /* Validate the data before disabling interrupts */
636 if (txc
->modes
& ADJ_ADJTIME
) {
637 /* singleshot must not be used with any other mode bits */
638 if (!(txc
->modes
& ADJ_OFFSET_SINGLESHOT
))
640 if (!(txc
->modes
& ADJ_OFFSET_READONLY
) &&
641 !capable(CAP_SYS_TIME
))
644 /* In order to modify anything, you gotta be super-user! */
645 if (txc
->modes
&& !capable(CAP_SYS_TIME
))
649 * if the quartz is off by more than 10% then
650 * something is VERY wrong!
652 if (txc
->modes
& ADJ_TICK
&&
653 (txc
->tick
< 900000/USER_HZ
||
654 txc
->tick
> 1100000/USER_HZ
))
658 if (txc
->modes
& ADJ_SETOFFSET
) {
659 struct timespec delta
;
660 delta
.tv_sec
= txc
->time
.tv_sec
;
661 delta
.tv_nsec
= txc
->time
.tv_usec
;
662 if (!capable(CAP_SYS_TIME
))
664 if (!(txc
->modes
& ADJ_NANO
))
665 delta
.tv_nsec
*= 1000;
666 result
= timekeeping_inject_offset(&delta
);
672 orig_tai
= time_tai
= timekeeping_get_tai_offset();
674 raw_spin_lock_irq(&ntp_lock
);
676 if (txc
->modes
& ADJ_ADJTIME
) {
677 long save_adjust
= time_adjust
;
679 if (!(txc
->modes
& ADJ_OFFSET_READONLY
)) {
680 /* adjtime() is independent from ntp_adjtime() */
681 time_adjust
= txc
->offset
;
682 ntp_update_frequency();
684 txc
->offset
= save_adjust
;
687 /* If there are input parameters, then process them: */
689 process_adjtimex_modes(txc
, &ts
, &time_tai
);
691 txc
->offset
= shift_right(time_offset
* NTP_INTERVAL_FREQ
,
693 if (!(time_status
& STA_NANO
))
694 txc
->offset
/= NSEC_PER_USEC
;
697 result
= time_state
; /* mostly `TIME_OK' */
698 /* check for errors */
699 if (is_error_status(time_status
))
702 txc
->freq
= shift_right((time_freq
>> PPM_SCALE_INV_SHIFT
) *
703 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
704 txc
->maxerror
= time_maxerror
;
705 txc
->esterror
= time_esterror
;
706 txc
->status
= time_status
;
707 txc
->constant
= time_constant
;
709 txc
->tolerance
= MAXFREQ_SCALED
/ PPM_SCALE
;
710 txc
->tick
= tick_usec
;
713 /* fill PPS status fields */
716 raw_spin_unlock_irq(&ntp_lock
);
718 if (time_tai
!= orig_tai
)
719 timekeeping_set_tai_offset(time_tai
);
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 raw_spin_lock_irqsave(&ntp_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 raw_spin_unlock_irqrestore(&ntp_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 raw_spin_unlock_irqrestore(&ntp_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 raw_spin_unlock_irqrestore(&ntp_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)