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 "ntp_internal.h"
23 * NTP timekeeping variables:
25 * Note: All of the NTP state is protected by the timekeeping locks.
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 static inline void pps_clear(void)
137 pps_reset_freq_interval();
141 pps_fbase
.tv_sec
= pps_fbase
.tv_nsec
= 0;
145 /* Decrease pps_valid to indicate that another second has passed since
146 * the last PPS signal. When it reaches 0, indicate that PPS signal is
149 static inline void pps_dec_valid(void)
154 time_status
&= ~(STA_PPSSIGNAL
| STA_PPSJITTER
|
155 STA_PPSWANDER
| STA_PPSERROR
);
160 static inline void pps_set_freq(s64 freq
)
165 static inline int is_error_status(int status
)
167 return (status
& (STA_UNSYNC
|STA_CLOCKERR
))
168 /* PPS signal lost when either PPS time or
169 * PPS frequency synchronization requested
171 || ((status
& (STA_PPSFREQ
|STA_PPSTIME
))
172 && !(status
& STA_PPSSIGNAL
))
173 /* PPS jitter exceeded when
174 * PPS time synchronization requested */
175 || ((status
& (STA_PPSTIME
|STA_PPSJITTER
))
176 == (STA_PPSTIME
|STA_PPSJITTER
))
177 /* PPS wander exceeded or calibration error when
178 * PPS frequency synchronization requested
180 || ((status
& STA_PPSFREQ
)
181 && (status
& (STA_PPSWANDER
|STA_PPSERROR
)));
184 static inline void pps_fill_timex(struct timex
*txc
)
186 txc
->ppsfreq
= shift_right((pps_freq
>> PPM_SCALE_INV_SHIFT
) *
187 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
188 txc
->jitter
= pps_jitter
;
189 if (!(time_status
& STA_NANO
))
190 txc
->jitter
/= NSEC_PER_USEC
;
191 txc
->shift
= pps_shift
;
192 txc
->stabil
= pps_stabil
;
193 txc
->jitcnt
= pps_jitcnt
;
194 txc
->calcnt
= pps_calcnt
;
195 txc
->errcnt
= pps_errcnt
;
196 txc
->stbcnt
= pps_stbcnt
;
199 #else /* !CONFIG_NTP_PPS */
201 static inline s64
ntp_offset_chunk(s64 offset
)
203 return shift_right(offset
, SHIFT_PLL
+ time_constant
);
206 static inline void pps_reset_freq_interval(void) {}
207 static inline void pps_clear(void) {}
208 static inline void pps_dec_valid(void) {}
209 static inline void pps_set_freq(s64 freq
) {}
211 static inline int is_error_status(int status
)
213 return status
& (STA_UNSYNC
|STA_CLOCKERR
);
216 static inline void pps_fill_timex(struct timex
*txc
)
218 /* PPS is not implemented, so these are zero */
229 #endif /* CONFIG_NTP_PPS */
233 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
236 static inline int ntp_synced(void)
238 return !(time_status
& STA_UNSYNC
);
247 * Update (tick_length, tick_length_base, tick_nsec), based
248 * on (tick_usec, ntp_tick_adj, time_freq):
250 static void ntp_update_frequency(void)
255 second_length
= (u64
)(tick_usec
* NSEC_PER_USEC
* USER_HZ
)
258 second_length
+= ntp_tick_adj
;
259 second_length
+= time_freq
;
261 tick_nsec
= div_u64(second_length
, HZ
) >> NTP_SCALE_SHIFT
;
262 new_base
= div_u64(second_length
, NTP_INTERVAL_FREQ
);
265 * Don't wait for the next second_overflow, apply
266 * the change to the tick length immediately:
268 tick_length
+= new_base
- tick_length_base
;
269 tick_length_base
= new_base
;
272 static inline s64
ntp_update_offset_fll(s64 offset64
, long secs
)
274 time_status
&= ~STA_MODE
;
279 if (!(time_status
& STA_FLL
) && (secs
<= MAXSEC
))
282 time_status
|= STA_MODE
;
284 return div64_long(offset64
<< (NTP_SCALE_SHIFT
- SHIFT_FLL
), secs
);
287 static void ntp_update_offset(long offset
)
293 if (!(time_status
& STA_PLL
))
296 if (!(time_status
& STA_NANO
))
297 offset
*= NSEC_PER_USEC
;
300 * Scale the phase adjustment and
301 * clamp to the operating range.
303 offset
= min(offset
, MAXPHASE
);
304 offset
= max(offset
, -MAXPHASE
);
307 * Select how the frequency is to be controlled
308 * and in which mode (PLL or FLL).
310 secs
= get_seconds() - time_reftime
;
311 if (unlikely(time_status
& STA_FREQHOLD
))
314 time_reftime
= get_seconds();
317 freq_adj
= ntp_update_offset_fll(offset64
, secs
);
320 * Clamp update interval to reduce PLL gain with low
321 * sampling rate (e.g. intermittent network connection)
322 * to avoid instability.
324 if (unlikely(secs
> 1 << (SHIFT_PLL
+ 1 + time_constant
)))
325 secs
= 1 << (SHIFT_PLL
+ 1 + time_constant
);
327 freq_adj
+= (offset64
* secs
) <<
328 (NTP_SCALE_SHIFT
- 2 * (SHIFT_PLL
+ 2 + time_constant
));
330 freq_adj
= min(freq_adj
+ time_freq
, MAXFREQ_SCALED
);
332 time_freq
= max(freq_adj
, -MAXFREQ_SCALED
);
334 time_offset
= div_s64(offset64
<< NTP_SCALE_SHIFT
, NTP_INTERVAL_FREQ
);
338 * ntp_clear - Clears the NTP state variables
342 time_adjust
= 0; /* stop active adjtime() */
343 time_status
|= STA_UNSYNC
;
344 time_maxerror
= NTP_PHASE_LIMIT
;
345 time_esterror
= NTP_PHASE_LIMIT
;
347 ntp_update_frequency();
349 tick_length
= tick_length_base
;
352 /* Clear PPS state variables */
357 u64
ntp_tick_length(void)
364 * this routine handles the overflow of the microsecond field
366 * The tricky bits of code to handle the accurate clock support
367 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
368 * They were originally developed for SUN and DEC kernels.
369 * All the kudos should go to Dave for this stuff.
371 * Also handles leap second processing, and returns leap offset
373 int second_overflow(unsigned long secs
)
379 * Leap second processing. If in leap-insert state at the end of the
380 * day, the system clock is set back one second; if in leap-delete
381 * state, the system clock is set ahead one second.
383 switch (time_state
) {
385 if (time_status
& STA_INS
)
386 time_state
= TIME_INS
;
387 else if (time_status
& STA_DEL
)
388 time_state
= TIME_DEL
;
391 if (!(time_status
& STA_INS
))
392 time_state
= TIME_OK
;
393 else if (secs
% 86400 == 0) {
395 time_state
= TIME_OOP
;
397 "Clock: inserting leap second 23:59:60 UTC\n");
401 if (!(time_status
& STA_DEL
))
402 time_state
= TIME_OK
;
403 else if ((secs
+ 1) % 86400 == 0) {
405 time_state
= TIME_WAIT
;
407 "Clock: deleting leap second 23:59:59 UTC\n");
411 time_state
= TIME_WAIT
;
415 if (!(time_status
& (STA_INS
| STA_DEL
)))
416 time_state
= TIME_OK
;
421 /* Bump the maxerror field */
422 time_maxerror
+= MAXFREQ
/ NSEC_PER_USEC
;
423 if (time_maxerror
> NTP_PHASE_LIMIT
) {
424 time_maxerror
= NTP_PHASE_LIMIT
;
425 time_status
|= STA_UNSYNC
;
428 /* Compute the phase adjustment for the next second */
429 tick_length
= tick_length_base
;
431 delta
= ntp_offset_chunk(time_offset
);
432 time_offset
-= delta
;
433 tick_length
+= delta
;
435 /* Check PPS signal */
441 if (time_adjust
> MAX_TICKADJ
) {
442 time_adjust
-= MAX_TICKADJ
;
443 tick_length
+= MAX_TICKADJ_SCALED
;
447 if (time_adjust
< -MAX_TICKADJ
) {
448 time_adjust
+= MAX_TICKADJ
;
449 tick_length
-= MAX_TICKADJ_SCALED
;
453 tick_length
+= (s64
)(time_adjust
* NSEC_PER_USEC
/ NTP_INTERVAL_FREQ
)
461 #ifdef CONFIG_GENERIC_CMOS_UPDATE
462 int __weak
update_persistent_clock64(struct timespec64 now64
)
466 now
= timespec64_to_timespec(now64
);
467 return update_persistent_clock(now
);
471 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
472 static void sync_cmos_clock(struct work_struct
*work
);
474 static DECLARE_DELAYED_WORK(sync_cmos_work
, sync_cmos_clock
);
476 static void sync_cmos_clock(struct work_struct
*work
)
478 struct timespec64 now
;
479 struct timespec next
;
483 * If we have an externally synchronized Linux clock, then update
484 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
485 * called as close as possible to 500 ms before the new second starts.
486 * This code is run on a timer. If the clock is set, that timer
487 * may not expire at the correct time. Thus, we adjust...
488 * We want the clock to be within a couple of ticks from the target.
492 * Not synced, exit, do not restart a timer (if one is
493 * running, let it run out).
498 getnstimeofday64(&now
);
499 if (abs(now
.tv_nsec
- (NSEC_PER_SEC
/ 2)) <= tick_nsec
* 5) {
500 struct timespec64 adjust
= now
;
503 if (persistent_clock_is_local
)
504 adjust
.tv_sec
-= (sys_tz
.tz_minuteswest
* 60);
505 #ifdef CONFIG_GENERIC_CMOS_UPDATE
506 fail
= update_persistent_clock64(adjust
);
509 #ifdef CONFIG_RTC_SYSTOHC
511 fail
= rtc_set_ntp_time(adjust
);
515 next
.tv_nsec
= (NSEC_PER_SEC
/ 2) - now
.tv_nsec
- (TICK_NSEC
/ 2);
516 if (next
.tv_nsec
<= 0)
517 next
.tv_nsec
+= NSEC_PER_SEC
;
519 if (!fail
|| fail
== -ENODEV
)
524 if (next
.tv_nsec
>= NSEC_PER_SEC
) {
526 next
.tv_nsec
-= NSEC_PER_SEC
;
528 queue_delayed_work(system_power_efficient_wq
,
529 &sync_cmos_work
, timespec_to_jiffies(&next
));
532 void ntp_notify_cmos_timer(void)
534 queue_delayed_work(system_power_efficient_wq
, &sync_cmos_work
, 0);
538 void ntp_notify_cmos_timer(void) { }
543 * Propagate a new txc->status value into the NTP state:
545 static inline void process_adj_status(struct timex
*txc
, struct timespec64
*ts
)
547 if ((time_status
& STA_PLL
) && !(txc
->status
& STA_PLL
)) {
548 time_state
= TIME_OK
;
549 time_status
= STA_UNSYNC
;
550 /* restart PPS frequency calibration */
551 pps_reset_freq_interval();
555 * If we turn on PLL adjustments then reset the
556 * reference time to current time.
558 if (!(time_status
& STA_PLL
) && (txc
->status
& STA_PLL
))
559 time_reftime
= get_seconds();
561 /* only set allowed bits */
562 time_status
&= STA_RONLY
;
563 time_status
|= txc
->status
& ~STA_RONLY
;
567 static inline void process_adjtimex_modes(struct timex
*txc
,
568 struct timespec64
*ts
,
571 if (txc
->modes
& ADJ_STATUS
)
572 process_adj_status(txc
, ts
);
574 if (txc
->modes
& ADJ_NANO
)
575 time_status
|= STA_NANO
;
577 if (txc
->modes
& ADJ_MICRO
)
578 time_status
&= ~STA_NANO
;
580 if (txc
->modes
& ADJ_FREQUENCY
) {
581 time_freq
= txc
->freq
* PPM_SCALE
;
582 time_freq
= min(time_freq
, MAXFREQ_SCALED
);
583 time_freq
= max(time_freq
, -MAXFREQ_SCALED
);
584 /* update pps_freq */
585 pps_set_freq(time_freq
);
588 if (txc
->modes
& ADJ_MAXERROR
)
589 time_maxerror
= txc
->maxerror
;
591 if (txc
->modes
& ADJ_ESTERROR
)
592 time_esterror
= txc
->esterror
;
594 if (txc
->modes
& ADJ_TIMECONST
) {
595 time_constant
= txc
->constant
;
596 if (!(time_status
& STA_NANO
))
598 time_constant
= min(time_constant
, (long)MAXTC
);
599 time_constant
= max(time_constant
, 0l);
602 if (txc
->modes
& ADJ_TAI
&& txc
->constant
> 0)
603 *time_tai
= txc
->constant
;
605 if (txc
->modes
& ADJ_OFFSET
)
606 ntp_update_offset(txc
->offset
);
608 if (txc
->modes
& ADJ_TICK
)
609 tick_usec
= txc
->tick
;
611 if (txc
->modes
& (ADJ_TICK
|ADJ_FREQUENCY
|ADJ_OFFSET
))
612 ntp_update_frequency();
618 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
620 int ntp_validate_timex(struct timex
*txc
)
622 if (txc
->modes
& ADJ_ADJTIME
) {
623 /* singleshot must not be used with any other mode bits */
624 if (!(txc
->modes
& ADJ_OFFSET_SINGLESHOT
))
626 if (!(txc
->modes
& ADJ_OFFSET_READONLY
) &&
627 !capable(CAP_SYS_TIME
))
630 /* In order to modify anything, you gotta be super-user! */
631 if (txc
->modes
&& !capable(CAP_SYS_TIME
))
634 * if the quartz is off by more than 10% then
635 * something is VERY wrong!
637 if (txc
->modes
& ADJ_TICK
&&
638 (txc
->tick
< 900000/USER_HZ
||
639 txc
->tick
> 1100000/USER_HZ
))
643 if ((txc
->modes
& ADJ_SETOFFSET
) && (!capable(CAP_SYS_TIME
)))
647 * Check for potential multiplication overflows that can
648 * only happen on 64-bit systems:
650 if ((txc
->modes
& ADJ_FREQUENCY
) && (BITS_PER_LONG
== 64)) {
651 if (LLONG_MIN
/ PPM_SCALE
> txc
->freq
)
653 if (LLONG_MAX
/ PPM_SCALE
< txc
->freq
)
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
, struct timespec64
*ts
, s32
*time_tai
)
669 if (txc
->modes
& ADJ_ADJTIME
) {
670 long save_adjust
= time_adjust
;
672 if (!(txc
->modes
& ADJ_OFFSET_READONLY
)) {
673 /* adjtime() is independent from ntp_adjtime() */
674 time_adjust
= txc
->offset
;
675 ntp_update_frequency();
677 txc
->offset
= save_adjust
;
680 /* If there are input parameters, then process them: */
682 process_adjtimex_modes(txc
, ts
, time_tai
);
684 txc
->offset
= shift_right(time_offset
* NTP_INTERVAL_FREQ
,
686 if (!(time_status
& STA_NANO
))
687 txc
->offset
/= NSEC_PER_USEC
;
690 result
= time_state
; /* mostly `TIME_OK' */
691 /* check for errors */
692 if (is_error_status(time_status
))
695 txc
->freq
= shift_right((time_freq
>> PPM_SCALE_INV_SHIFT
) *
696 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
697 txc
->maxerror
= time_maxerror
;
698 txc
->esterror
= time_esterror
;
699 txc
->status
= time_status
;
700 txc
->constant
= time_constant
;
702 txc
->tolerance
= MAXFREQ_SCALED
/ PPM_SCALE
;
703 txc
->tick
= tick_usec
;
704 txc
->tai
= *time_tai
;
706 /* fill PPS status fields */
709 txc
->time
.tv_sec
= (time_t)ts
->tv_sec
;
710 txc
->time
.tv_usec
= ts
->tv_nsec
;
711 if (!(time_status
& STA_NANO
))
712 txc
->time
.tv_usec
/= NSEC_PER_USEC
;
717 #ifdef CONFIG_NTP_PPS
719 /* actually struct pps_normtime is good old struct timespec, but it is
720 * semantically different (and it is the reason why it was invented):
721 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
722 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
723 struct pps_normtime
{
724 __kernel_time_t sec
; /* seconds */
725 long nsec
; /* nanoseconds */
728 /* normalize the timestamp so that nsec is in the
729 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
730 static inline struct pps_normtime
pps_normalize_ts(struct timespec ts
)
732 struct pps_normtime norm
= {
737 if (norm
.nsec
> (NSEC_PER_SEC
>> 1)) {
738 norm
.nsec
-= NSEC_PER_SEC
;
745 /* get current phase correction and jitter */
746 static inline long pps_phase_filter_get(long *jitter
)
748 *jitter
= pps_tf
[0] - pps_tf
[1];
752 /* TODO: test various filters */
756 /* add the sample to the phase filter */
757 static inline void pps_phase_filter_add(long err
)
759 pps_tf
[2] = pps_tf
[1];
760 pps_tf
[1] = pps_tf
[0];
764 /* decrease frequency calibration interval length.
765 * It is halved after four consecutive unstable intervals.
767 static inline void pps_dec_freq_interval(void)
769 if (--pps_intcnt
<= -PPS_INTCOUNT
) {
770 pps_intcnt
= -PPS_INTCOUNT
;
771 if (pps_shift
> PPS_INTMIN
) {
778 /* increase frequency calibration interval length.
779 * It is doubled after four consecutive stable intervals.
781 static inline void pps_inc_freq_interval(void)
783 if (++pps_intcnt
>= PPS_INTCOUNT
) {
784 pps_intcnt
= PPS_INTCOUNT
;
785 if (pps_shift
< PPS_INTMAX
) {
792 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
795 * At the end of the calibration interval the difference between the
796 * first and last MONOTONIC_RAW clock timestamps divided by the length
797 * of the interval becomes the frequency update. If the interval was
798 * too long, the data are discarded.
799 * Returns the difference between old and new frequency values.
801 static long hardpps_update_freq(struct pps_normtime freq_norm
)
803 long delta
, delta_mod
;
806 /* check if the frequency interval was too long */
807 if (freq_norm
.sec
> (2 << pps_shift
)) {
808 time_status
|= STA_PPSERROR
;
810 pps_dec_freq_interval();
811 printk_deferred(KERN_ERR
812 "hardpps: PPSERROR: interval too long - %ld s\n",
817 /* here the raw frequency offset and wander (stability) is
818 * calculated. If the wander is less than the wander threshold
819 * the interval is increased; otherwise it is decreased.
821 ftemp
= div_s64(((s64
)(-freq_norm
.nsec
)) << NTP_SCALE_SHIFT
,
823 delta
= shift_right(ftemp
- pps_freq
, NTP_SCALE_SHIFT
);
825 if (delta
> PPS_MAXWANDER
|| delta
< -PPS_MAXWANDER
) {
826 printk_deferred(KERN_WARNING
827 "hardpps: PPSWANDER: change=%ld\n", delta
);
828 time_status
|= STA_PPSWANDER
;
830 pps_dec_freq_interval();
831 } else { /* good sample */
832 pps_inc_freq_interval();
835 /* the stability metric is calculated as the average of recent
836 * frequency changes, but is used only for performance
841 delta_mod
= -delta_mod
;
842 pps_stabil
+= (div_s64(((s64
)delta_mod
) <<
843 (NTP_SCALE_SHIFT
- SHIFT_USEC
),
844 NSEC_PER_USEC
) - pps_stabil
) >> PPS_INTMIN
;
846 /* if enabled, the system clock frequency is updated */
847 if ((time_status
& STA_PPSFREQ
) != 0 &&
848 (time_status
& STA_FREQHOLD
) == 0) {
849 time_freq
= pps_freq
;
850 ntp_update_frequency();
856 /* correct REALTIME clock phase error against PPS signal */
857 static void hardpps_update_phase(long error
)
859 long correction
= -error
;
862 /* add the sample to the median filter */
863 pps_phase_filter_add(correction
);
864 correction
= pps_phase_filter_get(&jitter
);
866 /* Nominal jitter is due to PPS signal noise. If it exceeds the
867 * threshold, the sample is discarded; otherwise, if so enabled,
868 * the time offset is updated.
870 if (jitter
> (pps_jitter
<< PPS_POPCORN
)) {
871 printk_deferred(KERN_WARNING
872 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
873 jitter
, (pps_jitter
<< PPS_POPCORN
));
874 time_status
|= STA_PPSJITTER
;
876 } else if (time_status
& STA_PPSTIME
) {
877 /* correct the time using the phase offset */
878 time_offset
= div_s64(((s64
)correction
) << NTP_SCALE_SHIFT
,
880 /* cancel running adjtime() */
884 pps_jitter
+= (jitter
- pps_jitter
) >> PPS_INTMIN
;
888 * __hardpps() - discipline CPU clock oscillator to external PPS signal
890 * This routine is called at each PPS signal arrival in order to
891 * discipline the CPU clock oscillator to the PPS signal. It takes two
892 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
893 * is used to correct clock phase error and the latter is used to
894 * correct the frequency.
896 * This code is based on David Mills's reference nanokernel
897 * implementation. It was mostly rewritten but keeps the same idea.
899 void __hardpps(const struct timespec
*phase_ts
, const struct timespec
*raw_ts
)
901 struct pps_normtime pts_norm
, freq_norm
;
903 pts_norm
= pps_normalize_ts(*phase_ts
);
905 /* clear the error bits, they will be set again if needed */
906 time_status
&= ~(STA_PPSJITTER
| STA_PPSWANDER
| STA_PPSERROR
);
908 /* indicate signal presence */
909 time_status
|= STA_PPSSIGNAL
;
910 pps_valid
= PPS_VALID
;
912 /* when called for the first time,
913 * just start the frequency interval */
914 if (unlikely(pps_fbase
.tv_sec
== 0)) {
919 /* ok, now we have a base for frequency calculation */
920 freq_norm
= pps_normalize_ts(timespec_sub(*raw_ts
, pps_fbase
));
922 /* check that the signal is in the range
923 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
924 if ((freq_norm
.sec
== 0) ||
925 (freq_norm
.nsec
> MAXFREQ
* freq_norm
.sec
) ||
926 (freq_norm
.nsec
< -MAXFREQ
* freq_norm
.sec
)) {
927 time_status
|= STA_PPSJITTER
;
928 /* restart the frequency calibration interval */
930 printk_deferred(KERN_ERR
"hardpps: PPSJITTER: bad pulse\n");
936 /* check if the current frequency interval is finished */
937 if (freq_norm
.sec
>= (1 << pps_shift
)) {
939 /* restart the frequency calibration interval */
941 hardpps_update_freq(freq_norm
);
944 hardpps_update_phase(pts_norm
.nsec
);
947 #endif /* CONFIG_NTP_PPS */
949 static int __init
ntp_tick_adj_setup(char *str
)
951 int rc
= kstrtol(str
, 0, (long *)&ntp_tick_adj
);
955 ntp_tick_adj
<<= NTP_SCALE_SHIFT
;
960 __setup("ntp_tick_adj=", ntp_tick_adj_setup
);
962 void __init
ntp_init(void)