]>
git.proxmox.com Git - mirror_ubuntu-jammy-kernel.git/blob - kernel/time/ntp.c
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_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 /* TAI offset (secs): */
59 /* time adjustment (nsecs): */
60 static s64 time_offset
;
62 /* pll time constant: */
63 static long time_constant
= 2;
65 /* maximum error (usecs): */
66 static long time_maxerror
= NTP_PHASE_LIMIT
;
68 /* estimated error (usecs): */
69 static long time_esterror
= NTP_PHASE_LIMIT
;
71 /* frequency offset (scaled nsecs/secs): */
74 /* time at last adjustment (secs): */
75 static long time_reftime
;
77 static long time_adjust
;
79 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
80 static s64 ntp_tick_adj
;
85 * The following variables are used when a pulse-per-second (PPS) signal
86 * is available. They establish the engineering parameters of the clock
87 * discipline loop when controlled by the PPS signal.
89 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
90 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
91 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
92 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
93 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
94 increase pps_shift or consecutive bad
95 intervals to decrease it */
96 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
98 static int pps_valid
; /* signal watchdog counter */
99 static long pps_tf
[3]; /* phase median filter */
100 static long pps_jitter
; /* current jitter (ns) */
101 static struct timespec pps_fbase
; /* beginning of the last freq interval */
102 static int pps_shift
; /* current interval duration (s) (shift) */
103 static int pps_intcnt
; /* interval counter */
104 static s64 pps_freq
; /* frequency offset (scaled ns/s) */
105 static long pps_stabil
; /* current stability (scaled ns/s) */
108 * PPS signal quality monitors
110 static long pps_calcnt
; /* calibration intervals */
111 static long pps_jitcnt
; /* jitter limit exceeded */
112 static long pps_stbcnt
; /* stability limit exceeded */
113 static long pps_errcnt
; /* calibration errors */
116 /* PPS kernel consumer compensates the whole phase error immediately.
117 * Otherwise, reduce the offset by a fixed factor times the time constant.
119 static inline s64
ntp_offset_chunk(s64 offset
)
121 if (time_status
& STA_PPSTIME
&& time_status
& STA_PPSSIGNAL
)
124 return shift_right(offset
, SHIFT_PLL
+ time_constant
);
127 static inline void pps_reset_freq_interval(void)
129 /* the PPS calibration interval may end
130 surprisingly early */
131 pps_shift
= PPS_INTMIN
;
136 * pps_clear - Clears the PPS state variables
138 * Must be called while holding a write on the ntp_lock
140 static inline void pps_clear(void)
142 pps_reset_freq_interval();
146 pps_fbase
.tv_sec
= pps_fbase
.tv_nsec
= 0;
150 /* Decrease pps_valid to indicate that another second has passed since
151 * the last PPS signal. When it reaches 0, indicate that PPS signal is
154 * Must be called while holding a write on the ntp_lock
156 static inline void pps_dec_valid(void)
161 time_status
&= ~(STA_PPSSIGNAL
| STA_PPSJITTER
|
162 STA_PPSWANDER
| STA_PPSERROR
);
167 static inline void pps_set_freq(s64 freq
)
172 static inline int is_error_status(int status
)
174 return (time_status
& (STA_UNSYNC
|STA_CLOCKERR
))
175 /* PPS signal lost when either PPS time or
176 * PPS frequency synchronization requested
178 || ((time_status
& (STA_PPSFREQ
|STA_PPSTIME
))
179 && !(time_status
& STA_PPSSIGNAL
))
180 /* PPS jitter exceeded when
181 * PPS time synchronization requested */
182 || ((time_status
& (STA_PPSTIME
|STA_PPSJITTER
))
183 == (STA_PPSTIME
|STA_PPSJITTER
))
184 /* PPS wander exceeded or calibration error when
185 * PPS frequency synchronization requested
187 || ((time_status
& STA_PPSFREQ
)
188 && (time_status
& (STA_PPSWANDER
|STA_PPSERROR
)));
191 static inline void pps_fill_timex(struct timex
*txc
)
193 txc
->ppsfreq
= shift_right((pps_freq
>> PPM_SCALE_INV_SHIFT
) *
194 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
195 txc
->jitter
= pps_jitter
;
196 if (!(time_status
& STA_NANO
))
197 txc
->jitter
/= NSEC_PER_USEC
;
198 txc
->shift
= pps_shift
;
199 txc
->stabil
= pps_stabil
;
200 txc
->jitcnt
= pps_jitcnt
;
201 txc
->calcnt
= pps_calcnt
;
202 txc
->errcnt
= pps_errcnt
;
203 txc
->stbcnt
= pps_stbcnt
;
206 #else /* !CONFIG_NTP_PPS */
208 static inline s64
ntp_offset_chunk(s64 offset
)
210 return shift_right(offset
, SHIFT_PLL
+ time_constant
);
213 static inline void pps_reset_freq_interval(void) {}
214 static inline void pps_clear(void) {}
215 static inline void pps_dec_valid(void) {}
216 static inline void pps_set_freq(s64 freq
) {}
218 static inline int is_error_status(int status
)
220 return status
& (STA_UNSYNC
|STA_CLOCKERR
);
223 static inline void pps_fill_timex(struct timex
*txc
)
225 /* PPS is not implemented, so these are zero */
236 #endif /* CONFIG_NTP_PPS */
240 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
243 static inline int ntp_synced(void)
245 return !(time_status
& STA_UNSYNC
);
254 * Update (tick_length, tick_length_base, tick_nsec), based
255 * on (tick_usec, ntp_tick_adj, time_freq):
257 static void ntp_update_frequency(void)
262 second_length
= (u64
)(tick_usec
* NSEC_PER_USEC
* USER_HZ
)
265 second_length
+= ntp_tick_adj
;
266 second_length
+= time_freq
;
268 tick_nsec
= div_u64(second_length
, HZ
) >> NTP_SCALE_SHIFT
;
269 new_base
= div_u64(second_length
, NTP_INTERVAL_FREQ
);
272 * Don't wait for the next second_overflow, apply
273 * the change to the tick length immediately:
275 tick_length
+= new_base
- tick_length_base
;
276 tick_length_base
= new_base
;
279 static inline s64
ntp_update_offset_fll(s64 offset64
, long secs
)
281 time_status
&= ~STA_MODE
;
286 if (!(time_status
& STA_FLL
) && (secs
<= MAXSEC
))
289 time_status
|= STA_MODE
;
291 return div64_long(offset64
<< (NTP_SCALE_SHIFT
- SHIFT_FLL
), secs
);
294 static void ntp_update_offset(long offset
)
300 if (!(time_status
& STA_PLL
))
303 if (!(time_status
& STA_NANO
))
304 offset
*= NSEC_PER_USEC
;
307 * Scale the phase adjustment and
308 * clamp to the operating range.
310 offset
= min(offset
, MAXPHASE
);
311 offset
= max(offset
, -MAXPHASE
);
314 * Select how the frequency is to be controlled
315 * and in which mode (PLL or FLL).
317 secs
= get_seconds() - time_reftime
;
318 if (unlikely(time_status
& STA_FREQHOLD
))
321 time_reftime
= get_seconds();
324 freq_adj
= ntp_update_offset_fll(offset64
, secs
);
327 * Clamp update interval to reduce PLL gain with low
328 * sampling rate (e.g. intermittent network connection)
329 * to avoid instability.
331 if (unlikely(secs
> 1 << (SHIFT_PLL
+ 1 + time_constant
)))
332 secs
= 1 << (SHIFT_PLL
+ 1 + time_constant
);
334 freq_adj
+= (offset64
* secs
) <<
335 (NTP_SCALE_SHIFT
- 2 * (SHIFT_PLL
+ 2 + time_constant
));
337 freq_adj
= min(freq_adj
+ time_freq
, MAXFREQ_SCALED
);
339 time_freq
= max(freq_adj
, -MAXFREQ_SCALED
);
341 time_offset
= div_s64(offset64
<< NTP_SCALE_SHIFT
, NTP_INTERVAL_FREQ
);
345 * ntp_clear - Clears the NTP state variables
351 spin_lock_irqsave(&ntp_lock
, flags
);
353 time_adjust
= 0; /* stop active adjtime() */
354 time_status
|= STA_UNSYNC
;
355 time_maxerror
= NTP_PHASE_LIMIT
;
356 time_esterror
= NTP_PHASE_LIMIT
;
358 ntp_update_frequency();
360 tick_length
= tick_length_base
;
363 /* Clear PPS state variables */
365 spin_unlock_irqrestore(&ntp_lock
, flags
);
370 u64
ntp_tick_length(void)
375 spin_lock_irqsave(&ntp_lock
, flags
);
377 spin_unlock_irqrestore(&ntp_lock
, flags
);
383 * this routine handles the overflow of the microsecond field
385 * The tricky bits of code to handle the accurate clock support
386 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
387 * They were originally developed for SUN and DEC kernels.
388 * All the kudos should go to Dave for this stuff.
390 * Also handles leap second processing, and returns leap offset
392 int second_overflow(unsigned long secs
)
398 spin_lock_irqsave(&ntp_lock
, flags
);
401 * Leap second processing. If in leap-insert state at the end of the
402 * day, the system clock is set back one second; if in leap-delete
403 * state, the system clock is set ahead one second.
405 switch (time_state
) {
407 if (time_status
& STA_INS
)
408 time_state
= TIME_INS
;
409 else if (time_status
& STA_DEL
)
410 time_state
= TIME_DEL
;
413 if (!(time_status
& STA_INS
))
414 time_state
= TIME_OK
;
415 else if (secs
% 86400 == 0) {
417 time_state
= TIME_OOP
;
420 "Clock: inserting leap second 23:59:60 UTC\n");
424 if (!(time_status
& STA_DEL
))
425 time_state
= TIME_OK
;
426 else if ((secs
+ 1) % 86400 == 0) {
429 time_state
= TIME_WAIT
;
431 "Clock: deleting leap second 23:59:59 UTC\n");
435 time_state
= TIME_WAIT
;
439 if (!(time_status
& (STA_INS
| STA_DEL
)))
440 time_state
= TIME_OK
;
445 /* Bump the maxerror field */
446 time_maxerror
+= MAXFREQ
/ NSEC_PER_USEC
;
447 if (time_maxerror
> NTP_PHASE_LIMIT
) {
448 time_maxerror
= NTP_PHASE_LIMIT
;
449 time_status
|= STA_UNSYNC
;
452 /* Compute the phase adjustment for the next second */
453 tick_length
= tick_length_base
;
455 delta
= ntp_offset_chunk(time_offset
);
456 time_offset
-= delta
;
457 tick_length
+= delta
;
459 /* Check PPS signal */
465 if (time_adjust
> MAX_TICKADJ
) {
466 time_adjust
-= MAX_TICKADJ
;
467 tick_length
+= MAX_TICKADJ_SCALED
;
471 if (time_adjust
< -MAX_TICKADJ
) {
472 time_adjust
+= MAX_TICKADJ
;
473 tick_length
-= MAX_TICKADJ_SCALED
;
477 tick_length
+= (s64
)(time_adjust
* NSEC_PER_USEC
/ NTP_INTERVAL_FREQ
)
482 spin_unlock_irqrestore(&ntp_lock
, flags
);
487 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
488 static void sync_cmos_clock(struct work_struct
*work
);
490 static DECLARE_DELAYED_WORK(sync_cmos_work
, sync_cmos_clock
);
492 static void sync_cmos_clock(struct work_struct
*work
)
494 struct timespec now
, next
;
498 * If we have an externally synchronized Linux clock, then update
499 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
500 * called as close as possible to 500 ms before the new second starts.
501 * This code is run on a timer. If the clock is set, that timer
502 * may not expire at the correct time. Thus, we adjust...
506 * Not synced, exit, do not restart a timer (if one is
507 * running, let it run out).
512 getnstimeofday(&now
);
513 if (abs(now
.tv_nsec
- (NSEC_PER_SEC
/ 2)) <= tick_nsec
/ 2) {
515 #ifdef CONFIG_GENERIC_CMOS_UPDATE
516 fail
= update_persistent_clock(now
);
518 #ifdef CONFIG_RTC_SYSTOHC
520 fail
= rtc_set_ntp_time(now
);
524 next
.tv_nsec
= (NSEC_PER_SEC
/ 2) - now
.tv_nsec
- (TICK_NSEC
/ 2);
525 if (next
.tv_nsec
<= 0)
526 next
.tv_nsec
+= NSEC_PER_SEC
;
528 if (!fail
|| fail
== -ENODEV
)
533 if (next
.tv_nsec
>= NSEC_PER_SEC
) {
535 next
.tv_nsec
-= NSEC_PER_SEC
;
537 schedule_delayed_work(&sync_cmos_work
, timespec_to_jiffies(&next
));
540 static void notify_cmos_timer(void)
542 schedule_delayed_work(&sync_cmos_work
, 0);
546 static inline void notify_cmos_timer(void) { }
551 * Propagate a new txc->status value into the NTP state:
553 static inline void process_adj_status(struct timex
*txc
, struct timespec
*ts
)
555 if ((time_status
& STA_PLL
) && !(txc
->status
& STA_PLL
)) {
556 time_state
= TIME_OK
;
557 time_status
= STA_UNSYNC
;
558 /* restart PPS frequency calibration */
559 pps_reset_freq_interval();
563 * If we turn on PLL adjustments then reset the
564 * reference time to current time.
566 if (!(time_status
& STA_PLL
) && (txc
->status
& STA_PLL
))
567 time_reftime
= get_seconds();
569 /* only set allowed bits */
570 time_status
&= STA_RONLY
;
571 time_status
|= txc
->status
& ~STA_RONLY
;
575 * Called with ntp_lock held, so we can access and modify
576 * all the global NTP state:
578 static inline void process_adjtimex_modes(struct timex
*txc
, struct timespec
*ts
)
580 if (txc
->modes
& ADJ_STATUS
)
581 process_adj_status(txc
, ts
);
583 if (txc
->modes
& ADJ_NANO
)
584 time_status
|= STA_NANO
;
586 if (txc
->modes
& ADJ_MICRO
)
587 time_status
&= ~STA_NANO
;
589 if (txc
->modes
& ADJ_FREQUENCY
) {
590 time_freq
= txc
->freq
* PPM_SCALE
;
591 time_freq
= min(time_freq
, MAXFREQ_SCALED
);
592 time_freq
= max(time_freq
, -MAXFREQ_SCALED
);
593 /* update pps_freq */
594 pps_set_freq(time_freq
);
597 if (txc
->modes
& ADJ_MAXERROR
)
598 time_maxerror
= txc
->maxerror
;
600 if (txc
->modes
& ADJ_ESTERROR
)
601 time_esterror
= txc
->esterror
;
603 if (txc
->modes
& ADJ_TIMECONST
) {
604 time_constant
= txc
->constant
;
605 if (!(time_status
& STA_NANO
))
607 time_constant
= min(time_constant
, (long)MAXTC
);
608 time_constant
= max(time_constant
, 0l);
611 if (txc
->modes
& ADJ_TAI
&& txc
->constant
> 0)
612 time_tai
= txc
->constant
;
614 if (txc
->modes
& ADJ_OFFSET
)
615 ntp_update_offset(txc
->offset
);
617 if (txc
->modes
& ADJ_TICK
)
618 tick_usec
= txc
->tick
;
620 if (txc
->modes
& (ADJ_TICK
|ADJ_FREQUENCY
|ADJ_OFFSET
))
621 ntp_update_frequency();
625 * adjtimex mainly allows reading (and writing, if superuser) of
626 * kernel time-keeping variables. used by xntpd.
628 int do_adjtimex(struct timex
*txc
)
633 /* Validate the data before disabling interrupts */
634 if (txc
->modes
& ADJ_ADJTIME
) {
635 /* singleshot must not be used with any other mode bits */
636 if (!(txc
->modes
& ADJ_OFFSET_SINGLESHOT
))
638 if (!(txc
->modes
& ADJ_OFFSET_READONLY
) &&
639 !capable(CAP_SYS_TIME
))
642 /* In order to modify anything, you gotta be super-user! */
643 if (txc
->modes
&& !capable(CAP_SYS_TIME
))
647 * if the quartz is off by more than 10% then
648 * something is VERY wrong!
650 if (txc
->modes
& ADJ_TICK
&&
651 (txc
->tick
< 900000/USER_HZ
||
652 txc
->tick
> 1100000/USER_HZ
))
656 if (txc
->modes
& ADJ_SETOFFSET
) {
657 struct timespec delta
;
658 delta
.tv_sec
= txc
->time
.tv_sec
;
659 delta
.tv_nsec
= txc
->time
.tv_usec
;
660 if (!capable(CAP_SYS_TIME
))
662 if (!(txc
->modes
& ADJ_NANO
))
663 delta
.tv_nsec
*= 1000;
664 result
= timekeeping_inject_offset(&delta
);
671 spin_lock_irq(&ntp_lock
);
673 if (txc
->modes
& ADJ_ADJTIME
) {
674 long save_adjust
= time_adjust
;
676 if (!(txc
->modes
& ADJ_OFFSET_READONLY
)) {
677 /* adjtime() is independent from ntp_adjtime() */
678 time_adjust
= txc
->offset
;
679 ntp_update_frequency();
681 txc
->offset
= save_adjust
;
684 /* If there are input parameters, then process them: */
686 process_adjtimex_modes(txc
, &ts
);
688 txc
->offset
= shift_right(time_offset
* NTP_INTERVAL_FREQ
,
690 if (!(time_status
& STA_NANO
))
691 txc
->offset
/= NSEC_PER_USEC
;
694 result
= time_state
; /* mostly `TIME_OK' */
695 /* check for errors */
696 if (is_error_status(time_status
))
699 txc
->freq
= shift_right((time_freq
>> PPM_SCALE_INV_SHIFT
) *
700 PPM_SCALE_INV
, NTP_SCALE_SHIFT
);
701 txc
->maxerror
= time_maxerror
;
702 txc
->esterror
= time_esterror
;
703 txc
->status
= time_status
;
704 txc
->constant
= time_constant
;
706 txc
->tolerance
= MAXFREQ_SCALED
/ PPM_SCALE
;
707 txc
->tick
= tick_usec
;
710 /* fill PPS status fields */
713 spin_unlock_irq(&ntp_lock
);
715 txc
->time
.tv_sec
= ts
.tv_sec
;
716 txc
->time
.tv_usec
= ts
.tv_nsec
;
717 if (!(time_status
& STA_NANO
))
718 txc
->time
.tv_usec
/= NSEC_PER_USEC
;
725 #ifdef CONFIG_NTP_PPS
727 /* actually struct pps_normtime is good old struct timespec, but it is
728 * semantically different (and it is the reason why it was invented):
729 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
730 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
731 struct pps_normtime
{
732 __kernel_time_t sec
; /* seconds */
733 long nsec
; /* nanoseconds */
736 /* normalize the timestamp so that nsec is in the
737 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
738 static inline struct pps_normtime
pps_normalize_ts(struct timespec ts
)
740 struct pps_normtime norm
= {
745 if (norm
.nsec
> (NSEC_PER_SEC
>> 1)) {
746 norm
.nsec
-= NSEC_PER_SEC
;
753 /* get current phase correction and jitter */
754 static inline long pps_phase_filter_get(long *jitter
)
756 *jitter
= pps_tf
[0] - pps_tf
[1];
760 /* TODO: test various filters */
764 /* add the sample to the phase filter */
765 static inline void pps_phase_filter_add(long err
)
767 pps_tf
[2] = pps_tf
[1];
768 pps_tf
[1] = pps_tf
[0];
772 /* decrease frequency calibration interval length.
773 * It is halved after four consecutive unstable intervals.
775 static inline void pps_dec_freq_interval(void)
777 if (--pps_intcnt
<= -PPS_INTCOUNT
) {
778 pps_intcnt
= -PPS_INTCOUNT
;
779 if (pps_shift
> PPS_INTMIN
) {
786 /* increase frequency calibration interval length.
787 * It is doubled after four consecutive stable intervals.
789 static inline void pps_inc_freq_interval(void)
791 if (++pps_intcnt
>= PPS_INTCOUNT
) {
792 pps_intcnt
= PPS_INTCOUNT
;
793 if (pps_shift
< PPS_INTMAX
) {
800 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
803 * At the end of the calibration interval the difference between the
804 * first and last MONOTONIC_RAW clock timestamps divided by the length
805 * of the interval becomes the frequency update. If the interval was
806 * too long, the data are discarded.
807 * Returns the difference between old and new frequency values.
809 static long hardpps_update_freq(struct pps_normtime freq_norm
)
811 long delta
, delta_mod
;
814 /* check if the frequency interval was too long */
815 if (freq_norm
.sec
> (2 << pps_shift
)) {
816 time_status
|= STA_PPSERROR
;
818 pps_dec_freq_interval();
819 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
824 /* here the raw frequency offset and wander (stability) is
825 * calculated. If the wander is less than the wander threshold
826 * the interval is increased; otherwise it is decreased.
828 ftemp
= div_s64(((s64
)(-freq_norm
.nsec
)) << NTP_SCALE_SHIFT
,
830 delta
= shift_right(ftemp
- pps_freq
, NTP_SCALE_SHIFT
);
832 if (delta
> PPS_MAXWANDER
|| delta
< -PPS_MAXWANDER
) {
833 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta
);
834 time_status
|= STA_PPSWANDER
;
836 pps_dec_freq_interval();
837 } else { /* good sample */
838 pps_inc_freq_interval();
841 /* the stability metric is calculated as the average of recent
842 * frequency changes, but is used only for performance
847 delta_mod
= -delta_mod
;
848 pps_stabil
+= (div_s64(((s64
)delta_mod
) <<
849 (NTP_SCALE_SHIFT
- SHIFT_USEC
),
850 NSEC_PER_USEC
) - pps_stabil
) >> PPS_INTMIN
;
852 /* if enabled, the system clock frequency is updated */
853 if ((time_status
& STA_PPSFREQ
) != 0 &&
854 (time_status
& STA_FREQHOLD
) == 0) {
855 time_freq
= pps_freq
;
856 ntp_update_frequency();
862 /* correct REALTIME clock phase error against PPS signal */
863 static void hardpps_update_phase(long error
)
865 long correction
= -error
;
868 /* add the sample to the median filter */
869 pps_phase_filter_add(correction
);
870 correction
= pps_phase_filter_get(&jitter
);
872 /* Nominal jitter is due to PPS signal noise. If it exceeds the
873 * threshold, the sample is discarded; otherwise, if so enabled,
874 * the time offset is updated.
876 if (jitter
> (pps_jitter
<< PPS_POPCORN
)) {
877 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
878 jitter
, (pps_jitter
<< PPS_POPCORN
));
879 time_status
|= STA_PPSJITTER
;
881 } else if (time_status
& STA_PPSTIME
) {
882 /* correct the time using the phase offset */
883 time_offset
= div_s64(((s64
)correction
) << NTP_SCALE_SHIFT
,
885 /* cancel running adjtime() */
889 pps_jitter
+= (jitter
- pps_jitter
) >> PPS_INTMIN
;
893 * hardpps() - discipline CPU clock oscillator to external PPS signal
895 * This routine is called at each PPS signal arrival in order to
896 * discipline the CPU clock oscillator to the PPS signal. It takes two
897 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
898 * is used to correct clock phase error and the latter is used to
899 * correct the frequency.
901 * This code is based on David Mills's reference nanokernel
902 * implementation. It was mostly rewritten but keeps the same idea.
904 void hardpps(const struct timespec
*phase_ts
, const struct timespec
*raw_ts
)
906 struct pps_normtime pts_norm
, freq_norm
;
909 pts_norm
= pps_normalize_ts(*phase_ts
);
911 spin_lock_irqsave(&ntp_lock
, flags
);
913 /* clear the error bits, they will be set again if needed */
914 time_status
&= ~(STA_PPSJITTER
| STA_PPSWANDER
| STA_PPSERROR
);
916 /* indicate signal presence */
917 time_status
|= STA_PPSSIGNAL
;
918 pps_valid
= PPS_VALID
;
920 /* when called for the first time,
921 * just start the frequency interval */
922 if (unlikely(pps_fbase
.tv_sec
== 0)) {
924 spin_unlock_irqrestore(&ntp_lock
, flags
);
928 /* ok, now we have a base for frequency calculation */
929 freq_norm
= pps_normalize_ts(timespec_sub(*raw_ts
, pps_fbase
));
931 /* check that the signal is in the range
932 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
933 if ((freq_norm
.sec
== 0) ||
934 (freq_norm
.nsec
> MAXFREQ
* freq_norm
.sec
) ||
935 (freq_norm
.nsec
< -MAXFREQ
* freq_norm
.sec
)) {
936 time_status
|= STA_PPSJITTER
;
937 /* restart the frequency calibration interval */
939 spin_unlock_irqrestore(&ntp_lock
, flags
);
940 pr_err("hardpps: PPSJITTER: bad pulse\n");
946 /* check if the current frequency interval is finished */
947 if (freq_norm
.sec
>= (1 << pps_shift
)) {
949 /* restart the frequency calibration interval */
951 hardpps_update_freq(freq_norm
);
954 hardpps_update_phase(pts_norm
.nsec
);
956 spin_unlock_irqrestore(&ntp_lock
, flags
);
958 EXPORT_SYMBOL(hardpps
);
960 #endif /* CONFIG_NTP_PPS */
962 static int __init
ntp_tick_adj_setup(char *str
)
964 ntp_tick_adj
= simple_strtol(str
, NULL
, 0);
965 ntp_tick_adj
<<= NTP_SCALE_SHIFT
;
970 __setup("ntp_tick_adj=", ntp_tick_adj_setup
);
972 void __init
ntp_init(void)