projects/linux·blob v3.13 · refs

936 lines · 23.0 KiB

1/*
2 * NTP state machine interfaces and logic.
3 *
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
6 * changelogs.
7 */
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>
16#include <linux/mm.h>
17#include <linux/module.h>
18#include <linux/rtc.h>
19
20#include "tick-internal.h"
21#include "ntp_internal.h"
22
23/*
24 * NTP timekeeping variables:
25 *
26 * Note: All of the NTP state is protected by the timekeeping locks.
27 */
28
29
30/* USER_HZ period (usecs): */
31unsigned long tick_usec = TICK_USEC;
32
33/* SHIFTED_HZ period (nsecs): */
34unsigned long tick_nsec;
35
36static u64 tick_length;
37static u64 tick_length_base;
38
39#define MAX_TICKADJ 500LL /* usecs */
40#define MAX_TICKADJ_SCALED \
41 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
42
43/*
44 * phase-lock loop variables
45 */
46
47/*
48 * clock synchronization status
49 *
50 * (TIME_ERROR prevents overwriting the CMOS clock)
51 */
52static int time_state = TIME_OK;
53
54/* clock status bits: */
55static int time_status = STA_UNSYNC;
56
57/* time adjustment (nsecs): */
58static s64 time_offset;
59
60/* pll time constant: */
61static long time_constant = 2;
62
63/* maximum error (usecs): */
64static long time_maxerror = NTP_PHASE_LIMIT;
65
66/* estimated error (usecs): */
67static long time_esterror = NTP_PHASE_LIMIT;
68
69/* frequency offset (scaled nsecs/secs): */
70static s64 time_freq;
71
72/* time at last adjustment (secs): */
73static long time_reftime;
74
75static long time_adjust;
76
77/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
78static s64 ntp_tick_adj;
79
80#ifdef CONFIG_NTP_PPS
81
82/*
83 * The following variables are used when a pulse-per-second (PPS) signal
84 * is available. They establish the engineering parameters of the clock
85 * discipline loop when controlled by the PPS signal.
86 */
87#define PPS_VALID 10 /* PPS signal watchdog max (s) */
88#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
89#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
90#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
91#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
92 increase pps_shift or consecutive bad
93 intervals to decrease it */
94#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
95
96static int pps_valid; /* signal watchdog counter */
97static long pps_tf[3]; /* phase median filter */
98static long pps_jitter; /* current jitter (ns) */
99static struct timespec pps_fbase; /* beginning of the last freq interval */
100static int pps_shift; /* current interval duration (s) (shift) */
101static int pps_intcnt; /* interval counter */
102static s64 pps_freq; /* frequency offset (scaled ns/s) */
103static long pps_stabil; /* current stability (scaled ns/s) */
104
105/*
106 * PPS signal quality monitors
107 */
108static long pps_calcnt; /* calibration intervals */
109static long pps_jitcnt; /* jitter limit exceeded */
110static long pps_stbcnt; /* stability limit exceeded */
111static long pps_errcnt; /* calibration errors */
112
113
114/* PPS kernel consumer compensates the whole phase error immediately.
115 * Otherwise, reduce the offset by a fixed factor times the time constant.
116 */
117static inline s64 ntp_offset_chunk(s64 offset)
118{
119 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
120 return offset;
121 else
122 return shift_right(offset, SHIFT_PLL + time_constant);
123}
124
125static inline void pps_reset_freq_interval(void)
126{
127 /* the PPS calibration interval may end
128 surprisingly early */
129 pps_shift = PPS_INTMIN;
130 pps_intcnt = 0;
131}
132
133/**
134 * pps_clear - Clears the PPS state variables
135 */
136static inline void pps_clear(void)
137{
138 pps_reset_freq_interval();
139 pps_tf[0] = 0;
140 pps_tf[1] = 0;
141 pps_tf[2] = 0;
142 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
143 pps_freq = 0;
144}
145
146/* Decrease pps_valid to indicate that another second has passed since
147 * the last PPS signal. When it reaches 0, indicate that PPS signal is
148 * missing.
149 */
150static inline void pps_dec_valid(void)
151{
152 if (pps_valid > 0)
153 pps_valid--;
154 else {
155 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
156 STA_PPSWANDER | STA_PPSERROR);
157 pps_clear();
158 }
159}
160
161static inline void pps_set_freq(s64 freq)
162{
163 pps_freq = freq;
164}
165
166static inline int is_error_status(int status)
167{
168 return (time_status & (STA_UNSYNC|STA_CLOCKERR))
169 /* PPS signal lost when either PPS time or
170 * PPS frequency synchronization requested
171 */
172 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
173 && !(time_status & STA_PPSSIGNAL))
174 /* PPS jitter exceeded when
175 * PPS time synchronization requested */
176 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
177 == (STA_PPSTIME|STA_PPSJITTER))
178 /* PPS wander exceeded or calibration error when
179 * PPS frequency synchronization requested
180 */
181 || ((time_status & STA_PPSFREQ)
182 && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
183}
184
185static inline void pps_fill_timex(struct timex *txc)
186{
187 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
188 PPM_SCALE_INV, NTP_SCALE_SHIFT);
189 txc->jitter = pps_jitter;
190 if (!(time_status & STA_NANO))
191 txc->jitter /= NSEC_PER_USEC;
192 txc->shift = pps_shift;
193 txc->stabil = pps_stabil;
194 txc->jitcnt = pps_jitcnt;
195 txc->calcnt = pps_calcnt;
196 txc->errcnt = pps_errcnt;
197 txc->stbcnt = pps_stbcnt;
198}
199
200#else /* !CONFIG_NTP_PPS */
201
202static inline s64 ntp_offset_chunk(s64 offset)
203{
204 return shift_right(offset, SHIFT_PLL + time_constant);
205}
206
207static inline void pps_reset_freq_interval(void) {}
208static inline void pps_clear(void) {}
209static inline void pps_dec_valid(void) {}
210static inline void pps_set_freq(s64 freq) {}
211
212static inline int is_error_status(int status)
213{
214 return status & (STA_UNSYNC|STA_CLOCKERR);
215}
216
217static inline void pps_fill_timex(struct timex *txc)
218{
219 /* PPS is not implemented, so these are zero */
220 txc->ppsfreq = 0;
221 txc->jitter = 0;
222 txc->shift = 0;
223 txc->stabil = 0;
224 txc->jitcnt = 0;
225 txc->calcnt = 0;
226 txc->errcnt = 0;
227 txc->stbcnt = 0;
228}
229
230#endif /* CONFIG_NTP_PPS */
231
232
233/**
234 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
235 *
236 */
237static inline int ntp_synced(void)
238{
239 return !(time_status & STA_UNSYNC);
240}
241
242
243/*
244 * NTP methods:
245 */
246
247/*
248 * Update (tick_length, tick_length_base, tick_nsec), based
249 * on (tick_usec, ntp_tick_adj, time_freq):
250 */
251static void ntp_update_frequency(void)
252{
253 u64 second_length;
254 u64 new_base;
255
256 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
257 << NTP_SCALE_SHIFT;
258
259 second_length += ntp_tick_adj;
260 second_length += time_freq;
261
262 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
263 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
264
265 /*
266 * Don't wait for the next second_overflow, apply
267 * the change to the tick length immediately:
268 */
269 tick_length += new_base - tick_length_base;
270 tick_length_base = new_base;
271}
272
273static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
274{
275 time_status &= ~STA_MODE;
276
277 if (secs < MINSEC)
278 return 0;
279
280 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
281 return 0;
282
283 time_status |= STA_MODE;
284
285 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
286}
287
288static void ntp_update_offset(long offset)
289{
290 s64 freq_adj;
291 s64 offset64;
292 long secs;
293
294 if (!(time_status & STA_PLL))
295 return;
296
297 if (!(time_status & STA_NANO))
298 offset *= NSEC_PER_USEC;
299
300 /*
301 * Scale the phase adjustment and
302 * clamp to the operating range.
303 */
304 offset = min(offset, MAXPHASE);
305 offset = max(offset, -MAXPHASE);
306
307 /*
308 * Select how the frequency is to be controlled
309 * and in which mode (PLL or FLL).
310 */
311 secs = get_seconds() - time_reftime;
312 if (unlikely(time_status & STA_FREQHOLD))
313 secs = 0;
314
315 time_reftime = get_seconds();
316
317 offset64 = offset;
318 freq_adj = ntp_update_offset_fll(offset64, secs);
319
320 /*
321 * Clamp update interval to reduce PLL gain with low
322 * sampling rate (e.g. intermittent network connection)
323 * to avoid instability.
324 */
325 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
326 secs = 1 << (SHIFT_PLL + 1 + time_constant);
327
328 freq_adj += (offset64 * secs) <<
329 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
330
331 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
332
333 time_freq = max(freq_adj, -MAXFREQ_SCALED);
334
335 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
336}
337
338/**
339 * ntp_clear - Clears the NTP state variables
340 */
341void ntp_clear(void)
342{
343 time_adjust = 0; /* stop active adjtime() */
344 time_status |= STA_UNSYNC;
345 time_maxerror = NTP_PHASE_LIMIT;
346 time_esterror = NTP_PHASE_LIMIT;
347
348 ntp_update_frequency();
349
350 tick_length = tick_length_base;
351 time_offset = 0;
352
353 /* Clear PPS state variables */
354 pps_clear();
355}
356
357
358u64 ntp_tick_length(void)
359{
360 return tick_length;
361}
362
363
364/*
365 * this routine handles the overflow of the microsecond field
366 *
367 * The tricky bits of code to handle the accurate clock support
368 * were provided by Dave Mills ([email protected]) of NTP fame.
369 * They were originally developed for SUN and DEC kernels.
370 * All the kudos should go to Dave for this stuff.
371 *
372 * Also handles leap second processing, and returns leap offset
373 */
374int second_overflow(unsigned long secs)
375{
376 s64 delta;
377 int leap = 0;
378
379 /*
380 * Leap second processing. If in leap-insert state at the end of the
381 * day, the system clock is set back one second; if in leap-delete
382 * state, the system clock is set ahead one second.
383 */
384 switch (time_state) {
385 case TIME_OK:
386 if (time_status & STA_INS)
387 time_state = TIME_INS;
388 else if (time_status & STA_DEL)
389 time_state = TIME_DEL;
390 break;
391 case TIME_INS:
392 if (!(time_status & STA_INS))
393 time_state = TIME_OK;
394 else if (secs % 86400 == 0) {
395 leap = -1;
396 time_state = TIME_OOP;
397 printk(KERN_NOTICE
398 "Clock: inserting leap second 23:59:60 UTC\n");
399 }
400 break;
401 case TIME_DEL:
402 if (!(time_status & STA_DEL))
403 time_state = TIME_OK;
404 else if ((secs + 1) % 86400 == 0) {
405 leap = 1;
406 time_state = TIME_WAIT;
407 printk(KERN_NOTICE
408 "Clock: deleting leap second 23:59:59 UTC\n");
409 }
410 break;
411 case TIME_OOP:
412 time_state = TIME_WAIT;
413 break;
414
415 case TIME_WAIT:
416 if (!(time_status & (STA_INS | STA_DEL)))
417 time_state = TIME_OK;
418 break;
419 }
420
421
422 /* Bump the maxerror field */
423 time_maxerror += MAXFREQ / NSEC_PER_USEC;
424 if (time_maxerror > NTP_PHASE_LIMIT) {
425 time_maxerror = NTP_PHASE_LIMIT;
426 time_status |= STA_UNSYNC;
427 }
428
429 /* Compute the phase adjustment for the next second */
430 tick_length = tick_length_base;
431
432 delta = ntp_offset_chunk(time_offset);
433 time_offset -= delta;
434 tick_length += delta;
435
436 /* Check PPS signal */
437 pps_dec_valid();
438
439 if (!time_adjust)
440 goto out;
441
442 if (time_adjust > MAX_TICKADJ) {
443 time_adjust -= MAX_TICKADJ;
444 tick_length += MAX_TICKADJ_SCALED;
445 goto out;
446 }
447
448 if (time_adjust < -MAX_TICKADJ) {
449 time_adjust += MAX_TICKADJ;
450 tick_length -= MAX_TICKADJ_SCALED;
451 goto out;
452 }
453
454 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
455 << NTP_SCALE_SHIFT;
456 time_adjust = 0;
457
458out:
459 return leap;
460}
461
462#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
463static void sync_cmos_clock(struct work_struct *work);
464
465static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
466
467static void sync_cmos_clock(struct work_struct *work)
468{
469 struct timespec now, next;
470 int fail = 1;
471
472 /*
473 * If we have an externally synchronized Linux clock, then update
474 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
475 * called as close as possible to 500 ms before the new second starts.
476 * This code is run on a timer. If the clock is set, that timer
477 * may not expire at the correct time. Thus, we adjust...
478 * We want the clock to be within a couple of ticks from the target.
479 */
480 if (!ntp_synced()) {
481 /*
482 * Not synced, exit, do not restart a timer (if one is
483 * running, let it run out).
484 */
485 return;
486 }
487
488 getnstimeofday(&now);
489 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) {
490 struct timespec adjust = now;
491
492 fail = -ENODEV;
493 if (persistent_clock_is_local)
494 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
495#ifdef CONFIG_GENERIC_CMOS_UPDATE
496 fail = update_persistent_clock(adjust);
497#endif
498#ifdef CONFIG_RTC_SYSTOHC
499 if (fail == -ENODEV)
500 fail = rtc_set_ntp_time(adjust);
501#endif
502 }
503
504 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
505 if (next.tv_nsec <= 0)
506 next.tv_nsec += NSEC_PER_SEC;
507
508 if (!fail || fail == -ENODEV)
509 next.tv_sec = 659;
510 else
511 next.tv_sec = 0;
512
513 if (next.tv_nsec >= NSEC_PER_SEC) {
514 next.tv_sec++;
515 next.tv_nsec -= NSEC_PER_SEC;
516 }
517 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
518}
519
520void ntp_notify_cmos_timer(void)
521{
522 schedule_delayed_work(&sync_cmos_work, 0);
523}
524
525#else
526void ntp_notify_cmos_timer(void) { }
527#endif
528
529
530/*
531 * Propagate a new txc->status value into the NTP state:
532 */
533static inline void process_adj_status(struct timex *txc, struct timespec *ts)
534{
535 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
536 time_state = TIME_OK;
537 time_status = STA_UNSYNC;
538 /* restart PPS frequency calibration */
539 pps_reset_freq_interval();
540 }
541
542 /*
543 * If we turn on PLL adjustments then reset the
544 * reference time to current time.
545 */
546 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
547 time_reftime = get_seconds();
548
549 /* only set allowed bits */
550 time_status &= STA_RONLY;
551 time_status |= txc->status & ~STA_RONLY;
552}
553
554
555static inline void process_adjtimex_modes(struct timex *txc,
556 struct timespec *ts,
557 s32 *time_tai)
558{
559 if (txc->modes & ADJ_STATUS)
560 process_adj_status(txc, ts);
561
562 if (txc->modes & ADJ_NANO)
563 time_status |= STA_NANO;
564
565 if (txc->modes & ADJ_MICRO)
566 time_status &= ~STA_NANO;
567
568 if (txc->modes & ADJ_FREQUENCY) {
569 time_freq = txc->freq * PPM_SCALE;
570 time_freq = min(time_freq, MAXFREQ_SCALED);
571 time_freq = max(time_freq, -MAXFREQ_SCALED);
572 /* update pps_freq */
573 pps_set_freq(time_freq);
574 }
575
576 if (txc->modes & ADJ_MAXERROR)
577 time_maxerror = txc->maxerror;
578
579 if (txc->modes & ADJ_ESTERROR)
580 time_esterror = txc->esterror;
581
582 if (txc->modes & ADJ_TIMECONST) {
583 time_constant = txc->constant;
584 if (!(time_status & STA_NANO))
585 time_constant += 4;
586 time_constant = min(time_constant, (long)MAXTC);
587 time_constant = max(time_constant, 0l);
588 }
589
590 if (txc->modes & ADJ_TAI && txc->constant > 0)
591 *time_tai = txc->constant;
592
593 if (txc->modes & ADJ_OFFSET)
594 ntp_update_offset(txc->offset);
595
596 if (txc->modes & ADJ_TICK)
597 tick_usec = txc->tick;
598
599 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
600 ntp_update_frequency();
601}
602
603
604
605/**
606 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
607 */
608int ntp_validate_timex(struct timex *txc)
609{
610 if (txc->modes & ADJ_ADJTIME) {
611 /* singleshot must not be used with any other mode bits */
612 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
613 return -EINVAL;
614 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
615 !capable(CAP_SYS_TIME))
616 return -EPERM;
617 } else {
618 /* In order to modify anything, you gotta be super-user! */
619 if (txc->modes && !capable(CAP_SYS_TIME))
620 return -EPERM;
621 /*
622 * if the quartz is off by more than 10% then
623 * something is VERY wrong!
624 */
625 if (txc->modes & ADJ_TICK &&
626 (txc->tick < 900000/USER_HZ ||
627 txc->tick > 1100000/USER_HZ))
628 return -EINVAL;
629 }
630
631 if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
632 return -EPERM;
633
634 return 0;
635}
636
637
638/*
639 * adjtimex mainly allows reading (and writing, if superuser) of
640 * kernel time-keeping variables. used by xntpd.
641 */
642int __do_adjtimex(struct timex *txc, struct timespec *ts, s32 *time_tai)
643{
644 int result;
645
646 if (txc->modes & ADJ_ADJTIME) {
647 long save_adjust = time_adjust;
648
649 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
650 /* adjtime() is independent from ntp_adjtime() */
651 time_adjust = txc->offset;
652 ntp_update_frequency();
653 }
654 txc->offset = save_adjust;
655 } else {
656
657 /* If there are input parameters, then process them: */
658 if (txc->modes)
659 process_adjtimex_modes(txc, ts, time_tai);
660
661 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
662 NTP_SCALE_SHIFT);
663 if (!(time_status & STA_NANO))
664 txc->offset /= NSEC_PER_USEC;
665 }
666
667 result = time_state; /* mostly `TIME_OK' */
668 /* check for errors */
669 if (is_error_status(time_status))
670 result = TIME_ERROR;
671
672 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
673 PPM_SCALE_INV, NTP_SCALE_SHIFT);
674 txc->maxerror = time_maxerror;
675 txc->esterror = time_esterror;
676 txc->status = time_status;
677 txc->constant = time_constant;
678 txc->precision = 1;
679 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
680 txc->tick = tick_usec;
681 txc->tai = *time_tai;
682
683 /* fill PPS status fields */
684 pps_fill_timex(txc);
685
686 txc->time.tv_sec = ts->tv_sec;
687 txc->time.tv_usec = ts->tv_nsec;
688 if (!(time_status & STA_NANO))
689 txc->time.tv_usec /= NSEC_PER_USEC;
690
691 return result;
692}
693
694#ifdef CONFIG_NTP_PPS
695
696/* actually struct pps_normtime is good old struct timespec, but it is
697 * semantically different (and it is the reason why it was invented):
698 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
699 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
700struct pps_normtime {
701 __kernel_time_t sec; /* seconds */
702 long nsec; /* nanoseconds */
703};
704
705/* normalize the timestamp so that nsec is in the
706 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
707static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
708{
709 struct pps_normtime norm = {
710 .sec = ts.tv_sec,
711 .nsec = ts.tv_nsec
712 };
713
714 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
715 norm.nsec -= NSEC_PER_SEC;
716 norm.sec++;
717 }
718
719 return norm;
720}
721
722/* get current phase correction and jitter */
723static inline long pps_phase_filter_get(long *jitter)
724{
725 *jitter = pps_tf[0] - pps_tf[1];
726 if (*jitter < 0)
727 *jitter = -*jitter;
728
729 /* TODO: test various filters */
730 return pps_tf[0];
731}
732
733/* add the sample to the phase filter */
734static inline void pps_phase_filter_add(long err)
735{
736 pps_tf[2] = pps_tf[1];
737 pps_tf[1] = pps_tf[0];
738 pps_tf[0] = err;
739}
740
741/* decrease frequency calibration interval length.
742 * It is halved after four consecutive unstable intervals.
743 */
744static inline void pps_dec_freq_interval(void)
745{
746 if (--pps_intcnt <= -PPS_INTCOUNT) {
747 pps_intcnt = -PPS_INTCOUNT;
748 if (pps_shift > PPS_INTMIN) {
749 pps_shift--;
750 pps_intcnt = 0;
751 }
752 }
753}
754
755/* increase frequency calibration interval length.
756 * It is doubled after four consecutive stable intervals.
757 */
758static inline void pps_inc_freq_interval(void)
759{
760 if (++pps_intcnt >= PPS_INTCOUNT) {
761 pps_intcnt = PPS_INTCOUNT;
762 if (pps_shift < PPS_INTMAX) {
763 pps_shift++;
764 pps_intcnt = 0;
765 }
766 }
767}
768
769/* update clock frequency based on MONOTONIC_RAW clock PPS signal
770 * timestamps
771 *
772 * At the end of the calibration interval the difference between the
773 * first and last MONOTONIC_RAW clock timestamps divided by the length
774 * of the interval becomes the frequency update. If the interval was
775 * too long, the data are discarded.
776 * Returns the difference between old and new frequency values.
777 */
778static long hardpps_update_freq(struct pps_normtime freq_norm)
779{
780 long delta, delta_mod;
781 s64 ftemp;
782
783 /* check if the frequency interval was too long */
784 if (freq_norm.sec > (2 << pps_shift)) {
785 time_status |= STA_PPSERROR;
786 pps_errcnt++;
787 pps_dec_freq_interval();
788 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
789 freq_norm.sec);
790 return 0;
791 }
792
793 /* here the raw frequency offset and wander (stability) is
794 * calculated. If the wander is less than the wander threshold
795 * the interval is increased; otherwise it is decreased.
796 */
797 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
798 freq_norm.sec);
799 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
800 pps_freq = ftemp;
801 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
802 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
803 time_status |= STA_PPSWANDER;
804 pps_stbcnt++;
805 pps_dec_freq_interval();
806 } else { /* good sample */
807 pps_inc_freq_interval();
808 }
809
810 /* the stability metric is calculated as the average of recent
811 * frequency changes, but is used only for performance
812 * monitoring
813 */
814 delta_mod = delta;
815 if (delta_mod < 0)
816 delta_mod = -delta_mod;
817 pps_stabil += (div_s64(((s64)delta_mod) <<
818 (NTP_SCALE_SHIFT - SHIFT_USEC),
819 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
820
821 /* if enabled, the system clock frequency is updated */
822 if ((time_status & STA_PPSFREQ) != 0 &&
823 (time_status & STA_FREQHOLD) == 0) {
824 time_freq = pps_freq;
825 ntp_update_frequency();
826 }
827
828 return delta;
829}
830
831/* correct REALTIME clock phase error against PPS signal */
832static void hardpps_update_phase(long error)
833{
834 long correction = -error;
835 long jitter;
836
837 /* add the sample to the median filter */
838 pps_phase_filter_add(correction);
839 correction = pps_phase_filter_get(&jitter);
840
841 /* Nominal jitter is due to PPS signal noise. If it exceeds the
842 * threshold, the sample is discarded; otherwise, if so enabled,
843 * the time offset is updated.
844 */
845 if (jitter > (pps_jitter << PPS_POPCORN)) {
846 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
847 jitter, (pps_jitter << PPS_POPCORN));
848 time_status |= STA_PPSJITTER;
849 pps_jitcnt++;
850 } else if (time_status & STA_PPSTIME) {
851 /* correct the time using the phase offset */
852 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
853 NTP_INTERVAL_FREQ);
854 /* cancel running adjtime() */
855 time_adjust = 0;
856 }
857 /* update jitter */
858 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
859}
860
861/*
862 * __hardpps() - discipline CPU clock oscillator to external PPS signal
863 *
864 * This routine is called at each PPS signal arrival in order to
865 * discipline the CPU clock oscillator to the PPS signal. It takes two
866 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
867 * is used to correct clock phase error and the latter is used to
868 * correct the frequency.
869 *
870 * This code is based on David Mills's reference nanokernel
871 * implementation. It was mostly rewritten but keeps the same idea.
872 */
873void __hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
874{
875 struct pps_normtime pts_norm, freq_norm;
876
877 pts_norm = pps_normalize_ts(*phase_ts);
878
879 /* clear the error bits, they will be set again if needed */
880 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
881
882 /* indicate signal presence */
883 time_status |= STA_PPSSIGNAL;
884 pps_valid = PPS_VALID;
885
886 /* when called for the first time,
887 * just start the frequency interval */
888 if (unlikely(pps_fbase.tv_sec == 0)) {
889 pps_fbase = *raw_ts;
890 return;
891 }
892
893 /* ok, now we have a base for frequency calculation */
894 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
895
896 /* check that the signal is in the range
897 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
898 if ((freq_norm.sec == 0) ||
899 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
900 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
901 time_status |= STA_PPSJITTER;
902 /* restart the frequency calibration interval */
903 pps_fbase = *raw_ts;
904 pr_err("hardpps: PPSJITTER: bad pulse\n");
905 return;
906 }
907
908 /* signal is ok */
909
910 /* check if the current frequency interval is finished */
911 if (freq_norm.sec >= (1 << pps_shift)) {
912 pps_calcnt++;
913 /* restart the frequency calibration interval */
914 pps_fbase = *raw_ts;
915 hardpps_update_freq(freq_norm);
916 }
917
918 hardpps_update_phase(pts_norm.nsec);
919
920}
921#endif /* CONFIG_NTP_PPS */
922
923static int __init ntp_tick_adj_setup(char *str)
924{
925 ntp_tick_adj = simple_strtol(str, NULL, 0);
926 ntp_tick_adj <<= NTP_SCALE_SHIFT;
927
928 return 1;
929}
930
931__setup("ntp_tick_adj=", ntp_tick_adj_setup);
932
933void __init ntp_init(void)
934{
935 ntp_clear();
936}