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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
19#include "tick-internal.h"
20
21/*
22 * NTP timekeeping variables:
23 */
24
25DEFINE_SPINLOCK(ntp_lock);
26
27
28/* USER_HZ period (usecs): */
29unsigned long tick_usec = TICK_USEC;
30
31/* ACTHZ period (nsecs): */
32unsigned long tick_nsec;
33
34static u64 tick_length;
35static u64 tick_length_base;
36
37#define MAX_TICKADJ 500LL /* usecs */
38#define MAX_TICKADJ_SCALED \
39 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
40
41/*
42 * phase-lock loop variables
43 */
44
45/*
46 * clock synchronization status
47 *
48 * (TIME_ERROR prevents overwriting the CMOS clock)
49 */
50static int time_state = TIME_OK;
51
52/* clock status bits: */
53static int time_status = STA_UNSYNC;
54
55/* TAI offset (secs): */
56static long time_tai;
57
58/* time adjustment (nsecs): */
59static s64 time_offset;
60
61/* pll time constant: */
62static long time_constant = 2;
63
64/* maximum error (usecs): */
65static long time_maxerror = NTP_PHASE_LIMIT;
66
67/* estimated error (usecs): */
68static long time_esterror = NTP_PHASE_LIMIT;
69
70/* frequency offset (scaled nsecs/secs): */
71static s64 time_freq;
72
73/* time at last adjustment (secs): */
74static long time_reftime;
75
76static long time_adjust;
77
78/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
79static s64 ntp_tick_adj;
80
81#ifdef CONFIG_NTP_PPS
82
83/*
84 * The following variables are used when a pulse-per-second (PPS) signal
85 * is available. They establish the engineering parameters of the clock
86 * discipline loop when controlled by the PPS signal.
87 */
88#define PPS_VALID 10 /* PPS signal watchdog max (s) */
89#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
90#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
91#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
92#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
93 increase pps_shift or consecutive bad
94 intervals to decrease it */
95#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
96
97static int pps_valid; /* signal watchdog counter */
98static long pps_tf[3]; /* phase median filter */
99static long pps_jitter; /* current jitter (ns) */
100static struct timespec pps_fbase; /* beginning of the last freq interval */
101static int pps_shift; /* current interval duration (s) (shift) */
102static int pps_intcnt; /* interval counter */
103static s64 pps_freq; /* frequency offset (scaled ns/s) */
104static long pps_stabil; /* current stability (scaled ns/s) */
105
106/*
107 * PPS signal quality monitors
108 */
109static long pps_calcnt; /* calibration intervals */
110static long pps_jitcnt; /* jitter limit exceeded */
111static long pps_stbcnt; /* stability limit exceeded */
112static long pps_errcnt; /* calibration errors */
113
114
115/* PPS kernel consumer compensates the whole phase error immediately.
116 * Otherwise, reduce the offset by a fixed factor times the time constant.
117 */
118static inline s64 ntp_offset_chunk(s64 offset)
119{
120 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
121 return offset;
122 else
123 return shift_right(offset, SHIFT_PLL + time_constant);
124}
125
126static inline void pps_reset_freq_interval(void)
127{
128 /* the PPS calibration interval may end
129 surprisingly early */
130 pps_shift = PPS_INTMIN;
131 pps_intcnt = 0;
132}
133
134/**
135 * pps_clear - Clears the PPS state variables
136 *
137 * Must be called while holding a write on the ntp_lock
138 */
139static inline void pps_clear(void)
140{
141 pps_reset_freq_interval();
142 pps_tf[0] = 0;
143 pps_tf[1] = 0;
144 pps_tf[2] = 0;
145 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
146 pps_freq = 0;
147}
148
149/* Decrease pps_valid to indicate that another second has passed since
150 * the last PPS signal. When it reaches 0, indicate that PPS signal is
151 * missing.
152 *
153 * Must be called while holding a write on the ntp_lock
154 */
155static inline void pps_dec_valid(void)
156{
157 if (pps_valid > 0)
158 pps_valid--;
159 else {
160 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
161 STA_PPSWANDER | STA_PPSERROR);
162 pps_clear();
163 }
164}
165
166static inline void pps_set_freq(s64 freq)
167{
168 pps_freq = freq;
169}
170
171static inline int is_error_status(int status)
172{
173 return (time_status & (STA_UNSYNC|STA_CLOCKERR))
174 /* PPS signal lost when either PPS time or
175 * PPS frequency synchronization requested
176 */
177 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
178 && !(time_status & STA_PPSSIGNAL))
179 /* PPS jitter exceeded when
180 * PPS time synchronization requested */
181 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
182 == (STA_PPSTIME|STA_PPSJITTER))
183 /* PPS wander exceeded or calibration error when
184 * PPS frequency synchronization requested
185 */
186 || ((time_status & STA_PPSFREQ)
187 && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
188}
189
190static inline void pps_fill_timex(struct timex *txc)
191{
192 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
193 PPM_SCALE_INV, NTP_SCALE_SHIFT);
194 txc->jitter = pps_jitter;
195 if (!(time_status & STA_NANO))
196 txc->jitter /= NSEC_PER_USEC;
197 txc->shift = pps_shift;
198 txc->stabil = pps_stabil;
199 txc->jitcnt = pps_jitcnt;
200 txc->calcnt = pps_calcnt;
201 txc->errcnt = pps_errcnt;
202 txc->stbcnt = pps_stbcnt;
203}
204
205#else /* !CONFIG_NTP_PPS */
206
207static inline s64 ntp_offset_chunk(s64 offset)
208{
209 return shift_right(offset, SHIFT_PLL + time_constant);
210}
211
212static inline void pps_reset_freq_interval(void) {}
213static inline void pps_clear(void) {}
214static inline void pps_dec_valid(void) {}
215static inline void pps_set_freq(s64 freq) {}
216
217static inline int is_error_status(int status)
218{
219 return status & (STA_UNSYNC|STA_CLOCKERR);
220}
221
222static inline void pps_fill_timex(struct timex *txc)
223{
224 /* PPS is not implemented, so these are zero */
225 txc->ppsfreq = 0;
226 txc->jitter = 0;
227 txc->shift = 0;
228 txc->stabil = 0;
229 txc->jitcnt = 0;
230 txc->calcnt = 0;
231 txc->errcnt = 0;
232 txc->stbcnt = 0;
233}
234
235#endif /* CONFIG_NTP_PPS */
236
237
238/**
239 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
240 *
241 */
242static inline int ntp_synced(void)
243{
244 return !(time_status & STA_UNSYNC);
245}
246
247
248/*
249 * NTP methods:
250 */
251
252/*
253 * Update (tick_length, tick_length_base, tick_nsec), based
254 * on (tick_usec, ntp_tick_adj, time_freq):
255 */
256static void ntp_update_frequency(void)
257{
258 u64 second_length;
259 u64 new_base;
260
261 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
262 << NTP_SCALE_SHIFT;
263
264 second_length += ntp_tick_adj;
265 second_length += time_freq;
266
267 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
268 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
269
270 /*
271 * Don't wait for the next second_overflow, apply
272 * the change to the tick length immediately:
273 */
274 tick_length += new_base - tick_length_base;
275 tick_length_base = new_base;
276}
277
278static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
279{
280 time_status &= ~STA_MODE;
281
282 if (secs < MINSEC)
283 return 0;
284
285 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
286 return 0;
287
288 time_status |= STA_MODE;
289
290 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
291}
292
293static void ntp_update_offset(long offset)
294{
295 s64 freq_adj;
296 s64 offset64;
297 long secs;
298
299 if (!(time_status & STA_PLL))
300 return;
301
302 if (!(time_status & STA_NANO))
303 offset *= NSEC_PER_USEC;
304
305 /*
306 * Scale the phase adjustment and
307 * clamp to the operating range.
308 */
309 offset = min(offset, MAXPHASE);
310 offset = max(offset, -MAXPHASE);
311
312 /*
313 * Select how the frequency is to be controlled
314 * and in which mode (PLL or FLL).
315 */
316 secs = get_seconds() - time_reftime;
317 if (unlikely(time_status & STA_FREQHOLD))
318 secs = 0;
319
320 time_reftime = get_seconds();
321
322 offset64 = offset;
323 freq_adj = ntp_update_offset_fll(offset64, secs);
324
325 /*
326 * Clamp update interval to reduce PLL gain with low
327 * sampling rate (e.g. intermittent network connection)
328 * to avoid instability.
329 */
330 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
331 secs = 1 << (SHIFT_PLL + 1 + time_constant);
332
333 freq_adj += (offset64 * secs) <<
334 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
335
336 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
337
338 time_freq = max(freq_adj, -MAXFREQ_SCALED);
339
340 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
341}
342
343/**
344 * ntp_clear - Clears the NTP state variables
345 */
346void ntp_clear(void)
347{
348 unsigned long flags;
349
350 spin_lock_irqsave(&ntp_lock, flags);
351
352 time_adjust = 0; /* stop active adjtime() */
353 time_status |= STA_UNSYNC;
354 time_maxerror = NTP_PHASE_LIMIT;
355 time_esterror = NTP_PHASE_LIMIT;
356
357 ntp_update_frequency();
358
359 tick_length = tick_length_base;
360 time_offset = 0;
361
362 /* Clear PPS state variables */
363 pps_clear();
364 spin_unlock_irqrestore(&ntp_lock, flags);
365
366}
367
368
369u64 ntp_tick_length(void)
370{
371 unsigned long flags;
372 s64 ret;
373
374 spin_lock_irqsave(&ntp_lock, flags);
375 ret = tick_length;
376 spin_unlock_irqrestore(&ntp_lock, flags);
377 return ret;
378}
379
380
381/*
382 * this routine handles the overflow of the microsecond field
383 *
384 * The tricky bits of code to handle the accurate clock support
385 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
386 * They were originally developed for SUN and DEC kernels.
387 * All the kudos should go to Dave for this stuff.
388 *
389 * Also handles leap second processing, and returns leap offset
390 */
391int second_overflow(unsigned long secs)
392{
393 s64 delta;
394 int leap = 0;
395 unsigned long flags;
396
397 spin_lock_irqsave(&ntp_lock, flags);
398
399 /*
400 * Leap second processing. If in leap-insert state at the end of the
401 * day, the system clock is set back one second; if in leap-delete
402 * state, the system clock is set ahead one second.
403 */
404 switch (time_state) {
405 case TIME_OK:
406 if (time_status & STA_INS)
407 time_state = TIME_INS;
408 else if (time_status & STA_DEL)
409 time_state = TIME_DEL;
410 break;
411 case TIME_INS:
412 if (!(time_status & STA_INS))
413 time_state = TIME_OK;
414 else if (secs % 86400 == 0) {
415 leap = -1;
416 time_state = TIME_OOP;
417 time_tai++;
418 printk(KERN_NOTICE
419 "Clock: inserting leap second 23:59:60 UTC\n");
420 }
421 break;
422 case TIME_DEL:
423 if (!(time_status & STA_DEL))
424 time_state = TIME_OK;
425 else if ((secs + 1) % 86400 == 0) {
426 leap = 1;
427 time_tai--;
428 time_state = TIME_WAIT;
429 printk(KERN_NOTICE
430 "Clock: deleting leap second 23:59:59 UTC\n");
431 }
432 break;
433 case TIME_OOP:
434 time_state = TIME_WAIT;
435 break;
436
437 case TIME_WAIT:
438 if (!(time_status & (STA_INS | STA_DEL)))
439 time_state = TIME_OK;
440 break;
441 }
442
443
444 /* Bump the maxerror field */
445 time_maxerror += MAXFREQ / NSEC_PER_USEC;
446 if (time_maxerror > NTP_PHASE_LIMIT) {
447 time_maxerror = NTP_PHASE_LIMIT;
448 time_status |= STA_UNSYNC;
449 }
450
451 /* Compute the phase adjustment for the next second */
452 tick_length = tick_length_base;
453
454 delta = ntp_offset_chunk(time_offset);
455 time_offset -= delta;
456 tick_length += delta;
457
458 /* Check PPS signal */
459 pps_dec_valid();
460
461 if (!time_adjust)
462 goto out;
463
464 if (time_adjust > MAX_TICKADJ) {
465 time_adjust -= MAX_TICKADJ;
466 tick_length += MAX_TICKADJ_SCALED;
467 goto out;
468 }
469
470 if (time_adjust < -MAX_TICKADJ) {
471 time_adjust += MAX_TICKADJ;
472 tick_length -= MAX_TICKADJ_SCALED;
473 goto out;
474 }
475
476 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
477 << NTP_SCALE_SHIFT;
478 time_adjust = 0;
479
480out:
481 spin_unlock_irqrestore(&ntp_lock, flags);
482
483 return leap;
484}
485
486#ifdef CONFIG_GENERIC_CMOS_UPDATE
487
488static void sync_cmos_clock(struct work_struct *work);
489
490static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
491
492static void sync_cmos_clock(struct work_struct *work)
493{
494 struct timespec now, next;
495 int fail = 1;
496
497 /*
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...
503 */
504 if (!ntp_synced()) {
505 /*
506 * Not synced, exit, do not restart a timer (if one is
507 * running, let it run out).
508 */
509 return;
510 }
511
512 getnstimeofday(&now);
513 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
514 fail = update_persistent_clock(now);
515
516 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
517 if (next.tv_nsec <= 0)
518 next.tv_nsec += NSEC_PER_SEC;
519
520 if (!fail)
521 next.tv_sec = 659;
522 else
523 next.tv_sec = 0;
524
525 if (next.tv_nsec >= NSEC_PER_SEC) {
526 next.tv_sec++;
527 next.tv_nsec -= NSEC_PER_SEC;
528 }
529 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
530}
531
532static void notify_cmos_timer(void)
533{
534 schedule_delayed_work(&sync_cmos_work, 0);
535}
536
537#else
538static inline void notify_cmos_timer(void) { }
539#endif
540
541
542/*
543 * Propagate a new txc->status value into the NTP state:
544 */
545static inline void process_adj_status(struct timex *txc, struct timespec *ts)
546{
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();
552 }
553
554 /*
555 * If we turn on PLL adjustments then reset the
556 * reference time to current time.
557 */
558 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
559 time_reftime = get_seconds();
560
561 /* only set allowed bits */
562 time_status &= STA_RONLY;
563 time_status |= txc->status & ~STA_RONLY;
564}
565
566/*
567 * Called with ntp_lock held, so we can access and modify
568 * all the global NTP state:
569 */
570static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
571{
572 if (txc->modes & ADJ_STATUS)
573 process_adj_status(txc, ts);
574
575 if (txc->modes & ADJ_NANO)
576 time_status |= STA_NANO;
577
578 if (txc->modes & ADJ_MICRO)
579 time_status &= ~STA_NANO;
580
581 if (txc->modes & ADJ_FREQUENCY) {
582 time_freq = txc->freq * PPM_SCALE;
583 time_freq = min(time_freq, MAXFREQ_SCALED);
584 time_freq = max(time_freq, -MAXFREQ_SCALED);
585 /* update pps_freq */
586 pps_set_freq(time_freq);
587 }
588
589 if (txc->modes & ADJ_MAXERROR)
590 time_maxerror = txc->maxerror;
591
592 if (txc->modes & ADJ_ESTERROR)
593 time_esterror = txc->esterror;
594
595 if (txc->modes & ADJ_TIMECONST) {
596 time_constant = txc->constant;
597 if (!(time_status & STA_NANO))
598 time_constant += 4;
599 time_constant = min(time_constant, (long)MAXTC);
600 time_constant = max(time_constant, 0l);
601 }
602
603 if (txc->modes & ADJ_TAI && txc->constant > 0)
604 time_tai = txc->constant;
605
606 if (txc->modes & ADJ_OFFSET)
607 ntp_update_offset(txc->offset);
608
609 if (txc->modes & ADJ_TICK)
610 tick_usec = txc->tick;
611
612 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
613 ntp_update_frequency();
614}
615
616/*
617 * adjtimex mainly allows reading (and writing, if superuser) of
618 * kernel time-keeping variables. used by xntpd.
619 */
620int do_adjtimex(struct timex *txc)
621{
622 struct timespec ts;
623 int result;
624
625 /* Validate the data before disabling interrupts */
626 if (txc->modes & ADJ_ADJTIME) {
627 /* singleshot must not be used with any other mode bits */
628 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
629 return -EINVAL;
630 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
631 !capable(CAP_SYS_TIME))
632 return -EPERM;
633 } else {
634 /* In order to modify anything, you gotta be super-user! */
635 if (txc->modes && !capable(CAP_SYS_TIME))
636 return -EPERM;
637
638 /*
639 * if the quartz is off by more than 10% then
640 * something is VERY wrong!
641 */
642 if (txc->modes & ADJ_TICK &&
643 (txc->tick < 900000/USER_HZ ||
644 txc->tick > 1100000/USER_HZ))
645 return -EINVAL;
646 }
647
648 if (txc->modes & ADJ_SETOFFSET) {
649 struct timespec delta;
650 delta.tv_sec = txc->time.tv_sec;
651 delta.tv_nsec = txc->time.tv_usec;
652 if (!capable(CAP_SYS_TIME))
653 return -EPERM;
654 if (!(txc->modes & ADJ_NANO))
655 delta.tv_nsec *= 1000;
656 result = timekeeping_inject_offset(&delta);
657 if (result)
658 return result;
659 }
660
661 getnstimeofday(&ts);
662
663 spin_lock_irq(&ntp_lock);
664
665 if (txc->modes & ADJ_ADJTIME) {
666 long save_adjust = time_adjust;
667
668 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
669 /* adjtime() is independent from ntp_adjtime() */
670 time_adjust = txc->offset;
671 ntp_update_frequency();
672 }
673 txc->offset = save_adjust;
674 } else {
675
676 /* If there are input parameters, then process them: */
677 if (txc->modes)
678 process_adjtimex_modes(txc, &ts);
679
680 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
681 NTP_SCALE_SHIFT);
682 if (!(time_status & STA_NANO))
683 txc->offset /= NSEC_PER_USEC;
684 }
685
686 result = time_state; /* mostly `TIME_OK' */
687 /* check for errors */
688 if (is_error_status(time_status))
689 result = TIME_ERROR;
690
691 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
692 PPM_SCALE_INV, NTP_SCALE_SHIFT);
693 txc->maxerror = time_maxerror;
694 txc->esterror = time_esterror;
695 txc->status = time_status;
696 txc->constant = time_constant;
697 txc->precision = 1;
698 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
699 txc->tick = tick_usec;
700 txc->tai = time_tai;
701
702 /* fill PPS status fields */
703 pps_fill_timex(txc);
704
705 spin_unlock_irq(&ntp_lock);
706
707 txc->time.tv_sec = ts.tv_sec;
708 txc->time.tv_usec = ts.tv_nsec;
709 if (!(time_status & STA_NANO))
710 txc->time.tv_usec /= NSEC_PER_USEC;
711
712 notify_cmos_timer();
713
714 return result;
715}
716
717#ifdef CONFIG_NTP_PPS
718
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) */
723struct pps_normtime {
724 __kernel_time_t sec; /* seconds */
725 long nsec; /* nanoseconds */
726};
727
728/* normalize the timestamp so that nsec is in the
729 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
730static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
731{
732 struct pps_normtime norm = {
733 .sec = ts.tv_sec,
734 .nsec = ts.tv_nsec
735 };
736
737 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
738 norm.nsec -= NSEC_PER_SEC;
739 norm.sec++;
740 }
741
742 return norm;
743}
744
745/* get current phase correction and jitter */
746static inline long pps_phase_filter_get(long *jitter)
747{
748 *jitter = pps_tf[0] - pps_tf[1];
749 if (*jitter < 0)
750 *jitter = -*jitter;
751
752 /* TODO: test various filters */
753 return pps_tf[0];
754}
755
756/* add the sample to the phase filter */
757static inline void pps_phase_filter_add(long err)
758{
759 pps_tf[2] = pps_tf[1];
760 pps_tf[1] = pps_tf[0];
761 pps_tf[0] = err;
762}
763
764/* decrease frequency calibration interval length.
765 * It is halved after four consecutive unstable intervals.
766 */
767static inline void pps_dec_freq_interval(void)
768{
769 if (--pps_intcnt <= -PPS_INTCOUNT) {
770 pps_intcnt = -PPS_INTCOUNT;
771 if (pps_shift > PPS_INTMIN) {
772 pps_shift--;
773 pps_intcnt = 0;
774 }
775 }
776}
777
778/* increase frequency calibration interval length.
779 * It is doubled after four consecutive stable intervals.
780 */
781static inline void pps_inc_freq_interval(void)
782{
783 if (++pps_intcnt >= PPS_INTCOUNT) {
784 pps_intcnt = PPS_INTCOUNT;
785 if (pps_shift < PPS_INTMAX) {
786 pps_shift++;
787 pps_intcnt = 0;
788 }
789 }
790}
791
792/* update clock frequency based on MONOTONIC_RAW clock PPS signal
793 * timestamps
794 *
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.
800 */
801static long hardpps_update_freq(struct pps_normtime freq_norm)
802{
803 long delta, delta_mod;
804 s64 ftemp;
805
806 /* check if the frequency interval was too long */
807 if (freq_norm.sec > (2 << pps_shift)) {
808 time_status |= STA_PPSERROR;
809 pps_errcnt++;
810 pps_dec_freq_interval();
811 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
812 freq_norm.sec);
813 return 0;
814 }
815
816 /* here the raw frequency offset and wander (stability) is
817 * calculated. If the wander is less than the wander threshold
818 * the interval is increased; otherwise it is decreased.
819 */
820 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
821 freq_norm.sec);
822 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
823 pps_freq = ftemp;
824 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
825 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
826 time_status |= STA_PPSWANDER;
827 pps_stbcnt++;
828 pps_dec_freq_interval();
829 } else { /* good sample */
830 pps_inc_freq_interval();
831 }
832
833 /* the stability metric is calculated as the average of recent
834 * frequency changes, but is used only for performance
835 * monitoring
836 */
837 delta_mod = delta;
838 if (delta_mod < 0)
839 delta_mod = -delta_mod;
840 pps_stabil += (div_s64(((s64)delta_mod) <<
841 (NTP_SCALE_SHIFT - SHIFT_USEC),
842 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
843
844 /* if enabled, the system clock frequency is updated */
845 if ((time_status & STA_PPSFREQ) != 0 &&
846 (time_status & STA_FREQHOLD) == 0) {
847 time_freq = pps_freq;
848 ntp_update_frequency();
849 }
850
851 return delta;
852}
853
854/* correct REALTIME clock phase error against PPS signal */
855static void hardpps_update_phase(long error)
856{
857 long correction = -error;
858 long jitter;
859
860 /* add the sample to the median filter */
861 pps_phase_filter_add(correction);
862 correction = pps_phase_filter_get(&jitter);
863
864 /* Nominal jitter is due to PPS signal noise. If it exceeds the
865 * threshold, the sample is discarded; otherwise, if so enabled,
866 * the time offset is updated.
867 */
868 if (jitter > (pps_jitter << PPS_POPCORN)) {
869 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
870 jitter, (pps_jitter << PPS_POPCORN));
871 time_status |= STA_PPSJITTER;
872 pps_jitcnt++;
873 } else if (time_status & STA_PPSTIME) {
874 /* correct the time using the phase offset */
875 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
876 NTP_INTERVAL_FREQ);
877 /* cancel running adjtime() */
878 time_adjust = 0;
879 }
880 /* update jitter */
881 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
882}
883
884/*
885 * hardpps() - discipline CPU clock oscillator to external PPS signal
886 *
887 * This routine is called at each PPS signal arrival in order to
888 * discipline the CPU clock oscillator to the PPS signal. It takes two
889 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
890 * is used to correct clock phase error and the latter is used to
891 * correct the frequency.
892 *
893 * This code is based on David Mills's reference nanokernel
894 * implementation. It was mostly rewritten but keeps the same idea.
895 */
896void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
897{
898 struct pps_normtime pts_norm, freq_norm;
899 unsigned long flags;
900
901 pts_norm = pps_normalize_ts(*phase_ts);
902
903 spin_lock_irqsave(&ntp_lock, flags);
904
905 /* clear the error bits, they will be set again if needed */
906 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
907
908 /* indicate signal presence */
909 time_status |= STA_PPSSIGNAL;
910 pps_valid = PPS_VALID;
911
912 /* when called for the first time,
913 * just start the frequency interval */
914 if (unlikely(pps_fbase.tv_sec == 0)) {
915 pps_fbase = *raw_ts;
916 spin_unlock_irqrestore(&ntp_lock, flags);
917 return;
918 }
919
920 /* ok, now we have a base for frequency calculation */
921 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
922
923 /* check that the signal is in the range
924 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
925 if ((freq_norm.sec == 0) ||
926 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
927 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
928 time_status |= STA_PPSJITTER;
929 /* restart the frequency calibration interval */
930 pps_fbase = *raw_ts;
931 spin_unlock_irqrestore(&ntp_lock, flags);
932 pr_err("hardpps: PPSJITTER: bad pulse\n");
933 return;
934 }
935
936 /* signal is ok */
937
938 /* check if the current frequency interval is finished */
939 if (freq_norm.sec >= (1 << pps_shift)) {
940 pps_calcnt++;
941 /* restart the frequency calibration interval */
942 pps_fbase = *raw_ts;
943 hardpps_update_freq(freq_norm);
944 }
945
946 hardpps_update_phase(pts_norm.nsec);
947
948 spin_unlock_irqrestore(&ntp_lock, flags);
949}
950EXPORT_SYMBOL(hardpps);
951
952#endif /* CONFIG_NTP_PPS */
953
954static int __init ntp_tick_adj_setup(char *str)
955{
956 ntp_tick_adj = simple_strtol(str, NULL, 0);
957 ntp_tick_adj <<= NTP_SCALE_SHIFT;
958
959 return 1;
960}
961
962__setup("ntp_tick_adj=", ntp_tick_adj_setup);
963
964void __init ntp_init(void)
965{
966 ntp_clear();
967}
1// SPDX-License-Identifier: GPL-2.0
2/*
3 * NTP state machine interfaces and logic.
4 *
5 * This code was mainly moved from kernel/timer.c and kernel/time.c
6 * Please see those files for relevant copyright info and historical
7 * changelogs.
8 */
9#include <linux/capability.h>
10#include <linux/clocksource.h>
11#include <linux/workqueue.h>
12#include <linux/hrtimer.h>
13#include <linux/jiffies.h>
14#include <linux/math64.h>
15#include <linux/timex.h>
16#include <linux/time.h>
17#include <linux/mm.h>
18#include <linux/module.h>
19#include <linux/rtc.h>
20#include <linux/math64.h>
21
22#include "ntp_internal.h"
23#include "timekeeping_internal.h"
24
25
26/*
27 * NTP timekeeping variables:
28 *
29 * Note: All of the NTP state is protected by the timekeeping locks.
30 */
31
32
33/* USER_HZ period (usecs): */
34unsigned long tick_usec = USER_TICK_USEC;
35
36/* SHIFTED_HZ period (nsecs): */
37unsigned long tick_nsec;
38
39static u64 tick_length;
40static u64 tick_length_base;
41
42#define SECS_PER_DAY 86400
43#define MAX_TICKADJ 500LL /* usecs */
44#define MAX_TICKADJ_SCALED \
45 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
46
47/*
48 * phase-lock loop variables
49 */
50
51/*
52 * clock synchronization status
53 *
54 * (TIME_ERROR prevents overwriting the CMOS clock)
55 */
56static int time_state = TIME_OK;
57
58/* clock status bits: */
59static int time_status = STA_UNSYNC;
60
61/* time adjustment (nsecs): */
62static s64 time_offset;
63
64/* pll time constant: */
65static long time_constant = 2;
66
67/* maximum error (usecs): */
68static long time_maxerror = NTP_PHASE_LIMIT;
69
70/* estimated error (usecs): */
71static long time_esterror = NTP_PHASE_LIMIT;
72
73/* frequency offset (scaled nsecs/secs): */
74static s64 time_freq;
75
76/* time at last adjustment (secs): */
77static time64_t time_reftime;
78
79static long time_adjust;
80
81/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
82static s64 ntp_tick_adj;
83
84/* second value of the next pending leapsecond, or TIME64_MAX if no leap */
85static time64_t ntp_next_leap_sec = TIME64_MAX;
86
87#ifdef CONFIG_NTP_PPS
88
89/*
90 * The following variables are used when a pulse-per-second (PPS) signal
91 * is available. They establish the engineering parameters of the clock
92 * discipline loop when controlled by the PPS signal.
93 */
94#define PPS_VALID 10 /* PPS signal watchdog max (s) */
95#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
96#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
97#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
98#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
99 increase pps_shift or consecutive bad
100 intervals to decrease it */
101#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
102
103static int pps_valid; /* signal watchdog counter */
104static long pps_tf[3]; /* phase median filter */
105static long pps_jitter; /* current jitter (ns) */
106static struct timespec64 pps_fbase; /* beginning of the last freq interval */
107static int pps_shift; /* current interval duration (s) (shift) */
108static int pps_intcnt; /* interval counter */
109static s64 pps_freq; /* frequency offset (scaled ns/s) */
110static long pps_stabil; /* current stability (scaled ns/s) */
111
112/*
113 * PPS signal quality monitors
114 */
115static long pps_calcnt; /* calibration intervals */
116static long pps_jitcnt; /* jitter limit exceeded */
117static long pps_stbcnt; /* stability limit exceeded */
118static long pps_errcnt; /* calibration errors */
119
120
121/* PPS kernel consumer compensates the whole phase error immediately.
122 * Otherwise, reduce the offset by a fixed factor times the time constant.
123 */
124static inline s64 ntp_offset_chunk(s64 offset)
125{
126 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
127 return offset;
128 else
129 return shift_right(offset, SHIFT_PLL + time_constant);
130}
131
132static inline void pps_reset_freq_interval(void)
133{
134 /* the PPS calibration interval may end
135 surprisingly early */
136 pps_shift = PPS_INTMIN;
137 pps_intcnt = 0;
138}
139
140/**
141 * pps_clear - Clears the PPS state variables
142 */
143static inline void pps_clear(void)
144{
145 pps_reset_freq_interval();
146 pps_tf[0] = 0;
147 pps_tf[1] = 0;
148 pps_tf[2] = 0;
149 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
150 pps_freq = 0;
151}
152
153/* Decrease pps_valid to indicate that another second has passed since
154 * the last PPS signal. When it reaches 0, indicate that PPS signal is
155 * missing.
156 */
157static inline void pps_dec_valid(void)
158{
159 if (pps_valid > 0)
160 pps_valid--;
161 else {
162 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
163 STA_PPSWANDER | STA_PPSERROR);
164 pps_clear();
165 }
166}
167
168static inline void pps_set_freq(s64 freq)
169{
170 pps_freq = freq;
171}
172
173static inline int is_error_status(int status)
174{
175 return (status & (STA_UNSYNC|STA_CLOCKERR))
176 /* PPS signal lost when either PPS time or
177 * PPS frequency synchronization requested
178 */
179 || ((status & (STA_PPSFREQ|STA_PPSTIME))
180 && !(status & STA_PPSSIGNAL))
181 /* PPS jitter exceeded when
182 * PPS time synchronization requested */
183 || ((status & (STA_PPSTIME|STA_PPSJITTER))
184 == (STA_PPSTIME|STA_PPSJITTER))
185 /* PPS wander exceeded or calibration error when
186 * PPS frequency synchronization requested
187 */
188 || ((status & STA_PPSFREQ)
189 && (status & (STA_PPSWANDER|STA_PPSERROR)));
190}
191
192static inline void pps_fill_timex(struct timex *txc)
193{
194 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
195 PPM_SCALE_INV, NTP_SCALE_SHIFT);
196 txc->jitter = pps_jitter;
197 if (!(time_status & STA_NANO))
198 txc->jitter /= NSEC_PER_USEC;
199 txc->shift = pps_shift;
200 txc->stabil = pps_stabil;
201 txc->jitcnt = pps_jitcnt;
202 txc->calcnt = pps_calcnt;
203 txc->errcnt = pps_errcnt;
204 txc->stbcnt = pps_stbcnt;
205}
206
207#else /* !CONFIG_NTP_PPS */
208
209static inline s64 ntp_offset_chunk(s64 offset)
210{
211 return shift_right(offset, SHIFT_PLL + time_constant);
212}
213
214static inline void pps_reset_freq_interval(void) {}
215static inline void pps_clear(void) {}
216static inline void pps_dec_valid(void) {}
217static inline void pps_set_freq(s64 freq) {}
218
219static inline int is_error_status(int status)
220{
221 return status & (STA_UNSYNC|STA_CLOCKERR);
222}
223
224static inline void pps_fill_timex(struct timex *txc)
225{
226 /* PPS is not implemented, so these are zero */
227 txc->ppsfreq = 0;
228 txc->jitter = 0;
229 txc->shift = 0;
230 txc->stabil = 0;
231 txc->jitcnt = 0;
232 txc->calcnt = 0;
233 txc->errcnt = 0;
234 txc->stbcnt = 0;
235}
236
237#endif /* CONFIG_NTP_PPS */
238
239
240/**
241 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
242 *
243 */
244static inline int ntp_synced(void)
245{
246 return !(time_status & STA_UNSYNC);
247}
248
249
250/*
251 * NTP methods:
252 */
253
254/*
255 * Update (tick_length, tick_length_base, tick_nsec), based
256 * on (tick_usec, ntp_tick_adj, time_freq):
257 */
258static void ntp_update_frequency(void)
259{
260 u64 second_length;
261 u64 new_base;
262
263 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
264 << NTP_SCALE_SHIFT;
265
266 second_length += ntp_tick_adj;
267 second_length += time_freq;
268
269 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
270 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
271
272 /*
273 * Don't wait for the next second_overflow, apply
274 * the change to the tick length immediately:
275 */
276 tick_length += new_base - tick_length_base;
277 tick_length_base = new_base;
278}
279
280static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
281{
282 time_status &= ~STA_MODE;
283
284 if (secs < MINSEC)
285 return 0;
286
287 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
288 return 0;
289
290 time_status |= STA_MODE;
291
292 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
293}
294
295static void ntp_update_offset(long offset)
296{
297 s64 freq_adj;
298 s64 offset64;
299 long secs;
300
301 if (!(time_status & STA_PLL))
302 return;
303
304 if (!(time_status & STA_NANO)) {
305 /* Make sure the multiplication below won't overflow */
306 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
307 offset *= NSEC_PER_USEC;
308 }
309
310 /*
311 * Scale the phase adjustment and
312 * clamp to the operating range.
313 */
314 offset = clamp(offset, -MAXPHASE, MAXPHASE);
315
316 /*
317 * Select how the frequency is to be controlled
318 * and in which mode (PLL or FLL).
319 */
320 secs = (long)(__ktime_get_real_seconds() - time_reftime);
321 if (unlikely(time_status & STA_FREQHOLD))
322 secs = 0;
323
324 time_reftime = __ktime_get_real_seconds();
325
326 offset64 = offset;
327 freq_adj = ntp_update_offset_fll(offset64, secs);
328
329 /*
330 * Clamp update interval to reduce PLL gain with low
331 * sampling rate (e.g. intermittent network connection)
332 * to avoid instability.
333 */
334 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
335 secs = 1 << (SHIFT_PLL + 1 + time_constant);
336
337 freq_adj += (offset64 * secs) <<
338 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
339
340 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
341
342 time_freq = max(freq_adj, -MAXFREQ_SCALED);
343
344 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
345}
346
347/**
348 * ntp_clear - Clears the NTP state variables
349 */
350void ntp_clear(void)
351{
352 time_adjust = 0; /* stop active adjtime() */
353 time_status |= STA_UNSYNC;
354 time_maxerror = NTP_PHASE_LIMIT;
355 time_esterror = NTP_PHASE_LIMIT;
356
357 ntp_update_frequency();
358
359 tick_length = tick_length_base;
360 time_offset = 0;
361
362 ntp_next_leap_sec = TIME64_MAX;
363 /* Clear PPS state variables */
364 pps_clear();
365}
366
367
368u64 ntp_tick_length(void)
369{
370 return tick_length;
371}
372
373/**
374 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
375 *
376 * Provides the time of the next leapsecond against CLOCK_REALTIME in
377 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
378 */
379ktime_t ntp_get_next_leap(void)
380{
381 ktime_t ret;
382
383 if ((time_state == TIME_INS) && (time_status & STA_INS))
384 return ktime_set(ntp_next_leap_sec, 0);
385 ret = KTIME_MAX;
386 return ret;
387}
388
389/*
390 * this routine handles the overflow of the microsecond field
391 *
392 * The tricky bits of code to handle the accurate clock support
393 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
394 * They were originally developed for SUN and DEC kernels.
395 * All the kudos should go to Dave for this stuff.
396 *
397 * Also handles leap second processing, and returns leap offset
398 */
399int second_overflow(time64_t secs)
400{
401 s64 delta;
402 int leap = 0;
403 s32 rem;
404
405 /*
406 * Leap second processing. If in leap-insert state at the end of the
407 * day, the system clock is set back one second; if in leap-delete
408 * state, the system clock is set ahead one second.
409 */
410 switch (time_state) {
411 case TIME_OK:
412 if (time_status & STA_INS) {
413 time_state = TIME_INS;
414 div_s64_rem(secs, SECS_PER_DAY, &rem);
415 ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
416 } else if (time_status & STA_DEL) {
417 time_state = TIME_DEL;
418 div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
419 ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
420 }
421 break;
422 case TIME_INS:
423 if (!(time_status & STA_INS)) {
424 ntp_next_leap_sec = TIME64_MAX;
425 time_state = TIME_OK;
426 } else if (secs == ntp_next_leap_sec) {
427 leap = -1;
428 time_state = TIME_OOP;
429 printk(KERN_NOTICE
430 "Clock: inserting leap second 23:59:60 UTC\n");
431 }
432 break;
433 case TIME_DEL:
434 if (!(time_status & STA_DEL)) {
435 ntp_next_leap_sec = TIME64_MAX;
436 time_state = TIME_OK;
437 } else if (secs == ntp_next_leap_sec) {
438 leap = 1;
439 ntp_next_leap_sec = TIME64_MAX;
440 time_state = TIME_WAIT;
441 printk(KERN_NOTICE
442 "Clock: deleting leap second 23:59:59 UTC\n");
443 }
444 break;
445 case TIME_OOP:
446 ntp_next_leap_sec = TIME64_MAX;
447 time_state = TIME_WAIT;
448 break;
449 case TIME_WAIT:
450 if (!(time_status & (STA_INS | STA_DEL)))
451 time_state = TIME_OK;
452 break;
453 }
454
455
456 /* Bump the maxerror field */
457 time_maxerror += MAXFREQ / NSEC_PER_USEC;
458 if (time_maxerror > NTP_PHASE_LIMIT) {
459 time_maxerror = NTP_PHASE_LIMIT;
460 time_status |= STA_UNSYNC;
461 }
462
463 /* Compute the phase adjustment for the next second */
464 tick_length = tick_length_base;
465
466 delta = ntp_offset_chunk(time_offset);
467 time_offset -= delta;
468 tick_length += delta;
469
470 /* Check PPS signal */
471 pps_dec_valid();
472
473 if (!time_adjust)
474 goto out;
475
476 if (time_adjust > MAX_TICKADJ) {
477 time_adjust -= MAX_TICKADJ;
478 tick_length += MAX_TICKADJ_SCALED;
479 goto out;
480 }
481
482 if (time_adjust < -MAX_TICKADJ) {
483 time_adjust += MAX_TICKADJ;
484 tick_length -= MAX_TICKADJ_SCALED;
485 goto out;
486 }
487
488 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
489 << NTP_SCALE_SHIFT;
490 time_adjust = 0;
491
492out:
493 return leap;
494}
495
496static void sync_hw_clock(struct work_struct *work);
497static DECLARE_DELAYED_WORK(sync_work, sync_hw_clock);
498
499static void sched_sync_hw_clock(struct timespec64 now,
500 unsigned long target_nsec, bool fail)
501
502{
503 struct timespec64 next;
504
505 getnstimeofday64(&next);
506 if (!fail)
507 next.tv_sec = 659;
508 else {
509 /*
510 * Try again as soon as possible. Delaying long periods
511 * decreases the accuracy of the work queue timer. Due to this
512 * the algorithm is very likely to require a short-sleep retry
513 * after the above long sleep to synchronize ts_nsec.
514 */
515 next.tv_sec = 0;
516 }
517
518 /* Compute the needed delay that will get to tv_nsec == target_nsec */
519 next.tv_nsec = target_nsec - next.tv_nsec;
520 if (next.tv_nsec <= 0)
521 next.tv_nsec += NSEC_PER_SEC;
522 if (next.tv_nsec >= NSEC_PER_SEC) {
523 next.tv_sec++;
524 next.tv_nsec -= NSEC_PER_SEC;
525 }
526
527 queue_delayed_work(system_power_efficient_wq, &sync_work,
528 timespec64_to_jiffies(&next));
529}
530
531static void sync_rtc_clock(void)
532{
533 unsigned long target_nsec;
534 struct timespec64 adjust, now;
535 int rc;
536
537 if (!IS_ENABLED(CONFIG_RTC_SYSTOHC))
538 return;
539
540 getnstimeofday64(&now);
541
542 adjust = now;
543 if (persistent_clock_is_local)
544 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
545
546 /*
547 * The current RTC in use will provide the target_nsec it wants to be
548 * called at, and does rtc_tv_nsec_ok internally.
549 */
550 rc = rtc_set_ntp_time(adjust, &target_nsec);
551 if (rc == -ENODEV)
552 return;
553
554 sched_sync_hw_clock(now, target_nsec, rc);
555}
556
557#ifdef CONFIG_GENERIC_CMOS_UPDATE
558int __weak update_persistent_clock(struct timespec now)
559{
560 return -ENODEV;
561}
562
563int __weak update_persistent_clock64(struct timespec64 now64)
564{
565 struct timespec now;
566
567 now = timespec64_to_timespec(now64);
568 return update_persistent_clock(now);
569}
570#endif
571
572static bool sync_cmos_clock(void)
573{
574 static bool no_cmos;
575 struct timespec64 now;
576 struct timespec64 adjust;
577 int rc = -EPROTO;
578 long target_nsec = NSEC_PER_SEC / 2;
579
580 if (!IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE))
581 return false;
582
583 if (no_cmos)
584 return false;
585
586 /*
587 * Historically update_persistent_clock64() has followed x86
588 * semantics, which match the MC146818A/etc RTC. This RTC will store
589 * 'adjust' and then in .5s it will advance once second.
590 *
591 * Architectures are strongly encouraged to use rtclib and not
592 * implement this legacy API.
593 */
594 getnstimeofday64(&now);
595 if (rtc_tv_nsec_ok(-1 * target_nsec, &adjust, &now)) {
596 if (persistent_clock_is_local)
597 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
598 rc = update_persistent_clock64(adjust);
599 /*
600 * The machine does not support update_persistent_clock64 even
601 * though it defines CONFIG_GENERIC_CMOS_UPDATE.
602 */
603 if (rc == -ENODEV) {
604 no_cmos = true;
605 return false;
606 }
607 }
608
609 sched_sync_hw_clock(now, target_nsec, rc);
610 return true;
611}
612
613/*
614 * If we have an externally synchronized Linux clock, then update RTC clock
615 * accordingly every ~11 minutes. Generally RTCs can only store second
616 * precision, but many RTCs will adjust the phase of their second tick to
617 * match the moment of update. This infrastructure arranges to call to the RTC
618 * set at the correct moment to phase synchronize the RTC second tick over
619 * with the kernel clock.
620 */
621static void sync_hw_clock(struct work_struct *work)
622{
623 if (!ntp_synced())
624 return;
625
626 if (sync_cmos_clock())
627 return;
628
629 sync_rtc_clock();
630}
631
632void ntp_notify_cmos_timer(void)
633{
634 if (!ntp_synced())
635 return;
636
637 if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) ||
638 IS_ENABLED(CONFIG_RTC_SYSTOHC))
639 queue_delayed_work(system_power_efficient_wq, &sync_work, 0);
640}
641
642/*
643 * Propagate a new txc->status value into the NTP state:
644 */
645static inline void process_adj_status(struct timex *txc, struct timespec64 *ts)
646{
647 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
648 time_state = TIME_OK;
649 time_status = STA_UNSYNC;
650 ntp_next_leap_sec = TIME64_MAX;
651 /* restart PPS frequency calibration */
652 pps_reset_freq_interval();
653 }
654
655 /*
656 * If we turn on PLL adjustments then reset the
657 * reference time to current time.
658 */
659 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
660 time_reftime = __ktime_get_real_seconds();
661
662 /* only set allowed bits */
663 time_status &= STA_RONLY;
664 time_status |= txc->status & ~STA_RONLY;
665}
666
667
668static inline void process_adjtimex_modes(struct timex *txc,
669 struct timespec64 *ts,
670 s32 *time_tai)
671{
672 if (txc->modes & ADJ_STATUS)
673 process_adj_status(txc, ts);
674
675 if (txc->modes & ADJ_NANO)
676 time_status |= STA_NANO;
677
678 if (txc->modes & ADJ_MICRO)
679 time_status &= ~STA_NANO;
680
681 if (txc->modes & ADJ_FREQUENCY) {
682 time_freq = txc->freq * PPM_SCALE;
683 time_freq = min(time_freq, MAXFREQ_SCALED);
684 time_freq = max(time_freq, -MAXFREQ_SCALED);
685 /* update pps_freq */
686 pps_set_freq(time_freq);
687 }
688
689 if (txc->modes & ADJ_MAXERROR)
690 time_maxerror = txc->maxerror;
691
692 if (txc->modes & ADJ_ESTERROR)
693 time_esterror = txc->esterror;
694
695 if (txc->modes & ADJ_TIMECONST) {
696 time_constant = txc->constant;
697 if (!(time_status & STA_NANO))
698 time_constant += 4;
699 time_constant = min(time_constant, (long)MAXTC);
700 time_constant = max(time_constant, 0l);
701 }
702
703 if (txc->modes & ADJ_TAI && txc->constant > 0)
704 *time_tai = txc->constant;
705
706 if (txc->modes & ADJ_OFFSET)
707 ntp_update_offset(txc->offset);
708
709 if (txc->modes & ADJ_TICK)
710 tick_usec = txc->tick;
711
712 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
713 ntp_update_frequency();
714}
715
716
717/*
718 * adjtimex mainly allows reading (and writing, if superuser) of
719 * kernel time-keeping variables. used by xntpd.
720 */
721int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai)
722{
723 int result;
724
725 if (txc->modes & ADJ_ADJTIME) {
726 long save_adjust = time_adjust;
727
728 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
729 /* adjtime() is independent from ntp_adjtime() */
730 time_adjust = txc->offset;
731 ntp_update_frequency();
732 }
733 txc->offset = save_adjust;
734 } else {
735
736 /* If there are input parameters, then process them: */
737 if (txc->modes)
738 process_adjtimex_modes(txc, ts, time_tai);
739
740 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
741 NTP_SCALE_SHIFT);
742 if (!(time_status & STA_NANO))
743 txc->offset /= NSEC_PER_USEC;
744 }
745
746 result = time_state; /* mostly `TIME_OK' */
747 /* check for errors */
748 if (is_error_status(time_status))
749 result = TIME_ERROR;
750
751 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
752 PPM_SCALE_INV, NTP_SCALE_SHIFT);
753 txc->maxerror = time_maxerror;
754 txc->esterror = time_esterror;
755 txc->status = time_status;
756 txc->constant = time_constant;
757 txc->precision = 1;
758 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
759 txc->tick = tick_usec;
760 txc->tai = *time_tai;
761
762 /* fill PPS status fields */
763 pps_fill_timex(txc);
764
765 txc->time.tv_sec = (time_t)ts->tv_sec;
766 txc->time.tv_usec = ts->tv_nsec;
767 if (!(time_status & STA_NANO))
768 txc->time.tv_usec /= NSEC_PER_USEC;
769
770 /* Handle leapsec adjustments */
771 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
772 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
773 result = TIME_OOP;
774 txc->tai++;
775 txc->time.tv_sec--;
776 }
777 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
778 result = TIME_WAIT;
779 txc->tai--;
780 txc->time.tv_sec++;
781 }
782 if ((time_state == TIME_OOP) &&
783 (ts->tv_sec == ntp_next_leap_sec)) {
784 result = TIME_WAIT;
785 }
786 }
787
788 return result;
789}
790
791#ifdef CONFIG_NTP_PPS
792
793/* actually struct pps_normtime is good old struct timespec, but it is
794 * semantically different (and it is the reason why it was invented):
795 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
796 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
797struct pps_normtime {
798 s64 sec; /* seconds */
799 long nsec; /* nanoseconds */
800};
801
802/* normalize the timestamp so that nsec is in the
803 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
804static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
805{
806 struct pps_normtime norm = {
807 .sec = ts.tv_sec,
808 .nsec = ts.tv_nsec
809 };
810
811 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
812 norm.nsec -= NSEC_PER_SEC;
813 norm.sec++;
814 }
815
816 return norm;
817}
818
819/* get current phase correction and jitter */
820static inline long pps_phase_filter_get(long *jitter)
821{
822 *jitter = pps_tf[0] - pps_tf[1];
823 if (*jitter < 0)
824 *jitter = -*jitter;
825
826 /* TODO: test various filters */
827 return pps_tf[0];
828}
829
830/* add the sample to the phase filter */
831static inline void pps_phase_filter_add(long err)
832{
833 pps_tf[2] = pps_tf[1];
834 pps_tf[1] = pps_tf[0];
835 pps_tf[0] = err;
836}
837
838/* decrease frequency calibration interval length.
839 * It is halved after four consecutive unstable intervals.
840 */
841static inline void pps_dec_freq_interval(void)
842{
843 if (--pps_intcnt <= -PPS_INTCOUNT) {
844 pps_intcnt = -PPS_INTCOUNT;
845 if (pps_shift > PPS_INTMIN) {
846 pps_shift--;
847 pps_intcnt = 0;
848 }
849 }
850}
851
852/* increase frequency calibration interval length.
853 * It is doubled after four consecutive stable intervals.
854 */
855static inline void pps_inc_freq_interval(void)
856{
857 if (++pps_intcnt >= PPS_INTCOUNT) {
858 pps_intcnt = PPS_INTCOUNT;
859 if (pps_shift < PPS_INTMAX) {
860 pps_shift++;
861 pps_intcnt = 0;
862 }
863 }
864}
865
866/* update clock frequency based on MONOTONIC_RAW clock PPS signal
867 * timestamps
868 *
869 * At the end of the calibration interval the difference between the
870 * first and last MONOTONIC_RAW clock timestamps divided by the length
871 * of the interval becomes the frequency update. If the interval was
872 * too long, the data are discarded.
873 * Returns the difference between old and new frequency values.
874 */
875static long hardpps_update_freq(struct pps_normtime freq_norm)
876{
877 long delta, delta_mod;
878 s64 ftemp;
879
880 /* check if the frequency interval was too long */
881 if (freq_norm.sec > (2 << pps_shift)) {
882 time_status |= STA_PPSERROR;
883 pps_errcnt++;
884 pps_dec_freq_interval();
885 printk_deferred(KERN_ERR
886 "hardpps: PPSERROR: interval too long - %lld s\n",
887 freq_norm.sec);
888 return 0;
889 }
890
891 /* here the raw frequency offset and wander (stability) is
892 * calculated. If the wander is less than the wander threshold
893 * the interval is increased; otherwise it is decreased.
894 */
895 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
896 freq_norm.sec);
897 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
898 pps_freq = ftemp;
899 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
900 printk_deferred(KERN_WARNING
901 "hardpps: PPSWANDER: change=%ld\n", delta);
902 time_status |= STA_PPSWANDER;
903 pps_stbcnt++;
904 pps_dec_freq_interval();
905 } else { /* good sample */
906 pps_inc_freq_interval();
907 }
908
909 /* the stability metric is calculated as the average of recent
910 * frequency changes, but is used only for performance
911 * monitoring
912 */
913 delta_mod = delta;
914 if (delta_mod < 0)
915 delta_mod = -delta_mod;
916 pps_stabil += (div_s64(((s64)delta_mod) <<
917 (NTP_SCALE_SHIFT - SHIFT_USEC),
918 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
919
920 /* if enabled, the system clock frequency is updated */
921 if ((time_status & STA_PPSFREQ) != 0 &&
922 (time_status & STA_FREQHOLD) == 0) {
923 time_freq = pps_freq;
924 ntp_update_frequency();
925 }
926
927 return delta;
928}
929
930/* correct REALTIME clock phase error against PPS signal */
931static void hardpps_update_phase(long error)
932{
933 long correction = -error;
934 long jitter;
935
936 /* add the sample to the median filter */
937 pps_phase_filter_add(correction);
938 correction = pps_phase_filter_get(&jitter);
939
940 /* Nominal jitter is due to PPS signal noise. If it exceeds the
941 * threshold, the sample is discarded; otherwise, if so enabled,
942 * the time offset is updated.
943 */
944 if (jitter > (pps_jitter << PPS_POPCORN)) {
945 printk_deferred(KERN_WARNING
946 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
947 jitter, (pps_jitter << PPS_POPCORN));
948 time_status |= STA_PPSJITTER;
949 pps_jitcnt++;
950 } else if (time_status & STA_PPSTIME) {
951 /* correct the time using the phase offset */
952 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
953 NTP_INTERVAL_FREQ);
954 /* cancel running adjtime() */
955 time_adjust = 0;
956 }
957 /* update jitter */
958 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
959}
960
961/*
962 * __hardpps() - discipline CPU clock oscillator to external PPS signal
963 *
964 * This routine is called at each PPS signal arrival in order to
965 * discipline the CPU clock oscillator to the PPS signal. It takes two
966 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
967 * is used to correct clock phase error and the latter is used to
968 * correct the frequency.
969 *
970 * This code is based on David Mills's reference nanokernel
971 * implementation. It was mostly rewritten but keeps the same idea.
972 */
973void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
974{
975 struct pps_normtime pts_norm, freq_norm;
976
977 pts_norm = pps_normalize_ts(*phase_ts);
978
979 /* clear the error bits, they will be set again if needed */
980 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
981
982 /* indicate signal presence */
983 time_status |= STA_PPSSIGNAL;
984 pps_valid = PPS_VALID;
985
986 /* when called for the first time,
987 * just start the frequency interval */
988 if (unlikely(pps_fbase.tv_sec == 0)) {
989 pps_fbase = *raw_ts;
990 return;
991 }
992
993 /* ok, now we have a base for frequency calculation */
994 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
995
996 /* check that the signal is in the range
997 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
998 if ((freq_norm.sec == 0) ||
999 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1000 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1001 time_status |= STA_PPSJITTER;
1002 /* restart the frequency calibration interval */
1003 pps_fbase = *raw_ts;
1004 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1005 return;
1006 }
1007
1008 /* signal is ok */
1009
1010 /* check if the current frequency interval is finished */
1011 if (freq_norm.sec >= (1 << pps_shift)) {
1012 pps_calcnt++;
1013 /* restart the frequency calibration interval */
1014 pps_fbase = *raw_ts;
1015 hardpps_update_freq(freq_norm);
1016 }
1017
1018 hardpps_update_phase(pts_norm.nsec);
1019
1020}
1021#endif /* CONFIG_NTP_PPS */
1022
1023static int __init ntp_tick_adj_setup(char *str)
1024{
1025 int rc = kstrtol(str, 0, (long *)&ntp_tick_adj);
1026
1027 if (rc)
1028 return rc;
1029 ntp_tick_adj <<= NTP_SCALE_SHIFT;
1030
1031 return 1;
1032}
1033
1034__setup("ntp_tick_adj=", ntp_tick_adj_setup);
1035
1036void __init ntp_init(void)
1037{
1038 ntp_clear();
1039}