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): */
34 unsigned long tick_usec = USER_TICK_USEC;
35
36 /* SHIFTED_HZ period (nsecs): */
37 unsigned long tick_nsec;
38
39 static u64 tick_length;
40 static 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 */
56 static int time_state = TIME_OK;
57
58 /* clock status bits: */
59 static int time_status = STA_UNSYNC;
60
61 /* time adjustment (nsecs): */
62 static s64 time_offset;
63
64 /* pll time constant: */
65 static long time_constant = 2;
66
67 /* maximum error (usecs): */
68 static long time_maxerror = NTP_PHASE_LIMIT;
69
70 /* estimated error (usecs): */
71 static long time_esterror = NTP_PHASE_LIMIT;
72
73 /* frequency offset (scaled nsecs/secs): */
74 static s64 time_freq;
75
76 /* time at last adjustment (secs): */
77 static time64_t time_reftime;
78
79 static long time_adjust;
80
81 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
82 static s64 ntp_tick_adj;
83
84 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */
85 static 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
103 static int pps_valid; /* signal watchdog counter */
104 static long pps_tf[3]; /* phase median filter */
105 static long pps_jitter; /* current jitter (ns) */
106 static struct timespec64 pps_fbase; /* beginning of the last freq interval */
107 static int pps_shift; /* current interval duration (s) (shift) */
108 static int pps_intcnt; /* interval counter */
109 static s64 pps_freq; /* frequency offset (scaled ns/s) */
110 static long pps_stabil; /* current stability (scaled ns/s) */
111
112 /*
113 * PPS signal quality monitors
114 */
115 static long pps_calcnt; /* calibration intervals */
116 static long pps_jitcnt; /* jitter limit exceeded */
117 static long pps_stbcnt; /* stability limit exceeded */
118 static 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 */
ntp_offset_chunk(s64 offset)124 static 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
pps_reset_freq_interval(void)132 static 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 */
pps_clear(void)143 static 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 */
pps_dec_valid(void)157 static 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
pps_set_freq(s64 freq)168 static inline void pps_set_freq(s64 freq)
169 {
170 pps_freq = freq;
171 }
172
is_error_status(int status)173 static 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
pps_fill_timex(struct timex * txc)192 static 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
ntp_offset_chunk(s64 offset)209 static inline s64 ntp_offset_chunk(s64 offset)
210 {
211 return shift_right(offset, SHIFT_PLL + time_constant);
212 }
213
pps_reset_freq_interval(void)214 static inline void pps_reset_freq_interval(void) {}
pps_clear(void)215 static inline void pps_clear(void) {}
pps_dec_valid(void)216 static inline void pps_dec_valid(void) {}
pps_set_freq(s64 freq)217 static inline void pps_set_freq(s64 freq) {}
218
is_error_status(int status)219 static inline int is_error_status(int status)
220 {
221 return status & (STA_UNSYNC|STA_CLOCKERR);
222 }
223
pps_fill_timex(struct timex * txc)224 static 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 */
ntp_synced(void)244 static 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 */
ntp_update_frequency(void)258 static 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
ntp_update_offset_fll(s64 offset64,long secs)280 static 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
ntp_update_offset(long offset)295 static 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 */
ntp_clear(void)350 void 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
ntp_tick_length(void)368 u64 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 */
ntp_get_next_leap(void)379 ktime_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 */
second_overflow(time64_t secs)399 int 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
492 out:
493 return leap;
494 }
495
496 static void sync_hw_clock(struct work_struct *work);
497 static DECLARE_DELAYED_WORK(sync_work, sync_hw_clock);
498
sched_sync_hw_clock(struct timespec64 now,unsigned long target_nsec,bool fail)499 static void sched_sync_hw_clock(struct timespec64 now,
500 unsigned long target_nsec, bool fail)
501
502 {
503 struct timespec64 next;
504
505 ktime_get_real_ts64(&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
sync_rtc_clock(void)531 static 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 ktime_get_real_ts64(&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
update_persistent_clock(struct timespec now)558 int __weak update_persistent_clock(struct timespec now)
559 {
560 return -ENODEV;
561 }
562
update_persistent_clock64(struct timespec64 now64)563 int __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
sync_cmos_clock(void)572 static 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 ktime_get_real_ts64(&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 */
sync_hw_clock(struct work_struct * work)621 static 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
ntp_notify_cmos_timer(void)632 void 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 */
process_adj_status(const struct timex * txc)645 static inline void process_adj_status(const struct timex *txc)
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
process_adjtimex_modes(const struct timex * txc,s32 * time_tai)668 static inline void process_adjtimex_modes(const struct timex *txc, s32 *time_tai)
669 {
670 if (txc->modes & ADJ_STATUS)
671 process_adj_status(txc);
672
673 if (txc->modes & ADJ_NANO)
674 time_status |= STA_NANO;
675
676 if (txc->modes & ADJ_MICRO)
677 time_status &= ~STA_NANO;
678
679 if (txc->modes & ADJ_FREQUENCY) {
680 time_freq = txc->freq * PPM_SCALE;
681 time_freq = min(time_freq, MAXFREQ_SCALED);
682 time_freq = max(time_freq, -MAXFREQ_SCALED);
683 /* update pps_freq */
684 pps_set_freq(time_freq);
685 }
686
687 if (txc->modes & ADJ_MAXERROR)
688 time_maxerror = txc->maxerror;
689
690 if (txc->modes & ADJ_ESTERROR)
691 time_esterror = txc->esterror;
692
693 if (txc->modes & ADJ_TIMECONST) {
694 time_constant = txc->constant;
695 if (!(time_status & STA_NANO))
696 time_constant += 4;
697 time_constant = min(time_constant, (long)MAXTC);
698 time_constant = max(time_constant, 0l);
699 }
700
701 if (txc->modes & ADJ_TAI && txc->constant > 0)
702 *time_tai = txc->constant;
703
704 if (txc->modes & ADJ_OFFSET)
705 ntp_update_offset(txc->offset);
706
707 if (txc->modes & ADJ_TICK)
708 tick_usec = txc->tick;
709
710 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
711 ntp_update_frequency();
712 }
713
714
715 /*
716 * adjtimex mainly allows reading (and writing, if superuser) of
717 * kernel time-keeping variables. used by xntpd.
718 */
__do_adjtimex(struct timex * txc,const struct timespec64 * ts,s32 * time_tai)719 int __do_adjtimex(struct timex *txc, const struct timespec64 *ts, s32 *time_tai)
720 {
721 int result;
722
723 if (txc->modes & ADJ_ADJTIME) {
724 long save_adjust = time_adjust;
725
726 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
727 /* adjtime() is independent from ntp_adjtime() */
728 time_adjust = txc->offset;
729 ntp_update_frequency();
730 }
731 txc->offset = save_adjust;
732 } else {
733
734 /* If there are input parameters, then process them: */
735 if (txc->modes)
736 process_adjtimex_modes(txc, time_tai);
737
738 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
739 NTP_SCALE_SHIFT);
740 if (!(time_status & STA_NANO))
741 txc->offset /= NSEC_PER_USEC;
742 }
743
744 result = time_state; /* mostly `TIME_OK' */
745 /* check for errors */
746 if (is_error_status(time_status))
747 result = TIME_ERROR;
748
749 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
750 PPM_SCALE_INV, NTP_SCALE_SHIFT);
751 txc->maxerror = time_maxerror;
752 txc->esterror = time_esterror;
753 txc->status = time_status;
754 txc->constant = time_constant;
755 txc->precision = 1;
756 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
757 txc->tick = tick_usec;
758 txc->tai = *time_tai;
759
760 /* fill PPS status fields */
761 pps_fill_timex(txc);
762
763 txc->time.tv_sec = (time_t)ts->tv_sec;
764 txc->time.tv_usec = ts->tv_nsec;
765 if (!(time_status & STA_NANO))
766 txc->time.tv_usec /= NSEC_PER_USEC;
767
768 /* Handle leapsec adjustments */
769 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
770 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
771 result = TIME_OOP;
772 txc->tai++;
773 txc->time.tv_sec--;
774 }
775 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
776 result = TIME_WAIT;
777 txc->tai--;
778 txc->time.tv_sec++;
779 }
780 if ((time_state == TIME_OOP) &&
781 (ts->tv_sec == ntp_next_leap_sec)) {
782 result = TIME_WAIT;
783 }
784 }
785
786 return result;
787 }
788
789 #ifdef CONFIG_NTP_PPS
790
791 /* actually struct pps_normtime is good old struct timespec, but it is
792 * semantically different (and it is the reason why it was invented):
793 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
794 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
795 struct pps_normtime {
796 s64 sec; /* seconds */
797 long nsec; /* nanoseconds */
798 };
799
800 /* normalize the timestamp so that nsec is in the
801 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
pps_normalize_ts(struct timespec64 ts)802 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
803 {
804 struct pps_normtime norm = {
805 .sec = ts.tv_sec,
806 .nsec = ts.tv_nsec
807 };
808
809 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
810 norm.nsec -= NSEC_PER_SEC;
811 norm.sec++;
812 }
813
814 return norm;
815 }
816
817 /* get current phase correction and jitter */
pps_phase_filter_get(long * jitter)818 static inline long pps_phase_filter_get(long *jitter)
819 {
820 *jitter = pps_tf[0] - pps_tf[1];
821 if (*jitter < 0)
822 *jitter = -*jitter;
823
824 /* TODO: test various filters */
825 return pps_tf[0];
826 }
827
828 /* add the sample to the phase filter */
pps_phase_filter_add(long err)829 static inline void pps_phase_filter_add(long err)
830 {
831 pps_tf[2] = pps_tf[1];
832 pps_tf[1] = pps_tf[0];
833 pps_tf[0] = err;
834 }
835
836 /* decrease frequency calibration interval length.
837 * It is halved after four consecutive unstable intervals.
838 */
pps_dec_freq_interval(void)839 static inline void pps_dec_freq_interval(void)
840 {
841 if (--pps_intcnt <= -PPS_INTCOUNT) {
842 pps_intcnt = -PPS_INTCOUNT;
843 if (pps_shift > PPS_INTMIN) {
844 pps_shift--;
845 pps_intcnt = 0;
846 }
847 }
848 }
849
850 /* increase frequency calibration interval length.
851 * It is doubled after four consecutive stable intervals.
852 */
pps_inc_freq_interval(void)853 static inline void pps_inc_freq_interval(void)
854 {
855 if (++pps_intcnt >= PPS_INTCOUNT) {
856 pps_intcnt = PPS_INTCOUNT;
857 if (pps_shift < PPS_INTMAX) {
858 pps_shift++;
859 pps_intcnt = 0;
860 }
861 }
862 }
863
864 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
865 * timestamps
866 *
867 * At the end of the calibration interval the difference between the
868 * first and last MONOTONIC_RAW clock timestamps divided by the length
869 * of the interval becomes the frequency update. If the interval was
870 * too long, the data are discarded.
871 * Returns the difference between old and new frequency values.
872 */
hardpps_update_freq(struct pps_normtime freq_norm)873 static long hardpps_update_freq(struct pps_normtime freq_norm)
874 {
875 long delta, delta_mod;
876 s64 ftemp;
877
878 /* check if the frequency interval was too long */
879 if (freq_norm.sec > (2 << pps_shift)) {
880 time_status |= STA_PPSERROR;
881 pps_errcnt++;
882 pps_dec_freq_interval();
883 printk_deferred(KERN_ERR
884 "hardpps: PPSERROR: interval too long - %lld s\n",
885 freq_norm.sec);
886 return 0;
887 }
888
889 /* here the raw frequency offset and wander (stability) is
890 * calculated. If the wander is less than the wander threshold
891 * the interval is increased; otherwise it is decreased.
892 */
893 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
894 freq_norm.sec);
895 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
896 pps_freq = ftemp;
897 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
898 printk_deferred(KERN_WARNING
899 "hardpps: PPSWANDER: change=%ld\n", delta);
900 time_status |= STA_PPSWANDER;
901 pps_stbcnt++;
902 pps_dec_freq_interval();
903 } else { /* good sample */
904 pps_inc_freq_interval();
905 }
906
907 /* the stability metric is calculated as the average of recent
908 * frequency changes, but is used only for performance
909 * monitoring
910 */
911 delta_mod = delta;
912 if (delta_mod < 0)
913 delta_mod = -delta_mod;
914 pps_stabil += (div_s64(((s64)delta_mod) <<
915 (NTP_SCALE_SHIFT - SHIFT_USEC),
916 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
917
918 /* if enabled, the system clock frequency is updated */
919 if ((time_status & STA_PPSFREQ) != 0 &&
920 (time_status & STA_FREQHOLD) == 0) {
921 time_freq = pps_freq;
922 ntp_update_frequency();
923 }
924
925 return delta;
926 }
927
928 /* correct REALTIME clock phase error against PPS signal */
hardpps_update_phase(long error)929 static void hardpps_update_phase(long error)
930 {
931 long correction = -error;
932 long jitter;
933
934 /* add the sample to the median filter */
935 pps_phase_filter_add(correction);
936 correction = pps_phase_filter_get(&jitter);
937
938 /* Nominal jitter is due to PPS signal noise. If it exceeds the
939 * threshold, the sample is discarded; otherwise, if so enabled,
940 * the time offset is updated.
941 */
942 if (jitter > (pps_jitter << PPS_POPCORN)) {
943 printk_deferred(KERN_WARNING
944 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
945 jitter, (pps_jitter << PPS_POPCORN));
946 time_status |= STA_PPSJITTER;
947 pps_jitcnt++;
948 } else if (time_status & STA_PPSTIME) {
949 /* correct the time using the phase offset */
950 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
951 NTP_INTERVAL_FREQ);
952 /* cancel running adjtime() */
953 time_adjust = 0;
954 }
955 /* update jitter */
956 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
957 }
958
959 /*
960 * __hardpps() - discipline CPU clock oscillator to external PPS signal
961 *
962 * This routine is called at each PPS signal arrival in order to
963 * discipline the CPU clock oscillator to the PPS signal. It takes two
964 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
965 * is used to correct clock phase error and the latter is used to
966 * correct the frequency.
967 *
968 * This code is based on David Mills's reference nanokernel
969 * implementation. It was mostly rewritten but keeps the same idea.
970 */
__hardpps(const struct timespec64 * phase_ts,const struct timespec64 * raw_ts)971 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
972 {
973 struct pps_normtime pts_norm, freq_norm;
974
975 pts_norm = pps_normalize_ts(*phase_ts);
976
977 /* clear the error bits, they will be set again if needed */
978 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
979
980 /* indicate signal presence */
981 time_status |= STA_PPSSIGNAL;
982 pps_valid = PPS_VALID;
983
984 /* when called for the first time,
985 * just start the frequency interval */
986 if (unlikely(pps_fbase.tv_sec == 0)) {
987 pps_fbase = *raw_ts;
988 return;
989 }
990
991 /* ok, now we have a base for frequency calculation */
992 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
993
994 /* check that the signal is in the range
995 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
996 if ((freq_norm.sec == 0) ||
997 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
998 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
999 time_status |= STA_PPSJITTER;
1000 /* restart the frequency calibration interval */
1001 pps_fbase = *raw_ts;
1002 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1003 return;
1004 }
1005
1006 /* signal is ok */
1007
1008 /* check if the current frequency interval is finished */
1009 if (freq_norm.sec >= (1 << pps_shift)) {
1010 pps_calcnt++;
1011 /* restart the frequency calibration interval */
1012 pps_fbase = *raw_ts;
1013 hardpps_update_freq(freq_norm);
1014 }
1015
1016 hardpps_update_phase(pts_norm.nsec);
1017
1018 }
1019 #endif /* CONFIG_NTP_PPS */
1020
ntp_tick_adj_setup(char * str)1021 static int __init ntp_tick_adj_setup(char *str)
1022 {
1023 int rc = kstrtos64(str, 0, &ntp_tick_adj);
1024 if (rc)
1025 return rc;
1026
1027 ntp_tick_adj <<= NTP_SCALE_SHIFT;
1028 return 1;
1029 }
1030
1031 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1032
ntp_init(void)1033 void __init ntp_init(void)
1034 {
1035 ntp_clear();
1036 }
1037
