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/audit.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 #define MAX_TAI_OFFSET 100000
47
48 /*
49 * phase-lock loop variables
50 */
51
52 /*
53 * clock synchronization status
54 *
55 * (TIME_ERROR prevents overwriting the CMOS clock)
56 */
57 static int time_state = TIME_OK;
58
59 /* clock status bits: */
60 static int time_status = STA_UNSYNC;
61
62 /* time adjustment (nsecs): */
63 static s64 time_offset;
64
65 /* pll time constant: */
66 static long time_constant = 2;
67
68 /* maximum error (usecs): */
69 static long time_maxerror = NTP_PHASE_LIMIT;
70
71 /* estimated error (usecs): */
72 static long time_esterror = NTP_PHASE_LIMIT;
73
74 /* frequency offset (scaled nsecs/secs): */
75 static s64 time_freq;
76
77 /* time at last adjustment (secs): */
78 static time64_t time_reftime;
79
80 static long time_adjust;
81
82 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
83 static s64 ntp_tick_adj;
84
85 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */
86 static time64_t ntp_next_leap_sec = TIME64_MAX;
87
88 #ifdef CONFIG_NTP_PPS
89
90 /*
91 * The following variables are used when a pulse-per-second (PPS) signal
92 * is available. They establish the engineering parameters of the clock
93 * discipline loop when controlled by the PPS signal.
94 */
95 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
96 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
97 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
98 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
99 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
100 increase pps_shift or consecutive bad
101 intervals to decrease it */
102 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
103
104 static int pps_valid; /* signal watchdog counter */
105 static long pps_tf[3]; /* phase median filter */
106 static long pps_jitter; /* current jitter (ns) */
107 static struct timespec64 pps_fbase; /* beginning of the last freq interval */
108 static int pps_shift; /* current interval duration (s) (shift) */
109 static int pps_intcnt; /* interval counter */
110 static s64 pps_freq; /* frequency offset (scaled ns/s) */
111 static long pps_stabil; /* current stability (scaled ns/s) */
112
113 /*
114 * PPS signal quality monitors
115 */
116 static long pps_calcnt; /* calibration intervals */
117 static long pps_jitcnt; /* jitter limit exceeded */
118 static long pps_stbcnt; /* stability limit exceeded */
119 static long pps_errcnt; /* calibration errors */
120
121
122 /* PPS kernel consumer compensates the whole phase error immediately.
123 * Otherwise, reduce the offset by a fixed factor times the time constant.
124 */
ntp_offset_chunk(s64 offset)125 static inline s64 ntp_offset_chunk(s64 offset)
126 {
127 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
128 return offset;
129 else
130 return shift_right(offset, SHIFT_PLL + time_constant);
131 }
132
pps_reset_freq_interval(void)133 static inline void pps_reset_freq_interval(void)
134 {
135 /* the PPS calibration interval may end
136 surprisingly early */
137 pps_shift = PPS_INTMIN;
138 pps_intcnt = 0;
139 }
140
141 /**
142 * pps_clear - Clears the PPS state variables
143 */
pps_clear(void)144 static inline void pps_clear(void)
145 {
146 pps_reset_freq_interval();
147 pps_tf[0] = 0;
148 pps_tf[1] = 0;
149 pps_tf[2] = 0;
150 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
151 pps_freq = 0;
152 }
153
154 /* Decrease pps_valid to indicate that another second has passed since
155 * the last PPS signal. When it reaches 0, indicate that PPS signal is
156 * missing.
157 */
pps_dec_valid(void)158 static inline void pps_dec_valid(void)
159 {
160 if (pps_valid > 0)
161 pps_valid--;
162 else {
163 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
164 STA_PPSWANDER | STA_PPSERROR);
165 pps_clear();
166 }
167 }
168
pps_set_freq(s64 freq)169 static inline void pps_set_freq(s64 freq)
170 {
171 pps_freq = freq;
172 }
173
is_error_status(int status)174 static inline int is_error_status(int status)
175 {
176 return (status & (STA_UNSYNC|STA_CLOCKERR))
177 /* PPS signal lost when either PPS time or
178 * PPS frequency synchronization requested
179 */
180 || ((status & (STA_PPSFREQ|STA_PPSTIME))
181 && !(status & STA_PPSSIGNAL))
182 /* PPS jitter exceeded when
183 * PPS time synchronization requested */
184 || ((status & (STA_PPSTIME|STA_PPSJITTER))
185 == (STA_PPSTIME|STA_PPSJITTER))
186 /* PPS wander exceeded or calibration error when
187 * PPS frequency synchronization requested
188 */
189 || ((status & STA_PPSFREQ)
190 && (status & (STA_PPSWANDER|STA_PPSERROR)));
191 }
192
pps_fill_timex(struct __kernel_timex * txc)193 static inline void pps_fill_timex(struct __kernel_timex *txc)
194 {
195 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
196 PPM_SCALE_INV, NTP_SCALE_SHIFT);
197 txc->jitter = pps_jitter;
198 if (!(time_status & STA_NANO))
199 txc->jitter = pps_jitter / NSEC_PER_USEC;
200 txc->shift = pps_shift;
201 txc->stabil = pps_stabil;
202 txc->jitcnt = pps_jitcnt;
203 txc->calcnt = pps_calcnt;
204 txc->errcnt = pps_errcnt;
205 txc->stbcnt = pps_stbcnt;
206 }
207
208 #else /* !CONFIG_NTP_PPS */
209
ntp_offset_chunk(s64 offset)210 static inline s64 ntp_offset_chunk(s64 offset)
211 {
212 return shift_right(offset, SHIFT_PLL + time_constant);
213 }
214
pps_reset_freq_interval(void)215 static inline void pps_reset_freq_interval(void) {}
pps_clear(void)216 static inline void pps_clear(void) {}
pps_dec_valid(void)217 static inline void pps_dec_valid(void) {}
pps_set_freq(s64 freq)218 static inline void pps_set_freq(s64 freq) {}
219
is_error_status(int status)220 static inline int is_error_status(int status)
221 {
222 return status & (STA_UNSYNC|STA_CLOCKERR);
223 }
224
pps_fill_timex(struct __kernel_timex * txc)225 static inline void pps_fill_timex(struct __kernel_timex *txc)
226 {
227 /* PPS is not implemented, so these are zero */
228 txc->ppsfreq = 0;
229 txc->jitter = 0;
230 txc->shift = 0;
231 txc->stabil = 0;
232 txc->jitcnt = 0;
233 txc->calcnt = 0;
234 txc->errcnt = 0;
235 txc->stbcnt = 0;
236 }
237
238 #endif /* CONFIG_NTP_PPS */
239
240
241 /**
242 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
243 *
244 */
ntp_synced(void)245 static inline int ntp_synced(void)
246 {
247 return !(time_status & STA_UNSYNC);
248 }
249
250
251 /*
252 * NTP methods:
253 */
254
255 /*
256 * Update (tick_length, tick_length_base, tick_nsec), based
257 * on (tick_usec, ntp_tick_adj, time_freq):
258 */
ntp_update_frequency(void)259 static void ntp_update_frequency(void)
260 {
261 u64 second_length;
262 u64 new_base;
263
264 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
265 << NTP_SCALE_SHIFT;
266
267 second_length += ntp_tick_adj;
268 second_length += time_freq;
269
270 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
271 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
272
273 /*
274 * Don't wait for the next second_overflow, apply
275 * the change to the tick length immediately:
276 */
277 tick_length += new_base - tick_length_base;
278 tick_length_base = new_base;
279 }
280
ntp_update_offset_fll(s64 offset64,long secs)281 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
282 {
283 time_status &= ~STA_MODE;
284
285 if (secs < MINSEC)
286 return 0;
287
288 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
289 return 0;
290
291 time_status |= STA_MODE;
292
293 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
294 }
295
ntp_update_offset(long offset)296 static void ntp_update_offset(long offset)
297 {
298 s64 freq_adj;
299 s64 offset64;
300 long secs;
301
302 if (!(time_status & STA_PLL))
303 return;
304
305 if (!(time_status & STA_NANO)) {
306 /* Make sure the multiplication below won't overflow */
307 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
308 offset *= NSEC_PER_USEC;
309 }
310
311 /*
312 * Scale the phase adjustment and
313 * clamp to the operating range.
314 */
315 offset = clamp(offset, -MAXPHASE, MAXPHASE);
316
317 /*
318 * Select how the frequency is to be controlled
319 * and in which mode (PLL or FLL).
320 */
321 secs = (long)(__ktime_get_real_seconds() - time_reftime);
322 if (unlikely(time_status & STA_FREQHOLD))
323 secs = 0;
324
325 time_reftime = __ktime_get_real_seconds();
326
327 offset64 = offset;
328 freq_adj = ntp_update_offset_fll(offset64, secs);
329
330 /*
331 * Clamp update interval to reduce PLL gain with low
332 * sampling rate (e.g. intermittent network connection)
333 * to avoid instability.
334 */
335 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
336 secs = 1 << (SHIFT_PLL + 1 + time_constant);
337
338 freq_adj += (offset64 * secs) <<
339 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
340
341 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
342
343 time_freq = max(freq_adj, -MAXFREQ_SCALED);
344
345 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
346 }
347
348 /**
349 * ntp_clear - Clears the NTP state variables
350 */
ntp_clear(void)351 void ntp_clear(void)
352 {
353 time_adjust = 0; /* stop active adjtime() */
354 time_status |= STA_UNSYNC;
355 time_maxerror = NTP_PHASE_LIMIT;
356 time_esterror = NTP_PHASE_LIMIT;
357
358 ntp_update_frequency();
359
360 tick_length = tick_length_base;
361 time_offset = 0;
362
363 ntp_next_leap_sec = TIME64_MAX;
364 /* Clear PPS state variables */
365 pps_clear();
366 }
367
368
ntp_tick_length(void)369 u64 ntp_tick_length(void)
370 {
371 return tick_length;
372 }
373
374 /**
375 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
376 *
377 * Provides the time of the next leapsecond against CLOCK_REALTIME in
378 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
379 */
ntp_get_next_leap(void)380 ktime_t ntp_get_next_leap(void)
381 {
382 ktime_t ret;
383
384 if ((time_state == TIME_INS) && (time_status & STA_INS))
385 return ktime_set(ntp_next_leap_sec, 0);
386 ret = KTIME_MAX;
387 return ret;
388 }
389
390 /*
391 * this routine handles the overflow of the microsecond field
392 *
393 * The tricky bits of code to handle the accurate clock support
394 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
395 * They were originally developed for SUN and DEC kernels.
396 * All the kudos should go to Dave for this stuff.
397 *
398 * Also handles leap second processing, and returns leap offset
399 */
second_overflow(time64_t secs)400 int second_overflow(time64_t secs)
401 {
402 s64 delta;
403 int leap = 0;
404 s32 rem;
405
406 /*
407 * Leap second processing. If in leap-insert state at the end of the
408 * day, the system clock is set back one second; if in leap-delete
409 * state, the system clock is set ahead one second.
410 */
411 switch (time_state) {
412 case TIME_OK:
413 if (time_status & STA_INS) {
414 time_state = TIME_INS;
415 div_s64_rem(secs, SECS_PER_DAY, &rem);
416 ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
417 } else if (time_status & STA_DEL) {
418 time_state = TIME_DEL;
419 div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
420 ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
421 }
422 break;
423 case TIME_INS:
424 if (!(time_status & STA_INS)) {
425 ntp_next_leap_sec = TIME64_MAX;
426 time_state = TIME_OK;
427 } else if (secs == ntp_next_leap_sec) {
428 leap = -1;
429 time_state = TIME_OOP;
430 printk(KERN_NOTICE
431 "Clock: inserting leap second 23:59:60 UTC\n");
432 }
433 break;
434 case TIME_DEL:
435 if (!(time_status & STA_DEL)) {
436 ntp_next_leap_sec = TIME64_MAX;
437 time_state = TIME_OK;
438 } else if (secs == ntp_next_leap_sec) {
439 leap = 1;
440 ntp_next_leap_sec = TIME64_MAX;
441 time_state = TIME_WAIT;
442 printk(KERN_NOTICE
443 "Clock: deleting leap second 23:59:59 UTC\n");
444 }
445 break;
446 case TIME_OOP:
447 ntp_next_leap_sec = TIME64_MAX;
448 time_state = TIME_WAIT;
449 break;
450 case TIME_WAIT:
451 if (!(time_status & (STA_INS | STA_DEL)))
452 time_state = TIME_OK;
453 break;
454 }
455
456
457 /* Bump the maxerror field */
458 time_maxerror += MAXFREQ / NSEC_PER_USEC;
459 if (time_maxerror > NTP_PHASE_LIMIT) {
460 time_maxerror = NTP_PHASE_LIMIT;
461 time_status |= STA_UNSYNC;
462 }
463
464 /* Compute the phase adjustment for the next second */
465 tick_length = tick_length_base;
466
467 delta = ntp_offset_chunk(time_offset);
468 time_offset -= delta;
469 tick_length += delta;
470
471 /* Check PPS signal */
472 pps_dec_valid();
473
474 if (!time_adjust)
475 goto out;
476
477 if (time_adjust > MAX_TICKADJ) {
478 time_adjust -= MAX_TICKADJ;
479 tick_length += MAX_TICKADJ_SCALED;
480 goto out;
481 }
482
483 if (time_adjust < -MAX_TICKADJ) {
484 time_adjust += MAX_TICKADJ;
485 tick_length -= MAX_TICKADJ_SCALED;
486 goto out;
487 }
488
489 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
490 << NTP_SCALE_SHIFT;
491 time_adjust = 0;
492
493 out:
494 return leap;
495 }
496
497 static void sync_hw_clock(struct work_struct *work);
498 static DECLARE_DELAYED_WORK(sync_work, sync_hw_clock);
499
sched_sync_hw_clock(struct timespec64 now,unsigned long target_nsec,bool fail)500 static void sched_sync_hw_clock(struct timespec64 now,
501 unsigned long target_nsec, bool fail)
502
503 {
504 struct timespec64 next;
505
506 ktime_get_real_ts64(&next);
507 if (!fail)
508 next.tv_sec = 659;
509 else {
510 /*
511 * Try again as soon as possible. Delaying long periods
512 * decreases the accuracy of the work queue timer. Due to this
513 * the algorithm is very likely to require a short-sleep retry
514 * after the above long sleep to synchronize ts_nsec.
515 */
516 next.tv_sec = 0;
517 }
518
519 /* Compute the needed delay that will get to tv_nsec == target_nsec */
520 next.tv_nsec = target_nsec - next.tv_nsec;
521 if (next.tv_nsec <= 0)
522 next.tv_nsec += NSEC_PER_SEC;
523 if (next.tv_nsec >= NSEC_PER_SEC) {
524 next.tv_sec++;
525 next.tv_nsec -= NSEC_PER_SEC;
526 }
527
528 queue_delayed_work(system_power_efficient_wq, &sync_work,
529 timespec64_to_jiffies(&next));
530 }
531
sync_rtc_clock(void)532 static void sync_rtc_clock(void)
533 {
534 unsigned long target_nsec;
535 struct timespec64 adjust, now;
536 int rc;
537
538 if (!IS_ENABLED(CONFIG_RTC_SYSTOHC))
539 return;
540
541 ktime_get_real_ts64(&now);
542
543 adjust = now;
544 if (persistent_clock_is_local)
545 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
546
547 /*
548 * The current RTC in use will provide the target_nsec it wants to be
549 * called at, and does rtc_tv_nsec_ok internally.
550 */
551 rc = rtc_set_ntp_time(adjust, &target_nsec);
552 if (rc == -ENODEV)
553 return;
554
555 sched_sync_hw_clock(now, target_nsec, rc);
556 }
557
558 #ifdef CONFIG_GENERIC_CMOS_UPDATE
update_persistent_clock64(struct timespec64 now64)559 int __weak update_persistent_clock64(struct timespec64 now64)
560 {
561 return -ENODEV;
562 }
563 #endif
564
sync_cmos_clock(void)565 static bool sync_cmos_clock(void)
566 {
567 static bool no_cmos;
568 struct timespec64 now;
569 struct timespec64 adjust;
570 int rc = -EPROTO;
571 long target_nsec = NSEC_PER_SEC / 2;
572
573 if (!IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE))
574 return false;
575
576 if (no_cmos)
577 return false;
578
579 /*
580 * Historically update_persistent_clock64() has followed x86
581 * semantics, which match the MC146818A/etc RTC. This RTC will store
582 * 'adjust' and then in .5s it will advance once second.
583 *
584 * Architectures are strongly encouraged to use rtclib and not
585 * implement this legacy API.
586 */
587 ktime_get_real_ts64(&now);
588 if (rtc_tv_nsec_ok(-1 * target_nsec, &adjust, &now)) {
589 if (persistent_clock_is_local)
590 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
591 rc = update_persistent_clock64(adjust);
592 /*
593 * The machine does not support update_persistent_clock64 even
594 * though it defines CONFIG_GENERIC_CMOS_UPDATE.
595 */
596 if (rc == -ENODEV) {
597 no_cmos = true;
598 return false;
599 }
600 }
601
602 sched_sync_hw_clock(now, target_nsec, rc);
603 return true;
604 }
605
606 /*
607 * If we have an externally synchronized Linux clock, then update RTC clock
608 * accordingly every ~11 minutes. Generally RTCs can only store second
609 * precision, but many RTCs will adjust the phase of their second tick to
610 * match the moment of update. This infrastructure arranges to call to the RTC
611 * set at the correct moment to phase synchronize the RTC second tick over
612 * with the kernel clock.
613 */
sync_hw_clock(struct work_struct * work)614 static void sync_hw_clock(struct work_struct *work)
615 {
616 if (!ntp_synced())
617 return;
618
619 if (sync_cmos_clock())
620 return;
621
622 sync_rtc_clock();
623 }
624
ntp_notify_cmos_timer(void)625 void ntp_notify_cmos_timer(void)
626 {
627 if (!ntp_synced())
628 return;
629
630 if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) ||
631 IS_ENABLED(CONFIG_RTC_SYSTOHC))
632 queue_delayed_work(system_power_efficient_wq, &sync_work, 0);
633 }
634
635 /*
636 * Propagate a new txc->status value into the NTP state:
637 */
process_adj_status(const struct __kernel_timex * txc)638 static inline void process_adj_status(const struct __kernel_timex *txc)
639 {
640 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
641 time_state = TIME_OK;
642 time_status = STA_UNSYNC;
643 ntp_next_leap_sec = TIME64_MAX;
644 /* restart PPS frequency calibration */
645 pps_reset_freq_interval();
646 }
647
648 /*
649 * If we turn on PLL adjustments then reset the
650 * reference time to current time.
651 */
652 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
653 time_reftime = __ktime_get_real_seconds();
654
655 /* only set allowed bits */
656 time_status &= STA_RONLY;
657 time_status |= txc->status & ~STA_RONLY;
658 }
659
660
process_adjtimex_modes(const struct __kernel_timex * txc,s32 * time_tai)661 static inline void process_adjtimex_modes(const struct __kernel_timex *txc,
662 s32 *time_tai)
663 {
664 if (txc->modes & ADJ_STATUS)
665 process_adj_status(txc);
666
667 if (txc->modes & ADJ_NANO)
668 time_status |= STA_NANO;
669
670 if (txc->modes & ADJ_MICRO)
671 time_status &= ~STA_NANO;
672
673 if (txc->modes & ADJ_FREQUENCY) {
674 time_freq = txc->freq * PPM_SCALE;
675 time_freq = min(time_freq, MAXFREQ_SCALED);
676 time_freq = max(time_freq, -MAXFREQ_SCALED);
677 /* update pps_freq */
678 pps_set_freq(time_freq);
679 }
680
681 if (txc->modes & ADJ_MAXERROR)
682 time_maxerror = txc->maxerror;
683
684 if (txc->modes & ADJ_ESTERROR)
685 time_esterror = txc->esterror;
686
687 if (txc->modes & ADJ_TIMECONST) {
688 time_constant = txc->constant;
689 if (!(time_status & STA_NANO))
690 time_constant += 4;
691 time_constant = min(time_constant, (long)MAXTC);
692 time_constant = max(time_constant, 0l);
693 }
694
695 if (txc->modes & ADJ_TAI &&
696 txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
697 *time_tai = txc->constant;
698
699 if (txc->modes & ADJ_OFFSET)
700 ntp_update_offset(txc->offset);
701
702 if (txc->modes & ADJ_TICK)
703 tick_usec = txc->tick;
704
705 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
706 ntp_update_frequency();
707 }
708
709
710 /*
711 * adjtimex mainly allows reading (and writing, if superuser) of
712 * kernel time-keeping variables. used by xntpd.
713 */
__do_adjtimex(struct __kernel_timex * txc,const struct timespec64 * ts,s32 * time_tai,struct audit_ntp_data * ad)714 int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts,
715 s32 *time_tai, struct audit_ntp_data *ad)
716 {
717 int result;
718
719 if (txc->modes & ADJ_ADJTIME) {
720 long save_adjust = time_adjust;
721
722 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
723 /* adjtime() is independent from ntp_adjtime() */
724 time_adjust = txc->offset;
725 ntp_update_frequency();
726
727 audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust);
728 audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, time_adjust);
729 }
730 txc->offset = save_adjust;
731 } else {
732 /* If there are input parameters, then process them: */
733 if (txc->modes) {
734 audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, time_offset);
735 audit_ntp_set_old(ad, AUDIT_NTP_FREQ, time_freq);
736 audit_ntp_set_old(ad, AUDIT_NTP_STATUS, time_status);
737 audit_ntp_set_old(ad, AUDIT_NTP_TAI, *time_tai);
738 audit_ntp_set_old(ad, AUDIT_NTP_TICK, tick_usec);
739
740 process_adjtimex_modes(txc, time_tai);
741
742 audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, time_offset);
743 audit_ntp_set_new(ad, AUDIT_NTP_FREQ, time_freq);
744 audit_ntp_set_new(ad, AUDIT_NTP_STATUS, time_status);
745 audit_ntp_set_new(ad, AUDIT_NTP_TAI, *time_tai);
746 audit_ntp_set_new(ad, AUDIT_NTP_TICK, tick_usec);
747 }
748
749 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
750 NTP_SCALE_SHIFT);
751 if (!(time_status & STA_NANO))
752 txc->offset = (u32)txc->offset / NSEC_PER_USEC;
753 }
754
755 result = time_state; /* mostly `TIME_OK' */
756 /* check for errors */
757 if (is_error_status(time_status))
758 result = TIME_ERROR;
759
760 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
761 PPM_SCALE_INV, NTP_SCALE_SHIFT);
762 txc->maxerror = time_maxerror;
763 txc->esterror = time_esterror;
764 txc->status = time_status;
765 txc->constant = time_constant;
766 txc->precision = 1;
767 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
768 txc->tick = tick_usec;
769 txc->tai = *time_tai;
770
771 /* fill PPS status fields */
772 pps_fill_timex(txc);
773
774 txc->time.tv_sec = ts->tv_sec;
775 txc->time.tv_usec = ts->tv_nsec;
776 if (!(time_status & STA_NANO))
777 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;
778
779 /* Handle leapsec adjustments */
780 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
781 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
782 result = TIME_OOP;
783 txc->tai++;
784 txc->time.tv_sec--;
785 }
786 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
787 result = TIME_WAIT;
788 txc->tai--;
789 txc->time.tv_sec++;
790 }
791 if ((time_state == TIME_OOP) &&
792 (ts->tv_sec == ntp_next_leap_sec)) {
793 result = TIME_WAIT;
794 }
795 }
796
797 return result;
798 }
799
800 #ifdef CONFIG_NTP_PPS
801
802 /* actually struct pps_normtime is good old struct timespec, but it is
803 * semantically different (and it is the reason why it was invented):
804 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
805 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
806 struct pps_normtime {
807 s64 sec; /* seconds */
808 long nsec; /* nanoseconds */
809 };
810
811 /* normalize the timestamp so that nsec is in the
812 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
pps_normalize_ts(struct timespec64 ts)813 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
814 {
815 struct pps_normtime norm = {
816 .sec = ts.tv_sec,
817 .nsec = ts.tv_nsec
818 };
819
820 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
821 norm.nsec -= NSEC_PER_SEC;
822 norm.sec++;
823 }
824
825 return norm;
826 }
827
828 /* get current phase correction and jitter */
pps_phase_filter_get(long * jitter)829 static inline long pps_phase_filter_get(long *jitter)
830 {
831 *jitter = pps_tf[0] - pps_tf[1];
832 if (*jitter < 0)
833 *jitter = -*jitter;
834
835 /* TODO: test various filters */
836 return pps_tf[0];
837 }
838
839 /* add the sample to the phase filter */
pps_phase_filter_add(long err)840 static inline void pps_phase_filter_add(long err)
841 {
842 pps_tf[2] = pps_tf[1];
843 pps_tf[1] = pps_tf[0];
844 pps_tf[0] = err;
845 }
846
847 /* decrease frequency calibration interval length.
848 * It is halved after four consecutive unstable intervals.
849 */
pps_dec_freq_interval(void)850 static inline void pps_dec_freq_interval(void)
851 {
852 if (--pps_intcnt <= -PPS_INTCOUNT) {
853 pps_intcnt = -PPS_INTCOUNT;
854 if (pps_shift > PPS_INTMIN) {
855 pps_shift--;
856 pps_intcnt = 0;
857 }
858 }
859 }
860
861 /* increase frequency calibration interval length.
862 * It is doubled after four consecutive stable intervals.
863 */
pps_inc_freq_interval(void)864 static inline void pps_inc_freq_interval(void)
865 {
866 if (++pps_intcnt >= PPS_INTCOUNT) {
867 pps_intcnt = PPS_INTCOUNT;
868 if (pps_shift < PPS_INTMAX) {
869 pps_shift++;
870 pps_intcnt = 0;
871 }
872 }
873 }
874
875 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
876 * timestamps
877 *
878 * At the end of the calibration interval the difference between the
879 * first and last MONOTONIC_RAW clock timestamps divided by the length
880 * of the interval becomes the frequency update. If the interval was
881 * too long, the data are discarded.
882 * Returns the difference between old and new frequency values.
883 */
hardpps_update_freq(struct pps_normtime freq_norm)884 static long hardpps_update_freq(struct pps_normtime freq_norm)
885 {
886 long delta, delta_mod;
887 s64 ftemp;
888
889 /* check if the frequency interval was too long */
890 if (freq_norm.sec > (2 << pps_shift)) {
891 time_status |= STA_PPSERROR;
892 pps_errcnt++;
893 pps_dec_freq_interval();
894 printk_deferred(KERN_ERR
895 "hardpps: PPSERROR: interval too long - %lld s\n",
896 freq_norm.sec);
897 return 0;
898 }
899
900 /* here the raw frequency offset and wander (stability) is
901 * calculated. If the wander is less than the wander threshold
902 * the interval is increased; otherwise it is decreased.
903 */
904 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
905 freq_norm.sec);
906 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
907 pps_freq = ftemp;
908 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
909 printk_deferred(KERN_WARNING
910 "hardpps: PPSWANDER: change=%ld\n", delta);
911 time_status |= STA_PPSWANDER;
912 pps_stbcnt++;
913 pps_dec_freq_interval();
914 } else { /* good sample */
915 pps_inc_freq_interval();
916 }
917
918 /* the stability metric is calculated as the average of recent
919 * frequency changes, but is used only for performance
920 * monitoring
921 */
922 delta_mod = delta;
923 if (delta_mod < 0)
924 delta_mod = -delta_mod;
925 pps_stabil += (div_s64(((s64)delta_mod) <<
926 (NTP_SCALE_SHIFT - SHIFT_USEC),
927 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
928
929 /* if enabled, the system clock frequency is updated */
930 if ((time_status & STA_PPSFREQ) != 0 &&
931 (time_status & STA_FREQHOLD) == 0) {
932 time_freq = pps_freq;
933 ntp_update_frequency();
934 }
935
936 return delta;
937 }
938
939 /* correct REALTIME clock phase error against PPS signal */
hardpps_update_phase(long error)940 static void hardpps_update_phase(long error)
941 {
942 long correction = -error;
943 long jitter;
944
945 /* add the sample to the median filter */
946 pps_phase_filter_add(correction);
947 correction = pps_phase_filter_get(&jitter);
948
949 /* Nominal jitter is due to PPS signal noise. If it exceeds the
950 * threshold, the sample is discarded; otherwise, if so enabled,
951 * the time offset is updated.
952 */
953 if (jitter > (pps_jitter << PPS_POPCORN)) {
954 printk_deferred(KERN_WARNING
955 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
956 jitter, (pps_jitter << PPS_POPCORN));
957 time_status |= STA_PPSJITTER;
958 pps_jitcnt++;
959 } else if (time_status & STA_PPSTIME) {
960 /* correct the time using the phase offset */
961 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
962 NTP_INTERVAL_FREQ);
963 /* cancel running adjtime() */
964 time_adjust = 0;
965 }
966 /* update jitter */
967 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
968 }
969
970 /*
971 * __hardpps() - discipline CPU clock oscillator to external PPS signal
972 *
973 * This routine is called at each PPS signal arrival in order to
974 * discipline the CPU clock oscillator to the PPS signal. It takes two
975 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
976 * is used to correct clock phase error and the latter is used to
977 * correct the frequency.
978 *
979 * This code is based on David Mills's reference nanokernel
980 * implementation. It was mostly rewritten but keeps the same idea.
981 */
__hardpps(const struct timespec64 * phase_ts,const struct timespec64 * raw_ts)982 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
983 {
984 struct pps_normtime pts_norm, freq_norm;
985
986 pts_norm = pps_normalize_ts(*phase_ts);
987
988 /* clear the error bits, they will be set again if needed */
989 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
990
991 /* indicate signal presence */
992 time_status |= STA_PPSSIGNAL;
993 pps_valid = PPS_VALID;
994
995 /* when called for the first time,
996 * just start the frequency interval */
997 if (unlikely(pps_fbase.tv_sec == 0)) {
998 pps_fbase = *raw_ts;
999 return;
1000 }
1001
1002 /* ok, now we have a base for frequency calculation */
1003 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
1004
1005 /* check that the signal is in the range
1006 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
1007 if ((freq_norm.sec == 0) ||
1008 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1009 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1010 time_status |= STA_PPSJITTER;
1011 /* restart the frequency calibration interval */
1012 pps_fbase = *raw_ts;
1013 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1014 return;
1015 }
1016
1017 /* signal is ok */
1018
1019 /* check if the current frequency interval is finished */
1020 if (freq_norm.sec >= (1 << pps_shift)) {
1021 pps_calcnt++;
1022 /* restart the frequency calibration interval */
1023 pps_fbase = *raw_ts;
1024 hardpps_update_freq(freq_norm);
1025 }
1026
1027 hardpps_update_phase(pts_norm.nsec);
1028
1029 }
1030 #endif /* CONFIG_NTP_PPS */
1031
ntp_tick_adj_setup(char * str)1032 static int __init ntp_tick_adj_setup(char *str)
1033 {
1034 int rc = kstrtos64(str, 0, &ntp_tick_adj);
1035 if (rc)
1036 return rc;
1037
1038 ntp_tick_adj <<= NTP_SCALE_SHIFT;
1039 return 1;
1040 }
1041
1042 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1043
ntp_init(void)1044 void __init ntp_init(void)
1045 {
1046 ntp_clear();
1047 }
1048