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 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
498 static void sync_hw_clock(struct work_struct *work);
499 static DECLARE_WORK(sync_work, sync_hw_clock);
500 static struct hrtimer sync_hrtimer;
501 #define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC)
502
sync_timer_callback(struct hrtimer * timer)503 static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
504 {
505 queue_work(system_freezable_power_efficient_wq, &sync_work);
506
507 return HRTIMER_NORESTART;
508 }
509
sched_sync_hw_clock(unsigned long offset_nsec,bool retry)510 static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry)
511 {
512 ktime_t exp = ktime_set(ktime_get_real_seconds(), 0);
513
514 if (retry)
515 exp = ktime_add_ns(exp, 2ULL * NSEC_PER_SEC - offset_nsec);
516 else
517 exp = ktime_add_ns(exp, SYNC_PERIOD_NS - offset_nsec);
518
519 hrtimer_start(&sync_hrtimer, exp, HRTIMER_MODE_ABS);
520 }
521
522 /*
523 * Check whether @now is correct versus the required time to update the RTC
524 * and calculate the value which needs to be written to the RTC so that the
525 * next seconds increment of the RTC after the write is aligned with the next
526 * seconds increment of clock REALTIME.
527 *
528 * tsched t1 write(t2.tv_sec - 1sec)) t2 RTC increments seconds
529 *
530 * t2.tv_nsec == 0
531 * tsched = t2 - set_offset_nsec
532 * newval = t2 - NSEC_PER_SEC
533 *
534 * ==> neval = tsched + set_offset_nsec - NSEC_PER_SEC
535 *
536 * As the execution of this code is not guaranteed to happen exactly at
537 * tsched this allows it to happen within a fuzzy region:
538 *
539 * abs(now - tsched) < FUZZ
540 *
541 * If @now is not inside the allowed window the function returns false.
542 */
rtc_tv_nsec_ok(unsigned long set_offset_nsec,struct timespec64 * to_set,const struct timespec64 * now)543 static inline bool rtc_tv_nsec_ok(unsigned long set_offset_nsec,
544 struct timespec64 *to_set,
545 const struct timespec64 *now)
546 {
547 /* Allowed error in tv_nsec, arbitrarily set to 5 jiffies in ns. */
548 const unsigned long TIME_SET_NSEC_FUZZ = TICK_NSEC * 5;
549 struct timespec64 delay = {.tv_sec = -1,
550 .tv_nsec = set_offset_nsec};
551
552 *to_set = timespec64_add(*now, delay);
553
554 if (to_set->tv_nsec < TIME_SET_NSEC_FUZZ) {
555 to_set->tv_nsec = 0;
556 return true;
557 }
558
559 if (to_set->tv_nsec > NSEC_PER_SEC - TIME_SET_NSEC_FUZZ) {
560 to_set->tv_sec++;
561 to_set->tv_nsec = 0;
562 return true;
563 }
564 return false;
565 }
566
567 #ifdef CONFIG_GENERIC_CMOS_UPDATE
update_persistent_clock64(struct timespec64 now64)568 int __weak update_persistent_clock64(struct timespec64 now64)
569 {
570 return -ENODEV;
571 }
572 #else
update_persistent_clock64(struct timespec64 now64)573 static inline int update_persistent_clock64(struct timespec64 now64)
574 {
575 return -ENODEV;
576 }
577 #endif
578
579 #ifdef CONFIG_RTC_SYSTOHC
580 /* Save NTP synchronized time to the RTC */
update_rtc(struct timespec64 * to_set,unsigned long * offset_nsec)581 static int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
582 {
583 struct rtc_device *rtc;
584 struct rtc_time tm;
585 int err = -ENODEV;
586
587 rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
588 if (!rtc)
589 return -ENODEV;
590
591 if (!rtc->ops || !rtc->ops->set_time)
592 goto out_close;
593
594 /* First call might not have the correct offset */
595 if (*offset_nsec == rtc->set_offset_nsec) {
596 rtc_time64_to_tm(to_set->tv_sec, &tm);
597 err = rtc_set_time(rtc, &tm);
598 } else {
599 /* Store the update offset and let the caller try again */
600 *offset_nsec = rtc->set_offset_nsec;
601 err = -EAGAIN;
602 }
603 out_close:
604 rtc_class_close(rtc);
605 return err;
606 }
607 #else
update_rtc(struct timespec64 * to_set,unsigned long * offset_nsec)608 static inline int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
609 {
610 return -ENODEV;
611 }
612 #endif
613
614 /*
615 * If we have an externally synchronized Linux clock, then update RTC clock
616 * accordingly every ~11 minutes. Generally RTCs can only store second
617 * precision, but many RTCs will adjust the phase of their second tick to
618 * match the moment of update. This infrastructure arranges to call to the RTC
619 * set at the correct moment to phase synchronize the RTC second tick over
620 * with the kernel clock.
621 */
sync_hw_clock(struct work_struct * work)622 static void sync_hw_clock(struct work_struct *work)
623 {
624 /*
625 * The default synchronization offset is 500ms for the deprecated
626 * update_persistent_clock64() under the assumption that it uses
627 * the infamous CMOS clock (MC146818).
628 */
629 static unsigned long offset_nsec = NSEC_PER_SEC / 2;
630 struct timespec64 now, to_set;
631 int res = -EAGAIN;
632
633 /*
634 * Don't update if STA_UNSYNC is set and if ntp_notify_cmos_timer()
635 * managed to schedule the work between the timer firing and the
636 * work being able to rearm the timer. Wait for the timer to expire.
637 */
638 if (!ntp_synced() || hrtimer_is_queued(&sync_hrtimer))
639 return;
640
641 ktime_get_real_ts64(&now);
642 /* If @now is not in the allowed window, try again */
643 if (!rtc_tv_nsec_ok(offset_nsec, &to_set, &now))
644 goto rearm;
645
646 /* Take timezone adjusted RTCs into account */
647 if (persistent_clock_is_local)
648 to_set.tv_sec -= (sys_tz.tz_minuteswest * 60);
649
650 /* Try the legacy RTC first. */
651 res = update_persistent_clock64(to_set);
652 if (res != -ENODEV)
653 goto rearm;
654
655 /* Try the RTC class */
656 res = update_rtc(&to_set, &offset_nsec);
657 if (res == -ENODEV)
658 return;
659 rearm:
660 sched_sync_hw_clock(offset_nsec, res != 0);
661 }
662
ntp_notify_cmos_timer(void)663 void ntp_notify_cmos_timer(void)
664 {
665 /*
666 * When the work is currently executed but has not yet the timer
667 * rearmed this queues the work immediately again. No big issue,
668 * just a pointless work scheduled.
669 */
670 if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer))
671 queue_work(system_freezable_power_efficient_wq, &sync_work);
672 }
673
ntp_init_cmos_sync(void)674 static void __init ntp_init_cmos_sync(void)
675 {
676 hrtimer_init(&sync_hrtimer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
677 sync_hrtimer.function = sync_timer_callback;
678 }
679 #else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
ntp_init_cmos_sync(void)680 static inline void __init ntp_init_cmos_sync(void) { }
681 #endif /* !CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
682
683 /*
684 * Propagate a new txc->status value into the NTP state:
685 */
process_adj_status(const struct __kernel_timex * txc)686 static inline void process_adj_status(const struct __kernel_timex *txc)
687 {
688 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
689 time_state = TIME_OK;
690 time_status = STA_UNSYNC;
691 ntp_next_leap_sec = TIME64_MAX;
692 /* restart PPS frequency calibration */
693 pps_reset_freq_interval();
694 }
695
696 /*
697 * If we turn on PLL adjustments then reset the
698 * reference time to current time.
699 */
700 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
701 time_reftime = __ktime_get_real_seconds();
702
703 /* only set allowed bits */
704 time_status &= STA_RONLY;
705 time_status |= txc->status & ~STA_RONLY;
706 }
707
708
process_adjtimex_modes(const struct __kernel_timex * txc,s32 * time_tai)709 static inline void process_adjtimex_modes(const struct __kernel_timex *txc,
710 s32 *time_tai)
711 {
712 if (txc->modes & ADJ_STATUS)
713 process_adj_status(txc);
714
715 if (txc->modes & ADJ_NANO)
716 time_status |= STA_NANO;
717
718 if (txc->modes & ADJ_MICRO)
719 time_status &= ~STA_NANO;
720
721 if (txc->modes & ADJ_FREQUENCY) {
722 time_freq = txc->freq * PPM_SCALE;
723 time_freq = min(time_freq, MAXFREQ_SCALED);
724 time_freq = max(time_freq, -MAXFREQ_SCALED);
725 /* update pps_freq */
726 pps_set_freq(time_freq);
727 }
728
729 if (txc->modes & ADJ_MAXERROR)
730 time_maxerror = clamp(txc->maxerror, 0, NTP_PHASE_LIMIT);
731
732 if (txc->modes & ADJ_ESTERROR)
733 time_esterror = clamp(txc->esterror, 0, NTP_PHASE_LIMIT);
734
735 if (txc->modes & ADJ_TIMECONST) {
736 time_constant = clamp(txc->constant, 0, MAXTC);
737 if (!(time_status & STA_NANO))
738 time_constant += 4;
739 time_constant = clamp(time_constant, 0, MAXTC);
740 }
741
742 if (txc->modes & ADJ_TAI &&
743 txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
744 *time_tai = txc->constant;
745
746 if (txc->modes & ADJ_OFFSET)
747 ntp_update_offset(txc->offset);
748
749 if (txc->modes & ADJ_TICK)
750 tick_usec = txc->tick;
751
752 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
753 ntp_update_frequency();
754 }
755
756
757 /*
758 * adjtimex mainly allows reading (and writing, if superuser) of
759 * kernel time-keeping variables. used by xntpd.
760 */
__do_adjtimex(struct __kernel_timex * txc,const struct timespec64 * ts,s32 * time_tai,struct audit_ntp_data * ad)761 int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts,
762 s32 *time_tai, struct audit_ntp_data *ad)
763 {
764 int result;
765
766 if (txc->modes & ADJ_ADJTIME) {
767 long save_adjust = time_adjust;
768
769 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
770 /* adjtime() is independent from ntp_adjtime() */
771 time_adjust = txc->offset;
772 ntp_update_frequency();
773
774 audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust);
775 audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, time_adjust);
776 }
777 txc->offset = save_adjust;
778 } else {
779 /* If there are input parameters, then process them: */
780 if (txc->modes) {
781 audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, time_offset);
782 audit_ntp_set_old(ad, AUDIT_NTP_FREQ, time_freq);
783 audit_ntp_set_old(ad, AUDIT_NTP_STATUS, time_status);
784 audit_ntp_set_old(ad, AUDIT_NTP_TAI, *time_tai);
785 audit_ntp_set_old(ad, AUDIT_NTP_TICK, tick_usec);
786
787 process_adjtimex_modes(txc, time_tai);
788
789 audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, time_offset);
790 audit_ntp_set_new(ad, AUDIT_NTP_FREQ, time_freq);
791 audit_ntp_set_new(ad, AUDIT_NTP_STATUS, time_status);
792 audit_ntp_set_new(ad, AUDIT_NTP_TAI, *time_tai);
793 audit_ntp_set_new(ad, AUDIT_NTP_TICK, tick_usec);
794 }
795
796 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
797 NTP_SCALE_SHIFT);
798 if (!(time_status & STA_NANO))
799 txc->offset = (u32)txc->offset / NSEC_PER_USEC;
800 }
801
802 result = time_state; /* mostly `TIME_OK' */
803 /* check for errors */
804 if (is_error_status(time_status))
805 result = TIME_ERROR;
806
807 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
808 PPM_SCALE_INV, NTP_SCALE_SHIFT);
809 txc->maxerror = time_maxerror;
810 txc->esterror = time_esterror;
811 txc->status = time_status;
812 txc->constant = time_constant;
813 txc->precision = 1;
814 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
815 txc->tick = tick_usec;
816 txc->tai = *time_tai;
817
818 /* fill PPS status fields */
819 pps_fill_timex(txc);
820
821 txc->time.tv_sec = ts->tv_sec;
822 txc->time.tv_usec = ts->tv_nsec;
823 if (!(time_status & STA_NANO))
824 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;
825
826 /* Handle leapsec adjustments */
827 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
828 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
829 result = TIME_OOP;
830 txc->tai++;
831 txc->time.tv_sec--;
832 }
833 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
834 result = TIME_WAIT;
835 txc->tai--;
836 txc->time.tv_sec++;
837 }
838 if ((time_state == TIME_OOP) &&
839 (ts->tv_sec == ntp_next_leap_sec)) {
840 result = TIME_WAIT;
841 }
842 }
843
844 return result;
845 }
846
847 #ifdef CONFIG_NTP_PPS
848
849 /* actually struct pps_normtime is good old struct timespec, but it is
850 * semantically different (and it is the reason why it was invented):
851 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
852 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
853 struct pps_normtime {
854 s64 sec; /* seconds */
855 long nsec; /* nanoseconds */
856 };
857
858 /* normalize the timestamp so that nsec is in the
859 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
pps_normalize_ts(struct timespec64 ts)860 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
861 {
862 struct pps_normtime norm = {
863 .sec = ts.tv_sec,
864 .nsec = ts.tv_nsec
865 };
866
867 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
868 norm.nsec -= NSEC_PER_SEC;
869 norm.sec++;
870 }
871
872 return norm;
873 }
874
875 /* get current phase correction and jitter */
pps_phase_filter_get(long * jitter)876 static inline long pps_phase_filter_get(long *jitter)
877 {
878 *jitter = pps_tf[0] - pps_tf[1];
879 if (*jitter < 0)
880 *jitter = -*jitter;
881
882 /* TODO: test various filters */
883 return pps_tf[0];
884 }
885
886 /* add the sample to the phase filter */
pps_phase_filter_add(long err)887 static inline void pps_phase_filter_add(long err)
888 {
889 pps_tf[2] = pps_tf[1];
890 pps_tf[1] = pps_tf[0];
891 pps_tf[0] = err;
892 }
893
894 /* decrease frequency calibration interval length.
895 * It is halved after four consecutive unstable intervals.
896 */
pps_dec_freq_interval(void)897 static inline void pps_dec_freq_interval(void)
898 {
899 if (--pps_intcnt <= -PPS_INTCOUNT) {
900 pps_intcnt = -PPS_INTCOUNT;
901 if (pps_shift > PPS_INTMIN) {
902 pps_shift--;
903 pps_intcnt = 0;
904 }
905 }
906 }
907
908 /* increase frequency calibration interval length.
909 * It is doubled after four consecutive stable intervals.
910 */
pps_inc_freq_interval(void)911 static inline void pps_inc_freq_interval(void)
912 {
913 if (++pps_intcnt >= PPS_INTCOUNT) {
914 pps_intcnt = PPS_INTCOUNT;
915 if (pps_shift < PPS_INTMAX) {
916 pps_shift++;
917 pps_intcnt = 0;
918 }
919 }
920 }
921
922 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
923 * timestamps
924 *
925 * At the end of the calibration interval the difference between the
926 * first and last MONOTONIC_RAW clock timestamps divided by the length
927 * of the interval becomes the frequency update. If the interval was
928 * too long, the data are discarded.
929 * Returns the difference between old and new frequency values.
930 */
hardpps_update_freq(struct pps_normtime freq_norm)931 static long hardpps_update_freq(struct pps_normtime freq_norm)
932 {
933 long delta, delta_mod;
934 s64 ftemp;
935
936 /* check if the frequency interval was too long */
937 if (freq_norm.sec > (2 << pps_shift)) {
938 time_status |= STA_PPSERROR;
939 pps_errcnt++;
940 pps_dec_freq_interval();
941 printk_deferred(KERN_ERR
942 "hardpps: PPSERROR: interval too long - %lld s\n",
943 freq_norm.sec);
944 return 0;
945 }
946
947 /* here the raw frequency offset and wander (stability) is
948 * calculated. If the wander is less than the wander threshold
949 * the interval is increased; otherwise it is decreased.
950 */
951 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
952 freq_norm.sec);
953 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
954 pps_freq = ftemp;
955 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
956 printk_deferred(KERN_WARNING
957 "hardpps: PPSWANDER: change=%ld\n", delta);
958 time_status |= STA_PPSWANDER;
959 pps_stbcnt++;
960 pps_dec_freq_interval();
961 } else { /* good sample */
962 pps_inc_freq_interval();
963 }
964
965 /* the stability metric is calculated as the average of recent
966 * frequency changes, but is used only for performance
967 * monitoring
968 */
969 delta_mod = delta;
970 if (delta_mod < 0)
971 delta_mod = -delta_mod;
972 pps_stabil += (div_s64(((s64)delta_mod) <<
973 (NTP_SCALE_SHIFT - SHIFT_USEC),
974 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
975
976 /* if enabled, the system clock frequency is updated */
977 if ((time_status & STA_PPSFREQ) != 0 &&
978 (time_status & STA_FREQHOLD) == 0) {
979 time_freq = pps_freq;
980 ntp_update_frequency();
981 }
982
983 return delta;
984 }
985
986 /* correct REALTIME clock phase error against PPS signal */
hardpps_update_phase(long error)987 static void hardpps_update_phase(long error)
988 {
989 long correction = -error;
990 long jitter;
991
992 /* add the sample to the median filter */
993 pps_phase_filter_add(correction);
994 correction = pps_phase_filter_get(&jitter);
995
996 /* Nominal jitter is due to PPS signal noise. If it exceeds the
997 * threshold, the sample is discarded; otherwise, if so enabled,
998 * the time offset is updated.
999 */
1000 if (jitter > (pps_jitter << PPS_POPCORN)) {
1001 printk_deferred(KERN_WARNING
1002 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
1003 jitter, (pps_jitter << PPS_POPCORN));
1004 time_status |= STA_PPSJITTER;
1005 pps_jitcnt++;
1006 } else if (time_status & STA_PPSTIME) {
1007 /* correct the time using the phase offset */
1008 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
1009 NTP_INTERVAL_FREQ);
1010 /* cancel running adjtime() */
1011 time_adjust = 0;
1012 }
1013 /* update jitter */
1014 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
1015 }
1016
1017 /*
1018 * __hardpps() - discipline CPU clock oscillator to external PPS signal
1019 *
1020 * This routine is called at each PPS signal arrival in order to
1021 * discipline the CPU clock oscillator to the PPS signal. It takes two
1022 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
1023 * is used to correct clock phase error and the latter is used to
1024 * correct the frequency.
1025 *
1026 * This code is based on David Mills's reference nanokernel
1027 * implementation. It was mostly rewritten but keeps the same idea.
1028 */
__hardpps(const struct timespec64 * phase_ts,const struct timespec64 * raw_ts)1029 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
1030 {
1031 struct pps_normtime pts_norm, freq_norm;
1032
1033 pts_norm = pps_normalize_ts(*phase_ts);
1034
1035 /* clear the error bits, they will be set again if needed */
1036 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
1037
1038 /* indicate signal presence */
1039 time_status |= STA_PPSSIGNAL;
1040 pps_valid = PPS_VALID;
1041
1042 /* when called for the first time,
1043 * just start the frequency interval */
1044 if (unlikely(pps_fbase.tv_sec == 0)) {
1045 pps_fbase = *raw_ts;
1046 return;
1047 }
1048
1049 /* ok, now we have a base for frequency calculation */
1050 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
1051
1052 /* check that the signal is in the range
1053 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
1054 if ((freq_norm.sec == 0) ||
1055 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1056 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1057 time_status |= STA_PPSJITTER;
1058 /* restart the frequency calibration interval */
1059 pps_fbase = *raw_ts;
1060 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1061 return;
1062 }
1063
1064 /* signal is ok */
1065
1066 /* check if the current frequency interval is finished */
1067 if (freq_norm.sec >= (1 << pps_shift)) {
1068 pps_calcnt++;
1069 /* restart the frequency calibration interval */
1070 pps_fbase = *raw_ts;
1071 hardpps_update_freq(freq_norm);
1072 }
1073
1074 hardpps_update_phase(pts_norm.nsec);
1075
1076 }
1077 #endif /* CONFIG_NTP_PPS */
1078
ntp_tick_adj_setup(char * str)1079 static int __init ntp_tick_adj_setup(char *str)
1080 {
1081 int rc = kstrtos64(str, 0, &ntp_tick_adj);
1082 if (rc)
1083 return rc;
1084
1085 ntp_tick_adj <<= NTP_SCALE_SHIFT;
1086 return 1;
1087 }
1088
1089 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1090
ntp_init(void)1091 void __init ntp_init(void)
1092 {
1093 ntp_clear();
1094 ntp_init_cmos_sync();
1095 }
1096