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#include <linux/timekeeper_internal.h>
22
23#include "ntp_internal.h"
24#include "timekeeping_internal.h"
25
26/**
27 * struct ntp_data - Structure holding all NTP related state
28 * @tick_usec: USER_HZ period in microseconds
29 * @tick_length: Adjusted tick length
30 * @tick_length_base: Base value for @tick_length
31 * @time_state: State of the clock synchronization
32 * @time_status: Clock status bits
33 * @time_offset: Time adjustment in nanoseconds
34 * @time_constant: PLL time constant
35 * @time_maxerror: Maximum error in microseconds holding the NTP sync distance
36 * (NTP dispersion + delay / 2)
37 * @time_esterror: Estimated error in microseconds holding NTP dispersion
38 * @time_freq: Frequency offset scaled nsecs/secs
39 * @time_reftime: Time at last adjustment in seconds
40 * @time_adjust: Adjustment value
41 * @ntp_tick_adj: Constant boot-param configurable NTP tick adjustment (upscaled)
42 * @ntp_next_leap_sec: Second value of the next pending leapsecond, or TIME64_MAX if no leap
43 *
44 * @pps_valid: PPS signal watchdog counter
45 * @pps_tf: PPS phase median filter
46 * @pps_jitter: PPS current jitter in nanoseconds
47 * @pps_fbase: PPS beginning of the last freq interval
48 * @pps_shift: PPS current interval duration in seconds (shift value)
49 * @pps_intcnt: PPS interval counter
50 * @pps_freq: PPS frequency offset in scaled ns/s
51 * @pps_stabil: PPS current stability in scaled ns/s
52 * @pps_calcnt: PPS monitor: calibration intervals
53 * @pps_jitcnt: PPS monitor: jitter limit exceeded
54 * @pps_stbcnt: PPS monitor: stability limit exceeded
55 * @pps_errcnt: PPS monitor: calibration errors
56 *
57 * Protected by the timekeeping locks.
58 */
59struct ntp_data {
60 unsigned long tick_usec;
61 u64 tick_length;
62 u64 tick_length_base;
63 int time_state;
64 int time_status;
65 s64 time_offset;
66 long time_constant;
67 long time_maxerror;
68 long time_esterror;
69 s64 time_freq;
70 time64_t time_reftime;
71 long time_adjust;
72 s64 ntp_tick_adj;
73 time64_t ntp_next_leap_sec;
74#ifdef CONFIG_NTP_PPS
75 int pps_valid;
76 long pps_tf[3];
77 long pps_jitter;
78 struct timespec64 pps_fbase;
79 int pps_shift;
80 int pps_intcnt;
81 s64 pps_freq;
82 long pps_stabil;
83 long pps_calcnt;
84 long pps_jitcnt;
85 long pps_stbcnt;
86 long pps_errcnt;
87#endif
88};
89
90static struct ntp_data tk_ntp_data[TIMEKEEPERS_MAX] = {
91 [ 0 ... TIMEKEEPERS_MAX - 1 ] = {
92 .tick_usec = USER_TICK_USEC,
93 .time_state = TIME_OK,
94 .time_status = STA_UNSYNC,
95 .time_constant = 2,
96 .time_maxerror = NTP_PHASE_LIMIT,
97 .time_esterror = NTP_PHASE_LIMIT,
98 .ntp_next_leap_sec = TIME64_MAX,
99 },
100};
101
102#define SECS_PER_DAY 86400
103#define MAX_TICKADJ 500LL /* usecs */
104#define MAX_TICKADJ_SCALED \
105 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
106#define MAX_TAI_OFFSET 100000
107
108#ifdef CONFIG_NTP_PPS
109
110/*
111 * The following variables are used when a pulse-per-second (PPS) signal
112 * is available. They establish the engineering parameters of the clock
113 * discipline loop when controlled by the PPS signal.
114 */
115#define PPS_VALID 10 /* PPS signal watchdog max (s) */
116#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
117#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
118#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
119#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
120 increase pps_shift or consecutive bad
121 intervals to decrease it */
122#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
123
124/*
125 * PPS kernel consumer compensates the whole phase error immediately.
126 * Otherwise, reduce the offset by a fixed factor times the time constant.
127 */
128static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
129{
130 if (ntpdata->time_status & STA_PPSTIME && ntpdata->time_status & STA_PPSSIGNAL)
131 return offset;
132 else
133 return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
134}
135
136static inline void pps_reset_freq_interval(struct ntp_data *ntpdata)
137{
138 /* The PPS calibration interval may end surprisingly early */
139 ntpdata->pps_shift = PPS_INTMIN;
140 ntpdata->pps_intcnt = 0;
141}
142
143/**
144 * pps_clear - Clears the PPS state variables
145 * @ntpdata: Pointer to ntp data
146 */
147static inline void pps_clear(struct ntp_data *ntpdata)
148{
149 pps_reset_freq_interval(ntpdata);
150 ntpdata->pps_tf[0] = 0;
151 ntpdata->pps_tf[1] = 0;
152 ntpdata->pps_tf[2] = 0;
153 ntpdata->pps_fbase.tv_sec = ntpdata->pps_fbase.tv_nsec = 0;
154 ntpdata->pps_freq = 0;
155}
156
157/*
158 * Decrease pps_valid to indicate that another second has passed since the
159 * last PPS signal. When it reaches 0, indicate that PPS signal is missing.
160 */
161static inline void pps_dec_valid(struct ntp_data *ntpdata)
162{
163 if (ntpdata->pps_valid > 0) {
164 ntpdata->pps_valid--;
165 } else {
166 ntpdata->time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
167 STA_PPSWANDER | STA_PPSERROR);
168 pps_clear(ntpdata);
169 }
170}
171
172static inline void pps_set_freq(struct ntp_data *ntpdata)
173{
174 ntpdata->pps_freq = ntpdata->time_freq;
175}
176
177static inline bool is_error_status(int status)
178{
179 return (status & (STA_UNSYNC|STA_CLOCKERR))
180 /*
181 * PPS signal lost when either PPS time or PPS frequency
182 * synchronization requested
183 */
184 || ((status & (STA_PPSFREQ|STA_PPSTIME))
185 && !(status & STA_PPSSIGNAL))
186 /*
187 * PPS jitter exceeded when PPS time synchronization
188 * requested
189 */
190 || ((status & (STA_PPSTIME|STA_PPSJITTER))
191 == (STA_PPSTIME|STA_PPSJITTER))
192 /*
193 * PPS wander exceeded or calibration error when PPS
194 * frequency synchronization requested
195 */
196 || ((status & STA_PPSFREQ)
197 && (status & (STA_PPSWANDER|STA_PPSERROR)));
198}
199
200static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
201{
202 txc->ppsfreq = shift_right((ntpdata->pps_freq >> PPM_SCALE_INV_SHIFT) *
203 PPM_SCALE_INV, NTP_SCALE_SHIFT);
204 txc->jitter = ntpdata->pps_jitter;
205 if (!(ntpdata->time_status & STA_NANO))
206 txc->jitter = ntpdata->pps_jitter / NSEC_PER_USEC;
207 txc->shift = ntpdata->pps_shift;
208 txc->stabil = ntpdata->pps_stabil;
209 txc->jitcnt = ntpdata->pps_jitcnt;
210 txc->calcnt = ntpdata->pps_calcnt;
211 txc->errcnt = ntpdata->pps_errcnt;
212 txc->stbcnt = ntpdata->pps_stbcnt;
213}
214
215#else /* !CONFIG_NTP_PPS */
216
217static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
218{
219 return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
220}
221
222static inline void pps_reset_freq_interval(struct ntp_data *ntpdata) {}
223static inline void pps_clear(struct ntp_data *ntpdata) {}
224static inline void pps_dec_valid(struct ntp_data *ntpdata) {}
225static inline void pps_set_freq(struct ntp_data *ntpdata) {}
226
227static inline bool is_error_status(int status)
228{
229 return status & (STA_UNSYNC|STA_CLOCKERR);
230}
231
232static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
233{
234 /* PPS is not implemented, so these are zero */
235 txc->ppsfreq = 0;
236 txc->jitter = 0;
237 txc->shift = 0;
238 txc->stabil = 0;
239 txc->jitcnt = 0;
240 txc->calcnt = 0;
241 txc->errcnt = 0;
242 txc->stbcnt = 0;
243}
244
245#endif /* CONFIG_NTP_PPS */
246
247/*
248 * Update tick_length and tick_length_base, based on tick_usec, ntp_tick_adj and
249 * time_freq:
250 */
251static void ntp_update_frequency(struct ntp_data *ntpdata)
252{
253 u64 second_length, new_base, tick_usec = (u64)ntpdata->tick_usec;
254
255 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << NTP_SCALE_SHIFT;
256
257 second_length += ntpdata->ntp_tick_adj;
258 second_length += ntpdata->time_freq;
259
260 new_base = div_u64(dividend: second_length, NTP_INTERVAL_FREQ);
261
262 /*
263 * Don't wait for the next second_overflow, apply the change to the
264 * tick length immediately:
265 */
266 ntpdata->tick_length += new_base - ntpdata->tick_length_base;
267 ntpdata->tick_length_base = new_base;
268}
269
270static inline s64 ntp_update_offset_fll(struct ntp_data *ntpdata, s64 offset64, long secs)
271{
272 ntpdata->time_status &= ~STA_MODE;
273
274 if (secs < MINSEC)
275 return 0;
276
277 if (!(ntpdata->time_status & STA_FLL) && (secs <= MAXSEC))
278 return 0;
279
280 ntpdata->time_status |= STA_MODE;
281
282 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
283}
284
285static void ntp_update_offset(struct ntp_data *ntpdata, long offset)
286{
287 s64 freq_adj, offset64;
288 long secs, real_secs;
289
290 if (!(ntpdata->time_status & STA_PLL))
291 return;
292
293 if (!(ntpdata->time_status & STA_NANO)) {
294 /* Make sure the multiplication below won't overflow */
295 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
296 offset *= NSEC_PER_USEC;
297 }
298
299 /* Scale the phase adjustment and clamp to the operating range. */
300 offset = clamp(offset, -MAXPHASE, MAXPHASE);
301
302 /*
303 * Select how the frequency is to be controlled
304 * and in which mode (PLL or FLL).
305 */
306 real_secs = ktime_get_ntp_seconds(id: ntpdata - tk_ntp_data);
307 secs = (long)(real_secs - ntpdata->time_reftime);
308 if (unlikely(ntpdata->time_status & STA_FREQHOLD))
309 secs = 0;
310
311 ntpdata->time_reftime = real_secs;
312
313 offset64 = offset;
314 freq_adj = ntp_update_offset_fll(ntpdata, offset64, secs);
315
316 /*
317 * Clamp update interval to reduce PLL gain with low
318 * sampling rate (e.g. intermittent network connection)
319 * to avoid instability.
320 */
321 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + ntpdata->time_constant)))
322 secs = 1 << (SHIFT_PLL + 1 + ntpdata->time_constant);
323
324 freq_adj += (offset64 * secs) <<
325 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + ntpdata->time_constant));
326
327 freq_adj = min(freq_adj + ntpdata->time_freq, MAXFREQ_SCALED);
328
329 ntpdata->time_freq = max(freq_adj, -MAXFREQ_SCALED);
330
331 ntpdata->time_offset = div_s64(dividend: offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
332}
333
334static void __ntp_clear(struct ntp_data *ntpdata)
335{
336 /* Stop active adjtime() */
337 ntpdata->time_adjust = 0;
338 ntpdata->time_status |= STA_UNSYNC;
339 ntpdata->time_maxerror = NTP_PHASE_LIMIT;
340 ntpdata->time_esterror = NTP_PHASE_LIMIT;
341
342 ntp_update_frequency(ntpdata);
343
344 ntpdata->tick_length = ntpdata->tick_length_base;
345 ntpdata->time_offset = 0;
346
347 ntpdata->ntp_next_leap_sec = TIME64_MAX;
348 /* Clear PPS state variables */
349 pps_clear(ntpdata);
350}
351
352/**
353 * ntp_clear - Clears the NTP state variables
354 * @tkid: Timekeeper ID to be able to select proper ntp data array member
355 */
356void ntp_clear(unsigned int tkid)
357{
358 __ntp_clear(ntpdata: &tk_ntp_data[tkid]);
359}
360
361
362u64 ntp_tick_length(unsigned int tkid)
363{
364 return tk_ntp_data[tkid].tick_length;
365}
366
367/**
368 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
369 * @tkid: Timekeeper ID
370 *
371 * Returns: For @tkid == TIMEKEEPER_CORE this provides the time of the next
372 * leap second against CLOCK_REALTIME in a ktime_t format if a
373 * leap second is pending. KTIME_MAX otherwise.
374 */
375ktime_t ntp_get_next_leap(unsigned int tkid)
376{
377 struct ntp_data *ntpdata = &tk_ntp_data[TIMEKEEPER_CORE];
378
379 if (tkid != TIMEKEEPER_CORE)
380 return KTIME_MAX;
381
382 if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS))
383 return ktime_set(secs: ntpdata->ntp_next_leap_sec, nsecs: 0);
384
385 return KTIME_MAX;
386}
387
388/*
389 * This routine handles the overflow of the microsecond field
390 *
391 * The tricky bits of code to handle the accurate clock support
392 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
393 * They were originally developed for SUN and DEC kernels.
394 * All the kudos should go to Dave for this stuff.
395 *
396 * Also handles leap second processing, and returns leap offset
397 */
398int second_overflow(unsigned int tkid, time64_t secs)
399{
400 struct ntp_data *ntpdata = &tk_ntp_data[tkid];
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 (ntpdata->time_state) {
411 case TIME_OK:
412 if (ntpdata->time_status & STA_INS) {
413 ntpdata->time_state = TIME_INS;
414 div_s64_rem(dividend: secs, SECS_PER_DAY, remainder: &rem);
415 ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
416 } else if (ntpdata->time_status & STA_DEL) {
417 ntpdata->time_state = TIME_DEL;
418 div_s64_rem(dividend: secs + 1, SECS_PER_DAY, remainder: &rem);
419 ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
420 }
421 break;
422 case TIME_INS:
423 if (!(ntpdata->time_status & STA_INS)) {
424 ntpdata->ntp_next_leap_sec = TIME64_MAX;
425 ntpdata->time_state = TIME_OK;
426 } else if (secs == ntpdata->ntp_next_leap_sec) {
427 leap = -1;
428 ntpdata->time_state = TIME_OOP;
429 pr_notice("Clock: inserting leap second 23:59:60 UTC\n");
430 }
431 break;
432 case TIME_DEL:
433 if (!(ntpdata->time_status & STA_DEL)) {
434 ntpdata->ntp_next_leap_sec = TIME64_MAX;
435 ntpdata->time_state = TIME_OK;
436 } else if (secs == ntpdata->ntp_next_leap_sec) {
437 leap = 1;
438 ntpdata->ntp_next_leap_sec = TIME64_MAX;
439 ntpdata->time_state = TIME_WAIT;
440 pr_notice("Clock: deleting leap second 23:59:59 UTC\n");
441 }
442 break;
443 case TIME_OOP:
444 ntpdata->ntp_next_leap_sec = TIME64_MAX;
445 ntpdata->time_state = TIME_WAIT;
446 break;
447 case TIME_WAIT:
448 if (!(ntpdata->time_status & (STA_INS | STA_DEL)))
449 ntpdata->time_state = TIME_OK;
450 break;
451 }
452
453 /* Bump the maxerror field */
454 ntpdata->time_maxerror += MAXFREQ / NSEC_PER_USEC;
455 if (ntpdata->time_maxerror > NTP_PHASE_LIMIT) {
456 ntpdata->time_maxerror = NTP_PHASE_LIMIT;
457 ntpdata->time_status |= STA_UNSYNC;
458 }
459
460 /* Compute the phase adjustment for the next second */
461 ntpdata->tick_length = ntpdata->tick_length_base;
462
463 delta = ntp_offset_chunk(ntpdata, offset: ntpdata->time_offset);
464 ntpdata->time_offset -= delta;
465 ntpdata->tick_length += delta;
466
467 /* Check PPS signal */
468 pps_dec_valid(ntpdata);
469
470 if (!ntpdata->time_adjust)
471 goto out;
472
473 if (ntpdata->time_adjust > MAX_TICKADJ) {
474 ntpdata->time_adjust -= MAX_TICKADJ;
475 ntpdata->tick_length += MAX_TICKADJ_SCALED;
476 goto out;
477 }
478
479 if (ntpdata->time_adjust < -MAX_TICKADJ) {
480 ntpdata->time_adjust += MAX_TICKADJ;
481 ntpdata->tick_length -= MAX_TICKADJ_SCALED;
482 goto out;
483 }
484
485 ntpdata->tick_length += (s64)(ntpdata->time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
486 << NTP_SCALE_SHIFT;
487 ntpdata->time_adjust = 0;
488
489out:
490 return leap;
491}
492
493#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
494static void sync_hw_clock(struct work_struct *work);
495static DECLARE_WORK(sync_work, sync_hw_clock);
496static struct hrtimer sync_hrtimer;
497#define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC)
498
499static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
500{
501 queue_work(wq: system_freezable_power_efficient_wq, work: &sync_work);
502
503 return HRTIMER_NORESTART;
504}
505
506static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry)
507{
508 ktime_t exp = ktime_set(secs: ktime_get_real_seconds(), nsecs: 0);
509
510 if (retry)
511 exp = ktime_add_ns(exp, 2ULL * NSEC_PER_SEC - offset_nsec);
512 else
513 exp = ktime_add_ns(exp, SYNC_PERIOD_NS - offset_nsec);
514
515 hrtimer_start(timer: &sync_hrtimer, tim: exp, mode: HRTIMER_MODE_ABS);
516}
517
518/*
519 * Check whether @now is correct versus the required time to update the RTC
520 * and calculate the value which needs to be written to the RTC so that the
521 * next seconds increment of the RTC after the write is aligned with the next
522 * seconds increment of clock REALTIME.
523 *
524 * tsched t1 write(t2.tv_sec - 1sec)) t2 RTC increments seconds
525 *
526 * t2.tv_nsec == 0
527 * tsched = t2 - set_offset_nsec
528 * newval = t2 - NSEC_PER_SEC
529 *
530 * ==> neval = tsched + set_offset_nsec - NSEC_PER_SEC
531 *
532 * As the execution of this code is not guaranteed to happen exactly at
533 * tsched this allows it to happen within a fuzzy region:
534 *
535 * abs(now - tsched) < FUZZ
536 *
537 * If @now is not inside the allowed window the function returns false.
538 */
539static inline bool rtc_tv_nsec_ok(unsigned long set_offset_nsec,
540 struct timespec64 *to_set,
541 const struct timespec64 *now)
542{
543 /* Allowed error in tv_nsec, arbitrarily set to 5 jiffies in ns. */
544 const unsigned long TIME_SET_NSEC_FUZZ = TICK_NSEC * 5;
545 struct timespec64 delay = {.tv_sec = -1,
546 .tv_nsec = set_offset_nsec};
547
548 *to_set = timespec64_add(lhs: *now, rhs: delay);
549
550 if (to_set->tv_nsec < TIME_SET_NSEC_FUZZ) {
551 to_set->tv_nsec = 0;
552 return true;
553 }
554
555 if (to_set->tv_nsec > NSEC_PER_SEC - TIME_SET_NSEC_FUZZ) {
556 to_set->tv_sec++;
557 to_set->tv_nsec = 0;
558 return true;
559 }
560 return false;
561}
562
563#ifdef CONFIG_GENERIC_CMOS_UPDATE
564int __weak update_persistent_clock64(struct timespec64 now64)
565{
566 return -ENODEV;
567}
568#else
569static inline int update_persistent_clock64(struct timespec64 now64)
570{
571 return -ENODEV;
572}
573#endif
574
575#ifdef CONFIG_RTC_SYSTOHC
576/* Save NTP synchronized time to the RTC */
577static int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
578{
579 struct rtc_device *rtc;
580 struct rtc_time tm;
581 int err = -ENODEV;
582
583 rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
584 if (!rtc)
585 return -ENODEV;
586
587 if (!rtc->ops || !rtc->ops->set_time)
588 goto out_close;
589
590 /* First call might not have the correct offset */
591 if (*offset_nsec == rtc->set_offset_nsec) {
592 rtc_time64_to_tm(time: to_set->tv_sec, tm: &tm);
593 err = rtc_set_time(rtc, tm: &tm);
594 } else {
595 /* Store the update offset and let the caller try again */
596 *offset_nsec = rtc->set_offset_nsec;
597 err = -EAGAIN;
598 }
599out_close:
600 rtc_class_close(rtc);
601 return err;
602}
603#else
604static inline int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
605{
606 return -ENODEV;
607}
608#endif
609
610/**
611 * ntp_synced - Tells whether the NTP status is not UNSYNC
612 * Returns: true if not UNSYNC, false otherwise
613 */
614static inline bool ntp_synced(void)
615{
616 return !(tk_ntp_data[TIMEKEEPER_CORE].time_status & STA_UNSYNC);
617}
618
619/*
620 * If we have an externally synchronized Linux clock, then update RTC clock
621 * accordingly every ~11 minutes. Generally RTCs can only store second
622 * precision, but many RTCs will adjust the phase of their second tick to
623 * match the moment of update. This infrastructure arranges to call to the RTC
624 * set at the correct moment to phase synchronize the RTC second tick over
625 * with the kernel clock.
626 */
627static void sync_hw_clock(struct work_struct *work)
628{
629 /*
630 * The default synchronization offset is 500ms for the deprecated
631 * update_persistent_clock64() under the assumption that it uses
632 * the infamous CMOS clock (MC146818).
633 */
634 static unsigned long offset_nsec = NSEC_PER_SEC / 2;
635 struct timespec64 now, to_set;
636 int res = -EAGAIN;
637
638 /*
639 * Don't update if STA_UNSYNC is set and if ntp_notify_cmos_timer()
640 * managed to schedule the work between the timer firing and the
641 * work being able to rearm the timer. Wait for the timer to expire.
642 */
643 if (!ntp_synced() || hrtimer_is_queued(timer: &sync_hrtimer))
644 return;
645
646 ktime_get_real_ts64(tv: &now);
647 /* If @now is not in the allowed window, try again */
648 if (!rtc_tv_nsec_ok(set_offset_nsec: offset_nsec, to_set: &to_set, now: &now))
649 goto rearm;
650
651 /* Take timezone adjusted RTCs into account */
652 if (persistent_clock_is_local)
653 to_set.tv_sec -= (sys_tz.tz_minuteswest * 60);
654
655 /* Try the legacy RTC first. */
656 res = update_persistent_clock64(now64: to_set);
657 if (res != -ENODEV)
658 goto rearm;
659
660 /* Try the RTC class */
661 res = update_rtc(to_set: &to_set, offset_nsec: &offset_nsec);
662 if (res == -ENODEV)
663 return;
664rearm:
665 sched_sync_hw_clock(offset_nsec, retry: res != 0);
666}
667
668void ntp_notify_cmos_timer(bool offset_set)
669{
670 /*
671 * If the time jumped (using ADJ_SETOFFSET) cancels sync timer,
672 * which may have been running if the time was synchronized
673 * prior to the ADJ_SETOFFSET call.
674 */
675 if (offset_set)
676 hrtimer_cancel(timer: &sync_hrtimer);
677
678 /*
679 * When the work is currently executed but has not yet the timer
680 * rearmed this queues the work immediately again. No big issue,
681 * just a pointless work scheduled.
682 */
683 if (ntp_synced() && !hrtimer_is_queued(timer: &sync_hrtimer))
684 queue_work(wq: system_freezable_power_efficient_wq, work: &sync_work);
685}
686
687static void __init ntp_init_cmos_sync(void)
688{
689 hrtimer_setup(timer: &sync_hrtimer, function: sync_timer_callback, CLOCK_REALTIME, mode: HRTIMER_MODE_ABS);
690}
691#else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
692static inline void __init ntp_init_cmos_sync(void) { }
693#endif /* !CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
694
695/*
696 * Propagate a new txc->status value into the NTP state:
697 */
698static inline void process_adj_status(struct ntp_data *ntpdata, const struct __kernel_timex *txc)
699{
700 if ((ntpdata->time_status & STA_PLL) && !(txc->status & STA_PLL)) {
701 ntpdata->time_state = TIME_OK;
702 ntpdata->time_status = STA_UNSYNC;
703 ntpdata->ntp_next_leap_sec = TIME64_MAX;
704 /* Restart PPS frequency calibration */
705 pps_reset_freq_interval(ntpdata);
706 }
707
708 /*
709 * If we turn on PLL adjustments then reset the
710 * reference time to current time.
711 */
712 if (!(ntpdata->time_status & STA_PLL) && (txc->status & STA_PLL))
713 ntpdata->time_reftime = ktime_get_ntp_seconds(id: ntpdata - tk_ntp_data);
714
715 /* only set allowed bits */
716 ntpdata->time_status &= STA_RONLY;
717 ntpdata->time_status |= txc->status & ~STA_RONLY;
718}
719
720static inline void process_adjtimex_modes(struct ntp_data *ntpdata, const struct __kernel_timex *txc,
721 s32 *time_tai)
722{
723 if (txc->modes & ADJ_STATUS)
724 process_adj_status(ntpdata, txc);
725
726 if (txc->modes & ADJ_NANO)
727 ntpdata->time_status |= STA_NANO;
728
729 if (txc->modes & ADJ_MICRO)
730 ntpdata->time_status &= ~STA_NANO;
731
732 if (txc->modes & ADJ_FREQUENCY) {
733 ntpdata->time_freq = txc->freq * PPM_SCALE;
734 ntpdata->time_freq = min(ntpdata->time_freq, MAXFREQ_SCALED);
735 ntpdata->time_freq = max(ntpdata->time_freq, -MAXFREQ_SCALED);
736 /* Update pps_freq */
737 pps_set_freq(ntpdata);
738 }
739
740 if (txc->modes & ADJ_MAXERROR)
741 ntpdata->time_maxerror = clamp(txc->maxerror, 0, NTP_PHASE_LIMIT);
742
743 if (txc->modes & ADJ_ESTERROR)
744 ntpdata->time_esterror = clamp(txc->esterror, 0, NTP_PHASE_LIMIT);
745
746 if (txc->modes & ADJ_TIMECONST) {
747 ntpdata->time_constant = clamp(txc->constant, 0, MAXTC);
748 if (!(ntpdata->time_status & STA_NANO))
749 ntpdata->time_constant += 4;
750 ntpdata->time_constant = clamp(ntpdata->time_constant, 0, MAXTC);
751 }
752
753 if (txc->modes & ADJ_TAI && txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
754 *time_tai = txc->constant;
755
756 if (txc->modes & ADJ_OFFSET)
757 ntp_update_offset(ntpdata, offset: txc->offset);
758
759 if (txc->modes & ADJ_TICK)
760 ntpdata->tick_usec = txc->tick;
761
762 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
763 ntp_update_frequency(ntpdata);
764}
765
766/*
767 * adjtimex() mainly allows reading (and writing, if superuser) of
768 * kernel time-keeping variables. used by xntpd.
769 */
770int ntp_adjtimex(unsigned int tkid, struct __kernel_timex *txc, const struct timespec64 *ts,
771 s32 *time_tai, struct audit_ntp_data *ad)
772{
773 struct ntp_data *ntpdata = &tk_ntp_data[tkid];
774 int result;
775
776 if (txc->modes & ADJ_ADJTIME) {
777 long save_adjust = ntpdata->time_adjust;
778
779 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
780 /* adjtime() is independent from ntp_adjtime() */
781 ntpdata->time_adjust = txc->offset;
782 ntp_update_frequency(ntpdata);
783
784 audit_ntp_set_old(ad, type: AUDIT_NTP_ADJUST, val: save_adjust);
785 audit_ntp_set_new(ad, type: AUDIT_NTP_ADJUST, val: ntpdata->time_adjust);
786 }
787 txc->offset = save_adjust;
788 } else {
789 /* If there are input parameters, then process them: */
790 if (txc->modes) {
791 audit_ntp_set_old(ad, type: AUDIT_NTP_OFFSET, val: ntpdata->time_offset);
792 audit_ntp_set_old(ad, type: AUDIT_NTP_FREQ, val: ntpdata->time_freq);
793 audit_ntp_set_old(ad, type: AUDIT_NTP_STATUS, val: ntpdata->time_status);
794 audit_ntp_set_old(ad, type: AUDIT_NTP_TAI, val: *time_tai);
795 audit_ntp_set_old(ad, type: AUDIT_NTP_TICK, val: ntpdata->tick_usec);
796
797 process_adjtimex_modes(ntpdata, txc, time_tai);
798
799 audit_ntp_set_new(ad, type: AUDIT_NTP_OFFSET, val: ntpdata->time_offset);
800 audit_ntp_set_new(ad, type: AUDIT_NTP_FREQ, val: ntpdata->time_freq);
801 audit_ntp_set_new(ad, type: AUDIT_NTP_STATUS, val: ntpdata->time_status);
802 audit_ntp_set_new(ad, type: AUDIT_NTP_TAI, val: *time_tai);
803 audit_ntp_set_new(ad, type: AUDIT_NTP_TICK, val: ntpdata->tick_usec);
804 }
805
806 txc->offset = shift_right(ntpdata->time_offset * NTP_INTERVAL_FREQ, NTP_SCALE_SHIFT);
807 if (!(ntpdata->time_status & STA_NANO))
808 txc->offset = div_s64(dividend: txc->offset, NSEC_PER_USEC);
809 }
810
811 result = ntpdata->time_state;
812 if (is_error_status(status: ntpdata->time_status))
813 result = TIME_ERROR;
814
815 txc->freq = shift_right((ntpdata->time_freq >> PPM_SCALE_INV_SHIFT) *
816 PPM_SCALE_INV, NTP_SCALE_SHIFT);
817 txc->maxerror = ntpdata->time_maxerror;
818 txc->esterror = ntpdata->time_esterror;
819 txc->status = ntpdata->time_status;
820 txc->constant = ntpdata->time_constant;
821 txc->precision = 1;
822 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
823 txc->tick = ntpdata->tick_usec;
824 txc->tai = *time_tai;
825
826 /* Fill PPS status fields */
827 pps_fill_timex(ntpdata, txc);
828
829 txc->time.tv_sec = ts->tv_sec;
830 txc->time.tv_usec = ts->tv_nsec;
831 if (!(ntpdata->time_status & STA_NANO))
832 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;
833
834 /* Handle leapsec adjustments */
835 if (unlikely(ts->tv_sec >= ntpdata->ntp_next_leap_sec)) {
836 if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS)) {
837 result = TIME_OOP;
838 txc->tai++;
839 txc->time.tv_sec--;
840 }
841 if ((ntpdata->time_state == TIME_DEL) && (ntpdata->time_status & STA_DEL)) {
842 result = TIME_WAIT;
843 txc->tai--;
844 txc->time.tv_sec++;
845 }
846 if ((ntpdata->time_state == TIME_OOP) && (ts->tv_sec == ntpdata->ntp_next_leap_sec))
847 result = TIME_WAIT;
848 }
849
850 return result;
851}
852
853#ifdef CONFIG_NTP_PPS
854
855/*
856 * struct pps_normtime is basically a struct timespec, but it is
857 * semantically different (and it is the reason why it was invented):
858 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
859 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC)
860 */
861struct pps_normtime {
862 s64 sec; /* seconds */
863 long nsec; /* nanoseconds */
864};
865
866/*
867 * Normalize the timestamp so that nsec is in the
868 * [ -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval
869 */
870static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
871{
872 struct pps_normtime norm = {
873 .sec = ts.tv_sec,
874 .nsec = ts.tv_nsec
875 };
876
877 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
878 norm.nsec -= NSEC_PER_SEC;
879 norm.sec++;
880 }
881
882 return norm;
883}
884
885/* Get current phase correction and jitter */
886static inline long pps_phase_filter_get(struct ntp_data *ntpdata, long *jitter)
887{
888 *jitter = ntpdata->pps_tf[0] - ntpdata->pps_tf[1];
889 if (*jitter < 0)
890 *jitter = -*jitter;
891
892 /* TODO: test various filters */
893 return ntpdata->pps_tf[0];
894}
895
896/* Add the sample to the phase filter */
897static inline void pps_phase_filter_add(struct ntp_data *ntpdata, long err)
898{
899 ntpdata->pps_tf[2] = ntpdata->pps_tf[1];
900 ntpdata->pps_tf[1] = ntpdata->pps_tf[0];
901 ntpdata->pps_tf[0] = err;
902}
903
904/*
905 * Decrease frequency calibration interval length. It is halved after four
906 * consecutive unstable intervals.
907 */
908static inline void pps_dec_freq_interval(struct ntp_data *ntpdata)
909{
910 if (--ntpdata->pps_intcnt <= -PPS_INTCOUNT) {
911 ntpdata->pps_intcnt = -PPS_INTCOUNT;
912 if (ntpdata->pps_shift > PPS_INTMIN) {
913 ntpdata->pps_shift--;
914 ntpdata->pps_intcnt = 0;
915 }
916 }
917}
918
919/*
920 * Increase frequency calibration interval length. It is doubled after
921 * four consecutive stable intervals.
922 */
923static inline void pps_inc_freq_interval(struct ntp_data *ntpdata)
924{
925 if (++ntpdata->pps_intcnt >= PPS_INTCOUNT) {
926 ntpdata->pps_intcnt = PPS_INTCOUNT;
927 if (ntpdata->pps_shift < PPS_INTMAX) {
928 ntpdata->pps_shift++;
929 ntpdata->pps_intcnt = 0;
930 }
931 }
932}
933
934/*
935 * Update clock frequency based on MONOTONIC_RAW clock PPS signal
936 * timestamps
937 *
938 * At the end of the calibration interval the difference between the
939 * first and last MONOTONIC_RAW clock timestamps divided by the length
940 * of the interval becomes the frequency update. If the interval was
941 * too long, the data are discarded.
942 * Returns the difference between old and new frequency values.
943 */
944static long hardpps_update_freq(struct ntp_data *ntpdata, struct pps_normtime freq_norm)
945{
946 long delta, delta_mod;
947 s64 ftemp;
948
949 /* Check if the frequency interval was too long */
950 if (freq_norm.sec > (2 << ntpdata->pps_shift)) {
951 ntpdata->time_status |= STA_PPSERROR;
952 ntpdata->pps_errcnt++;
953 pps_dec_freq_interval(ntpdata);
954 printk_deferred(KERN_ERR "hardpps: PPSERROR: interval too long - %lld s\n",
955 freq_norm.sec);
956 return 0;
957 }
958
959 /*
960 * Here the raw frequency offset and wander (stability) is
961 * calculated. If the wander is less than the wander threshold the
962 * interval is increased; otherwise it is decreased.
963 */
964 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
965 freq_norm.sec);
966 delta = shift_right(ftemp - ntpdata->pps_freq, NTP_SCALE_SHIFT);
967 ntpdata->pps_freq = ftemp;
968 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
969 printk_deferred(KERN_WARNING "hardpps: PPSWANDER: change=%ld\n", delta);
970 ntpdata->time_status |= STA_PPSWANDER;
971 ntpdata->pps_stbcnt++;
972 pps_dec_freq_interval(ntpdata);
973 } else {
974 /* Good sample */
975 pps_inc_freq_interval(ntpdata);
976 }
977
978 /*
979 * The stability metric is calculated as the average of recent
980 * frequency changes, but is used only for performance monitoring
981 */
982 delta_mod = delta;
983 if (delta_mod < 0)
984 delta_mod = -delta_mod;
985 ntpdata->pps_stabil += (div_s64(((s64)delta_mod) << (NTP_SCALE_SHIFT - SHIFT_USEC),
986 NSEC_PER_USEC) - ntpdata->pps_stabil) >> PPS_INTMIN;
987
988 /* If enabled, the system clock frequency is updated */
989 if ((ntpdata->time_status & STA_PPSFREQ) && !(ntpdata->time_status & STA_FREQHOLD)) {
990 ntpdata->time_freq = ntpdata->pps_freq;
991 ntp_update_frequency(ntpdata);
992 }
993
994 return delta;
995}
996
997/* Correct REALTIME clock phase error against PPS signal */
998static void hardpps_update_phase(struct ntp_data *ntpdata, long error)
999{
1000 long correction = -error;
1001 long jitter;
1002
1003 /* Add the sample to the median filter */
1004 pps_phase_filter_add(ntpdata, correction);
1005 correction = pps_phase_filter_get(ntpdata, &jitter);
1006
1007 /*
1008 * Nominal jitter is due to PPS signal noise. If it exceeds the
1009 * threshold, the sample is discarded; otherwise, if so enabled,
1010 * the time offset is updated.
1011 */
1012 if (jitter > (ntpdata->pps_jitter << PPS_POPCORN)) {
1013 printk_deferred(KERN_WARNING "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
1014 jitter, (ntpdata->pps_jitter << PPS_POPCORN));
1015 ntpdata->time_status |= STA_PPSJITTER;
1016 ntpdata->pps_jitcnt++;
1017 } else if (ntpdata->time_status & STA_PPSTIME) {
1018 /* Correct the time using the phase offset */
1019 ntpdata->time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
1020 NTP_INTERVAL_FREQ);
1021 /* Cancel running adjtime() */
1022 ntpdata->time_adjust = 0;
1023 }
1024 /* Update jitter */
1025 ntpdata->pps_jitter += (jitter - ntpdata->pps_jitter) >> PPS_INTMIN;
1026}
1027
1028/*
1029 * __hardpps() - discipline CPU clock oscillator to external PPS signal
1030 *
1031 * This routine is called at each PPS signal arrival in order to
1032 * discipline the CPU clock oscillator to the PPS signal. It takes two
1033 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
1034 * is used to correct clock phase error and the latter is used to
1035 * correct the frequency.
1036 *
1037 * This code is based on David Mills's reference nanokernel
1038 * implementation. It was mostly rewritten but keeps the same idea.
1039 */
1040void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
1041{
1042 struct ntp_data *ntpdata = &tk_ntp_data[TIMEKEEPER_CORE];
1043 struct pps_normtime pts_norm, freq_norm;
1044
1045 pts_norm = pps_normalize_ts(*phase_ts);
1046
1047 /* Clear the error bits, they will be set again if needed */
1048 ntpdata->time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
1049
1050 /* indicate signal presence */
1051 ntpdata->time_status |= STA_PPSSIGNAL;
1052 ntpdata->pps_valid = PPS_VALID;
1053
1054 /*
1055 * When called for the first time, just start the frequency
1056 * interval
1057 */
1058 if (unlikely(ntpdata->pps_fbase.tv_sec == 0)) {
1059 ntpdata->pps_fbase = *raw_ts;
1060 return;
1061 }
1062
1063 /* Ok, now we have a base for frequency calculation */
1064 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, ntpdata->pps_fbase));
1065
1066 /*
1067 * Check that the signal is in the range
1068 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it
1069 */
1070 if ((freq_norm.sec == 0) || (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1071 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1072 ntpdata->time_status |= STA_PPSJITTER;
1073 /* Restart the frequency calibration interval */
1074 ntpdata->pps_fbase = *raw_ts;
1075 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1076 return;
1077 }
1078
1079 /* Signal is ok. Check if the current frequency interval is finished */
1080 if (freq_norm.sec >= (1 << ntpdata->pps_shift)) {
1081 ntpdata->pps_calcnt++;
1082 /* Restart the frequency calibration interval */
1083 ntpdata->pps_fbase = *raw_ts;
1084 hardpps_update_freq(ntpdata, freq_norm);
1085 }
1086
1087 hardpps_update_phase(ntpdata, pts_norm.nsec);
1088
1089}
1090#endif /* CONFIG_NTP_PPS */
1091
1092static int __init ntp_tick_adj_setup(char *str)
1093{
1094 int rc = kstrtos64(s: str, base: 0, res: &tk_ntp_data[TIMEKEEPER_CORE].ntp_tick_adj);
1095 if (rc)
1096 return rc;
1097
1098 tk_ntp_data[TIMEKEEPER_CORE].ntp_tick_adj <<= NTP_SCALE_SHIFT;
1099 return 1;
1100}
1101__setup("ntp_tick_adj=", ntp_tick_adj_setup);
1102
1103void __init ntp_init(void)
1104{
1105 for (int id = 0; id < TIMEKEEPERS_MAX; id++)
1106 __ntp_clear(ntpdata: tk_ntp_data + id);
1107 ntp_init_cmos_sync();
1108}
1109

source code of linux/kernel/time/ntp.c