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 * struct ntp_data - Structure holding all NTP related state
27 * @tick_usec: USER_HZ period in microseconds
28 * @tick_length: Adjusted tick length
29 * @tick_length_base: Base value for @tick_length
30 * @time_state: State of the clock synchronization
31 * @time_status: Clock status bits
32 * @time_offset: Time adjustment in nanoseconds
33 * @time_constant: PLL time constant
34 * @time_maxerror: Maximum error in microseconds holding the NTP sync distance
35 * (NTP dispersion + delay / 2)
36 * @time_esterror: Estimated error in microseconds holding NTP dispersion
37 * @time_freq: Frequency offset scaled nsecs/secs
38 * @time_reftime: Time at last adjustment in seconds
39 * @time_adjust: Adjustment value
40 * @ntp_tick_adj: Constant boot-param configurable NTP tick adjustment (upscaled)
41 * @ntp_next_leap_sec: Second value of the next pending leapsecond, or TIME64_MAX if no leap
42 *
43 * @pps_valid: PPS signal watchdog counter
44 * @pps_tf: PPS phase median filter
45 * @pps_jitter: PPS current jitter in nanoseconds
46 * @pps_fbase: PPS beginning of the last freq interval
47 * @pps_shift: PPS current interval duration in seconds (shift value)
48 * @pps_intcnt: PPS interval counter
49 * @pps_freq: PPS frequency offset in scaled ns/s
50 * @pps_stabil: PPS current stability in scaled ns/s
51 * @pps_calcnt: PPS monitor: calibration intervals
52 * @pps_jitcnt: PPS monitor: jitter limit exceeded
53 * @pps_stbcnt: PPS monitor: stability limit exceeded
54 * @pps_errcnt: PPS monitor: calibration errors
55 *
56 * Protected by the timekeeping locks.
57 */
58struct ntp_data {
59 unsigned long tick_usec;
60 u64 tick_length;
61 u64 tick_length_base;
62 int time_state;
63 int time_status;
64 s64 time_offset;
65 long time_constant;
66 long time_maxerror;
67 long time_esterror;
68 s64 time_freq;
69 time64_t time_reftime;
70 long time_adjust;
71 s64 ntp_tick_adj;
72 time64_t ntp_next_leap_sec;
73#ifdef CONFIG_NTP_PPS
74 int pps_valid;
75 long pps_tf[3];
76 long pps_jitter;
77 struct timespec64 pps_fbase;
78 int pps_shift;
79 int pps_intcnt;
80 s64 pps_freq;
81 long pps_stabil;
82 long pps_calcnt;
83 long pps_jitcnt;
84 long pps_stbcnt;
85 long pps_errcnt;
86#endif
87};
88
89static struct ntp_data tk_ntp_data = {
90 .tick_usec = USER_TICK_USEC,
91 .time_state = TIME_OK,
92 .time_status = STA_UNSYNC,
93 .time_constant = 2,
94 .time_maxerror = NTP_PHASE_LIMIT,
95 .time_esterror = NTP_PHASE_LIMIT,
96 .ntp_next_leap_sec = TIME64_MAX,
97};
98
99#define SECS_PER_DAY 86400
100#define MAX_TICKADJ 500LL /* usecs */
101#define MAX_TICKADJ_SCALED \
102 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
103#define MAX_TAI_OFFSET 100000
104
105#ifdef CONFIG_NTP_PPS
106
107/*
108 * The following variables are used when a pulse-per-second (PPS) signal
109 * is available. They establish the engineering parameters of the clock
110 * discipline loop when controlled by the PPS signal.
111 */
112#define PPS_VALID 10 /* PPS signal watchdog max (s) */
113#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
114#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
115#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
116#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
117 increase pps_shift or consecutive bad
118 intervals to decrease it */
119#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
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 */
125static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
126{
127 if (ntpdata->time_status & STA_PPSTIME && ntpdata->time_status & STA_PPSSIGNAL)
128 return offset;
129 else
130 return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
131}
132
133static inline void pps_reset_freq_interval(struct ntp_data *ntpdata)
134{
135 /* The PPS calibration interval may end surprisingly early */
136 ntpdata->pps_shift = PPS_INTMIN;
137 ntpdata->pps_intcnt = 0;
138}
139
140/**
141 * pps_clear - Clears the PPS state variables
142 * @ntpdata: Pointer to ntp data
143 */
144static inline void pps_clear(struct ntp_data *ntpdata)
145{
146 pps_reset_freq_interval(ntpdata);
147 ntpdata->pps_tf[0] = 0;
148 ntpdata->pps_tf[1] = 0;
149 ntpdata->pps_tf[2] = 0;
150 ntpdata->pps_fbase.tv_sec = ntpdata->pps_fbase.tv_nsec = 0;
151 ntpdata->pps_freq = 0;
152}
153
154/*
155 * Decrease pps_valid to indicate that another second has passed since the
156 * last PPS signal. When it reaches 0, indicate that PPS signal is missing.
157 */
158static inline void pps_dec_valid(struct ntp_data *ntpdata)
159{
160 if (ntpdata->pps_valid > 0) {
161 ntpdata->pps_valid--;
162 } else {
163 ntpdata->time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
164 STA_PPSWANDER | STA_PPSERROR);
165 pps_clear(ntpdata);
166 }
167}
168
169static inline void pps_set_freq(struct ntp_data *ntpdata)
170{
171 ntpdata->pps_freq = ntpdata->time_freq;
172}
173
174static inline bool is_error_status(int status)
175{
176 return (status & (STA_UNSYNC|STA_CLOCKERR))
177 /*
178 * PPS signal lost when either PPS time or PPS frequency
179 * synchronization requested
180 */
181 || ((status & (STA_PPSFREQ|STA_PPSTIME))
182 && !(status & STA_PPSSIGNAL))
183 /*
184 * PPS jitter exceeded when PPS time synchronization
185 * requested
186 */
187 || ((status & (STA_PPSTIME|STA_PPSJITTER))
188 == (STA_PPSTIME|STA_PPSJITTER))
189 /*
190 * PPS wander exceeded or calibration error when PPS
191 * frequency synchronization requested
192 */
193 || ((status & STA_PPSFREQ)
194 && (status & (STA_PPSWANDER|STA_PPSERROR)));
195}
196
197static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
198{
199 txc->ppsfreq = shift_right((ntpdata->pps_freq >> PPM_SCALE_INV_SHIFT) *
200 PPM_SCALE_INV, NTP_SCALE_SHIFT);
201 txc->jitter = ntpdata->pps_jitter;
202 if (!(ntpdata->time_status & STA_NANO))
203 txc->jitter = ntpdata->pps_jitter / NSEC_PER_USEC;
204 txc->shift = ntpdata->pps_shift;
205 txc->stabil = ntpdata->pps_stabil;
206 txc->jitcnt = ntpdata->pps_jitcnt;
207 txc->calcnt = ntpdata->pps_calcnt;
208 txc->errcnt = ntpdata->pps_errcnt;
209 txc->stbcnt = ntpdata->pps_stbcnt;
210}
211
212#else /* !CONFIG_NTP_PPS */
213
214static inline s64 ntp_offset_chunk(struct ntp_data *ntpdata, s64 offset)
215{
216 return shift_right(offset, SHIFT_PLL + ntpdata->time_constant);
217}
218
219static inline void pps_reset_freq_interval(struct ntp_data *ntpdata) {}
220static inline void pps_clear(struct ntp_data *ntpdata) {}
221static inline void pps_dec_valid(struct ntp_data *ntpdata) {}
222static inline void pps_set_freq(struct ntp_data *ntpdata) {}
223
224static inline bool is_error_status(int status)
225{
226 return status & (STA_UNSYNC|STA_CLOCKERR);
227}
228
229static inline void pps_fill_timex(struct ntp_data *ntpdata, struct __kernel_timex *txc)
230{
231 /* PPS is not implemented, so these are zero */
232 txc->ppsfreq = 0;
233 txc->jitter = 0;
234 txc->shift = 0;
235 txc->stabil = 0;
236 txc->jitcnt = 0;
237 txc->calcnt = 0;
238 txc->errcnt = 0;
239 txc->stbcnt = 0;
240}
241
242#endif /* CONFIG_NTP_PPS */
243
244/*
245 * Update tick_length and tick_length_base, based on tick_usec, ntp_tick_adj and
246 * time_freq:
247 */
248static void ntp_update_frequency(struct ntp_data *ntpdata)
249{
250 u64 second_length, new_base, tick_usec = (u64)ntpdata->tick_usec;
251
252 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << NTP_SCALE_SHIFT;
253
254 second_length += ntpdata->ntp_tick_adj;
255 second_length += ntpdata->time_freq;
256
257 new_base = div_u64(dividend: second_length, NTP_INTERVAL_FREQ);
258
259 /*
260 * Don't wait for the next second_overflow, apply the change to the
261 * tick length immediately:
262 */
263 ntpdata->tick_length += new_base - ntpdata->tick_length_base;
264 ntpdata->tick_length_base = new_base;
265}
266
267static inline s64 ntp_update_offset_fll(struct ntp_data *ntpdata, s64 offset64, long secs)
268{
269 ntpdata->time_status &= ~STA_MODE;
270
271 if (secs < MINSEC)
272 return 0;
273
274 if (!(ntpdata->time_status & STA_FLL) && (secs <= MAXSEC))
275 return 0;
276
277 ntpdata->time_status |= STA_MODE;
278
279 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
280}
281
282static void ntp_update_offset(struct ntp_data *ntpdata, long offset)
283{
284 s64 freq_adj, offset64;
285 long secs, real_secs;
286
287 if (!(ntpdata->time_status & STA_PLL))
288 return;
289
290 if (!(ntpdata->time_status & STA_NANO)) {
291 /* Make sure the multiplication below won't overflow */
292 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
293 offset *= NSEC_PER_USEC;
294 }
295
296 /* Scale the phase adjustment and clamp to the operating range. */
297 offset = clamp(offset, -MAXPHASE, MAXPHASE);
298
299 /*
300 * Select how the frequency is to be controlled
301 * and in which mode (PLL or FLL).
302 */
303 real_secs = __ktime_get_real_seconds();
304 secs = (long)(real_secs - ntpdata->time_reftime);
305 if (unlikely(ntpdata->time_status & STA_FREQHOLD))
306 secs = 0;
307
308 ntpdata->time_reftime = real_secs;
309
310 offset64 = offset;
311 freq_adj = ntp_update_offset_fll(ntpdata, offset64, secs);
312
313 /*
314 * Clamp update interval to reduce PLL gain with low
315 * sampling rate (e.g. intermittent network connection)
316 * to avoid instability.
317 */
318 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + ntpdata->time_constant)))
319 secs = 1 << (SHIFT_PLL + 1 + ntpdata->time_constant);
320
321 freq_adj += (offset64 * secs) <<
322 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + ntpdata->time_constant));
323
324 freq_adj = min(freq_adj + ntpdata->time_freq, MAXFREQ_SCALED);
325
326 ntpdata->time_freq = max(freq_adj, -MAXFREQ_SCALED);
327
328 ntpdata->time_offset = div_s64(dividend: offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
329}
330
331static void __ntp_clear(struct ntp_data *ntpdata)
332{
333 /* Stop active adjtime() */
334 ntpdata->time_adjust = 0;
335 ntpdata->time_status |= STA_UNSYNC;
336 ntpdata->time_maxerror = NTP_PHASE_LIMIT;
337 ntpdata->time_esterror = NTP_PHASE_LIMIT;
338
339 ntp_update_frequency(ntpdata);
340
341 ntpdata->tick_length = ntpdata->tick_length_base;
342 ntpdata->time_offset = 0;
343
344 ntpdata->ntp_next_leap_sec = TIME64_MAX;
345 /* Clear PPS state variables */
346 pps_clear(ntpdata);
347}
348
349/**
350 * ntp_clear - Clears the NTP state variables
351 */
352void ntp_clear(void)
353{
354 __ntp_clear(ntpdata: &tk_ntp_data);
355}
356
357
358u64 ntp_tick_length(void)
359{
360 return tk_ntp_data.tick_length;
361}
362
363/**
364 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
365 *
366 * Provides the time of the next leapsecond against CLOCK_REALTIME in
367 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
368 */
369ktime_t ntp_get_next_leap(void)
370{
371 struct ntp_data *ntpdata = &tk_ntp_data;
372 ktime_t ret;
373
374 if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS))
375 return ktime_set(secs: ntpdata->ntp_next_leap_sec, nsecs: 0);
376 ret = KTIME_MAX;
377 return ret;
378}
379
380/*
381 * This routine handles the overflow of the microsecond field
382 *
383 * The tricky bits of code to handle the accurate clock support
384 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
385 * They were originally developed for SUN and DEC kernels.
386 * All the kudos should go to Dave for this stuff.
387 *
388 * Also handles leap second processing, and returns leap offset
389 */
390int second_overflow(time64_t secs)
391{
392 struct ntp_data *ntpdata = &tk_ntp_data;
393 s64 delta;
394 int leap = 0;
395 s32 rem;
396
397 /*
398 * Leap second processing. If in leap-insert state at the end of the
399 * day, the system clock is set back one second; if in leap-delete
400 * state, the system clock is set ahead one second.
401 */
402 switch (ntpdata->time_state) {
403 case TIME_OK:
404 if (ntpdata->time_status & STA_INS) {
405 ntpdata->time_state = TIME_INS;
406 div_s64_rem(dividend: secs, SECS_PER_DAY, remainder: &rem);
407 ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
408 } else if (ntpdata->time_status & STA_DEL) {
409 ntpdata->time_state = TIME_DEL;
410 div_s64_rem(dividend: secs + 1, SECS_PER_DAY, remainder: &rem);
411 ntpdata->ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
412 }
413 break;
414 case TIME_INS:
415 if (!(ntpdata->time_status & STA_INS)) {
416 ntpdata->ntp_next_leap_sec = TIME64_MAX;
417 ntpdata->time_state = TIME_OK;
418 } else if (secs == ntpdata->ntp_next_leap_sec) {
419 leap = -1;
420 ntpdata->time_state = TIME_OOP;
421 pr_notice("Clock: inserting leap second 23:59:60 UTC\n");
422 }
423 break;
424 case TIME_DEL:
425 if (!(ntpdata->time_status & STA_DEL)) {
426 ntpdata->ntp_next_leap_sec = TIME64_MAX;
427 ntpdata->time_state = TIME_OK;
428 } else if (secs == ntpdata->ntp_next_leap_sec) {
429 leap = 1;
430 ntpdata->ntp_next_leap_sec = TIME64_MAX;
431 ntpdata->time_state = TIME_WAIT;
432 pr_notice("Clock: deleting leap second 23:59:59 UTC\n");
433 }
434 break;
435 case TIME_OOP:
436 ntpdata->ntp_next_leap_sec = TIME64_MAX;
437 ntpdata->time_state = TIME_WAIT;
438 break;
439 case TIME_WAIT:
440 if (!(ntpdata->time_status & (STA_INS | STA_DEL)))
441 ntpdata->time_state = TIME_OK;
442 break;
443 }
444
445 /* Bump the maxerror field */
446 ntpdata->time_maxerror += MAXFREQ / NSEC_PER_USEC;
447 if (ntpdata->time_maxerror > NTP_PHASE_LIMIT) {
448 ntpdata->time_maxerror = NTP_PHASE_LIMIT;
449 ntpdata->time_status |= STA_UNSYNC;
450 }
451
452 /* Compute the phase adjustment for the next second */
453 ntpdata->tick_length = ntpdata->tick_length_base;
454
455 delta = ntp_offset_chunk(ntpdata, offset: ntpdata->time_offset);
456 ntpdata->time_offset -= delta;
457 ntpdata->tick_length += delta;
458
459 /* Check PPS signal */
460 pps_dec_valid(ntpdata);
461
462 if (!ntpdata->time_adjust)
463 goto out;
464
465 if (ntpdata->time_adjust > MAX_TICKADJ) {
466 ntpdata->time_adjust -= MAX_TICKADJ;
467 ntpdata->tick_length += MAX_TICKADJ_SCALED;
468 goto out;
469 }
470
471 if (ntpdata->time_adjust < -MAX_TICKADJ) {
472 ntpdata->time_adjust += MAX_TICKADJ;
473 ntpdata->tick_length -= MAX_TICKADJ_SCALED;
474 goto out;
475 }
476
477 ntpdata->tick_length += (s64)(ntpdata->time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
478 << NTP_SCALE_SHIFT;
479 ntpdata->time_adjust = 0;
480
481out:
482 return leap;
483}
484
485#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
486static void sync_hw_clock(struct work_struct *work);
487static DECLARE_WORK(sync_work, sync_hw_clock);
488static struct hrtimer sync_hrtimer;
489#define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC)
490
491static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
492{
493 queue_work(wq: system_freezable_power_efficient_wq, work: &sync_work);
494
495 return HRTIMER_NORESTART;
496}
497
498static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry)
499{
500 ktime_t exp = ktime_set(secs: ktime_get_real_seconds(), nsecs: 0);
501
502 if (retry)
503 exp = ktime_add_ns(exp, 2ULL * NSEC_PER_SEC - offset_nsec);
504 else
505 exp = ktime_add_ns(exp, SYNC_PERIOD_NS - offset_nsec);
506
507 hrtimer_start(timer: &sync_hrtimer, tim: exp, mode: HRTIMER_MODE_ABS);
508}
509
510/*
511 * Check whether @now is correct versus the required time to update the RTC
512 * and calculate the value which needs to be written to the RTC so that the
513 * next seconds increment of the RTC after the write is aligned with the next
514 * seconds increment of clock REALTIME.
515 *
516 * tsched t1 write(t2.tv_sec - 1sec)) t2 RTC increments seconds
517 *
518 * t2.tv_nsec == 0
519 * tsched = t2 - set_offset_nsec
520 * newval = t2 - NSEC_PER_SEC
521 *
522 * ==> neval = tsched + set_offset_nsec - NSEC_PER_SEC
523 *
524 * As the execution of this code is not guaranteed to happen exactly at
525 * tsched this allows it to happen within a fuzzy region:
526 *
527 * abs(now - tsched) < FUZZ
528 *
529 * If @now is not inside the allowed window the function returns false.
530 */
531static inline bool rtc_tv_nsec_ok(unsigned long set_offset_nsec,
532 struct timespec64 *to_set,
533 const struct timespec64 *now)
534{
535 /* Allowed error in tv_nsec, arbitrarily set to 5 jiffies in ns. */
536 const unsigned long TIME_SET_NSEC_FUZZ = TICK_NSEC * 5;
537 struct timespec64 delay = {.tv_sec = -1,
538 .tv_nsec = set_offset_nsec};
539
540 *to_set = timespec64_add(lhs: *now, rhs: delay);
541
542 if (to_set->tv_nsec < TIME_SET_NSEC_FUZZ) {
543 to_set->tv_nsec = 0;
544 return true;
545 }
546
547 if (to_set->tv_nsec > NSEC_PER_SEC - TIME_SET_NSEC_FUZZ) {
548 to_set->tv_sec++;
549 to_set->tv_nsec = 0;
550 return true;
551 }
552 return false;
553}
554
555#ifdef CONFIG_GENERIC_CMOS_UPDATE
556int __weak update_persistent_clock64(struct timespec64 now64)
557{
558 return -ENODEV;
559}
560#else
561static inline int update_persistent_clock64(struct timespec64 now64)
562{
563 return -ENODEV;
564}
565#endif
566
567#ifdef CONFIG_RTC_SYSTOHC
568/* Save NTP synchronized time to the RTC */
569static int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
570{
571 struct rtc_device *rtc;
572 struct rtc_time tm;
573 int err = -ENODEV;
574
575 rtc = rtc_class_open(CONFIG_RTC_SYSTOHC_DEVICE);
576 if (!rtc)
577 return -ENODEV;
578
579 if (!rtc->ops || !rtc->ops->set_time)
580 goto out_close;
581
582 /* First call might not have the correct offset */
583 if (*offset_nsec == rtc->set_offset_nsec) {
584 rtc_time64_to_tm(time: to_set->tv_sec, tm: &tm);
585 err = rtc_set_time(rtc, tm: &tm);
586 } else {
587 /* Store the update offset and let the caller try again */
588 *offset_nsec = rtc->set_offset_nsec;
589 err = -EAGAIN;
590 }
591out_close:
592 rtc_class_close(rtc);
593 return err;
594}
595#else
596static inline int update_rtc(struct timespec64 *to_set, unsigned long *offset_nsec)
597{
598 return -ENODEV;
599}
600#endif
601
602/**
603 * ntp_synced - Tells whether the NTP status is not UNSYNC
604 * Returns: true if not UNSYNC, false otherwise
605 */
606static inline bool ntp_synced(void)
607{
608 return !(tk_ntp_data.time_status & STA_UNSYNC);
609}
610
611/*
612 * If we have an externally synchronized Linux clock, then update RTC clock
613 * accordingly every ~11 minutes. Generally RTCs can only store second
614 * precision, but many RTCs will adjust the phase of their second tick to
615 * match the moment of update. This infrastructure arranges to call to the RTC
616 * set at the correct moment to phase synchronize the RTC second tick over
617 * with the kernel clock.
618 */
619static void sync_hw_clock(struct work_struct *work)
620{
621 /*
622 * The default synchronization offset is 500ms for the deprecated
623 * update_persistent_clock64() under the assumption that it uses
624 * the infamous CMOS clock (MC146818).
625 */
626 static unsigned long offset_nsec = NSEC_PER_SEC / 2;
627 struct timespec64 now, to_set;
628 int res = -EAGAIN;
629
630 /*
631 * Don't update if STA_UNSYNC is set and if ntp_notify_cmos_timer()
632 * managed to schedule the work between the timer firing and the
633 * work being able to rearm the timer. Wait for the timer to expire.
634 */
635 if (!ntp_synced() || hrtimer_is_queued(timer: &sync_hrtimer))
636 return;
637
638 ktime_get_real_ts64(tv: &now);
639 /* If @now is not in the allowed window, try again */
640 if (!rtc_tv_nsec_ok(set_offset_nsec: offset_nsec, to_set: &to_set, now: &now))
641 goto rearm;
642
643 /* Take timezone adjusted RTCs into account */
644 if (persistent_clock_is_local)
645 to_set.tv_sec -= (sys_tz.tz_minuteswest * 60);
646
647 /* Try the legacy RTC first. */
648 res = update_persistent_clock64(now64: to_set);
649 if (res != -ENODEV)
650 goto rearm;
651
652 /* Try the RTC class */
653 res = update_rtc(to_set: &to_set, offset_nsec: &offset_nsec);
654 if (res == -ENODEV)
655 return;
656rearm:
657 sched_sync_hw_clock(offset_nsec, retry: res != 0);
658}
659
660void ntp_notify_cmos_timer(bool offset_set)
661{
662 /*
663 * If the time jumped (using ADJ_SETOFFSET) cancels sync timer,
664 * which may have been running if the time was synchronized
665 * prior to the ADJ_SETOFFSET call.
666 */
667 if (offset_set)
668 hrtimer_cancel(timer: &sync_hrtimer);
669
670 /*
671 * When the work is currently executed but has not yet the timer
672 * rearmed this queues the work immediately again. No big issue,
673 * just a pointless work scheduled.
674 */
675 if (ntp_synced() && !hrtimer_is_queued(timer: &sync_hrtimer))
676 queue_work(wq: system_freezable_power_efficient_wq, work: &sync_work);
677}
678
679static void __init ntp_init_cmos_sync(void)
680{
681 hrtimer_setup(timer: &sync_hrtimer, function: sync_timer_callback, CLOCK_REALTIME, mode: HRTIMER_MODE_ABS);
682}
683#else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
684static inline void __init ntp_init_cmos_sync(void) { }
685#endif /* !CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
686
687/*
688 * Propagate a new txc->status value into the NTP state:
689 */
690static inline void process_adj_status(struct ntp_data *ntpdata, const struct __kernel_timex *txc)
691{
692 if ((ntpdata->time_status & STA_PLL) && !(txc->status & STA_PLL)) {
693 ntpdata->time_state = TIME_OK;
694 ntpdata->time_status = STA_UNSYNC;
695 ntpdata->ntp_next_leap_sec = TIME64_MAX;
696 /* Restart PPS frequency calibration */
697 pps_reset_freq_interval(ntpdata);
698 }
699
700 /*
701 * If we turn on PLL adjustments then reset the
702 * reference time to current time.
703 */
704 if (!(ntpdata->time_status & STA_PLL) && (txc->status & STA_PLL))
705 ntpdata->time_reftime = __ktime_get_real_seconds();
706
707 /* only set allowed bits */
708 ntpdata->time_status &= STA_RONLY;
709 ntpdata->time_status |= txc->status & ~STA_RONLY;
710}
711
712static inline void process_adjtimex_modes(struct ntp_data *ntpdata, const struct __kernel_timex *txc,
713 s32 *time_tai)
714{
715 if (txc->modes & ADJ_STATUS)
716 process_adj_status(ntpdata, txc);
717
718 if (txc->modes & ADJ_NANO)
719 ntpdata->time_status |= STA_NANO;
720
721 if (txc->modes & ADJ_MICRO)
722 ntpdata->time_status &= ~STA_NANO;
723
724 if (txc->modes & ADJ_FREQUENCY) {
725 ntpdata->time_freq = txc->freq * PPM_SCALE;
726 ntpdata->time_freq = min(ntpdata->time_freq, MAXFREQ_SCALED);
727 ntpdata->time_freq = max(ntpdata->time_freq, -MAXFREQ_SCALED);
728 /* Update pps_freq */
729 pps_set_freq(ntpdata);
730 }
731
732 if (txc->modes & ADJ_MAXERROR)
733 ntpdata->time_maxerror = clamp(txc->maxerror, 0, NTP_PHASE_LIMIT);
734
735 if (txc->modes & ADJ_ESTERROR)
736 ntpdata->time_esterror = clamp(txc->esterror, 0, NTP_PHASE_LIMIT);
737
738 if (txc->modes & ADJ_TIMECONST) {
739 ntpdata->time_constant = clamp(txc->constant, 0, MAXTC);
740 if (!(ntpdata->time_status & STA_NANO))
741 ntpdata->time_constant += 4;
742 ntpdata->time_constant = clamp(ntpdata->time_constant, 0, MAXTC);
743 }
744
745 if (txc->modes & ADJ_TAI && txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
746 *time_tai = txc->constant;
747
748 if (txc->modes & ADJ_OFFSET)
749 ntp_update_offset(ntpdata, offset: txc->offset);
750
751 if (txc->modes & ADJ_TICK)
752 ntpdata->tick_usec = txc->tick;
753
754 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
755 ntp_update_frequency(ntpdata);
756}
757
758/*
759 * adjtimex() mainly allows reading (and writing, if superuser) of
760 * kernel time-keeping variables. used by xntpd.
761 */
762int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts,
763 s32 *time_tai, struct audit_ntp_data *ad)
764{
765 struct ntp_data *ntpdata = &tk_ntp_data;
766 int result;
767
768 if (txc->modes & ADJ_ADJTIME) {
769 long save_adjust = ntpdata->time_adjust;
770
771 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
772 /* adjtime() is independent from ntp_adjtime() */
773 ntpdata->time_adjust = txc->offset;
774 ntp_update_frequency(ntpdata);
775
776 audit_ntp_set_old(ad, type: AUDIT_NTP_ADJUST, val: save_adjust);
777 audit_ntp_set_new(ad, type: AUDIT_NTP_ADJUST, val: ntpdata->time_adjust);
778 }
779 txc->offset = save_adjust;
780 } else {
781 /* If there are input parameters, then process them: */
782 if (txc->modes) {
783 audit_ntp_set_old(ad, type: AUDIT_NTP_OFFSET, val: ntpdata->time_offset);
784 audit_ntp_set_old(ad, type: AUDIT_NTP_FREQ, val: ntpdata->time_freq);
785 audit_ntp_set_old(ad, type: AUDIT_NTP_STATUS, val: ntpdata->time_status);
786 audit_ntp_set_old(ad, type: AUDIT_NTP_TAI, val: *time_tai);
787 audit_ntp_set_old(ad, type: AUDIT_NTP_TICK, val: ntpdata->tick_usec);
788
789 process_adjtimex_modes(ntpdata, txc, time_tai);
790
791 audit_ntp_set_new(ad, type: AUDIT_NTP_OFFSET, val: ntpdata->time_offset);
792 audit_ntp_set_new(ad, type: AUDIT_NTP_FREQ, val: ntpdata->time_freq);
793 audit_ntp_set_new(ad, type: AUDIT_NTP_STATUS, val: ntpdata->time_status);
794 audit_ntp_set_new(ad, type: AUDIT_NTP_TAI, val: *time_tai);
795 audit_ntp_set_new(ad, type: AUDIT_NTP_TICK, val: ntpdata->tick_usec);
796 }
797
798 txc->offset = shift_right(ntpdata->time_offset * NTP_INTERVAL_FREQ, NTP_SCALE_SHIFT);
799 if (!(ntpdata->time_status & STA_NANO))
800 txc->offset = div_s64(dividend: txc->offset, NSEC_PER_USEC);
801 }
802
803 result = ntpdata->time_state;
804 if (is_error_status(status: ntpdata->time_status))
805 result = TIME_ERROR;
806
807 txc->freq = shift_right((ntpdata->time_freq >> PPM_SCALE_INV_SHIFT) *
808 PPM_SCALE_INV, NTP_SCALE_SHIFT);
809 txc->maxerror = ntpdata->time_maxerror;
810 txc->esterror = ntpdata->time_esterror;
811 txc->status = ntpdata->time_status;
812 txc->constant = ntpdata->time_constant;
813 txc->precision = 1;
814 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
815 txc->tick = ntpdata->tick_usec;
816 txc->tai = *time_tai;
817
818 /* Fill PPS status fields */
819 pps_fill_timex(ntpdata, txc);
820
821 txc->time.tv_sec = ts->tv_sec;
822 txc->time.tv_usec = ts->tv_nsec;
823 if (!(ntpdata->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 >= ntpdata->ntp_next_leap_sec)) {
828 if ((ntpdata->time_state == TIME_INS) && (ntpdata->time_status & STA_INS)) {
829 result = TIME_OOP;
830 txc->tai++;
831 txc->time.tv_sec--;
832 }
833 if ((ntpdata->time_state == TIME_DEL) && (ntpdata->time_status & STA_DEL)) {
834 result = TIME_WAIT;
835 txc->tai--;
836 txc->time.tv_sec++;
837 }
838 if ((ntpdata->time_state == TIME_OOP) && (ts->tv_sec == ntpdata->ntp_next_leap_sec))
839 result = TIME_WAIT;
840 }
841
842 return result;
843}
844
845#ifdef CONFIG_NTP_PPS
846
847/*
848 * struct pps_normtime is basically a struct timespec, but it is
849 * semantically different (and it is the reason why it was invented):
850 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
851 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC)
852 */
853struct pps_normtime {
854 s64 sec; /* seconds */
855 long nsec; /* nanoseconds */
856};
857
858/*
859 * Normalize the timestamp so that nsec is in the
860 * [ -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval
861 */
862static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
863{
864 struct pps_normtime norm = {
865 .sec = ts.tv_sec,
866 .nsec = ts.tv_nsec
867 };
868
869 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
870 norm.nsec -= NSEC_PER_SEC;
871 norm.sec++;
872 }
873
874 return norm;
875}
876
877/* Get current phase correction and jitter */
878static inline long pps_phase_filter_get(struct ntp_data *ntpdata, long *jitter)
879{
880 *jitter = ntpdata->pps_tf[0] - ntpdata->pps_tf[1];
881 if (*jitter < 0)
882 *jitter = -*jitter;
883
884 /* TODO: test various filters */
885 return ntpdata->pps_tf[0];
886}
887
888/* Add the sample to the phase filter */
889static inline void pps_phase_filter_add(struct ntp_data *ntpdata, long err)
890{
891 ntpdata->pps_tf[2] = ntpdata->pps_tf[1];
892 ntpdata->pps_tf[1] = ntpdata->pps_tf[0];
893 ntpdata->pps_tf[0] = err;
894}
895
896/*
897 * Decrease frequency calibration interval length. It is halved after four
898 * consecutive unstable intervals.
899 */
900static inline void pps_dec_freq_interval(struct ntp_data *ntpdata)
901{
902 if (--ntpdata->pps_intcnt <= -PPS_INTCOUNT) {
903 ntpdata->pps_intcnt = -PPS_INTCOUNT;
904 if (ntpdata->pps_shift > PPS_INTMIN) {
905 ntpdata->pps_shift--;
906 ntpdata->pps_intcnt = 0;
907 }
908 }
909}
910
911/*
912 * Increase frequency calibration interval length. It is doubled after
913 * four consecutive stable intervals.
914 */
915static inline void pps_inc_freq_interval(struct ntp_data *ntpdata)
916{
917 if (++ntpdata->pps_intcnt >= PPS_INTCOUNT) {
918 ntpdata->pps_intcnt = PPS_INTCOUNT;
919 if (ntpdata->pps_shift < PPS_INTMAX) {
920 ntpdata->pps_shift++;
921 ntpdata->pps_intcnt = 0;
922 }
923 }
924}
925
926/*
927 * Update clock frequency based on MONOTONIC_RAW clock PPS signal
928 * timestamps
929 *
930 * At the end of the calibration interval the difference between the
931 * first and last MONOTONIC_RAW clock timestamps divided by the length
932 * of the interval becomes the frequency update. If the interval was
933 * too long, the data are discarded.
934 * Returns the difference between old and new frequency values.
935 */
936static long hardpps_update_freq(struct ntp_data *ntpdata, struct pps_normtime freq_norm)
937{
938 long delta, delta_mod;
939 s64 ftemp;
940
941 /* Check if the frequency interval was too long */
942 if (freq_norm.sec > (2 << ntpdata->pps_shift)) {
943 ntpdata->time_status |= STA_PPSERROR;
944 ntpdata->pps_errcnt++;
945 pps_dec_freq_interval(ntpdata);
946 printk_deferred(KERN_ERR "hardpps: PPSERROR: interval too long - %lld s\n",
947 freq_norm.sec);
948 return 0;
949 }
950
951 /*
952 * Here the raw frequency offset and wander (stability) is
953 * calculated. If the wander is less than the wander threshold the
954 * interval is increased; otherwise it is decreased.
955 */
956 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
957 freq_norm.sec);
958 delta = shift_right(ftemp - ntpdata->pps_freq, NTP_SCALE_SHIFT);
959 ntpdata->pps_freq = ftemp;
960 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
961 printk_deferred(KERN_WARNING "hardpps: PPSWANDER: change=%ld\n", delta);
962 ntpdata->time_status |= STA_PPSWANDER;
963 ntpdata->pps_stbcnt++;
964 pps_dec_freq_interval(ntpdata);
965 } else {
966 /* Good sample */
967 pps_inc_freq_interval(ntpdata);
968 }
969
970 /*
971 * The stability metric is calculated as the average of recent
972 * frequency changes, but is used only for performance monitoring
973 */
974 delta_mod = delta;
975 if (delta_mod < 0)
976 delta_mod = -delta_mod;
977 ntpdata->pps_stabil += (div_s64(((s64)delta_mod) << (NTP_SCALE_SHIFT - SHIFT_USEC),
978 NSEC_PER_USEC) - ntpdata->pps_stabil) >> PPS_INTMIN;
979
980 /* If enabled, the system clock frequency is updated */
981 if ((ntpdata->time_status & STA_PPSFREQ) && !(ntpdata->time_status & STA_FREQHOLD)) {
982 ntpdata->time_freq = ntpdata->pps_freq;
983 ntp_update_frequency(ntpdata);
984 }
985
986 return delta;
987}
988
989/* Correct REALTIME clock phase error against PPS signal */
990static void hardpps_update_phase(struct ntp_data *ntpdata, long error)
991{
992 long correction = -error;
993 long jitter;
994
995 /* Add the sample to the median filter */
996 pps_phase_filter_add(ntpdata, correction);
997 correction = pps_phase_filter_get(ntpdata, &jitter);
998
999 /*
1000 * Nominal jitter is due to PPS signal noise. If it exceeds the
1001 * threshold, the sample is discarded; otherwise, if so enabled,
1002 * the time offset is updated.
1003 */
1004 if (jitter > (ntpdata->pps_jitter << PPS_POPCORN)) {
1005 printk_deferred(KERN_WARNING "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
1006 jitter, (ntpdata->pps_jitter << PPS_POPCORN));
1007 ntpdata->time_status |= STA_PPSJITTER;
1008 ntpdata->pps_jitcnt++;
1009 } else if (ntpdata->time_status & STA_PPSTIME) {
1010 /* Correct the time using the phase offset */
1011 ntpdata->time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
1012 NTP_INTERVAL_FREQ);
1013 /* Cancel running adjtime() */
1014 ntpdata->time_adjust = 0;
1015 }
1016 /* Update jitter */
1017 ntpdata->pps_jitter += (jitter - ntpdata->pps_jitter) >> PPS_INTMIN;
1018}
1019
1020/*
1021 * __hardpps() - discipline CPU clock oscillator to external PPS signal
1022 *
1023 * This routine is called at each PPS signal arrival in order to
1024 * discipline the CPU clock oscillator to the PPS signal. It takes two
1025 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
1026 * is used to correct clock phase error and the latter is used to
1027 * correct the frequency.
1028 *
1029 * This code is based on David Mills's reference nanokernel
1030 * implementation. It was mostly rewritten but keeps the same idea.
1031 */
1032void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
1033{
1034 struct pps_normtime pts_norm, freq_norm;
1035 struct ntp_data *ntpdata = &tk_ntp_data;
1036
1037 pts_norm = pps_normalize_ts(*phase_ts);
1038
1039 /* Clear the error bits, they will be set again if needed */
1040 ntpdata->time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
1041
1042 /* indicate signal presence */
1043 ntpdata->time_status |= STA_PPSSIGNAL;
1044 ntpdata->pps_valid = PPS_VALID;
1045
1046 /*
1047 * When called for the first time, just start the frequency
1048 * interval
1049 */
1050 if (unlikely(ntpdata->pps_fbase.tv_sec == 0)) {
1051 ntpdata->pps_fbase = *raw_ts;
1052 return;
1053 }
1054
1055 /* Ok, now we have a base for frequency calculation */
1056 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, ntpdata->pps_fbase));
1057
1058 /*
1059 * Check that the signal is in the range
1060 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it
1061 */
1062 if ((freq_norm.sec == 0) || (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1063 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1064 ntpdata->time_status |= STA_PPSJITTER;
1065 /* Restart the frequency calibration interval */
1066 ntpdata->pps_fbase = *raw_ts;
1067 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1068 return;
1069 }
1070
1071 /* Signal is ok. Check if the current frequency interval is finished */
1072 if (freq_norm.sec >= (1 << ntpdata->pps_shift)) {
1073 ntpdata->pps_calcnt++;
1074 /* Restart the frequency calibration interval */
1075 ntpdata->pps_fbase = *raw_ts;
1076 hardpps_update_freq(ntpdata, freq_norm);
1077 }
1078
1079 hardpps_update_phase(ntpdata, pts_norm.nsec);
1080
1081}
1082#endif /* CONFIG_NTP_PPS */
1083
1084static int __init ntp_tick_adj_setup(char *str)
1085{
1086 int rc = kstrtos64(s: str, base: 0, res: &tk_ntp_data.ntp_tick_adj);
1087 if (rc)
1088 return rc;
1089
1090 tk_ntp_data.ntp_tick_adj <<= NTP_SCALE_SHIFT;
1091 return 1;
1092}
1093
1094__setup("ntp_tick_adj=", ntp_tick_adj_setup);
1095
1096void __init ntp_init(void)
1097{
1098 ntp_clear();
1099 ntp_init_cmos_sync();
1100}
1101

Provided by KDAB

Privacy Policy
Improve your Profiling and Debugging skills
Find out more

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