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): */
34unsigned long tick_usec = USER_TICK_USEC;
35
36/* SHIFTED_HZ period (nsecs): */
37unsigned long tick_nsec;
38
39static u64 tick_length;
40static 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 */
57static int time_state = TIME_OK;
58
59/* clock status bits: */
60static int time_status = STA_UNSYNC;
61
62/* time adjustment (nsecs): */
63static s64 time_offset;
64
65/* pll time constant: */
66static long time_constant = 2;
67
68/* maximum error (usecs): */
69static long time_maxerror = NTP_PHASE_LIMIT;
70
71/* estimated error (usecs): */
72static long time_esterror = NTP_PHASE_LIMIT;
73
74/* frequency offset (scaled nsecs/secs): */
75static s64 time_freq;
76
77/* time at last adjustment (secs): */
78static time64_t time_reftime;
79
80static long time_adjust;
81
82/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
83static s64 ntp_tick_adj;
84
85/* second value of the next pending leapsecond, or TIME64_MAX if no leap */
86static 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
104static int pps_valid; /* signal watchdog counter */
105static long pps_tf[3]; /* phase median filter */
106static long pps_jitter; /* current jitter (ns) */
107static struct timespec64 pps_fbase; /* beginning of the last freq interval */
108static int pps_shift; /* current interval duration (s) (shift) */
109static int pps_intcnt; /* interval counter */
110static s64 pps_freq; /* frequency offset (scaled ns/s) */
111static long pps_stabil; /* current stability (scaled ns/s) */
112
113/*
114 * PPS signal quality monitors
115 */
116static long pps_calcnt; /* calibration intervals */
117static long pps_jitcnt; /* jitter limit exceeded */
118static long pps_stbcnt; /* stability limit exceeded */
119static 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 */
125static 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
133static 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 */
144static 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 */
158static 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
169static inline void pps_set_freq(s64 freq)
170{
171 pps_freq = freq;
172}
173
174static 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
193static 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
210static inline s64 ntp_offset_chunk(s64 offset)
211{
212 return shift_right(offset, SHIFT_PLL + time_constant);
213}
214
215static inline void pps_reset_freq_interval(void) {}
216static inline void pps_clear(void) {}
217static inline void pps_dec_valid(void) {}
218static inline void pps_set_freq(s64 freq) {}
219
220static inline int is_error_status(int status)
221{
222 return status & (STA_UNSYNC|STA_CLOCKERR);
223}
224
225static 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 */
245static 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 */
259static 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(dividend: second_length, HZ) >> NTP_SCALE_SHIFT;
271 new_base = div_u64(dividend: 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
281static 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
296static 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(dividend: offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
346}
347
348/**
349 * ntp_clear - Clears the NTP state variables
350 */
351void 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
369u64 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 */
380ktime_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(secs: ntp_next_leap_sec, nsecs: 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 */
400int 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(dividend: secs, SECS_PER_DAY, remainder: &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(dividend: secs + 1, SECS_PER_DAY, remainder: &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(offset: 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
493out:
494 return leap;
495}
496
497#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
498static void sync_hw_clock(struct work_struct *work);
499static DECLARE_WORK(sync_work, sync_hw_clock);
500static struct hrtimer sync_hrtimer;
501#define SYNC_PERIOD_NS (11ULL * 60 * NSEC_PER_SEC)
502
503static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
504{
505 queue_work(wq: system_freezable_power_efficient_wq, work: &sync_work);
506
507 return HRTIMER_NORESTART;
508}
509
510static void sched_sync_hw_clock(unsigned long offset_nsec, bool retry)
511{
512 ktime_t exp = ktime_set(secs: ktime_get_real_seconds(), nsecs: 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(timer: &sync_hrtimer, tim: exp, mode: 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 */
543static 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(lhs: *now, rhs: 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
568int __weak update_persistent_clock64(struct timespec64 now64)
569{
570 return -ENODEV;
571}
572#else
573static 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 */
581static 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(time: to_set->tv_sec, tm: &tm);
597 err = rtc_set_time(rtc, tm: &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 }
603out_close:
604 rtc_class_close(rtc);
605 return err;
606}
607#else
608static 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 */
622static 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(timer: &sync_hrtimer))
639 return;
640
641 ktime_get_real_ts64(tv: &now);
642 /* If @now is not in the allowed window, try again */
643 if (!rtc_tv_nsec_ok(set_offset_nsec: offset_nsec, to_set: &to_set, now: &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(now64: to_set);
652 if (res != -ENODEV)
653 goto rearm;
654
655 /* Try the RTC class */
656 res = update_rtc(to_set: &to_set, offset_nsec: &offset_nsec);
657 if (res == -ENODEV)
658 return;
659rearm:
660 sched_sync_hw_clock(offset_nsec, retry: res != 0);
661}
662
663void 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(timer: &sync_hrtimer))
671 queue_work(wq: system_freezable_power_efficient_wq, work: &sync_work);
672}
673
674static void __init ntp_init_cmos_sync(void)
675{
676 hrtimer_init(timer: &sync_hrtimer, CLOCK_REALTIME, mode: HRTIMER_MODE_ABS);
677 sync_hrtimer.function = sync_timer_callback;
678}
679#else /* CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) */
680static 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 */
686static 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
709static 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(freq: time_freq);
727 }
728
729 if (txc->modes & ADJ_MAXERROR)
730 time_maxerror = txc->maxerror;
731
732 if (txc->modes & ADJ_ESTERROR)
733 time_esterror = txc->esterror;
734
735 if (txc->modes & ADJ_TIMECONST) {
736 time_constant = txc->constant;
737 if (!(time_status & STA_NANO))
738 time_constant += 4;
739 time_constant = min(time_constant, (long)MAXTC);
740 time_constant = max(time_constant, 0l);
741 }
742
743 if (txc->modes & ADJ_TAI &&
744 txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
745 *time_tai = txc->constant;
746
747 if (txc->modes & ADJ_OFFSET)
748 ntp_update_offset(offset: txc->offset);
749
750 if (txc->modes & ADJ_TICK)
751 tick_usec = txc->tick;
752
753 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
754 ntp_update_frequency();
755}
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 int result;
766
767 if (txc->modes & ADJ_ADJTIME) {
768 long save_adjust = time_adjust;
769
770 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
771 /* adjtime() is independent from ntp_adjtime() */
772 time_adjust = txc->offset;
773 ntp_update_frequency();
774
775 audit_ntp_set_old(ad, type: AUDIT_NTP_ADJUST, val: save_adjust);
776 audit_ntp_set_new(ad, type: AUDIT_NTP_ADJUST, val: time_adjust);
777 }
778 txc->offset = save_adjust;
779 } else {
780 /* If there are input parameters, then process them: */
781 if (txc->modes) {
782 audit_ntp_set_old(ad, type: AUDIT_NTP_OFFSET, val: time_offset);
783 audit_ntp_set_old(ad, type: AUDIT_NTP_FREQ, val: time_freq);
784 audit_ntp_set_old(ad, type: AUDIT_NTP_STATUS, val: time_status);
785 audit_ntp_set_old(ad, type: AUDIT_NTP_TAI, val: *time_tai);
786 audit_ntp_set_old(ad, type: AUDIT_NTP_TICK, val: tick_usec);
787
788 process_adjtimex_modes(txc, time_tai);
789
790 audit_ntp_set_new(ad, type: AUDIT_NTP_OFFSET, val: time_offset);
791 audit_ntp_set_new(ad, type: AUDIT_NTP_FREQ, val: time_freq);
792 audit_ntp_set_new(ad, type: AUDIT_NTP_STATUS, val: time_status);
793 audit_ntp_set_new(ad, type: AUDIT_NTP_TAI, val: *time_tai);
794 audit_ntp_set_new(ad, type: AUDIT_NTP_TICK, val: tick_usec);
795 }
796
797 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
798 NTP_SCALE_SHIFT);
799 if (!(time_status & STA_NANO))
800 txc->offset = (u32)txc->offset / NSEC_PER_USEC;
801 }
802
803 result = time_state; /* mostly `TIME_OK' */
804 /* check for errors */
805 if (is_error_status(status: time_status))
806 result = TIME_ERROR;
807
808 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
809 PPM_SCALE_INV, NTP_SCALE_SHIFT);
810 txc->maxerror = time_maxerror;
811 txc->esterror = time_esterror;
812 txc->status = time_status;
813 txc->constant = time_constant;
814 txc->precision = 1;
815 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
816 txc->tick = tick_usec;
817 txc->tai = *time_tai;
818
819 /* fill PPS status fields */
820 pps_fill_timex(txc);
821
822 txc->time.tv_sec = ts->tv_sec;
823 txc->time.tv_usec = ts->tv_nsec;
824 if (!(time_status & STA_NANO))
825 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;
826
827 /* Handle leapsec adjustments */
828 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
829 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
830 result = TIME_OOP;
831 txc->tai++;
832 txc->time.tv_sec--;
833 }
834 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
835 result = TIME_WAIT;
836 txc->tai--;
837 txc->time.tv_sec++;
838 }
839 if ((time_state == TIME_OOP) &&
840 (ts->tv_sec == ntp_next_leap_sec)) {
841 result = TIME_WAIT;
842 }
843 }
844
845 return result;
846}
847
848#ifdef CONFIG_NTP_PPS
849
850/* actually struct pps_normtime is good old struct timespec, but it is
851 * semantically different (and it is the reason why it was invented):
852 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
853 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
854struct pps_normtime {
855 s64 sec; /* seconds */
856 long nsec; /* nanoseconds */
857};
858
859/* normalize the timestamp so that nsec is in the
860 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
861static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
862{
863 struct pps_normtime norm = {
864 .sec = ts.tv_sec,
865 .nsec = ts.tv_nsec
866 };
867
868 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
869 norm.nsec -= NSEC_PER_SEC;
870 norm.sec++;
871 }
872
873 return norm;
874}
875
876/* get current phase correction and jitter */
877static inline long pps_phase_filter_get(long *jitter)
878{
879 *jitter = pps_tf[0] - pps_tf[1];
880 if (*jitter < 0)
881 *jitter = -*jitter;
882
883 /* TODO: test various filters */
884 return pps_tf[0];
885}
886
887/* add the sample to the phase filter */
888static inline void pps_phase_filter_add(long err)
889{
890 pps_tf[2] = pps_tf[1];
891 pps_tf[1] = pps_tf[0];
892 pps_tf[0] = err;
893}
894
895/* decrease frequency calibration interval length.
896 * It is halved after four consecutive unstable intervals.
897 */
898static inline void pps_dec_freq_interval(void)
899{
900 if (--pps_intcnt <= -PPS_INTCOUNT) {
901 pps_intcnt = -PPS_INTCOUNT;
902 if (pps_shift > PPS_INTMIN) {
903 pps_shift--;
904 pps_intcnt = 0;
905 }
906 }
907}
908
909/* increase frequency calibration interval length.
910 * It is doubled after four consecutive stable intervals.
911 */
912static inline void pps_inc_freq_interval(void)
913{
914 if (++pps_intcnt >= PPS_INTCOUNT) {
915 pps_intcnt = PPS_INTCOUNT;
916 if (pps_shift < PPS_INTMAX) {
917 pps_shift++;
918 pps_intcnt = 0;
919 }
920 }
921}
922
923/* update clock frequency based on MONOTONIC_RAW clock PPS signal
924 * timestamps
925 *
926 * At the end of the calibration interval the difference between the
927 * first and last MONOTONIC_RAW clock timestamps divided by the length
928 * of the interval becomes the frequency update. If the interval was
929 * too long, the data are discarded.
930 * Returns the difference between old and new frequency values.
931 */
932static long hardpps_update_freq(struct pps_normtime freq_norm)
933{
934 long delta, delta_mod;
935 s64 ftemp;
936
937 /* check if the frequency interval was too long */
938 if (freq_norm.sec > (2 << pps_shift)) {
939 time_status |= STA_PPSERROR;
940 pps_errcnt++;
941 pps_dec_freq_interval();
942 printk_deferred(KERN_ERR
943 "hardpps: PPSERROR: interval too long - %lld s\n",
944 freq_norm.sec);
945 return 0;
946 }
947
948 /* here the raw frequency offset and wander (stability) is
949 * calculated. If the wander is less than the wander threshold
950 * the interval is increased; otherwise it is decreased.
951 */
952 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
953 freq_norm.sec);
954 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
955 pps_freq = ftemp;
956 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
957 printk_deferred(KERN_WARNING
958 "hardpps: PPSWANDER: change=%ld\n", delta);
959 time_status |= STA_PPSWANDER;
960 pps_stbcnt++;
961 pps_dec_freq_interval();
962 } else { /* good sample */
963 pps_inc_freq_interval();
964 }
965
966 /* the stability metric is calculated as the average of recent
967 * frequency changes, but is used only for performance
968 * monitoring
969 */
970 delta_mod = delta;
971 if (delta_mod < 0)
972 delta_mod = -delta_mod;
973 pps_stabil += (div_s64(((s64)delta_mod) <<
974 (NTP_SCALE_SHIFT - SHIFT_USEC),
975 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
976
977 /* if enabled, the system clock frequency is updated */
978 if ((time_status & STA_PPSFREQ) != 0 &&
979 (time_status & STA_FREQHOLD) == 0) {
980 time_freq = pps_freq;
981 ntp_update_frequency();
982 }
983
984 return delta;
985}
986
987/* correct REALTIME clock phase error against PPS signal */
988static void hardpps_update_phase(long error)
989{
990 long correction = -error;
991 long jitter;
992
993 /* add the sample to the median filter */
994 pps_phase_filter_add(correction);
995 correction = pps_phase_filter_get(&jitter);
996
997 /* Nominal jitter is due to PPS signal noise. If it exceeds the
998 * threshold, the sample is discarded; otherwise, if so enabled,
999 * the time offset is updated.
1000 */
1001 if (jitter > (pps_jitter << PPS_POPCORN)) {
1002 printk_deferred(KERN_WARNING
1003 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
1004 jitter, (pps_jitter << PPS_POPCORN));
1005 time_status |= STA_PPSJITTER;
1006 pps_jitcnt++;
1007 } else if (time_status & STA_PPSTIME) {
1008 /* correct the time using the phase offset */
1009 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
1010 NTP_INTERVAL_FREQ);
1011 /* cancel running adjtime() */
1012 time_adjust = 0;
1013 }
1014 /* update jitter */
1015 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
1016}
1017
1018/*
1019 * __hardpps() - discipline CPU clock oscillator to external PPS signal
1020 *
1021 * This routine is called at each PPS signal arrival in order to
1022 * discipline the CPU clock oscillator to the PPS signal. It takes two
1023 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
1024 * is used to correct clock phase error and the latter is used to
1025 * correct the frequency.
1026 *
1027 * This code is based on David Mills's reference nanokernel
1028 * implementation. It was mostly rewritten but keeps the same idea.
1029 */
1030void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
1031{
1032 struct pps_normtime pts_norm, freq_norm;
1033
1034 pts_norm = pps_normalize_ts(*phase_ts);
1035
1036 /* clear the error bits, they will be set again if needed */
1037 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
1038
1039 /* indicate signal presence */
1040 time_status |= STA_PPSSIGNAL;
1041 pps_valid = PPS_VALID;
1042
1043 /* when called for the first time,
1044 * just start the frequency interval */
1045 if (unlikely(pps_fbase.tv_sec == 0)) {
1046 pps_fbase = *raw_ts;
1047 return;
1048 }
1049
1050 /* ok, now we have a base for frequency calculation */
1051 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
1052
1053 /* check that the signal is in the range
1054 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
1055 if ((freq_norm.sec == 0) ||
1056 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1057 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1058 time_status |= STA_PPSJITTER;
1059 /* restart the frequency calibration interval */
1060 pps_fbase = *raw_ts;
1061 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1062 return;
1063 }
1064
1065 /* signal is ok */
1066
1067 /* check if the current frequency interval is finished */
1068 if (freq_norm.sec >= (1 << pps_shift)) {
1069 pps_calcnt++;
1070 /* restart the frequency calibration interval */
1071 pps_fbase = *raw_ts;
1072 hardpps_update_freq(freq_norm);
1073 }
1074
1075 hardpps_update_phase(pts_norm.nsec);
1076
1077}
1078#endif /* CONFIG_NTP_PPS */
1079
1080static int __init ntp_tick_adj_setup(char *str)
1081{
1082 int rc = kstrtos64(s: str, base: 0, res: &ntp_tick_adj);
1083 if (rc)
1084 return rc;
1085
1086 ntp_tick_adj <<= NTP_SCALE_SHIFT;
1087 return 1;
1088}
1089
1090__setup("ntp_tick_adj=", ntp_tick_adj_setup);
1091
1092void __init ntp_init(void)
1093{
1094 ntp_clear();
1095 ntp_init_cmos_sync();
1096}
1097

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