1 /*
2 * NTP state machine interfaces and logic.
3 *
4 * This code was mainly moved from kernel/timer.c and kernel/time.c
5 * Please see those files for relevant copyright info and historical
6 * changelogs.
7 */
8 #include <linux/capability.h>
9 #include <linux/clocksource.h>
10 #include <linux/workqueue.h>
11 #include <linux/hrtimer.h>
12 #include <linux/jiffies.h>
13 #include <linux/math64.h>
14 #include <linux/timex.h>
15 #include <linux/time.h>
16 #include <linux/mm.h>
17 #include <linux/module.h>
18
19 #include "tick-internal.h"
20
21 /*
22 * NTP timekeeping variables:
23 */
24
25 /* USER_HZ period (usecs): */
26 unsigned long tick_usec = TICK_USEC;
27
28 /* ACTHZ period (nsecs): */
29 unsigned long tick_nsec;
30
31 u64 tick_length;
32 static u64 tick_length_base;
33
34 static struct hrtimer leap_timer;
35
36 #define MAX_TICKADJ 500LL /* usecs */
37 #define MAX_TICKADJ_SCALED \
38 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
39
40 /*
41 * phase-lock loop variables
42 */
43
44 /*
45 * clock synchronization status
46 *
47 * (TIME_ERROR prevents overwriting the CMOS clock)
48 */
49 static int time_state = TIME_OK;
50
51 /* clock status bits: */
52 int time_status = STA_UNSYNC;
53
54 /* TAI offset (secs): */
55 static long time_tai;
56
57 /* time adjustment (nsecs): */
58 static s64 time_offset;
59
60 /* pll time constant: */
61 static long time_constant = 2;
62
63 /* maximum error (usecs): */
64 static long time_maxerror = NTP_PHASE_LIMIT;
65
66 /* estimated error (usecs): */
67 static long time_esterror = NTP_PHASE_LIMIT;
68
69 /* frequency offset (scaled nsecs/secs): */
70 static s64 time_freq;
71
72 /* time at last adjustment (secs): */
73 static long time_reftime;
74
75 static long time_adjust;
76
77 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */
78 static s64 ntp_tick_adj;
79
80 #ifdef CONFIG_NTP_PPS
81
82 /*
83 * The following variables are used when a pulse-per-second (PPS) signal
84 * is available. They establish the engineering parameters of the clock
85 * discipline loop when controlled by the PPS signal.
86 */
87 #define PPS_VALID 10 /* PPS signal watchdog max (s) */
88 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
89 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */
90 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */
91 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to
92 increase pps_shift or consecutive bad
93 intervals to decrease it */
94 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
95
96 static int pps_valid; /* signal watchdog counter */
97 static long pps_tf[3]; /* phase median filter */
98 static long pps_jitter; /* current jitter (ns) */
99 static struct timespec pps_fbase; /* beginning of the last freq interval */
100 static int pps_shift; /* current interval duration (s) (shift) */
101 static int pps_intcnt; /* interval counter */
102 static s64 pps_freq; /* frequency offset (scaled ns/s) */
103 static long pps_stabil; /* current stability (scaled ns/s) */
104
105 /*
106 * PPS signal quality monitors
107 */
108 static long pps_calcnt; /* calibration intervals */
109 static long pps_jitcnt; /* jitter limit exceeded */
110 static long pps_stbcnt; /* stability limit exceeded */
111 static long pps_errcnt; /* calibration errors */
112
113
114 /* PPS kernel consumer compensates the whole phase error immediately.
115 * Otherwise, reduce the offset by a fixed factor times the time constant.
116 */
ntp_offset_chunk(s64 offset)117 static inline s64 ntp_offset_chunk(s64 offset)
118 {
119 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
120 return offset;
121 else
122 return shift_right(offset, SHIFT_PLL + time_constant);
123 }
124
pps_reset_freq_interval(void)125 static inline void pps_reset_freq_interval(void)
126 {
127 /* the PPS calibration interval may end
128 surprisingly early */
129 pps_shift = PPS_INTMIN;
130 pps_intcnt = 0;
131 }
132
133 /**
134 * pps_clear - Clears the PPS state variables
135 *
136 * Must be called while holding a write on the xtime_lock
137 */
pps_clear(void)138 static inline void pps_clear(void)
139 {
140 pps_reset_freq_interval();
141 pps_tf[0] = 0;
142 pps_tf[1] = 0;
143 pps_tf[2] = 0;
144 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
145 pps_freq = 0;
146 }
147
148 /* Decrease pps_valid to indicate that another second has passed since
149 * the last PPS signal. When it reaches 0, indicate that PPS signal is
150 * missing.
151 *
152 * Must be called while holding a write on the xtime_lock
153 */
pps_dec_valid(void)154 static inline void pps_dec_valid(void)
155 {
156 if (pps_valid > 0)
157 pps_valid--;
158 else {
159 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
160 STA_PPSWANDER | STA_PPSERROR);
161 pps_clear();
162 }
163 }
164
pps_set_freq(s64 freq)165 static inline void pps_set_freq(s64 freq)
166 {
167 pps_freq = freq;
168 }
169
is_error_status(int status)170 static inline int is_error_status(int status)
171 {
172 return (time_status & (STA_UNSYNC|STA_CLOCKERR))
173 /* PPS signal lost when either PPS time or
174 * PPS frequency synchronization requested
175 */
176 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
177 && !(time_status & STA_PPSSIGNAL))
178 /* PPS jitter exceeded when
179 * PPS time synchronization requested */
180 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
181 == (STA_PPSTIME|STA_PPSJITTER))
182 /* PPS wander exceeded or calibration error when
183 * PPS frequency synchronization requested
184 */
185 || ((time_status & STA_PPSFREQ)
186 && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
187 }
188
pps_fill_timex(struct timex * txc)189 static inline void pps_fill_timex(struct timex *txc)
190 {
191 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
192 PPM_SCALE_INV, NTP_SCALE_SHIFT);
193 txc->jitter = pps_jitter;
194 if (!(time_status & STA_NANO))
195 txc->jitter /= NSEC_PER_USEC;
196 txc->shift = pps_shift;
197 txc->stabil = pps_stabil;
198 txc->jitcnt = pps_jitcnt;
199 txc->calcnt = pps_calcnt;
200 txc->errcnt = pps_errcnt;
201 txc->stbcnt = pps_stbcnt;
202 }
203
204 #else /* !CONFIG_NTP_PPS */
205
ntp_offset_chunk(s64 offset)206 static inline s64 ntp_offset_chunk(s64 offset)
207 {
208 return shift_right(offset, SHIFT_PLL + time_constant);
209 }
210
pps_reset_freq_interval(void)211 static inline void pps_reset_freq_interval(void) {}
pps_clear(void)212 static inline void pps_clear(void) {}
pps_dec_valid(void)213 static inline void pps_dec_valid(void) {}
pps_set_freq(s64 freq)214 static inline void pps_set_freq(s64 freq) {}
215
is_error_status(int status)216 static inline int is_error_status(int status)
217 {
218 return status & (STA_UNSYNC|STA_CLOCKERR);
219 }
220
pps_fill_timex(struct timex * txc)221 static inline void pps_fill_timex(struct timex *txc)
222 {
223 /* PPS is not implemented, so these are zero */
224 txc->ppsfreq = 0;
225 txc->jitter = 0;
226 txc->shift = 0;
227 txc->stabil = 0;
228 txc->jitcnt = 0;
229 txc->calcnt = 0;
230 txc->errcnt = 0;
231 txc->stbcnt = 0;
232 }
233
234 #endif /* CONFIG_NTP_PPS */
235
236 /*
237 * NTP methods:
238 */
239
240 /*
241 * Update (tick_length, tick_length_base, tick_nsec), based
242 * on (tick_usec, ntp_tick_adj, time_freq):
243 */
ntp_update_frequency(void)244 static void ntp_update_frequency(void)
245 {
246 u64 second_length;
247 u64 new_base;
248
249 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
250 << NTP_SCALE_SHIFT;
251
252 second_length += ntp_tick_adj;
253 second_length += time_freq;
254
255 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
256 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
257
258 /*
259 * Don't wait for the next second_overflow, apply
260 * the change to the tick length immediately:
261 */
262 tick_length += new_base - tick_length_base;
263 tick_length_base = new_base;
264 }
265
ntp_update_offset_fll(s64 offset64,long secs)266 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
267 {
268 time_status &= ~STA_MODE;
269
270 if (secs < MINSEC)
271 return 0;
272
273 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
274 return 0;
275
276 time_status |= STA_MODE;
277
278 return div_s64(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
279 }
280
ntp_update_offset(long offset)281 static void ntp_update_offset(long offset)
282 {
283 s64 freq_adj;
284 s64 offset64;
285 long secs;
286
287 if (!(time_status & STA_PLL))
288 return;
289
290 if (!(time_status & STA_NANO))
291 offset *= NSEC_PER_USEC;
292
293 /*
294 * Scale the phase adjustment and
295 * clamp to the operating range.
296 */
297 offset = min(offset, MAXPHASE);
298 offset = max(offset, -MAXPHASE);
299
300 /*
301 * Select how the frequency is to be controlled
302 * and in which mode (PLL or FLL).
303 */
304 secs = get_seconds() - time_reftime;
305 if (unlikely(time_status & STA_FREQHOLD))
306 secs = 0;
307
308 time_reftime = get_seconds();
309
310 offset64 = offset;
311 freq_adj = ntp_update_offset_fll(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 + time_constant)))
319 secs = 1 << (SHIFT_PLL + 1 + time_constant);
320
321 freq_adj += (offset64 * secs) <<
322 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
323
324 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
325
326 time_freq = max(freq_adj, -MAXFREQ_SCALED);
327
328 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
329 }
330
331 /**
332 * ntp_clear - Clears the NTP state variables
333 *
334 * Must be called while holding a write on the xtime_lock
335 */
ntp_clear(void)336 void ntp_clear(void)
337 {
338 time_adjust = 0; /* stop active adjtime() */
339 time_status |= STA_UNSYNC;
340 time_maxerror = NTP_PHASE_LIMIT;
341 time_esterror = NTP_PHASE_LIMIT;
342
343 ntp_update_frequency();
344
345 tick_length = tick_length_base;
346 time_offset = 0;
347
348 /* Clear PPS state variables */
349 pps_clear();
350 }
351
352 /*
353 * Leap second processing. If in leap-insert state at the end of the
354 * day, the system clock is set back one second; if in leap-delete
355 * state, the system clock is set ahead one second.
356 */
ntp_leap_second(struct hrtimer * timer)357 static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
358 {
359 enum hrtimer_restart res = HRTIMER_NORESTART;
360
361 write_seqlock(&xtime_lock);
362
363 switch (time_state) {
364 case TIME_OK:
365 break;
366 case TIME_INS:
367 timekeeping_leap_insert(-1);
368 time_state = TIME_OOP;
369 printk(KERN_NOTICE
370 "Clock: inserting leap second 23:59:60 UTC\n");
371 hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
372 res = HRTIMER_RESTART;
373 break;
374 case TIME_DEL:
375 timekeeping_leap_insert(1);
376 time_tai--;
377 time_state = TIME_WAIT;
378 printk(KERN_NOTICE
379 "Clock: deleting leap second 23:59:59 UTC\n");
380 break;
381 case TIME_OOP:
382 time_tai++;
383 time_state = TIME_WAIT;
384 /* fall through */
385 case TIME_WAIT:
386 if (!(time_status & (STA_INS | STA_DEL)))
387 time_state = TIME_OK;
388 break;
389 }
390
391 write_sequnlock(&xtime_lock);
392
393 return res;
394 }
395
396 /*
397 * this routine handles the overflow of the microsecond field
398 *
399 * The tricky bits of code to handle the accurate clock support
400 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
401 * They were originally developed for SUN and DEC kernels.
402 * All the kudos should go to Dave for this stuff.
403 */
second_overflow(void)404 void second_overflow(void)
405 {
406 s64 delta;
407
408 /* Bump the maxerror field */
409 time_maxerror += MAXFREQ / NSEC_PER_USEC;
410 if (time_maxerror > NTP_PHASE_LIMIT) {
411 time_maxerror = NTP_PHASE_LIMIT;
412 time_status |= STA_UNSYNC;
413 }
414
415 /* Compute the phase adjustment for the next second */
416 tick_length = tick_length_base;
417
418 delta = ntp_offset_chunk(time_offset);
419 time_offset -= delta;
420 tick_length += delta;
421
422 /* Check PPS signal */
423 pps_dec_valid();
424
425 if (!time_adjust)
426 return;
427
428 if (time_adjust > MAX_TICKADJ) {
429 time_adjust -= MAX_TICKADJ;
430 tick_length += MAX_TICKADJ_SCALED;
431 return;
432 }
433
434 if (time_adjust < -MAX_TICKADJ) {
435 time_adjust += MAX_TICKADJ;
436 tick_length -= MAX_TICKADJ_SCALED;
437 return;
438 }
439
440 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
441 << NTP_SCALE_SHIFT;
442 time_adjust = 0;
443 }
444
445 #ifdef CONFIG_GENERIC_CMOS_UPDATE
446
447 /* Disable the cmos update - used by virtualization and embedded */
448 int no_sync_cmos_clock __read_mostly;
449
450 static void sync_cmos_clock(struct work_struct *work);
451
452 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
453
sync_cmos_clock(struct work_struct * work)454 static void sync_cmos_clock(struct work_struct *work)
455 {
456 struct timespec now, next;
457 int fail = 1;
458
459 /*
460 * If we have an externally synchronized Linux clock, then update
461 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
462 * called as close as possible to 500 ms before the new second starts.
463 * This code is run on a timer. If the clock is set, that timer
464 * may not expire at the correct time. Thus, we adjust...
465 */
466 if (!ntp_synced()) {
467 /*
468 * Not synced, exit, do not restart a timer (if one is
469 * running, let it run out).
470 */
471 return;
472 }
473
474 getnstimeofday(&now);
475 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
476 fail = update_persistent_clock(now);
477
478 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
479 if (next.tv_nsec <= 0)
480 next.tv_nsec += NSEC_PER_SEC;
481
482 if (!fail)
483 next.tv_sec = 659;
484 else
485 next.tv_sec = 0;
486
487 if (next.tv_nsec >= NSEC_PER_SEC) {
488 next.tv_sec++;
489 next.tv_nsec -= NSEC_PER_SEC;
490 }
491 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
492 }
493
notify_cmos_timer(void)494 static void notify_cmos_timer(void)
495 {
496 if (!no_sync_cmos_clock)
497 schedule_delayed_work(&sync_cmos_work, 0);
498 }
499
500 #else
notify_cmos_timer(void)501 static inline void notify_cmos_timer(void) { }
502 #endif
503
504 /*
505 * Start the leap seconds timer:
506 */
ntp_start_leap_timer(struct timespec * ts)507 static inline void ntp_start_leap_timer(struct timespec *ts)
508 {
509 long now = ts->tv_sec;
510
511 if (time_status & STA_INS) {
512 time_state = TIME_INS;
513 now += 86400 - now % 86400;
514 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
515
516 return;
517 }
518
519 if (time_status & STA_DEL) {
520 time_state = TIME_DEL;
521 now += 86400 - (now + 1) % 86400;
522 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
523 }
524 }
525
526 /*
527 * Propagate a new txc->status value into the NTP state:
528 */
process_adj_status(struct timex * txc,struct timespec * ts)529 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
530 {
531 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
532 time_state = TIME_OK;
533 time_status = STA_UNSYNC;
534 /* restart PPS frequency calibration */
535 pps_reset_freq_interval();
536 }
537
538 /*
539 * If we turn on PLL adjustments then reset the
540 * reference time to current time.
541 */
542 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
543 time_reftime = get_seconds();
544
545 /* only set allowed bits */
546 time_status &= STA_RONLY;
547 time_status |= txc->status & ~STA_RONLY;
548
549 switch (time_state) {
550 case TIME_OK:
551 ntp_start_leap_timer(ts);
552 break;
553 case TIME_INS:
554 case TIME_DEL:
555 time_state = TIME_OK;
556 ntp_start_leap_timer(ts);
557 case TIME_WAIT:
558 if (!(time_status & (STA_INS | STA_DEL)))
559 time_state = TIME_OK;
560 break;
561 case TIME_OOP:
562 hrtimer_restart(&leap_timer);
563 break;
564 }
565 }
566 /*
567 * Called with the xtime lock held, so we can access and modify
568 * all the global NTP state:
569 */
process_adjtimex_modes(struct timex * txc,struct timespec * ts)570 static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
571 {
572 if (txc->modes & ADJ_STATUS)
573 process_adj_status(txc, ts);
574
575 if (txc->modes & ADJ_NANO)
576 time_status |= STA_NANO;
577
578 if (txc->modes & ADJ_MICRO)
579 time_status &= ~STA_NANO;
580
581 if (txc->modes & ADJ_FREQUENCY) {
582 time_freq = txc->freq * PPM_SCALE;
583 time_freq = min(time_freq, MAXFREQ_SCALED);
584 time_freq = max(time_freq, -MAXFREQ_SCALED);
585 /* update pps_freq */
586 pps_set_freq(time_freq);
587 }
588
589 if (txc->modes & ADJ_MAXERROR)
590 time_maxerror = txc->maxerror;
591
592 if (txc->modes & ADJ_ESTERROR)
593 time_esterror = txc->esterror;
594
595 if (txc->modes & ADJ_TIMECONST) {
596 time_constant = txc->constant;
597 if (!(time_status & STA_NANO))
598 time_constant += 4;
599 time_constant = min(time_constant, (long)MAXTC);
600 time_constant = max(time_constant, 0l);
601 }
602
603 if (txc->modes & ADJ_TAI && txc->constant > 0)
604 time_tai = txc->constant;
605
606 if (txc->modes & ADJ_OFFSET)
607 ntp_update_offset(txc->offset);
608
609 if (txc->modes & ADJ_TICK)
610 tick_usec = txc->tick;
611
612 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
613 ntp_update_frequency();
614 }
615
616 /*
617 * adjtimex mainly allows reading (and writing, if superuser) of
618 * kernel time-keeping variables. used by xntpd.
619 */
do_adjtimex(struct timex * txc)620 int do_adjtimex(struct timex *txc)
621 {
622 struct timespec ts;
623 int result;
624
625 /* Validate the data before disabling interrupts */
626 if (txc->modes & ADJ_ADJTIME) {
627 /* singleshot must not be used with any other mode bits */
628 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
629 return -EINVAL;
630 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
631 !capable(CAP_SYS_TIME))
632 return -EPERM;
633 } else {
634 /* In order to modify anything, you gotta be super-user! */
635 if (txc->modes && !capable(CAP_SYS_TIME))
636 return -EPERM;
637
638 /*
639 * if the quartz is off by more than 10% then
640 * something is VERY wrong!
641 */
642 if (txc->modes & ADJ_TICK &&
643 (txc->tick < 900000/USER_HZ ||
644 txc->tick > 1100000/USER_HZ))
645 return -EINVAL;
646
647 if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
648 hrtimer_cancel(&leap_timer);
649 }
650
651 if (txc->modes & ADJ_SETOFFSET) {
652 struct timespec delta;
653 delta.tv_sec = txc->time.tv_sec;
654 delta.tv_nsec = txc->time.tv_usec;
655 if (!capable(CAP_SYS_TIME))
656 return -EPERM;
657 if (!(txc->modes & ADJ_NANO))
658 delta.tv_nsec *= 1000;
659 result = timekeeping_inject_offset(&delta);
660 if (result)
661 return result;
662 }
663
664 getnstimeofday(&ts);
665
666 write_seqlock_irq(&xtime_lock);
667
668 if (txc->modes & ADJ_ADJTIME) {
669 long save_adjust = time_adjust;
670
671 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
672 /* adjtime() is independent from ntp_adjtime() */
673 time_adjust = txc->offset;
674 ntp_update_frequency();
675 }
676 txc->offset = save_adjust;
677 } else {
678
679 /* If there are input parameters, then process them: */
680 if (txc->modes)
681 process_adjtimex_modes(txc, &ts);
682
683 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
684 NTP_SCALE_SHIFT);
685 if (!(time_status & STA_NANO))
686 txc->offset /= NSEC_PER_USEC;
687 }
688
689 result = time_state; /* mostly `TIME_OK' */
690 /* check for errors */
691 if (is_error_status(time_status))
692 result = TIME_ERROR;
693
694 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
695 PPM_SCALE_INV, NTP_SCALE_SHIFT);
696 txc->maxerror = time_maxerror;
697 txc->esterror = time_esterror;
698 txc->status = time_status;
699 txc->constant = time_constant;
700 txc->precision = 1;
701 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
702 txc->tick = tick_usec;
703 txc->tai = time_tai;
704
705 /* fill PPS status fields */
706 pps_fill_timex(txc);
707
708 write_sequnlock_irq(&xtime_lock);
709
710 txc->time.tv_sec = ts.tv_sec;
711 txc->time.tv_usec = ts.tv_nsec;
712 if (!(time_status & STA_NANO))
713 txc->time.tv_usec /= NSEC_PER_USEC;
714
715 notify_cmos_timer();
716
717 return result;
718 }
719
720 #ifdef CONFIG_NTP_PPS
721
722 /* actually struct pps_normtime is good old struct timespec, but it is
723 * semantically different (and it is the reason why it was invented):
724 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
725 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
726 struct pps_normtime {
727 __kernel_time_t sec; /* seconds */
728 long nsec; /* nanoseconds */
729 };
730
731 /* normalize the timestamp so that nsec is in the
732 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
pps_normalize_ts(struct timespec ts)733 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
734 {
735 struct pps_normtime norm = {
736 .sec = ts.tv_sec,
737 .nsec = ts.tv_nsec
738 };
739
740 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
741 norm.nsec -= NSEC_PER_SEC;
742 norm.sec++;
743 }
744
745 return norm;
746 }
747
748 /* get current phase correction and jitter */
pps_phase_filter_get(long * jitter)749 static inline long pps_phase_filter_get(long *jitter)
750 {
751 *jitter = pps_tf[0] - pps_tf[1];
752 if (*jitter < 0)
753 *jitter = -*jitter;
754
755 /* TODO: test various filters */
756 return pps_tf[0];
757 }
758
759 /* add the sample to the phase filter */
pps_phase_filter_add(long err)760 static inline void pps_phase_filter_add(long err)
761 {
762 pps_tf[2] = pps_tf[1];
763 pps_tf[1] = pps_tf[0];
764 pps_tf[0] = err;
765 }
766
767 /* decrease frequency calibration interval length.
768 * It is halved after four consecutive unstable intervals.
769 */
pps_dec_freq_interval(void)770 static inline void pps_dec_freq_interval(void)
771 {
772 if (--pps_intcnt <= -PPS_INTCOUNT) {
773 pps_intcnt = -PPS_INTCOUNT;
774 if (pps_shift > PPS_INTMIN) {
775 pps_shift--;
776 pps_intcnt = 0;
777 }
778 }
779 }
780
781 /* increase frequency calibration interval length.
782 * It is doubled after four consecutive stable intervals.
783 */
pps_inc_freq_interval(void)784 static inline void pps_inc_freq_interval(void)
785 {
786 if (++pps_intcnt >= PPS_INTCOUNT) {
787 pps_intcnt = PPS_INTCOUNT;
788 if (pps_shift < PPS_INTMAX) {
789 pps_shift++;
790 pps_intcnt = 0;
791 }
792 }
793 }
794
795 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
796 * timestamps
797 *
798 * At the end of the calibration interval the difference between the
799 * first and last MONOTONIC_RAW clock timestamps divided by the length
800 * of the interval becomes the frequency update. If the interval was
801 * too long, the data are discarded.
802 * Returns the difference between old and new frequency values.
803 */
hardpps_update_freq(struct pps_normtime freq_norm)804 static long hardpps_update_freq(struct pps_normtime freq_norm)
805 {
806 long delta, delta_mod;
807 s64 ftemp;
808
809 /* check if the frequency interval was too long */
810 if (freq_norm.sec > (2 << pps_shift)) {
811 time_status |= STA_PPSERROR;
812 pps_errcnt++;
813 pps_dec_freq_interval();
814 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
815 freq_norm.sec);
816 return 0;
817 }
818
819 /* here the raw frequency offset and wander (stability) is
820 * calculated. If the wander is less than the wander threshold
821 * the interval is increased; otherwise it is decreased.
822 */
823 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
824 freq_norm.sec);
825 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
826 pps_freq = ftemp;
827 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
828 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
829 time_status |= STA_PPSWANDER;
830 pps_stbcnt++;
831 pps_dec_freq_interval();
832 } else { /* good sample */
833 pps_inc_freq_interval();
834 }
835
836 /* the stability metric is calculated as the average of recent
837 * frequency changes, but is used only for performance
838 * monitoring
839 */
840 delta_mod = delta;
841 if (delta_mod < 0)
842 delta_mod = -delta_mod;
843 pps_stabil += (div_s64(((s64)delta_mod) <<
844 (NTP_SCALE_SHIFT - SHIFT_USEC),
845 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
846
847 /* if enabled, the system clock frequency is updated */
848 if ((time_status & STA_PPSFREQ) != 0 &&
849 (time_status & STA_FREQHOLD) == 0) {
850 time_freq = pps_freq;
851 ntp_update_frequency();
852 }
853
854 return delta;
855 }
856
857 /* correct REALTIME clock phase error against PPS signal */
hardpps_update_phase(long error)858 static void hardpps_update_phase(long error)
859 {
860 long correction = -error;
861 long jitter;
862
863 /* add the sample to the median filter */
864 pps_phase_filter_add(correction);
865 correction = pps_phase_filter_get(&jitter);
866
867 /* Nominal jitter is due to PPS signal noise. If it exceeds the
868 * threshold, the sample is discarded; otherwise, if so enabled,
869 * the time offset is updated.
870 */
871 if (jitter > (pps_jitter << PPS_POPCORN)) {
872 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
873 jitter, (pps_jitter << PPS_POPCORN));
874 time_status |= STA_PPSJITTER;
875 pps_jitcnt++;
876 } else if (time_status & STA_PPSTIME) {
877 /* correct the time using the phase offset */
878 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
879 NTP_INTERVAL_FREQ);
880 /* cancel running adjtime() */
881 time_adjust = 0;
882 }
883 /* update jitter */
884 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
885 }
886
887 /*
888 * hardpps() - discipline CPU clock oscillator to external PPS signal
889 *
890 * This routine is called at each PPS signal arrival in order to
891 * discipline the CPU clock oscillator to the PPS signal. It takes two
892 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
893 * is used to correct clock phase error and the latter is used to
894 * correct the frequency.
895 *
896 * This code is based on David Mills's reference nanokernel
897 * implementation. It was mostly rewritten but keeps the same idea.
898 */
hardpps(const struct timespec * phase_ts,const struct timespec * raw_ts)899 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
900 {
901 struct pps_normtime pts_norm, freq_norm;
902 unsigned long flags;
903
904 pts_norm = pps_normalize_ts(*phase_ts);
905
906 write_seqlock_irqsave(&xtime_lock, flags);
907
908 /* clear the error bits, they will be set again if needed */
909 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
910
911 /* indicate signal presence */
912 time_status |= STA_PPSSIGNAL;
913 pps_valid = PPS_VALID;
914
915 /* when called for the first time,
916 * just start the frequency interval */
917 if (unlikely(pps_fbase.tv_sec == 0)) {
918 pps_fbase = *raw_ts;
919 write_sequnlock_irqrestore(&xtime_lock, flags);
920 return;
921 }
922
923 /* ok, now we have a base for frequency calculation */
924 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
925
926 /* check that the signal is in the range
927 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
928 if ((freq_norm.sec == 0) ||
929 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
930 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
931 time_status |= STA_PPSJITTER;
932 /* restart the frequency calibration interval */
933 pps_fbase = *raw_ts;
934 write_sequnlock_irqrestore(&xtime_lock, flags);
935 pr_err("hardpps: PPSJITTER: bad pulse\n");
936 return;
937 }
938
939 /* signal is ok */
940
941 /* check if the current frequency interval is finished */
942 if (freq_norm.sec >= (1 << pps_shift)) {
943 pps_calcnt++;
944 /* restart the frequency calibration interval */
945 pps_fbase = *raw_ts;
946 hardpps_update_freq(freq_norm);
947 }
948
949 hardpps_update_phase(pts_norm.nsec);
950
951 write_sequnlock_irqrestore(&xtime_lock, flags);
952 }
953 EXPORT_SYMBOL(hardpps);
954
955 #endif /* CONFIG_NTP_PPS */
956
ntp_tick_adj_setup(char * str)957 static int __init ntp_tick_adj_setup(char *str)
958 {
959 ntp_tick_adj = simple_strtol(str, NULL, 0);
960 ntp_tick_adj <<= NTP_SCALE_SHIFT;
961
962 return 1;
963 }
964
965 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
966
ntp_init(void)967 void __init ntp_init(void)
968 {
969 ntp_clear();
970 hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
971 leap_timer.function = ntp_leap_second;
972 }
973