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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): */
26unsigned long tick_usec = TICK_USEC;
27
28/* ACTHZ period (nsecs): */
29unsigned long tick_nsec;
30
31u64 tick_length;
32static u64 tick_length_base;
33
34static 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 */
49static int time_state = TIME_OK;
50
51/* clock status bits: */
52int time_status = STA_UNSYNC;
53
54/* TAI offset (secs): */
55static long time_tai;
56
57/* time adjustment (nsecs): */
58static s64 time_offset;
59
60/* pll time constant: */
61static long time_constant = 2;
62
63/* maximum error (usecs): */
64static long time_maxerror = NTP_PHASE_LIMIT;
65
66/* estimated error (usecs): */
67static long time_esterror = NTP_PHASE_LIMIT;
68
69/* frequency offset (scaled nsecs/secs): */
70static s64 time_freq;
71
72/* time at last adjustment (secs): */
73static long time_reftime;
74
75static long time_adjust;
76
77/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
78static 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
96static int pps_valid; /* signal watchdog counter */
97static long pps_tf[3]; /* phase median filter */
98static long pps_jitter; /* current jitter (ns) */
99static struct timespec pps_fbase; /* beginning of the last freq interval */
100static int pps_shift; /* current interval duration (s) (shift) */
101static int pps_intcnt; /* interval counter */
102static s64 pps_freq; /* frequency offset (scaled ns/s) */
103static long pps_stabil; /* current stability (scaled ns/s) */
104
105/*
106 * PPS signal quality monitors
107 */
108static long pps_calcnt; /* calibration intervals */
109static long pps_jitcnt; /* jitter limit exceeded */
110static long pps_stbcnt; /* stability limit exceeded */
111static 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 */
117static 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
125static 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 */
138static 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 */
154static 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
165static inline void pps_set_freq(s64 freq)
166{
167 pps_freq = freq;
168}
169
170static 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
189static 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
206static inline s64 ntp_offset_chunk(s64 offset)
207{
208 return shift_right(offset, SHIFT_PLL + time_constant);
209}
210
211static inline void pps_reset_freq_interval(void) {}
212static inline void pps_clear(void) {}
213static inline void pps_dec_valid(void) {}
214static inline void pps_set_freq(s64 freq) {}
215
216static inline int is_error_status(int status)
217{
218 return status & (STA_UNSYNC|STA_CLOCKERR);
219}
220
221static 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 */
244static 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
266static 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
281static 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 */
336void 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 */
357static 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 */
404void 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 */
448int no_sync_cmos_clock __read_mostly;
449
450static void sync_cmos_clock(struct work_struct *work);
451
452static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
453
454static 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
494static void notify_cmos_timer(void)
495{
496 if (!no_sync_cmos_clock)
497 schedule_delayed_work(&sync_cmos_work, 0);
498}
499
500#else
501static inline void notify_cmos_timer(void) { }
502#endif
503
504/*
505 * Start the leap seconds timer:
506 */
507static 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 */
529static 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 */
570static 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 */
620int 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) */
726struct 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 */
733static 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 */
749static 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 */
760static 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 */
770static 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 */
784static 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 */
804static 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 */
858static 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 */
899void 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}
953EXPORT_SYMBOL(hardpps);
954
955#endif /* CONFIG_NTP_PPS */
956
957static 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
967void __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}
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
25DEFINE_SPINLOCK(ntp_lock);
26
27
28/* USER_HZ period (usecs): */
29unsigned long tick_usec = TICK_USEC;
30
31/* ACTHZ period (nsecs): */
32unsigned long tick_nsec;
33
34static u64 tick_length;
35static u64 tick_length_base;
36
37#define MAX_TICKADJ 500LL /* usecs */
38#define MAX_TICKADJ_SCALED \
39 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
40
41/*
42 * phase-lock loop variables
43 */
44
45/*
46 * clock synchronization status
47 *
48 * (TIME_ERROR prevents overwriting the CMOS clock)
49 */
50static int time_state = TIME_OK;
51
52/* clock status bits: */
53static int time_status = STA_UNSYNC;
54
55/* TAI offset (secs): */
56static long time_tai;
57
58/* time adjustment (nsecs): */
59static s64 time_offset;
60
61/* pll time constant: */
62static long time_constant = 2;
63
64/* maximum error (usecs): */
65static long time_maxerror = NTP_PHASE_LIMIT;
66
67/* estimated error (usecs): */
68static long time_esterror = NTP_PHASE_LIMIT;
69
70/* frequency offset (scaled nsecs/secs): */
71static s64 time_freq;
72
73/* time at last adjustment (secs): */
74static long time_reftime;
75
76static long time_adjust;
77
78/* constant (boot-param configurable) NTP tick adjustment (upscaled) */
79static s64 ntp_tick_adj;
80
81#ifdef CONFIG_NTP_PPS
82
83/*
84 * The following variables are used when a pulse-per-second (PPS) signal
85 * is available. They establish the engineering parameters of the clock
86 * discipline loop when controlled by the PPS signal.
87 */
88#define PPS_VALID 10 /* PPS signal watchdog max (s) */
89#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */
90#define PPS_INTMIN 2 /* min freq interval (s) (shift) */
91#define PPS_INTMAX 8 /* max freq interval (s) (shift) */
92#define PPS_INTCOUNT 4 /* number of consecutive good intervals to
93 increase pps_shift or consecutive bad
94 intervals to decrease it */
95#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */
96
97static int pps_valid; /* signal watchdog counter */
98static long pps_tf[3]; /* phase median filter */
99static long pps_jitter; /* current jitter (ns) */
100static struct timespec pps_fbase; /* beginning of the last freq interval */
101static int pps_shift; /* current interval duration (s) (shift) */
102static int pps_intcnt; /* interval counter */
103static s64 pps_freq; /* frequency offset (scaled ns/s) */
104static long pps_stabil; /* current stability (scaled ns/s) */
105
106/*
107 * PPS signal quality monitors
108 */
109static long pps_calcnt; /* calibration intervals */
110static long pps_jitcnt; /* jitter limit exceeded */
111static long pps_stbcnt; /* stability limit exceeded */
112static long pps_errcnt; /* calibration errors */
113
114
115/* PPS kernel consumer compensates the whole phase error immediately.
116 * Otherwise, reduce the offset by a fixed factor times the time constant.
117 */
118static inline s64 ntp_offset_chunk(s64 offset)
119{
120 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
121 return offset;
122 else
123 return shift_right(offset, SHIFT_PLL + time_constant);
124}
125
126static inline void pps_reset_freq_interval(void)
127{
128 /* the PPS calibration interval may end
129 surprisingly early */
130 pps_shift = PPS_INTMIN;
131 pps_intcnt = 0;
132}
133
134/**
135 * pps_clear - Clears the PPS state variables
136 *
137 * Must be called while holding a write on the ntp_lock
138 */
139static inline void pps_clear(void)
140{
141 pps_reset_freq_interval();
142 pps_tf[0] = 0;
143 pps_tf[1] = 0;
144 pps_tf[2] = 0;
145 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
146 pps_freq = 0;
147}
148
149/* Decrease pps_valid to indicate that another second has passed since
150 * the last PPS signal. When it reaches 0, indicate that PPS signal is
151 * missing.
152 *
153 * Must be called while holding a write on the ntp_lock
154 */
155static inline void pps_dec_valid(void)
156{
157 if (pps_valid > 0)
158 pps_valid--;
159 else {
160 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
161 STA_PPSWANDER | STA_PPSERROR);
162 pps_clear();
163 }
164}
165
166static inline void pps_set_freq(s64 freq)
167{
168 pps_freq = freq;
169}
170
171static inline int is_error_status(int status)
172{
173 return (time_status & (STA_UNSYNC|STA_CLOCKERR))
174 /* PPS signal lost when either PPS time or
175 * PPS frequency synchronization requested
176 */
177 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
178 && !(time_status & STA_PPSSIGNAL))
179 /* PPS jitter exceeded when
180 * PPS time synchronization requested */
181 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
182 == (STA_PPSTIME|STA_PPSJITTER))
183 /* PPS wander exceeded or calibration error when
184 * PPS frequency synchronization requested
185 */
186 || ((time_status & STA_PPSFREQ)
187 && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
188}
189
190static inline void pps_fill_timex(struct timex *txc)
191{
192 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
193 PPM_SCALE_INV, NTP_SCALE_SHIFT);
194 txc->jitter = pps_jitter;
195 if (!(time_status & STA_NANO))
196 txc->jitter /= NSEC_PER_USEC;
197 txc->shift = pps_shift;
198 txc->stabil = pps_stabil;
199 txc->jitcnt = pps_jitcnt;
200 txc->calcnt = pps_calcnt;
201 txc->errcnt = pps_errcnt;
202 txc->stbcnt = pps_stbcnt;
203}
204
205#else /* !CONFIG_NTP_PPS */
206
207static inline s64 ntp_offset_chunk(s64 offset)
208{
209 return shift_right(offset, SHIFT_PLL + time_constant);
210}
211
212static inline void pps_reset_freq_interval(void) {}
213static inline void pps_clear(void) {}
214static inline void pps_dec_valid(void) {}
215static inline void pps_set_freq(s64 freq) {}
216
217static inline int is_error_status(int status)
218{
219 return status & (STA_UNSYNC|STA_CLOCKERR);
220}
221
222static inline void pps_fill_timex(struct timex *txc)
223{
224 /* PPS is not implemented, so these are zero */
225 txc->ppsfreq = 0;
226 txc->jitter = 0;
227 txc->shift = 0;
228 txc->stabil = 0;
229 txc->jitcnt = 0;
230 txc->calcnt = 0;
231 txc->errcnt = 0;
232 txc->stbcnt = 0;
233}
234
235#endif /* CONFIG_NTP_PPS */
236
237
238/**
239 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
240 *
241 */
242static inline int ntp_synced(void)
243{
244 return !(time_status & STA_UNSYNC);
245}
246
247
248/*
249 * NTP methods:
250 */
251
252/*
253 * Update (tick_length, tick_length_base, tick_nsec), based
254 * on (tick_usec, ntp_tick_adj, time_freq):
255 */
256static void ntp_update_frequency(void)
257{
258 u64 second_length;
259 u64 new_base;
260
261 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
262 << NTP_SCALE_SHIFT;
263
264 second_length += ntp_tick_adj;
265 second_length += time_freq;
266
267 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
268 new_base = div_u64(second_length, NTP_INTERVAL_FREQ);
269
270 /*
271 * Don't wait for the next second_overflow, apply
272 * the change to the tick length immediately:
273 */
274 tick_length += new_base - tick_length_base;
275 tick_length_base = new_base;
276}
277
278static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
279{
280 time_status &= ~STA_MODE;
281
282 if (secs < MINSEC)
283 return 0;
284
285 if (!(time_status & STA_FLL) && (secs <= MAXSEC))
286 return 0;
287
288 time_status |= STA_MODE;
289
290 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
291}
292
293static void ntp_update_offset(long offset)
294{
295 s64 freq_adj;
296 s64 offset64;
297 long secs;
298
299 if (!(time_status & STA_PLL))
300 return;
301
302 if (!(time_status & STA_NANO))
303 offset *= NSEC_PER_USEC;
304
305 /*
306 * Scale the phase adjustment and
307 * clamp to the operating range.
308 */
309 offset = min(offset, MAXPHASE);
310 offset = max(offset, -MAXPHASE);
311
312 /*
313 * Select how the frequency is to be controlled
314 * and in which mode (PLL or FLL).
315 */
316 secs = get_seconds() - time_reftime;
317 if (unlikely(time_status & STA_FREQHOLD))
318 secs = 0;
319
320 time_reftime = get_seconds();
321
322 offset64 = offset;
323 freq_adj = ntp_update_offset_fll(offset64, secs);
324
325 /*
326 * Clamp update interval to reduce PLL gain with low
327 * sampling rate (e.g. intermittent network connection)
328 * to avoid instability.
329 */
330 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
331 secs = 1 << (SHIFT_PLL + 1 + time_constant);
332
333 freq_adj += (offset64 * secs) <<
334 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
335
336 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED);
337
338 time_freq = max(freq_adj, -MAXFREQ_SCALED);
339
340 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
341}
342
343/**
344 * ntp_clear - Clears the NTP state variables
345 */
346void ntp_clear(void)
347{
348 unsigned long flags;
349
350 spin_lock_irqsave(&ntp_lock, flags);
351
352 time_adjust = 0; /* stop active adjtime() */
353 time_status |= STA_UNSYNC;
354 time_maxerror = NTP_PHASE_LIMIT;
355 time_esterror = NTP_PHASE_LIMIT;
356
357 ntp_update_frequency();
358
359 tick_length = tick_length_base;
360 time_offset = 0;
361
362 /* Clear PPS state variables */
363 pps_clear();
364 spin_unlock_irqrestore(&ntp_lock, flags);
365
366}
367
368
369u64 ntp_tick_length(void)
370{
371 unsigned long flags;
372 s64 ret;
373
374 spin_lock_irqsave(&ntp_lock, flags);
375 ret = tick_length;
376 spin_unlock_irqrestore(&ntp_lock, flags);
377 return ret;
378}
379
380
381/*
382 * this routine handles the overflow of the microsecond field
383 *
384 * The tricky bits of code to handle the accurate clock support
385 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
386 * They were originally developed for SUN and DEC kernels.
387 * All the kudos should go to Dave for this stuff.
388 *
389 * Also handles leap second processing, and returns leap offset
390 */
391int second_overflow(unsigned long secs)
392{
393 s64 delta;
394 int leap = 0;
395 unsigned long flags;
396
397 spin_lock_irqsave(&ntp_lock, flags);
398
399 /*
400 * Leap second processing. If in leap-insert state at the end of the
401 * day, the system clock is set back one second; if in leap-delete
402 * state, the system clock is set ahead one second.
403 */
404 switch (time_state) {
405 case TIME_OK:
406 if (time_status & STA_INS)
407 time_state = TIME_INS;
408 else if (time_status & STA_DEL)
409 time_state = TIME_DEL;
410 break;
411 case TIME_INS:
412 if (!(time_status & STA_INS))
413 time_state = TIME_OK;
414 else if (secs % 86400 == 0) {
415 leap = -1;
416 time_state = TIME_OOP;
417 time_tai++;
418 printk(KERN_NOTICE
419 "Clock: inserting leap second 23:59:60 UTC\n");
420 }
421 break;
422 case TIME_DEL:
423 if (!(time_status & STA_DEL))
424 time_state = TIME_OK;
425 else if ((secs + 1) % 86400 == 0) {
426 leap = 1;
427 time_tai--;
428 time_state = TIME_WAIT;
429 printk(KERN_NOTICE
430 "Clock: deleting leap second 23:59:59 UTC\n");
431 }
432 break;
433 case TIME_OOP:
434 time_state = TIME_WAIT;
435 break;
436
437 case TIME_WAIT:
438 if (!(time_status & (STA_INS | STA_DEL)))
439 time_state = TIME_OK;
440 break;
441 }
442
443
444 /* Bump the maxerror field */
445 time_maxerror += MAXFREQ / NSEC_PER_USEC;
446 if (time_maxerror > NTP_PHASE_LIMIT) {
447 time_maxerror = NTP_PHASE_LIMIT;
448 time_status |= STA_UNSYNC;
449 }
450
451 /* Compute the phase adjustment for the next second */
452 tick_length = tick_length_base;
453
454 delta = ntp_offset_chunk(time_offset);
455 time_offset -= delta;
456 tick_length += delta;
457
458 /* Check PPS signal */
459 pps_dec_valid();
460
461 if (!time_adjust)
462 goto out;
463
464 if (time_adjust > MAX_TICKADJ) {
465 time_adjust -= MAX_TICKADJ;
466 tick_length += MAX_TICKADJ_SCALED;
467 goto out;
468 }
469
470 if (time_adjust < -MAX_TICKADJ) {
471 time_adjust += MAX_TICKADJ;
472 tick_length -= MAX_TICKADJ_SCALED;
473 goto out;
474 }
475
476 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
477 << NTP_SCALE_SHIFT;
478 time_adjust = 0;
479
480out:
481 spin_unlock_irqrestore(&ntp_lock, flags);
482
483 return leap;
484}
485
486#ifdef CONFIG_GENERIC_CMOS_UPDATE
487
488static void sync_cmos_clock(struct work_struct *work);
489
490static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
491
492static void sync_cmos_clock(struct work_struct *work)
493{
494 struct timespec now, next;
495 int fail = 1;
496
497 /*
498 * If we have an externally synchronized Linux clock, then update
499 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
500 * called as close as possible to 500 ms before the new second starts.
501 * This code is run on a timer. If the clock is set, that timer
502 * may not expire at the correct time. Thus, we adjust...
503 */
504 if (!ntp_synced()) {
505 /*
506 * Not synced, exit, do not restart a timer (if one is
507 * running, let it run out).
508 */
509 return;
510 }
511
512 getnstimeofday(&now);
513 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
514 fail = update_persistent_clock(now);
515
516 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
517 if (next.tv_nsec <= 0)
518 next.tv_nsec += NSEC_PER_SEC;
519
520 if (!fail)
521 next.tv_sec = 659;
522 else
523 next.tv_sec = 0;
524
525 if (next.tv_nsec >= NSEC_PER_SEC) {
526 next.tv_sec++;
527 next.tv_nsec -= NSEC_PER_SEC;
528 }
529 schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
530}
531
532static void notify_cmos_timer(void)
533{
534 schedule_delayed_work(&sync_cmos_work, 0);
535}
536
537#else
538static inline void notify_cmos_timer(void) { }
539#endif
540
541
542/*
543 * Propagate a new txc->status value into the NTP state:
544 */
545static inline void process_adj_status(struct timex *txc, struct timespec *ts)
546{
547 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
548 time_state = TIME_OK;
549 time_status = STA_UNSYNC;
550 /* restart PPS frequency calibration */
551 pps_reset_freq_interval();
552 }
553
554 /*
555 * If we turn on PLL adjustments then reset the
556 * reference time to current time.
557 */
558 if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
559 time_reftime = get_seconds();
560
561 /* only set allowed bits */
562 time_status &= STA_RONLY;
563 time_status |= txc->status & ~STA_RONLY;
564}
565
566/*
567 * Called with ntp_lock held, so we can access and modify
568 * all the global NTP state:
569 */
570static 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 */
620int 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
648 if (txc->modes & ADJ_SETOFFSET) {
649 struct timespec delta;
650 delta.tv_sec = txc->time.tv_sec;
651 delta.tv_nsec = txc->time.tv_usec;
652 if (!capable(CAP_SYS_TIME))
653 return -EPERM;
654 if (!(txc->modes & ADJ_NANO))
655 delta.tv_nsec *= 1000;
656 result = timekeeping_inject_offset(&delta);
657 if (result)
658 return result;
659 }
660
661 getnstimeofday(&ts);
662
663 spin_lock_irq(&ntp_lock);
664
665 if (txc->modes & ADJ_ADJTIME) {
666 long save_adjust = time_adjust;
667
668 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
669 /* adjtime() is independent from ntp_adjtime() */
670 time_adjust = txc->offset;
671 ntp_update_frequency();
672 }
673 txc->offset = save_adjust;
674 } else {
675
676 /* If there are input parameters, then process them: */
677 if (txc->modes)
678 process_adjtimex_modes(txc, &ts);
679
680 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
681 NTP_SCALE_SHIFT);
682 if (!(time_status & STA_NANO))
683 txc->offset /= NSEC_PER_USEC;
684 }
685
686 result = time_state; /* mostly `TIME_OK' */
687 /* check for errors */
688 if (is_error_status(time_status))
689 result = TIME_ERROR;
690
691 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
692 PPM_SCALE_INV, NTP_SCALE_SHIFT);
693 txc->maxerror = time_maxerror;
694 txc->esterror = time_esterror;
695 txc->status = time_status;
696 txc->constant = time_constant;
697 txc->precision = 1;
698 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE;
699 txc->tick = tick_usec;
700 txc->tai = time_tai;
701
702 /* fill PPS status fields */
703 pps_fill_timex(txc);
704
705 spin_unlock_irq(&ntp_lock);
706
707 txc->time.tv_sec = ts.tv_sec;
708 txc->time.tv_usec = ts.tv_nsec;
709 if (!(time_status & STA_NANO))
710 txc->time.tv_usec /= NSEC_PER_USEC;
711
712 notify_cmos_timer();
713
714 return result;
715}
716
717#ifdef CONFIG_NTP_PPS
718
719/* actually struct pps_normtime is good old struct timespec, but it is
720 * semantically different (and it is the reason why it was invented):
721 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
722 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
723struct pps_normtime {
724 __kernel_time_t sec; /* seconds */
725 long nsec; /* nanoseconds */
726};
727
728/* normalize the timestamp so that nsec is in the
729 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
730static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
731{
732 struct pps_normtime norm = {
733 .sec = ts.tv_sec,
734 .nsec = ts.tv_nsec
735 };
736
737 if (norm.nsec > (NSEC_PER_SEC >> 1)) {
738 norm.nsec -= NSEC_PER_SEC;
739 norm.sec++;
740 }
741
742 return norm;
743}
744
745/* get current phase correction and jitter */
746static inline long pps_phase_filter_get(long *jitter)
747{
748 *jitter = pps_tf[0] - pps_tf[1];
749 if (*jitter < 0)
750 *jitter = -*jitter;
751
752 /* TODO: test various filters */
753 return pps_tf[0];
754}
755
756/* add the sample to the phase filter */
757static inline void pps_phase_filter_add(long err)
758{
759 pps_tf[2] = pps_tf[1];
760 pps_tf[1] = pps_tf[0];
761 pps_tf[0] = err;
762}
763
764/* decrease frequency calibration interval length.
765 * It is halved after four consecutive unstable intervals.
766 */
767static inline void pps_dec_freq_interval(void)
768{
769 if (--pps_intcnt <= -PPS_INTCOUNT) {
770 pps_intcnt = -PPS_INTCOUNT;
771 if (pps_shift > PPS_INTMIN) {
772 pps_shift--;
773 pps_intcnt = 0;
774 }
775 }
776}
777
778/* increase frequency calibration interval length.
779 * It is doubled after four consecutive stable intervals.
780 */
781static inline void pps_inc_freq_interval(void)
782{
783 if (++pps_intcnt >= PPS_INTCOUNT) {
784 pps_intcnt = PPS_INTCOUNT;
785 if (pps_shift < PPS_INTMAX) {
786 pps_shift++;
787 pps_intcnt = 0;
788 }
789 }
790}
791
792/* update clock frequency based on MONOTONIC_RAW clock PPS signal
793 * timestamps
794 *
795 * At the end of the calibration interval the difference between the
796 * first and last MONOTONIC_RAW clock timestamps divided by the length
797 * of the interval becomes the frequency update. If the interval was
798 * too long, the data are discarded.
799 * Returns the difference between old and new frequency values.
800 */
801static long hardpps_update_freq(struct pps_normtime freq_norm)
802{
803 long delta, delta_mod;
804 s64 ftemp;
805
806 /* check if the frequency interval was too long */
807 if (freq_norm.sec > (2 << pps_shift)) {
808 time_status |= STA_PPSERROR;
809 pps_errcnt++;
810 pps_dec_freq_interval();
811 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
812 freq_norm.sec);
813 return 0;
814 }
815
816 /* here the raw frequency offset and wander (stability) is
817 * calculated. If the wander is less than the wander threshold
818 * the interval is increased; otherwise it is decreased.
819 */
820 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
821 freq_norm.sec);
822 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
823 pps_freq = ftemp;
824 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
825 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
826 time_status |= STA_PPSWANDER;
827 pps_stbcnt++;
828 pps_dec_freq_interval();
829 } else { /* good sample */
830 pps_inc_freq_interval();
831 }
832
833 /* the stability metric is calculated as the average of recent
834 * frequency changes, but is used only for performance
835 * monitoring
836 */
837 delta_mod = delta;
838 if (delta_mod < 0)
839 delta_mod = -delta_mod;
840 pps_stabil += (div_s64(((s64)delta_mod) <<
841 (NTP_SCALE_SHIFT - SHIFT_USEC),
842 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
843
844 /* if enabled, the system clock frequency is updated */
845 if ((time_status & STA_PPSFREQ) != 0 &&
846 (time_status & STA_FREQHOLD) == 0) {
847 time_freq = pps_freq;
848 ntp_update_frequency();
849 }
850
851 return delta;
852}
853
854/* correct REALTIME clock phase error against PPS signal */
855static void hardpps_update_phase(long error)
856{
857 long correction = -error;
858 long jitter;
859
860 /* add the sample to the median filter */
861 pps_phase_filter_add(correction);
862 correction = pps_phase_filter_get(&jitter);
863
864 /* Nominal jitter is due to PPS signal noise. If it exceeds the
865 * threshold, the sample is discarded; otherwise, if so enabled,
866 * the time offset is updated.
867 */
868 if (jitter > (pps_jitter << PPS_POPCORN)) {
869 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
870 jitter, (pps_jitter << PPS_POPCORN));
871 time_status |= STA_PPSJITTER;
872 pps_jitcnt++;
873 } else if (time_status & STA_PPSTIME) {
874 /* correct the time using the phase offset */
875 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
876 NTP_INTERVAL_FREQ);
877 /* cancel running adjtime() */
878 time_adjust = 0;
879 }
880 /* update jitter */
881 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
882}
883
884/*
885 * hardpps() - discipline CPU clock oscillator to external PPS signal
886 *
887 * This routine is called at each PPS signal arrival in order to
888 * discipline the CPU clock oscillator to the PPS signal. It takes two
889 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
890 * is used to correct clock phase error and the latter is used to
891 * correct the frequency.
892 *
893 * This code is based on David Mills's reference nanokernel
894 * implementation. It was mostly rewritten but keeps the same idea.
895 */
896void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
897{
898 struct pps_normtime pts_norm, freq_norm;
899 unsigned long flags;
900
901 pts_norm = pps_normalize_ts(*phase_ts);
902
903 spin_lock_irqsave(&ntp_lock, flags);
904
905 /* clear the error bits, they will be set again if needed */
906 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
907
908 /* indicate signal presence */
909 time_status |= STA_PPSSIGNAL;
910 pps_valid = PPS_VALID;
911
912 /* when called for the first time,
913 * just start the frequency interval */
914 if (unlikely(pps_fbase.tv_sec == 0)) {
915 pps_fbase = *raw_ts;
916 spin_unlock_irqrestore(&ntp_lock, flags);
917 return;
918 }
919
920 /* ok, now we have a base for frequency calculation */
921 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
922
923 /* check that the signal is in the range
924 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
925 if ((freq_norm.sec == 0) ||
926 (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
927 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
928 time_status |= STA_PPSJITTER;
929 /* restart the frequency calibration interval */
930 pps_fbase = *raw_ts;
931 spin_unlock_irqrestore(&ntp_lock, flags);
932 pr_err("hardpps: PPSJITTER: bad pulse\n");
933 return;
934 }
935
936 /* signal is ok */
937
938 /* check if the current frequency interval is finished */
939 if (freq_norm.sec >= (1 << pps_shift)) {
940 pps_calcnt++;
941 /* restart the frequency calibration interval */
942 pps_fbase = *raw_ts;
943 hardpps_update_freq(freq_norm);
944 }
945
946 hardpps_update_phase(pts_norm.nsec);
947
948 spin_unlock_irqrestore(&ntp_lock, flags);
949}
950EXPORT_SYMBOL(hardpps);
951
952#endif /* CONFIG_NTP_PPS */
953
954static int __init ntp_tick_adj_setup(char *str)
955{
956 ntp_tick_adj = simple_strtol(str, NULL, 0);
957 ntp_tick_adj <<= NTP_SCALE_SHIFT;
958
959 return 1;
960}
961
962__setup("ntp_tick_adj=", ntp_tick_adj_setup);
963
964void __init ntp_init(void)
965{
966 ntp_clear();
967}