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Linux/kernel/time/ntp.c

  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 #include <linux/rtc.h>
 19 
 20 #include "ntp_internal.h"
 21 
 22 /*
 23  * NTP timekeeping variables:
 24  *
 25  * Note: All of the NTP state is protected by the timekeeping locks.
 26  */
 27 
 28 
 29 /* USER_HZ period (usecs): */
 30 unsigned long                   tick_usec = TICK_USEC;
 31 
 32 /* SHIFTED_HZ period (nsecs): */
 33 unsigned long                   tick_nsec;
 34 
 35 static u64                      tick_length;
 36 static u64                      tick_length_base;
 37 
 38 #define SECS_PER_DAY            86400
 39 #define MAX_TICKADJ             500LL           /* usecs */
 40 #define MAX_TICKADJ_SCALED \
 41         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
 42 
 43 /*
 44  * phase-lock loop variables
 45  */
 46 
 47 /*
 48  * clock synchronization status
 49  *
 50  * (TIME_ERROR prevents overwriting the CMOS clock)
 51  */
 52 static int                      time_state = TIME_OK;
 53 
 54 /* clock status bits:                                                   */
 55 static int                      time_status = STA_UNSYNC;
 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 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */
 81 static time64_t                 ntp_next_leap_sec = TIME64_MAX;
 82 
 83 #ifdef CONFIG_NTP_PPS
 84 
 85 /*
 86  * The following variables are used when a pulse-per-second (PPS) signal
 87  * is available. They establish the engineering parameters of the clock
 88  * discipline loop when controlled by the PPS signal.
 89  */
 90 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
 91 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
 92 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
 93 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
 94 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
 95                                    increase pps_shift or consecutive bad
 96                                    intervals to decrease it */
 97 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
 98 
 99 static int pps_valid;           /* signal watchdog counter */
100 static long pps_tf[3];          /* phase median filter */
101 static long pps_jitter;         /* current jitter (ns) */
102 static struct timespec64 pps_fbase; /* beginning of the last freq interval */
103 static int pps_shift;           /* current interval duration (s) (shift) */
104 static int pps_intcnt;          /* interval counter */
105 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
106 static long pps_stabil;         /* current stability (scaled ns/s) */
107 
108 /*
109  * PPS signal quality monitors
110  */
111 static long pps_calcnt;         /* calibration intervals */
112 static long pps_jitcnt;         /* jitter limit exceeded */
113 static long pps_stbcnt;         /* stability limit exceeded */
114 static long pps_errcnt;         /* calibration errors */
115 
116 
117 /* PPS kernel consumer compensates the whole phase error immediately.
118  * Otherwise, reduce the offset by a fixed factor times the time constant.
119  */
120 static inline s64 ntp_offset_chunk(s64 offset)
121 {
122         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
123                 return offset;
124         else
125                 return shift_right(offset, SHIFT_PLL + time_constant);
126 }
127 
128 static inline void pps_reset_freq_interval(void)
129 {
130         /* the PPS calibration interval may end
131            surprisingly early */
132         pps_shift = PPS_INTMIN;
133         pps_intcnt = 0;
134 }
135 
136 /**
137  * pps_clear - Clears the PPS state variables
138  */
139 static 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 static inline void pps_dec_valid(void)
154 {
155         if (pps_valid > 0)
156                 pps_valid--;
157         else {
158                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
159                                  STA_PPSWANDER | STA_PPSERROR);
160                 pps_clear();
161         }
162 }
163 
164 static inline void pps_set_freq(s64 freq)
165 {
166         pps_freq = freq;
167 }
168 
169 static inline int is_error_status(int status)
170 {
171         return (status & (STA_UNSYNC|STA_CLOCKERR))
172                 /* PPS signal lost when either PPS time or
173                  * PPS frequency synchronization requested
174                  */
175                 || ((status & (STA_PPSFREQ|STA_PPSTIME))
176                         && !(status & STA_PPSSIGNAL))
177                 /* PPS jitter exceeded when
178                  * PPS time synchronization requested */
179                 || ((status & (STA_PPSTIME|STA_PPSJITTER))
180                         == (STA_PPSTIME|STA_PPSJITTER))
181                 /* PPS wander exceeded or calibration error when
182                  * PPS frequency synchronization requested
183                  */
184                 || ((status & STA_PPSFREQ)
185                         && (status & (STA_PPSWANDER|STA_PPSERROR)));
186 }
187 
188 static inline void pps_fill_timex(struct timex *txc)
189 {
190         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
191                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
192         txc->jitter        = pps_jitter;
193         if (!(time_status & STA_NANO))
194                 txc->jitter /= NSEC_PER_USEC;
195         txc->shift         = pps_shift;
196         txc->stabil        = pps_stabil;
197         txc->jitcnt        = pps_jitcnt;
198         txc->calcnt        = pps_calcnt;
199         txc->errcnt        = pps_errcnt;
200         txc->stbcnt        = pps_stbcnt;
201 }
202 
203 #else /* !CONFIG_NTP_PPS */
204 
205 static inline s64 ntp_offset_chunk(s64 offset)
206 {
207         return shift_right(offset, SHIFT_PLL + time_constant);
208 }
209 
210 static inline void pps_reset_freq_interval(void) {}
211 static inline void pps_clear(void) {}
212 static inline void pps_dec_valid(void) {}
213 static inline void pps_set_freq(s64 freq) {}
214 
215 static inline int is_error_status(int status)
216 {
217         return status & (STA_UNSYNC|STA_CLOCKERR);
218 }
219 
220 static inline void pps_fill_timex(struct timex *txc)
221 {
222         /* PPS is not implemented, so these are zero */
223         txc->ppsfreq       = 0;
224         txc->jitter        = 0;
225         txc->shift         = 0;
226         txc->stabil        = 0;
227         txc->jitcnt        = 0;
228         txc->calcnt        = 0;
229         txc->errcnt        = 0;
230         txc->stbcnt        = 0;
231 }
232 
233 #endif /* CONFIG_NTP_PPS */
234 
235 
236 /**
237  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
238  *
239  */
240 static inline int ntp_synced(void)
241 {
242         return !(time_status & STA_UNSYNC);
243 }
244 
245 
246 /*
247  * NTP methods:
248  */
249 
250 /*
251  * Update (tick_length, tick_length_base, tick_nsec), based
252  * on (tick_usec, ntp_tick_adj, time_freq):
253  */
254 static void ntp_update_frequency(void)
255 {
256         u64 second_length;
257         u64 new_base;
258 
259         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
260                                                 << NTP_SCALE_SHIFT;
261 
262         second_length           += ntp_tick_adj;
263         second_length           += time_freq;
264 
265         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
266         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
267 
268         /*
269          * Don't wait for the next second_overflow, apply
270          * the change to the tick length immediately:
271          */
272         tick_length             += new_base - tick_length_base;
273         tick_length_base         = new_base;
274 }
275 
276 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
277 {
278         time_status &= ~STA_MODE;
279 
280         if (secs < MINSEC)
281                 return 0;
282 
283         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
284                 return 0;
285 
286         time_status |= STA_MODE;
287 
288         return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
289 }
290 
291 static void ntp_update_offset(long offset)
292 {
293         s64 freq_adj;
294         s64 offset64;
295         long secs;
296 
297         if (!(time_status & STA_PLL))
298                 return;
299 
300         if (!(time_status & STA_NANO))
301                 offset *= NSEC_PER_USEC;
302 
303         /*
304          * Scale the phase adjustment and
305          * clamp to the operating range.
306          */
307         offset = min(offset, MAXPHASE);
308         offset = max(offset, -MAXPHASE);
309 
310         /*
311          * Select how the frequency is to be controlled
312          * and in which mode (PLL or FLL).
313          */
314         secs = get_seconds() - time_reftime;
315         if (unlikely(time_status & STA_FREQHOLD))
316                 secs = 0;
317 
318         time_reftime = get_seconds();
319 
320         offset64    = offset;
321         freq_adj    = ntp_update_offset_fll(offset64, secs);
322 
323         /*
324          * Clamp update interval to reduce PLL gain with low
325          * sampling rate (e.g. intermittent network connection)
326          * to avoid instability.
327          */
328         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
329                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
330 
331         freq_adj    += (offset64 * secs) <<
332                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
333 
334         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
335 
336         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
337 
338         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
339 }
340 
341 /**
342  * ntp_clear - Clears the NTP state variables
343  */
344 void ntp_clear(void)
345 {
346         time_adjust     = 0;            /* stop active adjtime() */
347         time_status     |= STA_UNSYNC;
348         time_maxerror   = NTP_PHASE_LIMIT;
349         time_esterror   = NTP_PHASE_LIMIT;
350 
351         ntp_update_frequency();
352 
353         tick_length     = tick_length_base;
354         time_offset     = 0;
355 
356         ntp_next_leap_sec = TIME64_MAX;
357         /* Clear PPS state variables */
358         pps_clear();
359 }
360 
361 
362 u64 ntp_tick_length(void)
363 {
364         return tick_length;
365 }
366 
367 /**
368  * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
369  *
370  * Provides the time of the next leapsecond against CLOCK_REALTIME in
371  * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
372  */
373 ktime_t ntp_get_next_leap(void)
374 {
375         ktime_t ret;
376 
377         if ((time_state == TIME_INS) && (time_status & STA_INS))
378                 return ktime_set(ntp_next_leap_sec, 0);
379         ret.tv64 = KTIME_MAX;
380         return ret;
381 }
382 
383 /*
384  * this routine handles the overflow of the microsecond field
385  *
386  * The tricky bits of code to handle the accurate clock support
387  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
388  * They were originally developed for SUN and DEC kernels.
389  * All the kudos should go to Dave for this stuff.
390  *
391  * Also handles leap second processing, and returns leap offset
392  */
393 int second_overflow(unsigned long secs)
394 {
395         s64 delta;
396         int leap = 0;
397 
398         /*
399          * Leap second processing. If in leap-insert state at the end of the
400          * day, the system clock is set back one second; if in leap-delete
401          * state, the system clock is set ahead one second.
402          */
403         switch (time_state) {
404         case TIME_OK:
405                 if (time_status & STA_INS) {
406                         time_state = TIME_INS;
407                         ntp_next_leap_sec = secs + SECS_PER_DAY -
408                                                 (secs % SECS_PER_DAY);
409                 } else if (time_status & STA_DEL) {
410                         time_state = TIME_DEL;
411                         ntp_next_leap_sec = secs + SECS_PER_DAY -
412                                                  ((secs+1) % SECS_PER_DAY);
413                 }
414                 break;
415         case TIME_INS:
416                 if (!(time_status & STA_INS)) {
417                         ntp_next_leap_sec = TIME64_MAX;
418                         time_state = TIME_OK;
419                 } else if (secs % SECS_PER_DAY == 0) {
420                         leap = -1;
421                         time_state = TIME_OOP;
422                         printk(KERN_NOTICE
423                                 "Clock: inserting leap second 23:59:60 UTC\n");
424                 }
425                 break;
426         case TIME_DEL:
427                 if (!(time_status & STA_DEL)) {
428                         ntp_next_leap_sec = TIME64_MAX;
429                         time_state = TIME_OK;
430                 } else if ((secs + 1) % SECS_PER_DAY == 0) {
431                         leap = 1;
432                         ntp_next_leap_sec = TIME64_MAX;
433                         time_state = TIME_WAIT;
434                         printk(KERN_NOTICE
435                                 "Clock: deleting leap second 23:59:59 UTC\n");
436                 }
437                 break;
438         case TIME_OOP:
439                 ntp_next_leap_sec = TIME64_MAX;
440                 time_state = TIME_WAIT;
441                 break;
442         case TIME_WAIT:
443                 if (!(time_status & (STA_INS | STA_DEL)))
444                         time_state = TIME_OK;
445                 break;
446         }
447 
448 
449         /* Bump the maxerror field */
450         time_maxerror += MAXFREQ / NSEC_PER_USEC;
451         if (time_maxerror > NTP_PHASE_LIMIT) {
452                 time_maxerror = NTP_PHASE_LIMIT;
453                 time_status |= STA_UNSYNC;
454         }
455 
456         /* Compute the phase adjustment for the next second */
457         tick_length      = tick_length_base;
458 
459         delta            = ntp_offset_chunk(time_offset);
460         time_offset     -= delta;
461         tick_length     += delta;
462 
463         /* Check PPS signal */
464         pps_dec_valid();
465 
466         if (!time_adjust)
467                 goto out;
468 
469         if (time_adjust > MAX_TICKADJ) {
470                 time_adjust -= MAX_TICKADJ;
471                 tick_length += MAX_TICKADJ_SCALED;
472                 goto out;
473         }
474 
475         if (time_adjust < -MAX_TICKADJ) {
476                 time_adjust += MAX_TICKADJ;
477                 tick_length -= MAX_TICKADJ_SCALED;
478                 goto out;
479         }
480 
481         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
482                                                          << NTP_SCALE_SHIFT;
483         time_adjust = 0;
484 
485 out:
486         return leap;
487 }
488 
489 #ifdef CONFIG_GENERIC_CMOS_UPDATE
490 int __weak update_persistent_clock(struct timespec now)
491 {
492         return -ENODEV;
493 }
494 
495 int __weak update_persistent_clock64(struct timespec64 now64)
496 {
497         struct timespec now;
498 
499         now = timespec64_to_timespec(now64);
500         return update_persistent_clock(now);
501 }
502 #endif
503 
504 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
505 static void sync_cmos_clock(struct work_struct *work);
506 
507 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
508 
509 static void sync_cmos_clock(struct work_struct *work)
510 {
511         struct timespec64 now;
512         struct timespec64 next;
513         int fail = 1;
514 
515         /*
516          * If we have an externally synchronized Linux clock, then update
517          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
518          * called as close as possible to 500 ms before the new second starts.
519          * This code is run on a timer.  If the clock is set, that timer
520          * may not expire at the correct time.  Thus, we adjust...
521          * We want the clock to be within a couple of ticks from the target.
522          */
523         if (!ntp_synced()) {
524                 /*
525                  * Not synced, exit, do not restart a timer (if one is
526                  * running, let it run out).
527                  */
528                 return;
529         }
530 
531         getnstimeofday64(&now);
532         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) {
533                 struct timespec64 adjust = now;
534 
535                 fail = -ENODEV;
536                 if (persistent_clock_is_local)
537                         adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
538 #ifdef CONFIG_GENERIC_CMOS_UPDATE
539                 fail = update_persistent_clock64(adjust);
540 #endif
541 
542 #ifdef CONFIG_RTC_SYSTOHC
543                 if (fail == -ENODEV)
544                         fail = rtc_set_ntp_time(adjust);
545 #endif
546         }
547 
548         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
549         if (next.tv_nsec <= 0)
550                 next.tv_nsec += NSEC_PER_SEC;
551 
552         if (!fail || fail == -ENODEV)
553                 next.tv_sec = 659;
554         else
555                 next.tv_sec = 0;
556 
557         if (next.tv_nsec >= NSEC_PER_SEC) {
558                 next.tv_sec++;
559                 next.tv_nsec -= NSEC_PER_SEC;
560         }
561         queue_delayed_work(system_power_efficient_wq,
562                            &sync_cmos_work, timespec64_to_jiffies(&next));
563 }
564 
565 void ntp_notify_cmos_timer(void)
566 {
567         queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0);
568 }
569 
570 #else
571 void ntp_notify_cmos_timer(void) { }
572 #endif
573 
574 
575 /*
576  * Propagate a new txc->status value into the NTP state:
577  */
578 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts)
579 {
580         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
581                 time_state = TIME_OK;
582                 time_status = STA_UNSYNC;
583                 ntp_next_leap_sec = TIME64_MAX;
584                 /* restart PPS frequency calibration */
585                 pps_reset_freq_interval();
586         }
587 
588         /*
589          * If we turn on PLL adjustments then reset the
590          * reference time to current time.
591          */
592         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
593                 time_reftime = get_seconds();
594 
595         /* only set allowed bits */
596         time_status &= STA_RONLY;
597         time_status |= txc->status & ~STA_RONLY;
598 }
599 
600 
601 static inline void process_adjtimex_modes(struct timex *txc,
602                                                 struct timespec64 *ts,
603                                                 s32 *time_tai)
604 {
605         if (txc->modes & ADJ_STATUS)
606                 process_adj_status(txc, ts);
607 
608         if (txc->modes & ADJ_NANO)
609                 time_status |= STA_NANO;
610 
611         if (txc->modes & ADJ_MICRO)
612                 time_status &= ~STA_NANO;
613 
614         if (txc->modes & ADJ_FREQUENCY) {
615                 time_freq = txc->freq * PPM_SCALE;
616                 time_freq = min(time_freq, MAXFREQ_SCALED);
617                 time_freq = max(time_freq, -MAXFREQ_SCALED);
618                 /* update pps_freq */
619                 pps_set_freq(time_freq);
620         }
621 
622         if (txc->modes & ADJ_MAXERROR)
623                 time_maxerror = txc->maxerror;
624 
625         if (txc->modes & ADJ_ESTERROR)
626                 time_esterror = txc->esterror;
627 
628         if (txc->modes & ADJ_TIMECONST) {
629                 time_constant = txc->constant;
630                 if (!(time_status & STA_NANO))
631                         time_constant += 4;
632                 time_constant = min(time_constant, (long)MAXTC);
633                 time_constant = max(time_constant, 0l);
634         }
635 
636         if (txc->modes & ADJ_TAI && txc->constant > 0)
637                 *time_tai = txc->constant;
638 
639         if (txc->modes & ADJ_OFFSET)
640                 ntp_update_offset(txc->offset);
641 
642         if (txc->modes & ADJ_TICK)
643                 tick_usec = txc->tick;
644 
645         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
646                 ntp_update_frequency();
647 }
648 
649 
650 
651 /**
652  * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
653  */
654 int ntp_validate_timex(struct timex *txc)
655 {
656         if (txc->modes & ADJ_ADJTIME) {
657                 /* singleshot must not be used with any other mode bits */
658                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
659                         return -EINVAL;
660                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
661                     !capable(CAP_SYS_TIME))
662                         return -EPERM;
663         } else {
664                 /* In order to modify anything, you gotta be super-user! */
665                  if (txc->modes && !capable(CAP_SYS_TIME))
666                         return -EPERM;
667                 /*
668                  * if the quartz is off by more than 10% then
669                  * something is VERY wrong!
670                  */
671                 if (txc->modes & ADJ_TICK &&
672                     (txc->tick <  900000/USER_HZ ||
673                      txc->tick > 1100000/USER_HZ))
674                         return -EINVAL;
675         }
676 
677         if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
678                 return -EPERM;
679 
680         /*
681          * Check for potential multiplication overflows that can
682          * only happen on 64-bit systems:
683          */
684         if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) {
685                 if (LLONG_MIN / PPM_SCALE > txc->freq)
686                         return -EINVAL;
687                 if (LLONG_MAX / PPM_SCALE < txc->freq)
688                         return -EINVAL;
689         }
690 
691         return 0;
692 }
693 
694 
695 /*
696  * adjtimex mainly allows reading (and writing, if superuser) of
697  * kernel time-keeping variables. used by xntpd.
698  */
699 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai)
700 {
701         int result;
702 
703         if (txc->modes & ADJ_ADJTIME) {
704                 long save_adjust = time_adjust;
705 
706                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
707                         /* adjtime() is independent from ntp_adjtime() */
708                         time_adjust = txc->offset;
709                         ntp_update_frequency();
710                 }
711                 txc->offset = save_adjust;
712         } else {
713 
714                 /* If there are input parameters, then process them: */
715                 if (txc->modes)
716                         process_adjtimex_modes(txc, ts, time_tai);
717 
718                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
719                                   NTP_SCALE_SHIFT);
720                 if (!(time_status & STA_NANO))
721                         txc->offset /= NSEC_PER_USEC;
722         }
723 
724         result = time_state;    /* mostly `TIME_OK' */
725         /* check for errors */
726         if (is_error_status(time_status))
727                 result = TIME_ERROR;
728 
729         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
730                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
731         txc->maxerror      = time_maxerror;
732         txc->esterror      = time_esterror;
733         txc->status        = time_status;
734         txc->constant      = time_constant;
735         txc->precision     = 1;
736         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
737         txc->tick          = tick_usec;
738         txc->tai           = *time_tai;
739 
740         /* fill PPS status fields */
741         pps_fill_timex(txc);
742 
743         txc->time.tv_sec = (time_t)ts->tv_sec;
744         txc->time.tv_usec = ts->tv_nsec;
745         if (!(time_status & STA_NANO))
746                 txc->time.tv_usec /= NSEC_PER_USEC;
747 
748         /* Handle leapsec adjustments */
749         if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
750                 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
751                         result = TIME_OOP;
752                         txc->tai++;
753                         txc->time.tv_sec--;
754                 }
755                 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
756                         result = TIME_WAIT;
757                         txc->tai--;
758                         txc->time.tv_sec++;
759                 }
760                 if ((time_state == TIME_OOP) &&
761                                         (ts->tv_sec == ntp_next_leap_sec)) {
762                         result = TIME_WAIT;
763                 }
764         }
765 
766         return result;
767 }
768 
769 #ifdef  CONFIG_NTP_PPS
770 
771 /* actually struct pps_normtime is good old struct timespec, but it is
772  * semantically different (and it is the reason why it was invented):
773  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
774  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
775 struct pps_normtime {
776         s64             sec;    /* seconds */
777         long            nsec;   /* nanoseconds */
778 };
779 
780 /* normalize the timestamp so that nsec is in the
781    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
782 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
783 {
784         struct pps_normtime norm = {
785                 .sec = ts.tv_sec,
786                 .nsec = ts.tv_nsec
787         };
788 
789         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
790                 norm.nsec -= NSEC_PER_SEC;
791                 norm.sec++;
792         }
793 
794         return norm;
795 }
796 
797 /* get current phase correction and jitter */
798 static inline long pps_phase_filter_get(long *jitter)
799 {
800         *jitter = pps_tf[0] - pps_tf[1];
801         if (*jitter < 0)
802                 *jitter = -*jitter;
803 
804         /* TODO: test various filters */
805         return pps_tf[0];
806 }
807 
808 /* add the sample to the phase filter */
809 static inline void pps_phase_filter_add(long err)
810 {
811         pps_tf[2] = pps_tf[1];
812         pps_tf[1] = pps_tf[0];
813         pps_tf[0] = err;
814 }
815 
816 /* decrease frequency calibration interval length.
817  * It is halved after four consecutive unstable intervals.
818  */
819 static inline void pps_dec_freq_interval(void)
820 {
821         if (--pps_intcnt <= -PPS_INTCOUNT) {
822                 pps_intcnt = -PPS_INTCOUNT;
823                 if (pps_shift > PPS_INTMIN) {
824                         pps_shift--;
825                         pps_intcnt = 0;
826                 }
827         }
828 }
829 
830 /* increase frequency calibration interval length.
831  * It is doubled after four consecutive stable intervals.
832  */
833 static inline void pps_inc_freq_interval(void)
834 {
835         if (++pps_intcnt >= PPS_INTCOUNT) {
836                 pps_intcnt = PPS_INTCOUNT;
837                 if (pps_shift < PPS_INTMAX) {
838                         pps_shift++;
839                         pps_intcnt = 0;
840                 }
841         }
842 }
843 
844 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
845  * timestamps
846  *
847  * At the end of the calibration interval the difference between the
848  * first and last MONOTONIC_RAW clock timestamps divided by the length
849  * of the interval becomes the frequency update. If the interval was
850  * too long, the data are discarded.
851  * Returns the difference between old and new frequency values.
852  */
853 static long hardpps_update_freq(struct pps_normtime freq_norm)
854 {
855         long delta, delta_mod;
856         s64 ftemp;
857 
858         /* check if the frequency interval was too long */
859         if (freq_norm.sec > (2 << pps_shift)) {
860                 time_status |= STA_PPSERROR;
861                 pps_errcnt++;
862                 pps_dec_freq_interval();
863                 printk_deferred(KERN_ERR
864                         "hardpps: PPSERROR: interval too long - %lld s\n",
865                         freq_norm.sec);
866                 return 0;
867         }
868 
869         /* here the raw frequency offset and wander (stability) is
870          * calculated. If the wander is less than the wander threshold
871          * the interval is increased; otherwise it is decreased.
872          */
873         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
874                         freq_norm.sec);
875         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
876         pps_freq = ftemp;
877         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
878                 printk_deferred(KERN_WARNING
879                                 "hardpps: PPSWANDER: change=%ld\n", delta);
880                 time_status |= STA_PPSWANDER;
881                 pps_stbcnt++;
882                 pps_dec_freq_interval();
883         } else {        /* good sample */
884                 pps_inc_freq_interval();
885         }
886 
887         /* the stability metric is calculated as the average of recent
888          * frequency changes, but is used only for performance
889          * monitoring
890          */
891         delta_mod = delta;
892         if (delta_mod < 0)
893                 delta_mod = -delta_mod;
894         pps_stabil += (div_s64(((s64)delta_mod) <<
895                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
896                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
897 
898         /* if enabled, the system clock frequency is updated */
899         if ((time_status & STA_PPSFREQ) != 0 &&
900             (time_status & STA_FREQHOLD) == 0) {
901                 time_freq = pps_freq;
902                 ntp_update_frequency();
903         }
904 
905         return delta;
906 }
907 
908 /* correct REALTIME clock phase error against PPS signal */
909 static void hardpps_update_phase(long error)
910 {
911         long correction = -error;
912         long jitter;
913 
914         /* add the sample to the median filter */
915         pps_phase_filter_add(correction);
916         correction = pps_phase_filter_get(&jitter);
917 
918         /* Nominal jitter is due to PPS signal noise. If it exceeds the
919          * threshold, the sample is discarded; otherwise, if so enabled,
920          * the time offset is updated.
921          */
922         if (jitter > (pps_jitter << PPS_POPCORN)) {
923                 printk_deferred(KERN_WARNING
924                                 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
925                                 jitter, (pps_jitter << PPS_POPCORN));
926                 time_status |= STA_PPSJITTER;
927                 pps_jitcnt++;
928         } else if (time_status & STA_PPSTIME) {
929                 /* correct the time using the phase offset */
930                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
931                                 NTP_INTERVAL_FREQ);
932                 /* cancel running adjtime() */
933                 time_adjust = 0;
934         }
935         /* update jitter */
936         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
937 }
938 
939 /*
940  * __hardpps() - discipline CPU clock oscillator to external PPS signal
941  *
942  * This routine is called at each PPS signal arrival in order to
943  * discipline the CPU clock oscillator to the PPS signal. It takes two
944  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
945  * is used to correct clock phase error and the latter is used to
946  * correct the frequency.
947  *
948  * This code is based on David Mills's reference nanokernel
949  * implementation. It was mostly rewritten but keeps the same idea.
950  */
951 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
952 {
953         struct pps_normtime pts_norm, freq_norm;
954 
955         pts_norm = pps_normalize_ts(*phase_ts);
956 
957         /* clear the error bits, they will be set again if needed */
958         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
959 
960         /* indicate signal presence */
961         time_status |= STA_PPSSIGNAL;
962         pps_valid = PPS_VALID;
963 
964         /* when called for the first time,
965          * just start the frequency interval */
966         if (unlikely(pps_fbase.tv_sec == 0)) {
967                 pps_fbase = *raw_ts;
968                 return;
969         }
970 
971         /* ok, now we have a base for frequency calculation */
972         freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
973 
974         /* check that the signal is in the range
975          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
976         if ((freq_norm.sec == 0) ||
977                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
978                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
979                 time_status |= STA_PPSJITTER;
980                 /* restart the frequency calibration interval */
981                 pps_fbase = *raw_ts;
982                 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
983                 return;
984         }
985 
986         /* signal is ok */
987 
988         /* check if the current frequency interval is finished */
989         if (freq_norm.sec >= (1 << pps_shift)) {
990                 pps_calcnt++;
991                 /* restart the frequency calibration interval */
992                 pps_fbase = *raw_ts;
993                 hardpps_update_freq(freq_norm);
994         }
995 
996         hardpps_update_phase(pts_norm.nsec);
997 
998 }
999 #endif  /* CONFIG_NTP_PPS */
1000 
1001 static int __init ntp_tick_adj_setup(char *str)
1002 {
1003         int rc = kstrtol(str, 0, (long *)&ntp_tick_adj);
1004 
1005         if (rc)
1006                 return rc;
1007         ntp_tick_adj <<= NTP_SCALE_SHIFT;
1008 
1009         return 1;
1010 }
1011 
1012 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1013 
1014 void __init ntp_init(void)
1015 {
1016         ntp_clear();
1017 }
1018 

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