root/kernel/time/ntp.c

DEFINITIONS

1. ntp_offset_chunk
2. pps_reset_freq_interval
3. pps_clear
4. pps_dec_valid
5. pps_set_freq
6. is_error_status
7. pps_fill_timex
8. ntp_offset_chunk
9. pps_reset_freq_interval
10. pps_clear
11. pps_dec_valid
12. pps_set_freq
13. is_error_status
14. pps_fill_timex
15. ntp_synced
16. ntp_update_frequency
17. ntp_update_offset_fll
18. ntp_update_offset
19. ntp_clear
20. ntp_tick_length
21. ntp_get_next_leap
22. second_overflow
23. sched_sync_hw_clock
24. sync_rtc_clock
25. update_persistent_clock64
26. sync_cmos_clock
27. sync_hw_clock
28. ntp_notify_cmos_timer
29. process_adj_status
30. process_adjtimex_modes
31. __do_adjtimex
32. pps_normalize_ts
33. pps_phase_filter_get
34. pps_phase_filter_add
35. pps_dec_freq_interval
36. pps_inc_freq_interval
37. hardpps_update_freq
38. hardpps_update_phase
39. __hardpps
40. ntp_tick_adj_setup
41. ntp_init

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * NTP state machine interfaces and logic.
   4  *
   5  * This code was mainly moved from kernel/timer.c and kernel/time.c
   6  * Please see those files for relevant copyright info and historical
   7  * changelogs.
   8  */
   9 #include <linux/capability.h>
  10 #include <linux/clocksource.h>
  11 #include <linux/workqueue.h>
  12 #include <linux/hrtimer.h>
  13 #include <linux/jiffies.h>
  14 #include <linux/math64.h>
  15 #include <linux/timex.h>
  16 #include <linux/time.h>
  17 #include <linux/mm.h>
  18 #include <linux/module.h>
  19 #include <linux/rtc.h>
  20 #include <linux/audit.h>
  21 
  22 #include "ntp_internal.h"
  23 #include "timekeeping_internal.h"
  24 
  25 
  26 /*
  27  * NTP timekeeping variables:
  28  *
  29  * Note: All of the NTP state is protected by the timekeeping locks.
  30  */
  31 
  32 
  33 /* USER_HZ period (usecs): */
  34 unsigned long                   tick_usec = USER_TICK_USEC;
  35 
  36 /* SHIFTED_HZ period (nsecs): */
  37 unsigned long                   tick_nsec;
  38 
  39 static u64                      tick_length;
  40 static u64                      tick_length_base;
  41 
  42 #define SECS_PER_DAY            86400
  43 #define MAX_TICKADJ             500LL           /* usecs */
  44 #define MAX_TICKADJ_SCALED \
  45         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  46 #define MAX_TAI_OFFSET          100000
  47 
  48 /*
  49  * phase-lock loop variables
  50  */
  51 
  52 /*
  53  * clock synchronization status
  54  *
  55  * (TIME_ERROR prevents overwriting the CMOS clock)
  56  */
  57 static int                      time_state = TIME_OK;
  58 
  59 /* clock status bits:                                                   */
  60 static int                      time_status = STA_UNSYNC;
  61 
  62 /* time adjustment (nsecs):                                             */
  63 static s64                      time_offset;
  64 
  65 /* pll time constant:                                                   */
  66 static long                     time_constant = 2;
  67 
  68 /* maximum error (usecs):                                               */
  69 static long                     time_maxerror = NTP_PHASE_LIMIT;
  70 
  71 /* estimated error (usecs):                                             */
  72 static long                     time_esterror = NTP_PHASE_LIMIT;
  73 
  74 /* frequency offset (scaled nsecs/secs):                                */
  75 static s64                      time_freq;
  76 
  77 /* time at last adjustment (secs):                                      */
  78 static time64_t         time_reftime;
  79 
  80 static long                     time_adjust;
  81 
  82 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
  83 static s64                      ntp_tick_adj;
  84 
  85 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */
  86 static time64_t                 ntp_next_leap_sec = TIME64_MAX;
  87 
  88 #ifdef CONFIG_NTP_PPS
  89 
  90 /*
  91  * The following variables are used when a pulse-per-second (PPS) signal
  92  * is available. They establish the engineering parameters of the clock
  93  * discipline loop when controlled by the PPS signal.
  94  */
  95 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
  96 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
  97 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
  98 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
  99 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
 100                                    increase pps_shift or consecutive bad
 101                                    intervals to decrease it */
 102 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
 103 
 104 static int pps_valid;           /* signal watchdog counter */
 105 static long pps_tf[3];          /* phase median filter */
 106 static long pps_jitter;         /* current jitter (ns) */
 107 static struct timespec64 pps_fbase; /* beginning of the last freq interval */
 108 static int pps_shift;           /* current interval duration (s) (shift) */
 109 static int pps_intcnt;          /* interval counter */
 110 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
 111 static long pps_stabil;         /* current stability (scaled ns/s) */
 112 
 113 /*
 114  * PPS signal quality monitors
 115  */
 116 static long pps_calcnt;         /* calibration intervals */
 117 static long pps_jitcnt;         /* jitter limit exceeded */
 118 static long pps_stbcnt;         /* stability limit exceeded */
 119 static long pps_errcnt;         /* calibration errors */
 120 
 121 
 122 /* PPS kernel consumer compensates the whole phase error immediately.
 123  * Otherwise, reduce the offset by a fixed factor times the time constant.
 124  */
 125 static inline s64 ntp_offset_chunk(s64 offset)
 126 {
 127         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
 128                 return offset;
 129         else
 130                 return shift_right(offset, SHIFT_PLL + time_constant);
 131 }
 132 
 133 static inline void pps_reset_freq_interval(void)
 134 {
 135         /* the PPS calibration interval may end
 136            surprisingly early */
 137         pps_shift = PPS_INTMIN;
 138         pps_intcnt = 0;
 139 }
 140 
 141 /**
 142  * pps_clear - Clears the PPS state variables
 143  */
 144 static inline void pps_clear(void)
 145 {
 146         pps_reset_freq_interval();
 147         pps_tf[0] = 0;
 148         pps_tf[1] = 0;
 149         pps_tf[2] = 0;
 150         pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
 151         pps_freq = 0;
 152 }
 153 
 154 /* Decrease pps_valid to indicate that another second has passed since
 155  * the last PPS signal. When it reaches 0, indicate that PPS signal is
 156  * missing.
 157  */
 158 static inline void pps_dec_valid(void)
 159 {
 160         if (pps_valid > 0)
 161                 pps_valid--;
 162         else {
 163                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 164                                  STA_PPSWANDER | STA_PPSERROR);
 165                 pps_clear();
 166         }
 167 }
 168 
 169 static inline void pps_set_freq(s64 freq)
 170 {
 171         pps_freq = freq;
 172 }
 173 
 174 static inline int is_error_status(int status)
 175 {
 176         return (status & (STA_UNSYNC|STA_CLOCKERR))
 177                 /* PPS signal lost when either PPS time or
 178                  * PPS frequency synchronization requested
 179                  */
 180                 || ((status & (STA_PPSFREQ|STA_PPSTIME))
 181                         && !(status & STA_PPSSIGNAL))
 182                 /* PPS jitter exceeded when
 183                  * PPS time synchronization requested */
 184                 || ((status & (STA_PPSTIME|STA_PPSJITTER))
 185                         == (STA_PPSTIME|STA_PPSJITTER))
 186                 /* PPS wander exceeded or calibration error when
 187                  * PPS frequency synchronization requested
 188                  */
 189                 || ((status & STA_PPSFREQ)
 190                         && (status & (STA_PPSWANDER|STA_PPSERROR)));
 191 }
 192 
 193 static inline void pps_fill_timex(struct __kernel_timex *txc)
 194 {
 195         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 196                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 197         txc->jitter        = pps_jitter;
 198         if (!(time_status & STA_NANO))
 199                 txc->jitter = pps_jitter / NSEC_PER_USEC;
 200         txc->shift         = pps_shift;
 201         txc->stabil        = pps_stabil;
 202         txc->jitcnt        = pps_jitcnt;
 203         txc->calcnt        = pps_calcnt;
 204         txc->errcnt        = pps_errcnt;
 205         txc->stbcnt        = pps_stbcnt;
 206 }
 207 
 208 #else /* !CONFIG_NTP_PPS */
 209 
 210 static inline s64 ntp_offset_chunk(s64 offset)
 211 {
 212         return shift_right(offset, SHIFT_PLL + time_constant);
 213 }
 214 
 215 static inline void pps_reset_freq_interval(void) {}
 216 static inline void pps_clear(void) {}
 217 static inline void pps_dec_valid(void) {}
 218 static inline void pps_set_freq(s64 freq) {}
 219 
 220 static inline int is_error_status(int status)
 221 {
 222         return status & (STA_UNSYNC|STA_CLOCKERR);
 223 }
 224 
 225 static inline void pps_fill_timex(struct __kernel_timex *txc)
 226 {
 227         /* PPS is not implemented, so these are zero */
 228         txc->ppsfreq       = 0;
 229         txc->jitter        = 0;
 230         txc->shift         = 0;
 231         txc->stabil        = 0;
 232         txc->jitcnt        = 0;
 233         txc->calcnt        = 0;
 234         txc->errcnt        = 0;
 235         txc->stbcnt        = 0;
 236 }
 237 
 238 #endif /* CONFIG_NTP_PPS */
 239 
 240 
 241 /**
 242  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 243  *
 244  */
 245 static inline int ntp_synced(void)
 246 {
 247         return !(time_status & STA_UNSYNC);
 248 }
 249 
 250 
 251 /*
 252  * NTP methods:
 253  */
 254 
 255 /*
 256  * Update (tick_length, tick_length_base, tick_nsec), based
 257  * on (tick_usec, ntp_tick_adj, time_freq):
 258  */
 259 static void ntp_update_frequency(void)
 260 {
 261         u64 second_length;
 262         u64 new_base;
 263 
 264         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 265                                                 << NTP_SCALE_SHIFT;
 266 
 267         second_length           += ntp_tick_adj;
 268         second_length           += time_freq;
 269 
 270         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 271         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 272 
 273         /*
 274          * Don't wait for the next second_overflow, apply
 275          * the change to the tick length immediately:
 276          */
 277         tick_length             += new_base - tick_length_base;
 278         tick_length_base         = new_base;
 279 }
 280 
 281 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 282 {
 283         time_status &= ~STA_MODE;
 284 
 285         if (secs < MINSEC)
 286                 return 0;
 287 
 288         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 289                 return 0;
 290 
 291         time_status |= STA_MODE;
 292 
 293         return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 294 }
 295 
 296 static void ntp_update_offset(long offset)
 297 {
 298         s64 freq_adj;
 299         s64 offset64;
 300         long secs;
 301 
 302         if (!(time_status & STA_PLL))
 303                 return;
 304 
 305         if (!(time_status & STA_NANO)) {
 306                 /* Make sure the multiplication below won't overflow */
 307                 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC);
 308                 offset *= NSEC_PER_USEC;
 309         }
 310 
 311         /*
 312          * Scale the phase adjustment and
 313          * clamp to the operating range.
 314          */
 315         offset = clamp(offset, -MAXPHASE, MAXPHASE);
 316 
 317         /*
 318          * Select how the frequency is to be controlled
 319          * and in which mode (PLL or FLL).
 320          */
 321         secs = (long)(__ktime_get_real_seconds() - time_reftime);
 322         if (unlikely(time_status & STA_FREQHOLD))
 323                 secs = 0;
 324 
 325         time_reftime = __ktime_get_real_seconds();
 326 
 327         offset64    = offset;
 328         freq_adj    = ntp_update_offset_fll(offset64, secs);
 329 
 330         /*
 331          * Clamp update interval to reduce PLL gain with low
 332          * sampling rate (e.g. intermittent network connection)
 333          * to avoid instability.
 334          */
 335         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 336                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
 337 
 338         freq_adj    += (offset64 * secs) <<
 339                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 340 
 341         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 342 
 343         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 344 
 345         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 346 }
 347 
 348 /**
 349  * ntp_clear - Clears the NTP state variables
 350  */
 351 void ntp_clear(void)
 352 {
 353         time_adjust     = 0;            /* stop active adjtime() */
 354         time_status     |= STA_UNSYNC;
 355         time_maxerror   = NTP_PHASE_LIMIT;
 356         time_esterror   = NTP_PHASE_LIMIT;
 357 
 358         ntp_update_frequency();
 359 
 360         tick_length     = tick_length_base;
 361         time_offset     = 0;
 362 
 363         ntp_next_leap_sec = TIME64_MAX;
 364         /* Clear PPS state variables */
 365         pps_clear();
 366 }
 367 
 368 
 369 u64 ntp_tick_length(void)
 370 {
 371         return tick_length;
 372 }
 373 
 374 /**
 375  * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t
 376  *
 377  * Provides the time of the next leapsecond against CLOCK_REALTIME in
 378  * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending.
 379  */
 380 ktime_t ntp_get_next_leap(void)
 381 {
 382         ktime_t ret;
 383 
 384         if ((time_state == TIME_INS) && (time_status & STA_INS))
 385                 return ktime_set(ntp_next_leap_sec, 0);
 386         ret = KTIME_MAX;
 387         return ret;
 388 }
 389 
 390 /*
 391  * this routine handles the overflow of the microsecond field
 392  *
 393  * The tricky bits of code to handle the accurate clock support
 394  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 395  * They were originally developed for SUN and DEC kernels.
 396  * All the kudos should go to Dave for this stuff.
 397  *
 398  * Also handles leap second processing, and returns leap offset
 399  */
 400 int second_overflow(time64_t secs)
 401 {
 402         s64 delta;
 403         int leap = 0;
 404         s32 rem;
 405 
 406         /*
 407          * Leap second processing. If in leap-insert state at the end of the
 408          * day, the system clock is set back one second; if in leap-delete
 409          * state, the system clock is set ahead one second.
 410          */
 411         switch (time_state) {
 412         case TIME_OK:
 413                 if (time_status & STA_INS) {
 414                         time_state = TIME_INS;
 415                         div_s64_rem(secs, SECS_PER_DAY, &rem);
 416                         ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
 417                 } else if (time_status & STA_DEL) {
 418                         time_state = TIME_DEL;
 419                         div_s64_rem(secs + 1, SECS_PER_DAY, &rem);
 420                         ntp_next_leap_sec = secs + SECS_PER_DAY - rem;
 421                 }
 422                 break;
 423         case TIME_INS:
 424                 if (!(time_status & STA_INS)) {
 425                         ntp_next_leap_sec = TIME64_MAX;
 426                         time_state = TIME_OK;
 427                 } else if (secs == ntp_next_leap_sec) {
 428                         leap = -1;
 429                         time_state = TIME_OOP;
 430                         printk(KERN_NOTICE
 431                                 "Clock: inserting leap second 23:59:60 UTC\n");
 432                 }
 433                 break;
 434         case TIME_DEL:
 435                 if (!(time_status & STA_DEL)) {
 436                         ntp_next_leap_sec = TIME64_MAX;
 437                         time_state = TIME_OK;
 438                 } else if (secs == ntp_next_leap_sec) {
 439                         leap = 1;
 440                         ntp_next_leap_sec = TIME64_MAX;
 441                         time_state = TIME_WAIT;
 442                         printk(KERN_NOTICE
 443                                 "Clock: deleting leap second 23:59:59 UTC\n");
 444                 }
 445                 break;
 446         case TIME_OOP:
 447                 ntp_next_leap_sec = TIME64_MAX;
 448                 time_state = TIME_WAIT;
 449                 break;
 450         case TIME_WAIT:
 451                 if (!(time_status & (STA_INS | STA_DEL)))
 452                         time_state = TIME_OK;
 453                 break;
 454         }
 455 
 456 
 457         /* Bump the maxerror field */
 458         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 459         if (time_maxerror > NTP_PHASE_LIMIT) {
 460                 time_maxerror = NTP_PHASE_LIMIT;
 461                 time_status |= STA_UNSYNC;
 462         }
 463 
 464         /* Compute the phase adjustment for the next second */
 465         tick_length      = tick_length_base;
 466 
 467         delta            = ntp_offset_chunk(time_offset);
 468         time_offset     -= delta;
 469         tick_length     += delta;
 470 
 471         /* Check PPS signal */
 472         pps_dec_valid();
 473 
 474         if (!time_adjust)
 475                 goto out;
 476 
 477         if (time_adjust > MAX_TICKADJ) {
 478                 time_adjust -= MAX_TICKADJ;
 479                 tick_length += MAX_TICKADJ_SCALED;
 480                 goto out;
 481         }
 482 
 483         if (time_adjust < -MAX_TICKADJ) {
 484                 time_adjust += MAX_TICKADJ;
 485                 tick_length -= MAX_TICKADJ_SCALED;
 486                 goto out;
 487         }
 488 
 489         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 490                                                          << NTP_SCALE_SHIFT;
 491         time_adjust = 0;
 492 
 493 out:
 494         return leap;
 495 }
 496 
 497 static void sync_hw_clock(struct work_struct *work);
 498 static DECLARE_DELAYED_WORK(sync_work, sync_hw_clock);
 499 
 500 static void sched_sync_hw_clock(struct timespec64 now,
 501                                 unsigned long target_nsec, bool fail)
 502 
 503 {
 504         struct timespec64 next;
 505 
 506         ktime_get_real_ts64(&next);
 507         if (!fail)
 508                 next.tv_sec = 659;
 509         else {
 510                 /*
 511                  * Try again as soon as possible. Delaying long periods
 512                  * decreases the accuracy of the work queue timer. Due to this
 513                  * the algorithm is very likely to require a short-sleep retry
 514                  * after the above long sleep to synchronize ts_nsec.
 515                  */
 516                 next.tv_sec = 0;
 517         }
 518 
 519         /* Compute the needed delay that will get to tv_nsec == target_nsec */
 520         next.tv_nsec = target_nsec - next.tv_nsec;
 521         if (next.tv_nsec <= 0)
 522                 next.tv_nsec += NSEC_PER_SEC;
 523         if (next.tv_nsec >= NSEC_PER_SEC) {
 524                 next.tv_sec++;
 525                 next.tv_nsec -= NSEC_PER_SEC;
 526         }
 527 
 528         queue_delayed_work(system_power_efficient_wq, &sync_work,
 529                            timespec64_to_jiffies(&next));
 530 }
 531 
 532 static void sync_rtc_clock(void)
 533 {
 534         unsigned long target_nsec;
 535         struct timespec64 adjust, now;
 536         int rc;
 537 
 538         if (!IS_ENABLED(CONFIG_RTC_SYSTOHC))
 539                 return;
 540 
 541         ktime_get_real_ts64(&now);
 542 
 543         adjust = now;
 544         if (persistent_clock_is_local)
 545                 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
 546 
 547         /*
 548          * The current RTC in use will provide the target_nsec it wants to be
 549          * called at, and does rtc_tv_nsec_ok internally.
 550          */
 551         rc = rtc_set_ntp_time(adjust, &target_nsec);
 552         if (rc == -ENODEV)
 553                 return;
 554 
 555         sched_sync_hw_clock(now, target_nsec, rc);
 556 }
 557 
 558 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 559 int __weak update_persistent_clock64(struct timespec64 now64)
 560 {
 561         return -ENODEV;
 562 }
 563 #endif
 564 
 565 static bool sync_cmos_clock(void)
 566 {
 567         static bool no_cmos;
 568         struct timespec64 now;
 569         struct timespec64 adjust;
 570         int rc = -EPROTO;
 571         long target_nsec = NSEC_PER_SEC / 2;
 572 
 573         if (!IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE))
 574                 return false;
 575 
 576         if (no_cmos)
 577                 return false;
 578 
 579         /*
 580          * Historically update_persistent_clock64() has followed x86
 581          * semantics, which match the MC146818A/etc RTC. This RTC will store
 582          * 'adjust' and then in .5s it will advance once second.
 583          *
 584          * Architectures are strongly encouraged to use rtclib and not
 585          * implement this legacy API.
 586          */
 587         ktime_get_real_ts64(&now);
 588         if (rtc_tv_nsec_ok(-1 * target_nsec, &adjust, &now)) {
 589                 if (persistent_clock_is_local)
 590                         adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
 591                 rc = update_persistent_clock64(adjust);
 592                 /*
 593                  * The machine does not support update_persistent_clock64 even
 594                  * though it defines CONFIG_GENERIC_CMOS_UPDATE.
 595                  */
 596                 if (rc == -ENODEV) {
 597                         no_cmos = true;
 598                         return false;
 599                 }
 600         }
 601 
 602         sched_sync_hw_clock(now, target_nsec, rc);
 603         return true;
 604 }
 605 
 606 /*
 607  * If we have an externally synchronized Linux clock, then update RTC clock
 608  * accordingly every ~11 minutes. Generally RTCs can only store second
 609  * precision, but many RTCs will adjust the phase of their second tick to
 610  * match the moment of update. This infrastructure arranges to call to the RTC
 611  * set at the correct moment to phase synchronize the RTC second tick over
 612  * with the kernel clock.
 613  */
 614 static void sync_hw_clock(struct work_struct *work)
 615 {
 616         if (!ntp_synced())
 617                 return;
 618 
 619         if (sync_cmos_clock())
 620                 return;
 621 
 622         sync_rtc_clock();
 623 }
 624 
 625 void ntp_notify_cmos_timer(void)
 626 {
 627         if (!ntp_synced())
 628                 return;
 629 
 630         if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) ||
 631             IS_ENABLED(CONFIG_RTC_SYSTOHC))
 632                 queue_delayed_work(system_power_efficient_wq, &sync_work, 0);
 633 }
 634 
 635 /*
 636  * Propagate a new txc->status value into the NTP state:
 637  */
 638 static inline void process_adj_status(const struct __kernel_timex *txc)
 639 {
 640         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 641                 time_state = TIME_OK;
 642                 time_status = STA_UNSYNC;
 643                 ntp_next_leap_sec = TIME64_MAX;
 644                 /* restart PPS frequency calibration */
 645                 pps_reset_freq_interval();
 646         }
 647 
 648         /*
 649          * If we turn on PLL adjustments then reset the
 650          * reference time to current time.
 651          */
 652         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 653                 time_reftime = __ktime_get_real_seconds();
 654 
 655         /* only set allowed bits */
 656         time_status &= STA_RONLY;
 657         time_status |= txc->status & ~STA_RONLY;
 658 }
 659 
 660 
 661 static inline void process_adjtimex_modes(const struct __kernel_timex *txc,
 662                                           s32 *time_tai)
 663 {
 664         if (txc->modes & ADJ_STATUS)
 665                 process_adj_status(txc);
 666 
 667         if (txc->modes & ADJ_NANO)
 668                 time_status |= STA_NANO;
 669 
 670         if (txc->modes & ADJ_MICRO)
 671                 time_status &= ~STA_NANO;
 672 
 673         if (txc->modes & ADJ_FREQUENCY) {
 674                 time_freq = txc->freq * PPM_SCALE;
 675                 time_freq = min(time_freq, MAXFREQ_SCALED);
 676                 time_freq = max(time_freq, -MAXFREQ_SCALED);
 677                 /* update pps_freq */
 678                 pps_set_freq(time_freq);
 679         }
 680 
 681         if (txc->modes & ADJ_MAXERROR)
 682                 time_maxerror = txc->maxerror;
 683 
 684         if (txc->modes & ADJ_ESTERROR)
 685                 time_esterror = txc->esterror;
 686 
 687         if (txc->modes & ADJ_TIMECONST) {
 688                 time_constant = txc->constant;
 689                 if (!(time_status & STA_NANO))
 690                         time_constant += 4;
 691                 time_constant = min(time_constant, (long)MAXTC);
 692                 time_constant = max(time_constant, 0l);
 693         }
 694 
 695         if (txc->modes & ADJ_TAI &&
 696                         txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET)
 697                 *time_tai = txc->constant;
 698 
 699         if (txc->modes & ADJ_OFFSET)
 700                 ntp_update_offset(txc->offset);
 701 
 702         if (txc->modes & ADJ_TICK)
 703                 tick_usec = txc->tick;
 704 
 705         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 706                 ntp_update_frequency();
 707 }
 708 
 709 
 710 /*
 711  * adjtimex mainly allows reading (and writing, if superuser) of
 712  * kernel time-keeping variables. used by xntpd.
 713  */
 714 int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts,
 715                   s32 *time_tai, struct audit_ntp_data *ad)
 716 {
 717         int result;
 718 
 719         if (txc->modes & ADJ_ADJTIME) {
 720                 long save_adjust = time_adjust;
 721 
 722                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 723                         /* adjtime() is independent from ntp_adjtime() */
 724                         time_adjust = txc->offset;
 725                         ntp_update_frequency();
 726 
 727                         audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust);
 728                         audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, time_adjust);
 729                 }
 730                 txc->offset = save_adjust;
 731         } else {
 732                 /* If there are input parameters, then process them: */
 733                 if (txc->modes) {
 734                         audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, time_offset);
 735                         audit_ntp_set_old(ad, AUDIT_NTP_FREQ,   time_freq);
 736                         audit_ntp_set_old(ad, AUDIT_NTP_STATUS, time_status);
 737                         audit_ntp_set_old(ad, AUDIT_NTP_TAI,    *time_tai);
 738                         audit_ntp_set_old(ad, AUDIT_NTP_TICK,   tick_usec);
 739 
 740                         process_adjtimex_modes(txc, time_tai);
 741 
 742                         audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, time_offset);
 743                         audit_ntp_set_new(ad, AUDIT_NTP_FREQ,   time_freq);
 744                         audit_ntp_set_new(ad, AUDIT_NTP_STATUS, time_status);
 745                         audit_ntp_set_new(ad, AUDIT_NTP_TAI,    *time_tai);
 746                         audit_ntp_set_new(ad, AUDIT_NTP_TICK,   tick_usec);
 747                 }
 748 
 749                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 750                                   NTP_SCALE_SHIFT);
 751                 if (!(time_status & STA_NANO))
 752                         txc->offset = (u32)txc->offset / NSEC_PER_USEC;
 753         }
 754 
 755         result = time_state;    /* mostly `TIME_OK' */
 756         /* check for errors */
 757         if (is_error_status(time_status))
 758                 result = TIME_ERROR;
 759 
 760         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 761                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 762         txc->maxerror      = time_maxerror;
 763         txc->esterror      = time_esterror;
 764         txc->status        = time_status;
 765         txc->constant      = time_constant;
 766         txc->precision     = 1;
 767         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 768         txc->tick          = tick_usec;
 769         txc->tai           = *time_tai;
 770 
 771         /* fill PPS status fields */
 772         pps_fill_timex(txc);
 773 
 774         txc->time.tv_sec = ts->tv_sec;
 775         txc->time.tv_usec = ts->tv_nsec;
 776         if (!(time_status & STA_NANO))
 777                 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC;
 778 
 779         /* Handle leapsec adjustments */
 780         if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) {
 781                 if ((time_state == TIME_INS) && (time_status & STA_INS)) {
 782                         result = TIME_OOP;
 783                         txc->tai++;
 784                         txc->time.tv_sec--;
 785                 }
 786                 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) {
 787                         result = TIME_WAIT;
 788                         txc->tai--;
 789                         txc->time.tv_sec++;
 790                 }
 791                 if ((time_state == TIME_OOP) &&
 792                                         (ts->tv_sec == ntp_next_leap_sec)) {
 793                         result = TIME_WAIT;
 794                 }
 795         }
 796 
 797         return result;
 798 }
 799 
 800 #ifdef  CONFIG_NTP_PPS
 801 
 802 /* actually struct pps_normtime is good old struct timespec, but it is
 803  * semantically different (and it is the reason why it was invented):
 804  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 805  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 806 struct pps_normtime {
 807         s64             sec;    /* seconds */
 808         long            nsec;   /* nanoseconds */
 809 };
 810 
 811 /* normalize the timestamp so that nsec is in the
 812    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 813 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts)
 814 {
 815         struct pps_normtime norm = {
 816                 .sec = ts.tv_sec,
 817                 .nsec = ts.tv_nsec
 818         };
 819 
 820         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 821                 norm.nsec -= NSEC_PER_SEC;
 822                 norm.sec++;
 823         }
 824 
 825         return norm;
 826 }
 827 
 828 /* get current phase correction and jitter */
 829 static inline long pps_phase_filter_get(long *jitter)
 830 {
 831         *jitter = pps_tf[0] - pps_tf[1];
 832         if (*jitter < 0)
 833                 *jitter = -*jitter;
 834 
 835         /* TODO: test various filters */
 836         return pps_tf[0];
 837 }
 838 
 839 /* add the sample to the phase filter */
 840 static inline void pps_phase_filter_add(long err)
 841 {
 842         pps_tf[2] = pps_tf[1];
 843         pps_tf[1] = pps_tf[0];
 844         pps_tf[0] = err;
 845 }
 846 
 847 /* decrease frequency calibration interval length.
 848  * It is halved after four consecutive unstable intervals.
 849  */
 850 static inline void pps_dec_freq_interval(void)
 851 {
 852         if (--pps_intcnt <= -PPS_INTCOUNT) {
 853                 pps_intcnt = -PPS_INTCOUNT;
 854                 if (pps_shift > PPS_INTMIN) {
 855                         pps_shift--;
 856                         pps_intcnt = 0;
 857                 }
 858         }
 859 }
 860 
 861 /* increase frequency calibration interval length.
 862  * It is doubled after four consecutive stable intervals.
 863  */
 864 static inline void pps_inc_freq_interval(void)
 865 {
 866         if (++pps_intcnt >= PPS_INTCOUNT) {
 867                 pps_intcnt = PPS_INTCOUNT;
 868                 if (pps_shift < PPS_INTMAX) {
 869                         pps_shift++;
 870                         pps_intcnt = 0;
 871                 }
 872         }
 873 }
 874 
 875 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 876  * timestamps
 877  *
 878  * At the end of the calibration interval the difference between the
 879  * first and last MONOTONIC_RAW clock timestamps divided by the length
 880  * of the interval becomes the frequency update. If the interval was
 881  * too long, the data are discarded.
 882  * Returns the difference between old and new frequency values.
 883  */
 884 static long hardpps_update_freq(struct pps_normtime freq_norm)
 885 {
 886         long delta, delta_mod;
 887         s64 ftemp;
 888 
 889         /* check if the frequency interval was too long */
 890         if (freq_norm.sec > (2 << pps_shift)) {
 891                 time_status |= STA_PPSERROR;
 892                 pps_errcnt++;
 893                 pps_dec_freq_interval();
 894                 printk_deferred(KERN_ERR
 895                         "hardpps: PPSERROR: interval too long - %lld s\n",
 896                         freq_norm.sec);
 897                 return 0;
 898         }
 899 
 900         /* here the raw frequency offset and wander (stability) is
 901          * calculated. If the wander is less than the wander threshold
 902          * the interval is increased; otherwise it is decreased.
 903          */
 904         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 905                         freq_norm.sec);
 906         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 907         pps_freq = ftemp;
 908         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 909                 printk_deferred(KERN_WARNING
 910                                 "hardpps: PPSWANDER: change=%ld\n", delta);
 911                 time_status |= STA_PPSWANDER;
 912                 pps_stbcnt++;
 913                 pps_dec_freq_interval();
 914         } else {        /* good sample */
 915                 pps_inc_freq_interval();
 916         }
 917 
 918         /* the stability metric is calculated as the average of recent
 919          * frequency changes, but is used only for performance
 920          * monitoring
 921          */
 922         delta_mod = delta;
 923         if (delta_mod < 0)
 924                 delta_mod = -delta_mod;
 925         pps_stabil += (div_s64(((s64)delta_mod) <<
 926                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 927                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 928 
 929         /* if enabled, the system clock frequency is updated */
 930         if ((time_status & STA_PPSFREQ) != 0 &&
 931             (time_status & STA_FREQHOLD) == 0) {
 932                 time_freq = pps_freq;
 933                 ntp_update_frequency();
 934         }
 935 
 936         return delta;
 937 }
 938 
 939 /* correct REALTIME clock phase error against PPS signal */
 940 static void hardpps_update_phase(long error)
 941 {
 942         long correction = -error;
 943         long jitter;
 944 
 945         /* add the sample to the median filter */
 946         pps_phase_filter_add(correction);
 947         correction = pps_phase_filter_get(&jitter);
 948 
 949         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 950          * threshold, the sample is discarded; otherwise, if so enabled,
 951          * the time offset is updated.
 952          */
 953         if (jitter > (pps_jitter << PPS_POPCORN)) {
 954                 printk_deferred(KERN_WARNING
 955                                 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 956                                 jitter, (pps_jitter << PPS_POPCORN));
 957                 time_status |= STA_PPSJITTER;
 958                 pps_jitcnt++;
 959         } else if (time_status & STA_PPSTIME) {
 960                 /* correct the time using the phase offset */
 961                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 962                                 NTP_INTERVAL_FREQ);
 963                 /* cancel running adjtime() */
 964                 time_adjust = 0;
 965         }
 966         /* update jitter */
 967         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 968 }
 969 
 970 /*
 971  * __hardpps() - discipline CPU clock oscillator to external PPS signal
 972  *
 973  * This routine is called at each PPS signal arrival in order to
 974  * discipline the CPU clock oscillator to the PPS signal. It takes two
 975  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 976  * is used to correct clock phase error and the latter is used to
 977  * correct the frequency.
 978  *
 979  * This code is based on David Mills's reference nanokernel
 980  * implementation. It was mostly rewritten but keeps the same idea.
 981  */
 982 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts)
 983 {
 984         struct pps_normtime pts_norm, freq_norm;
 985 
 986         pts_norm = pps_normalize_ts(*phase_ts);
 987 
 988         /* clear the error bits, they will be set again if needed */
 989         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 990 
 991         /* indicate signal presence */
 992         time_status |= STA_PPSSIGNAL;
 993         pps_valid = PPS_VALID;
 994 
 995         /* when called for the first time,
 996          * just start the frequency interval */
 997         if (unlikely(pps_fbase.tv_sec == 0)) {
 998                 pps_fbase = *raw_ts;
 999                 return;
1000         }
1001 
1002         /* ok, now we have a base for frequency calculation */
1003         freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase));
1004 
1005         /* check that the signal is in the range
1006          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
1007         if ((freq_norm.sec == 0) ||
1008                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
1009                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
1010                 time_status |= STA_PPSJITTER;
1011                 /* restart the frequency calibration interval */
1012                 pps_fbase = *raw_ts;
1013                 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n");
1014                 return;
1015         }
1016 
1017         /* signal is ok */
1018 
1019         /* check if the current frequency interval is finished */
1020         if (freq_norm.sec >= (1 << pps_shift)) {
1021                 pps_calcnt++;
1022                 /* restart the frequency calibration interval */
1023                 pps_fbase = *raw_ts;
1024                 hardpps_update_freq(freq_norm);
1025         }
1026 
1027         hardpps_update_phase(pts_norm.nsec);
1028 
1029 }
1030 #endif  /* CONFIG_NTP_PPS */
1031 
1032 static int __init ntp_tick_adj_setup(char *str)
1033 {
1034         int rc = kstrtos64(str, 0, &ntp_tick_adj);
1035         if (rc)
1036                 return rc;
1037 
1038         ntp_tick_adj <<= NTP_SCALE_SHIFT;
1039         return 1;
1040 }
1041 
1042 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
1043 
1044 void __init ntp_init(void)
1045 {
1046         ntp_clear();
1047 }