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 "tick-internal.h"
  21
  22 /*
  23  * NTP timekeeping variables:
  24  */
  25
  26 DEFINE_RAW_SPINLOCK(ntp_lock);
  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 MAX_TICKADJ             500LL           /* usecs */
  39 #define MAX_TICKADJ_SCALED \
  40         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  41
  42 /*
  43  * phase-lock loop variables
  44  */
  45
  46 /*
  47  * clock synchronization status
  48  *
  49  * (TIME_ERROR prevents overwriting the CMOS clock)
  50  */
  51 static int                      time_state = TIME_OK;
  52
  53 /* clock status bits:                                                   */
  54 static int                      time_status = STA_UNSYNC;
  55
  56 /* TAI offset (secs):                                                   */
  57 static long                     time_tai;
  58
  59 /* time adjustment (nsecs):                                             */
  60 static s64                      time_offset;
  61
  62 /* pll time constant:                                                   */
  63 static long                     time_constant = 2;
  64
  65 /* maximum error (usecs):                                               */
  66 static long                     time_maxerror = NTP_PHASE_LIMIT;
  67
  68 /* estimated error (usecs):                                             */
  69 static long                     time_esterror = NTP_PHASE_LIMIT;
  70
  71 /* frequency offset (scaled nsecs/secs):                                */
  72 static s64                      time_freq;
  73
  74 /* time at last adjustment (secs):                                      */
  75 static long                     time_reftime;
  76
  77 static long                     time_adjust;
  78
  79 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
  80 static s64                      ntp_tick_adj;
  81
  82 #ifdef CONFIG_NTP_PPS
  83
  84 /*
  85  * The following variables are used when a pulse-per-second (PPS) signal
  86  * is available. They establish the engineering parameters of the clock
  87  * discipline loop when controlled by the PPS signal.
  88  */
  89 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
  90 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
  91 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
  92 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
  93 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
  94                                    increase pps_shift or consecutive bad
  95                                    intervals to decrease it */
  96 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
  97
  98 static int pps_valid;           /* signal watchdog counter */
  99 static long pps_tf[3];          /* phase median filter */
 100 static long pps_jitter;         /* current jitter (ns) */
 101 static struct timespec pps_fbase; /* beginning of the last freq interval */
 102 static int pps_shift;           /* current interval duration (s) (shift) */
 103 static int pps_intcnt;          /* interval counter */
 104 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
 105 static long pps_stabil;         /* current stability (scaled ns/s) */
 106
 107 /*
 108  * PPS signal quality monitors
 109  */
 110 static long pps_calcnt;         /* calibration intervals */
 111 static long pps_jitcnt;         /* jitter limit exceeded */
 112 static long pps_stbcnt;         /* stability limit exceeded */
 113 static long pps_errcnt;         /* calibration errors */
 114
 115
 116 /* PPS kernel consumer compensates the whole phase error immediately.
 117  * Otherwise, reduce the offset by a fixed factor times the time constant.
 118  */
 119 static inline s64 ntp_offset_chunk(s64 offset)
 120 {
 121         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
 122                 return offset;
 123         else
 124                 return shift_right(offset, SHIFT_PLL + time_constant);
 125 }
 126
 127 static inline void pps_reset_freq_interval(void)
 128 {
 129         /* the PPS calibration interval may end
 130            surprisingly early */
 131         pps_shift = PPS_INTMIN;
 132         pps_intcnt = 0;
 133 }
 134
 135 /**
 136  * pps_clear - Clears the PPS state variables
 137  *
 138  * Must be called while holding a write on the ntp_lock
 139  */
 140 static inline void pps_clear(void)
 141 {
 142         pps_reset_freq_interval();
 143         pps_tf[0] = 0;
 144         pps_tf[1] = 0;
 145         pps_tf[2] = 0;
 146         pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
 147         pps_freq = 0;
 148 }
 149
 150 /* Decrease pps_valid to indicate that another second has passed since
 151  * the last PPS signal. When it reaches 0, indicate that PPS signal is
 152  * missing.
 153  *
 154  * Must be called while holding a write on the ntp_lock
 155  */
 156 static inline void pps_dec_valid(void)
 157 {
 158         if (pps_valid > 0)
 159                 pps_valid--;
 160         else {
 161                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 162                                  STA_PPSWANDER | STA_PPSERROR);
 163                 pps_clear();
 164         }
 165 }
 166
 167 static inline void pps_set_freq(s64 freq)
 168 {
 169         pps_freq = freq;
 170 }
 171
 172 static inline int is_error_status(int status)
 173 {
 174         return (time_status & (STA_UNSYNC|STA_CLOCKERR))
 175                 /* PPS signal lost when either PPS time or
 176                  * PPS frequency synchronization requested
 177                  */
 178                 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
 179                         && !(time_status & STA_PPSSIGNAL))
 180                 /* PPS jitter exceeded when
 181                  * PPS time synchronization requested */
 182                 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
 183                         == (STA_PPSTIME|STA_PPSJITTER))
 184                 /* PPS wander exceeded or calibration error when
 185                  * PPS frequency synchronization requested
 186                  */
 187                 || ((time_status & STA_PPSFREQ)
 188                         && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
 189 }
 190
 191 static inline void pps_fill_timex(struct timex *txc)
 192 {
 193         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 194                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 195         txc->jitter        = pps_jitter;
 196         if (!(time_status & STA_NANO))
 197                 txc->jitter /= NSEC_PER_USEC;
 198         txc->shift         = pps_shift;
 199         txc->stabil        = pps_stabil;
 200         txc->jitcnt        = pps_jitcnt;
 201         txc->calcnt        = pps_calcnt;
 202         txc->errcnt        = pps_errcnt;
 203         txc->stbcnt        = pps_stbcnt;
 204 }
 205
 206 #else /* !CONFIG_NTP_PPS */
 207
 208 static inline s64 ntp_offset_chunk(s64 offset)
 209 {
 210         return shift_right(offset, SHIFT_PLL + time_constant);
 211 }
 212
 213 static inline void pps_reset_freq_interval(void) {}
 214 static inline void pps_clear(void) {}
 215 static inline void pps_dec_valid(void) {}
 216 static inline void pps_set_freq(s64 freq) {}
 217
 218 static inline int is_error_status(int status)
 219 {
 220         return status & (STA_UNSYNC|STA_CLOCKERR);
 221 }
 222
 223 static inline void pps_fill_timex(struct timex *txc)
 224 {
 225         /* PPS is not implemented, so these are zero */
 226         txc->ppsfreq       = 0;
 227         txc->jitter        = 0;
 228         txc->shift         = 0;
 229         txc->stabil        = 0;
 230         txc->jitcnt        = 0;
 231         txc->calcnt        = 0;
 232         txc->errcnt        = 0;
 233         txc->stbcnt        = 0;
 234 }
 235
 236 #endif /* CONFIG_NTP_PPS */
 237
 238
 239 /**
 240  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 241  *
 242  */
 243 static inline int ntp_synced(void)
 244 {
 245         return !(time_status & STA_UNSYNC);
 246 }
 247
 248
 249 /*
 250  * NTP methods:
 251  */
 252
 253 /*
 254  * Update (tick_length, tick_length_base, tick_nsec), based
 255  * on (tick_usec, ntp_tick_adj, time_freq):
 256  */
 257 static void ntp_update_frequency(void)
 258 {
 259         u64 second_length;
 260         u64 new_base;
 261
 262         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 263                                                 << NTP_SCALE_SHIFT;
 264
 265         second_length           += ntp_tick_adj;
 266         second_length           += time_freq;
 267
 268         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 269         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 270
 271         /*
 272          * Don't wait for the next second_overflow, apply
 273          * the change to the tick length immediately:
 274          */
 275         tick_length             += new_base - tick_length_base;
 276         tick_length_base         = new_base;
 277 }
 278
 279 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 280 {
 281         time_status &= ~STA_MODE;
 282
 283         if (secs < MINSEC)
 284                 return 0;
 285
 286         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 287                 return 0;
 288
 289         time_status |= STA_MODE;
 290
 291         return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 292 }
 293
 294 static void ntp_update_offset(long offset)
 295 {
 296         s64 freq_adj;
 297         s64 offset64;
 298         long secs;
 299
 300         if (!(time_status & STA_PLL))
 301                 return;
 302
 303         if (!(time_status & STA_NANO))
 304                 offset *= NSEC_PER_USEC;
 305
 306         /*
 307          * Scale the phase adjustment and
 308          * clamp to the operating range.
 309          */
 310         offset = min(offset, MAXPHASE);
 311         offset = max(offset, -MAXPHASE);
 312
 313         /*
 314          * Select how the frequency is to be controlled
 315          * and in which mode (PLL or FLL).
 316          */
 317         secs = get_seconds() - time_reftime;
 318         if (unlikely(time_status & STA_FREQHOLD))
 319                 secs = 0;
 320
 321         time_reftime = get_seconds();
 322
 323         offset64    = offset;
 324         freq_adj    = ntp_update_offset_fll(offset64, secs);
 325
 326         /*
 327          * Clamp update interval to reduce PLL gain with low
 328          * sampling rate (e.g. intermittent network connection)
 329          * to avoid instability.
 330          */
 331         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 332                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
 333
 334         freq_adj    += (offset64 * secs) <<
 335                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 336
 337         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 338
 339         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 340
 341         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 342 }
 343
 344 /**
 345  * ntp_clear - Clears the NTP state variables
 346  */
 347 void ntp_clear(void)
 348 {
 349         unsigned long flags;
 350
 351         raw_spin_lock_irqsave(&ntp_lock, flags);
 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         /* Clear PPS state variables */
 364         pps_clear();
 365         raw_spin_unlock_irqrestore(&ntp_lock, flags);
 366
 367 }
 368
 369
 370 u64 ntp_tick_length(void)
 371 {
 372         unsigned long flags;
 373         s64 ret;
 374
 375         raw_spin_lock_irqsave(&ntp_lock, flags);
 376         ret = tick_length;
 377         raw_spin_unlock_irqrestore(&ntp_lock, flags);
 378         return ret;
 379 }
 380
 381
 382 /*
 383  * this routine handles the overflow of the microsecond field
 384  *
 385  * The tricky bits of code to handle the accurate clock support
 386  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 387  * They were originally developed for SUN and DEC kernels.
 388  * All the kudos should go to Dave for this stuff.
 389  *
 390  * Also handles leap second processing, and returns leap offset
 391  */
 392 int second_overflow(unsigned long secs)
 393 {
 394         s64 delta;
 395         int leap = 0;
 396         unsigned long flags;
 397
 398         raw_spin_lock_irqsave(&ntp_lock, flags);
 399
 400         /*
 401          * Leap second processing. If in leap-insert state at the end of the
 402          * day, the system clock is set back one second; if in leap-delete
 403          * state, the system clock is set ahead one second.
 404          */
 405         switch (time_state) {
 406         case TIME_OK:
 407                 if (time_status & STA_INS)
 408                         time_state = TIME_INS;
 409                 else if (time_status & STA_DEL)
 410                         time_state = TIME_DEL;
 411                 break;
 412         case TIME_INS:
 413                 if (!(time_status & STA_INS))
 414                         time_state = TIME_OK;
 415                 else if (secs % 86400 == 0) {
 416                         leap = -1;
 417                         time_state = TIME_OOP;
 418                         time_tai++;
 419                         printk(KERN_NOTICE
 420                                 "Clock: inserting leap second 23:59:60 UTC\n");
 421                 }
 422                 break;
 423         case TIME_DEL:
 424                 if (!(time_status & STA_DEL))
 425                         time_state = TIME_OK;
 426                 else if ((secs + 1) % 86400 == 0) {
 427                         leap = 1;
 428                         time_tai--;
 429                         time_state = TIME_WAIT;
 430                         printk(KERN_NOTICE
 431                                 "Clock: deleting leap second 23:59:59 UTC\n");
 432                 }
 433                 break;
 434         case TIME_OOP:
 435                 time_state = TIME_WAIT;
 436                 break;
 437
 438         case TIME_WAIT:
 439                 if (!(time_status & (STA_INS | STA_DEL)))
 440                         time_state = TIME_OK;
 441                 break;
 442         }
 443
 444
 445         /* Bump the maxerror field */
 446         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 447         if (time_maxerror > NTP_PHASE_LIMIT) {
 448                 time_maxerror = NTP_PHASE_LIMIT;
 449                 time_status |= STA_UNSYNC;
 450         }
 451
 452         /* Compute the phase adjustment for the next second */
 453         tick_length      = tick_length_base;
 454
 455         delta            = ntp_offset_chunk(time_offset);
 456         time_offset     -= delta;
 457         tick_length     += delta;
 458
 459         /* Check PPS signal */
 460         pps_dec_valid();
 461
 462         if (!time_adjust)
 463                 goto out;
 464
 465         if (time_adjust > MAX_TICKADJ) {
 466                 time_adjust -= MAX_TICKADJ;
 467                 tick_length += MAX_TICKADJ_SCALED;
 468                 goto out;
 469         }
 470
 471         if (time_adjust < -MAX_TICKADJ) {
 472                 time_adjust += MAX_TICKADJ;
 473                 tick_length -= MAX_TICKADJ_SCALED;
 474                 goto out;
 475         }
 476
 477         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 478                                                          << NTP_SCALE_SHIFT;
 479         time_adjust = 0;
 480
 481 out:
 482         raw_spin_unlock_irqrestore(&ntp_lock, flags);
 483
 484         return leap;
 485 }
 486
 487 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
 488 static void sync_cmos_clock(struct work_struct *work);
 489
 490 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
 491
 492 static 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                 struct timespec adjust = now;
 515
 516                 fail = -ENODEV;
 517                 if (persistent_clock_is_local)
 518                         adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
 519 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 520                 fail = update_persistent_clock(adjust);
 521 #endif
 522 #ifdef CONFIG_RTC_SYSTOHC
 523                 if (fail == -ENODEV)
 524                         fail = rtc_set_ntp_time(adjust);
 525 #endif
 526         }
 527
 528         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 529         if (next.tv_nsec <= 0)
 530                 next.tv_nsec += NSEC_PER_SEC;
 531
 532         if (!fail || fail == -ENODEV)
 533                 next.tv_sec = 659;
 534         else
 535                 next.tv_sec = 0;
 536
 537         if (next.tv_nsec >= NSEC_PER_SEC) {
 538                 next.tv_sec++;
 539                 next.tv_nsec -= NSEC_PER_SEC;
 540         }
 541         schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
 542 }
 543
 544 static void notify_cmos_timer(void)
 545 {
 546         schedule_delayed_work(&sync_cmos_work, 0);
 547 }
 548
 549 #else
 550 static inline void notify_cmos_timer(void) { }
 551 #endif
 552
 553
 554 /*
 555  * Propagate a new txc->status value into the NTP state:
 556  */
 557 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
 558 {
 559         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 560                 time_state = TIME_OK;
 561                 time_status = STA_UNSYNC;
 562                 /* restart PPS frequency calibration */
 563                 pps_reset_freq_interval();
 564         }
 565
 566         /*
 567          * If we turn on PLL adjustments then reset the
 568          * reference time to current time.
 569          */
 570         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 571                 time_reftime = get_seconds();
 572
 573         /* only set allowed bits */
 574         time_status &= STA_RONLY;
 575         time_status |= txc->status & ~STA_RONLY;
 576 }
 577
 578 /*
 579  * Called with ntp_lock held, so we can access and modify
 580  * all the global NTP state:
 581  */
 582 static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
 583 {
 584         if (txc->modes & ADJ_STATUS)
 585                 process_adj_status(txc, ts);
 586
 587         if (txc->modes & ADJ_NANO)
 588                 time_status |= STA_NANO;
 589
 590         if (txc->modes & ADJ_MICRO)
 591                 time_status &= ~STA_NANO;
 592
 593         if (txc->modes & ADJ_FREQUENCY) {
 594                 time_freq = txc->freq * PPM_SCALE;
 595                 time_freq = min(time_freq, MAXFREQ_SCALED);
 596                 time_freq = max(time_freq, -MAXFREQ_SCALED);
 597                 /* update pps_freq */
 598                 pps_set_freq(time_freq);
 599         }
 600
 601         if (txc->modes & ADJ_MAXERROR)
 602                 time_maxerror = txc->maxerror;
 603
 604         if (txc->modes & ADJ_ESTERROR)
 605                 time_esterror = txc->esterror;
 606
 607         if (txc->modes & ADJ_TIMECONST) {
 608                 time_constant = txc->constant;
 609                 if (!(time_status & STA_NANO))
 610                         time_constant += 4;
 611                 time_constant = min(time_constant, (long)MAXTC);
 612                 time_constant = max(time_constant, 0l);
 613         }
 614
 615         if (txc->modes & ADJ_TAI && txc->constant > 0)
 616                 time_tai = txc->constant;
 617
 618         if (txc->modes & ADJ_OFFSET)
 619                 ntp_update_offset(txc->offset);
 620
 621         if (txc->modes & ADJ_TICK)
 622                 tick_usec = txc->tick;
 623
 624         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 625                 ntp_update_frequency();
 626 }
 627
 628 /*
 629  * adjtimex mainly allows reading (and writing, if superuser) of
 630  * kernel time-keeping variables. used by xntpd.
 631  */
 632 int do_adjtimex(struct timex *txc)
 633 {
 634         struct timespec ts;
 635         int result;
 636
 637         /* Validate the data before disabling interrupts */
 638         if (txc->modes & ADJ_ADJTIME) {
 639                 /* singleshot must not be used with any other mode bits */
 640                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
 641                         return -EINVAL;
 642                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
 643                     !capable(CAP_SYS_TIME))
 644                         return -EPERM;
 645         } else {
 646                 /* In order to modify anything, you gotta be super-user! */
 647                  if (txc->modes && !capable(CAP_SYS_TIME))
 648                         return -EPERM;
 649
 650                 /*
 651                  * if the quartz is off by more than 10% then
 652                  * something is VERY wrong!
 653                  */
 654                 if (txc->modes & ADJ_TICK &&
 655                     (txc->tick <  900000/USER_HZ ||
 656                      txc->tick > 1100000/USER_HZ))
 657                         return -EINVAL;
 658         }
 659
 660         if (txc->modes & ADJ_SETOFFSET) {
 661                 struct timespec delta;
 662                 delta.tv_sec  = txc->time.tv_sec;
 663                 delta.tv_nsec = txc->time.tv_usec;
 664                 if (!capable(CAP_SYS_TIME))
 665                         return -EPERM;
 666                 if (!(txc->modes & ADJ_NANO))
 667                         delta.tv_nsec *= 1000;
 668                 result = timekeeping_inject_offset(&delta);
 669                 if (result)
 670                         return result;
 671         }
 672
 673         getnstimeofday(&ts);
 674
 675         raw_spin_lock_irq(&ntp_lock);
 676
 677         if (txc->modes & ADJ_ADJTIME) {
 678                 long save_adjust = time_adjust;
 679
 680                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 681                         /* adjtime() is independent from ntp_adjtime() */
 682                         time_adjust = txc->offset;
 683                         ntp_update_frequency();
 684                 }
 685                 txc->offset = save_adjust;
 686         } else {
 687
 688                 /* If there are input parameters, then process them: */
 689                 if (txc->modes)
 690                         process_adjtimex_modes(txc, &ts);
 691
 692                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 693                                   NTP_SCALE_SHIFT);
 694                 if (!(time_status & STA_NANO))
 695                         txc->offset /= NSEC_PER_USEC;
 696         }
 697
 698         result = time_state;    /* mostly `TIME_OK' */
 699         /* check for errors */
 700         if (is_error_status(time_status))
 701                 result = TIME_ERROR;
 702
 703         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 704                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 705         txc->maxerror      = time_maxerror;
 706         txc->esterror      = time_esterror;
 707         txc->status        = time_status;
 708         txc->constant      = time_constant;
 709         txc->precision     = 1;
 710         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 711         txc->tick          = tick_usec;
 712         txc->tai           = time_tai;
 713
 714         /* fill PPS status fields */
 715         pps_fill_timex(txc);
 716
 717         raw_spin_unlock_irq(&ntp_lock);
 718
 719         txc->time.tv_sec = ts.tv_sec;
 720         txc->time.tv_usec = ts.tv_nsec;
 721         if (!(time_status & STA_NANO))
 722                 txc->time.tv_usec /= NSEC_PER_USEC;
 723
 724         notify_cmos_timer();
 725
 726         return result;
 727 }
 728
 729 #ifdef  CONFIG_NTP_PPS
 730
 731 /* actually struct pps_normtime is good old struct timespec, but it is
 732  * semantically different (and it is the reason why it was invented):
 733  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 734  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 735 struct pps_normtime {
 736         __kernel_time_t sec;    /* seconds */
 737         long            nsec;   /* nanoseconds */
 738 };
 739
 740 /* normalize the timestamp so that nsec is in the
 741    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 742 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
 743 {
 744         struct pps_normtime norm = {
 745                 .sec = ts.tv_sec,
 746                 .nsec = ts.tv_nsec
 747         };
 748
 749         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 750                 norm.nsec -= NSEC_PER_SEC;
 751                 norm.sec++;
 752         }
 753
 754         return norm;
 755 }
 756
 757 /* get current phase correction and jitter */
 758 static inline long pps_phase_filter_get(long *jitter)
 759 {
 760         *jitter = pps_tf[0] - pps_tf[1];
 761         if (*jitter < 0)
 762                 *jitter = -*jitter;
 763
 764         /* TODO: test various filters */
 765         return pps_tf[0];
 766 }
 767
 768 /* add the sample to the phase filter */
 769 static inline void pps_phase_filter_add(long err)
 770 {
 771         pps_tf[2] = pps_tf[1];
 772         pps_tf[1] = pps_tf[0];
 773         pps_tf[0] = err;
 774 }
 775
 776 /* decrease frequency calibration interval length.
 777  * It is halved after four consecutive unstable intervals.
 778  */
 779 static inline void pps_dec_freq_interval(void)
 780 {
 781         if (--pps_intcnt <= -PPS_INTCOUNT) {
 782                 pps_intcnt = -PPS_INTCOUNT;
 783                 if (pps_shift > PPS_INTMIN) {
 784                         pps_shift--;
 785                         pps_intcnt = 0;
 786                 }
 787         }
 788 }
 789
 790 /* increase frequency calibration interval length.
 791  * It is doubled after four consecutive stable intervals.
 792  */
 793 static inline void pps_inc_freq_interval(void)
 794 {
 795         if (++pps_intcnt >= PPS_INTCOUNT) {
 796                 pps_intcnt = PPS_INTCOUNT;
 797                 if (pps_shift < PPS_INTMAX) {
 798                         pps_shift++;
 799                         pps_intcnt = 0;
 800                 }
 801         }
 802 }
 803
 804 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 805  * timestamps
 806  *
 807  * At the end of the calibration interval the difference between the
 808  * first and last MONOTONIC_RAW clock timestamps divided by the length
 809  * of the interval becomes the frequency update. If the interval was
 810  * too long, the data are discarded.
 811  * Returns the difference between old and new frequency values.
 812  */
 813 static long hardpps_update_freq(struct pps_normtime freq_norm)
 814 {
 815         long delta, delta_mod;
 816         s64 ftemp;
 817
 818         /* check if the frequency interval was too long */
 819         if (freq_norm.sec > (2 << pps_shift)) {
 820                 time_status |= STA_PPSERROR;
 821                 pps_errcnt++;
 822                 pps_dec_freq_interval();
 823                 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
 824                                 freq_norm.sec);
 825                 return 0;
 826         }
 827
 828         /* here the raw frequency offset and wander (stability) is
 829          * calculated. If the wander is less than the wander threshold
 830          * the interval is increased; otherwise it is decreased.
 831          */
 832         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 833                         freq_norm.sec);
 834         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 835         pps_freq = ftemp;
 836         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 837                 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
 838                 time_status |= STA_PPSWANDER;
 839                 pps_stbcnt++;
 840                 pps_dec_freq_interval();
 841         } else {        /* good sample */
 842                 pps_inc_freq_interval();
 843         }
 844
 845         /* the stability metric is calculated as the average of recent
 846          * frequency changes, but is used only for performance
 847          * monitoring
 848          */
 849         delta_mod = delta;
 850         if (delta_mod < 0)
 851                 delta_mod = -delta_mod;
 852         pps_stabil += (div_s64(((s64)delta_mod) <<
 853                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 854                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 855
 856         /* if enabled, the system clock frequency is updated */
 857         if ((time_status & STA_PPSFREQ) != 0 &&
 858             (time_status & STA_FREQHOLD) == 0) {
 859                 time_freq = pps_freq;
 860                 ntp_update_frequency();
 861         }
 862
 863         return delta;
 864 }
 865
 866 /* correct REALTIME clock phase error against PPS signal */
 867 static void hardpps_update_phase(long error)
 868 {
 869         long correction = -error;
 870         long jitter;
 871
 872         /* add the sample to the median filter */
 873         pps_phase_filter_add(correction);
 874         correction = pps_phase_filter_get(&jitter);
 875
 876         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 877          * threshold, the sample is discarded; otherwise, if so enabled,
 878          * the time offset is updated.
 879          */
 880         if (jitter > (pps_jitter << PPS_POPCORN)) {
 881                 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 882                        jitter, (pps_jitter << PPS_POPCORN));
 883                 time_status |= STA_PPSJITTER;
 884                 pps_jitcnt++;
 885         } else if (time_status & STA_PPSTIME) {
 886                 /* correct the time using the phase offset */
 887                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 888                                 NTP_INTERVAL_FREQ);
 889                 /* cancel running adjtime() */
 890                 time_adjust = 0;
 891         }
 892         /* update jitter */
 893         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 894 }
 895
 896 /*
 897  * hardpps() - discipline CPU clock oscillator to external PPS signal
 898  *
 899  * This routine is called at each PPS signal arrival in order to
 900  * discipline the CPU clock oscillator to the PPS signal. It takes two
 901  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 902  * is used to correct clock phase error and the latter is used to
 903  * correct the frequency.
 904  *
 905  * This code is based on David Mills's reference nanokernel
 906  * implementation. It was mostly rewritten but keeps the same idea.
 907  */
 908 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 909 {
 910         struct pps_normtime pts_norm, freq_norm;
 911         unsigned long flags;
 912
 913         pts_norm = pps_normalize_ts(*phase_ts);
 914
 915         raw_spin_lock_irqsave(&ntp_lock, flags);
 916
 917         /* clear the error bits, they will be set again if needed */
 918         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 919
 920         /* indicate signal presence */
 921         time_status |= STA_PPSSIGNAL;
 922         pps_valid = PPS_VALID;
 923
 924         /* when called for the first time,
 925          * just start the frequency interval */
 926         if (unlikely(pps_fbase.tv_sec == 0)) {
 927                 pps_fbase = *raw_ts;
 928                 raw_spin_unlock_irqrestore(&ntp_lock, flags);
 929                 return;
 930         }
 931
 932         /* ok, now we have a base for frequency calculation */
 933         freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
 934
 935         /* check that the signal is in the range
 936          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 937         if ((freq_norm.sec == 0) ||
 938                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 939                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 940                 time_status |= STA_PPSJITTER;
 941                 /* restart the frequency calibration interval */
 942                 pps_fbase = *raw_ts;
 943                 raw_spin_unlock_irqrestore(&ntp_lock, flags);
 944                 pr_err("hardpps: PPSJITTER: bad pulse\n");
 945                 return;
 946         }
 947
 948         /* signal is ok */
 949
 950         /* check if the current frequency interval is finished */
 951         if (freq_norm.sec >= (1 << pps_shift)) {
 952                 pps_calcnt++;
 953                 /* restart the frequency calibration interval */
 954                 pps_fbase = *raw_ts;
 955                 hardpps_update_freq(freq_norm);
 956         }
 957
 958         hardpps_update_phase(pts_norm.nsec);
 959
 960         raw_spin_unlock_irqrestore(&ntp_lock, flags);
 961 }
 962 EXPORT_SYMBOL(hardpps);
 963
 964 #endif  /* CONFIG_NTP_PPS */
 965
 966 static int __init ntp_tick_adj_setup(char *str)
 967 {
 968         ntp_tick_adj = simple_strtol(str, NULL, 0);
 969         ntp_tick_adj <<= NTP_SCALE_SHIFT;
 970
 971         return 1;
 972 }
 973
 974 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
 975
 976 void __init ntp_init(void)
 977 {
 978         ntp_clear();
 979 }