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
  19 /*
  20  * NTP timekeeping variables:
  21  */
  22
  23 /* USER_HZ period (usecs): */
  24 unsigned long                   tick_usec = TICK_USEC;
  25
  26 /* ACTHZ period (nsecs): */
  27 unsigned long                   tick_nsec;
  28
  29 u64                             tick_length;
  30 static u64                      tick_length_base;
  31
  32 static struct hrtimer           leap_timer;
  33
  34 #define MAX_TICKADJ             500LL           /* usecs */
  35 #define MAX_TICKADJ_SCALED \
  36         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  37
  38 /*
  39  * phase-lock loop variables
  40  */
  41
  42 /*
  43  * clock synchronization status
  44  *
  45  * (TIME_ERROR prevents overwriting the CMOS clock)
  46  */
  47 static int                      time_state = TIME_OK;
  48
  49 /* clock status bits:                                                   */
  50 int                             time_status = STA_UNSYNC;
  51
  52 /* TAI offset (secs):                                                   */
  53 static long                     time_tai;
  54
  55 /* time adjustment (nsecs):                                             */
  56 static s64                      time_offset;
  57
  58 /* pll time constant:                                                   */
  59 static long                     time_constant = 2;
  60
  61 /* maximum error (usecs):                                               */
  62 static long                     time_maxerror = NTP_PHASE_LIMIT;
  63
  64 /* estimated error (usecs):                                             */
  65 static long                     time_esterror = NTP_PHASE_LIMIT;
  66
  67 /* frequency offset (scaled nsecs/secs):                                */
  68 static s64                      time_freq;
  69
  70 /* time at last adjustment (secs):                                      */
  71 static long                     time_reftime;
  72
  73 static long                     time_adjust;
  74
  75 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
  76 static s64                      ntp_tick_adj;
  77
  78 #ifdef CONFIG_NTP_PPS
  79
  80 /*
  81  * The following variables are used when a pulse-per-second (PPS) signal
  82  * is available. They establish the engineering parameters of the clock
  83  * discipline loop when controlled by the PPS signal.
  84  */
  85 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
  86 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
  87 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
  88 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
  89 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
  90                                    increase pps_shift or consecutive bad
  91                                    intervals to decrease it */
  92 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
  93
  94 static int pps_valid;           /* signal watchdog counter */
  95 static long pps_tf[3];          /* phase median filter */
  96 static long pps_jitter;         /* current jitter (ns) */
  97 static struct timespec pps_fbase; /* beginning of the last freq interval */
  98 static int pps_shift;           /* current interval duration (s) (shift) */
  99 static int pps_intcnt;          /* interval counter */
 100 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
 101 static long pps_stabil;         /* current stability (scaled ns/s) */
 102
 103 /*
 104  * PPS signal quality monitors
 105  */
 106 static long pps_calcnt;         /* calibration intervals */
 107 static long pps_jitcnt;         /* jitter limit exceeded */
 108 static long pps_stbcnt;         /* stability limit exceeded */
 109 static long pps_errcnt;         /* calibration errors */
 110
 111
 112 /* PPS kernel consumer compensates the whole phase error immediately.
 113  * Otherwise, reduce the offset by a fixed factor times the time constant.
 114  */
 115 static inline s64 ntp_offset_chunk(s64 offset)
 116 {
 117         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
 118                 return offset;
 119         else
 120                 return shift_right(offset, SHIFT_PLL + time_constant);
 121 }
 122
 123 static inline void pps_reset_freq_interval(void)
 124 {
 125         /* the PPS calibration interval may end
 126            surprisingly early */
 127         pps_shift = PPS_INTMIN;
 128         pps_intcnt = 0;
 129 }
 130
 131 /**
 132  * pps_clear - Clears the PPS state variables
 133  *
 134  * Must be called while holding a write on the xtime_lock
 135  */
 136 static inline void pps_clear(void)
 137 {
 138         pps_reset_freq_interval();
 139         pps_tf[0] = 0;
 140         pps_tf[1] = 0;
 141         pps_tf[2] = 0;
 142         pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
 143         pps_freq = 0;
 144 }
 145
 146 /* Decrease pps_valid to indicate that another second has passed since
 147  * the last PPS signal. When it reaches 0, indicate that PPS signal is
 148  * missing.
 149  *
 150  * Must be called while holding a write on the xtime_lock
 151  */
 152 static inline void pps_dec_valid(void)
 153 {
 154         if (pps_valid > 0)
 155                 pps_valid--;
 156         else {
 157                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 158                                  STA_PPSWANDER | STA_PPSERROR);
 159                 pps_clear();
 160         }
 161 }
 162
 163 static inline void pps_set_freq(s64 freq)
 164 {
 165         pps_freq = freq;
 166 }
 167
 168 static inline int is_error_status(int status)
 169 {
 170         return (time_status & (STA_UNSYNC|STA_CLOCKERR))
 171                 /* PPS signal lost when either PPS time or
 172                  * PPS frequency synchronization requested
 173                  */
 174                 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
 175                         && !(time_status & STA_PPSSIGNAL))
 176                 /* PPS jitter exceeded when
 177                  * PPS time synchronization requested */
 178                 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
 179                         == (STA_PPSTIME|STA_PPSJITTER))
 180                 /* PPS wander exceeded or calibration error when
 181                  * PPS frequency synchronization requested
 182                  */
 183                 || ((time_status & STA_PPSFREQ)
 184                         && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
 185 }
 186
 187 static inline void pps_fill_timex(struct timex *txc)
 188 {
 189         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 190                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 191         txc->jitter        = pps_jitter;
 192         if (!(time_status & STA_NANO))
 193                 txc->jitter /= NSEC_PER_USEC;
 194         txc->shift         = pps_shift;
 195         txc->stabil        = pps_stabil;
 196         txc->jitcnt        = pps_jitcnt;
 197         txc->calcnt        = pps_calcnt;
 198         txc->errcnt        = pps_errcnt;
 199         txc->stbcnt        = pps_stbcnt;
 200 }
 201
 202 #else /* !CONFIG_NTP_PPS */
 203
 204 static inline s64 ntp_offset_chunk(s64 offset)
 205 {
 206         return shift_right(offset, SHIFT_PLL + time_constant);
 207 }
 208
 209 static inline void pps_reset_freq_interval(void) {}
 210 static inline void pps_clear(void) {}
 211 static inline void pps_dec_valid(void) {}
 212 static inline void pps_set_freq(s64 freq) {}
 213
 214 static inline int is_error_status(int status)
 215 {
 216         return status & (STA_UNSYNC|STA_CLOCKERR);
 217 }
 218
 219 static inline void pps_fill_timex(struct timex *txc)
 220 {
 221         /* PPS is not implemented, so these are zero */
 222         txc->ppsfreq       = 0;
 223         txc->jitter        = 0;
 224         txc->shift         = 0;
 225         txc->stabil        = 0;
 226         txc->jitcnt        = 0;
 227         txc->calcnt        = 0;
 228         txc->errcnt        = 0;
 229         txc->stbcnt        = 0;
 230 }
 231
 232 #endif /* CONFIG_NTP_PPS */
 233
 234 /*
 235  * NTP methods:
 236  */
 237
 238 /*
 239  * Update (tick_length, tick_length_base, tick_nsec), based
 240  * on (tick_usec, ntp_tick_adj, time_freq):
 241  */
 242 static void ntp_update_frequency(void)
 243 {
 244         u64 second_length;
 245         u64 new_base;
 246
 247         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 248                                                 << NTP_SCALE_SHIFT;
 249
 250         second_length           += ntp_tick_adj;
 251         second_length           += time_freq;
 252
 253         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 254         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 255
 256         /*
 257          * Don't wait for the next second_overflow, apply
 258          * the change to the tick length immediately:
 259          */
 260         tick_length             += new_base - tick_length_base;
 261         tick_length_base         = new_base;
 262 }
 263
 264 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 265 {
 266         time_status &= ~STA_MODE;
 267
 268         if (secs < MINSEC)
 269                 return 0;
 270
 271         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 272                 return 0;
 273
 274         time_status |= STA_MODE;
 275
 276         return div_s64(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 277 }
 278
 279 static void ntp_update_offset(long offset)
 280 {
 281         s64 freq_adj;
 282         s64 offset64;
 283         long secs;
 284
 285         if (!(time_status & STA_PLL))
 286                 return;
 287
 288         if (!(time_status & STA_NANO))
 289                 offset *= NSEC_PER_USEC;
 290
 291         /*
 292          * Scale the phase adjustment and
 293          * clamp to the operating range.
 294          */
 295         offset = min(offset, MAXPHASE);
 296         offset = max(offset, -MAXPHASE);
 297
 298         /*
 299          * Select how the frequency is to be controlled
 300          * and in which mode (PLL or FLL).
 301          */
 302         secs = get_seconds() - time_reftime;
 303         if (unlikely(time_status & STA_FREQHOLD))
 304                 secs = 0;
 305
 306         time_reftime = get_seconds();
 307
 308         offset64    = offset;
 309         freq_adj    = ntp_update_offset_fll(offset64, secs);
 310
 311         /*
 312          * Clamp update interval to reduce PLL gain with low
 313          * sampling rate (e.g. intermittent network connection)
 314          * to avoid instability.
 315          */
 316         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 317                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
 318
 319         freq_adj    += (offset64 * secs) <<
 320                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 321
 322         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 323
 324         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 325
 326         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 327 }
 328
 329 /**
 330  * ntp_clear - Clears the NTP state variables
 331  *
 332  * Must be called while holding a write on the xtime_lock
 333  */
 334 void ntp_clear(void)
 335 {
 336         time_adjust     = 0;            /* stop active adjtime() */
 337         time_status     |= STA_UNSYNC;
 338         time_maxerror   = NTP_PHASE_LIMIT;
 339         time_esterror   = NTP_PHASE_LIMIT;
 340
 341         ntp_update_frequency();
 342
 343         tick_length     = tick_length_base;
 344         time_offset     = 0;
 345
 346         /* Clear PPS state variables */
 347         pps_clear();
 348 }
 349
 350 /*
 351  * Leap second processing. If in leap-insert state at the end of the
 352  * day, the system clock is set back one second; if in leap-delete
 353  * state, the system clock is set ahead one second.
 354  */
 355 static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
 356 {
 357         enum hrtimer_restart res = HRTIMER_NORESTART;
 358
 359         write_seqlock(&xtime_lock);
 360
 361         switch (time_state) {
 362         case TIME_OK:
 363                 break;
 364         case TIME_INS:
 365                 timekeeping_leap_insert(-1);
 366                 time_state = TIME_OOP;
 367                 printk(KERN_NOTICE
 368                         "Clock: inserting leap second 23:59:60 UTC\n");
 369                 hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
 370                 res = HRTIMER_RESTART;
 371                 break;
 372         case TIME_DEL:
 373                 timekeeping_leap_insert(1);
 374                 time_tai--;
 375                 time_state = TIME_WAIT;
 376                 printk(KERN_NOTICE
 377                         "Clock: deleting leap second 23:59:59 UTC\n");
 378                 break;
 379         case TIME_OOP:
 380                 time_tai++;
 381                 time_state = TIME_WAIT;
 382                 /* fall through */
 383         case TIME_WAIT:
 384                 if (!(time_status & (STA_INS | STA_DEL)))
 385                         time_state = TIME_OK;
 386                 break;
 387         }
 388
 389         write_sequnlock(&xtime_lock);
 390
 391         return res;
 392 }
 393
 394 /*
 395  * this routine handles the overflow of the microsecond field
 396  *
 397  * The tricky bits of code to handle the accurate clock support
 398  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 399  * They were originally developed for SUN and DEC kernels.
 400  * All the kudos should go to Dave for this stuff.
 401  */
 402 void second_overflow(void)
 403 {
 404         s64 delta;
 405
 406         /* Bump the maxerror field */
 407         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 408         if (time_maxerror > NTP_PHASE_LIMIT) {
 409                 time_maxerror = NTP_PHASE_LIMIT;
 410                 time_status |= STA_UNSYNC;
 411         }
 412
 413         /* Compute the phase adjustment for the next second */
 414         tick_length      = tick_length_base;
 415
 416         delta            = ntp_offset_chunk(time_offset);
 417         time_offset     -= delta;
 418         tick_length     += delta;
 419
 420         /* Check PPS signal */
 421         pps_dec_valid();
 422
 423         if (!time_adjust)
 424                 return;
 425
 426         if (time_adjust > MAX_TICKADJ) {
 427                 time_adjust -= MAX_TICKADJ;
 428                 tick_length += MAX_TICKADJ_SCALED;
 429                 return;
 430         }
 431
 432         if (time_adjust < -MAX_TICKADJ) {
 433                 time_adjust += MAX_TICKADJ;
 434                 tick_length -= MAX_TICKADJ_SCALED;
 435                 return;
 436         }
 437
 438         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 439                                                          << NTP_SCALE_SHIFT;
 440         time_adjust = 0;
 441 }
 442
 443 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 444
 445 /* Disable the cmos update - used by virtualization and embedded */
 446 int no_sync_cmos_clock  __read_mostly;
 447
 448 static void sync_cmos_clock(struct work_struct *work);
 449
 450 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
 451
 452 static void sync_cmos_clock(struct work_struct *work)
 453 {
 454         struct timespec now, next;
 455         int fail = 1;
 456
 457         /*
 458          * If we have an externally synchronized Linux clock, then update
 459          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
 460          * called as close as possible to 500 ms before the new second starts.
 461          * This code is run on a timer.  If the clock is set, that timer
 462          * may not expire at the correct time.  Thus, we adjust...
 463          */
 464         if (!ntp_synced()) {
 465                 /*
 466                  * Not synced, exit, do not restart a timer (if one is
 467                  * running, let it run out).
 468                  */
 469                 return;
 470         }
 471
 472         getnstimeofday(&now);
 473         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
 474                 fail = update_persistent_clock(now);
 475
 476         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 477         if (next.tv_nsec <= 0)
 478                 next.tv_nsec += NSEC_PER_SEC;
 479
 480         if (!fail)
 481                 next.tv_sec = 659;
 482         else
 483                 next.tv_sec = 0;
 484
 485         if (next.tv_nsec >= NSEC_PER_SEC) {
 486                 next.tv_sec++;
 487                 next.tv_nsec -= NSEC_PER_SEC;
 488         }
 489         schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
 490 }
 491
 492 static void notify_cmos_timer(void)
 493 {
 494         if (!no_sync_cmos_clock)
 495                 schedule_delayed_work(&sync_cmos_work, 0);
 496 }
 497
 498 #else
 499 static inline void notify_cmos_timer(void) { }
 500 #endif
 501
 502 /*
 503  * Start the leap seconds timer:
 504  */
 505 static inline void ntp_start_leap_timer(struct timespec *ts)
 506 {
 507         long now = ts->tv_sec;
 508
 509         if (time_status & STA_INS) {
 510                 time_state = TIME_INS;
 511                 now += 86400 - now % 86400;
 512                 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
 513
 514                 return;
 515         }
 516
 517         if (time_status & STA_DEL) {
 518                 time_state = TIME_DEL;
 519                 now += 86400 - (now + 1) % 86400;
 520                 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
 521         }
 522 }
 523
 524 /*
 525  * Propagate a new txc->status value into the NTP state:
 526  */
 527 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
 528 {
 529         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 530                 time_state = TIME_OK;
 531                 time_status = STA_UNSYNC;
 532                 /* restart PPS frequency calibration */
 533                 pps_reset_freq_interval();
 534         }
 535
 536         /*
 537          * If we turn on PLL adjustments then reset the
 538          * reference time to current time.
 539          */
 540         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 541                 time_reftime = get_seconds();
 542
 543         /* only set allowed bits */
 544         time_status &= STA_RONLY;
 545         time_status |= txc->status & ~STA_RONLY;
 546
 547         switch (time_state) {
 548         case TIME_OK:
 549                 ntp_start_leap_timer(ts);
 550                 break;
 551         case TIME_INS:
 552         case TIME_DEL:
 553                 time_state = TIME_OK;
 554                 ntp_start_leap_timer(ts);
 555         case TIME_WAIT:
 556                 if (!(time_status & (STA_INS | STA_DEL)))
 557                         time_state = TIME_OK;
 558                 break;
 559         case TIME_OOP:
 560                 hrtimer_restart(&leap_timer);
 561                 break;
 562         }
 563 }
 564 /*
 565  * Called with the xtime lock held, so we can access and modify
 566  * all the global NTP state:
 567  */
 568 static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
 569 {
 570         if (txc->modes & ADJ_STATUS)
 571                 process_adj_status(txc, ts);
 572
 573         if (txc->modes & ADJ_NANO)
 574                 time_status |= STA_NANO;
 575
 576         if (txc->modes & ADJ_MICRO)
 577                 time_status &= ~STA_NANO;
 578
 579         if (txc->modes & ADJ_FREQUENCY) {
 580                 time_freq = txc->freq * PPM_SCALE;
 581                 time_freq = min(time_freq, MAXFREQ_SCALED);
 582                 time_freq = max(time_freq, -MAXFREQ_SCALED);
 583                 /* update pps_freq */
 584                 pps_set_freq(time_freq);
 585         }
 586
 587         if (txc->modes & ADJ_MAXERROR)
 588                 time_maxerror = txc->maxerror;
 589
 590         if (txc->modes & ADJ_ESTERROR)
 591                 time_esterror = txc->esterror;
 592
 593         if (txc->modes & ADJ_TIMECONST) {
 594                 time_constant = txc->constant;
 595                 if (!(time_status & STA_NANO))
 596                         time_constant += 4;
 597                 time_constant = min(time_constant, (long)MAXTC);
 598                 time_constant = max(time_constant, 0l);
 599         }
 600
 601         if (txc->modes & ADJ_TAI && txc->constant > 0)
 602                 time_tai = txc->constant;
 603
 604         if (txc->modes & ADJ_OFFSET)
 605                 ntp_update_offset(txc->offset);
 606
 607         if (txc->modes & ADJ_TICK)
 608                 tick_usec = txc->tick;
 609
 610         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 611                 ntp_update_frequency();
 612 }
 613
 614 /*
 615  * adjtimex mainly allows reading (and writing, if superuser) of
 616  * kernel time-keeping variables. used by xntpd.
 617  */
 618 int do_adjtimex(struct timex *txc)
 619 {
 620         struct timespec ts;
 621         int result;
 622
 623         /* Validate the data before disabling interrupts */
 624         if (txc->modes & ADJ_ADJTIME) {
 625                 /* singleshot must not be used with any other mode bits */
 626                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
 627                         return -EINVAL;
 628                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
 629                     !capable(CAP_SYS_TIME))
 630                         return -EPERM;
 631         } else {
 632                 /* In order to modify anything, you gotta be super-user! */
 633                  if (txc->modes && !capable(CAP_SYS_TIME))
 634                         return -EPERM;
 635
 636                 /*
 637                  * if the quartz is off by more than 10% then
 638                  * something is VERY wrong!
 639                  */
 640                 if (txc->modes & ADJ_TICK &&
 641                     (txc->tick <  900000/USER_HZ ||
 642                      txc->tick > 1100000/USER_HZ))
 643                         return -EINVAL;
 644
 645                 if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
 646                         hrtimer_cancel(&leap_timer);
 647         }
 648
 649         getnstimeofday(&ts);
 650
 651         write_seqlock_irq(&xtime_lock);
 652
 653         if (txc->modes & ADJ_ADJTIME) {
 654                 long save_adjust = time_adjust;
 655
 656                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 657                         /* adjtime() is independent from ntp_adjtime() */
 658                         time_adjust = txc->offset;
 659                         ntp_update_frequency();
 660                 }
 661                 txc->offset = save_adjust;
 662         } else {
 663
 664                 /* If there are input parameters, then process them: */
 665                 if (txc->modes)
 666                         process_adjtimex_modes(txc, &ts);
 667
 668                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 669                                   NTP_SCALE_SHIFT);
 670                 if (!(time_status & STA_NANO))
 671                         txc->offset /= NSEC_PER_USEC;
 672         }
 673
 674         result = time_state;    /* mostly `TIME_OK' */
 675         /* check for errors */
 676         if (is_error_status(time_status))
 677                 result = TIME_ERROR;
 678
 679         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 680                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 681         txc->maxerror      = time_maxerror;
 682         txc->esterror      = time_esterror;
 683         txc->status        = time_status;
 684         txc->constant      = time_constant;
 685         txc->precision     = 1;
 686         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 687         txc->tick          = tick_usec;
 688         txc->tai           = time_tai;
 689
 690         /* fill PPS status fields */
 691         pps_fill_timex(txc);
 692
 693         write_sequnlock_irq(&xtime_lock);
 694
 695         txc->time.tv_sec = ts.tv_sec;
 696         txc->time.tv_usec = ts.tv_nsec;
 697         if (!(time_status & STA_NANO))
 698                 txc->time.tv_usec /= NSEC_PER_USEC;
 699
 700         notify_cmos_timer();
 701
 702         return result;
 703 }
 704
 705 #ifdef  CONFIG_NTP_PPS
 706
 707 /* actually struct pps_normtime is good old struct timespec, but it is
 708  * semantically different (and it is the reason why it was invented):
 709  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 710  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 711 struct pps_normtime {
 712         __kernel_time_t sec;    /* seconds */
 713         long            nsec;   /* nanoseconds */
 714 };
 715
 716 /* normalize the timestamp so that nsec is in the
 717    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 718 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
 719 {
 720         struct pps_normtime norm = {
 721                 .sec = ts.tv_sec,
 722                 .nsec = ts.tv_nsec
 723         };
 724
 725         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 726                 norm.nsec -= NSEC_PER_SEC;
 727                 norm.sec++;
 728         }
 729
 730         return norm;
 731 }
 732
 733 /* get current phase correction and jitter */
 734 static inline long pps_phase_filter_get(long *jitter)
 735 {
 736         *jitter = pps_tf[0] - pps_tf[1];
 737         if (*jitter < 0)
 738                 *jitter = -*jitter;
 739
 740         /* TODO: test various filters */
 741         return pps_tf[0];
 742 }
 743
 744 /* add the sample to the phase filter */
 745 static inline void pps_phase_filter_add(long err)
 746 {
 747         pps_tf[2] = pps_tf[1];
 748         pps_tf[1] = pps_tf[0];
 749         pps_tf[0] = err;
 750 }
 751
 752 /* decrease frequency calibration interval length.
 753  * It is halved after four consecutive unstable intervals.
 754  */
 755 static inline void pps_dec_freq_interval(void)
 756 {
 757         if (--pps_intcnt <= -PPS_INTCOUNT) {
 758                 pps_intcnt = -PPS_INTCOUNT;
 759                 if (pps_shift > PPS_INTMIN) {
 760                         pps_shift--;
 761                         pps_intcnt = 0;
 762                 }
 763         }
 764 }
 765
 766 /* increase frequency calibration interval length.
 767  * It is doubled after four consecutive stable intervals.
 768  */
 769 static inline void pps_inc_freq_interval(void)
 770 {
 771         if (++pps_intcnt >= PPS_INTCOUNT) {
 772                 pps_intcnt = PPS_INTCOUNT;
 773                 if (pps_shift < PPS_INTMAX) {
 774                         pps_shift++;
 775                         pps_intcnt = 0;
 776                 }
 777         }
 778 }
 779
 780 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 781  * timestamps
 782  *
 783  * At the end of the calibration interval the difference between the
 784  * first and last MONOTONIC_RAW clock timestamps divided by the length
 785  * of the interval becomes the frequency update. If the interval was
 786  * too long, the data are discarded.
 787  * Returns the difference between old and new frequency values.
 788  */
 789 static long hardpps_update_freq(struct pps_normtime freq_norm)
 790 {
 791         long delta, delta_mod;
 792         s64 ftemp;
 793
 794         /* check if the frequency interval was too long */
 795         if (freq_norm.sec > (2 << pps_shift)) {
 796                 time_status |= STA_PPSERROR;
 797                 pps_errcnt++;
 798                 pps_dec_freq_interval();
 799                 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
 800                                 freq_norm.sec);
 801                 return 0;
 802         }
 803
 804         /* here the raw frequency offset and wander (stability) is
 805          * calculated. If the wander is less than the wander threshold
 806          * the interval is increased; otherwise it is decreased.
 807          */
 808         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 809                         freq_norm.sec);
 810         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 811         pps_freq = ftemp;
 812         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 813                 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
 814                 time_status |= STA_PPSWANDER;
 815                 pps_stbcnt++;
 816                 pps_dec_freq_interval();
 817         } else {        /* good sample */
 818                 pps_inc_freq_interval();
 819         }
 820
 821         /* the stability metric is calculated as the average of recent
 822          * frequency changes, but is used only for performance
 823          * monitoring
 824          */
 825         delta_mod = delta;
 826         if (delta_mod < 0)
 827                 delta_mod = -delta_mod;
 828         pps_stabil += (div_s64(((s64)delta_mod) <<
 829                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 830                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 831
 832         /* if enabled, the system clock frequency is updated */
 833         if ((time_status & STA_PPSFREQ) != 0 &&
 834             (time_status & STA_FREQHOLD) == 0) {
 835                 time_freq = pps_freq;
 836                 ntp_update_frequency();
 837         }
 838
 839         return delta;
 840 }
 841
 842 /* correct REALTIME clock phase error against PPS signal */
 843 static void hardpps_update_phase(long error)
 844 {
 845         long correction = -error;
 846         long jitter;
 847
 848         /* add the sample to the median filter */
 849         pps_phase_filter_add(correction);
 850         correction = pps_phase_filter_get(&jitter);
 851
 852         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 853          * threshold, the sample is discarded; otherwise, if so enabled,
 854          * the time offset is updated.
 855          */
 856         if (jitter > (pps_jitter << PPS_POPCORN)) {
 857                 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 858                        jitter, (pps_jitter << PPS_POPCORN));
 859                 time_status |= STA_PPSJITTER;
 860                 pps_jitcnt++;
 861         } else if (time_status & STA_PPSTIME) {
 862                 /* correct the time using the phase offset */
 863                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 864                                 NTP_INTERVAL_FREQ);
 865                 /* cancel running adjtime() */
 866                 time_adjust = 0;
 867         }
 868         /* update jitter */
 869         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 870 }
 871
 872 /*
 873  * hardpps() - discipline CPU clock oscillator to external PPS signal
 874  *
 875  * This routine is called at each PPS signal arrival in order to
 876  * discipline the CPU clock oscillator to the PPS signal. It takes two
 877  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 878  * is used to correct clock phase error and the latter is used to
 879  * correct the frequency.
 880  *
 881  * This code is based on David Mills's reference nanokernel
 882  * implementation. It was mostly rewritten but keeps the same idea.
 883  */
 884 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 885 {
 886         struct pps_normtime pts_norm, freq_norm;
 887         unsigned long flags;
 888
 889         pts_norm = pps_normalize_ts(*phase_ts);
 890
 891         write_seqlock_irqsave(&xtime_lock, flags);
 892
 893         /* clear the error bits, they will be set again if needed */
 894         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 895
 896         /* indicate signal presence */
 897         time_status |= STA_PPSSIGNAL;
 898         pps_valid = PPS_VALID;
 899
 900         /* when called for the first time,
 901          * just start the frequency interval */
 902         if (unlikely(pps_fbase.tv_sec == 0)) {
 903                 pps_fbase = *raw_ts;
 904                 write_sequnlock_irqrestore(&xtime_lock, flags);
 905                 return;
 906         }
 907
 908         /* ok, now we have a base for frequency calculation */
 909         freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
 910
 911         /* check that the signal is in the range
 912          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 913         if ((freq_norm.sec == 0) ||
 914                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 915                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 916                 time_status |= STA_PPSJITTER;
 917                 /* restart the frequency calibration interval */
 918                 pps_fbase = *raw_ts;
 919                 write_sequnlock_irqrestore(&xtime_lock, flags);
 920                 pr_err("hardpps: PPSJITTER: bad pulse\n");
 921                 return;
 922         }
 923
 924         /* signal is ok */
 925
 926         /* check if the current frequency interval is finished */
 927         if (freq_norm.sec >= (1 << pps_shift)) {
 928                 pps_calcnt++;
 929                 /* restart the frequency calibration interval */
 930                 pps_fbase = *raw_ts;
 931                 hardpps_update_freq(freq_norm);
 932         }
 933
 934         hardpps_update_phase(pts_norm.nsec);
 935
 936         write_sequnlock_irqrestore(&xtime_lock, flags);
 937 }
 938 EXPORT_SYMBOL(hardpps);
 939
 940 #endif  /* CONFIG_NTP_PPS */
 941
 942 static int __init ntp_tick_adj_setup(char *str)
 943 {
 944         ntp_tick_adj = simple_strtol(str, NULL, 0);
 945         ntp_tick_adj <<= NTP_SCALE_SHIFT;
 946
 947         return 1;
 948 }
 949
 950 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
 951
 952 void __init ntp_init(void)
 953 {
 954         ntp_clear();
 955         hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
 956         leap_timer.function = ntp_leap_second;
 957 }