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 #include "tick-internal.h"
  20
  21 /*
  22  * NTP timekeeping variables:
  23  */
  24
  25 DEFINE_SPINLOCK(ntp_lock);
  26
  27
  28 /* USER_HZ period (usecs): */
  29 unsigned long                   tick_usec = TICK_USEC;
  30
  31 /* ACTHZ period (nsecs): */
  32 unsigned long                   tick_nsec;
  33
  34 static u64                      tick_length;
  35 static u64                      tick_length_base;
  36
  37 #define MAX_TICKADJ             500LL           /* usecs */
  38 #define MAX_TICKADJ_SCALED \
  39         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  40
  41 /*
  42  * phase-lock loop variables
  43  */
  44
  45 /*
  46  * clock synchronization status
  47  *
  48  * (TIME_ERROR prevents overwriting the CMOS clock)
  49  */
  50 static int                      time_state = TIME_OK;
  51
  52 /* clock status bits:                                                   */
  53 static int                      time_status = STA_UNSYNC;
  54
  55 /* TAI offset (secs):                                                   */
  56 static long                     time_tai;
  57
  58 /* time adjustment (nsecs):                                             */
  59 static s64                      time_offset;
  60
  61 /* pll time constant:                                                   */
  62 static long                     time_constant = 2;
  63
  64 /* maximum error (usecs):                                               */
  65 static long                     time_maxerror = NTP_PHASE_LIMIT;
  66
  67 /* estimated error (usecs):                                             */
  68 static long                     time_esterror = NTP_PHASE_LIMIT;
  69
  70 /* frequency offset (scaled nsecs/secs):                                */
  71 static s64                      time_freq;
  72
  73 /* time at last adjustment (secs):                                      */
  74 static long                     time_reftime;
  75
  76 static long                     time_adjust;
  77
  78 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
  79 static s64                      ntp_tick_adj;
  80
  81 #ifdef CONFIG_NTP_PPS
  82
  83 /*
  84  * The following variables are used when a pulse-per-second (PPS) signal
  85  * is available. They establish the engineering parameters of the clock
  86  * discipline loop when controlled by the PPS signal.
  87  */
  88 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
  89 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
  90 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
  91 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
  92 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
  93                                    increase pps_shift or consecutive bad
  94                                    intervals to decrease it */
  95 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
  96
  97 static int pps_valid;           /* signal watchdog counter */
  98 static long pps_tf[3];          /* phase median filter */
  99 static long pps_jitter;         /* current jitter (ns) */
 100 static struct timespec pps_fbase; /* beginning of the last freq interval */
 101 static int pps_shift;           /* current interval duration (s) (shift) */
 102 static int pps_intcnt;          /* interval counter */
 103 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
 104 static long pps_stabil;         /* current stability (scaled ns/s) */
 105
 106 /*
 107  * PPS signal quality monitors
 108  */
 109 static long pps_calcnt;         /* calibration intervals */
 110 static long pps_jitcnt;         /* jitter limit exceeded */
 111 static long pps_stbcnt;         /* stability limit exceeded */
 112 static long pps_errcnt;         /* calibration errors */
 113
 114
 115 /* PPS kernel consumer compensates the whole phase error immediately.
 116  * Otherwise, reduce the offset by a fixed factor times the time constant.
 117  */
 118 static inline s64 ntp_offset_chunk(s64 offset)
 119 {
 120         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
 121                 return offset;
 122         else
 123                 return shift_right(offset, SHIFT_PLL + time_constant);
 124 }
 125
 126 static inline void pps_reset_freq_interval(void)
 127 {
 128         /* the PPS calibration interval may end
 129            surprisingly early */
 130         pps_shift = PPS_INTMIN;
 131         pps_intcnt = 0;
 132 }
 133
 134 /**
 135  * pps_clear - Clears the PPS state variables
 136  *
 137  * Must be called while holding a write on the ntp_lock
 138  */
 139 static inline void pps_clear(void)
 140 {
 141         pps_reset_freq_interval();
 142         pps_tf[0] = 0;
 143         pps_tf[1] = 0;
 144         pps_tf[2] = 0;
 145         pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
 146         pps_freq = 0;
 147 }
 148
 149 /* Decrease pps_valid to indicate that another second has passed since
 150  * the last PPS signal. When it reaches 0, indicate that PPS signal is
 151  * missing.
 152  *
 153  * Must be called while holding a write on the ntp_lock
 154  */
 155 static inline void pps_dec_valid(void)
 156 {
 157         if (pps_valid > 0)
 158                 pps_valid--;
 159         else {
 160                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 161                                  STA_PPSWANDER | STA_PPSERROR);
 162                 pps_clear();
 163         }
 164 }
 165
 166 static inline void pps_set_freq(s64 freq)
 167 {
 168         pps_freq = freq;
 169 }
 170
 171 static inline int is_error_status(int status)
 172 {
 173         return (time_status & (STA_UNSYNC|STA_CLOCKERR))
 174                 /* PPS signal lost when either PPS time or
 175                  * PPS frequency synchronization requested
 176                  */
 177                 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
 178                         && !(time_status & STA_PPSSIGNAL))
 179                 /* PPS jitter exceeded when
 180                  * PPS time synchronization requested */
 181                 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
 182                         == (STA_PPSTIME|STA_PPSJITTER))
 183                 /* PPS wander exceeded or calibration error when
 184                  * PPS frequency synchronization requested
 185                  */
 186                 || ((time_status & STA_PPSFREQ)
 187                         && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
 188 }
 189
 190 static inline void pps_fill_timex(struct timex *txc)
 191 {
 192         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 193                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 194         txc->jitter        = pps_jitter;
 195         if (!(time_status & STA_NANO))
 196                 txc->jitter /= NSEC_PER_USEC;
 197         txc->shift         = pps_shift;
 198         txc->stabil        = pps_stabil;
 199         txc->jitcnt        = pps_jitcnt;
 200         txc->calcnt        = pps_calcnt;
 201         txc->errcnt        = pps_errcnt;
 202         txc->stbcnt        = pps_stbcnt;
 203 }
 204
 205 #else /* !CONFIG_NTP_PPS */
 206
 207 static inline s64 ntp_offset_chunk(s64 offset)
 208 {
 209         return shift_right(offset, SHIFT_PLL + time_constant);
 210 }
 211
 212 static inline void pps_reset_freq_interval(void) {}
 213 static inline void pps_clear(void) {}
 214 static inline void pps_dec_valid(void) {}
 215 static inline void pps_set_freq(s64 freq) {}
 216
 217 static inline int is_error_status(int status)
 218 {
 219         return status & (STA_UNSYNC|STA_CLOCKERR);
 220 }
 221
 222 static inline void pps_fill_timex(struct timex *txc)
 223 {
 224         /* PPS is not implemented, so these are zero */
 225         txc->ppsfreq       = 0;
 226         txc->jitter        = 0;
 227         txc->shift         = 0;
 228         txc->stabil        = 0;
 229         txc->jitcnt        = 0;
 230         txc->calcnt        = 0;
 231         txc->errcnt        = 0;
 232         txc->stbcnt        = 0;
 233 }
 234
 235 #endif /* CONFIG_NTP_PPS */
 236
 237
 238 /**
 239  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 240  *
 241  */
 242 static inline int ntp_synced(void)
 243 {
 244         return !(time_status & STA_UNSYNC);
 245 }
 246
 247
 248 /*
 249  * NTP methods:
 250  */
 251
 252 /*
 253  * Update (tick_length, tick_length_base, tick_nsec), based
 254  * on (tick_usec, ntp_tick_adj, time_freq):
 255  */
 256 static void ntp_update_frequency(void)
 257 {
 258         u64 second_length;
 259         u64 new_base;
 260
 261         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 262                                                 << NTP_SCALE_SHIFT;
 263
 264         second_length           += ntp_tick_adj;
 265         second_length           += time_freq;
 266
 267         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 268         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 269
 270         /*
 271          * Don't wait for the next second_overflow, apply
 272          * the change to the tick length immediately:
 273          */
 274         tick_length             += new_base - tick_length_base;
 275         tick_length_base         = new_base;
 276 }
 277
 278 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 279 {
 280         time_status &= ~STA_MODE;
 281
 282         if (secs < MINSEC)
 283                 return 0;
 284
 285         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 286                 return 0;
 287
 288         time_status |= STA_MODE;
 289
 290         return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 291 }
 292
 293 static void ntp_update_offset(long offset)
 294 {
 295         s64 freq_adj;
 296         s64 offset64;
 297         long secs;
 298
 299         if (!(time_status & STA_PLL))
 300                 return;
 301
 302         if (!(time_status & STA_NANO))
 303                 offset *= NSEC_PER_USEC;
 304
 305         /*
 306          * Scale the phase adjustment and
 307          * clamp to the operating range.
 308          */
 309         offset = min(offset, MAXPHASE);
 310         offset = max(offset, -MAXPHASE);
 311
 312         /*
 313          * Select how the frequency is to be controlled
 314          * and in which mode (PLL or FLL).
 315          */
 316         secs = get_seconds() - time_reftime;
 317         if (unlikely(time_status & STA_FREQHOLD))
 318                 secs = 0;
 319
 320         time_reftime = get_seconds();
 321
 322         offset64    = offset;
 323         freq_adj    = ntp_update_offset_fll(offset64, secs);
 324
 325         /*
 326          * Clamp update interval to reduce PLL gain with low
 327          * sampling rate (e.g. intermittent network connection)
 328          * to avoid instability.
 329          */
 330         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 331                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
 332
 333         freq_adj    += (offset64 * secs) <<
 334                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 335
 336         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 337
 338         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 339
 340         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 341 }
 342
 343 /**
 344  * ntp_clear - Clears the NTP state variables
 345  */
 346 void ntp_clear(void)
 347 {
 348         unsigned long flags;
 349
 350         spin_lock_irqsave(&ntp_lock, flags);
 351
 352         time_adjust     = 0;            /* stop active adjtime() */
 353         time_status     |= STA_UNSYNC;
 354         time_maxerror   = NTP_PHASE_LIMIT;
 355         time_esterror   = NTP_PHASE_LIMIT;
 356
 357         ntp_update_frequency();
 358
 359         tick_length     = tick_length_base;
 360         time_offset     = 0;
 361
 362         /* Clear PPS state variables */
 363         pps_clear();
 364         spin_unlock_irqrestore(&ntp_lock, flags);
 365
 366 }
 367
 368
 369 u64 ntp_tick_length(void)
 370 {
 371         unsigned long flags;
 372         s64 ret;
 373
 374         spin_lock_irqsave(&ntp_lock, flags);
 375         ret = tick_length;
 376         spin_unlock_irqrestore(&ntp_lock, flags);
 377         return ret;
 378 }
 379
 380
 381 /*
 382  * this routine handles the overflow of the microsecond field
 383  *
 384  * The tricky bits of code to handle the accurate clock support
 385  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 386  * They were originally developed for SUN and DEC kernels.
 387  * All the kudos should go to Dave for this stuff.
 388  *
 389  * Also handles leap second processing, and returns leap offset
 390  */
 391 int second_overflow(unsigned long secs)
 392 {
 393         s64 delta;
 394         int leap = 0;
 395         unsigned long flags;
 396
 397         spin_lock_irqsave(&ntp_lock, flags);
 398
 399         /*
 400          * Leap second processing. If in leap-insert state at the end of the
 401          * day, the system clock is set back one second; if in leap-delete
 402          * state, the system clock is set ahead one second.
 403          */
 404         switch (time_state) {
 405         case TIME_OK:
 406                 if (time_status & STA_INS)
 407                         time_state = TIME_INS;
 408                 else if (time_status & STA_DEL)
 409                         time_state = TIME_DEL;
 410                 break;
 411         case TIME_INS:
 412                 if (secs % 86400 == 0) {
 413                         leap = -1;
 414                         time_state = TIME_OOP;
 415                         printk(KERN_NOTICE
 416                                 "Clock: inserting leap second 23:59:60 UTC\n");
 417                 }
 418                 break;
 419         case TIME_DEL:
 420                 if ((secs + 1) % 86400 == 0) {
 421                         leap = 1;
 422                         time_tai--;
 423                         time_state = TIME_WAIT;
 424                         printk(KERN_NOTICE
 425                                 "Clock: deleting leap second 23:59:59 UTC\n");
 426                 }
 427                 break;
 428         case TIME_OOP:
 429                 time_tai++;
 430                 time_state = TIME_WAIT;
 431                 break;
 432
 433         case TIME_WAIT:
 434                 if (!(time_status & (STA_INS | STA_DEL)))
 435                         time_state = TIME_OK;
 436                 break;
 437         }
 438
 439
 440         /* Bump the maxerror field */
 441         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 442         if (time_maxerror > NTP_PHASE_LIMIT) {
 443                 time_maxerror = NTP_PHASE_LIMIT;
 444                 time_status |= STA_UNSYNC;
 445         }
 446
 447         /* Compute the phase adjustment for the next second */
 448         tick_length      = tick_length_base;
 449
 450         delta            = ntp_offset_chunk(time_offset);
 451         time_offset     -= delta;
 452         tick_length     += delta;
 453
 454         /* Check PPS signal */
 455         pps_dec_valid();
 456
 457         if (!time_adjust)
 458                 goto out;
 459
 460         if (time_adjust > MAX_TICKADJ) {
 461                 time_adjust -= MAX_TICKADJ;
 462                 tick_length += MAX_TICKADJ_SCALED;
 463                 goto out;
 464         }
 465
 466         if (time_adjust < -MAX_TICKADJ) {
 467                 time_adjust += MAX_TICKADJ;
 468                 tick_length -= MAX_TICKADJ_SCALED;
 469                 goto out;
 470         }
 471
 472         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 473                                                          << NTP_SCALE_SHIFT;
 474         time_adjust = 0;
 475
 476
 477
 478 out:
 479         spin_unlock_irqrestore(&ntp_lock, flags);
 480
 481         return leap;
 482 }
 483
 484 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 485
 486 static void sync_cmos_clock(struct work_struct *work);
 487
 488 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
 489
 490 static void sync_cmos_clock(struct work_struct *work)
 491 {
 492         struct timespec now, next;
 493         int fail = 1;
 494
 495         /*
 496          * If we have an externally synchronized Linux clock, then update
 497          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
 498          * called as close as possible to 500 ms before the new second starts.
 499          * This code is run on a timer.  If the clock is set, that timer
 500          * may not expire at the correct time.  Thus, we adjust...
 501          */
 502         if (!ntp_synced()) {
 503                 /*
 504                  * Not synced, exit, do not restart a timer (if one is
 505                  * running, let it run out).
 506                  */
 507                 return;
 508         }
 509
 510         getnstimeofday(&now);
 511         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
 512                 fail = update_persistent_clock(now);
 513
 514         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 515         if (next.tv_nsec <= 0)
 516                 next.tv_nsec += NSEC_PER_SEC;
 517
 518         if (!fail)
 519                 next.tv_sec = 659;
 520         else
 521                 next.tv_sec = 0;
 522
 523         if (next.tv_nsec >= NSEC_PER_SEC) {
 524                 next.tv_sec++;
 525                 next.tv_nsec -= NSEC_PER_SEC;
 526         }
 527         schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
 528 }
 529
 530 static void notify_cmos_timer(void)
 531 {
 532         schedule_delayed_work(&sync_cmos_work, 0);
 533 }
 534
 535 #else
 536 static inline void notify_cmos_timer(void) { }
 537 #endif
 538
 539
 540 /*
 541  * Propagate a new txc->status value into the NTP state:
 542  */
 543 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
 544 {
 545         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 546                 time_state = TIME_OK;
 547                 time_status = STA_UNSYNC;
 548                 /* restart PPS frequency calibration */
 549                 pps_reset_freq_interval();
 550         }
 551
 552         /*
 553          * If we turn on PLL adjustments then reset the
 554          * reference time to current time.
 555          */
 556         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 557                 time_reftime = get_seconds();
 558
 559         /* only set allowed bits */
 560         time_status &= STA_RONLY;
 561         time_status |= txc->status & ~STA_RONLY;
 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
 646         if (txc->modes & ADJ_SETOFFSET) {
 647                 struct timespec delta;
 648                 delta.tv_sec  = txc->time.tv_sec;
 649                 delta.tv_nsec = txc->time.tv_usec;
 650                 if (!capable(CAP_SYS_TIME))
 651                         return -EPERM;
 652                 if (!(txc->modes & ADJ_NANO))
 653                         delta.tv_nsec *= 1000;
 654                 result = timekeeping_inject_offset(&delta);
 655                 if (result)
 656                         return result;
 657         }
 658
 659         getnstimeofday(&ts);
 660
 661         spin_lock_irq(&ntp_lock);
 662
 663         if (txc->modes & ADJ_ADJTIME) {
 664                 long save_adjust = time_adjust;
 665
 666                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 667                         /* adjtime() is independent from ntp_adjtime() */
 668                         time_adjust = txc->offset;
 669                         ntp_update_frequency();
 670                 }
 671                 txc->offset = save_adjust;
 672         } else {
 673
 674                 /* If there are input parameters, then process them: */
 675                 if (txc->modes)
 676                         process_adjtimex_modes(txc, &ts);
 677
 678                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 679                                   NTP_SCALE_SHIFT);
 680                 if (!(time_status & STA_NANO))
 681                         txc->offset /= NSEC_PER_USEC;
 682         }
 683
 684         result = time_state;    /* mostly `TIME_OK' */
 685         /* check for errors */
 686         if (is_error_status(time_status))
 687                 result = TIME_ERROR;
 688
 689         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 690                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 691         txc->maxerror      = time_maxerror;
 692         txc->esterror      = time_esterror;
 693         txc->status        = time_status;
 694         txc->constant      = time_constant;
 695         txc->precision     = 1;
 696         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 697         txc->tick          = tick_usec;
 698         txc->tai           = time_tai;
 699
 700         /* fill PPS status fields */
 701         pps_fill_timex(txc);
 702
 703         spin_unlock_irq(&ntp_lock);
 704
 705         txc->time.tv_sec = ts.tv_sec;
 706         txc->time.tv_usec = ts.tv_nsec;
 707         if (!(time_status & STA_NANO))
 708                 txc->time.tv_usec /= NSEC_PER_USEC;
 709
 710         notify_cmos_timer();
 711
 712         return result;
 713 }
 714
 715 #ifdef  CONFIG_NTP_PPS
 716
 717 /* actually struct pps_normtime is good old struct timespec, but it is
 718  * semantically different (and it is the reason why it was invented):
 719  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 720  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 721 struct pps_normtime {
 722         __kernel_time_t sec;    /* seconds */
 723         long            nsec;   /* nanoseconds */
 724 };
 725
 726 /* normalize the timestamp so that nsec is in the
 727    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 728 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
 729 {
 730         struct pps_normtime norm = {
 731                 .sec = ts.tv_sec,
 732                 .nsec = ts.tv_nsec
 733         };
 734
 735         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 736                 norm.nsec -= NSEC_PER_SEC;
 737                 norm.sec++;
 738         }
 739
 740         return norm;
 741 }
 742
 743 /* get current phase correction and jitter */
 744 static inline long pps_phase_filter_get(long *jitter)
 745 {
 746         *jitter = pps_tf[0] - pps_tf[1];
 747         if (*jitter < 0)
 748                 *jitter = -*jitter;
 749
 750         /* TODO: test various filters */
 751         return pps_tf[0];
 752 }
 753
 754 /* add the sample to the phase filter */
 755 static inline void pps_phase_filter_add(long err)
 756 {
 757         pps_tf[2] = pps_tf[1];
 758         pps_tf[1] = pps_tf[0];
 759         pps_tf[0] = err;
 760 }
 761
 762 /* decrease frequency calibration interval length.
 763  * It is halved after four consecutive unstable intervals.
 764  */
 765 static inline void pps_dec_freq_interval(void)
 766 {
 767         if (--pps_intcnt <= -PPS_INTCOUNT) {
 768                 pps_intcnt = -PPS_INTCOUNT;
 769                 if (pps_shift > PPS_INTMIN) {
 770                         pps_shift--;
 771                         pps_intcnt = 0;
 772                 }
 773         }
 774 }
 775
 776 /* increase frequency calibration interval length.
 777  * It is doubled after four consecutive stable intervals.
 778  */
 779 static inline void pps_inc_freq_interval(void)
 780 {
 781         if (++pps_intcnt >= PPS_INTCOUNT) {
 782                 pps_intcnt = PPS_INTCOUNT;
 783                 if (pps_shift < PPS_INTMAX) {
 784                         pps_shift++;
 785                         pps_intcnt = 0;
 786                 }
 787         }
 788 }
 789
 790 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 791  * timestamps
 792  *
 793  * At the end of the calibration interval the difference between the
 794  * first and last MONOTONIC_RAW clock timestamps divided by the length
 795  * of the interval becomes the frequency update. If the interval was
 796  * too long, the data are discarded.
 797  * Returns the difference between old and new frequency values.
 798  */
 799 static long hardpps_update_freq(struct pps_normtime freq_norm)
 800 {
 801         long delta, delta_mod;
 802         s64 ftemp;
 803
 804         /* check if the frequency interval was too long */
 805         if (freq_norm.sec > (2 << pps_shift)) {
 806                 time_status |= STA_PPSERROR;
 807                 pps_errcnt++;
 808                 pps_dec_freq_interval();
 809                 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
 810                                 freq_norm.sec);
 811                 return 0;
 812         }
 813
 814         /* here the raw frequency offset and wander (stability) is
 815          * calculated. If the wander is less than the wander threshold
 816          * the interval is increased; otherwise it is decreased.
 817          */
 818         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 819                         freq_norm.sec);
 820         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 821         pps_freq = ftemp;
 822         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 823                 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
 824                 time_status |= STA_PPSWANDER;
 825                 pps_stbcnt++;
 826                 pps_dec_freq_interval();
 827         } else {        /* good sample */
 828                 pps_inc_freq_interval();
 829         }
 830
 831         /* the stability metric is calculated as the average of recent
 832          * frequency changes, but is used only for performance
 833          * monitoring
 834          */
 835         delta_mod = delta;
 836         if (delta_mod < 0)
 837                 delta_mod = -delta_mod;
 838         pps_stabil += (div_s64(((s64)delta_mod) <<
 839                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 840                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 841
 842         /* if enabled, the system clock frequency is updated */
 843         if ((time_status & STA_PPSFREQ) != 0 &&
 844             (time_status & STA_FREQHOLD) == 0) {
 845                 time_freq = pps_freq;
 846                 ntp_update_frequency();
 847         }
 848
 849         return delta;
 850 }
 851
 852 /* correct REALTIME clock phase error against PPS signal */
 853 static void hardpps_update_phase(long error)
 854 {
 855         long correction = -error;
 856         long jitter;
 857
 858         /* add the sample to the median filter */
 859         pps_phase_filter_add(correction);
 860         correction = pps_phase_filter_get(&jitter);
 861
 862         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 863          * threshold, the sample is discarded; otherwise, if so enabled,
 864          * the time offset is updated.
 865          */
 866         if (jitter > (pps_jitter << PPS_POPCORN)) {
 867                 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 868                        jitter, (pps_jitter << PPS_POPCORN));
 869                 time_status |= STA_PPSJITTER;
 870                 pps_jitcnt++;
 871         } else if (time_status & STA_PPSTIME) {
 872                 /* correct the time using the phase offset */
 873                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 874                                 NTP_INTERVAL_FREQ);
 875                 /* cancel running adjtime() */
 876                 time_adjust = 0;
 877         }
 878         /* update jitter */
 879         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 880 }
 881
 882 /*
 883  * hardpps() - discipline CPU clock oscillator to external PPS signal
 884  *
 885  * This routine is called at each PPS signal arrival in order to
 886  * discipline the CPU clock oscillator to the PPS signal. It takes two
 887  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 888  * is used to correct clock phase error and the latter is used to
 889  * correct the frequency.
 890  *
 891  * This code is based on David Mills's reference nanokernel
 892  * implementation. It was mostly rewritten but keeps the same idea.
 893  */
 894 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 895 {
 896         struct pps_normtime pts_norm, freq_norm;
 897         unsigned long flags;
 898
 899         pts_norm = pps_normalize_ts(*phase_ts);
 900
 901         spin_lock_irqsave(&ntp_lock, flags);
 902
 903         /* clear the error bits, they will be set again if needed */
 904         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 905
 906         /* indicate signal presence */
 907         time_status |= STA_PPSSIGNAL;
 908         pps_valid = PPS_VALID;
 909
 910         /* when called for the first time,
 911          * just start the frequency interval */
 912         if (unlikely(pps_fbase.tv_sec == 0)) {
 913                 pps_fbase = *raw_ts;
 914                 spin_unlock_irqrestore(&ntp_lock, flags);
 915                 return;
 916         }
 917
 918         /* ok, now we have a base for frequency calculation */
 919         freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
 920
 921         /* check that the signal is in the range
 922          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 923         if ((freq_norm.sec == 0) ||
 924                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 925                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 926                 time_status |= STA_PPSJITTER;
 927                 /* restart the frequency calibration interval */
 928                 pps_fbase = *raw_ts;
 929                 spin_unlock_irqrestore(&ntp_lock, flags);
 930                 pr_err("hardpps: PPSJITTER: bad pulse\n");
 931                 return;
 932         }
 933
 934         /* signal is ok */
 935
 936         /* check if the current frequency interval is finished */
 937         if (freq_norm.sec >= (1 << pps_shift)) {
 938                 pps_calcnt++;
 939                 /* restart the frequency calibration interval */
 940                 pps_fbase = *raw_ts;
 941                 hardpps_update_freq(freq_norm);
 942         }
 943
 944         hardpps_update_phase(pts_norm.nsec);
 945
 946         spin_unlock_irqrestore(&ntp_lock, flags);
 947 }
 948 EXPORT_SYMBOL(hardpps);
 949
 950 #endif  /* CONFIG_NTP_PPS */
 951
 952 static int __init ntp_tick_adj_setup(char *str)
 953 {
 954         ntp_tick_adj = simple_strtol(str, NULL, 0);
 955         ntp_tick_adj <<= NTP_SCALE_SHIFT;
 956
 957         return 1;
 958 }
 959
 960 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
 961
 962 void __init ntp_init(void)
 963 {
 964         ntp_clear();
 965 }