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 /* SHIFTED_HZ 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 (!(time_status & STA_INS))
 413                         time_state = TIME_OK;
 414                 else if (secs % 86400 == 0) {
 415                         leap = -1;
 416                         time_state = TIME_OOP;
 417                         time_tai++;
 418                         printk(KERN_NOTICE
 419                                 "Clock: inserting leap second 23:59:60 UTC\n");
 420                 }
 421                 break;
 422         case TIME_DEL:
 423                 if (!(time_status & STA_DEL))
 424                         time_state = TIME_OK;
 425                 else if ((secs + 1) % 86400 == 0) {
 426                         leap = 1;
 427                         time_tai--;
 428                         time_state = TIME_WAIT;
 429                         printk(KERN_NOTICE
 430                                 "Clock: deleting leap second 23:59:59 UTC\n");
 431                 }
 432                 break;
 433         case TIME_OOP:
 434                 time_state = TIME_WAIT;
 435                 break;
 436
 437         case TIME_WAIT:
 438                 if (!(time_status & (STA_INS | STA_DEL)))
 439                         time_state = TIME_OK;
 440                 break;
 441         }
 442
 443
 444         /* Bump the maxerror field */
 445         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 446         if (time_maxerror > NTP_PHASE_LIMIT) {
 447                 time_maxerror = NTP_PHASE_LIMIT;
 448                 time_status |= STA_UNSYNC;
 449         }
 450
 451         /* Compute the phase adjustment for the next second */
 452         tick_length      = tick_length_base;
 453
 454         delta            = ntp_offset_chunk(time_offset);
 455         time_offset     -= delta;
 456         tick_length     += delta;
 457
 458         /* Check PPS signal */
 459         pps_dec_valid();
 460
 461         if (!time_adjust)
 462                 goto out;
 463
 464         if (time_adjust > MAX_TICKADJ) {
 465                 time_adjust -= MAX_TICKADJ;
 466                 tick_length += MAX_TICKADJ_SCALED;
 467                 goto out;
 468         }
 469
 470         if (time_adjust < -MAX_TICKADJ) {
 471                 time_adjust += MAX_TICKADJ;
 472                 tick_length -= MAX_TICKADJ_SCALED;
 473                 goto out;
 474         }
 475
 476         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 477                                                          << NTP_SCALE_SHIFT;
 478         time_adjust = 0;
 479
 480 out:
 481         spin_unlock_irqrestore(&ntp_lock, flags);
 482
 483         return leap;
 484 }
 485
 486 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 487
 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                 fail = update_persistent_clock(now);
 515
 516         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 517         if (next.tv_nsec <= 0)
 518                 next.tv_nsec += NSEC_PER_SEC;
 519
 520         if (!fail)
 521                 next.tv_sec = 659;
 522         else
 523                 next.tv_sec = 0;
 524
 525         if (next.tv_nsec >= NSEC_PER_SEC) {
 526                 next.tv_sec++;
 527                 next.tv_nsec -= NSEC_PER_SEC;
 528         }
 529         schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
 530 }
 531
 532 static void notify_cmos_timer(void)
 533 {
 534         schedule_delayed_work(&sync_cmos_work, 0);
 535 }
 536
 537 #else
 538 static inline void notify_cmos_timer(void) { }
 539 #endif
 540
 541
 542 /*
 543  * Propagate a new txc->status value into the NTP state:
 544  */
 545 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
 546 {
 547         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 548                 time_state = TIME_OK;
 549                 time_status = STA_UNSYNC;
 550                 /* restart PPS frequency calibration */
 551                 pps_reset_freq_interval();
 552         }
 553
 554         /*
 555          * If we turn on PLL adjustments then reset the
 556          * reference time to current time.
 557          */
 558         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 559                 time_reftime = get_seconds();
 560
 561         /* only set allowed bits */
 562         time_status &= STA_RONLY;
 563         time_status |= txc->status & ~STA_RONLY;
 564 }
 565
 566 /*
 567  * Called with ntp_lock held, so we can access and modify
 568  * all the global NTP state:
 569  */
 570 static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
 571 {
 572         if (txc->modes & ADJ_STATUS)
 573                 process_adj_status(txc, ts);
 574
 575         if (txc->modes & ADJ_NANO)
 576                 time_status |= STA_NANO;
 577
 578         if (txc->modes & ADJ_MICRO)
 579                 time_status &= ~STA_NANO;
 580
 581         if (txc->modes & ADJ_FREQUENCY) {
 582                 time_freq = txc->freq * PPM_SCALE;
 583                 time_freq = min(time_freq, MAXFREQ_SCALED);
 584                 time_freq = max(time_freq, -MAXFREQ_SCALED);
 585                 /* update pps_freq */
 586                 pps_set_freq(time_freq);
 587         }
 588
 589         if (txc->modes & ADJ_MAXERROR)
 590                 time_maxerror = txc->maxerror;
 591
 592         if (txc->modes & ADJ_ESTERROR)
 593                 time_esterror = txc->esterror;
 594
 595         if (txc->modes & ADJ_TIMECONST) {
 596                 time_constant = txc->constant;
 597                 if (!(time_status & STA_NANO))
 598                         time_constant += 4;
 599                 time_constant = min(time_constant, (long)MAXTC);
 600                 time_constant = max(time_constant, 0l);
 601         }
 602
 603         if (txc->modes & ADJ_TAI && txc->constant > 0)
 604                 time_tai = txc->constant;
 605
 606         if (txc->modes & ADJ_OFFSET)
 607                 ntp_update_offset(txc->offset);
 608
 609         if (txc->modes & ADJ_TICK)
 610                 tick_usec = txc->tick;
 611
 612         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 613                 ntp_update_frequency();
 614 }
 615
 616 /*
 617  * adjtimex mainly allows reading (and writing, if superuser) of
 618  * kernel time-keeping variables. used by xntpd.
 619  */
 620 int do_adjtimex(struct timex *txc)
 621 {
 622         struct timespec ts;
 623         int result;
 624
 625         /* Validate the data before disabling interrupts */
 626         if (txc->modes & ADJ_ADJTIME) {
 627                 /* singleshot must not be used with any other mode bits */
 628                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
 629                         return -EINVAL;
 630                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
 631                     !capable(CAP_SYS_TIME))
 632                         return -EPERM;
 633         } else {
 634                 /* In order to modify anything, you gotta be super-user! */
 635                  if (txc->modes && !capable(CAP_SYS_TIME))
 636                         return -EPERM;
 637
 638                 /*
 639                  * if the quartz is off by more than 10% then
 640                  * something is VERY wrong!
 641                  */
 642                 if (txc->modes & ADJ_TICK &&
 643                     (txc->tick <  900000/USER_HZ ||
 644                      txc->tick > 1100000/USER_HZ))
 645                         return -EINVAL;
 646         }
 647
 648         if (txc->modes & ADJ_SETOFFSET) {
 649                 struct timespec delta;
 650                 delta.tv_sec  = txc->time.tv_sec;
 651                 delta.tv_nsec = txc->time.tv_usec;
 652                 if (!capable(CAP_SYS_TIME))
 653                         return -EPERM;
 654                 if (!(txc->modes & ADJ_NANO))
 655                         delta.tv_nsec *= 1000;
 656                 result = timekeeping_inject_offset(&delta);
 657                 if (result)
 658                         return result;
 659         }
 660
 661         getnstimeofday(&ts);
 662
 663         spin_lock_irq(&ntp_lock);
 664
 665         if (txc->modes & ADJ_ADJTIME) {
 666                 long save_adjust = time_adjust;
 667
 668                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 669                         /* adjtime() is independent from ntp_adjtime() */
 670                         time_adjust = txc->offset;
 671                         ntp_update_frequency();
 672                 }
 673                 txc->offset = save_adjust;
 674         } else {
 675
 676                 /* If there are input parameters, then process them: */
 677                 if (txc->modes)
 678                         process_adjtimex_modes(txc, &ts);
 679
 680                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 681                                   NTP_SCALE_SHIFT);
 682                 if (!(time_status & STA_NANO))
 683                         txc->offset /= NSEC_PER_USEC;
 684         }
 685
 686         result = time_state;    /* mostly `TIME_OK' */
 687         /* check for errors */
 688         if (is_error_status(time_status))
 689                 result = TIME_ERROR;
 690
 691         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 692                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 693         txc->maxerror      = time_maxerror;
 694         txc->esterror      = time_esterror;
 695         txc->status        = time_status;
 696         txc->constant      = time_constant;
 697         txc->precision     = 1;
 698         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 699         txc->tick          = tick_usec;
 700         txc->tai           = time_tai;
 701
 702         /* fill PPS status fields */
 703         pps_fill_timex(txc);
 704
 705         spin_unlock_irq(&ntp_lock);
 706
 707         txc->time.tv_sec = ts.tv_sec;
 708         txc->time.tv_usec = ts.tv_nsec;
 709         if (!(time_status & STA_NANO))
 710                 txc->time.tv_usec /= NSEC_PER_USEC;
 711
 712         notify_cmos_timer();
 713
 714         return result;
 715 }
 716
 717 #ifdef  CONFIG_NTP_PPS
 718
 719 /* actually struct pps_normtime is good old struct timespec, but it is
 720  * semantically different (and it is the reason why it was invented):
 721  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 722  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 723 struct pps_normtime {
 724         __kernel_time_t sec;    /* seconds */
 725         long            nsec;   /* nanoseconds */
 726 };
 727
 728 /* normalize the timestamp so that nsec is in the
 729    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 730 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
 731 {
 732         struct pps_normtime norm = {
 733                 .sec = ts.tv_sec,
 734                 .nsec = ts.tv_nsec
 735         };
 736
 737         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 738                 norm.nsec -= NSEC_PER_SEC;
 739                 norm.sec++;
 740         }
 741
 742         return norm;
 743 }
 744
 745 /* get current phase correction and jitter */
 746 static inline long pps_phase_filter_get(long *jitter)
 747 {
 748         *jitter = pps_tf[0] - pps_tf[1];
 749         if (*jitter < 0)
 750                 *jitter = -*jitter;
 751
 752         /* TODO: test various filters */
 753         return pps_tf[0];
 754 }
 755
 756 /* add the sample to the phase filter */
 757 static inline void pps_phase_filter_add(long err)
 758 {
 759         pps_tf[2] = pps_tf[1];
 760         pps_tf[1] = pps_tf[0];
 761         pps_tf[0] = err;
 762 }
 763
 764 /* decrease frequency calibration interval length.
 765  * It is halved after four consecutive unstable intervals.
 766  */
 767 static inline void pps_dec_freq_interval(void)
 768 {
 769         if (--pps_intcnt <= -PPS_INTCOUNT) {
 770                 pps_intcnt = -PPS_INTCOUNT;
 771                 if (pps_shift > PPS_INTMIN) {
 772                         pps_shift--;
 773                         pps_intcnt = 0;
 774                 }
 775         }
 776 }
 777
 778 /* increase frequency calibration interval length.
 779  * It is doubled after four consecutive stable intervals.
 780  */
 781 static inline void pps_inc_freq_interval(void)
 782 {
 783         if (++pps_intcnt >= PPS_INTCOUNT) {
 784                 pps_intcnt = PPS_INTCOUNT;
 785                 if (pps_shift < PPS_INTMAX) {
 786                         pps_shift++;
 787                         pps_intcnt = 0;
 788                 }
 789         }
 790 }
 791
 792 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 793  * timestamps
 794  *
 795  * At the end of the calibration interval the difference between the
 796  * first and last MONOTONIC_RAW clock timestamps divided by the length
 797  * of the interval becomes the frequency update. If the interval was
 798  * too long, the data are discarded.
 799  * Returns the difference between old and new frequency values.
 800  */
 801 static long hardpps_update_freq(struct pps_normtime freq_norm)
 802 {
 803         long delta, delta_mod;
 804         s64 ftemp;
 805
 806         /* check if the frequency interval was too long */
 807         if (freq_norm.sec > (2 << pps_shift)) {
 808                 time_status |= STA_PPSERROR;
 809                 pps_errcnt++;
 810                 pps_dec_freq_interval();
 811                 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
 812                                 freq_norm.sec);
 813                 return 0;
 814         }
 815
 816         /* here the raw frequency offset and wander (stability) is
 817          * calculated. If the wander is less than the wander threshold
 818          * the interval is increased; otherwise it is decreased.
 819          */
 820         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 821                         freq_norm.sec);
 822         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 823         pps_freq = ftemp;
 824         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 825                 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
 826                 time_status |= STA_PPSWANDER;
 827                 pps_stbcnt++;
 828                 pps_dec_freq_interval();
 829         } else {        /* good sample */
 830                 pps_inc_freq_interval();
 831         }
 832
 833         /* the stability metric is calculated as the average of recent
 834          * frequency changes, but is used only for performance
 835          * monitoring
 836          */
 837         delta_mod = delta;
 838         if (delta_mod < 0)
 839                 delta_mod = -delta_mod;
 840         pps_stabil += (div_s64(((s64)delta_mod) <<
 841                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 842                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 843
 844         /* if enabled, the system clock frequency is updated */
 845         if ((time_status & STA_PPSFREQ) != 0 &&
 846             (time_status & STA_FREQHOLD) == 0) {
 847                 time_freq = pps_freq;
 848                 ntp_update_frequency();
 849         }
 850
 851         return delta;
 852 }
 853
 854 /* correct REALTIME clock phase error against PPS signal */
 855 static void hardpps_update_phase(long error)
 856 {
 857         long correction = -error;
 858         long jitter;
 859
 860         /* add the sample to the median filter */
 861         pps_phase_filter_add(correction);
 862         correction = pps_phase_filter_get(&jitter);
 863
 864         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 865          * threshold, the sample is discarded; otherwise, if so enabled,
 866          * the time offset is updated.
 867          */
 868         if (jitter > (pps_jitter << PPS_POPCORN)) {
 869                 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 870                        jitter, (pps_jitter << PPS_POPCORN));
 871                 time_status |= STA_PPSJITTER;
 872                 pps_jitcnt++;
 873         } else if (time_status & STA_PPSTIME) {
 874                 /* correct the time using the phase offset */
 875                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 876                                 NTP_INTERVAL_FREQ);
 877                 /* cancel running adjtime() */
 878                 time_adjust = 0;
 879         }
 880         /* update jitter */
 881         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 882 }
 883
 884 /*
 885  * hardpps() - discipline CPU clock oscillator to external PPS signal
 886  *
 887  * This routine is called at each PPS signal arrival in order to
 888  * discipline the CPU clock oscillator to the PPS signal. It takes two
 889  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 890  * is used to correct clock phase error and the latter is used to
 891  * correct the frequency.
 892  *
 893  * This code is based on David Mills's reference nanokernel
 894  * implementation. It was mostly rewritten but keeps the same idea.
 895  */
 896 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 897 {
 898         struct pps_normtime pts_norm, freq_norm;
 899         unsigned long flags;
 900
 901         pts_norm = pps_normalize_ts(*phase_ts);
 902
 903         spin_lock_irqsave(&ntp_lock, flags);
 904
 905         /* clear the error bits, they will be set again if needed */
 906         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 907
 908         /* indicate signal presence */
 909         time_status |= STA_PPSSIGNAL;
 910         pps_valid = PPS_VALID;
 911
 912         /* when called for the first time,
 913          * just start the frequency interval */
 914         if (unlikely(pps_fbase.tv_sec == 0)) {
 915                 pps_fbase = *raw_ts;
 916                 spin_unlock_irqrestore(&ntp_lock, flags);
 917                 return;
 918         }
 919
 920         /* ok, now we have a base for frequency calculation */
 921         freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
 922
 923         /* check that the signal is in the range
 924          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 925         if ((freq_norm.sec == 0) ||
 926                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 927                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 928                 time_status |= STA_PPSJITTER;
 929                 /* restart the frequency calibration interval */
 930                 pps_fbase = *raw_ts;
 931                 spin_unlock_irqrestore(&ntp_lock, flags);
 932                 pr_err("hardpps: PPSJITTER: bad pulse\n");
 933                 return;
 934         }
 935
 936         /* signal is ok */
 937
 938         /* check if the current frequency interval is finished */
 939         if (freq_norm.sec >= (1 << pps_shift)) {
 940                 pps_calcnt++;
 941                 /* restart the frequency calibration interval */
 942                 pps_fbase = *raw_ts;
 943                 hardpps_update_freq(freq_norm);
 944         }
 945
 946         hardpps_update_phase(pts_norm.nsec);
 947
 948         spin_unlock_irqrestore(&ntp_lock, flags);
 949 }
 950 EXPORT_SYMBOL(hardpps);
 951
 952 #endif  /* CONFIG_NTP_PPS */
 953
 954 static int __init ntp_tick_adj_setup(char *str)
 955 {
 956         ntp_tick_adj = simple_strtol(str, NULL, 0);
 957         ntp_tick_adj <<= NTP_SCALE_SHIFT;
 958
 959         return 1;
 960 }
 961
 962 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
 963
 964 void __init ntp_init(void)
 965 {
 966         ntp_clear();
 967 }