kernel/time/ntp.c

   1 /*
   2  * NTP state machine interfaces and logic.
   3  *
   4  * This code was mainly moved from kernel/timer.c and kernel/time.c
   5  * Please see those files for relevant copyright info and historical
   6  * changelogs.
   7  */
   8 #include <linux/capability.h>
   9 #include <linux/clocksource.h>
  10 #include <linux/workqueue.h>
  11 #include <linux/hrtimer.h>
  12 #include <linux/jiffies.h>
  13 #include <linux/math64.h>
  14 #include <linux/timex.h>
  15 #include <linux/time.h>
  16 #include <linux/mm.h>
  17 #include <linux/module.h>
  18 #include <linux/rtc.h>
  19
  20 #include "tick-internal.h"
  21 #include "ntp_internal.h"
  22
  23 /*
  24  * NTP timekeeping variables:
  25  *
  26  * Note: All of the NTP state is protected by the timekeeping locks.
  27  */
  28
  29
  30 /* USER_HZ period (usecs): */
  31 unsigned long                   tick_usec = TICK_USEC;
  32
  33 /* SHIFTED_HZ period (nsecs): */
  34 unsigned long                   tick_nsec;
  35
  36 static u64                      tick_length;
  37 static u64                      tick_length_base;
  38
  39 #define MAX_TICKADJ             500LL           /* usecs */
  40 #define MAX_TICKADJ_SCALED \
  41         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  42
  43 /*
  44  * phase-lock loop variables
  45  */
  46
  47 /*
  48  * clock synchronization status
  49  *
  50  * (TIME_ERROR prevents overwriting the CMOS clock)
  51  */
  52 static int                      time_state = TIME_OK;
  53
  54 /* clock status bits:                                                   */
  55 static int                      time_status = STA_UNSYNC;
  56
  57 /* time adjustment (nsecs):                                             */
  58 static s64                      time_offset;
  59
  60 /* pll time constant:                                                   */
  61 static long                     time_constant = 2;
  62
  63 /* maximum error (usecs):                                               */
  64 static long                     time_maxerror = NTP_PHASE_LIMIT;
  65
  66 /* estimated error (usecs):                                             */
  67 static long                     time_esterror = NTP_PHASE_LIMIT;
  68
  69 /* frequency offset (scaled nsecs/secs):                                */
  70 static s64                      time_freq;
  71
  72 /* time at last adjustment (secs):                                      */
  73 static long                     time_reftime;
  74
  75 static long                     time_adjust;
  76
  77 /* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
  78 static s64                      ntp_tick_adj;
  79
  80 #ifdef CONFIG_NTP_PPS
  81
  82 /*
  83  * The following variables are used when a pulse-per-second (PPS) signal
  84  * is available. They establish the engineering parameters of the clock
  85  * discipline loop when controlled by the PPS signal.
  86  */
  87 #define PPS_VALID       10      /* PPS signal watchdog max (s) */
  88 #define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
  89 #define PPS_INTMIN      2       /* min freq interval (s) (shift) */
  90 #define PPS_INTMAX      8       /* max freq interval (s) (shift) */
  91 #define PPS_INTCOUNT    4       /* number of consecutive good intervals to
  92                                    increase pps_shift or consecutive bad
  93                                    intervals to decrease it */
  94 #define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
  95
  96 static int pps_valid;           /* signal watchdog counter */
  97 static long pps_tf[3];          /* phase median filter */
  98 static long pps_jitter;         /* current jitter (ns) */
  99 static struct timespec pps_fbase; /* beginning of the last freq interval */
 100 static int pps_shift;           /* current interval duration (s) (shift) */
 101 static int pps_intcnt;          /* interval counter */
 102 static s64 pps_freq;            /* frequency offset (scaled ns/s) */
 103 static long pps_stabil;         /* current stability (scaled ns/s) */
 104
 105 /*
 106  * PPS signal quality monitors
 107  */
 108 static long pps_calcnt;         /* calibration intervals */
 109 static long pps_jitcnt;         /* jitter limit exceeded */
 110 static long pps_stbcnt;         /* stability limit exceeded */
 111 static long pps_errcnt;         /* calibration errors */
 112
 113
 114 /* PPS kernel consumer compensates the whole phase error immediately.
 115  * Otherwise, reduce the offset by a fixed factor times the time constant.
 116  */
 117 static inline s64 ntp_offset_chunk(s64 offset)
 118 {
 119         if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
 120                 return offset;
 121         else
 122                 return shift_right(offset, SHIFT_PLL + time_constant);
 123 }
 124
 125 static inline void pps_reset_freq_interval(void)
 126 {
 127         /* the PPS calibration interval may end
 128            surprisingly early */
 129         pps_shift = PPS_INTMIN;
 130         pps_intcnt = 0;
 131 }
 132
 133 /**
 134  * pps_clear - Clears the PPS state variables
 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 static inline void pps_dec_valid(void)
 151 {
 152         if (pps_valid > 0)
 153                 pps_valid--;
 154         else {
 155                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 156                                  STA_PPSWANDER | STA_PPSERROR);
 157                 pps_clear();
 158         }
 159 }
 160
 161 static inline void pps_set_freq(s64 freq)
 162 {
 163         pps_freq = freq;
 164 }
 165
 166 static inline int is_error_status(int status)
 167 {
 168         return (time_status & (STA_UNSYNC|STA_CLOCKERR))
 169                 /* PPS signal lost when either PPS time or
 170                  * PPS frequency synchronization requested
 171                  */
 172                 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
 173                         && !(time_status & STA_PPSSIGNAL))
 174                 /* PPS jitter exceeded when
 175                  * PPS time synchronization requested */
 176                 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
 177                         == (STA_PPSTIME|STA_PPSJITTER))
 178                 /* PPS wander exceeded or calibration error when
 179                  * PPS frequency synchronization requested
 180                  */
 181                 || ((time_status & STA_PPSFREQ)
 182                         && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
 183 }
 184
 185 static inline void pps_fill_timex(struct timex *txc)
 186 {
 187         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 188                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 189         txc->jitter        = pps_jitter;
 190         if (!(time_status & STA_NANO))
 191                 txc->jitter /= NSEC_PER_USEC;
 192         txc->shift         = pps_shift;
 193         txc->stabil        = pps_stabil;
 194         txc->jitcnt        = pps_jitcnt;
 195         txc->calcnt        = pps_calcnt;
 196         txc->errcnt        = pps_errcnt;
 197         txc->stbcnt        = pps_stbcnt;
 198 }
 199
 200 #else /* !CONFIG_NTP_PPS */
 201
 202 static inline s64 ntp_offset_chunk(s64 offset)
 203 {
 204         return shift_right(offset, SHIFT_PLL + time_constant);
 205 }
 206
 207 static inline void pps_reset_freq_interval(void) {}
 208 static inline void pps_clear(void) {}
 209 static inline void pps_dec_valid(void) {}
 210 static inline void pps_set_freq(s64 freq) {}
 211
 212 static inline int is_error_status(int status)
 213 {
 214         return status & (STA_UNSYNC|STA_CLOCKERR);
 215 }
 216
 217 static inline void pps_fill_timex(struct timex *txc)
 218 {
 219         /* PPS is not implemented, so these are zero */
 220         txc->ppsfreq       = 0;
 221         txc->jitter        = 0;
 222         txc->shift         = 0;
 223         txc->stabil        = 0;
 224         txc->jitcnt        = 0;
 225         txc->calcnt        = 0;
 226         txc->errcnt        = 0;
 227         txc->stbcnt        = 0;
 228 }
 229
 230 #endif /* CONFIG_NTP_PPS */
 231
 232
 233 /**
 234  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 235  *
 236  */
 237 static inline int ntp_synced(void)
 238 {
 239         return !(time_status & STA_UNSYNC);
 240 }
 241
 242
 243 /*
 244  * NTP methods:
 245  */
 246
 247 /*
 248  * Update (tick_length, tick_length_base, tick_nsec), based
 249  * on (tick_usec, ntp_tick_adj, time_freq):
 250  */
 251 static void ntp_update_frequency(void)
 252 {
 253         u64 second_length;
 254         u64 new_base;
 255
 256         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 257                                                 << NTP_SCALE_SHIFT;
 258
 259         second_length           += ntp_tick_adj;
 260         second_length           += time_freq;
 261
 262         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 263         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 264
 265         /*
 266          * Don't wait for the next second_overflow, apply
 267          * the change to the tick length immediately:
 268          */
 269         tick_length             += new_base - tick_length_base;
 270         tick_length_base         = new_base;
 271 }
 272
 273 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 274 {
 275         time_status &= ~STA_MODE;
 276
 277         if (secs < MINSEC)
 278                 return 0;
 279
 280         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 281                 return 0;
 282
 283         time_status |= STA_MODE;
 284
 285         return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 286 }
 287
 288 static void ntp_update_offset(long offset)
 289 {
 290         s64 freq_adj;
 291         s64 offset64;
 292         long secs;
 293
 294         if (!(time_status & STA_PLL))
 295                 return;
 296
 297         if (!(time_status & STA_NANO))
 298                 offset *= NSEC_PER_USEC;
 299
 300         /*
 301          * Scale the phase adjustment and
 302          * clamp to the operating range.
 303          */
 304         offset = min(offset, MAXPHASE);
 305         offset = max(offset, -MAXPHASE);
 306
 307         /*
 308          * Select how the frequency is to be controlled
 309          * and in which mode (PLL or FLL).
 310          */
 311         secs = get_seconds() - time_reftime;
 312         if (unlikely(time_status & STA_FREQHOLD))
 313                 secs = 0;
 314
 315         time_reftime = get_seconds();
 316
 317         offset64    = offset;
 318         freq_adj    = ntp_update_offset_fll(offset64, secs);
 319
 320         /*
 321          * Clamp update interval to reduce PLL gain with low
 322          * sampling rate (e.g. intermittent network connection)
 323          * to avoid instability.
 324          */
 325         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 326                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
 327
 328         freq_adj    += (offset64 * secs) <<
 329                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 330
 331         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 332
 333         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 334
 335         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 336 }
 337
 338 /**
 339  * ntp_clear - Clears the NTP state variables
 340  */
 341 void ntp_clear(void)
 342 {
 343         time_adjust     = 0;            /* stop active adjtime() */
 344         time_status     |= STA_UNSYNC;
 345         time_maxerror   = NTP_PHASE_LIMIT;
 346         time_esterror   = NTP_PHASE_LIMIT;
 347
 348         ntp_update_frequency();
 349
 350         tick_length     = tick_length_base;
 351         time_offset     = 0;
 352
 353         /* Clear PPS state variables */
 354         pps_clear();
 355 }
 356
 357
 358 u64 ntp_tick_length(void)
 359 {
 360         return tick_length;
 361 }
 362
 363
 364 /*
 365  * this routine handles the overflow of the microsecond field
 366  *
 367  * The tricky bits of code to handle the accurate clock support
 368  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 369  * They were originally developed for SUN and DEC kernels.
 370  * All the kudos should go to Dave for this stuff.
 371  *
 372  * Also handles leap second processing, and returns leap offset
 373  */
 374 int second_overflow(unsigned long secs)
 375 {
 376         s64 delta;
 377         int leap = 0;
 378
 379         /*
 380          * Leap second processing. If in leap-insert state at the end of the
 381          * day, the system clock is set back one second; if in leap-delete
 382          * state, the system clock is set ahead one second.
 383          */
 384         switch (time_state) {
 385         case TIME_OK:
 386                 if (time_status & STA_INS)
 387                         time_state = TIME_INS;
 388                 else if (time_status & STA_DEL)
 389                         time_state = TIME_DEL;
 390                 break;
 391         case TIME_INS:
 392                 if (!(time_status & STA_INS))
 393                         time_state = TIME_OK;
 394                 else if (secs % 86400 == 0) {
 395                         leap = -1;
 396                         time_state = TIME_OOP;
 397                         printk(KERN_NOTICE
 398                                 "Clock: inserting leap second 23:59:60 UTC\n");
 399                 }
 400                 break;
 401         case TIME_DEL:
 402                 if (!(time_status & STA_DEL))
 403                         time_state = TIME_OK;
 404                 else if ((secs + 1) % 86400 == 0) {
 405                         leap = 1;
 406                         time_state = TIME_WAIT;
 407                         printk(KERN_NOTICE
 408                                 "Clock: deleting leap second 23:59:59 UTC\n");
 409                 }
 410                 break;
 411         case TIME_OOP:
 412                 time_state = TIME_WAIT;
 413                 break;
 414
 415         case TIME_WAIT:
 416                 if (!(time_status & (STA_INS | STA_DEL)))
 417                         time_state = TIME_OK;
 418                 break;
 419         }
 420
 421
 422         /* Bump the maxerror field */
 423         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 424         if (time_maxerror > NTP_PHASE_LIMIT) {
 425                 time_maxerror = NTP_PHASE_LIMIT;
 426                 time_status |= STA_UNSYNC;
 427         }
 428
 429         /* Compute the phase adjustment for the next second */
 430         tick_length      = tick_length_base;
 431
 432         delta            = ntp_offset_chunk(time_offset);
 433         time_offset     -= delta;
 434         tick_length     += delta;
 435
 436         /* Check PPS signal */
 437         pps_dec_valid();
 438
 439         if (!time_adjust)
 440                 goto out;
 441
 442         if (time_adjust > MAX_TICKADJ) {
 443                 time_adjust -= MAX_TICKADJ;
 444                 tick_length += MAX_TICKADJ_SCALED;
 445                 goto out;
 446         }
 447
 448         if (time_adjust < -MAX_TICKADJ) {
 449                 time_adjust += MAX_TICKADJ;
 450                 tick_length -= MAX_TICKADJ_SCALED;
 451                 goto out;
 452         }
 453
 454         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 455                                                          << NTP_SCALE_SHIFT;
 456         time_adjust = 0;
 457
 458 out:
 459         return leap;
 460 }
 461
 462 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
 463 static void sync_cmos_clock(struct work_struct *work);
 464
 465 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
 466
 467 static void sync_cmos_clock(struct work_struct *work)
 468 {
 469         struct timespec now, next;
 470         int fail = 1;
 471
 472         /*
 473          * If we have an externally synchronized Linux clock, then update
 474          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
 475          * called as close as possible to 500 ms before the new second starts.
 476          * This code is run on a timer.  If the clock is set, that timer
 477          * may not expire at the correct time.  Thus, we adjust...
 478          * We want the clock to be within a couple of ticks from the target.
 479          */
 480         if (!ntp_synced()) {
 481                 /*
 482                  * Not synced, exit, do not restart a timer (if one is
 483                  * running, let it run out).
 484                  */
 485                 return;
 486         }
 487
 488         getnstimeofday(&now);
 489         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) {
 490                 struct timespec adjust = now;
 491
 492                 fail = -ENODEV;
 493                 if (persistent_clock_is_local)
 494                         adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
 495 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 496                 fail = update_persistent_clock(adjust);
 497 #endif
 498 #ifdef CONFIG_RTC_SYSTOHC
 499                 if (fail == -ENODEV)
 500                         fail = rtc_set_ntp_time(adjust);
 501 #endif
 502         }
 503
 504         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 505         if (next.tv_nsec <= 0)
 506                 next.tv_nsec += NSEC_PER_SEC;
 507
 508         if (!fail || fail == -ENODEV)
 509                 next.tv_sec = 659;
 510         else
 511                 next.tv_sec = 0;
 512
 513         if (next.tv_nsec >= NSEC_PER_SEC) {
 514                 next.tv_sec++;
 515                 next.tv_nsec -= NSEC_PER_SEC;
 516         }
 517         schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
 518 }
 519
 520 void ntp_notify_cmos_timer(void)
 521 {
 522         schedule_delayed_work(&sync_cmos_work, 0);
 523 }
 524
 525 #else
 526 void ntp_notify_cmos_timer(void) { }
 527 #endif
 528
 529
 530 /*
 531  * Propagate a new txc->status value into the NTP state:
 532  */
 533 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
 534 {
 535         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 536                 time_state = TIME_OK;
 537                 time_status = STA_UNSYNC;
 538                 /* restart PPS frequency calibration */
 539                 pps_reset_freq_interval();
 540         }
 541
 542         /*
 543          * If we turn on PLL adjustments then reset the
 544          * reference time to current time.
 545          */
 546         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 547                 time_reftime = get_seconds();
 548
 549         /* only set allowed bits */
 550         time_status &= STA_RONLY;
 551         time_status |= txc->status & ~STA_RONLY;
 552 }
 553
 554
 555 static inline void process_adjtimex_modes(struct timex *txc,
 556                                                 struct timespec *ts,
 557                                                 s32 *time_tai)
 558 {
 559         if (txc->modes & ADJ_STATUS)
 560                 process_adj_status(txc, ts);
 561
 562         if (txc->modes & ADJ_NANO)
 563                 time_status |= STA_NANO;
 564
 565         if (txc->modes & ADJ_MICRO)
 566                 time_status &= ~STA_NANO;
 567
 568         if (txc->modes & ADJ_FREQUENCY) {
 569                 time_freq = txc->freq * PPM_SCALE;
 570                 time_freq = min(time_freq, MAXFREQ_SCALED);
 571                 time_freq = max(time_freq, -MAXFREQ_SCALED);
 572                 /* update pps_freq */
 573                 pps_set_freq(time_freq);
 574         }
 575
 576         if (txc->modes & ADJ_MAXERROR)
 577                 time_maxerror = txc->maxerror;
 578
 579         if (txc->modes & ADJ_ESTERROR)
 580                 time_esterror = txc->esterror;
 581
 582         if (txc->modes & ADJ_TIMECONST) {
 583                 time_constant = txc->constant;
 584                 if (!(time_status & STA_NANO))
 585                         time_constant += 4;
 586                 time_constant = min(time_constant, (long)MAXTC);
 587                 time_constant = max(time_constant, 0l);
 588         }
 589
 590         if (txc->modes & ADJ_TAI && txc->constant > 0)
 591                 *time_tai = txc->constant;
 592
 593         if (txc->modes & ADJ_OFFSET)
 594                 ntp_update_offset(txc->offset);
 595
 596         if (txc->modes & ADJ_TICK)
 597                 tick_usec = txc->tick;
 598
 599         if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 600                 ntp_update_frequency();
 601 }
 602
 603
 604
 605 /**
 606  * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex
 607  */
 608 int ntp_validate_timex(struct timex *txc)
 609 {
 610         if (txc->modes & ADJ_ADJTIME) {
 611                 /* singleshot must not be used with any other mode bits */
 612                 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
 613                         return -EINVAL;
 614                 if (!(txc->modes & ADJ_OFFSET_READONLY) &&
 615                     !capable(CAP_SYS_TIME))
 616                         return -EPERM;
 617         } else {
 618                 /* In order to modify anything, you gotta be super-user! */
 619                  if (txc->modes && !capable(CAP_SYS_TIME))
 620                         return -EPERM;
 621                 /*
 622                  * if the quartz is off by more than 10% then
 623                  * something is VERY wrong!
 624                  */
 625                 if (txc->modes & ADJ_TICK &&
 626                     (txc->tick <  900000/USER_HZ ||
 627                      txc->tick > 1100000/USER_HZ))
 628                         return -EINVAL;
 629         }
 630
 631         if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME)))
 632                 return -EPERM;
 633
 634         return 0;
 635 }
 636
 637
 638 /*
 639  * adjtimex mainly allows reading (and writing, if superuser) of
 640  * kernel time-keeping variables. used by xntpd.
 641  */
 642 int __do_adjtimex(struct timex *txc, struct timespec *ts, s32 *time_tai)
 643 {
 644         int result;
 645
 646         if (txc->modes & ADJ_ADJTIME) {
 647                 long save_adjust = time_adjust;
 648
 649                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 650                         /* adjtime() is independent from ntp_adjtime() */
 651                         time_adjust = txc->offset;
 652                         ntp_update_frequency();
 653                 }
 654                 txc->offset = save_adjust;
 655         } else {
 656
 657                 /* If there are input parameters, then process them: */
 658                 if (txc->modes)
 659                         process_adjtimex_modes(txc, ts, time_tai);
 660
 661                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 662                                   NTP_SCALE_SHIFT);
 663                 if (!(time_status & STA_NANO))
 664                         txc->offset /= NSEC_PER_USEC;
 665         }
 666
 667         result = time_state;    /* mostly `TIME_OK' */
 668         /* check for errors */
 669         if (is_error_status(time_status))
 670                 result = TIME_ERROR;
 671
 672         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 673                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 674         txc->maxerror      = time_maxerror;
 675         txc->esterror      = time_esterror;
 676         txc->status        = time_status;
 677         txc->constant      = time_constant;
 678         txc->precision     = 1;
 679         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 680         txc->tick          = tick_usec;
 681         txc->tai           = *time_tai;
 682
 683         /* fill PPS status fields */
 684         pps_fill_timex(txc);
 685
 686         txc->time.tv_sec = ts->tv_sec;
 687         txc->time.tv_usec = ts->tv_nsec;
 688         if (!(time_status & STA_NANO))
 689                 txc->time.tv_usec /= NSEC_PER_USEC;
 690
 691         return result;
 692 }
 693
 694 #ifdef  CONFIG_NTP_PPS
 695
 696 /* actually struct pps_normtime is good old struct timespec, but it is
 697  * semantically different (and it is the reason why it was invented):
 698  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 699  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 700 struct pps_normtime {
 701         __kernel_time_t sec;    /* seconds */
 702         long            nsec;   /* nanoseconds */
 703 };
 704
 705 /* normalize the timestamp so that nsec is in the
 706    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 707 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
 708 {
 709         struct pps_normtime norm = {
 710                 .sec = ts.tv_sec,
 711                 .nsec = ts.tv_nsec
 712         };
 713
 714         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 715                 norm.nsec -= NSEC_PER_SEC;
 716                 norm.sec++;
 717         }
 718
 719         return norm;
 720 }
 721
 722 /* get current phase correction and jitter */
 723 static inline long pps_phase_filter_get(long *jitter)
 724 {
 725         *jitter = pps_tf[0] - pps_tf[1];
 726         if (*jitter < 0)
 727                 *jitter = -*jitter;
 728
 729         /* TODO: test various filters */
 730         return pps_tf[0];
 731 }
 732
 733 /* add the sample to the phase filter */
 734 static inline void pps_phase_filter_add(long err)
 735 {
 736         pps_tf[2] = pps_tf[1];
 737         pps_tf[1] = pps_tf[0];
 738         pps_tf[0] = err;
 739 }
 740
 741 /* decrease frequency calibration interval length.
 742  * It is halved after four consecutive unstable intervals.
 743  */
 744 static inline void pps_dec_freq_interval(void)
 745 {
 746         if (--pps_intcnt <= -PPS_INTCOUNT) {
 747                 pps_intcnt = -PPS_INTCOUNT;
 748                 if (pps_shift > PPS_INTMIN) {
 749                         pps_shift--;
 750                         pps_intcnt = 0;
 751                 }
 752         }
 753 }
 754
 755 /* increase frequency calibration interval length.
 756  * It is doubled after four consecutive stable intervals.
 757  */
 758 static inline void pps_inc_freq_interval(void)
 759 {
 760         if (++pps_intcnt >= PPS_INTCOUNT) {
 761                 pps_intcnt = PPS_INTCOUNT;
 762                 if (pps_shift < PPS_INTMAX) {
 763                         pps_shift++;
 764                         pps_intcnt = 0;
 765                 }
 766         }
 767 }
 768
 769 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 770  * timestamps
 771  *
 772  * At the end of the calibration interval the difference between the
 773  * first and last MONOTONIC_RAW clock timestamps divided by the length
 774  * of the interval becomes the frequency update. If the interval was
 775  * too long, the data are discarded.
 776  * Returns the difference between old and new frequency values.
 777  */
 778 static long hardpps_update_freq(struct pps_normtime freq_norm)
 779 {
 780         long delta, delta_mod;
 781         s64 ftemp;
 782
 783         /* check if the frequency interval was too long */
 784         if (freq_norm.sec > (2 << pps_shift)) {
 785                 time_status |= STA_PPSERROR;
 786                 pps_errcnt++;
 787                 pps_dec_freq_interval();
 788                 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
 789                                 freq_norm.sec);
 790                 return 0;
 791         }
 792
 793         /* here the raw frequency offset and wander (stability) is
 794          * calculated. If the wander is less than the wander threshold
 795          * the interval is increased; otherwise it is decreased.
 796          */
 797         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 798                         freq_norm.sec);
 799         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 800         pps_freq = ftemp;
 801         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 802                 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
 803                 time_status |= STA_PPSWANDER;
 804                 pps_stbcnt++;
 805                 pps_dec_freq_interval();
 806         } else {        /* good sample */
 807                 pps_inc_freq_interval();
 808         }
 809
 810         /* the stability metric is calculated as the average of recent
 811          * frequency changes, but is used only for performance
 812          * monitoring
 813          */
 814         delta_mod = delta;
 815         if (delta_mod < 0)
 816                 delta_mod = -delta_mod;
 817         pps_stabil += (div_s64(((s64)delta_mod) <<
 818                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 819                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 820
 821         /* if enabled, the system clock frequency is updated */
 822         if ((time_status & STA_PPSFREQ) != 0 &&
 823             (time_status & STA_FREQHOLD) == 0) {
 824                 time_freq = pps_freq;
 825                 ntp_update_frequency();
 826         }
 827
 828         return delta;
 829 }
 830
 831 /* correct REALTIME clock phase error against PPS signal */
 832 static void hardpps_update_phase(long error)
 833 {
 834         long correction = -error;
 835         long jitter;
 836
 837         /* add the sample to the median filter */
 838         pps_phase_filter_add(correction);
 839         correction = pps_phase_filter_get(&jitter);
 840
 841         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 842          * threshold, the sample is discarded; otherwise, if so enabled,
 843          * the time offset is updated.
 844          */
 845         if (jitter > (pps_jitter << PPS_POPCORN)) {
 846                 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 847                        jitter, (pps_jitter << PPS_POPCORN));
 848                 time_status |= STA_PPSJITTER;
 849                 pps_jitcnt++;
 850         } else if (time_status & STA_PPSTIME) {
 851                 /* correct the time using the phase offset */
 852                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 853                                 NTP_INTERVAL_FREQ);
 854                 /* cancel running adjtime() */
 855                 time_adjust = 0;
 856         }
 857         /* update jitter */
 858         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 859 }
 860
 861 /*
 862  * __hardpps() - discipline CPU clock oscillator to external PPS signal
 863  *
 864  * This routine is called at each PPS signal arrival in order to
 865  * discipline the CPU clock oscillator to the PPS signal. It takes two
 866  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 867  * is used to correct clock phase error and the latter is used to
 868  * correct the frequency.
 869  *
 870  * This code is based on David Mills's reference nanokernel
 871  * implementation. It was mostly rewritten but keeps the same idea.
 872  */
 873 void __hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 874 {
 875         struct pps_normtime pts_norm, freq_norm;
 876
 877         pts_norm = pps_normalize_ts(*phase_ts);
 878
 879         /* clear the error bits, they will be set again if needed */
 880         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 881
 882         /* indicate signal presence */
 883         time_status |= STA_PPSSIGNAL;
 884         pps_valid = PPS_VALID;
 885
 886         /* when called for the first time,
 887          * just start the frequency interval */
 888         if (unlikely(pps_fbase.tv_sec == 0)) {
 889                 pps_fbase = *raw_ts;
 890                 return;
 891         }
 892
 893         /* ok, now we have a base for frequency calculation */
 894         freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
 895
 896         /* check that the signal is in the range
 897          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 898         if ((freq_norm.sec == 0) ||
 899                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 900                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 901                 time_status |= STA_PPSJITTER;
 902                 /* restart the frequency calibration interval */
 903                 pps_fbase = *raw_ts;
 904                 pr_err("hardpps: PPSJITTER: bad pulse\n");
 905                 return;
 906         }
 907
 908         /* signal is ok */
 909
 910         /* check if the current frequency interval is finished */
 911         if (freq_norm.sec >= (1 << pps_shift)) {
 912                 pps_calcnt++;
 913                 /* restart the frequency calibration interval */
 914                 pps_fbase = *raw_ts;
 915                 hardpps_update_freq(freq_norm);
 916         }
 917
 918         hardpps_update_phase(pts_norm.nsec);
 919
 920 }
 921 #endif  /* CONFIG_NTP_PPS */
 922
 923 static int __init ntp_tick_adj_setup(char *str)
 924 {
 925         ntp_tick_adj = simple_strtol(str, NULL, 0);
 926         ntp_tick_adj <<= NTP_SCALE_SHIFT;
 927
 928         return 1;
 929 }
 930
 931 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
 932
 933 void __init ntp_init(void)
 934 {
 935         ntp_clear();
 936 }