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 /* USER_HZ period (usecs): */
  26 unsigned long                   tick_usec = TICK_USEC;
  27
  28 /* ACTHZ period (nsecs): */
  29 unsigned long                   tick_nsec;
  30
  31 u64                             tick_length;
  32 static u64                      tick_length_base;
  33
  34 static struct hrtimer           leap_timer;
  35
  36 #define MAX_TICKADJ             500LL           /* usecs */
  37 #define MAX_TICKADJ_SCALED \
  38         (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  39
  40 /*
  41  * phase-lock loop variables
  42  */
  43
  44 /*
  45  * clock synchronization status
  46  *
  47  * (TIME_ERROR prevents overwriting the CMOS clock)
  48  */
  49 static int                      time_state = TIME_OK;
  50
  51 /* clock status bits:                                                   */
  52 int                             time_status = STA_UNSYNC;
  53
  54 /* TAI offset (secs):                                                   */
  55 static long                     time_tai;
  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  * Must be called while holding a write on the xtime_lock
 137  */
 138 static inline void pps_clear(void)
 139 {
 140         pps_reset_freq_interval();
 141         pps_tf[0] = 0;
 142         pps_tf[1] = 0;
 143         pps_tf[2] = 0;
 144         pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
 145         pps_freq = 0;
 146 }
 147
 148 /* Decrease pps_valid to indicate that another second has passed since
 149  * the last PPS signal. When it reaches 0, indicate that PPS signal is
 150  * missing.
 151  *
 152  * Must be called while holding a write on the xtime_lock
 153  */
 154 static inline void pps_dec_valid(void)
 155 {
 156         if (pps_valid > 0)
 157                 pps_valid--;
 158         else {
 159                 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 160                                  STA_PPSWANDER | STA_PPSERROR);
 161                 pps_clear();
 162         }
 163 }
 164
 165 static inline void pps_set_freq(s64 freq)
 166 {
 167         pps_freq = freq;
 168 }
 169
 170 static inline int is_error_status(int status)
 171 {
 172         return (time_status & (STA_UNSYNC|STA_CLOCKERR))
 173                 /* PPS signal lost when either PPS time or
 174                  * PPS frequency synchronization requested
 175                  */
 176                 || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
 177                         && !(time_status & STA_PPSSIGNAL))
 178                 /* PPS jitter exceeded when
 179                  * PPS time synchronization requested */
 180                 || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
 181                         == (STA_PPSTIME|STA_PPSJITTER))
 182                 /* PPS wander exceeded or calibration error when
 183                  * PPS frequency synchronization requested
 184                  */
 185                 || ((time_status & STA_PPSFREQ)
 186                         && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
 187 }
 188
 189 static inline void pps_fill_timex(struct timex *txc)
 190 {
 191         txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 192                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 193         txc->jitter        = pps_jitter;
 194         if (!(time_status & STA_NANO))
 195                 txc->jitter /= NSEC_PER_USEC;
 196         txc->shift         = pps_shift;
 197         txc->stabil        = pps_stabil;
 198         txc->jitcnt        = pps_jitcnt;
 199         txc->calcnt        = pps_calcnt;
 200         txc->errcnt        = pps_errcnt;
 201         txc->stbcnt        = pps_stbcnt;
 202 }
 203
 204 #else /* !CONFIG_NTP_PPS */
 205
 206 static inline s64 ntp_offset_chunk(s64 offset)
 207 {
 208         return shift_right(offset, SHIFT_PLL + time_constant);
 209 }
 210
 211 static inline void pps_reset_freq_interval(void) {}
 212 static inline void pps_clear(void) {}
 213 static inline void pps_dec_valid(void) {}
 214 static inline void pps_set_freq(s64 freq) {}
 215
 216 static inline int is_error_status(int status)
 217 {
 218         return status & (STA_UNSYNC|STA_CLOCKERR);
 219 }
 220
 221 static inline void pps_fill_timex(struct timex *txc)
 222 {
 223         /* PPS is not implemented, so these are zero */
 224         txc->ppsfreq       = 0;
 225         txc->jitter        = 0;
 226         txc->shift         = 0;
 227         txc->stabil        = 0;
 228         txc->jitcnt        = 0;
 229         txc->calcnt        = 0;
 230         txc->errcnt        = 0;
 231         txc->stbcnt        = 0;
 232 }
 233
 234 #endif /* CONFIG_NTP_PPS */
 235
 236 /*
 237  * NTP methods:
 238  */
 239
 240 /*
 241  * Update (tick_length, tick_length_base, tick_nsec), based
 242  * on (tick_usec, ntp_tick_adj, time_freq):
 243  */
 244 static void ntp_update_frequency(void)
 245 {
 246         u64 second_length;
 247         u64 new_base;
 248
 249         second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 250                                                 << NTP_SCALE_SHIFT;
 251
 252         second_length           += ntp_tick_adj;
 253         second_length           += time_freq;
 254
 255         tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 256         new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 257
 258         /*
 259          * Don't wait for the next second_overflow, apply
 260          * the change to the tick length immediately:
 261          */
 262         tick_length             += new_base - tick_length_base;
 263         tick_length_base         = new_base;
 264 }
 265
 266 static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 267 {
 268         time_status &= ~STA_MODE;
 269
 270         if (secs < MINSEC)
 271                 return 0;
 272
 273         if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 274                 return 0;
 275
 276         time_status |= STA_MODE;
 277
 278         return div_s64(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 279 }
 280
 281 static void ntp_update_offset(long offset)
 282 {
 283         s64 freq_adj;
 284         s64 offset64;
 285         long secs;
 286
 287         if (!(time_status & STA_PLL))
 288                 return;
 289
 290         if (!(time_status & STA_NANO))
 291                 offset *= NSEC_PER_USEC;
 292
 293         /*
 294          * Scale the phase adjustment and
 295          * clamp to the operating range.
 296          */
 297         offset = min(offset, MAXPHASE);
 298         offset = max(offset, -MAXPHASE);
 299
 300         /*
 301          * Select how the frequency is to be controlled
 302          * and in which mode (PLL or FLL).
 303          */
 304         secs = get_seconds() - time_reftime;
 305         if (unlikely(time_status & STA_FREQHOLD))
 306                 secs = 0;
 307
 308         time_reftime = get_seconds();
 309
 310         offset64    = offset;
 311         freq_adj    = ntp_update_offset_fll(offset64, secs);
 312
 313         /*
 314          * Clamp update interval to reduce PLL gain with low
 315          * sampling rate (e.g. intermittent network connection)
 316          * to avoid instability.
 317          */
 318         if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 319                 secs = 1 << (SHIFT_PLL + 1 + time_constant);
 320
 321         freq_adj    += (offset64 * secs) <<
 322                         (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 323
 324         freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 325
 326         time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 327
 328         time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 329 }
 330
 331 /**
 332  * ntp_clear - Clears the NTP state variables
 333  *
 334  * Must be called while holding a write on the xtime_lock
 335  */
 336 void ntp_clear(void)
 337 {
 338         time_adjust     = 0;            /* stop active adjtime() */
 339         time_status     |= STA_UNSYNC;
 340         time_maxerror   = NTP_PHASE_LIMIT;
 341         time_esterror   = NTP_PHASE_LIMIT;
 342
 343         ntp_update_frequency();
 344
 345         tick_length     = tick_length_base;
 346         time_offset     = 0;
 347
 348         /* Clear PPS state variables */
 349         pps_clear();
 350 }
 351
 352 /*
 353  * Leap second processing. If in leap-insert state at the end of the
 354  * day, the system clock is set back one second; if in leap-delete
 355  * state, the system clock is set ahead one second.
 356  */
 357 static enum hrtimer_restart ntp_leap_second(struct hrtimer *timer)
 358 {
 359         enum hrtimer_restart res = HRTIMER_NORESTART;
 360
 361         write_seqlock(&xtime_lock);
 362
 363         switch (time_state) {
 364         case TIME_OK:
 365                 break;
 366         case TIME_INS:
 367                 timekeeping_leap_insert(-1);
 368                 time_state = TIME_OOP;
 369                 printk(KERN_NOTICE
 370                         "Clock: inserting leap second 23:59:60 UTC\n");
 371                 hrtimer_add_expires_ns(&leap_timer, NSEC_PER_SEC);
 372                 res = HRTIMER_RESTART;
 373                 break;
 374         case TIME_DEL:
 375                 timekeeping_leap_insert(1);
 376                 time_tai--;
 377                 time_state = TIME_WAIT;
 378                 printk(KERN_NOTICE
 379                         "Clock: deleting leap second 23:59:59 UTC\n");
 380                 break;
 381         case TIME_OOP:
 382                 time_tai++;
 383                 time_state = TIME_WAIT;
 384                 /* fall through */
 385         case TIME_WAIT:
 386                 if (!(time_status & (STA_INS | STA_DEL)))
 387                         time_state = TIME_OK;
 388                 break;
 389         }
 390
 391         write_sequnlock(&xtime_lock);
 392
 393         return res;
 394 }
 395
 396 /*
 397  * this routine handles the overflow of the microsecond field
 398  *
 399  * The tricky bits of code to handle the accurate clock support
 400  * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 401  * They were originally developed for SUN and DEC kernels.
 402  * All the kudos should go to Dave for this stuff.
 403  */
 404 void second_overflow(void)
 405 {
 406         s64 delta;
 407
 408         /* Bump the maxerror field */
 409         time_maxerror += MAXFREQ / NSEC_PER_USEC;
 410         if (time_maxerror > NTP_PHASE_LIMIT) {
 411                 time_maxerror = NTP_PHASE_LIMIT;
 412                 time_status |= STA_UNSYNC;
 413         }
 414
 415         /* Compute the phase adjustment for the next second */
 416         tick_length      = tick_length_base;
 417
 418         delta            = ntp_offset_chunk(time_offset);
 419         time_offset     -= delta;
 420         tick_length     += delta;
 421
 422         /* Check PPS signal */
 423         pps_dec_valid();
 424
 425         if (!time_adjust)
 426                 return;
 427
 428         if (time_adjust > MAX_TICKADJ) {
 429                 time_adjust -= MAX_TICKADJ;
 430                 tick_length += MAX_TICKADJ_SCALED;
 431                 return;
 432         }
 433
 434         if (time_adjust < -MAX_TICKADJ) {
 435                 time_adjust += MAX_TICKADJ;
 436                 tick_length -= MAX_TICKADJ_SCALED;
 437                 return;
 438         }
 439
 440         tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 441                                                          << NTP_SCALE_SHIFT;
 442         time_adjust = 0;
 443 }
 444
 445 #ifdef CONFIG_GENERIC_CMOS_UPDATE
 446
 447 /* Disable the cmos update - used by virtualization and embedded */
 448 int no_sync_cmos_clock  __read_mostly;
 449
 450 static void sync_cmos_clock(struct work_struct *work);
 451
 452 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
 453
 454 static void sync_cmos_clock(struct work_struct *work)
 455 {
 456         struct timespec now, next;
 457         int fail = 1;
 458
 459         /*
 460          * If we have an externally synchronized Linux clock, then update
 461          * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
 462          * called as close as possible to 500 ms before the new second starts.
 463          * This code is run on a timer.  If the clock is set, that timer
 464          * may not expire at the correct time.  Thus, we adjust...
 465          */
 466         if (!ntp_synced()) {
 467                 /*
 468                  * Not synced, exit, do not restart a timer (if one is
 469                  * running, let it run out).
 470                  */
 471                 return;
 472         }
 473
 474         getnstimeofday(&now);
 475         if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec / 2)
 476                 fail = update_persistent_clock(now);
 477
 478         next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 479         if (next.tv_nsec <= 0)
 480                 next.tv_nsec += NSEC_PER_SEC;
 481
 482         if (!fail)
 483                 next.tv_sec = 659;
 484         else
 485                 next.tv_sec = 0;
 486
 487         if (next.tv_nsec >= NSEC_PER_SEC) {
 488                 next.tv_sec++;
 489                 next.tv_nsec -= NSEC_PER_SEC;
 490         }
 491         schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
 492 }
 493
 494 static void notify_cmos_timer(void)
 495 {
 496         if (!no_sync_cmos_clock)
 497                 schedule_delayed_work(&sync_cmos_work, 0);
 498 }
 499
 500 #else
 501 static inline void notify_cmos_timer(void) { }
 502 #endif
 503
 504 /*
 505  * Start the leap seconds timer:
 506  */
 507 static inline void ntp_start_leap_timer(struct timespec *ts)
 508 {
 509         long now = ts->tv_sec;
 510
 511         if (time_status & STA_INS) {
 512                 time_state = TIME_INS;
 513                 now += 86400 - now % 86400;
 514                 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
 515
 516                 return;
 517         }
 518
 519         if (time_status & STA_DEL) {
 520                 time_state = TIME_DEL;
 521                 now += 86400 - (now + 1) % 86400;
 522                 hrtimer_start(&leap_timer, ktime_set(now, 0), HRTIMER_MODE_ABS);
 523         }
 524 }
 525
 526 /*
 527  * Propagate a new txc->status value into the NTP state:
 528  */
 529 static inline void process_adj_status(struct timex *txc, struct timespec *ts)
 530 {
 531         if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 532                 time_state = TIME_OK;
 533                 time_status = STA_UNSYNC;
 534                 /* restart PPS frequency calibration */
 535                 pps_reset_freq_interval();
 536         }
 537
 538         /*
 539          * If we turn on PLL adjustments then reset the
 540          * reference time to current time.
 541          */
 542         if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 543                 time_reftime = get_seconds();
 544
 545         /* only set allowed bits */
 546         time_status &= STA_RONLY;
 547         time_status |= txc->status & ~STA_RONLY;
 548
 549         switch (time_state) {
 550         case TIME_OK:
 551                 ntp_start_leap_timer(ts);
 552                 break;
 553         case TIME_INS:
 554         case TIME_DEL:
 555                 time_state = TIME_OK;
 556                 ntp_start_leap_timer(ts);
 557         case TIME_WAIT:
 558                 if (!(time_status & (STA_INS | STA_DEL)))
 559                         time_state = TIME_OK;
 560                 break;
 561         case TIME_OOP:
 562                 hrtimer_restart(&leap_timer);
 563                 break;
 564         }
 565 }
 566 /*
 567  * Called with the xtime 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                 if (txc->modes & ADJ_STATUS && time_state != TIME_OK)
 648                         hrtimer_cancel(&leap_timer);
 649         }
 650
 651         if (txc->modes & ADJ_SETOFFSET) {
 652                 struct timespec delta;
 653                 delta.tv_sec  = txc->time.tv_sec;
 654                 delta.tv_nsec = txc->time.tv_usec;
 655                 if (!capable(CAP_SYS_TIME))
 656                         return -EPERM;
 657                 if (!(txc->modes & ADJ_NANO))
 658                         delta.tv_nsec *= 1000;
 659                 result = timekeeping_inject_offset(&delta);
 660                 if (result)
 661                         return result;
 662         }
 663
 664         getnstimeofday(&ts);
 665
 666         write_seqlock_irq(&xtime_lock);
 667
 668         if (txc->modes & ADJ_ADJTIME) {
 669                 long save_adjust = time_adjust;
 670
 671                 if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 672                         /* adjtime() is independent from ntp_adjtime() */
 673                         time_adjust = txc->offset;
 674                         ntp_update_frequency();
 675                 }
 676                 txc->offset = save_adjust;
 677         } else {
 678
 679                 /* If there are input parameters, then process them: */
 680                 if (txc->modes)
 681                         process_adjtimex_modes(txc, &ts);
 682
 683                 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 684                                   NTP_SCALE_SHIFT);
 685                 if (!(time_status & STA_NANO))
 686                         txc->offset /= NSEC_PER_USEC;
 687         }
 688
 689         result = time_state;    /* mostly `TIME_OK' */
 690         /* check for errors */
 691         if (is_error_status(time_status))
 692                 result = TIME_ERROR;
 693
 694         txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 695                                          PPM_SCALE_INV, NTP_SCALE_SHIFT);
 696         txc->maxerror      = time_maxerror;
 697         txc->esterror      = time_esterror;
 698         txc->status        = time_status;
 699         txc->constant      = time_constant;
 700         txc->precision     = 1;
 701         txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 702         txc->tick          = tick_usec;
 703         txc->tai           = time_tai;
 704
 705         /* fill PPS status fields */
 706         pps_fill_timex(txc);
 707
 708         write_sequnlock_irq(&xtime_lock);
 709
 710         txc->time.tv_sec = ts.tv_sec;
 711         txc->time.tv_usec = ts.tv_nsec;
 712         if (!(time_status & STA_NANO))
 713                 txc->time.tv_usec /= NSEC_PER_USEC;
 714
 715         notify_cmos_timer();
 716
 717         return result;
 718 }
 719
 720 #ifdef  CONFIG_NTP_PPS
 721
 722 /* actually struct pps_normtime is good old struct timespec, but it is
 723  * semantically different (and it is the reason why it was invented):
 724  * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 725  * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 726 struct pps_normtime {
 727         __kernel_time_t sec;    /* seconds */
 728         long            nsec;   /* nanoseconds */
 729 };
 730
 731 /* normalize the timestamp so that nsec is in the
 732    ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 733 static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
 734 {
 735         struct pps_normtime norm = {
 736                 .sec = ts.tv_sec,
 737                 .nsec = ts.tv_nsec
 738         };
 739
 740         if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 741                 norm.nsec -= NSEC_PER_SEC;
 742                 norm.sec++;
 743         }
 744
 745         return norm;
 746 }
 747
 748 /* get current phase correction and jitter */
 749 static inline long pps_phase_filter_get(long *jitter)
 750 {
 751         *jitter = pps_tf[0] - pps_tf[1];
 752         if (*jitter < 0)
 753                 *jitter = -*jitter;
 754
 755         /* TODO: test various filters */
 756         return pps_tf[0];
 757 }
 758
 759 /* add the sample to the phase filter */
 760 static inline void pps_phase_filter_add(long err)
 761 {
 762         pps_tf[2] = pps_tf[1];
 763         pps_tf[1] = pps_tf[0];
 764         pps_tf[0] = err;
 765 }
 766
 767 /* decrease frequency calibration interval length.
 768  * It is halved after four consecutive unstable intervals.
 769  */
 770 static inline void pps_dec_freq_interval(void)
 771 {
 772         if (--pps_intcnt <= -PPS_INTCOUNT) {
 773                 pps_intcnt = -PPS_INTCOUNT;
 774                 if (pps_shift > PPS_INTMIN) {
 775                         pps_shift--;
 776                         pps_intcnt = 0;
 777                 }
 778         }
 779 }
 780
 781 /* increase frequency calibration interval length.
 782  * It is doubled after four consecutive stable intervals.
 783  */
 784 static inline void pps_inc_freq_interval(void)
 785 {
 786         if (++pps_intcnt >= PPS_INTCOUNT) {
 787                 pps_intcnt = PPS_INTCOUNT;
 788                 if (pps_shift < PPS_INTMAX) {
 789                         pps_shift++;
 790                         pps_intcnt = 0;
 791                 }
 792         }
 793 }
 794
 795 /* update clock frequency based on MONOTONIC_RAW clock PPS signal
 796  * timestamps
 797  *
 798  * At the end of the calibration interval the difference between the
 799  * first and last MONOTONIC_RAW clock timestamps divided by the length
 800  * of the interval becomes the frequency update. If the interval was
 801  * too long, the data are discarded.
 802  * Returns the difference between old and new frequency values.
 803  */
 804 static long hardpps_update_freq(struct pps_normtime freq_norm)
 805 {
 806         long delta, delta_mod;
 807         s64 ftemp;
 808
 809         /* check if the frequency interval was too long */
 810         if (freq_norm.sec > (2 << pps_shift)) {
 811                 time_status |= STA_PPSERROR;
 812                 pps_errcnt++;
 813                 pps_dec_freq_interval();
 814                 pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
 815                                 freq_norm.sec);
 816                 return 0;
 817         }
 818
 819         /* here the raw frequency offset and wander (stability) is
 820          * calculated. If the wander is less than the wander threshold
 821          * the interval is increased; otherwise it is decreased.
 822          */
 823         ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 824                         freq_norm.sec);
 825         delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 826         pps_freq = ftemp;
 827         if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 828                 pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
 829                 time_status |= STA_PPSWANDER;
 830                 pps_stbcnt++;
 831                 pps_dec_freq_interval();
 832         } else {        /* good sample */
 833                 pps_inc_freq_interval();
 834         }
 835
 836         /* the stability metric is calculated as the average of recent
 837          * frequency changes, but is used only for performance
 838          * monitoring
 839          */
 840         delta_mod = delta;
 841         if (delta_mod < 0)
 842                 delta_mod = -delta_mod;
 843         pps_stabil += (div_s64(((s64)delta_mod) <<
 844                                 (NTP_SCALE_SHIFT - SHIFT_USEC),
 845                                 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 846
 847         /* if enabled, the system clock frequency is updated */
 848         if ((time_status & STA_PPSFREQ) != 0 &&
 849             (time_status & STA_FREQHOLD) == 0) {
 850                 time_freq = pps_freq;
 851                 ntp_update_frequency();
 852         }
 853
 854         return delta;
 855 }
 856
 857 /* correct REALTIME clock phase error against PPS signal */
 858 static void hardpps_update_phase(long error)
 859 {
 860         long correction = -error;
 861         long jitter;
 862
 863         /* add the sample to the median filter */
 864         pps_phase_filter_add(correction);
 865         correction = pps_phase_filter_get(&jitter);
 866
 867         /* Nominal jitter is due to PPS signal noise. If it exceeds the
 868          * threshold, the sample is discarded; otherwise, if so enabled,
 869          * the time offset is updated.
 870          */
 871         if (jitter > (pps_jitter << PPS_POPCORN)) {
 872                 pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 873                        jitter, (pps_jitter << PPS_POPCORN));
 874                 time_status |= STA_PPSJITTER;
 875                 pps_jitcnt++;
 876         } else if (time_status & STA_PPSTIME) {
 877                 /* correct the time using the phase offset */
 878                 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 879                                 NTP_INTERVAL_FREQ);
 880                 /* cancel running adjtime() */
 881                 time_adjust = 0;
 882         }
 883         /* update jitter */
 884         pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 885 }
 886
 887 /*
 888  * hardpps() - discipline CPU clock oscillator to external PPS signal
 889  *
 890  * This routine is called at each PPS signal arrival in order to
 891  * discipline the CPU clock oscillator to the PPS signal. It takes two
 892  * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 893  * is used to correct clock phase error and the latter is used to
 894  * correct the frequency.
 895  *
 896  * This code is based on David Mills's reference nanokernel
 897  * implementation. It was mostly rewritten but keeps the same idea.
 898  */
 899 void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 900 {
 901         struct pps_normtime pts_norm, freq_norm;
 902         unsigned long flags;
 903
 904         pts_norm = pps_normalize_ts(*phase_ts);
 905
 906         write_seqlock_irqsave(&xtime_lock, flags);
 907
 908         /* clear the error bits, they will be set again if needed */
 909         time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 910
 911         /* indicate signal presence */
 912         time_status |= STA_PPSSIGNAL;
 913         pps_valid = PPS_VALID;
 914
 915         /* when called for the first time,
 916          * just start the frequency interval */
 917         if (unlikely(pps_fbase.tv_sec == 0)) {
 918                 pps_fbase = *raw_ts;
 919                 write_sequnlock_irqrestore(&xtime_lock, flags);
 920                 return;
 921         }
 922
 923         /* ok, now we have a base for frequency calculation */
 924         freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
 925
 926         /* check that the signal is in the range
 927          * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 928         if ((freq_norm.sec == 0) ||
 929                         (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 930                         (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 931                 time_status |= STA_PPSJITTER;
 932                 /* restart the frequency calibration interval */
 933                 pps_fbase = *raw_ts;
 934                 write_sequnlock_irqrestore(&xtime_lock, flags);
 935                 pr_err("hardpps: PPSJITTER: bad pulse\n");
 936                 return;
 937         }
 938
 939         /* signal is ok */
 940
 941         /* check if the current frequency interval is finished */
 942         if (freq_norm.sec >= (1 << pps_shift)) {
 943                 pps_calcnt++;
 944                 /* restart the frequency calibration interval */
 945                 pps_fbase = *raw_ts;
 946                 hardpps_update_freq(freq_norm);
 947         }
 948
 949         hardpps_update_phase(pts_norm.nsec);
 950
 951         write_sequnlock_irqrestore(&xtime_lock, flags);
 952 }
 953 EXPORT_SYMBOL(hardpps);
 954
 955 #endif  /* CONFIG_NTP_PPS */
 956
 957 static int __init ntp_tick_adj_setup(char *str)
 958 {
 959         ntp_tick_adj = simple_strtol(str, NULL, 0);
 960         ntp_tick_adj <<= NTP_SCALE_SHIFT;
 961
 962         return 1;
 963 }
 964
 965 __setup("ntp_tick_adj=", ntp_tick_adj_setup);
 966
 967 void __init ntp_init(void)
 968 {
 969         ntp_clear();
 970         hrtimer_init(&leap_timer, CLOCK_REALTIME, HRTIMER_MODE_ABS);
 971         leap_timer.function = ntp_leap_second;
 972 }