linux/kernel/time/ntp.c
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   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
  22/*
  23 * NTP timekeeping variables:
  24 */
  25
  26DEFINE_RAW_SPINLOCK(ntp_lock);
  27
  28
  29/* USER_HZ period (usecs): */
  30unsigned long                   tick_usec = TICK_USEC;
  31
  32/* SHIFTED_HZ period (nsecs): */
  33unsigned long                   tick_nsec;
  34
  35static u64                      tick_length;
  36static u64                      tick_length_base;
  37
  38#define MAX_TICKADJ             500LL           /* usecs */
  39#define MAX_TICKADJ_SCALED \
  40        (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ)
  41
  42/*
  43 * phase-lock loop variables
  44 */
  45
  46/*
  47 * clock synchronization status
  48 *
  49 * (TIME_ERROR prevents overwriting the CMOS clock)
  50 */
  51static int                      time_state = TIME_OK;
  52
  53/* clock status bits:                                                   */
  54static int                      time_status = STA_UNSYNC;
  55
  56/* TAI offset (secs):                                                   */
  57static long                     time_tai;
  58
  59/* time adjustment (nsecs):                                             */
  60static s64                      time_offset;
  61
  62/* pll time constant:                                                   */
  63static long                     time_constant = 2;
  64
  65/* maximum error (usecs):                                               */
  66static long                     time_maxerror = NTP_PHASE_LIMIT;
  67
  68/* estimated error (usecs):                                             */
  69static long                     time_esterror = NTP_PHASE_LIMIT;
  70
  71/* frequency offset (scaled nsecs/secs):                                */
  72static s64                      time_freq;
  73
  74/* time at last adjustment (secs):                                      */
  75static long                     time_reftime;
  76
  77static long                     time_adjust;
  78
  79/* constant (boot-param configurable) NTP tick adjustment (upscaled)    */
  80static s64                      ntp_tick_adj;
  81
  82#ifdef CONFIG_NTP_PPS
  83
  84/*
  85 * The following variables are used when a pulse-per-second (PPS) signal
  86 * is available. They establish the engineering parameters of the clock
  87 * discipline loop when controlled by the PPS signal.
  88 */
  89#define PPS_VALID       10      /* PPS signal watchdog max (s) */
  90#define PPS_POPCORN     4       /* popcorn spike threshold (shift) */
  91#define PPS_INTMIN      2       /* min freq interval (s) (shift) */
  92#define PPS_INTMAX      8       /* max freq interval (s) (shift) */
  93#define PPS_INTCOUNT    4       /* number of consecutive good intervals to
  94                                   increase pps_shift or consecutive bad
  95                                   intervals to decrease it */
  96#define PPS_MAXWANDER   100000  /* max PPS freq wander (ns/s) */
  97
  98static int pps_valid;           /* signal watchdog counter */
  99static long pps_tf[3];          /* phase median filter */
 100static long pps_jitter;         /* current jitter (ns) */
 101static struct timespec pps_fbase; /* beginning of the last freq interval */
 102static int pps_shift;           /* current interval duration (s) (shift) */
 103static int pps_intcnt;          /* interval counter */
 104static s64 pps_freq;            /* frequency offset (scaled ns/s) */
 105static long pps_stabil;         /* current stability (scaled ns/s) */
 106
 107/*
 108 * PPS signal quality monitors
 109 */
 110static long pps_calcnt;         /* calibration intervals */
 111static long pps_jitcnt;         /* jitter limit exceeded */
 112static long pps_stbcnt;         /* stability limit exceeded */
 113static long pps_errcnt;         /* calibration errors */
 114
 115
 116/* PPS kernel consumer compensates the whole phase error immediately.
 117 * Otherwise, reduce the offset by a fixed factor times the time constant.
 118 */
 119static inline s64 ntp_offset_chunk(s64 offset)
 120{
 121        if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)
 122                return offset;
 123        else
 124                return shift_right(offset, SHIFT_PLL + time_constant);
 125}
 126
 127static inline void pps_reset_freq_interval(void)
 128{
 129        /* the PPS calibration interval may end
 130           surprisingly early */
 131        pps_shift = PPS_INTMIN;
 132        pps_intcnt = 0;
 133}
 134
 135/**
 136 * pps_clear - Clears the PPS state variables
 137 *
 138 * Must be called while holding a write on the ntp_lock
 139 */
 140static inline void pps_clear(void)
 141{
 142        pps_reset_freq_interval();
 143        pps_tf[0] = 0;
 144        pps_tf[1] = 0;
 145        pps_tf[2] = 0;
 146        pps_fbase.tv_sec = pps_fbase.tv_nsec = 0;
 147        pps_freq = 0;
 148}
 149
 150/* Decrease pps_valid to indicate that another second has passed since
 151 * the last PPS signal. When it reaches 0, indicate that PPS signal is
 152 * missing.
 153 *
 154 * Must be called while holding a write on the ntp_lock
 155 */
 156static inline void pps_dec_valid(void)
 157{
 158        if (pps_valid > 0)
 159                pps_valid--;
 160        else {
 161                time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER |
 162                                 STA_PPSWANDER | STA_PPSERROR);
 163                pps_clear();
 164        }
 165}
 166
 167static inline void pps_set_freq(s64 freq)
 168{
 169        pps_freq = freq;
 170}
 171
 172static inline int is_error_status(int status)
 173{
 174        return (time_status & (STA_UNSYNC|STA_CLOCKERR))
 175                /* PPS signal lost when either PPS time or
 176                 * PPS frequency synchronization requested
 177                 */
 178                || ((time_status & (STA_PPSFREQ|STA_PPSTIME))
 179                        && !(time_status & STA_PPSSIGNAL))
 180                /* PPS jitter exceeded when
 181                 * PPS time synchronization requested */
 182                || ((time_status & (STA_PPSTIME|STA_PPSJITTER))
 183                        == (STA_PPSTIME|STA_PPSJITTER))
 184                /* PPS wander exceeded or calibration error when
 185                 * PPS frequency synchronization requested
 186                 */
 187                || ((time_status & STA_PPSFREQ)
 188                        && (time_status & (STA_PPSWANDER|STA_PPSERROR)));
 189}
 190
 191static inline void pps_fill_timex(struct timex *txc)
 192{
 193        txc->ppsfreq       = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) *
 194                                         PPM_SCALE_INV, NTP_SCALE_SHIFT);
 195        txc->jitter        = pps_jitter;
 196        if (!(time_status & STA_NANO))
 197                txc->jitter /= NSEC_PER_USEC;
 198        txc->shift         = pps_shift;
 199        txc->stabil        = pps_stabil;
 200        txc->jitcnt        = pps_jitcnt;
 201        txc->calcnt        = pps_calcnt;
 202        txc->errcnt        = pps_errcnt;
 203        txc->stbcnt        = pps_stbcnt;
 204}
 205
 206#else /* !CONFIG_NTP_PPS */
 207
 208static inline s64 ntp_offset_chunk(s64 offset)
 209{
 210        return shift_right(offset, SHIFT_PLL + time_constant);
 211}
 212
 213static inline void pps_reset_freq_interval(void) {}
 214static inline void pps_clear(void) {}
 215static inline void pps_dec_valid(void) {}
 216static inline void pps_set_freq(s64 freq) {}
 217
 218static inline int is_error_status(int status)
 219{
 220        return status & (STA_UNSYNC|STA_CLOCKERR);
 221}
 222
 223static inline void pps_fill_timex(struct timex *txc)
 224{
 225        /* PPS is not implemented, so these are zero */
 226        txc->ppsfreq       = 0;
 227        txc->jitter        = 0;
 228        txc->shift         = 0;
 229        txc->stabil        = 0;
 230        txc->jitcnt        = 0;
 231        txc->calcnt        = 0;
 232        txc->errcnt        = 0;
 233        txc->stbcnt        = 0;
 234}
 235
 236#endif /* CONFIG_NTP_PPS */
 237
 238
 239/**
 240 * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 241 *
 242 */
 243static inline int ntp_synced(void)
 244{
 245        return !(time_status & STA_UNSYNC);
 246}
 247
 248
 249/*
 250 * NTP methods:
 251 */
 252
 253/*
 254 * Update (tick_length, tick_length_base, tick_nsec), based
 255 * on (tick_usec, ntp_tick_adj, time_freq):
 256 */
 257static void ntp_update_frequency(void)
 258{
 259        u64 second_length;
 260        u64 new_base;
 261
 262        second_length            = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ)
 263                                                << NTP_SCALE_SHIFT;
 264
 265        second_length           += ntp_tick_adj;
 266        second_length           += time_freq;
 267
 268        tick_nsec                = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT;
 269        new_base                 = div_u64(second_length, NTP_INTERVAL_FREQ);
 270
 271        /*
 272         * Don't wait for the next second_overflow, apply
 273         * the change to the tick length immediately:
 274         */
 275        tick_length             += new_base - tick_length_base;
 276        tick_length_base         = new_base;
 277}
 278
 279static inline s64 ntp_update_offset_fll(s64 offset64, long secs)
 280{
 281        time_status &= ~STA_MODE;
 282
 283        if (secs < MINSEC)
 284                return 0;
 285
 286        if (!(time_status & STA_FLL) && (secs <= MAXSEC))
 287                return 0;
 288
 289        time_status |= STA_MODE;
 290
 291        return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs);
 292}
 293
 294static void ntp_update_offset(long offset)
 295{
 296        s64 freq_adj;
 297        s64 offset64;
 298        long secs;
 299
 300        if (!(time_status & STA_PLL))
 301                return;
 302
 303        if (!(time_status & STA_NANO))
 304                offset *= NSEC_PER_USEC;
 305
 306        /*
 307         * Scale the phase adjustment and
 308         * clamp to the operating range.
 309         */
 310        offset = min(offset, MAXPHASE);
 311        offset = max(offset, -MAXPHASE);
 312
 313        /*
 314         * Select how the frequency is to be controlled
 315         * and in which mode (PLL or FLL).
 316         */
 317        secs = get_seconds() - time_reftime;
 318        if (unlikely(time_status & STA_FREQHOLD))
 319                secs = 0;
 320
 321        time_reftime = get_seconds();
 322
 323        offset64    = offset;
 324        freq_adj    = ntp_update_offset_fll(offset64, secs);
 325
 326        /*
 327         * Clamp update interval to reduce PLL gain with low
 328         * sampling rate (e.g. intermittent network connection)
 329         * to avoid instability.
 330         */
 331        if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant)))
 332                secs = 1 << (SHIFT_PLL + 1 + time_constant);
 333
 334        freq_adj    += (offset64 * secs) <<
 335                        (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant));
 336
 337        freq_adj    = min(freq_adj + time_freq, MAXFREQ_SCALED);
 338
 339        time_freq   = max(freq_adj, -MAXFREQ_SCALED);
 340
 341        time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ);
 342}
 343
 344/**
 345 * ntp_clear - Clears the NTP state variables
 346 */
 347void ntp_clear(void)
 348{
 349        unsigned long flags;
 350
 351        raw_spin_lock_irqsave(&ntp_lock, flags);
 352
 353        time_adjust     = 0;            /* stop active adjtime() */
 354        time_status     |= STA_UNSYNC;
 355        time_maxerror   = NTP_PHASE_LIMIT;
 356        time_esterror   = NTP_PHASE_LIMIT;
 357
 358        ntp_update_frequency();
 359
 360        tick_length     = tick_length_base;
 361        time_offset     = 0;
 362
 363        /* Clear PPS state variables */
 364        pps_clear();
 365        raw_spin_unlock_irqrestore(&ntp_lock, flags);
 366
 367}
 368
 369
 370u64 ntp_tick_length(void)
 371{
 372        unsigned long flags;
 373        s64 ret;
 374
 375        raw_spin_lock_irqsave(&ntp_lock, flags);
 376        ret = tick_length;
 377        raw_spin_unlock_irqrestore(&ntp_lock, flags);
 378        return ret;
 379}
 380
 381
 382/*
 383 * this routine handles the overflow of the microsecond field
 384 *
 385 * The tricky bits of code to handle the accurate clock support
 386 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame.
 387 * They were originally developed for SUN and DEC kernels.
 388 * All the kudos should go to Dave for this stuff.
 389 *
 390 * Also handles leap second processing, and returns leap offset
 391 */
 392int second_overflow(unsigned long secs)
 393{
 394        s64 delta;
 395        int leap = 0;
 396        unsigned long flags;
 397
 398        raw_spin_lock_irqsave(&ntp_lock, flags);
 399
 400        /*
 401         * Leap second processing. If in leap-insert state at the end of the
 402         * day, the system clock is set back one second; if in leap-delete
 403         * state, the system clock is set ahead one second.
 404         */
 405        switch (time_state) {
 406        case TIME_OK:
 407                if (time_status & STA_INS)
 408                        time_state = TIME_INS;
 409                else if (time_status & STA_DEL)
 410                        time_state = TIME_DEL;
 411                break;
 412        case TIME_INS:
 413                if (!(time_status & STA_INS))
 414                        time_state = TIME_OK;
 415                else if (secs % 86400 == 0) {
 416                        leap = -1;
 417                        time_state = TIME_OOP;
 418                        time_tai++;
 419                        printk(KERN_NOTICE
 420                                "Clock: inserting leap second 23:59:60 UTC\n");
 421                }
 422                break;
 423        case TIME_DEL:
 424                if (!(time_status & STA_DEL))
 425                        time_state = TIME_OK;
 426                else if ((secs + 1) % 86400 == 0) {
 427                        leap = 1;
 428                        time_tai--;
 429                        time_state = TIME_WAIT;
 430                        printk(KERN_NOTICE
 431                                "Clock: deleting leap second 23:59:59 UTC\n");
 432                }
 433                break;
 434        case TIME_OOP:
 435                time_state = TIME_WAIT;
 436                break;
 437
 438        case TIME_WAIT:
 439                if (!(time_status & (STA_INS | STA_DEL)))
 440                        time_state = TIME_OK;
 441                break;
 442        }
 443
 444
 445        /* Bump the maxerror field */
 446        time_maxerror += MAXFREQ / NSEC_PER_USEC;
 447        if (time_maxerror > NTP_PHASE_LIMIT) {
 448                time_maxerror = NTP_PHASE_LIMIT;
 449                time_status |= STA_UNSYNC;
 450        }
 451
 452        /* Compute the phase adjustment for the next second */
 453        tick_length      = tick_length_base;
 454
 455        delta            = ntp_offset_chunk(time_offset);
 456        time_offset     -= delta;
 457        tick_length     += delta;
 458
 459        /* Check PPS signal */
 460        pps_dec_valid();
 461
 462        if (!time_adjust)
 463                goto out;
 464
 465        if (time_adjust > MAX_TICKADJ) {
 466                time_adjust -= MAX_TICKADJ;
 467                tick_length += MAX_TICKADJ_SCALED;
 468                goto out;
 469        }
 470
 471        if (time_adjust < -MAX_TICKADJ) {
 472                time_adjust += MAX_TICKADJ;
 473                tick_length -= MAX_TICKADJ_SCALED;
 474                goto out;
 475        }
 476
 477        tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ)
 478                                                         << NTP_SCALE_SHIFT;
 479        time_adjust = 0;
 480
 481out:
 482        raw_spin_unlock_irqrestore(&ntp_lock, flags);
 483
 484        return leap;
 485}
 486
 487#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC)
 488static void sync_cmos_clock(struct work_struct *work);
 489
 490static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock);
 491
 492static 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                struct timespec adjust = now;
 515
 516                fail = -ENODEV;
 517                if (persistent_clock_is_local)
 518                        adjust.tv_sec -= (sys_tz.tz_minuteswest * 60);
 519#ifdef CONFIG_GENERIC_CMOS_UPDATE
 520                fail = update_persistent_clock(adjust);
 521#endif
 522#ifdef CONFIG_RTC_SYSTOHC
 523                if (fail == -ENODEV)
 524                        fail = rtc_set_ntp_time(adjust);
 525#endif
 526        }
 527
 528        next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2);
 529        if (next.tv_nsec <= 0)
 530                next.tv_nsec += NSEC_PER_SEC;
 531
 532        if (!fail || fail == -ENODEV)
 533                next.tv_sec = 659;
 534        else
 535                next.tv_sec = 0;
 536
 537        if (next.tv_nsec >= NSEC_PER_SEC) {
 538                next.tv_sec++;
 539                next.tv_nsec -= NSEC_PER_SEC;
 540        }
 541        schedule_delayed_work(&sync_cmos_work, timespec_to_jiffies(&next));
 542}
 543
 544static void notify_cmos_timer(void)
 545{
 546        schedule_delayed_work(&sync_cmos_work, 0);
 547}
 548
 549#else
 550static inline void notify_cmos_timer(void) { }
 551#endif
 552
 553
 554/*
 555 * Propagate a new txc->status value into the NTP state:
 556 */
 557static inline void process_adj_status(struct timex *txc, struct timespec *ts)
 558{
 559        if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) {
 560                time_state = TIME_OK;
 561                time_status = STA_UNSYNC;
 562                /* restart PPS frequency calibration */
 563                pps_reset_freq_interval();
 564        }
 565
 566        /*
 567         * If we turn on PLL adjustments then reset the
 568         * reference time to current time.
 569         */
 570        if (!(time_status & STA_PLL) && (txc->status & STA_PLL))
 571                time_reftime = get_seconds();
 572
 573        /* only set allowed bits */
 574        time_status &= STA_RONLY;
 575        time_status |= txc->status & ~STA_RONLY;
 576}
 577
 578/*
 579 * Called with ntp_lock held, so we can access and modify
 580 * all the global NTP state:
 581 */
 582static inline void process_adjtimex_modes(struct timex *txc, struct timespec *ts)
 583{
 584        if (txc->modes & ADJ_STATUS)
 585                process_adj_status(txc, ts);
 586
 587        if (txc->modes & ADJ_NANO)
 588                time_status |= STA_NANO;
 589
 590        if (txc->modes & ADJ_MICRO)
 591                time_status &= ~STA_NANO;
 592
 593        if (txc->modes & ADJ_FREQUENCY) {
 594                time_freq = txc->freq * PPM_SCALE;
 595                time_freq = min(time_freq, MAXFREQ_SCALED);
 596                time_freq = max(time_freq, -MAXFREQ_SCALED);
 597                /* update pps_freq */
 598                pps_set_freq(time_freq);
 599        }
 600
 601        if (txc->modes & ADJ_MAXERROR)
 602                time_maxerror = txc->maxerror;
 603
 604        if (txc->modes & ADJ_ESTERROR)
 605                time_esterror = txc->esterror;
 606
 607        if (txc->modes & ADJ_TIMECONST) {
 608                time_constant = txc->constant;
 609                if (!(time_status & STA_NANO))
 610                        time_constant += 4;
 611                time_constant = min(time_constant, (long)MAXTC);
 612                time_constant = max(time_constant, 0l);
 613        }
 614
 615        if (txc->modes & ADJ_TAI && txc->constant > 0)
 616                time_tai = txc->constant;
 617
 618        if (txc->modes & ADJ_OFFSET)
 619                ntp_update_offset(txc->offset);
 620
 621        if (txc->modes & ADJ_TICK)
 622                tick_usec = txc->tick;
 623
 624        if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET))
 625                ntp_update_frequency();
 626}
 627
 628/*
 629 * adjtimex mainly allows reading (and writing, if superuser) of
 630 * kernel time-keeping variables. used by xntpd.
 631 */
 632int do_adjtimex(struct timex *txc)
 633{
 634        struct timespec ts;
 635        int result;
 636
 637        /* Validate the data before disabling interrupts */
 638        if (txc->modes & ADJ_ADJTIME) {
 639                /* singleshot must not be used with any other mode bits */
 640                if (!(txc->modes & ADJ_OFFSET_SINGLESHOT))
 641                        return -EINVAL;
 642                if (!(txc->modes & ADJ_OFFSET_READONLY) &&
 643                    !capable(CAP_SYS_TIME))
 644                        return -EPERM;
 645        } else {
 646                /* In order to modify anything, you gotta be super-user! */
 647                 if (txc->modes && !capable(CAP_SYS_TIME))
 648                        return -EPERM;
 649
 650                /*
 651                 * if the quartz is off by more than 10% then
 652                 * something is VERY wrong!
 653                 */
 654                if (txc->modes & ADJ_TICK &&
 655                    (txc->tick <  900000/USER_HZ ||
 656                     txc->tick > 1100000/USER_HZ))
 657                        return -EINVAL;
 658        }
 659
 660        if (txc->modes & ADJ_SETOFFSET) {
 661                struct timespec delta;
 662                delta.tv_sec  = txc->time.tv_sec;
 663                delta.tv_nsec = txc->time.tv_usec;
 664                if (!capable(CAP_SYS_TIME))
 665                        return -EPERM;
 666                if (!(txc->modes & ADJ_NANO))
 667                        delta.tv_nsec *= 1000;
 668                result = timekeeping_inject_offset(&delta);
 669                if (result)
 670                        return result;
 671        }
 672
 673        getnstimeofday(&ts);
 674
 675        raw_spin_lock_irq(&ntp_lock);
 676
 677        if (txc->modes & ADJ_ADJTIME) {
 678                long save_adjust = time_adjust;
 679
 680                if (!(txc->modes & ADJ_OFFSET_READONLY)) {
 681                        /* adjtime() is independent from ntp_adjtime() */
 682                        time_adjust = txc->offset;
 683                        ntp_update_frequency();
 684                }
 685                txc->offset = save_adjust;
 686        } else {
 687
 688                /* If there are input parameters, then process them: */
 689                if (txc->modes)
 690                        process_adjtimex_modes(txc, &ts);
 691
 692                txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ,
 693                                  NTP_SCALE_SHIFT);
 694                if (!(time_status & STA_NANO))
 695                        txc->offset /= NSEC_PER_USEC;
 696        }
 697
 698        result = time_state;    /* mostly `TIME_OK' */
 699        /* check for errors */
 700        if (is_error_status(time_status))
 701                result = TIME_ERROR;
 702
 703        txc->freq          = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) *
 704                                         PPM_SCALE_INV, NTP_SCALE_SHIFT);
 705        txc->maxerror      = time_maxerror;
 706        txc->esterror      = time_esterror;
 707        txc->status        = time_status;
 708        txc->constant      = time_constant;
 709        txc->precision     = 1;
 710        txc->tolerance     = MAXFREQ_SCALED / PPM_SCALE;
 711        txc->tick          = tick_usec;
 712        txc->tai           = time_tai;
 713
 714        /* fill PPS status fields */
 715        pps_fill_timex(txc);
 716
 717        raw_spin_unlock_irq(&ntp_lock);
 718
 719        txc->time.tv_sec = ts.tv_sec;
 720        txc->time.tv_usec = ts.tv_nsec;
 721        if (!(time_status & STA_NANO))
 722                txc->time.tv_usec /= NSEC_PER_USEC;
 723
 724        notify_cmos_timer();
 725
 726        return result;
 727}
 728
 729#ifdef  CONFIG_NTP_PPS
 730
 731/* actually struct pps_normtime is good old struct timespec, but it is
 732 * semantically different (and it is the reason why it was invented):
 733 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ]
 734 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */
 735struct pps_normtime {
 736        __kernel_time_t sec;    /* seconds */
 737        long            nsec;   /* nanoseconds */
 738};
 739
 740/* normalize the timestamp so that nsec is in the
 741   ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */
 742static inline struct pps_normtime pps_normalize_ts(struct timespec ts)
 743{
 744        struct pps_normtime norm = {
 745                .sec = ts.tv_sec,
 746                .nsec = ts.tv_nsec
 747        };
 748
 749        if (norm.nsec > (NSEC_PER_SEC >> 1)) {
 750                norm.nsec -= NSEC_PER_SEC;
 751                norm.sec++;
 752        }
 753
 754        return norm;
 755}
 756
 757/* get current phase correction and jitter */
 758static inline long pps_phase_filter_get(long *jitter)
 759{
 760        *jitter = pps_tf[0] - pps_tf[1];
 761        if (*jitter < 0)
 762                *jitter = -*jitter;
 763
 764        /* TODO: test various filters */
 765        return pps_tf[0];
 766}
 767
 768/* add the sample to the phase filter */
 769static inline void pps_phase_filter_add(long err)
 770{
 771        pps_tf[2] = pps_tf[1];
 772        pps_tf[1] = pps_tf[0];
 773        pps_tf[0] = err;
 774}
 775
 776/* decrease frequency calibration interval length.
 777 * It is halved after four consecutive unstable intervals.
 778 */
 779static inline void pps_dec_freq_interval(void)
 780{
 781        if (--pps_intcnt <= -PPS_INTCOUNT) {
 782                pps_intcnt = -PPS_INTCOUNT;
 783                if (pps_shift > PPS_INTMIN) {
 784                        pps_shift--;
 785                        pps_intcnt = 0;
 786                }
 787        }
 788}
 789
 790/* increase frequency calibration interval length.
 791 * It is doubled after four consecutive stable intervals.
 792 */
 793static inline void pps_inc_freq_interval(void)
 794{
 795        if (++pps_intcnt >= PPS_INTCOUNT) {
 796                pps_intcnt = PPS_INTCOUNT;
 797                if (pps_shift < PPS_INTMAX) {
 798                        pps_shift++;
 799                        pps_intcnt = 0;
 800                }
 801        }
 802}
 803
 804/* update clock frequency based on MONOTONIC_RAW clock PPS signal
 805 * timestamps
 806 *
 807 * At the end of the calibration interval the difference between the
 808 * first and last MONOTONIC_RAW clock timestamps divided by the length
 809 * of the interval becomes the frequency update. If the interval was
 810 * too long, the data are discarded.
 811 * Returns the difference between old and new frequency values.
 812 */
 813static long hardpps_update_freq(struct pps_normtime freq_norm)
 814{
 815        long delta, delta_mod;
 816        s64 ftemp;
 817
 818        /* check if the frequency interval was too long */
 819        if (freq_norm.sec > (2 << pps_shift)) {
 820                time_status |= STA_PPSERROR;
 821                pps_errcnt++;
 822                pps_dec_freq_interval();
 823                pr_err("hardpps: PPSERROR: interval too long - %ld s\n",
 824                                freq_norm.sec);
 825                return 0;
 826        }
 827
 828        /* here the raw frequency offset and wander (stability) is
 829         * calculated. If the wander is less than the wander threshold
 830         * the interval is increased; otherwise it is decreased.
 831         */
 832        ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT,
 833                        freq_norm.sec);
 834        delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT);
 835        pps_freq = ftemp;
 836        if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) {
 837                pr_warning("hardpps: PPSWANDER: change=%ld\n", delta);
 838                time_status |= STA_PPSWANDER;
 839                pps_stbcnt++;
 840                pps_dec_freq_interval();
 841        } else {        /* good sample */
 842                pps_inc_freq_interval();
 843        }
 844
 845        /* the stability metric is calculated as the average of recent
 846         * frequency changes, but is used only for performance
 847         * monitoring
 848         */
 849        delta_mod = delta;
 850        if (delta_mod < 0)
 851                delta_mod = -delta_mod;
 852        pps_stabil += (div_s64(((s64)delta_mod) <<
 853                                (NTP_SCALE_SHIFT - SHIFT_USEC),
 854                                NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN;
 855
 856        /* if enabled, the system clock frequency is updated */
 857        if ((time_status & STA_PPSFREQ) != 0 &&
 858            (time_status & STA_FREQHOLD) == 0) {
 859                time_freq = pps_freq;
 860                ntp_update_frequency();
 861        }
 862
 863        return delta;
 864}
 865
 866/* correct REALTIME clock phase error against PPS signal */
 867static void hardpps_update_phase(long error)
 868{
 869        long correction = -error;
 870        long jitter;
 871
 872        /* add the sample to the median filter */
 873        pps_phase_filter_add(correction);
 874        correction = pps_phase_filter_get(&jitter);
 875
 876        /* Nominal jitter is due to PPS signal noise. If it exceeds the
 877         * threshold, the sample is discarded; otherwise, if so enabled,
 878         * the time offset is updated.
 879         */
 880        if (jitter > (pps_jitter << PPS_POPCORN)) {
 881                pr_warning("hardpps: PPSJITTER: jitter=%ld, limit=%ld\n",
 882                       jitter, (pps_jitter << PPS_POPCORN));
 883                time_status |= STA_PPSJITTER;
 884                pps_jitcnt++;
 885        } else if (time_status & STA_PPSTIME) {
 886                /* correct the time using the phase offset */
 887                time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT,
 888                                NTP_INTERVAL_FREQ);
 889                /* cancel running adjtime() */
 890                time_adjust = 0;
 891        }
 892        /* update jitter */
 893        pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN;
 894}
 895
 896/*
 897 * hardpps() - discipline CPU clock oscillator to external PPS signal
 898 *
 899 * This routine is called at each PPS signal arrival in order to
 900 * discipline the CPU clock oscillator to the PPS signal. It takes two
 901 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former
 902 * is used to correct clock phase error and the latter is used to
 903 * correct the frequency.
 904 *
 905 * This code is based on David Mills's reference nanokernel
 906 * implementation. It was mostly rewritten but keeps the same idea.
 907 */
 908void hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts)
 909{
 910        struct pps_normtime pts_norm, freq_norm;
 911        unsigned long flags;
 912
 913        pts_norm = pps_normalize_ts(*phase_ts);
 914
 915        raw_spin_lock_irqsave(&ntp_lock, flags);
 916
 917        /* clear the error bits, they will be set again if needed */
 918        time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR);
 919
 920        /* indicate signal presence */
 921        time_status |= STA_PPSSIGNAL;
 922        pps_valid = PPS_VALID;
 923
 924        /* when called for the first time,
 925         * just start the frequency interval */
 926        if (unlikely(pps_fbase.tv_sec == 0)) {
 927                pps_fbase = *raw_ts;
 928                raw_spin_unlock_irqrestore(&ntp_lock, flags);
 929                return;
 930        }
 931
 932        /* ok, now we have a base for frequency calculation */
 933        freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase));
 934
 935        /* check that the signal is in the range
 936         * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */
 937        if ((freq_norm.sec == 0) ||
 938                        (freq_norm.nsec > MAXFREQ * freq_norm.sec) ||
 939                        (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) {
 940                time_status |= STA_PPSJITTER;
 941                /* restart the frequency calibration interval */
 942                pps_fbase = *raw_ts;
 943                raw_spin_unlock_irqrestore(&ntp_lock, flags);
 944                pr_err("hardpps: PPSJITTER: bad pulse\n");
 945                return;
 946        }
 947
 948        /* signal is ok */
 949
 950        /* check if the current frequency interval is finished */
 951        if (freq_norm.sec >= (1 << pps_shift)) {
 952                pps_calcnt++;
 953                /* restart the frequency calibration interval */
 954                pps_fbase = *raw_ts;
 955                hardpps_update_freq(freq_norm);
 956        }
 957
 958        hardpps_update_phase(pts_norm.nsec);
 959
 960        raw_spin_unlock_irqrestore(&ntp_lock, flags);
 961}
 962EXPORT_SYMBOL(hardpps);
 963
 964#endif  /* CONFIG_NTP_PPS */
 965
 966static int __init ntp_tick_adj_setup(char *str)
 967{
 968        ntp_tick_adj = simple_strtol(str, NULL, 0);
 969        ntp_tick_adj <<= NTP_SCALE_SHIFT;
 970
 971        return 1;
 972}
 973
 974__setup("ntp_tick_adj=", ntp_tick_adj_setup);
 975
 976void __init ntp_init(void)
 977{
 978        ntp_clear();
 979}
 980
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