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 "ntp_internal.h" 21 22/* 23 * NTP timekeeping variables: 24 * 25 * Note: All of the NTP state is protected by the timekeeping locks. 26 */ 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/* time adjustment (nsecs): */ 57static s64 time_offset; 58 59/* pll time constant: */ 60static long time_constant = 2; 61 62/* maximum error (usecs): */ 63static long time_maxerror = NTP_PHASE_LIMIT; 64 65/* estimated error (usecs): */ 66static long time_esterror = NTP_PHASE_LIMIT; 67 68/* frequency offset (scaled nsecs/secs): */ 69static s64 time_freq; 70 71/* time at last adjustment (secs): */ 72static long time_reftime; 73 74static long time_adjust; 75 76/* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 77static s64 ntp_tick_adj; 78 79#ifdef CONFIG_NTP_PPS 80 81/* 82 * The following variables are used when a pulse-per-second (PPS) signal 83 * is available. They establish the engineering parameters of the clock 84 * discipline loop when controlled by the PPS signal. 85 */ 86#define PPS_VALID 10 /* PPS signal watchdog max (s) */ 87#define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 88#define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 89#define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 90#define PPS_INTCOUNT 4 /* number of consecutive good intervals to 91 increase pps_shift or consecutive bad 92 intervals to decrease it */ 93#define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 94 95static int pps_valid; /* signal watchdog counter */ 96static long pps_tf[3]; /* phase median filter */ 97static long pps_jitter; /* current jitter (ns) */ 98static struct timespec pps_fbase; /* beginning of the last freq interval */ 99static int pps_shift; /* current interval duration (s) (shift) */ 100static int pps_intcnt; /* interval counter */ 101static s64 pps_freq; /* frequency offset (scaled ns/s) */ 102static long pps_stabil; /* current stability (scaled ns/s) */ 103 104/* 105 * PPS signal quality monitors 106 */ 107static long pps_calcnt; /* calibration intervals */ 108static long pps_jitcnt; /* jitter limit exceeded */ 109static long pps_stbcnt; /* stability limit exceeded */ 110static long pps_errcnt; /* calibration errors */ 111 112 113/* PPS kernel consumer compensates the whole phase error immediately. 114 * Otherwise, reduce the offset by a fixed factor times the time constant. 115 */ 116static inline s64 ntp_offset_chunk(s64 offset) 117{ 118 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 119 return offset; 120 else 121 return shift_right(offset, SHIFT_PLL + time_constant); 122} 123 124static inline void pps_reset_freq_interval(void) 125{ 126 /* the PPS calibration interval may end 127 surprisingly early */ 128 pps_shift = PPS_INTMIN; 129 pps_intcnt = 0; 130} 131 132/** 133 * pps_clear - Clears the PPS state variables 134 */ 135static inline void pps_clear(void) 136{ 137 pps_reset_freq_interval(); 138 pps_tf[0] = 0; 139 pps_tf[1] = 0; 140 pps_tf[2] = 0; 141 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 142 pps_freq = 0; 143} 144 145/* Decrease pps_valid to indicate that another second has passed since 146 * the last PPS signal. When it reaches 0, indicate that PPS signal is 147 * missing. 148 */ 149static inline void pps_dec_valid(void) 150{ 151 if (pps_valid > 0) 152 pps_valid--; 153 else { 154 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 155 STA_PPSWANDER | STA_PPSERROR); 156 pps_clear(); 157 } 158} 159 160static inline void pps_set_freq(s64 freq) 161{ 162 pps_freq = freq; 163} 164 165static inline int is_error_status(int status) 166{ 167 return (status & (STA_UNSYNC|STA_CLOCKERR)) 168 /* PPS signal lost when either PPS time or 169 * PPS frequency synchronization requested 170 */ 171 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 172 && !(status & STA_PPSSIGNAL)) 173 /* PPS jitter exceeded when 174 * PPS time synchronization requested */ 175 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 176 == (STA_PPSTIME|STA_PPSJITTER)) 177 /* PPS wander exceeded or calibration error when 178 * PPS frequency synchronization requested 179 */ 180 || ((status & STA_PPSFREQ) 181 && (status & (STA_PPSWANDER|STA_PPSERROR))); 182} 183 184static inline void pps_fill_timex(struct timex *txc) 185{ 186 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 187 PPM_SCALE_INV, NTP_SCALE_SHIFT); 188 txc->jitter = pps_jitter; 189 if (!(time_status & STA_NANO)) 190 txc->jitter /= NSEC_PER_USEC; 191 txc->shift = pps_shift; 192 txc->stabil = pps_stabil; 193 txc->jitcnt = pps_jitcnt; 194 txc->calcnt = pps_calcnt; 195 txc->errcnt = pps_errcnt; 196 txc->stbcnt = pps_stbcnt; 197} 198 199#else /* !CONFIG_NTP_PPS */ 200 201static inline s64 ntp_offset_chunk(s64 offset) 202{ 203 return shift_right(offset, SHIFT_PLL + time_constant); 204} 205 206static inline void pps_reset_freq_interval(void) {} 207static inline void pps_clear(void) {} 208static inline void pps_dec_valid(void) {} 209static inline void pps_set_freq(s64 freq) {} 210 211static inline int is_error_status(int status) 212{ 213 return status & (STA_UNSYNC|STA_CLOCKERR); 214} 215 216static inline void pps_fill_timex(struct timex *txc) 217{ 218 /* PPS is not implemented, so these are zero */ 219 txc->ppsfreq = 0; 220 txc->jitter = 0; 221 txc->shift = 0; 222 txc->stabil = 0; 223 txc->jitcnt = 0; 224 txc->calcnt = 0; 225 txc->errcnt = 0; 226 txc->stbcnt = 0; 227} 228 229#endif /* CONFIG_NTP_PPS */ 230 231 232/** 233 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 234 * 235 */ 236static inline int ntp_synced(void) 237{ 238 return !(time_status & STA_UNSYNC); 239} 240 241 242/* 243 * NTP methods: 244 */ 245 246/* 247 * Update (tick_length, tick_length_base, tick_nsec), based 248 * on (tick_usec, ntp_tick_adj, time_freq): 249 */ 250static void ntp_update_frequency(void) 251{ 252 u64 second_length; 253 u64 new_base; 254 255 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 256 << NTP_SCALE_SHIFT; 257 258 second_length += ntp_tick_adj; 259 second_length += time_freq; 260 261 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 262 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 263 264 /* 265 * Don't wait for the next second_overflow, apply 266 * the change to the tick length immediately: 267 */ 268 tick_length += new_base - tick_length_base; 269 tick_length_base = new_base; 270} 271 272static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 273{ 274 time_status &= ~STA_MODE; 275 276 if (secs < MINSEC) 277 return 0; 278 279 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 280 return 0; 281 282 time_status |= STA_MODE; 283 284 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 285} 286 287static void ntp_update_offset(long offset) 288{ 289 s64 freq_adj; 290 s64 offset64; 291 long secs; 292 293 if (!(time_status & STA_PLL)) 294 return; 295 296 if (!(time_status & STA_NANO)) 297 offset *= NSEC_PER_USEC; 298 299 /* 300 * Scale the phase adjustment and 301 * clamp to the operating range. 302 */ 303 offset = min(offset, MAXPHASE); 304 offset = max(offset, -MAXPHASE); 305 306 /* 307 * Select how the frequency is to be controlled 308 * and in which mode (PLL or FLL). 309 */ 310 secs = get_seconds() - time_reftime; 311 if (unlikely(time_status & STA_FREQHOLD)) 312 secs = 0; 313 314 time_reftime = get_seconds(); 315 316 offset64 = offset; 317 freq_adj = ntp_update_offset_fll(offset64, secs); 318 319 /* 320 * Clamp update interval to reduce PLL gain with low 321 * sampling rate (e.g. intermittent network connection) 322 * to avoid instability. 323 */ 324 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 325 secs = 1 << (SHIFT_PLL + 1 + time_constant); 326 327 freq_adj += (offset64 * secs) << 328 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 329 330 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 331 332 time_freq = max(freq_adj, -MAXFREQ_SCALED); 333 334 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 335} 336 337/** 338 * ntp_clear - Clears the NTP state variables 339 */ 340void ntp_clear(void) 341{ 342 time_adjust = 0; /* stop active adjtime() */ 343 time_status |= STA_UNSYNC; 344 time_maxerror = NTP_PHASE_LIMIT; 345 time_esterror = NTP_PHASE_LIMIT; 346 347 ntp_update_frequency(); 348 349 tick_length = tick_length_base; 350 time_offset = 0; 351 352 /* Clear PPS state variables */ 353 pps_clear(); 354} 355 356 357u64 ntp_tick_length(void) 358{ 359 return tick_length; 360} 361 362 363/* 364 * this routine handles the overflow of the microsecond field 365 * 366 * The tricky bits of code to handle the accurate clock support 367 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 368 * They were originally developed for SUN and DEC kernels. 369 * All the kudos should go to Dave for this stuff. 370 * 371 * Also handles leap second processing, and returns leap offset 372 */ 373int second_overflow(unsigned long secs) 374{ 375 s64 delta; 376 int leap = 0; 377 378 /* 379 * Leap second processing. If in leap-insert state at the end of the 380 * day, the system clock is set back one second; if in leap-delete 381 * state, the system clock is set ahead one second. 382 */ 383 switch (time_state) { 384 case TIME_OK: 385 if (time_status & STA_INS) 386 time_state = TIME_INS; 387 else if (time_status & STA_DEL) 388 time_state = TIME_DEL; 389 break; 390 case TIME_INS: 391 if (!(time_status & STA_INS)) 392 time_state = TIME_OK; 393 else if (secs % 86400 == 0) { 394 leap = -1; 395 time_state = TIME_OOP; 396 printk(KERN_NOTICE 397 "Clock: inserting leap second 23:59:60 UTC\n"); 398 } 399 break; 400 case TIME_DEL: 401 if (!(time_status & STA_DEL)) 402 time_state = TIME_OK; 403 else if ((secs + 1) % 86400 == 0) { 404 leap = 1; 405 time_state = TIME_WAIT; 406 printk(KERN_NOTICE 407 "Clock: deleting leap second 23:59:59 UTC\n"); 408 } 409 break; 410 case TIME_OOP: 411 time_state = TIME_WAIT; 412 break; 413 414 case TIME_WAIT: 415 if (!(time_status & (STA_INS | STA_DEL))) 416 time_state = TIME_OK; 417 break; 418 } 419 420 421 /* Bump the maxerror field */ 422 time_maxerror += MAXFREQ / NSEC_PER_USEC; 423 if (time_maxerror > NTP_PHASE_LIMIT) { 424 time_maxerror = NTP_PHASE_LIMIT; 425 time_status |= STA_UNSYNC; 426 } 427 428 /* Compute the phase adjustment for the next second */ 429 tick_length = tick_length_base; 430 431 delta = ntp_offset_chunk(time_offset); 432 time_offset -= delta; 433 tick_length += delta; 434 435 /* Check PPS signal */ 436 pps_dec_valid(); 437 438 if (!time_adjust) 439 goto out; 440 441 if (time_adjust > MAX_TICKADJ) { 442 time_adjust -= MAX_TICKADJ; 443 tick_length += MAX_TICKADJ_SCALED; 444 goto out; 445 } 446 447 if (time_adjust < -MAX_TICKADJ) { 448 time_adjust += MAX_TICKADJ; 449 tick_length -= MAX_TICKADJ_SCALED; 450 goto out; 451 } 452 453 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) 454 << NTP_SCALE_SHIFT; 455 time_adjust = 0; 456 457out: 458 return leap; 459} 460 461#ifdef CONFIG_GENERIC_CMOS_UPDATE 462int __weak update_persistent_clock64(struct timespec64 now64) 463{ 464 struct timespec now; 465 466 now = timespec64_to_timespec(now64); 467 return update_persistent_clock(now); 468} 469#endif 470 471#if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) 472static void sync_cmos_clock(struct work_struct *work); 473 474static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); 475 476static void sync_cmos_clock(struct work_struct *work) 477{ 478 struct timespec64 now; 479 struct timespec next; 480 int fail = 1; 481 482 /* 483 * If we have an externally synchronized Linux clock, then update 484 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be 485 * called as close as possible to 500 ms before the new second starts. 486 * This code is run on a timer. If the clock is set, that timer 487 * may not expire at the correct time. Thus, we adjust... 488 * We want the clock to be within a couple of ticks from the target. 489 */ 490 if (!ntp_synced()) { 491 /* 492 * Not synced, exit, do not restart a timer (if one is 493 * running, let it run out). 494 */ 495 return; 496 } 497 498 getnstimeofday64(&now); 499 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) { 500 struct timespec64 adjust = now; 501 502 fail = -ENODEV; 503 if (persistent_clock_is_local) 504 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 505#ifdef CONFIG_GENERIC_CMOS_UPDATE 506 fail = update_persistent_clock64(adjust); 507#endif 508 509#ifdef CONFIG_RTC_SYSTOHC 510 if (fail == -ENODEV) 511 fail = rtc_set_ntp_time(adjust); 512#endif 513 } 514 515 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); 516 if (next.tv_nsec <= 0) 517 next.tv_nsec += NSEC_PER_SEC; 518 519 if (!fail || fail == -ENODEV) 520 next.tv_sec = 659; 521 else 522 next.tv_sec = 0; 523 524 if (next.tv_nsec >= NSEC_PER_SEC) { 525 next.tv_sec++; 526 next.tv_nsec -= NSEC_PER_SEC; 527 } 528 queue_delayed_work(system_power_efficient_wq, 529 &sync_cmos_work, timespec_to_jiffies(&next)); 530} 531 532void ntp_notify_cmos_timer(void) 533{ 534 queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0); 535} 536 537#else 538void ntp_notify_cmos_timer(void) { } 539#endif 540 541 542/* 543 * Propagate a new txc->status value into the NTP state: 544 */ 545static inline void process_adj_status(struct timex *txc, struct timespec64 *ts) 546{ 547 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 548 time_state = TIME_OK; 549 time_status = STA_UNSYNC; 550 /* restart PPS frequency calibration */ 551 pps_reset_freq_interval(); 552 } 553 554 /* 555 * If we turn on PLL adjustments then reset the 556 * reference time to current time. 557 */ 558 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 559 time_reftime = get_seconds(); 560 561 /* only set allowed bits */ 562 time_status &= STA_RONLY; 563 time_status |= txc->status & ~STA_RONLY; 564} 565 566 567static inline void process_adjtimex_modes(struct timex *txc, 568 struct timespec64 *ts, 569 s32 *time_tai) 570{ 571 if (txc->modes & ADJ_STATUS) 572 process_adj_status(txc, ts); 573 574 if (txc->modes & ADJ_NANO) 575 time_status |= STA_NANO; 576 577 if (txc->modes & ADJ_MICRO) 578 time_status &= ~STA_NANO; 579 580 if (txc->modes & ADJ_FREQUENCY) { 581 time_freq = txc->freq * PPM_SCALE; 582 time_freq = min(time_freq, MAXFREQ_SCALED); 583 time_freq = max(time_freq, -MAXFREQ_SCALED); 584 /* update pps_freq */ 585 pps_set_freq(time_freq); 586 } 587 588 if (txc->modes & ADJ_MAXERROR) 589 time_maxerror = txc->maxerror; 590 591 if (txc->modes & ADJ_ESTERROR) 592 time_esterror = txc->esterror; 593 594 if (txc->modes & ADJ_TIMECONST) { 595 time_constant = txc->constant; 596 if (!(time_status & STA_NANO)) 597 time_constant += 4; 598 time_constant = min(time_constant, (long)MAXTC); 599 time_constant = max(time_constant, 0l); 600 } 601 602 if (txc->modes & ADJ_TAI && txc->constant > 0) 603 *time_tai = txc->constant; 604 605 if (txc->modes & ADJ_OFFSET) 606 ntp_update_offset(txc->offset); 607 608 if (txc->modes & ADJ_TICK) 609 tick_usec = txc->tick; 610 611 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 612 ntp_update_frequency(); 613} 614 615 616 617/** 618 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex 619 */ 620int ntp_validate_timex(struct timex *txc) 621{ 622 if (txc->modes & ADJ_ADJTIME) { 623 /* singleshot must not be used with any other mode bits */ 624 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT)) 625 return -EINVAL; 626 if (!(txc->modes & ADJ_OFFSET_READONLY) && 627 !capable(CAP_SYS_TIME)) 628 return -EPERM; 629 } else { 630 /* In order to modify anything, you gotta be super-user! */ 631 if (txc->modes && !capable(CAP_SYS_TIME)) 632 return -EPERM; 633 /* 634 * if the quartz is off by more than 10% then 635 * something is VERY wrong! 636 */ 637 if (txc->modes & ADJ_TICK && 638 (txc->tick < 900000/USER_HZ || 639 txc->tick > 1100000/USER_HZ)) 640 return -EINVAL; 641 } 642 643 if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME))) 644 return -EPERM; 645 646 /* 647 * Check for potential multiplication overflows that can 648 * only happen on 64-bit systems: 649 */ 650 if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) { 651 if (LLONG_MIN / PPM_SCALE > txc->freq) 652 return -EINVAL; 653 if (LLONG_MAX / PPM_SCALE < txc->freq) 654 return -EINVAL; 655 } 656 657 return 0; 658} 659 660 661/* 662 * adjtimex mainly allows reading (and writing, if superuser) of 663 * kernel time-keeping variables. used by xntpd. 664 */ 665int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai) 666{ 667 int result; 668 669 if (txc->modes & ADJ_ADJTIME) { 670 long save_adjust = time_adjust; 671 672 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 673 /* adjtime() is independent from ntp_adjtime() */ 674 time_adjust = txc->offset; 675 ntp_update_frequency(); 676 } 677 txc->offset = save_adjust; 678 } else { 679 680 /* If there are input parameters, then process them: */ 681 if (txc->modes) 682 process_adjtimex_modes(txc, ts, time_tai); 683 684 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 685 NTP_SCALE_SHIFT); 686 if (!(time_status & STA_NANO)) 687 txc->offset /= NSEC_PER_USEC; 688 } 689 690 result = time_state; /* mostly `TIME_OK' */ 691 /* check for errors */ 692 if (is_error_status(time_status)) 693 result = TIME_ERROR; 694 695 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 696 PPM_SCALE_INV, NTP_SCALE_SHIFT); 697 txc->maxerror = time_maxerror; 698 txc->esterror = time_esterror; 699 txc->status = time_status; 700 txc->constant = time_constant; 701 txc->precision = 1; 702 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 703 txc->tick = tick_usec; 704 txc->tai = *time_tai; 705 706 /* fill PPS status fields */ 707 pps_fill_timex(txc); 708 709 txc->time.tv_sec = (time_t)ts->tv_sec; 710 txc->time.tv_usec = ts->tv_nsec; 711 if (!(time_status & STA_NANO)) 712 txc->time.tv_usec /= NSEC_PER_USEC; 713 714 return result; 715} 716 717#ifdef CONFIG_NTP_PPS 718 719/* actually struct pps_normtime is good old struct timespec, but it is 720 * semantically different (and it is the reason why it was invented): 721 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 722 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 723struct pps_normtime { 724 __kernel_time_t sec; /* seconds */ 725 long nsec; /* nanoseconds */ 726}; 727 728/* normalize the timestamp so that nsec is in the 729 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 730static inline struct pps_normtime pps_normalize_ts(struct timespec ts) 731{ 732 struct pps_normtime norm = { 733 .sec = ts.tv_sec, 734 .nsec = ts.tv_nsec 735 }; 736 737 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 738 norm.nsec -= NSEC_PER_SEC; 739 norm.sec++; 740 } 741 742 return norm; 743} 744 745/* get current phase correction and jitter */ 746static inline long pps_phase_filter_get(long *jitter) 747{ 748 *jitter = pps_tf[0] - pps_tf[1]; 749 if (*jitter < 0) 750 *jitter = -*jitter; 751 752 /* TODO: test various filters */ 753 return pps_tf[0]; 754} 755 756/* add the sample to the phase filter */ 757static inline void pps_phase_filter_add(long err) 758{ 759 pps_tf[2] = pps_tf[1]; 760 pps_tf[1] = pps_tf[0]; 761 pps_tf[0] = err; 762} 763 764/* decrease frequency calibration interval length. 765 * It is halved after four consecutive unstable intervals. 766 */ 767static inline void pps_dec_freq_interval(void) 768{ 769 if (--pps_intcnt <= -PPS_INTCOUNT) { 770 pps_intcnt = -PPS_INTCOUNT; 771 if (pps_shift > PPS_INTMIN) { 772 pps_shift--; 773 pps_intcnt = 0; 774 } 775 } 776} 777 778/* increase frequency calibration interval length. 779 * It is doubled after four consecutive stable intervals. 780 */ 781static inline void pps_inc_freq_interval(void) 782{ 783 if (++pps_intcnt >= PPS_INTCOUNT) { 784 pps_intcnt = PPS_INTCOUNT; 785 if (pps_shift < PPS_INTMAX) { 786 pps_shift++; 787 pps_intcnt = 0; 788 } 789 } 790} 791 792/* update clock frequency based on MONOTONIC_RAW clock PPS signal 793 * timestamps 794 * 795 * At the end of the calibration interval the difference between the 796 * first and last MONOTONIC_RAW clock timestamps divided by the length 797 * of the interval becomes the frequency update. If the interval was 798 * too long, the data are discarded. 799 * Returns the difference between old and new frequency values. 800 */ 801static long hardpps_update_freq(struct pps_normtime freq_norm) 802{ 803 long delta, delta_mod; 804 s64 ftemp; 805 806 /* check if the frequency interval was too long */ 807 if (freq_norm.sec > (2 << pps_shift)) { 808 time_status |= STA_PPSERROR; 809 pps_errcnt++; 810 pps_dec_freq_interval(); 811 printk_deferred(KERN_ERR 812 "hardpps: PPSERROR: interval too long - %ld s\n", 813 freq_norm.sec); 814 return 0; 815 } 816 817 /* here the raw frequency offset and wander (stability) is 818 * calculated. If the wander is less than the wander threshold 819 * the interval is increased; otherwise it is decreased. 820 */ 821 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 822 freq_norm.sec); 823 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 824 pps_freq = ftemp; 825 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 826 printk_deferred(KERN_WARNING 827 "hardpps: PPSWANDER: change=%ld\n", delta); 828 time_status |= STA_PPSWANDER; 829 pps_stbcnt++; 830 pps_dec_freq_interval(); 831 } else { /* good sample */ 832 pps_inc_freq_interval(); 833 } 834 835 /* the stability metric is calculated as the average of recent 836 * frequency changes, but is used only for performance 837 * monitoring 838 */ 839 delta_mod = delta; 840 if (delta_mod < 0) 841 delta_mod = -delta_mod; 842 pps_stabil += (div_s64(((s64)delta_mod) << 843 (NTP_SCALE_SHIFT - SHIFT_USEC), 844 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 845 846 /* if enabled, the system clock frequency is updated */ 847 if ((time_status & STA_PPSFREQ) != 0 && 848 (time_status & STA_FREQHOLD) == 0) { 849 time_freq = pps_freq; 850 ntp_update_frequency(); 851 } 852 853 return delta; 854} 855 856/* correct REALTIME clock phase error against PPS signal */ 857static void hardpps_update_phase(long error) 858{ 859 long correction = -error; 860 long jitter; 861 862 /* add the sample to the median filter */ 863 pps_phase_filter_add(correction); 864 correction = pps_phase_filter_get(&jitter); 865 866 /* Nominal jitter is due to PPS signal noise. If it exceeds the 867 * threshold, the sample is discarded; otherwise, if so enabled, 868 * the time offset is updated. 869 */ 870 if (jitter > (pps_jitter << PPS_POPCORN)) { 871 printk_deferred(KERN_WARNING 872 "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 */ 899void __hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts) 900{ 901 struct pps_normtime pts_norm, freq_norm; 902 903 pts_norm = pps_normalize_ts(*phase_ts); 904 905 /* clear the error bits, they will be set again if needed */ 906 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 907 908 /* indicate signal presence */ 909 time_status |= STA_PPSSIGNAL; 910 pps_valid = PPS_VALID; 911 912 /* when called for the first time, 913 * just start the frequency interval */ 914 if (unlikely(pps_fbase.tv_sec == 0)) { 915 pps_fbase = *raw_ts; 916 return; 917 } 918 919 /* ok, now we have a base for frequency calculation */ 920 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase)); 921 922 /* check that the signal is in the range 923 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 924 if ((freq_norm.sec == 0) || 925 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 926 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 927 time_status |= STA_PPSJITTER; 928 /* restart the frequency calibration interval */ 929 pps_fbase = *raw_ts; 930 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 931 return; 932 } 933 934 /* signal is ok */ 935 936 /* check if the current frequency interval is finished */ 937 if (freq_norm.sec >= (1 << pps_shift)) { 938 pps_calcnt++; 939 /* restart the frequency calibration interval */ 940 pps_fbase = *raw_ts; 941 hardpps_update_freq(freq_norm); 942 } 943 944 hardpps_update_phase(pts_norm.nsec); 945 946} 947#endif /* CONFIG_NTP_PPS */ 948 949static int __init ntp_tick_adj_setup(char *str) 950{ 951 int rc = kstrtol(str, 0, (long *)&ntp_tick_adj); 952 953 if (rc) 954 return rc; 955 ntp_tick_adj <<= NTP_SCALE_SHIFT; 956 957 return 1; 958} 959 960__setup("ntp_tick_adj=", ntp_tick_adj_setup); 961 962void __init ntp_init(void) 963{ 964 ntp_clear(); 965} 966