1 /* 2 * NTP state machine interfaces and logic. 3 * 4 * This code was mainly moved from kernel/timer.c and kernel/time.c 5 * Please see those files for relevant copyright info and historical 6 * changelogs. 7 */ 8 #include <linux/capability.h> 9 #include <linux/clocksource.h> 10 #include <linux/workqueue.h> 11 #include <linux/hrtimer.h> 12 #include <linux/jiffies.h> 13 #include <linux/math64.h> 14 #include <linux/timex.h> 15 #include <linux/time.h> 16 #include <linux/mm.h> 17 #include <linux/module.h> 18 #include <linux/rtc.h> 19 20 #include "tick-internal.h" 21 #include "ntp_internal.h" 22 23 /* 24 * NTP timekeeping variables: 25 * 26 * Note: All of the NTP state is protected by the timekeeping locks. 27 */ 28 29 30 /* USER_HZ period (usecs): */ 31 unsigned long tick_usec = TICK_USEC; 32 33 /* SHIFTED_HZ period (nsecs): */ 34 unsigned long tick_nsec; 35 36 static u64 tick_length; 37 static u64 tick_length_base; 38 39 #define MAX_TICKADJ 500LL /* usecs */ 40 #define MAX_TICKADJ_SCALED \ 41 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) 42 43 /* 44 * phase-lock loop variables 45 */ 46 47 /* 48 * clock synchronization status 49 * 50 * (TIME_ERROR prevents overwriting the CMOS clock) 51 */ 52 static int time_state = TIME_OK; 53 54 /* clock status bits: */ 55 static int time_status = STA_UNSYNC; 56 57 /* time adjustment (nsecs): */ 58 static s64 time_offset; 59 60 /* pll time constant: */ 61 static long time_constant = 2; 62 63 /* maximum error (usecs): */ 64 static long time_maxerror = NTP_PHASE_LIMIT; 65 66 /* estimated error (usecs): */ 67 static long time_esterror = NTP_PHASE_LIMIT; 68 69 /* frequency offset (scaled nsecs/secs): */ 70 static s64 time_freq; 71 72 /* time at last adjustment (secs): */ 73 static long time_reftime; 74 75 static long time_adjust; 76 77 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 78 static s64 ntp_tick_adj; 79 80 #ifdef CONFIG_NTP_PPS 81 82 /* 83 * The following variables are used when a pulse-per-second (PPS) signal 84 * is available. They establish the engineering parameters of the clock 85 * discipline loop when controlled by the PPS signal. 86 */ 87 #define PPS_VALID 10 /* PPS signal watchdog max (s) */ 88 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 89 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 90 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 91 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to 92 increase pps_shift or consecutive bad 93 intervals to decrease it */ 94 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 95 96 static int pps_valid; /* signal watchdog counter */ 97 static long pps_tf[3]; /* phase median filter */ 98 static long pps_jitter; /* current jitter (ns) */ 99 static struct timespec pps_fbase; /* beginning of the last freq interval */ 100 static int pps_shift; /* current interval duration (s) (shift) */ 101 static int pps_intcnt; /* interval counter */ 102 static s64 pps_freq; /* frequency offset (scaled ns/s) */ 103 static long pps_stabil; /* current stability (scaled ns/s) */ 104 105 /* 106 * PPS signal quality monitors 107 */ 108 static long pps_calcnt; /* calibration intervals */ 109 static long pps_jitcnt; /* jitter limit exceeded */ 110 static long pps_stbcnt; /* stability limit exceeded */ 111 static long pps_errcnt; /* calibration errors */ 112 113 114 /* PPS kernel consumer compensates the whole phase error immediately. 115 * Otherwise, reduce the offset by a fixed factor times the time constant. 116 */ 117 static inline s64 ntp_offset_chunk(s64 offset) 118 { 119 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 120 return offset; 121 else 122 return shift_right(offset, SHIFT_PLL + time_constant); 123 } 124 125 static inline void pps_reset_freq_interval(void) 126 { 127 /* the PPS calibration interval may end 128 surprisingly early */ 129 pps_shift = PPS_INTMIN; 130 pps_intcnt = 0; 131 } 132 133 /** 134 * pps_clear - Clears the PPS state variables 135 */ 136 static inline void pps_clear(void) 137 { 138 pps_reset_freq_interval(); 139 pps_tf[0] = 0; 140 pps_tf[1] = 0; 141 pps_tf[2] = 0; 142 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 143 pps_freq = 0; 144 } 145 146 /* Decrease pps_valid to indicate that another second has passed since 147 * the last PPS signal. When it reaches 0, indicate that PPS signal is 148 * missing. 149 */ 150 static inline void pps_dec_valid(void) 151 { 152 if (pps_valid > 0) 153 pps_valid--; 154 else { 155 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 156 STA_PPSWANDER | STA_PPSERROR); 157 pps_clear(); 158 } 159 } 160 161 static inline void pps_set_freq(s64 freq) 162 { 163 pps_freq = freq; 164 } 165 166 static inline int is_error_status(int status) 167 { 168 return (status & (STA_UNSYNC|STA_CLOCKERR)) 169 /* PPS signal lost when either PPS time or 170 * PPS frequency synchronization requested 171 */ 172 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 173 && !(status & STA_PPSSIGNAL)) 174 /* PPS jitter exceeded when 175 * PPS time synchronization requested */ 176 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 177 == (STA_PPSTIME|STA_PPSJITTER)) 178 /* PPS wander exceeded or calibration error when 179 * PPS frequency synchronization requested 180 */ 181 || ((status & STA_PPSFREQ) 182 && (status & (STA_PPSWANDER|STA_PPSERROR))); 183 } 184 185 static inline void pps_fill_timex(struct timex *txc) 186 { 187 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 188 PPM_SCALE_INV, NTP_SCALE_SHIFT); 189 txc->jitter = pps_jitter; 190 if (!(time_status & STA_NANO)) 191 txc->jitter /= NSEC_PER_USEC; 192 txc->shift = pps_shift; 193 txc->stabil = pps_stabil; 194 txc->jitcnt = pps_jitcnt; 195 txc->calcnt = pps_calcnt; 196 txc->errcnt = pps_errcnt; 197 txc->stbcnt = pps_stbcnt; 198 } 199 200 #else /* !CONFIG_NTP_PPS */ 201 202 static inline s64 ntp_offset_chunk(s64 offset) 203 { 204 return shift_right(offset, SHIFT_PLL + time_constant); 205 } 206 207 static inline void pps_reset_freq_interval(void) {} 208 static inline void pps_clear(void) {} 209 static inline void pps_dec_valid(void) {} 210 static inline void pps_set_freq(s64 freq) {} 211 212 static inline int is_error_status(int status) 213 { 214 return status & (STA_UNSYNC|STA_CLOCKERR); 215 } 216 217 static inline void pps_fill_timex(struct timex *txc) 218 { 219 /* PPS is not implemented, so these are zero */ 220 txc->ppsfreq = 0; 221 txc->jitter = 0; 222 txc->shift = 0; 223 txc->stabil = 0; 224 txc->jitcnt = 0; 225 txc->calcnt = 0; 226 txc->errcnt = 0; 227 txc->stbcnt = 0; 228 } 229 230 #endif /* CONFIG_NTP_PPS */ 231 232 233 /** 234 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 235 * 236 */ 237 static inline int ntp_synced(void) 238 { 239 return !(time_status & STA_UNSYNC); 240 } 241 242 243 /* 244 * NTP methods: 245 */ 246 247 /* 248 * Update (tick_length, tick_length_base, tick_nsec), based 249 * on (tick_usec, ntp_tick_adj, time_freq): 250 */ 251 static void ntp_update_frequency(void) 252 { 253 u64 second_length; 254 u64 new_base; 255 256 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 257 << NTP_SCALE_SHIFT; 258 259 second_length += ntp_tick_adj; 260 second_length += time_freq; 261 262 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 263 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 264 265 /* 266 * Don't wait for the next second_overflow, apply 267 * the change to the tick length immediately: 268 */ 269 tick_length += new_base - tick_length_base; 270 tick_length_base = new_base; 271 } 272 273 static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 274 { 275 time_status &= ~STA_MODE; 276 277 if (secs < MINSEC) 278 return 0; 279 280 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 281 return 0; 282 283 time_status |= STA_MODE; 284 285 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 286 } 287 288 static void ntp_update_offset(long offset) 289 { 290 s64 freq_adj; 291 s64 offset64; 292 long secs; 293 294 if (!(time_status & STA_PLL)) 295 return; 296 297 if (!(time_status & STA_NANO)) 298 offset *= NSEC_PER_USEC; 299 300 /* 301 * Scale the phase adjustment and 302 * clamp to the operating range. 303 */ 304 offset = min(offset, MAXPHASE); 305 offset = max(offset, -MAXPHASE); 306 307 /* 308 * Select how the frequency is to be controlled 309 * and in which mode (PLL or FLL). 310 */ 311 secs = get_seconds() - time_reftime; 312 if (unlikely(time_status & STA_FREQHOLD)) 313 secs = 0; 314 315 time_reftime = get_seconds(); 316 317 offset64 = offset; 318 freq_adj = ntp_update_offset_fll(offset64, secs); 319 320 /* 321 * Clamp update interval to reduce PLL gain with low 322 * sampling rate (e.g. intermittent network connection) 323 * to avoid instability. 324 */ 325 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 326 secs = 1 << (SHIFT_PLL + 1 + time_constant); 327 328 freq_adj += (offset64 * secs) << 329 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 330 331 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 332 333 time_freq = max(freq_adj, -MAXFREQ_SCALED); 334 335 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 336 } 337 338 /** 339 * ntp_clear - Clears the NTP state variables 340 */ 341 void ntp_clear(void) 342 { 343 time_adjust = 0; /* stop active adjtime() */ 344 time_status |= STA_UNSYNC; 345 time_maxerror = NTP_PHASE_LIMIT; 346 time_esterror = NTP_PHASE_LIMIT; 347 348 ntp_update_frequency(); 349 350 tick_length = tick_length_base; 351 time_offset = 0; 352 353 /* Clear PPS state variables */ 354 pps_clear(); 355 } 356 357 358 u64 ntp_tick_length(void) 359 { 360 return tick_length; 361 } 362 363 364 /* 365 * this routine handles the overflow of the microsecond field 366 * 367 * The tricky bits of code to handle the accurate clock support 368 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 369 * They were originally developed for SUN and DEC kernels. 370 * All the kudos should go to Dave for this stuff. 371 * 372 * Also handles leap second processing, and returns leap offset 373 */ 374 int second_overflow(unsigned long secs) 375 { 376 s64 delta; 377 int leap = 0; 378 379 /* 380 * Leap second processing. If in leap-insert state at the end of the 381 * day, the system clock is set back one second; if in leap-delete 382 * state, the system clock is set ahead one second. 383 */ 384 switch (time_state) { 385 case TIME_OK: 386 if (time_status & STA_INS) 387 time_state = TIME_INS; 388 else if (time_status & STA_DEL) 389 time_state = TIME_DEL; 390 break; 391 case TIME_INS: 392 if (!(time_status & STA_INS)) 393 time_state = TIME_OK; 394 else if (secs % 86400 == 0) { 395 leap = -1; 396 time_state = TIME_OOP; 397 printk(KERN_NOTICE 398 "Clock: inserting leap second 23:59:60 UTC\n"); 399 } 400 break; 401 case TIME_DEL: 402 if (!(time_status & STA_DEL)) 403 time_state = TIME_OK; 404 else if ((secs + 1) % 86400 == 0) { 405 leap = 1; 406 time_state = TIME_WAIT; 407 printk(KERN_NOTICE 408 "Clock: deleting leap second 23:59:59 UTC\n"); 409 } 410 break; 411 case TIME_OOP: 412 time_state = TIME_WAIT; 413 break; 414 415 case TIME_WAIT: 416 if (!(time_status & (STA_INS | STA_DEL))) 417 time_state = TIME_OK; 418 break; 419 } 420 421 422 /* Bump the maxerror field */ 423 time_maxerror += MAXFREQ / NSEC_PER_USEC; 424 if (time_maxerror > NTP_PHASE_LIMIT) { 425 time_maxerror = NTP_PHASE_LIMIT; 426 time_status |= STA_UNSYNC; 427 } 428 429 /* Compute the phase adjustment for the next second */ 430 tick_length = tick_length_base; 431 432 delta = ntp_offset_chunk(time_offset); 433 time_offset -= delta; 434 tick_length += delta; 435 436 /* Check PPS signal */ 437 pps_dec_valid(); 438 439 if (!time_adjust) 440 goto out; 441 442 if (time_adjust > MAX_TICKADJ) { 443 time_adjust -= MAX_TICKADJ; 444 tick_length += MAX_TICKADJ_SCALED; 445 goto out; 446 } 447 448 if (time_adjust < -MAX_TICKADJ) { 449 time_adjust += MAX_TICKADJ; 450 tick_length -= MAX_TICKADJ_SCALED; 451 goto out; 452 } 453 454 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) 455 << NTP_SCALE_SHIFT; 456 time_adjust = 0; 457 458 out: 459 return leap; 460 } 461 462 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) 463 static void sync_cmos_clock(struct work_struct *work); 464 465 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); 466 467 static void sync_cmos_clock(struct work_struct *work) 468 { 469 struct timespec64 now; 470 struct timespec next; 471 int fail = 1; 472 473 /* 474 * If we have an externally synchronized Linux clock, then update 475 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be 476 * called as close as possible to 500 ms before the new second starts. 477 * This code is run on a timer. If the clock is set, that timer 478 * may not expire at the correct time. Thus, we adjust... 479 * We want the clock to be within a couple of ticks from the target. 480 */ 481 if (!ntp_synced()) { 482 /* 483 * Not synced, exit, do not restart a timer (if one is 484 * running, let it run out). 485 */ 486 return; 487 } 488 489 getnstimeofday64(&now); 490 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) { 491 struct timespec adjust = timespec64_to_timespec(now); 492 493 fail = -ENODEV; 494 if (persistent_clock_is_local) 495 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 496 #ifdef CONFIG_GENERIC_CMOS_UPDATE 497 fail = update_persistent_clock(adjust); 498 #endif 499 #ifdef CONFIG_RTC_SYSTOHC 500 if (fail == -ENODEV) 501 fail = rtc_set_ntp_time(adjust); 502 #endif 503 } 504 505 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); 506 if (next.tv_nsec <= 0) 507 next.tv_nsec += NSEC_PER_SEC; 508 509 if (!fail || fail == -ENODEV) 510 next.tv_sec = 659; 511 else 512 next.tv_sec = 0; 513 514 if (next.tv_nsec >= NSEC_PER_SEC) { 515 next.tv_sec++; 516 next.tv_nsec -= NSEC_PER_SEC; 517 } 518 queue_delayed_work(system_power_efficient_wq, 519 &sync_cmos_work, timespec_to_jiffies(&next)); 520 } 521 522 void ntp_notify_cmos_timer(void) 523 { 524 queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0); 525 } 526 527 #else 528 void ntp_notify_cmos_timer(void) { } 529 #endif 530 531 532 /* 533 * Propagate a new txc->status value into the NTP state: 534 */ 535 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts) 536 { 537 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 538 time_state = TIME_OK; 539 time_status = STA_UNSYNC; 540 /* restart PPS frequency calibration */ 541 pps_reset_freq_interval(); 542 } 543 544 /* 545 * If we turn on PLL adjustments then reset the 546 * reference time to current time. 547 */ 548 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 549 time_reftime = get_seconds(); 550 551 /* only set allowed bits */ 552 time_status &= STA_RONLY; 553 time_status |= txc->status & ~STA_RONLY; 554 } 555 556 557 static inline void process_adjtimex_modes(struct timex *txc, 558 struct timespec64 *ts, 559 s32 *time_tai) 560 { 561 if (txc->modes & ADJ_STATUS) 562 process_adj_status(txc, ts); 563 564 if (txc->modes & ADJ_NANO) 565 time_status |= STA_NANO; 566 567 if (txc->modes & ADJ_MICRO) 568 time_status &= ~STA_NANO; 569 570 if (txc->modes & ADJ_FREQUENCY) { 571 time_freq = txc->freq * PPM_SCALE; 572 time_freq = min(time_freq, MAXFREQ_SCALED); 573 time_freq = max(time_freq, -MAXFREQ_SCALED); 574 /* update pps_freq */ 575 pps_set_freq(time_freq); 576 } 577 578 if (txc->modes & ADJ_MAXERROR) 579 time_maxerror = txc->maxerror; 580 581 if (txc->modes & ADJ_ESTERROR) 582 time_esterror = txc->esterror; 583 584 if (txc->modes & ADJ_TIMECONST) { 585 time_constant = txc->constant; 586 if (!(time_status & STA_NANO)) 587 time_constant += 4; 588 time_constant = min(time_constant, (long)MAXTC); 589 time_constant = max(time_constant, 0l); 590 } 591 592 if (txc->modes & ADJ_TAI && txc->constant > 0) 593 *time_tai = txc->constant; 594 595 if (txc->modes & ADJ_OFFSET) 596 ntp_update_offset(txc->offset); 597 598 if (txc->modes & ADJ_TICK) 599 tick_usec = txc->tick; 600 601 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 602 ntp_update_frequency(); 603 } 604 605 606 607 /** 608 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex 609 */ 610 int ntp_validate_timex(struct timex *txc) 611 { 612 if (txc->modes & ADJ_ADJTIME) { 613 /* singleshot must not be used with any other mode bits */ 614 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT)) 615 return -EINVAL; 616 if (!(txc->modes & ADJ_OFFSET_READONLY) && 617 !capable(CAP_SYS_TIME)) 618 return -EPERM; 619 } else { 620 /* In order to modify anything, you gotta be super-user! */ 621 if (txc->modes && !capable(CAP_SYS_TIME)) 622 return -EPERM; 623 /* 624 * if the quartz is off by more than 10% then 625 * something is VERY wrong! 626 */ 627 if (txc->modes & ADJ_TICK && 628 (txc->tick < 900000/USER_HZ || 629 txc->tick > 1100000/USER_HZ)) 630 return -EINVAL; 631 } 632 633 if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME))) 634 return -EPERM; 635 636 return 0; 637 } 638 639 640 /* 641 * adjtimex mainly allows reading (and writing, if superuser) of 642 * kernel time-keeping variables. used by xntpd. 643 */ 644 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai) 645 { 646 int result; 647 648 if (txc->modes & ADJ_ADJTIME) { 649 long save_adjust = time_adjust; 650 651 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 652 /* adjtime() is independent from ntp_adjtime() */ 653 time_adjust = txc->offset; 654 ntp_update_frequency(); 655 } 656 txc->offset = save_adjust; 657 } else { 658 659 /* If there are input parameters, then process them: */ 660 if (txc->modes) 661 process_adjtimex_modes(txc, ts, time_tai); 662 663 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 664 NTP_SCALE_SHIFT); 665 if (!(time_status & STA_NANO)) 666 txc->offset /= NSEC_PER_USEC; 667 } 668 669 result = time_state; /* mostly `TIME_OK' */ 670 /* check for errors */ 671 if (is_error_status(time_status)) 672 result = TIME_ERROR; 673 674 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 675 PPM_SCALE_INV, NTP_SCALE_SHIFT); 676 txc->maxerror = time_maxerror; 677 txc->esterror = time_esterror; 678 txc->status = time_status; 679 txc->constant = time_constant; 680 txc->precision = 1; 681 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 682 txc->tick = tick_usec; 683 txc->tai = *time_tai; 684 685 /* fill PPS status fields */ 686 pps_fill_timex(txc); 687 688 txc->time.tv_sec = (time_t)ts->tv_sec; 689 txc->time.tv_usec = ts->tv_nsec; 690 if (!(time_status & STA_NANO)) 691 txc->time.tv_usec /= NSEC_PER_USEC; 692 693 return result; 694 } 695 696 #ifdef CONFIG_NTP_PPS 697 698 /* actually struct pps_normtime is good old struct timespec, but it is 699 * semantically different (and it is the reason why it was invented): 700 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 701 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 702 struct pps_normtime { 703 __kernel_time_t sec; /* seconds */ 704 long nsec; /* nanoseconds */ 705 }; 706 707 /* normalize the timestamp so that nsec is in the 708 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 709 static inline struct pps_normtime pps_normalize_ts(struct timespec ts) 710 { 711 struct pps_normtime norm = { 712 .sec = ts.tv_sec, 713 .nsec = ts.tv_nsec 714 }; 715 716 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 717 norm.nsec -= NSEC_PER_SEC; 718 norm.sec++; 719 } 720 721 return norm; 722 } 723 724 /* get current phase correction and jitter */ 725 static inline long pps_phase_filter_get(long *jitter) 726 { 727 *jitter = pps_tf[0] - pps_tf[1]; 728 if (*jitter < 0) 729 *jitter = -*jitter; 730 731 /* TODO: test various filters */ 732 return pps_tf[0]; 733 } 734 735 /* add the sample to the phase filter */ 736 static inline void pps_phase_filter_add(long err) 737 { 738 pps_tf[2] = pps_tf[1]; 739 pps_tf[1] = pps_tf[0]; 740 pps_tf[0] = err; 741 } 742 743 /* decrease frequency calibration interval length. 744 * It is halved after four consecutive unstable intervals. 745 */ 746 static inline void pps_dec_freq_interval(void) 747 { 748 if (--pps_intcnt <= -PPS_INTCOUNT) { 749 pps_intcnt = -PPS_INTCOUNT; 750 if (pps_shift > PPS_INTMIN) { 751 pps_shift--; 752 pps_intcnt = 0; 753 } 754 } 755 } 756 757 /* increase frequency calibration interval length. 758 * It is doubled after four consecutive stable intervals. 759 */ 760 static inline void pps_inc_freq_interval(void) 761 { 762 if (++pps_intcnt >= PPS_INTCOUNT) { 763 pps_intcnt = PPS_INTCOUNT; 764 if (pps_shift < PPS_INTMAX) { 765 pps_shift++; 766 pps_intcnt = 0; 767 } 768 } 769 } 770 771 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 772 * timestamps 773 * 774 * At the end of the calibration interval the difference between the 775 * first and last MONOTONIC_RAW clock timestamps divided by the length 776 * of the interval becomes the frequency update. If the interval was 777 * too long, the data are discarded. 778 * Returns the difference between old and new frequency values. 779 */ 780 static long hardpps_update_freq(struct pps_normtime freq_norm) 781 { 782 long delta, delta_mod; 783 s64 ftemp; 784 785 /* check if the frequency interval was too long */ 786 if (freq_norm.sec > (2 << pps_shift)) { 787 time_status |= STA_PPSERROR; 788 pps_errcnt++; 789 pps_dec_freq_interval(); 790 printk_deferred(KERN_ERR 791 "hardpps: PPSERROR: interval too long - %ld s\n", 792 freq_norm.sec); 793 return 0; 794 } 795 796 /* here the raw frequency offset and wander (stability) is 797 * calculated. If the wander is less than the wander threshold 798 * the interval is increased; otherwise it is decreased. 799 */ 800 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 801 freq_norm.sec); 802 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 803 pps_freq = ftemp; 804 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 805 printk_deferred(KERN_WARNING 806 "hardpps: PPSWANDER: change=%ld\n", delta); 807 time_status |= STA_PPSWANDER; 808 pps_stbcnt++; 809 pps_dec_freq_interval(); 810 } else { /* good sample */ 811 pps_inc_freq_interval(); 812 } 813 814 /* the stability metric is calculated as the average of recent 815 * frequency changes, but is used only for performance 816 * monitoring 817 */ 818 delta_mod = delta; 819 if (delta_mod < 0) 820 delta_mod = -delta_mod; 821 pps_stabil += (div_s64(((s64)delta_mod) << 822 (NTP_SCALE_SHIFT - SHIFT_USEC), 823 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 824 825 /* if enabled, the system clock frequency is updated */ 826 if ((time_status & STA_PPSFREQ) != 0 && 827 (time_status & STA_FREQHOLD) == 0) { 828 time_freq = pps_freq; 829 ntp_update_frequency(); 830 } 831 832 return delta; 833 } 834 835 /* correct REALTIME clock phase error against PPS signal */ 836 static void hardpps_update_phase(long error) 837 { 838 long correction = -error; 839 long jitter; 840 841 /* add the sample to the median filter */ 842 pps_phase_filter_add(correction); 843 correction = pps_phase_filter_get(&jitter); 844 845 /* Nominal jitter is due to PPS signal noise. If it exceeds the 846 * threshold, the sample is discarded; otherwise, if so enabled, 847 * the time offset is updated. 848 */ 849 if (jitter > (pps_jitter << PPS_POPCORN)) { 850 printk_deferred(KERN_WARNING 851 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 852 jitter, (pps_jitter << PPS_POPCORN)); 853 time_status |= STA_PPSJITTER; 854 pps_jitcnt++; 855 } else if (time_status & STA_PPSTIME) { 856 /* correct the time using the phase offset */ 857 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 858 NTP_INTERVAL_FREQ); 859 /* cancel running adjtime() */ 860 time_adjust = 0; 861 } 862 /* update jitter */ 863 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 864 } 865 866 /* 867 * __hardpps() - discipline CPU clock oscillator to external PPS signal 868 * 869 * This routine is called at each PPS signal arrival in order to 870 * discipline the CPU clock oscillator to the PPS signal. It takes two 871 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 872 * is used to correct clock phase error and the latter is used to 873 * correct the frequency. 874 * 875 * This code is based on David Mills's reference nanokernel 876 * implementation. It was mostly rewritten but keeps the same idea. 877 */ 878 void __hardpps(const struct timespec *phase_ts, const struct timespec *raw_ts) 879 { 880 struct pps_normtime pts_norm, freq_norm; 881 882 pts_norm = pps_normalize_ts(*phase_ts); 883 884 /* clear the error bits, they will be set again if needed */ 885 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 886 887 /* indicate signal presence */ 888 time_status |= STA_PPSSIGNAL; 889 pps_valid = PPS_VALID; 890 891 /* when called for the first time, 892 * just start the frequency interval */ 893 if (unlikely(pps_fbase.tv_sec == 0)) { 894 pps_fbase = *raw_ts; 895 return; 896 } 897 898 /* ok, now we have a base for frequency calculation */ 899 freq_norm = pps_normalize_ts(timespec_sub(*raw_ts, pps_fbase)); 900 901 /* check that the signal is in the range 902 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 903 if ((freq_norm.sec == 0) || 904 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 905 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 906 time_status |= STA_PPSJITTER; 907 /* restart the frequency calibration interval */ 908 pps_fbase = *raw_ts; 909 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 910 return; 911 } 912 913 /* signal is ok */ 914 915 /* check if the current frequency interval is finished */ 916 if (freq_norm.sec >= (1 << pps_shift)) { 917 pps_calcnt++; 918 /* restart the frequency calibration interval */ 919 pps_fbase = *raw_ts; 920 hardpps_update_freq(freq_norm); 921 } 922 923 hardpps_update_phase(pts_norm.nsec); 924 925 } 926 #endif /* CONFIG_NTP_PPS */ 927 928 static int __init ntp_tick_adj_setup(char *str) 929 { 930 int rc = kstrtol(str, 0, (long *)&ntp_tick_adj); 931 932 if (rc) 933 return rc; 934 ntp_tick_adj <<= NTP_SCALE_SHIFT; 935 936 return 1; 937 } 938 939 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 940 941 void __init ntp_init(void) 942 { 943 ntp_clear(); 944 } 945