1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * NTP state machine interfaces and logic. 4 * 5 * This code was mainly moved from kernel/timer.c and kernel/time.c 6 * Please see those files for relevant copyright info and historical 7 * changelogs. 8 */ 9 #include <linux/capability.h> 10 #include <linux/clocksource.h> 11 #include <linux/workqueue.h> 12 #include <linux/hrtimer.h> 13 #include <linux/jiffies.h> 14 #include <linux/math64.h> 15 #include <linux/timex.h> 16 #include <linux/time.h> 17 #include <linux/mm.h> 18 #include <linux/module.h> 19 #include <linux/rtc.h> 20 #include <linux/math64.h> 21 22 #include "ntp_internal.h" 23 #include "timekeeping_internal.h" 24 25 26 /* 27 * NTP timekeeping variables: 28 * 29 * Note: All of the NTP state is protected by the timekeeping locks. 30 */ 31 32 33 /* USER_HZ period (usecs): */ 34 unsigned long tick_usec = USER_TICK_USEC; 35 36 /* SHIFTED_HZ period (nsecs): */ 37 unsigned long tick_nsec; 38 39 static u64 tick_length; 40 static u64 tick_length_base; 41 42 #define SECS_PER_DAY 86400 43 #define MAX_TICKADJ 500LL /* usecs */ 44 #define MAX_TICKADJ_SCALED \ 45 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) 46 47 /* 48 * phase-lock loop variables 49 */ 50 51 /* 52 * clock synchronization status 53 * 54 * (TIME_ERROR prevents overwriting the CMOS clock) 55 */ 56 static int time_state = TIME_OK; 57 58 /* clock status bits: */ 59 static int time_status = STA_UNSYNC; 60 61 /* time adjustment (nsecs): */ 62 static s64 time_offset; 63 64 /* pll time constant: */ 65 static long time_constant = 2; 66 67 /* maximum error (usecs): */ 68 static long time_maxerror = NTP_PHASE_LIMIT; 69 70 /* estimated error (usecs): */ 71 static long time_esterror = NTP_PHASE_LIMIT; 72 73 /* frequency offset (scaled nsecs/secs): */ 74 static s64 time_freq; 75 76 /* time at last adjustment (secs): */ 77 static time64_t time_reftime; 78 79 static long time_adjust; 80 81 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 82 static s64 ntp_tick_adj; 83 84 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */ 85 static time64_t ntp_next_leap_sec = TIME64_MAX; 86 87 #ifdef CONFIG_NTP_PPS 88 89 /* 90 * The following variables are used when a pulse-per-second (PPS) signal 91 * is available. They establish the engineering parameters of the clock 92 * discipline loop when controlled by the PPS signal. 93 */ 94 #define PPS_VALID 10 /* PPS signal watchdog max (s) */ 95 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 96 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 97 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 98 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to 99 increase pps_shift or consecutive bad 100 intervals to decrease it */ 101 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 102 103 static int pps_valid; /* signal watchdog counter */ 104 static long pps_tf[3]; /* phase median filter */ 105 static long pps_jitter; /* current jitter (ns) */ 106 static struct timespec64 pps_fbase; /* beginning of the last freq interval */ 107 static int pps_shift; /* current interval duration (s) (shift) */ 108 static int pps_intcnt; /* interval counter */ 109 static s64 pps_freq; /* frequency offset (scaled ns/s) */ 110 static long pps_stabil; /* current stability (scaled ns/s) */ 111 112 /* 113 * PPS signal quality monitors 114 */ 115 static long pps_calcnt; /* calibration intervals */ 116 static long pps_jitcnt; /* jitter limit exceeded */ 117 static long pps_stbcnt; /* stability limit exceeded */ 118 static long pps_errcnt; /* calibration errors */ 119 120 121 /* PPS kernel consumer compensates the whole phase error immediately. 122 * Otherwise, reduce the offset by a fixed factor times the time constant. 123 */ 124 static inline s64 ntp_offset_chunk(s64 offset) 125 { 126 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 127 return offset; 128 else 129 return shift_right(offset, SHIFT_PLL + time_constant); 130 } 131 132 static inline void pps_reset_freq_interval(void) 133 { 134 /* the PPS calibration interval may end 135 surprisingly early */ 136 pps_shift = PPS_INTMIN; 137 pps_intcnt = 0; 138 } 139 140 /** 141 * pps_clear - Clears the PPS state variables 142 */ 143 static inline void pps_clear(void) 144 { 145 pps_reset_freq_interval(); 146 pps_tf[0] = 0; 147 pps_tf[1] = 0; 148 pps_tf[2] = 0; 149 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 150 pps_freq = 0; 151 } 152 153 /* Decrease pps_valid to indicate that another second has passed since 154 * the last PPS signal. When it reaches 0, indicate that PPS signal is 155 * missing. 156 */ 157 static inline void pps_dec_valid(void) 158 { 159 if (pps_valid > 0) 160 pps_valid--; 161 else { 162 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 163 STA_PPSWANDER | STA_PPSERROR); 164 pps_clear(); 165 } 166 } 167 168 static inline void pps_set_freq(s64 freq) 169 { 170 pps_freq = freq; 171 } 172 173 static inline int is_error_status(int status) 174 { 175 return (status & (STA_UNSYNC|STA_CLOCKERR)) 176 /* PPS signal lost when either PPS time or 177 * PPS frequency synchronization requested 178 */ 179 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 180 && !(status & STA_PPSSIGNAL)) 181 /* PPS jitter exceeded when 182 * PPS time synchronization requested */ 183 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 184 == (STA_PPSTIME|STA_PPSJITTER)) 185 /* PPS wander exceeded or calibration error when 186 * PPS frequency synchronization requested 187 */ 188 || ((status & STA_PPSFREQ) 189 && (status & (STA_PPSWANDER|STA_PPSERROR))); 190 } 191 192 static inline void pps_fill_timex(struct timex *txc) 193 { 194 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 195 PPM_SCALE_INV, NTP_SCALE_SHIFT); 196 txc->jitter = pps_jitter; 197 if (!(time_status & STA_NANO)) 198 txc->jitter /= NSEC_PER_USEC; 199 txc->shift = pps_shift; 200 txc->stabil = pps_stabil; 201 txc->jitcnt = pps_jitcnt; 202 txc->calcnt = pps_calcnt; 203 txc->errcnt = pps_errcnt; 204 txc->stbcnt = pps_stbcnt; 205 } 206 207 #else /* !CONFIG_NTP_PPS */ 208 209 static inline s64 ntp_offset_chunk(s64 offset) 210 { 211 return shift_right(offset, SHIFT_PLL + time_constant); 212 } 213 214 static inline void pps_reset_freq_interval(void) {} 215 static inline void pps_clear(void) {} 216 static inline void pps_dec_valid(void) {} 217 static inline void pps_set_freq(s64 freq) {} 218 219 static inline int is_error_status(int status) 220 { 221 return status & (STA_UNSYNC|STA_CLOCKERR); 222 } 223 224 static inline void pps_fill_timex(struct timex *txc) 225 { 226 /* PPS is not implemented, so these are zero */ 227 txc->ppsfreq = 0; 228 txc->jitter = 0; 229 txc->shift = 0; 230 txc->stabil = 0; 231 txc->jitcnt = 0; 232 txc->calcnt = 0; 233 txc->errcnt = 0; 234 txc->stbcnt = 0; 235 } 236 237 #endif /* CONFIG_NTP_PPS */ 238 239 240 /** 241 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 242 * 243 */ 244 static inline int ntp_synced(void) 245 { 246 return !(time_status & STA_UNSYNC); 247 } 248 249 250 /* 251 * NTP methods: 252 */ 253 254 /* 255 * Update (tick_length, tick_length_base, tick_nsec), based 256 * on (tick_usec, ntp_tick_adj, time_freq): 257 */ 258 static void ntp_update_frequency(void) 259 { 260 u64 second_length; 261 u64 new_base; 262 263 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 264 << NTP_SCALE_SHIFT; 265 266 second_length += ntp_tick_adj; 267 second_length += time_freq; 268 269 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 270 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 271 272 /* 273 * Don't wait for the next second_overflow, apply 274 * the change to the tick length immediately: 275 */ 276 tick_length += new_base - tick_length_base; 277 tick_length_base = new_base; 278 } 279 280 static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 281 { 282 time_status &= ~STA_MODE; 283 284 if (secs < MINSEC) 285 return 0; 286 287 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 288 return 0; 289 290 time_status |= STA_MODE; 291 292 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 293 } 294 295 static void ntp_update_offset(long offset) 296 { 297 s64 freq_adj; 298 s64 offset64; 299 long secs; 300 301 if (!(time_status & STA_PLL)) 302 return; 303 304 if (!(time_status & STA_NANO)) { 305 /* Make sure the multiplication below won't overflow */ 306 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC); 307 offset *= NSEC_PER_USEC; 308 } 309 310 /* 311 * Scale the phase adjustment and 312 * clamp to the operating range. 313 */ 314 offset = clamp(offset, -MAXPHASE, MAXPHASE); 315 316 /* 317 * Select how the frequency is to be controlled 318 * and in which mode (PLL or FLL). 319 */ 320 secs = (long)(__ktime_get_real_seconds() - time_reftime); 321 if (unlikely(time_status & STA_FREQHOLD)) 322 secs = 0; 323 324 time_reftime = __ktime_get_real_seconds(); 325 326 offset64 = offset; 327 freq_adj = ntp_update_offset_fll(offset64, secs); 328 329 /* 330 * Clamp update interval to reduce PLL gain with low 331 * sampling rate (e.g. intermittent network connection) 332 * to avoid instability. 333 */ 334 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 335 secs = 1 << (SHIFT_PLL + 1 + time_constant); 336 337 freq_adj += (offset64 * secs) << 338 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 339 340 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 341 342 time_freq = max(freq_adj, -MAXFREQ_SCALED); 343 344 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 345 } 346 347 /** 348 * ntp_clear - Clears the NTP state variables 349 */ 350 void ntp_clear(void) 351 { 352 time_adjust = 0; /* stop active adjtime() */ 353 time_status |= STA_UNSYNC; 354 time_maxerror = NTP_PHASE_LIMIT; 355 time_esterror = NTP_PHASE_LIMIT; 356 357 ntp_update_frequency(); 358 359 tick_length = tick_length_base; 360 time_offset = 0; 361 362 ntp_next_leap_sec = TIME64_MAX; 363 /* Clear PPS state variables */ 364 pps_clear(); 365 } 366 367 368 u64 ntp_tick_length(void) 369 { 370 return tick_length; 371 } 372 373 /** 374 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t 375 * 376 * Provides the time of the next leapsecond against CLOCK_REALTIME in 377 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending. 378 */ 379 ktime_t ntp_get_next_leap(void) 380 { 381 ktime_t ret; 382 383 if ((time_state == TIME_INS) && (time_status & STA_INS)) 384 return ktime_set(ntp_next_leap_sec, 0); 385 ret = KTIME_MAX; 386 return ret; 387 } 388 389 /* 390 * this routine handles the overflow of the microsecond field 391 * 392 * The tricky bits of code to handle the accurate clock support 393 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 394 * They were originally developed for SUN and DEC kernels. 395 * All the kudos should go to Dave for this stuff. 396 * 397 * Also handles leap second processing, and returns leap offset 398 */ 399 int second_overflow(time64_t secs) 400 { 401 s64 delta; 402 int leap = 0; 403 s32 rem; 404 405 /* 406 * Leap second processing. If in leap-insert state at the end of the 407 * day, the system clock is set back one second; if in leap-delete 408 * state, the system clock is set ahead one second. 409 */ 410 switch (time_state) { 411 case TIME_OK: 412 if (time_status & STA_INS) { 413 time_state = TIME_INS; 414 div_s64_rem(secs, SECS_PER_DAY, &rem); 415 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 416 } else if (time_status & STA_DEL) { 417 time_state = TIME_DEL; 418 div_s64_rem(secs + 1, SECS_PER_DAY, &rem); 419 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 420 } 421 break; 422 case TIME_INS: 423 if (!(time_status & STA_INS)) { 424 ntp_next_leap_sec = TIME64_MAX; 425 time_state = TIME_OK; 426 } else if (secs == ntp_next_leap_sec) { 427 leap = -1; 428 time_state = TIME_OOP; 429 printk(KERN_NOTICE 430 "Clock: inserting leap second 23:59:60 UTC\n"); 431 } 432 break; 433 case TIME_DEL: 434 if (!(time_status & STA_DEL)) { 435 ntp_next_leap_sec = TIME64_MAX; 436 time_state = TIME_OK; 437 } else if (secs == ntp_next_leap_sec) { 438 leap = 1; 439 ntp_next_leap_sec = TIME64_MAX; 440 time_state = TIME_WAIT; 441 printk(KERN_NOTICE 442 "Clock: deleting leap second 23:59:59 UTC\n"); 443 } 444 break; 445 case TIME_OOP: 446 ntp_next_leap_sec = TIME64_MAX; 447 time_state = TIME_WAIT; 448 break; 449 case TIME_WAIT: 450 if (!(time_status & (STA_INS | STA_DEL))) 451 time_state = TIME_OK; 452 break; 453 } 454 455 456 /* Bump the maxerror field */ 457 time_maxerror += MAXFREQ / NSEC_PER_USEC; 458 if (time_maxerror > NTP_PHASE_LIMIT) { 459 time_maxerror = NTP_PHASE_LIMIT; 460 time_status |= STA_UNSYNC; 461 } 462 463 /* Compute the phase adjustment for the next second */ 464 tick_length = tick_length_base; 465 466 delta = ntp_offset_chunk(time_offset); 467 time_offset -= delta; 468 tick_length += delta; 469 470 /* Check PPS signal */ 471 pps_dec_valid(); 472 473 if (!time_adjust) 474 goto out; 475 476 if (time_adjust > MAX_TICKADJ) { 477 time_adjust -= MAX_TICKADJ; 478 tick_length += MAX_TICKADJ_SCALED; 479 goto out; 480 } 481 482 if (time_adjust < -MAX_TICKADJ) { 483 time_adjust += MAX_TICKADJ; 484 tick_length -= MAX_TICKADJ_SCALED; 485 goto out; 486 } 487 488 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) 489 << NTP_SCALE_SHIFT; 490 time_adjust = 0; 491 492 out: 493 return leap; 494 } 495 496 static void sync_hw_clock(struct work_struct *work); 497 static DECLARE_DELAYED_WORK(sync_work, sync_hw_clock); 498 499 static void sched_sync_hw_clock(struct timespec64 now, 500 unsigned long target_nsec, bool fail) 501 502 { 503 struct timespec64 next; 504 505 ktime_get_real_ts64(&next); 506 if (!fail) 507 next.tv_sec = 659; 508 else { 509 /* 510 * Try again as soon as possible. Delaying long periods 511 * decreases the accuracy of the work queue timer. Due to this 512 * the algorithm is very likely to require a short-sleep retry 513 * after the above long sleep to synchronize ts_nsec. 514 */ 515 next.tv_sec = 0; 516 } 517 518 /* Compute the needed delay that will get to tv_nsec == target_nsec */ 519 next.tv_nsec = target_nsec - next.tv_nsec; 520 if (next.tv_nsec <= 0) 521 next.tv_nsec += NSEC_PER_SEC; 522 if (next.tv_nsec >= NSEC_PER_SEC) { 523 next.tv_sec++; 524 next.tv_nsec -= NSEC_PER_SEC; 525 } 526 527 queue_delayed_work(system_power_efficient_wq, &sync_work, 528 timespec64_to_jiffies(&next)); 529 } 530 531 static void sync_rtc_clock(void) 532 { 533 unsigned long target_nsec; 534 struct timespec64 adjust, now; 535 int rc; 536 537 if (!IS_ENABLED(CONFIG_RTC_SYSTOHC)) 538 return; 539 540 ktime_get_real_ts64(&now); 541 542 adjust = now; 543 if (persistent_clock_is_local) 544 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 545 546 /* 547 * The current RTC in use will provide the target_nsec it wants to be 548 * called at, and does rtc_tv_nsec_ok internally. 549 */ 550 rc = rtc_set_ntp_time(adjust, &target_nsec); 551 if (rc == -ENODEV) 552 return; 553 554 sched_sync_hw_clock(now, target_nsec, rc); 555 } 556 557 #ifdef CONFIG_GENERIC_CMOS_UPDATE 558 int __weak update_persistent_clock(struct timespec now) 559 { 560 return -ENODEV; 561 } 562 563 int __weak update_persistent_clock64(struct timespec64 now64) 564 { 565 struct timespec now; 566 567 now = timespec64_to_timespec(now64); 568 return update_persistent_clock(now); 569 } 570 #endif 571 572 static bool sync_cmos_clock(void) 573 { 574 static bool no_cmos; 575 struct timespec64 now; 576 struct timespec64 adjust; 577 int rc = -EPROTO; 578 long target_nsec = NSEC_PER_SEC / 2; 579 580 if (!IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE)) 581 return false; 582 583 if (no_cmos) 584 return false; 585 586 /* 587 * Historically update_persistent_clock64() has followed x86 588 * semantics, which match the MC146818A/etc RTC. This RTC will store 589 * 'adjust' and then in .5s it will advance once second. 590 * 591 * Architectures are strongly encouraged to use rtclib and not 592 * implement this legacy API. 593 */ 594 ktime_get_real_ts64(&now); 595 if (rtc_tv_nsec_ok(-1 * target_nsec, &adjust, &now)) { 596 if (persistent_clock_is_local) 597 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 598 rc = update_persistent_clock64(adjust); 599 /* 600 * The machine does not support update_persistent_clock64 even 601 * though it defines CONFIG_GENERIC_CMOS_UPDATE. 602 */ 603 if (rc == -ENODEV) { 604 no_cmos = true; 605 return false; 606 } 607 } 608 609 sched_sync_hw_clock(now, target_nsec, rc); 610 return true; 611 } 612 613 /* 614 * If we have an externally synchronized Linux clock, then update RTC clock 615 * accordingly every ~11 minutes. Generally RTCs can only store second 616 * precision, but many RTCs will adjust the phase of their second tick to 617 * match the moment of update. This infrastructure arranges to call to the RTC 618 * set at the correct moment to phase synchronize the RTC second tick over 619 * with the kernel clock. 620 */ 621 static void sync_hw_clock(struct work_struct *work) 622 { 623 if (!ntp_synced()) 624 return; 625 626 if (sync_cmos_clock()) 627 return; 628 629 sync_rtc_clock(); 630 } 631 632 void ntp_notify_cmos_timer(void) 633 { 634 if (!ntp_synced()) 635 return; 636 637 if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) || 638 IS_ENABLED(CONFIG_RTC_SYSTOHC)) 639 queue_delayed_work(system_power_efficient_wq, &sync_work, 0); 640 } 641 642 /* 643 * Propagate a new txc->status value into the NTP state: 644 */ 645 static inline void process_adj_status(const struct timex *txc) 646 { 647 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 648 time_state = TIME_OK; 649 time_status = STA_UNSYNC; 650 ntp_next_leap_sec = TIME64_MAX; 651 /* restart PPS frequency calibration */ 652 pps_reset_freq_interval(); 653 } 654 655 /* 656 * If we turn on PLL adjustments then reset the 657 * reference time to current time. 658 */ 659 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 660 time_reftime = __ktime_get_real_seconds(); 661 662 /* only set allowed bits */ 663 time_status &= STA_RONLY; 664 time_status |= txc->status & ~STA_RONLY; 665 } 666 667 668 static inline void process_adjtimex_modes(const struct timex *txc, s32 *time_tai) 669 { 670 if (txc->modes & ADJ_STATUS) 671 process_adj_status(txc); 672 673 if (txc->modes & ADJ_NANO) 674 time_status |= STA_NANO; 675 676 if (txc->modes & ADJ_MICRO) 677 time_status &= ~STA_NANO; 678 679 if (txc->modes & ADJ_FREQUENCY) { 680 time_freq = txc->freq * PPM_SCALE; 681 time_freq = min(time_freq, MAXFREQ_SCALED); 682 time_freq = max(time_freq, -MAXFREQ_SCALED); 683 /* update pps_freq */ 684 pps_set_freq(time_freq); 685 } 686 687 if (txc->modes & ADJ_MAXERROR) 688 time_maxerror = txc->maxerror; 689 690 if (txc->modes & ADJ_ESTERROR) 691 time_esterror = txc->esterror; 692 693 if (txc->modes & ADJ_TIMECONST) { 694 time_constant = txc->constant; 695 if (!(time_status & STA_NANO)) 696 time_constant += 4; 697 time_constant = min(time_constant, (long)MAXTC); 698 time_constant = max(time_constant, 0l); 699 } 700 701 if (txc->modes & ADJ_TAI && txc->constant > 0) 702 *time_tai = txc->constant; 703 704 if (txc->modes & ADJ_OFFSET) 705 ntp_update_offset(txc->offset); 706 707 if (txc->modes & ADJ_TICK) 708 tick_usec = txc->tick; 709 710 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 711 ntp_update_frequency(); 712 } 713 714 715 /* 716 * adjtimex mainly allows reading (and writing, if superuser) of 717 * kernel time-keeping variables. used by xntpd. 718 */ 719 int __do_adjtimex(struct timex *txc, const struct timespec64 *ts, s32 *time_tai) 720 { 721 int result; 722 723 if (txc->modes & ADJ_ADJTIME) { 724 long save_adjust = time_adjust; 725 726 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 727 /* adjtime() is independent from ntp_adjtime() */ 728 time_adjust = txc->offset; 729 ntp_update_frequency(); 730 } 731 txc->offset = save_adjust; 732 } else { 733 734 /* If there are input parameters, then process them: */ 735 if (txc->modes) 736 process_adjtimex_modes(txc, time_tai); 737 738 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 739 NTP_SCALE_SHIFT); 740 if (!(time_status & STA_NANO)) 741 txc->offset /= NSEC_PER_USEC; 742 } 743 744 result = time_state; /* mostly `TIME_OK' */ 745 /* check for errors */ 746 if (is_error_status(time_status)) 747 result = TIME_ERROR; 748 749 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 750 PPM_SCALE_INV, NTP_SCALE_SHIFT); 751 txc->maxerror = time_maxerror; 752 txc->esterror = time_esterror; 753 txc->status = time_status; 754 txc->constant = time_constant; 755 txc->precision = 1; 756 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 757 txc->tick = tick_usec; 758 txc->tai = *time_tai; 759 760 /* fill PPS status fields */ 761 pps_fill_timex(txc); 762 763 txc->time.tv_sec = (time_t)ts->tv_sec; 764 txc->time.tv_usec = ts->tv_nsec; 765 if (!(time_status & STA_NANO)) 766 txc->time.tv_usec /= NSEC_PER_USEC; 767 768 /* Handle leapsec adjustments */ 769 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 770 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 771 result = TIME_OOP; 772 txc->tai++; 773 txc->time.tv_sec--; 774 } 775 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 776 result = TIME_WAIT; 777 txc->tai--; 778 txc->time.tv_sec++; 779 } 780 if ((time_state == TIME_OOP) && 781 (ts->tv_sec == ntp_next_leap_sec)) { 782 result = TIME_WAIT; 783 } 784 } 785 786 return result; 787 } 788 789 #ifdef CONFIG_NTP_PPS 790 791 /* actually struct pps_normtime is good old struct timespec, but it is 792 * semantically different (and it is the reason why it was invented): 793 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 794 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 795 struct pps_normtime { 796 s64 sec; /* seconds */ 797 long nsec; /* nanoseconds */ 798 }; 799 800 /* normalize the timestamp so that nsec is in the 801 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 802 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 803 { 804 struct pps_normtime norm = { 805 .sec = ts.tv_sec, 806 .nsec = ts.tv_nsec 807 }; 808 809 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 810 norm.nsec -= NSEC_PER_SEC; 811 norm.sec++; 812 } 813 814 return norm; 815 } 816 817 /* get current phase correction and jitter */ 818 static inline long pps_phase_filter_get(long *jitter) 819 { 820 *jitter = pps_tf[0] - pps_tf[1]; 821 if (*jitter < 0) 822 *jitter = -*jitter; 823 824 /* TODO: test various filters */ 825 return pps_tf[0]; 826 } 827 828 /* add the sample to the phase filter */ 829 static inline void pps_phase_filter_add(long err) 830 { 831 pps_tf[2] = pps_tf[1]; 832 pps_tf[1] = pps_tf[0]; 833 pps_tf[0] = err; 834 } 835 836 /* decrease frequency calibration interval length. 837 * It is halved after four consecutive unstable intervals. 838 */ 839 static inline void pps_dec_freq_interval(void) 840 { 841 if (--pps_intcnt <= -PPS_INTCOUNT) { 842 pps_intcnt = -PPS_INTCOUNT; 843 if (pps_shift > PPS_INTMIN) { 844 pps_shift--; 845 pps_intcnt = 0; 846 } 847 } 848 } 849 850 /* increase frequency calibration interval length. 851 * It is doubled after four consecutive stable intervals. 852 */ 853 static inline void pps_inc_freq_interval(void) 854 { 855 if (++pps_intcnt >= PPS_INTCOUNT) { 856 pps_intcnt = PPS_INTCOUNT; 857 if (pps_shift < PPS_INTMAX) { 858 pps_shift++; 859 pps_intcnt = 0; 860 } 861 } 862 } 863 864 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 865 * timestamps 866 * 867 * At the end of the calibration interval the difference between the 868 * first and last MONOTONIC_RAW clock timestamps divided by the length 869 * of the interval becomes the frequency update. If the interval was 870 * too long, the data are discarded. 871 * Returns the difference between old and new frequency values. 872 */ 873 static long hardpps_update_freq(struct pps_normtime freq_norm) 874 { 875 long delta, delta_mod; 876 s64 ftemp; 877 878 /* check if the frequency interval was too long */ 879 if (freq_norm.sec > (2 << pps_shift)) { 880 time_status |= STA_PPSERROR; 881 pps_errcnt++; 882 pps_dec_freq_interval(); 883 printk_deferred(KERN_ERR 884 "hardpps: PPSERROR: interval too long - %lld s\n", 885 freq_norm.sec); 886 return 0; 887 } 888 889 /* here the raw frequency offset and wander (stability) is 890 * calculated. If the wander is less than the wander threshold 891 * the interval is increased; otherwise it is decreased. 892 */ 893 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 894 freq_norm.sec); 895 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 896 pps_freq = ftemp; 897 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 898 printk_deferred(KERN_WARNING 899 "hardpps: PPSWANDER: change=%ld\n", delta); 900 time_status |= STA_PPSWANDER; 901 pps_stbcnt++; 902 pps_dec_freq_interval(); 903 } else { /* good sample */ 904 pps_inc_freq_interval(); 905 } 906 907 /* the stability metric is calculated as the average of recent 908 * frequency changes, but is used only for performance 909 * monitoring 910 */ 911 delta_mod = delta; 912 if (delta_mod < 0) 913 delta_mod = -delta_mod; 914 pps_stabil += (div_s64(((s64)delta_mod) << 915 (NTP_SCALE_SHIFT - SHIFT_USEC), 916 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 917 918 /* if enabled, the system clock frequency is updated */ 919 if ((time_status & STA_PPSFREQ) != 0 && 920 (time_status & STA_FREQHOLD) == 0) { 921 time_freq = pps_freq; 922 ntp_update_frequency(); 923 } 924 925 return delta; 926 } 927 928 /* correct REALTIME clock phase error against PPS signal */ 929 static void hardpps_update_phase(long error) 930 { 931 long correction = -error; 932 long jitter; 933 934 /* add the sample to the median filter */ 935 pps_phase_filter_add(correction); 936 correction = pps_phase_filter_get(&jitter); 937 938 /* Nominal jitter is due to PPS signal noise. If it exceeds the 939 * threshold, the sample is discarded; otherwise, if so enabled, 940 * the time offset is updated. 941 */ 942 if (jitter > (pps_jitter << PPS_POPCORN)) { 943 printk_deferred(KERN_WARNING 944 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 945 jitter, (pps_jitter << PPS_POPCORN)); 946 time_status |= STA_PPSJITTER; 947 pps_jitcnt++; 948 } else if (time_status & STA_PPSTIME) { 949 /* correct the time using the phase offset */ 950 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 951 NTP_INTERVAL_FREQ); 952 /* cancel running adjtime() */ 953 time_adjust = 0; 954 } 955 /* update jitter */ 956 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 957 } 958 959 /* 960 * __hardpps() - discipline CPU clock oscillator to external PPS signal 961 * 962 * This routine is called at each PPS signal arrival in order to 963 * discipline the CPU clock oscillator to the PPS signal. It takes two 964 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 965 * is used to correct clock phase error and the latter is used to 966 * correct the frequency. 967 * 968 * This code is based on David Mills's reference nanokernel 969 * implementation. It was mostly rewritten but keeps the same idea. 970 */ 971 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 972 { 973 struct pps_normtime pts_norm, freq_norm; 974 975 pts_norm = pps_normalize_ts(*phase_ts); 976 977 /* clear the error bits, they will be set again if needed */ 978 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 979 980 /* indicate signal presence */ 981 time_status |= STA_PPSSIGNAL; 982 pps_valid = PPS_VALID; 983 984 /* when called for the first time, 985 * just start the frequency interval */ 986 if (unlikely(pps_fbase.tv_sec == 0)) { 987 pps_fbase = *raw_ts; 988 return; 989 } 990 991 /* ok, now we have a base for frequency calculation */ 992 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 993 994 /* check that the signal is in the range 995 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 996 if ((freq_norm.sec == 0) || 997 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 998 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 999 time_status |= STA_PPSJITTER; 1000 /* restart the frequency calibration interval */ 1001 pps_fbase = *raw_ts; 1002 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 1003 return; 1004 } 1005 1006 /* signal is ok */ 1007 1008 /* check if the current frequency interval is finished */ 1009 if (freq_norm.sec >= (1 << pps_shift)) { 1010 pps_calcnt++; 1011 /* restart the frequency calibration interval */ 1012 pps_fbase = *raw_ts; 1013 hardpps_update_freq(freq_norm); 1014 } 1015 1016 hardpps_update_phase(pts_norm.nsec); 1017 1018 } 1019 #endif /* CONFIG_NTP_PPS */ 1020 1021 static int __init ntp_tick_adj_setup(char *str) 1022 { 1023 int rc = kstrtos64(str, 0, &ntp_tick_adj); 1024 if (rc) 1025 return rc; 1026 1027 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1028 return 1; 1029 } 1030 1031 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1032 1033 void __init ntp_init(void) 1034 { 1035 ntp_clear(); 1036 } 1037