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