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_clock64(struct timespec64 now64) 558 { 559 return -ENODEV; 560 } 561 #endif 562 563 static bool sync_cmos_clock(void) 564 { 565 static bool no_cmos; 566 struct timespec64 now; 567 struct timespec64 adjust; 568 int rc = -EPROTO; 569 long target_nsec = NSEC_PER_SEC / 2; 570 571 if (!IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE)) 572 return false; 573 574 if (no_cmos) 575 return false; 576 577 /* 578 * Historically update_persistent_clock64() has followed x86 579 * semantics, which match the MC146818A/etc RTC. This RTC will store 580 * 'adjust' and then in .5s it will advance once second. 581 * 582 * Architectures are strongly encouraged to use rtclib and not 583 * implement this legacy API. 584 */ 585 ktime_get_real_ts64(&now); 586 if (rtc_tv_nsec_ok(-1 * target_nsec, &adjust, &now)) { 587 if (persistent_clock_is_local) 588 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 589 rc = update_persistent_clock64(adjust); 590 /* 591 * The machine does not support update_persistent_clock64 even 592 * though it defines CONFIG_GENERIC_CMOS_UPDATE. 593 */ 594 if (rc == -ENODEV) { 595 no_cmos = true; 596 return false; 597 } 598 } 599 600 sched_sync_hw_clock(now, target_nsec, rc); 601 return true; 602 } 603 604 /* 605 * If we have an externally synchronized Linux clock, then update RTC clock 606 * accordingly every ~11 minutes. Generally RTCs can only store second 607 * precision, but many RTCs will adjust the phase of their second tick to 608 * match the moment of update. This infrastructure arranges to call to the RTC 609 * set at the correct moment to phase synchronize the RTC second tick over 610 * with the kernel clock. 611 */ 612 static void sync_hw_clock(struct work_struct *work) 613 { 614 if (!ntp_synced()) 615 return; 616 617 if (sync_cmos_clock()) 618 return; 619 620 sync_rtc_clock(); 621 } 622 623 void ntp_notify_cmos_timer(void) 624 { 625 if (!ntp_synced()) 626 return; 627 628 if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) || 629 IS_ENABLED(CONFIG_RTC_SYSTOHC)) 630 queue_delayed_work(system_power_efficient_wq, &sync_work, 0); 631 } 632 633 /* 634 * Propagate a new txc->status value into the NTP state: 635 */ 636 static inline void process_adj_status(const struct timex *txc) 637 { 638 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 639 time_state = TIME_OK; 640 time_status = STA_UNSYNC; 641 ntp_next_leap_sec = TIME64_MAX; 642 /* restart PPS frequency calibration */ 643 pps_reset_freq_interval(); 644 } 645 646 /* 647 * If we turn on PLL adjustments then reset the 648 * reference time to current time. 649 */ 650 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 651 time_reftime = __ktime_get_real_seconds(); 652 653 /* only set allowed bits */ 654 time_status &= STA_RONLY; 655 time_status |= txc->status & ~STA_RONLY; 656 } 657 658 659 static inline void process_adjtimex_modes(const struct timex *txc, s32 *time_tai) 660 { 661 if (txc->modes & ADJ_STATUS) 662 process_adj_status(txc); 663 664 if (txc->modes & ADJ_NANO) 665 time_status |= STA_NANO; 666 667 if (txc->modes & ADJ_MICRO) 668 time_status &= ~STA_NANO; 669 670 if (txc->modes & ADJ_FREQUENCY) { 671 time_freq = txc->freq * PPM_SCALE; 672 time_freq = min(time_freq, MAXFREQ_SCALED); 673 time_freq = max(time_freq, -MAXFREQ_SCALED); 674 /* update pps_freq */ 675 pps_set_freq(time_freq); 676 } 677 678 if (txc->modes & ADJ_MAXERROR) 679 time_maxerror = txc->maxerror; 680 681 if (txc->modes & ADJ_ESTERROR) 682 time_esterror = txc->esterror; 683 684 if (txc->modes & ADJ_TIMECONST) { 685 time_constant = txc->constant; 686 if (!(time_status & STA_NANO)) 687 time_constant += 4; 688 time_constant = min(time_constant, (long)MAXTC); 689 time_constant = max(time_constant, 0l); 690 } 691 692 if (txc->modes & ADJ_TAI && txc->constant > 0) 693 *time_tai = txc->constant; 694 695 if (txc->modes & ADJ_OFFSET) 696 ntp_update_offset(txc->offset); 697 698 if (txc->modes & ADJ_TICK) 699 tick_usec = txc->tick; 700 701 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 702 ntp_update_frequency(); 703 } 704 705 706 /* 707 * adjtimex mainly allows reading (and writing, if superuser) of 708 * kernel time-keeping variables. used by xntpd. 709 */ 710 int __do_adjtimex(struct timex *txc, const struct timespec64 *ts, s32 *time_tai) 711 { 712 int result; 713 714 if (txc->modes & ADJ_ADJTIME) { 715 long save_adjust = time_adjust; 716 717 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 718 /* adjtime() is independent from ntp_adjtime() */ 719 time_adjust = txc->offset; 720 ntp_update_frequency(); 721 } 722 txc->offset = save_adjust; 723 } else { 724 725 /* If there are input parameters, then process them: */ 726 if (txc->modes) 727 process_adjtimex_modes(txc, time_tai); 728 729 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 730 NTP_SCALE_SHIFT); 731 if (!(time_status & STA_NANO)) 732 txc->offset /= NSEC_PER_USEC; 733 } 734 735 result = time_state; /* mostly `TIME_OK' */ 736 /* check for errors */ 737 if (is_error_status(time_status)) 738 result = TIME_ERROR; 739 740 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 741 PPM_SCALE_INV, NTP_SCALE_SHIFT); 742 txc->maxerror = time_maxerror; 743 txc->esterror = time_esterror; 744 txc->status = time_status; 745 txc->constant = time_constant; 746 txc->precision = 1; 747 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 748 txc->tick = tick_usec; 749 txc->tai = *time_tai; 750 751 /* fill PPS status fields */ 752 pps_fill_timex(txc); 753 754 txc->time.tv_sec = (time_t)ts->tv_sec; 755 txc->time.tv_usec = ts->tv_nsec; 756 if (!(time_status & STA_NANO)) 757 txc->time.tv_usec /= NSEC_PER_USEC; 758 759 /* Handle leapsec adjustments */ 760 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 761 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 762 result = TIME_OOP; 763 txc->tai++; 764 txc->time.tv_sec--; 765 } 766 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 767 result = TIME_WAIT; 768 txc->tai--; 769 txc->time.tv_sec++; 770 } 771 if ((time_state == TIME_OOP) && 772 (ts->tv_sec == ntp_next_leap_sec)) { 773 result = TIME_WAIT; 774 } 775 } 776 777 return result; 778 } 779 780 #ifdef CONFIG_NTP_PPS 781 782 /* actually struct pps_normtime is good old struct timespec, but it is 783 * semantically different (and it is the reason why it was invented): 784 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 785 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 786 struct pps_normtime { 787 s64 sec; /* seconds */ 788 long nsec; /* nanoseconds */ 789 }; 790 791 /* normalize the timestamp so that nsec is in the 792 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 793 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 794 { 795 struct pps_normtime norm = { 796 .sec = ts.tv_sec, 797 .nsec = ts.tv_nsec 798 }; 799 800 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 801 norm.nsec -= NSEC_PER_SEC; 802 norm.sec++; 803 } 804 805 return norm; 806 } 807 808 /* get current phase correction and jitter */ 809 static inline long pps_phase_filter_get(long *jitter) 810 { 811 *jitter = pps_tf[0] - pps_tf[1]; 812 if (*jitter < 0) 813 *jitter = -*jitter; 814 815 /* TODO: test various filters */ 816 return pps_tf[0]; 817 } 818 819 /* add the sample to the phase filter */ 820 static inline void pps_phase_filter_add(long err) 821 { 822 pps_tf[2] = pps_tf[1]; 823 pps_tf[1] = pps_tf[0]; 824 pps_tf[0] = err; 825 } 826 827 /* decrease frequency calibration interval length. 828 * It is halved after four consecutive unstable intervals. 829 */ 830 static inline void pps_dec_freq_interval(void) 831 { 832 if (--pps_intcnt <= -PPS_INTCOUNT) { 833 pps_intcnt = -PPS_INTCOUNT; 834 if (pps_shift > PPS_INTMIN) { 835 pps_shift--; 836 pps_intcnt = 0; 837 } 838 } 839 } 840 841 /* increase frequency calibration interval length. 842 * It is doubled after four consecutive stable intervals. 843 */ 844 static inline void pps_inc_freq_interval(void) 845 { 846 if (++pps_intcnt >= PPS_INTCOUNT) { 847 pps_intcnt = PPS_INTCOUNT; 848 if (pps_shift < PPS_INTMAX) { 849 pps_shift++; 850 pps_intcnt = 0; 851 } 852 } 853 } 854 855 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 856 * timestamps 857 * 858 * At the end of the calibration interval the difference between the 859 * first and last MONOTONIC_RAW clock timestamps divided by the length 860 * of the interval becomes the frequency update. If the interval was 861 * too long, the data are discarded. 862 * Returns the difference between old and new frequency values. 863 */ 864 static long hardpps_update_freq(struct pps_normtime freq_norm) 865 { 866 long delta, delta_mod; 867 s64 ftemp; 868 869 /* check if the frequency interval was too long */ 870 if (freq_norm.sec > (2 << pps_shift)) { 871 time_status |= STA_PPSERROR; 872 pps_errcnt++; 873 pps_dec_freq_interval(); 874 printk_deferred(KERN_ERR 875 "hardpps: PPSERROR: interval too long - %lld s\n", 876 freq_norm.sec); 877 return 0; 878 } 879 880 /* here the raw frequency offset and wander (stability) is 881 * calculated. If the wander is less than the wander threshold 882 * the interval is increased; otherwise it is decreased. 883 */ 884 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 885 freq_norm.sec); 886 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 887 pps_freq = ftemp; 888 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 889 printk_deferred(KERN_WARNING 890 "hardpps: PPSWANDER: change=%ld\n", delta); 891 time_status |= STA_PPSWANDER; 892 pps_stbcnt++; 893 pps_dec_freq_interval(); 894 } else { /* good sample */ 895 pps_inc_freq_interval(); 896 } 897 898 /* the stability metric is calculated as the average of recent 899 * frequency changes, but is used only for performance 900 * monitoring 901 */ 902 delta_mod = delta; 903 if (delta_mod < 0) 904 delta_mod = -delta_mod; 905 pps_stabil += (div_s64(((s64)delta_mod) << 906 (NTP_SCALE_SHIFT - SHIFT_USEC), 907 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 908 909 /* if enabled, the system clock frequency is updated */ 910 if ((time_status & STA_PPSFREQ) != 0 && 911 (time_status & STA_FREQHOLD) == 0) { 912 time_freq = pps_freq; 913 ntp_update_frequency(); 914 } 915 916 return delta; 917 } 918 919 /* correct REALTIME clock phase error against PPS signal */ 920 static void hardpps_update_phase(long error) 921 { 922 long correction = -error; 923 long jitter; 924 925 /* add the sample to the median filter */ 926 pps_phase_filter_add(correction); 927 correction = pps_phase_filter_get(&jitter); 928 929 /* Nominal jitter is due to PPS signal noise. If it exceeds the 930 * threshold, the sample is discarded; otherwise, if so enabled, 931 * the time offset is updated. 932 */ 933 if (jitter > (pps_jitter << PPS_POPCORN)) { 934 printk_deferred(KERN_WARNING 935 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 936 jitter, (pps_jitter << PPS_POPCORN)); 937 time_status |= STA_PPSJITTER; 938 pps_jitcnt++; 939 } else if (time_status & STA_PPSTIME) { 940 /* correct the time using the phase offset */ 941 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 942 NTP_INTERVAL_FREQ); 943 /* cancel running adjtime() */ 944 time_adjust = 0; 945 } 946 /* update jitter */ 947 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 948 } 949 950 /* 951 * __hardpps() - discipline CPU clock oscillator to external PPS signal 952 * 953 * This routine is called at each PPS signal arrival in order to 954 * discipline the CPU clock oscillator to the PPS signal. It takes two 955 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 956 * is used to correct clock phase error and the latter is used to 957 * correct the frequency. 958 * 959 * This code is based on David Mills's reference nanokernel 960 * implementation. It was mostly rewritten but keeps the same idea. 961 */ 962 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 963 { 964 struct pps_normtime pts_norm, freq_norm; 965 966 pts_norm = pps_normalize_ts(*phase_ts); 967 968 /* clear the error bits, they will be set again if needed */ 969 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 970 971 /* indicate signal presence */ 972 time_status |= STA_PPSSIGNAL; 973 pps_valid = PPS_VALID; 974 975 /* when called for the first time, 976 * just start the frequency interval */ 977 if (unlikely(pps_fbase.tv_sec == 0)) { 978 pps_fbase = *raw_ts; 979 return; 980 } 981 982 /* ok, now we have a base for frequency calculation */ 983 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 984 985 /* check that the signal is in the range 986 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 987 if ((freq_norm.sec == 0) || 988 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 989 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 990 time_status |= STA_PPSJITTER; 991 /* restart the frequency calibration interval */ 992 pps_fbase = *raw_ts; 993 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 994 return; 995 } 996 997 /* signal is ok */ 998 999 /* check if the current frequency interval is finished */ 1000 if (freq_norm.sec >= (1 << pps_shift)) { 1001 pps_calcnt++; 1002 /* restart the frequency calibration interval */ 1003 pps_fbase = *raw_ts; 1004 hardpps_update_freq(freq_norm); 1005 } 1006 1007 hardpps_update_phase(pts_norm.nsec); 1008 1009 } 1010 #endif /* CONFIG_NTP_PPS */ 1011 1012 static int __init ntp_tick_adj_setup(char *str) 1013 { 1014 int rc = kstrtos64(str, 0, &ntp_tick_adj); 1015 if (rc) 1016 return rc; 1017 1018 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1019 return 1; 1020 } 1021 1022 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1023 1024 void __init ntp_init(void) 1025 { 1026 ntp_clear(); 1027 } 1028