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 __kernel_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 = pps_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 __kernel_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 __kernel_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 __kernel_timex *txc, 660 s32 *time_tai) 661 { 662 if (txc->modes & ADJ_STATUS) 663 process_adj_status(txc); 664 665 if (txc->modes & ADJ_NANO) 666 time_status |= STA_NANO; 667 668 if (txc->modes & ADJ_MICRO) 669 time_status &= ~STA_NANO; 670 671 if (txc->modes & ADJ_FREQUENCY) { 672 time_freq = txc->freq * PPM_SCALE; 673 time_freq = min(time_freq, MAXFREQ_SCALED); 674 time_freq = max(time_freq, -MAXFREQ_SCALED); 675 /* update pps_freq */ 676 pps_set_freq(time_freq); 677 } 678 679 if (txc->modes & ADJ_MAXERROR) 680 time_maxerror = txc->maxerror; 681 682 if (txc->modes & ADJ_ESTERROR) 683 time_esterror = txc->esterror; 684 685 if (txc->modes & ADJ_TIMECONST) { 686 time_constant = txc->constant; 687 if (!(time_status & STA_NANO)) 688 time_constant += 4; 689 time_constant = min(time_constant, (long)MAXTC); 690 time_constant = max(time_constant, 0l); 691 } 692 693 if (txc->modes & ADJ_TAI && txc->constant > 0) 694 *time_tai = txc->constant; 695 696 if (txc->modes & ADJ_OFFSET) 697 ntp_update_offset(txc->offset); 698 699 if (txc->modes & ADJ_TICK) 700 tick_usec = txc->tick; 701 702 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 703 ntp_update_frequency(); 704 } 705 706 707 /* 708 * adjtimex mainly allows reading (and writing, if superuser) of 709 * kernel time-keeping variables. used by xntpd. 710 */ 711 int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts, 712 s32 *time_tai) 713 { 714 int result; 715 716 if (txc->modes & ADJ_ADJTIME) { 717 long save_adjust = time_adjust; 718 719 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 720 /* adjtime() is independent from ntp_adjtime() */ 721 time_adjust = txc->offset; 722 ntp_update_frequency(); 723 } 724 txc->offset = save_adjust; 725 } else { 726 727 /* If there are input parameters, then process them: */ 728 if (txc->modes) 729 process_adjtimex_modes(txc, time_tai); 730 731 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 732 NTP_SCALE_SHIFT); 733 if (!(time_status & STA_NANO)) 734 txc->offset = (u32)txc->offset / NSEC_PER_USEC; 735 } 736 737 result = time_state; /* mostly `TIME_OK' */ 738 /* check for errors */ 739 if (is_error_status(time_status)) 740 result = TIME_ERROR; 741 742 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 743 PPM_SCALE_INV, NTP_SCALE_SHIFT); 744 txc->maxerror = time_maxerror; 745 txc->esterror = time_esterror; 746 txc->status = time_status; 747 txc->constant = time_constant; 748 txc->precision = 1; 749 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 750 txc->tick = tick_usec; 751 txc->tai = *time_tai; 752 753 /* fill PPS status fields */ 754 pps_fill_timex(txc); 755 756 txc->time.tv_sec = (time_t)ts->tv_sec; 757 txc->time.tv_usec = ts->tv_nsec; 758 if (!(time_status & STA_NANO)) 759 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC; 760 761 /* Handle leapsec adjustments */ 762 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 763 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 764 result = TIME_OOP; 765 txc->tai++; 766 txc->time.tv_sec--; 767 } 768 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 769 result = TIME_WAIT; 770 txc->tai--; 771 txc->time.tv_sec++; 772 } 773 if ((time_state == TIME_OOP) && 774 (ts->tv_sec == ntp_next_leap_sec)) { 775 result = TIME_WAIT; 776 } 777 } 778 779 return result; 780 } 781 782 #ifdef CONFIG_NTP_PPS 783 784 /* actually struct pps_normtime is good old struct timespec, but it is 785 * semantically different (and it is the reason why it was invented): 786 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 787 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 788 struct pps_normtime { 789 s64 sec; /* seconds */ 790 long nsec; /* nanoseconds */ 791 }; 792 793 /* normalize the timestamp so that nsec is in the 794 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 795 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 796 { 797 struct pps_normtime norm = { 798 .sec = ts.tv_sec, 799 .nsec = ts.tv_nsec 800 }; 801 802 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 803 norm.nsec -= NSEC_PER_SEC; 804 norm.sec++; 805 } 806 807 return norm; 808 } 809 810 /* get current phase correction and jitter */ 811 static inline long pps_phase_filter_get(long *jitter) 812 { 813 *jitter = pps_tf[0] - pps_tf[1]; 814 if (*jitter < 0) 815 *jitter = -*jitter; 816 817 /* TODO: test various filters */ 818 return pps_tf[0]; 819 } 820 821 /* add the sample to the phase filter */ 822 static inline void pps_phase_filter_add(long err) 823 { 824 pps_tf[2] = pps_tf[1]; 825 pps_tf[1] = pps_tf[0]; 826 pps_tf[0] = err; 827 } 828 829 /* decrease frequency calibration interval length. 830 * It is halved after four consecutive unstable intervals. 831 */ 832 static inline void pps_dec_freq_interval(void) 833 { 834 if (--pps_intcnt <= -PPS_INTCOUNT) { 835 pps_intcnt = -PPS_INTCOUNT; 836 if (pps_shift > PPS_INTMIN) { 837 pps_shift--; 838 pps_intcnt = 0; 839 } 840 } 841 } 842 843 /* increase frequency calibration interval length. 844 * It is doubled after four consecutive stable intervals. 845 */ 846 static inline void pps_inc_freq_interval(void) 847 { 848 if (++pps_intcnt >= PPS_INTCOUNT) { 849 pps_intcnt = PPS_INTCOUNT; 850 if (pps_shift < PPS_INTMAX) { 851 pps_shift++; 852 pps_intcnt = 0; 853 } 854 } 855 } 856 857 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 858 * timestamps 859 * 860 * At the end of the calibration interval the difference between the 861 * first and last MONOTONIC_RAW clock timestamps divided by the length 862 * of the interval becomes the frequency update. If the interval was 863 * too long, the data are discarded. 864 * Returns the difference between old and new frequency values. 865 */ 866 static long hardpps_update_freq(struct pps_normtime freq_norm) 867 { 868 long delta, delta_mod; 869 s64 ftemp; 870 871 /* check if the frequency interval was too long */ 872 if (freq_norm.sec > (2 << pps_shift)) { 873 time_status |= STA_PPSERROR; 874 pps_errcnt++; 875 pps_dec_freq_interval(); 876 printk_deferred(KERN_ERR 877 "hardpps: PPSERROR: interval too long - %lld s\n", 878 freq_norm.sec); 879 return 0; 880 } 881 882 /* here the raw frequency offset and wander (stability) is 883 * calculated. If the wander is less than the wander threshold 884 * the interval is increased; otherwise it is decreased. 885 */ 886 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 887 freq_norm.sec); 888 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 889 pps_freq = ftemp; 890 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 891 printk_deferred(KERN_WARNING 892 "hardpps: PPSWANDER: change=%ld\n", delta); 893 time_status |= STA_PPSWANDER; 894 pps_stbcnt++; 895 pps_dec_freq_interval(); 896 } else { /* good sample */ 897 pps_inc_freq_interval(); 898 } 899 900 /* the stability metric is calculated as the average of recent 901 * frequency changes, but is used only for performance 902 * monitoring 903 */ 904 delta_mod = delta; 905 if (delta_mod < 0) 906 delta_mod = -delta_mod; 907 pps_stabil += (div_s64(((s64)delta_mod) << 908 (NTP_SCALE_SHIFT - SHIFT_USEC), 909 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 910 911 /* if enabled, the system clock frequency is updated */ 912 if ((time_status & STA_PPSFREQ) != 0 && 913 (time_status & STA_FREQHOLD) == 0) { 914 time_freq = pps_freq; 915 ntp_update_frequency(); 916 } 917 918 return delta; 919 } 920 921 /* correct REALTIME clock phase error against PPS signal */ 922 static void hardpps_update_phase(long error) 923 { 924 long correction = -error; 925 long jitter; 926 927 /* add the sample to the median filter */ 928 pps_phase_filter_add(correction); 929 correction = pps_phase_filter_get(&jitter); 930 931 /* Nominal jitter is due to PPS signal noise. If it exceeds the 932 * threshold, the sample is discarded; otherwise, if so enabled, 933 * the time offset is updated. 934 */ 935 if (jitter > (pps_jitter << PPS_POPCORN)) { 936 printk_deferred(KERN_WARNING 937 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 938 jitter, (pps_jitter << PPS_POPCORN)); 939 time_status |= STA_PPSJITTER; 940 pps_jitcnt++; 941 } else if (time_status & STA_PPSTIME) { 942 /* correct the time using the phase offset */ 943 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 944 NTP_INTERVAL_FREQ); 945 /* cancel running adjtime() */ 946 time_adjust = 0; 947 } 948 /* update jitter */ 949 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 950 } 951 952 /* 953 * __hardpps() - discipline CPU clock oscillator to external PPS signal 954 * 955 * This routine is called at each PPS signal arrival in order to 956 * discipline the CPU clock oscillator to the PPS signal. It takes two 957 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 958 * is used to correct clock phase error and the latter is used to 959 * correct the frequency. 960 * 961 * This code is based on David Mills's reference nanokernel 962 * implementation. It was mostly rewritten but keeps the same idea. 963 */ 964 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 965 { 966 struct pps_normtime pts_norm, freq_norm; 967 968 pts_norm = pps_normalize_ts(*phase_ts); 969 970 /* clear the error bits, they will be set again if needed */ 971 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 972 973 /* indicate signal presence */ 974 time_status |= STA_PPSSIGNAL; 975 pps_valid = PPS_VALID; 976 977 /* when called for the first time, 978 * just start the frequency interval */ 979 if (unlikely(pps_fbase.tv_sec == 0)) { 980 pps_fbase = *raw_ts; 981 return; 982 } 983 984 /* ok, now we have a base for frequency calculation */ 985 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 986 987 /* check that the signal is in the range 988 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 989 if ((freq_norm.sec == 0) || 990 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 991 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 992 time_status |= STA_PPSJITTER; 993 /* restart the frequency calibration interval */ 994 pps_fbase = *raw_ts; 995 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 996 return; 997 } 998 999 /* signal is ok */ 1000 1001 /* check if the current frequency interval is finished */ 1002 if (freq_norm.sec >= (1 << pps_shift)) { 1003 pps_calcnt++; 1004 /* restart the frequency calibration interval */ 1005 pps_fbase = *raw_ts; 1006 hardpps_update_freq(freq_norm); 1007 } 1008 1009 hardpps_update_phase(pts_norm.nsec); 1010 1011 } 1012 #endif /* CONFIG_NTP_PPS */ 1013 1014 static int __init ntp_tick_adj_setup(char *str) 1015 { 1016 int rc = kstrtos64(str, 0, &ntp_tick_adj); 1017 if (rc) 1018 return rc; 1019 1020 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1021 return 1; 1022 } 1023 1024 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1025 1026 void __init ntp_init(void) 1027 { 1028 ntp_clear(); 1029 } 1030