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/audit.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 #define MAX_TAI_OFFSET 100000 47 48 /* 49 * phase-lock loop variables 50 */ 51 52 /* 53 * clock synchronization status 54 * 55 * (TIME_ERROR prevents overwriting the CMOS clock) 56 */ 57 static int time_state = TIME_OK; 58 59 /* clock status bits: */ 60 static int time_status = STA_UNSYNC; 61 62 /* time adjustment (nsecs): */ 63 static s64 time_offset; 64 65 /* pll time constant: */ 66 static long time_constant = 2; 67 68 /* maximum error (usecs): */ 69 static long time_maxerror = NTP_PHASE_LIMIT; 70 71 /* estimated error (usecs): */ 72 static long time_esterror = NTP_PHASE_LIMIT; 73 74 /* frequency offset (scaled nsecs/secs): */ 75 static s64 time_freq; 76 77 /* time at last adjustment (secs): */ 78 static time64_t time_reftime; 79 80 static long time_adjust; 81 82 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 83 static s64 ntp_tick_adj; 84 85 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */ 86 static time64_t ntp_next_leap_sec = TIME64_MAX; 87 88 #ifdef CONFIG_NTP_PPS 89 90 /* 91 * The following variables are used when a pulse-per-second (PPS) signal 92 * is available. They establish the engineering parameters of the clock 93 * discipline loop when controlled by the PPS signal. 94 */ 95 #define PPS_VALID 10 /* PPS signal watchdog max (s) */ 96 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 97 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 98 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 99 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to 100 increase pps_shift or consecutive bad 101 intervals to decrease it */ 102 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 103 104 static int pps_valid; /* signal watchdog counter */ 105 static long pps_tf[3]; /* phase median filter */ 106 static long pps_jitter; /* current jitter (ns) */ 107 static struct timespec64 pps_fbase; /* beginning of the last freq interval */ 108 static int pps_shift; /* current interval duration (s) (shift) */ 109 static int pps_intcnt; /* interval counter */ 110 static s64 pps_freq; /* frequency offset (scaled ns/s) */ 111 static long pps_stabil; /* current stability (scaled ns/s) */ 112 113 /* 114 * PPS signal quality monitors 115 */ 116 static long pps_calcnt; /* calibration intervals */ 117 static long pps_jitcnt; /* jitter limit exceeded */ 118 static long pps_stbcnt; /* stability limit exceeded */ 119 static long pps_errcnt; /* calibration errors */ 120 121 122 /* PPS kernel consumer compensates the whole phase error immediately. 123 * Otherwise, reduce the offset by a fixed factor times the time constant. 124 */ 125 static inline s64 ntp_offset_chunk(s64 offset) 126 { 127 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 128 return offset; 129 else 130 return shift_right(offset, SHIFT_PLL + time_constant); 131 } 132 133 static inline void pps_reset_freq_interval(void) 134 { 135 /* the PPS calibration interval may end 136 surprisingly early */ 137 pps_shift = PPS_INTMIN; 138 pps_intcnt = 0; 139 } 140 141 /** 142 * pps_clear - Clears the PPS state variables 143 */ 144 static inline void pps_clear(void) 145 { 146 pps_reset_freq_interval(); 147 pps_tf[0] = 0; 148 pps_tf[1] = 0; 149 pps_tf[2] = 0; 150 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 151 pps_freq = 0; 152 } 153 154 /* Decrease pps_valid to indicate that another second has passed since 155 * the last PPS signal. When it reaches 0, indicate that PPS signal is 156 * missing. 157 */ 158 static inline void pps_dec_valid(void) 159 { 160 if (pps_valid > 0) 161 pps_valid--; 162 else { 163 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 164 STA_PPSWANDER | STA_PPSERROR); 165 pps_clear(); 166 } 167 } 168 169 static inline void pps_set_freq(s64 freq) 170 { 171 pps_freq = freq; 172 } 173 174 static inline int is_error_status(int status) 175 { 176 return (status & (STA_UNSYNC|STA_CLOCKERR)) 177 /* PPS signal lost when either PPS time or 178 * PPS frequency synchronization requested 179 */ 180 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 181 && !(status & STA_PPSSIGNAL)) 182 /* PPS jitter exceeded when 183 * PPS time synchronization requested */ 184 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 185 == (STA_PPSTIME|STA_PPSJITTER)) 186 /* PPS wander exceeded or calibration error when 187 * PPS frequency synchronization requested 188 */ 189 || ((status & STA_PPSFREQ) 190 && (status & (STA_PPSWANDER|STA_PPSERROR))); 191 } 192 193 static inline void pps_fill_timex(struct __kernel_timex *txc) 194 { 195 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 196 PPM_SCALE_INV, NTP_SCALE_SHIFT); 197 txc->jitter = pps_jitter; 198 if (!(time_status & STA_NANO)) 199 txc->jitter = pps_jitter / NSEC_PER_USEC; 200 txc->shift = pps_shift; 201 txc->stabil = pps_stabil; 202 txc->jitcnt = pps_jitcnt; 203 txc->calcnt = pps_calcnt; 204 txc->errcnt = pps_errcnt; 205 txc->stbcnt = pps_stbcnt; 206 } 207 208 #else /* !CONFIG_NTP_PPS */ 209 210 static inline s64 ntp_offset_chunk(s64 offset) 211 { 212 return shift_right(offset, SHIFT_PLL + time_constant); 213 } 214 215 static inline void pps_reset_freq_interval(void) {} 216 static inline void pps_clear(void) {} 217 static inline void pps_dec_valid(void) {} 218 static inline void pps_set_freq(s64 freq) {} 219 220 static inline int is_error_status(int status) 221 { 222 return status & (STA_UNSYNC|STA_CLOCKERR); 223 } 224 225 static inline void pps_fill_timex(struct __kernel_timex *txc) 226 { 227 /* PPS is not implemented, so these are zero */ 228 txc->ppsfreq = 0; 229 txc->jitter = 0; 230 txc->shift = 0; 231 txc->stabil = 0; 232 txc->jitcnt = 0; 233 txc->calcnt = 0; 234 txc->errcnt = 0; 235 txc->stbcnt = 0; 236 } 237 238 #endif /* CONFIG_NTP_PPS */ 239 240 241 /** 242 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 243 * 244 */ 245 static inline int ntp_synced(void) 246 { 247 return !(time_status & STA_UNSYNC); 248 } 249 250 251 /* 252 * NTP methods: 253 */ 254 255 /* 256 * Update (tick_length, tick_length_base, tick_nsec), based 257 * on (tick_usec, ntp_tick_adj, time_freq): 258 */ 259 static void ntp_update_frequency(void) 260 { 261 u64 second_length; 262 u64 new_base; 263 264 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 265 << NTP_SCALE_SHIFT; 266 267 second_length += ntp_tick_adj; 268 second_length += time_freq; 269 270 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 271 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 272 273 /* 274 * Don't wait for the next second_overflow, apply 275 * the change to the tick length immediately: 276 */ 277 tick_length += new_base - tick_length_base; 278 tick_length_base = new_base; 279 } 280 281 static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 282 { 283 time_status &= ~STA_MODE; 284 285 if (secs < MINSEC) 286 return 0; 287 288 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 289 return 0; 290 291 time_status |= STA_MODE; 292 293 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 294 } 295 296 static void ntp_update_offset(long offset) 297 { 298 s64 freq_adj; 299 s64 offset64; 300 long secs; 301 302 if (!(time_status & STA_PLL)) 303 return; 304 305 if (!(time_status & STA_NANO)) { 306 /* Make sure the multiplication below won't overflow */ 307 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC); 308 offset *= NSEC_PER_USEC; 309 } 310 311 /* 312 * Scale the phase adjustment and 313 * clamp to the operating range. 314 */ 315 offset = clamp(offset, -MAXPHASE, MAXPHASE); 316 317 /* 318 * Select how the frequency is to be controlled 319 * and in which mode (PLL or FLL). 320 */ 321 secs = (long)(__ktime_get_real_seconds() - time_reftime); 322 if (unlikely(time_status & STA_FREQHOLD)) 323 secs = 0; 324 325 time_reftime = __ktime_get_real_seconds(); 326 327 offset64 = offset; 328 freq_adj = ntp_update_offset_fll(offset64, secs); 329 330 /* 331 * Clamp update interval to reduce PLL gain with low 332 * sampling rate (e.g. intermittent network connection) 333 * to avoid instability. 334 */ 335 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 336 secs = 1 << (SHIFT_PLL + 1 + time_constant); 337 338 freq_adj += (offset64 * secs) << 339 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 340 341 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 342 343 time_freq = max(freq_adj, -MAXFREQ_SCALED); 344 345 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 346 } 347 348 /** 349 * ntp_clear - Clears the NTP state variables 350 */ 351 void ntp_clear(void) 352 { 353 time_adjust = 0; /* stop active adjtime() */ 354 time_status |= STA_UNSYNC; 355 time_maxerror = NTP_PHASE_LIMIT; 356 time_esterror = NTP_PHASE_LIMIT; 357 358 ntp_update_frequency(); 359 360 tick_length = tick_length_base; 361 time_offset = 0; 362 363 ntp_next_leap_sec = TIME64_MAX; 364 /* Clear PPS state variables */ 365 pps_clear(); 366 } 367 368 369 u64 ntp_tick_length(void) 370 { 371 return tick_length; 372 } 373 374 /** 375 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t 376 * 377 * Provides the time of the next leapsecond against CLOCK_REALTIME in 378 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending. 379 */ 380 ktime_t ntp_get_next_leap(void) 381 { 382 ktime_t ret; 383 384 if ((time_state == TIME_INS) && (time_status & STA_INS)) 385 return ktime_set(ntp_next_leap_sec, 0); 386 ret = KTIME_MAX; 387 return ret; 388 } 389 390 /* 391 * this routine handles the overflow of the microsecond field 392 * 393 * The tricky bits of code to handle the accurate clock support 394 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 395 * They were originally developed for SUN and DEC kernels. 396 * All the kudos should go to Dave for this stuff. 397 * 398 * Also handles leap second processing, and returns leap offset 399 */ 400 int second_overflow(time64_t secs) 401 { 402 s64 delta; 403 int leap = 0; 404 s32 rem; 405 406 /* 407 * Leap second processing. If in leap-insert state at the end of the 408 * day, the system clock is set back one second; if in leap-delete 409 * state, the system clock is set ahead one second. 410 */ 411 switch (time_state) { 412 case TIME_OK: 413 if (time_status & STA_INS) { 414 time_state = TIME_INS; 415 div_s64_rem(secs, SECS_PER_DAY, &rem); 416 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 417 } else if (time_status & STA_DEL) { 418 time_state = TIME_DEL; 419 div_s64_rem(secs + 1, SECS_PER_DAY, &rem); 420 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 421 } 422 break; 423 case TIME_INS: 424 if (!(time_status & STA_INS)) { 425 ntp_next_leap_sec = TIME64_MAX; 426 time_state = TIME_OK; 427 } else if (secs == ntp_next_leap_sec) { 428 leap = -1; 429 time_state = TIME_OOP; 430 printk(KERN_NOTICE 431 "Clock: inserting leap second 23:59:60 UTC\n"); 432 } 433 break; 434 case TIME_DEL: 435 if (!(time_status & STA_DEL)) { 436 ntp_next_leap_sec = TIME64_MAX; 437 time_state = TIME_OK; 438 } else if (secs == ntp_next_leap_sec) { 439 leap = 1; 440 ntp_next_leap_sec = TIME64_MAX; 441 time_state = TIME_WAIT; 442 printk(KERN_NOTICE 443 "Clock: deleting leap second 23:59:59 UTC\n"); 444 } 445 break; 446 case TIME_OOP: 447 ntp_next_leap_sec = TIME64_MAX; 448 time_state = TIME_WAIT; 449 break; 450 case TIME_WAIT: 451 if (!(time_status & (STA_INS | STA_DEL))) 452 time_state = TIME_OK; 453 break; 454 } 455 456 457 /* Bump the maxerror field */ 458 time_maxerror += MAXFREQ / NSEC_PER_USEC; 459 if (time_maxerror > NTP_PHASE_LIMIT) { 460 time_maxerror = NTP_PHASE_LIMIT; 461 time_status |= STA_UNSYNC; 462 } 463 464 /* Compute the phase adjustment for the next second */ 465 tick_length = tick_length_base; 466 467 delta = ntp_offset_chunk(time_offset); 468 time_offset -= delta; 469 tick_length += delta; 470 471 /* Check PPS signal */ 472 pps_dec_valid(); 473 474 if (!time_adjust) 475 goto out; 476 477 if (time_adjust > MAX_TICKADJ) { 478 time_adjust -= MAX_TICKADJ; 479 tick_length += MAX_TICKADJ_SCALED; 480 goto out; 481 } 482 483 if (time_adjust < -MAX_TICKADJ) { 484 time_adjust += MAX_TICKADJ; 485 tick_length -= MAX_TICKADJ_SCALED; 486 goto out; 487 } 488 489 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) 490 << NTP_SCALE_SHIFT; 491 time_adjust = 0; 492 493 out: 494 return leap; 495 } 496 497 static void sync_hw_clock(struct work_struct *work); 498 static DECLARE_DELAYED_WORK(sync_work, sync_hw_clock); 499 500 static void sched_sync_hw_clock(struct timespec64 now, 501 unsigned long target_nsec, bool fail) 502 503 { 504 struct timespec64 next; 505 506 ktime_get_real_ts64(&next); 507 if (!fail) 508 next.tv_sec = 659; 509 else { 510 /* 511 * Try again as soon as possible. Delaying long periods 512 * decreases the accuracy of the work queue timer. Due to this 513 * the algorithm is very likely to require a short-sleep retry 514 * after the above long sleep to synchronize ts_nsec. 515 */ 516 next.tv_sec = 0; 517 } 518 519 /* Compute the needed delay that will get to tv_nsec == target_nsec */ 520 next.tv_nsec = target_nsec - next.tv_nsec; 521 if (next.tv_nsec <= 0) 522 next.tv_nsec += NSEC_PER_SEC; 523 if (next.tv_nsec >= NSEC_PER_SEC) { 524 next.tv_sec++; 525 next.tv_nsec -= NSEC_PER_SEC; 526 } 527 528 queue_delayed_work(system_power_efficient_wq, &sync_work, 529 timespec64_to_jiffies(&next)); 530 } 531 532 static void sync_rtc_clock(void) 533 { 534 unsigned long target_nsec; 535 struct timespec64 adjust, now; 536 int rc; 537 538 if (!IS_ENABLED(CONFIG_RTC_SYSTOHC)) 539 return; 540 541 ktime_get_real_ts64(&now); 542 543 adjust = now; 544 if (persistent_clock_is_local) 545 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 546 547 /* 548 * The current RTC in use will provide the target_nsec it wants to be 549 * called at, and does rtc_tv_nsec_ok internally. 550 */ 551 rc = rtc_set_ntp_time(adjust, &target_nsec); 552 if (rc == -ENODEV) 553 return; 554 555 sched_sync_hw_clock(now, target_nsec, rc); 556 } 557 558 #ifdef CONFIG_GENERIC_CMOS_UPDATE 559 int __weak update_persistent_clock64(struct timespec64 now64) 560 { 561 return -ENODEV; 562 } 563 #endif 564 565 static bool sync_cmos_clock(void) 566 { 567 static bool no_cmos; 568 struct timespec64 now; 569 struct timespec64 adjust; 570 int rc = -EPROTO; 571 long target_nsec = NSEC_PER_SEC / 2; 572 573 if (!IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE)) 574 return false; 575 576 if (no_cmos) 577 return false; 578 579 /* 580 * Historically update_persistent_clock64() has followed x86 581 * semantics, which match the MC146818A/etc RTC. This RTC will store 582 * 'adjust' and then in .5s it will advance once second. 583 * 584 * Architectures are strongly encouraged to use rtclib and not 585 * implement this legacy API. 586 */ 587 ktime_get_real_ts64(&now); 588 if (rtc_tv_nsec_ok(-1 * target_nsec, &adjust, &now)) { 589 if (persistent_clock_is_local) 590 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 591 rc = update_persistent_clock64(adjust); 592 /* 593 * The machine does not support update_persistent_clock64 even 594 * though it defines CONFIG_GENERIC_CMOS_UPDATE. 595 */ 596 if (rc == -ENODEV) { 597 no_cmos = true; 598 return false; 599 } 600 } 601 602 sched_sync_hw_clock(now, target_nsec, rc); 603 return true; 604 } 605 606 /* 607 * If we have an externally synchronized Linux clock, then update RTC clock 608 * accordingly every ~11 minutes. Generally RTCs can only store second 609 * precision, but many RTCs will adjust the phase of their second tick to 610 * match the moment of update. This infrastructure arranges to call to the RTC 611 * set at the correct moment to phase synchronize the RTC second tick over 612 * with the kernel clock. 613 */ 614 static void sync_hw_clock(struct work_struct *work) 615 { 616 if (!ntp_synced()) 617 return; 618 619 if (sync_cmos_clock()) 620 return; 621 622 sync_rtc_clock(); 623 } 624 625 void ntp_notify_cmos_timer(void) 626 { 627 if (!ntp_synced()) 628 return; 629 630 if (IS_ENABLED(CONFIG_GENERIC_CMOS_UPDATE) || 631 IS_ENABLED(CONFIG_RTC_SYSTOHC)) 632 queue_delayed_work(system_power_efficient_wq, &sync_work, 0); 633 } 634 635 /* 636 * Propagate a new txc->status value into the NTP state: 637 */ 638 static inline void process_adj_status(const struct __kernel_timex *txc) 639 { 640 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 641 time_state = TIME_OK; 642 time_status = STA_UNSYNC; 643 ntp_next_leap_sec = TIME64_MAX; 644 /* restart PPS frequency calibration */ 645 pps_reset_freq_interval(); 646 } 647 648 /* 649 * If we turn on PLL adjustments then reset the 650 * reference time to current time. 651 */ 652 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 653 time_reftime = __ktime_get_real_seconds(); 654 655 /* only set allowed bits */ 656 time_status &= STA_RONLY; 657 time_status |= txc->status & ~STA_RONLY; 658 } 659 660 661 static inline void process_adjtimex_modes(const struct __kernel_timex *txc, 662 s32 *time_tai) 663 { 664 if (txc->modes & ADJ_STATUS) 665 process_adj_status(txc); 666 667 if (txc->modes & ADJ_NANO) 668 time_status |= STA_NANO; 669 670 if (txc->modes & ADJ_MICRO) 671 time_status &= ~STA_NANO; 672 673 if (txc->modes & ADJ_FREQUENCY) { 674 time_freq = txc->freq * PPM_SCALE; 675 time_freq = min(time_freq, MAXFREQ_SCALED); 676 time_freq = max(time_freq, -MAXFREQ_SCALED); 677 /* update pps_freq */ 678 pps_set_freq(time_freq); 679 } 680 681 if (txc->modes & ADJ_MAXERROR) 682 time_maxerror = txc->maxerror; 683 684 if (txc->modes & ADJ_ESTERROR) 685 time_esterror = txc->esterror; 686 687 if (txc->modes & ADJ_TIMECONST) { 688 time_constant = txc->constant; 689 if (!(time_status & STA_NANO)) 690 time_constant += 4; 691 time_constant = min(time_constant, (long)MAXTC); 692 time_constant = max(time_constant, 0l); 693 } 694 695 if (txc->modes & ADJ_TAI && 696 txc->constant >= 0 && txc->constant <= MAX_TAI_OFFSET) 697 *time_tai = txc->constant; 698 699 if (txc->modes & ADJ_OFFSET) 700 ntp_update_offset(txc->offset); 701 702 if (txc->modes & ADJ_TICK) 703 tick_usec = txc->tick; 704 705 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 706 ntp_update_frequency(); 707 } 708 709 710 /* 711 * adjtimex mainly allows reading (and writing, if superuser) of 712 * kernel time-keeping variables. used by xntpd. 713 */ 714 int __do_adjtimex(struct __kernel_timex *txc, const struct timespec64 *ts, 715 s32 *time_tai, struct audit_ntp_data *ad) 716 { 717 int result; 718 719 if (txc->modes & ADJ_ADJTIME) { 720 long save_adjust = time_adjust; 721 722 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 723 /* adjtime() is independent from ntp_adjtime() */ 724 time_adjust = txc->offset; 725 ntp_update_frequency(); 726 727 audit_ntp_set_old(ad, AUDIT_NTP_ADJUST, save_adjust); 728 audit_ntp_set_new(ad, AUDIT_NTP_ADJUST, time_adjust); 729 } 730 txc->offset = save_adjust; 731 } else { 732 /* If there are input parameters, then process them: */ 733 if (txc->modes) { 734 audit_ntp_set_old(ad, AUDIT_NTP_OFFSET, time_offset); 735 audit_ntp_set_old(ad, AUDIT_NTP_FREQ, time_freq); 736 audit_ntp_set_old(ad, AUDIT_NTP_STATUS, time_status); 737 audit_ntp_set_old(ad, AUDIT_NTP_TAI, *time_tai); 738 audit_ntp_set_old(ad, AUDIT_NTP_TICK, tick_usec); 739 740 process_adjtimex_modes(txc, time_tai); 741 742 audit_ntp_set_new(ad, AUDIT_NTP_OFFSET, time_offset); 743 audit_ntp_set_new(ad, AUDIT_NTP_FREQ, time_freq); 744 audit_ntp_set_new(ad, AUDIT_NTP_STATUS, time_status); 745 audit_ntp_set_new(ad, AUDIT_NTP_TAI, *time_tai); 746 audit_ntp_set_new(ad, AUDIT_NTP_TICK, tick_usec); 747 } 748 749 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 750 NTP_SCALE_SHIFT); 751 if (!(time_status & STA_NANO)) 752 txc->offset = (u32)txc->offset / NSEC_PER_USEC; 753 } 754 755 result = time_state; /* mostly `TIME_OK' */ 756 /* check for errors */ 757 if (is_error_status(time_status)) 758 result = TIME_ERROR; 759 760 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 761 PPM_SCALE_INV, NTP_SCALE_SHIFT); 762 txc->maxerror = time_maxerror; 763 txc->esterror = time_esterror; 764 txc->status = time_status; 765 txc->constant = time_constant; 766 txc->precision = 1; 767 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 768 txc->tick = tick_usec; 769 txc->tai = *time_tai; 770 771 /* fill PPS status fields */ 772 pps_fill_timex(txc); 773 774 txc->time.tv_sec = (time_t)ts->tv_sec; 775 txc->time.tv_usec = ts->tv_nsec; 776 if (!(time_status & STA_NANO)) 777 txc->time.tv_usec = ts->tv_nsec / NSEC_PER_USEC; 778 779 /* Handle leapsec adjustments */ 780 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 781 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 782 result = TIME_OOP; 783 txc->tai++; 784 txc->time.tv_sec--; 785 } 786 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 787 result = TIME_WAIT; 788 txc->tai--; 789 txc->time.tv_sec++; 790 } 791 if ((time_state == TIME_OOP) && 792 (ts->tv_sec == ntp_next_leap_sec)) { 793 result = TIME_WAIT; 794 } 795 } 796 797 return result; 798 } 799 800 #ifdef CONFIG_NTP_PPS 801 802 /* actually struct pps_normtime is good old struct timespec, but it is 803 * semantically different (and it is the reason why it was invented): 804 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 805 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 806 struct pps_normtime { 807 s64 sec; /* seconds */ 808 long nsec; /* nanoseconds */ 809 }; 810 811 /* normalize the timestamp so that nsec is in the 812 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 813 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 814 { 815 struct pps_normtime norm = { 816 .sec = ts.tv_sec, 817 .nsec = ts.tv_nsec 818 }; 819 820 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 821 norm.nsec -= NSEC_PER_SEC; 822 norm.sec++; 823 } 824 825 return norm; 826 } 827 828 /* get current phase correction and jitter */ 829 static inline long pps_phase_filter_get(long *jitter) 830 { 831 *jitter = pps_tf[0] - pps_tf[1]; 832 if (*jitter < 0) 833 *jitter = -*jitter; 834 835 /* TODO: test various filters */ 836 return pps_tf[0]; 837 } 838 839 /* add the sample to the phase filter */ 840 static inline void pps_phase_filter_add(long err) 841 { 842 pps_tf[2] = pps_tf[1]; 843 pps_tf[1] = pps_tf[0]; 844 pps_tf[0] = err; 845 } 846 847 /* decrease frequency calibration interval length. 848 * It is halved after four consecutive unstable intervals. 849 */ 850 static inline void pps_dec_freq_interval(void) 851 { 852 if (--pps_intcnt <= -PPS_INTCOUNT) { 853 pps_intcnt = -PPS_INTCOUNT; 854 if (pps_shift > PPS_INTMIN) { 855 pps_shift--; 856 pps_intcnt = 0; 857 } 858 } 859 } 860 861 /* increase frequency calibration interval length. 862 * It is doubled after four consecutive stable intervals. 863 */ 864 static inline void pps_inc_freq_interval(void) 865 { 866 if (++pps_intcnt >= PPS_INTCOUNT) { 867 pps_intcnt = PPS_INTCOUNT; 868 if (pps_shift < PPS_INTMAX) { 869 pps_shift++; 870 pps_intcnt = 0; 871 } 872 } 873 } 874 875 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 876 * timestamps 877 * 878 * At the end of the calibration interval the difference between the 879 * first and last MONOTONIC_RAW clock timestamps divided by the length 880 * of the interval becomes the frequency update. If the interval was 881 * too long, the data are discarded. 882 * Returns the difference between old and new frequency values. 883 */ 884 static long hardpps_update_freq(struct pps_normtime freq_norm) 885 { 886 long delta, delta_mod; 887 s64 ftemp; 888 889 /* check if the frequency interval was too long */ 890 if (freq_norm.sec > (2 << pps_shift)) { 891 time_status |= STA_PPSERROR; 892 pps_errcnt++; 893 pps_dec_freq_interval(); 894 printk_deferred(KERN_ERR 895 "hardpps: PPSERROR: interval too long - %lld s\n", 896 freq_norm.sec); 897 return 0; 898 } 899 900 /* here the raw frequency offset and wander (stability) is 901 * calculated. If the wander is less than the wander threshold 902 * the interval is increased; otherwise it is decreased. 903 */ 904 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 905 freq_norm.sec); 906 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 907 pps_freq = ftemp; 908 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 909 printk_deferred(KERN_WARNING 910 "hardpps: PPSWANDER: change=%ld\n", delta); 911 time_status |= STA_PPSWANDER; 912 pps_stbcnt++; 913 pps_dec_freq_interval(); 914 } else { /* good sample */ 915 pps_inc_freq_interval(); 916 } 917 918 /* the stability metric is calculated as the average of recent 919 * frequency changes, but is used only for performance 920 * monitoring 921 */ 922 delta_mod = delta; 923 if (delta_mod < 0) 924 delta_mod = -delta_mod; 925 pps_stabil += (div_s64(((s64)delta_mod) << 926 (NTP_SCALE_SHIFT - SHIFT_USEC), 927 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 928 929 /* if enabled, the system clock frequency is updated */ 930 if ((time_status & STA_PPSFREQ) != 0 && 931 (time_status & STA_FREQHOLD) == 0) { 932 time_freq = pps_freq; 933 ntp_update_frequency(); 934 } 935 936 return delta; 937 } 938 939 /* correct REALTIME clock phase error against PPS signal */ 940 static void hardpps_update_phase(long error) 941 { 942 long correction = -error; 943 long jitter; 944 945 /* add the sample to the median filter */ 946 pps_phase_filter_add(correction); 947 correction = pps_phase_filter_get(&jitter); 948 949 /* Nominal jitter is due to PPS signal noise. If it exceeds the 950 * threshold, the sample is discarded; otherwise, if so enabled, 951 * the time offset is updated. 952 */ 953 if (jitter > (pps_jitter << PPS_POPCORN)) { 954 printk_deferred(KERN_WARNING 955 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 956 jitter, (pps_jitter << PPS_POPCORN)); 957 time_status |= STA_PPSJITTER; 958 pps_jitcnt++; 959 } else if (time_status & STA_PPSTIME) { 960 /* correct the time using the phase offset */ 961 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 962 NTP_INTERVAL_FREQ); 963 /* cancel running adjtime() */ 964 time_adjust = 0; 965 } 966 /* update jitter */ 967 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 968 } 969 970 /* 971 * __hardpps() - discipline CPU clock oscillator to external PPS signal 972 * 973 * This routine is called at each PPS signal arrival in order to 974 * discipline the CPU clock oscillator to the PPS signal. It takes two 975 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 976 * is used to correct clock phase error and the latter is used to 977 * correct the frequency. 978 * 979 * This code is based on David Mills's reference nanokernel 980 * implementation. It was mostly rewritten but keeps the same idea. 981 */ 982 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 983 { 984 struct pps_normtime pts_norm, freq_norm; 985 986 pts_norm = pps_normalize_ts(*phase_ts); 987 988 /* clear the error bits, they will be set again if needed */ 989 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 990 991 /* indicate signal presence */ 992 time_status |= STA_PPSSIGNAL; 993 pps_valid = PPS_VALID; 994 995 /* when called for the first time, 996 * just start the frequency interval */ 997 if (unlikely(pps_fbase.tv_sec == 0)) { 998 pps_fbase = *raw_ts; 999 return; 1000 } 1001 1002 /* ok, now we have a base for frequency calculation */ 1003 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 1004 1005 /* check that the signal is in the range 1006 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 1007 if ((freq_norm.sec == 0) || 1008 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 1009 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 1010 time_status |= STA_PPSJITTER; 1011 /* restart the frequency calibration interval */ 1012 pps_fbase = *raw_ts; 1013 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 1014 return; 1015 } 1016 1017 /* signal is ok */ 1018 1019 /* check if the current frequency interval is finished */ 1020 if (freq_norm.sec >= (1 << pps_shift)) { 1021 pps_calcnt++; 1022 /* restart the frequency calibration interval */ 1023 pps_fbase = *raw_ts; 1024 hardpps_update_freq(freq_norm); 1025 } 1026 1027 hardpps_update_phase(pts_norm.nsec); 1028 1029 } 1030 #endif /* CONFIG_NTP_PPS */ 1031 1032 static int __init ntp_tick_adj_setup(char *str) 1033 { 1034 int rc = kstrtos64(str, 0, &ntp_tick_adj); 1035 if (rc) 1036 return rc; 1037 1038 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1039 return 1; 1040 } 1041 1042 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1043 1044 void __init ntp_init(void) 1045 { 1046 ntp_clear(); 1047 } 1048