1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * NTP state machine interfaces and logic. 4 * 5 * This code was mainly moved from kernel/timer.c and kernel/time.c 6 * Please see those files for relevant copyright info and historical 7 * changelogs. 8 */ 9 #include <linux/capability.h> 10 #include <linux/clocksource.h> 11 #include <linux/workqueue.h> 12 #include <linux/hrtimer.h> 13 #include <linux/jiffies.h> 14 #include <linux/math64.h> 15 #include <linux/timex.h> 16 #include <linux/time.h> 17 #include <linux/mm.h> 18 #include <linux/module.h> 19 #include <linux/rtc.h> 20 #include <linux/math64.h> 21 22 #include "ntp_internal.h" 23 #include "timekeeping_internal.h" 24 25 26 /* 27 * NTP timekeeping variables: 28 * 29 * Note: All of the NTP state is protected by the timekeeping locks. 30 */ 31 32 33 /* USER_HZ period (usecs): */ 34 unsigned long tick_usec = TICK_USEC; 35 36 /* SHIFTED_HZ period (nsecs): */ 37 unsigned long tick_nsec; 38 39 static u64 tick_length; 40 static u64 tick_length_base; 41 42 #define SECS_PER_DAY 86400 43 #define MAX_TICKADJ 500LL /* usecs */ 44 #define MAX_TICKADJ_SCALED \ 45 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) 46 47 /* 48 * phase-lock loop variables 49 */ 50 51 /* 52 * clock synchronization status 53 * 54 * (TIME_ERROR prevents overwriting the CMOS clock) 55 */ 56 static int time_state = TIME_OK; 57 58 /* clock status bits: */ 59 static int time_status = STA_UNSYNC; 60 61 /* time adjustment (nsecs): */ 62 static s64 time_offset; 63 64 /* pll time constant: */ 65 static long time_constant = 2; 66 67 /* maximum error (usecs): */ 68 static long time_maxerror = NTP_PHASE_LIMIT; 69 70 /* estimated error (usecs): */ 71 static long time_esterror = NTP_PHASE_LIMIT; 72 73 /* frequency offset (scaled nsecs/secs): */ 74 static s64 time_freq; 75 76 /* time at last adjustment (secs): */ 77 static time64_t time_reftime; 78 79 static long time_adjust; 80 81 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 82 static s64 ntp_tick_adj; 83 84 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */ 85 static time64_t ntp_next_leap_sec = TIME64_MAX; 86 87 #ifdef CONFIG_NTP_PPS 88 89 /* 90 * The following variables are used when a pulse-per-second (PPS) signal 91 * is available. They establish the engineering parameters of the clock 92 * discipline loop when controlled by the PPS signal. 93 */ 94 #define PPS_VALID 10 /* PPS signal watchdog max (s) */ 95 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 96 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 97 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 98 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to 99 increase pps_shift or consecutive bad 100 intervals to decrease it */ 101 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 102 103 static int pps_valid; /* signal watchdog counter */ 104 static long pps_tf[3]; /* phase median filter */ 105 static long pps_jitter; /* current jitter (ns) */ 106 static struct timespec64 pps_fbase; /* beginning of the last freq interval */ 107 static int pps_shift; /* current interval duration (s) (shift) */ 108 static int pps_intcnt; /* interval counter */ 109 static s64 pps_freq; /* frequency offset (scaled ns/s) */ 110 static long pps_stabil; /* current stability (scaled ns/s) */ 111 112 /* 113 * PPS signal quality monitors 114 */ 115 static long pps_calcnt; /* calibration intervals */ 116 static long pps_jitcnt; /* jitter limit exceeded */ 117 static long pps_stbcnt; /* stability limit exceeded */ 118 static long pps_errcnt; /* calibration errors */ 119 120 121 /* PPS kernel consumer compensates the whole phase error immediately. 122 * Otherwise, reduce the offset by a fixed factor times the time constant. 123 */ 124 static inline s64 ntp_offset_chunk(s64 offset) 125 { 126 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 127 return offset; 128 else 129 return shift_right(offset, SHIFT_PLL + time_constant); 130 } 131 132 static inline void pps_reset_freq_interval(void) 133 { 134 /* the PPS calibration interval may end 135 surprisingly early */ 136 pps_shift = PPS_INTMIN; 137 pps_intcnt = 0; 138 } 139 140 /** 141 * pps_clear - Clears the PPS state variables 142 */ 143 static inline void pps_clear(void) 144 { 145 pps_reset_freq_interval(); 146 pps_tf[0] = 0; 147 pps_tf[1] = 0; 148 pps_tf[2] = 0; 149 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 150 pps_freq = 0; 151 } 152 153 /* Decrease pps_valid to indicate that another second has passed since 154 * the last PPS signal. When it reaches 0, indicate that PPS signal is 155 * missing. 156 */ 157 static inline void pps_dec_valid(void) 158 { 159 if (pps_valid > 0) 160 pps_valid--; 161 else { 162 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 163 STA_PPSWANDER | STA_PPSERROR); 164 pps_clear(); 165 } 166 } 167 168 static inline void pps_set_freq(s64 freq) 169 { 170 pps_freq = freq; 171 } 172 173 static inline int is_error_status(int status) 174 { 175 return (status & (STA_UNSYNC|STA_CLOCKERR)) 176 /* PPS signal lost when either PPS time or 177 * PPS frequency synchronization requested 178 */ 179 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 180 && !(status & STA_PPSSIGNAL)) 181 /* PPS jitter exceeded when 182 * PPS time synchronization requested */ 183 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 184 == (STA_PPSTIME|STA_PPSJITTER)) 185 /* PPS wander exceeded or calibration error when 186 * PPS frequency synchronization requested 187 */ 188 || ((status & STA_PPSFREQ) 189 && (status & (STA_PPSWANDER|STA_PPSERROR))); 190 } 191 192 static inline void pps_fill_timex(struct timex *txc) 193 { 194 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 195 PPM_SCALE_INV, NTP_SCALE_SHIFT); 196 txc->jitter = pps_jitter; 197 if (!(time_status & STA_NANO)) 198 txc->jitter /= NSEC_PER_USEC; 199 txc->shift = pps_shift; 200 txc->stabil = pps_stabil; 201 txc->jitcnt = pps_jitcnt; 202 txc->calcnt = pps_calcnt; 203 txc->errcnt = pps_errcnt; 204 txc->stbcnt = pps_stbcnt; 205 } 206 207 #else /* !CONFIG_NTP_PPS */ 208 209 static inline s64 ntp_offset_chunk(s64 offset) 210 { 211 return shift_right(offset, SHIFT_PLL + time_constant); 212 } 213 214 static inline void pps_reset_freq_interval(void) {} 215 static inline void pps_clear(void) {} 216 static inline void pps_dec_valid(void) {} 217 static inline void pps_set_freq(s64 freq) {} 218 219 static inline int is_error_status(int status) 220 { 221 return status & (STA_UNSYNC|STA_CLOCKERR); 222 } 223 224 static inline void pps_fill_timex(struct timex *txc) 225 { 226 /* PPS is not implemented, so these are zero */ 227 txc->ppsfreq = 0; 228 txc->jitter = 0; 229 txc->shift = 0; 230 txc->stabil = 0; 231 txc->jitcnt = 0; 232 txc->calcnt = 0; 233 txc->errcnt = 0; 234 txc->stbcnt = 0; 235 } 236 237 #endif /* CONFIG_NTP_PPS */ 238 239 240 /** 241 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 242 * 243 */ 244 static inline int ntp_synced(void) 245 { 246 return !(time_status & STA_UNSYNC); 247 } 248 249 250 /* 251 * NTP methods: 252 */ 253 254 /* 255 * Update (tick_length, tick_length_base, tick_nsec), based 256 * on (tick_usec, ntp_tick_adj, time_freq): 257 */ 258 static void ntp_update_frequency(void) 259 { 260 u64 second_length; 261 u64 new_base; 262 263 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 264 << NTP_SCALE_SHIFT; 265 266 second_length += ntp_tick_adj; 267 second_length += time_freq; 268 269 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 270 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 271 272 /* 273 * Don't wait for the next second_overflow, apply 274 * the change to the tick length immediately: 275 */ 276 tick_length += new_base - tick_length_base; 277 tick_length_base = new_base; 278 } 279 280 static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 281 { 282 time_status &= ~STA_MODE; 283 284 if (secs < MINSEC) 285 return 0; 286 287 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 288 return 0; 289 290 time_status |= STA_MODE; 291 292 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 293 } 294 295 static void ntp_update_offset(long offset) 296 { 297 s64 freq_adj; 298 s64 offset64; 299 long secs; 300 301 if (!(time_status & STA_PLL)) 302 return; 303 304 if (!(time_status & STA_NANO)) { 305 /* Make sure the multiplication below won't overflow */ 306 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC); 307 offset *= NSEC_PER_USEC; 308 } 309 310 /* 311 * Scale the phase adjustment and 312 * clamp to the operating range. 313 */ 314 offset = clamp(offset, -MAXPHASE, MAXPHASE); 315 316 /* 317 * Select how the frequency is to be controlled 318 * and in which mode (PLL or FLL). 319 */ 320 secs = (long)(__ktime_get_real_seconds() - time_reftime); 321 if (unlikely(time_status & STA_FREQHOLD)) 322 secs = 0; 323 324 time_reftime = __ktime_get_real_seconds(); 325 326 offset64 = offset; 327 freq_adj = ntp_update_offset_fll(offset64, secs); 328 329 /* 330 * Clamp update interval to reduce PLL gain with low 331 * sampling rate (e.g. intermittent network connection) 332 * to avoid instability. 333 */ 334 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 335 secs = 1 << (SHIFT_PLL + 1 + time_constant); 336 337 freq_adj += (offset64 * secs) << 338 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 339 340 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 341 342 time_freq = max(freq_adj, -MAXFREQ_SCALED); 343 344 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 345 } 346 347 /** 348 * ntp_clear - Clears the NTP state variables 349 */ 350 void ntp_clear(void) 351 { 352 time_adjust = 0; /* stop active adjtime() */ 353 time_status |= STA_UNSYNC; 354 time_maxerror = NTP_PHASE_LIMIT; 355 time_esterror = NTP_PHASE_LIMIT; 356 357 ntp_update_frequency(); 358 359 tick_length = tick_length_base; 360 time_offset = 0; 361 362 ntp_next_leap_sec = TIME64_MAX; 363 /* Clear PPS state variables */ 364 pps_clear(); 365 } 366 367 368 u64 ntp_tick_length(void) 369 { 370 return tick_length; 371 } 372 373 /** 374 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t 375 * 376 * Provides the time of the next leapsecond against CLOCK_REALTIME in 377 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending. 378 */ 379 ktime_t ntp_get_next_leap(void) 380 { 381 ktime_t ret; 382 383 if ((time_state == TIME_INS) && (time_status & STA_INS)) 384 return ktime_set(ntp_next_leap_sec, 0); 385 ret = KTIME_MAX; 386 return ret; 387 } 388 389 /* 390 * this routine handles the overflow of the microsecond field 391 * 392 * The tricky bits of code to handle the accurate clock support 393 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 394 * They were originally developed for SUN and DEC kernels. 395 * All the kudos should go to Dave for this stuff. 396 * 397 * Also handles leap second processing, and returns leap offset 398 */ 399 int second_overflow(time64_t secs) 400 { 401 s64 delta; 402 int leap = 0; 403 s32 rem; 404 405 /* 406 * Leap second processing. If in leap-insert state at the end of the 407 * day, the system clock is set back one second; if in leap-delete 408 * state, the system clock is set ahead one second. 409 */ 410 switch (time_state) { 411 case TIME_OK: 412 if (time_status & STA_INS) { 413 time_state = TIME_INS; 414 div_s64_rem(secs, SECS_PER_DAY, &rem); 415 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 416 } else if (time_status & STA_DEL) { 417 time_state = TIME_DEL; 418 div_s64_rem(secs + 1, SECS_PER_DAY, &rem); 419 ntp_next_leap_sec = secs + SECS_PER_DAY - rem; 420 } 421 break; 422 case TIME_INS: 423 if (!(time_status & STA_INS)) { 424 ntp_next_leap_sec = TIME64_MAX; 425 time_state = TIME_OK; 426 } else if (secs == ntp_next_leap_sec) { 427 leap = -1; 428 time_state = TIME_OOP; 429 printk(KERN_NOTICE 430 "Clock: inserting leap second 23:59:60 UTC\n"); 431 } 432 break; 433 case TIME_DEL: 434 if (!(time_status & STA_DEL)) { 435 ntp_next_leap_sec = TIME64_MAX; 436 time_state = TIME_OK; 437 } else if (secs == ntp_next_leap_sec) { 438 leap = 1; 439 ntp_next_leap_sec = TIME64_MAX; 440 time_state = TIME_WAIT; 441 printk(KERN_NOTICE 442 "Clock: deleting leap second 23:59:59 UTC\n"); 443 } 444 break; 445 case TIME_OOP: 446 ntp_next_leap_sec = TIME64_MAX; 447 time_state = TIME_WAIT; 448 break; 449 case TIME_WAIT: 450 if (!(time_status & (STA_INS | STA_DEL))) 451 time_state = TIME_OK; 452 break; 453 } 454 455 456 /* Bump the maxerror field */ 457 time_maxerror += MAXFREQ / NSEC_PER_USEC; 458 if (time_maxerror > NTP_PHASE_LIMIT) { 459 time_maxerror = NTP_PHASE_LIMIT; 460 time_status |= STA_UNSYNC; 461 } 462 463 /* Compute the phase adjustment for the next second */ 464 tick_length = tick_length_base; 465 466 delta = ntp_offset_chunk(time_offset); 467 time_offset -= delta; 468 tick_length += delta; 469 470 /* Check PPS signal */ 471 pps_dec_valid(); 472 473 if (!time_adjust) 474 goto out; 475 476 if (time_adjust > MAX_TICKADJ) { 477 time_adjust -= MAX_TICKADJ; 478 tick_length += MAX_TICKADJ_SCALED; 479 goto out; 480 } 481 482 if (time_adjust < -MAX_TICKADJ) { 483 time_adjust += MAX_TICKADJ; 484 tick_length -= MAX_TICKADJ_SCALED; 485 goto out; 486 } 487 488 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) 489 << NTP_SCALE_SHIFT; 490 time_adjust = 0; 491 492 out: 493 return leap; 494 } 495 496 #ifdef CONFIG_GENERIC_CMOS_UPDATE 497 int __weak update_persistent_clock(struct timespec now) 498 { 499 return -ENODEV; 500 } 501 502 int __weak update_persistent_clock64(struct timespec64 now64) 503 { 504 struct timespec now; 505 506 now = timespec64_to_timespec(now64); 507 return update_persistent_clock(now); 508 } 509 #endif 510 511 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) 512 static void sync_cmos_clock(struct work_struct *work); 513 514 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); 515 516 static void sync_cmos_clock(struct work_struct *work) 517 { 518 struct timespec64 now; 519 struct timespec64 next; 520 int fail = 1; 521 522 /* 523 * If we have an externally synchronized Linux clock, then update 524 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be 525 * called as close as possible to 500 ms before the new second starts. 526 * This code is run on a timer. If the clock is set, that timer 527 * may not expire at the correct time. Thus, we adjust... 528 * We want the clock to be within a couple of ticks from the target. 529 */ 530 if (!ntp_synced()) { 531 /* 532 * Not synced, exit, do not restart a timer (if one is 533 * running, let it run out). 534 */ 535 return; 536 } 537 538 getnstimeofday64(&now); 539 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) { 540 struct timespec64 adjust = now; 541 542 fail = -ENODEV; 543 if (persistent_clock_is_local) 544 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 545 #ifdef CONFIG_GENERIC_CMOS_UPDATE 546 fail = update_persistent_clock64(adjust); 547 #endif 548 549 #ifdef CONFIG_RTC_SYSTOHC 550 if (fail == -ENODEV) 551 fail = rtc_set_ntp_time(adjust); 552 #endif 553 } 554 555 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); 556 if (next.tv_nsec <= 0) 557 next.tv_nsec += NSEC_PER_SEC; 558 559 if (!fail || fail == -ENODEV) 560 next.tv_sec = 659; 561 else 562 next.tv_sec = 0; 563 564 if (next.tv_nsec >= NSEC_PER_SEC) { 565 next.tv_sec++; 566 next.tv_nsec -= NSEC_PER_SEC; 567 } 568 queue_delayed_work(system_power_efficient_wq, 569 &sync_cmos_work, timespec64_to_jiffies(&next)); 570 } 571 572 void ntp_notify_cmos_timer(void) 573 { 574 queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0); 575 } 576 577 #else 578 void ntp_notify_cmos_timer(void) { } 579 #endif 580 581 582 /* 583 * Propagate a new txc->status value into the NTP state: 584 */ 585 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts) 586 { 587 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 588 time_state = TIME_OK; 589 time_status = STA_UNSYNC; 590 ntp_next_leap_sec = TIME64_MAX; 591 /* restart PPS frequency calibration */ 592 pps_reset_freq_interval(); 593 } 594 595 /* 596 * If we turn on PLL adjustments then reset the 597 * reference time to current time. 598 */ 599 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 600 time_reftime = __ktime_get_real_seconds(); 601 602 /* only set allowed bits */ 603 time_status &= STA_RONLY; 604 time_status |= txc->status & ~STA_RONLY; 605 } 606 607 608 static inline void process_adjtimex_modes(struct timex *txc, 609 struct timespec64 *ts, 610 s32 *time_tai) 611 { 612 if (txc->modes & ADJ_STATUS) 613 process_adj_status(txc, ts); 614 615 if (txc->modes & ADJ_NANO) 616 time_status |= STA_NANO; 617 618 if (txc->modes & ADJ_MICRO) 619 time_status &= ~STA_NANO; 620 621 if (txc->modes & ADJ_FREQUENCY) { 622 time_freq = txc->freq * PPM_SCALE; 623 time_freq = min(time_freq, MAXFREQ_SCALED); 624 time_freq = max(time_freq, -MAXFREQ_SCALED); 625 /* update pps_freq */ 626 pps_set_freq(time_freq); 627 } 628 629 if (txc->modes & ADJ_MAXERROR) 630 time_maxerror = txc->maxerror; 631 632 if (txc->modes & ADJ_ESTERROR) 633 time_esterror = txc->esterror; 634 635 if (txc->modes & ADJ_TIMECONST) { 636 time_constant = txc->constant; 637 if (!(time_status & STA_NANO)) 638 time_constant += 4; 639 time_constant = min(time_constant, (long)MAXTC); 640 time_constant = max(time_constant, 0l); 641 } 642 643 if (txc->modes & ADJ_TAI && txc->constant > 0) 644 *time_tai = txc->constant; 645 646 if (txc->modes & ADJ_OFFSET) 647 ntp_update_offset(txc->offset); 648 649 if (txc->modes & ADJ_TICK) 650 tick_usec = txc->tick; 651 652 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 653 ntp_update_frequency(); 654 } 655 656 657 658 /** 659 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex 660 */ 661 int ntp_validate_timex(struct timex *txc) 662 { 663 if (txc->modes & ADJ_ADJTIME) { 664 /* singleshot must not be used with any other mode bits */ 665 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT)) 666 return -EINVAL; 667 if (!(txc->modes & ADJ_OFFSET_READONLY) && 668 !capable(CAP_SYS_TIME)) 669 return -EPERM; 670 } else { 671 /* In order to modify anything, you gotta be super-user! */ 672 if (txc->modes && !capable(CAP_SYS_TIME)) 673 return -EPERM; 674 /* 675 * if the quartz is off by more than 10% then 676 * something is VERY wrong! 677 */ 678 if (txc->modes & ADJ_TICK && 679 (txc->tick < 900000/USER_HZ || 680 txc->tick > 1100000/USER_HZ)) 681 return -EINVAL; 682 } 683 684 if (txc->modes & ADJ_SETOFFSET) { 685 /* In order to inject time, you gotta be super-user! */ 686 if (!capable(CAP_SYS_TIME)) 687 return -EPERM; 688 689 if (txc->modes & ADJ_NANO) { 690 struct timespec ts; 691 692 ts.tv_sec = txc->time.tv_sec; 693 ts.tv_nsec = txc->time.tv_usec; 694 if (!timespec_inject_offset_valid(&ts)) 695 return -EINVAL; 696 697 } else { 698 if (!timeval_inject_offset_valid(&txc->time)) 699 return -EINVAL; 700 } 701 } 702 703 /* 704 * Check for potential multiplication overflows that can 705 * only happen on 64-bit systems: 706 */ 707 if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) { 708 if (LLONG_MIN / PPM_SCALE > txc->freq) 709 return -EINVAL; 710 if (LLONG_MAX / PPM_SCALE < txc->freq) 711 return -EINVAL; 712 } 713 714 return 0; 715 } 716 717 718 /* 719 * adjtimex mainly allows reading (and writing, if superuser) of 720 * kernel time-keeping variables. used by xntpd. 721 */ 722 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai) 723 { 724 int result; 725 726 if (txc->modes & ADJ_ADJTIME) { 727 long save_adjust = time_adjust; 728 729 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 730 /* adjtime() is independent from ntp_adjtime() */ 731 time_adjust = txc->offset; 732 ntp_update_frequency(); 733 } 734 txc->offset = save_adjust; 735 } else { 736 737 /* If there are input parameters, then process them: */ 738 if (txc->modes) 739 process_adjtimex_modes(txc, ts, time_tai); 740 741 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 742 NTP_SCALE_SHIFT); 743 if (!(time_status & STA_NANO)) 744 txc->offset /= NSEC_PER_USEC; 745 } 746 747 result = time_state; /* mostly `TIME_OK' */ 748 /* check for errors */ 749 if (is_error_status(time_status)) 750 result = TIME_ERROR; 751 752 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 753 PPM_SCALE_INV, NTP_SCALE_SHIFT); 754 txc->maxerror = time_maxerror; 755 txc->esterror = time_esterror; 756 txc->status = time_status; 757 txc->constant = time_constant; 758 txc->precision = 1; 759 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 760 txc->tick = tick_usec; 761 txc->tai = *time_tai; 762 763 /* fill PPS status fields */ 764 pps_fill_timex(txc); 765 766 txc->time.tv_sec = (time_t)ts->tv_sec; 767 txc->time.tv_usec = ts->tv_nsec; 768 if (!(time_status & STA_NANO)) 769 txc->time.tv_usec /= NSEC_PER_USEC; 770 771 /* Handle leapsec adjustments */ 772 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 773 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 774 result = TIME_OOP; 775 txc->tai++; 776 txc->time.tv_sec--; 777 } 778 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 779 result = TIME_WAIT; 780 txc->tai--; 781 txc->time.tv_sec++; 782 } 783 if ((time_state == TIME_OOP) && 784 (ts->tv_sec == ntp_next_leap_sec)) { 785 result = TIME_WAIT; 786 } 787 } 788 789 return result; 790 } 791 792 #ifdef CONFIG_NTP_PPS 793 794 /* actually struct pps_normtime is good old struct timespec, but it is 795 * semantically different (and it is the reason why it was invented): 796 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 797 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 798 struct pps_normtime { 799 s64 sec; /* seconds */ 800 long nsec; /* nanoseconds */ 801 }; 802 803 /* normalize the timestamp so that nsec is in the 804 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 805 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 806 { 807 struct pps_normtime norm = { 808 .sec = ts.tv_sec, 809 .nsec = ts.tv_nsec 810 }; 811 812 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 813 norm.nsec -= NSEC_PER_SEC; 814 norm.sec++; 815 } 816 817 return norm; 818 } 819 820 /* get current phase correction and jitter */ 821 static inline long pps_phase_filter_get(long *jitter) 822 { 823 *jitter = pps_tf[0] - pps_tf[1]; 824 if (*jitter < 0) 825 *jitter = -*jitter; 826 827 /* TODO: test various filters */ 828 return pps_tf[0]; 829 } 830 831 /* add the sample to the phase filter */ 832 static inline void pps_phase_filter_add(long err) 833 { 834 pps_tf[2] = pps_tf[1]; 835 pps_tf[1] = pps_tf[0]; 836 pps_tf[0] = err; 837 } 838 839 /* decrease frequency calibration interval length. 840 * It is halved after four consecutive unstable intervals. 841 */ 842 static inline void pps_dec_freq_interval(void) 843 { 844 if (--pps_intcnt <= -PPS_INTCOUNT) { 845 pps_intcnt = -PPS_INTCOUNT; 846 if (pps_shift > PPS_INTMIN) { 847 pps_shift--; 848 pps_intcnt = 0; 849 } 850 } 851 } 852 853 /* increase frequency calibration interval length. 854 * It is doubled after four consecutive stable intervals. 855 */ 856 static inline void pps_inc_freq_interval(void) 857 { 858 if (++pps_intcnt >= PPS_INTCOUNT) { 859 pps_intcnt = PPS_INTCOUNT; 860 if (pps_shift < PPS_INTMAX) { 861 pps_shift++; 862 pps_intcnt = 0; 863 } 864 } 865 } 866 867 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 868 * timestamps 869 * 870 * At the end of the calibration interval the difference between the 871 * first and last MONOTONIC_RAW clock timestamps divided by the length 872 * of the interval becomes the frequency update. If the interval was 873 * too long, the data are discarded. 874 * Returns the difference between old and new frequency values. 875 */ 876 static long hardpps_update_freq(struct pps_normtime freq_norm) 877 { 878 long delta, delta_mod; 879 s64 ftemp; 880 881 /* check if the frequency interval was too long */ 882 if (freq_norm.sec > (2 << pps_shift)) { 883 time_status |= STA_PPSERROR; 884 pps_errcnt++; 885 pps_dec_freq_interval(); 886 printk_deferred(KERN_ERR 887 "hardpps: PPSERROR: interval too long - %lld s\n", 888 freq_norm.sec); 889 return 0; 890 } 891 892 /* here the raw frequency offset and wander (stability) is 893 * calculated. If the wander is less than the wander threshold 894 * the interval is increased; otherwise it is decreased. 895 */ 896 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 897 freq_norm.sec); 898 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 899 pps_freq = ftemp; 900 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 901 printk_deferred(KERN_WARNING 902 "hardpps: PPSWANDER: change=%ld\n", delta); 903 time_status |= STA_PPSWANDER; 904 pps_stbcnt++; 905 pps_dec_freq_interval(); 906 } else { /* good sample */ 907 pps_inc_freq_interval(); 908 } 909 910 /* the stability metric is calculated as the average of recent 911 * frequency changes, but is used only for performance 912 * monitoring 913 */ 914 delta_mod = delta; 915 if (delta_mod < 0) 916 delta_mod = -delta_mod; 917 pps_stabil += (div_s64(((s64)delta_mod) << 918 (NTP_SCALE_SHIFT - SHIFT_USEC), 919 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 920 921 /* if enabled, the system clock frequency is updated */ 922 if ((time_status & STA_PPSFREQ) != 0 && 923 (time_status & STA_FREQHOLD) == 0) { 924 time_freq = pps_freq; 925 ntp_update_frequency(); 926 } 927 928 return delta; 929 } 930 931 /* correct REALTIME clock phase error against PPS signal */ 932 static void hardpps_update_phase(long error) 933 { 934 long correction = -error; 935 long jitter; 936 937 /* add the sample to the median filter */ 938 pps_phase_filter_add(correction); 939 correction = pps_phase_filter_get(&jitter); 940 941 /* Nominal jitter is due to PPS signal noise. If it exceeds the 942 * threshold, the sample is discarded; otherwise, if so enabled, 943 * the time offset is updated. 944 */ 945 if (jitter > (pps_jitter << PPS_POPCORN)) { 946 printk_deferred(KERN_WARNING 947 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 948 jitter, (pps_jitter << PPS_POPCORN)); 949 time_status |= STA_PPSJITTER; 950 pps_jitcnt++; 951 } else if (time_status & STA_PPSTIME) { 952 /* correct the time using the phase offset */ 953 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 954 NTP_INTERVAL_FREQ); 955 /* cancel running adjtime() */ 956 time_adjust = 0; 957 } 958 /* update jitter */ 959 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 960 } 961 962 /* 963 * __hardpps() - discipline CPU clock oscillator to external PPS signal 964 * 965 * This routine is called at each PPS signal arrival in order to 966 * discipline the CPU clock oscillator to the PPS signal. It takes two 967 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 968 * is used to correct clock phase error and the latter is used to 969 * correct the frequency. 970 * 971 * This code is based on David Mills's reference nanokernel 972 * implementation. It was mostly rewritten but keeps the same idea. 973 */ 974 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 975 { 976 struct pps_normtime pts_norm, freq_norm; 977 978 pts_norm = pps_normalize_ts(*phase_ts); 979 980 /* clear the error bits, they will be set again if needed */ 981 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 982 983 /* indicate signal presence */ 984 time_status |= STA_PPSSIGNAL; 985 pps_valid = PPS_VALID; 986 987 /* when called for the first time, 988 * just start the frequency interval */ 989 if (unlikely(pps_fbase.tv_sec == 0)) { 990 pps_fbase = *raw_ts; 991 return; 992 } 993 994 /* ok, now we have a base for frequency calculation */ 995 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 996 997 /* check that the signal is in the range 998 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 999 if ((freq_norm.sec == 0) || 1000 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 1001 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 1002 time_status |= STA_PPSJITTER; 1003 /* restart the frequency calibration interval */ 1004 pps_fbase = *raw_ts; 1005 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 1006 return; 1007 } 1008 1009 /* signal is ok */ 1010 1011 /* check if the current frequency interval is finished */ 1012 if (freq_norm.sec >= (1 << pps_shift)) { 1013 pps_calcnt++; 1014 /* restart the frequency calibration interval */ 1015 pps_fbase = *raw_ts; 1016 hardpps_update_freq(freq_norm); 1017 } 1018 1019 hardpps_update_phase(pts_norm.nsec); 1020 1021 } 1022 #endif /* CONFIG_NTP_PPS */ 1023 1024 static int __init ntp_tick_adj_setup(char *str) 1025 { 1026 int rc = kstrtol(str, 0, (long *)&ntp_tick_adj); 1027 1028 if (rc) 1029 return rc; 1030 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1031 1032 return 1; 1033 } 1034 1035 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1036 1037 void __init ntp_init(void) 1038 { 1039 ntp_clear(); 1040 } 1041