1 /* 2 * NTP state machine interfaces and logic. 3 * 4 * This code was mainly moved from kernel/timer.c and kernel/time.c 5 * Please see those files for relevant copyright info and historical 6 * changelogs. 7 */ 8 #include <linux/capability.h> 9 #include <linux/clocksource.h> 10 #include <linux/workqueue.h> 11 #include <linux/hrtimer.h> 12 #include <linux/jiffies.h> 13 #include <linux/math64.h> 14 #include <linux/timex.h> 15 #include <linux/time.h> 16 #include <linux/mm.h> 17 #include <linux/module.h> 18 #include <linux/rtc.h> 19 20 #include "ntp_internal.h" 21 22 /* 23 * NTP timekeeping variables: 24 * 25 * Note: All of the NTP state is protected by the timekeeping locks. 26 */ 27 28 29 /* USER_HZ period (usecs): */ 30 unsigned long tick_usec = TICK_USEC; 31 32 /* SHIFTED_HZ period (nsecs): */ 33 unsigned long tick_nsec; 34 35 static u64 tick_length; 36 static u64 tick_length_base; 37 38 #define SECS_PER_DAY 86400 39 #define MAX_TICKADJ 500LL /* usecs */ 40 #define MAX_TICKADJ_SCALED \ 41 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) 42 43 /* 44 * phase-lock loop variables 45 */ 46 47 /* 48 * clock synchronization status 49 * 50 * (TIME_ERROR prevents overwriting the CMOS clock) 51 */ 52 static int time_state = TIME_OK; 53 54 /* clock status bits: */ 55 static int time_status = STA_UNSYNC; 56 57 /* time adjustment (nsecs): */ 58 static s64 time_offset; 59 60 /* pll time constant: */ 61 static long time_constant = 2; 62 63 /* maximum error (usecs): */ 64 static long time_maxerror = NTP_PHASE_LIMIT; 65 66 /* estimated error (usecs): */ 67 static long time_esterror = NTP_PHASE_LIMIT; 68 69 /* frequency offset (scaled nsecs/secs): */ 70 static s64 time_freq; 71 72 /* time at last adjustment (secs): */ 73 static long time_reftime; 74 75 static long time_adjust; 76 77 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 78 static s64 ntp_tick_adj; 79 80 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */ 81 static time64_t ntp_next_leap_sec = TIME64_MAX; 82 83 #ifdef CONFIG_NTP_PPS 84 85 /* 86 * The following variables are used when a pulse-per-second (PPS) signal 87 * is available. They establish the engineering parameters of the clock 88 * discipline loop when controlled by the PPS signal. 89 */ 90 #define PPS_VALID 10 /* PPS signal watchdog max (s) */ 91 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 92 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 93 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 94 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to 95 increase pps_shift or consecutive bad 96 intervals to decrease it */ 97 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 98 99 static int pps_valid; /* signal watchdog counter */ 100 static long pps_tf[3]; /* phase median filter */ 101 static long pps_jitter; /* current jitter (ns) */ 102 static struct timespec64 pps_fbase; /* beginning of the last freq interval */ 103 static int pps_shift; /* current interval duration (s) (shift) */ 104 static int pps_intcnt; /* interval counter */ 105 static s64 pps_freq; /* frequency offset (scaled ns/s) */ 106 static long pps_stabil; /* current stability (scaled ns/s) */ 107 108 /* 109 * PPS signal quality monitors 110 */ 111 static long pps_calcnt; /* calibration intervals */ 112 static long pps_jitcnt; /* jitter limit exceeded */ 113 static long pps_stbcnt; /* stability limit exceeded */ 114 static long pps_errcnt; /* calibration errors */ 115 116 117 /* PPS kernel consumer compensates the whole phase error immediately. 118 * Otherwise, reduce the offset by a fixed factor times the time constant. 119 */ 120 static inline s64 ntp_offset_chunk(s64 offset) 121 { 122 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 123 return offset; 124 else 125 return shift_right(offset, SHIFT_PLL + time_constant); 126 } 127 128 static inline void pps_reset_freq_interval(void) 129 { 130 /* the PPS calibration interval may end 131 surprisingly early */ 132 pps_shift = PPS_INTMIN; 133 pps_intcnt = 0; 134 } 135 136 /** 137 * pps_clear - Clears the PPS state variables 138 */ 139 static inline void pps_clear(void) 140 { 141 pps_reset_freq_interval(); 142 pps_tf[0] = 0; 143 pps_tf[1] = 0; 144 pps_tf[2] = 0; 145 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 146 pps_freq = 0; 147 } 148 149 /* Decrease pps_valid to indicate that another second has passed since 150 * the last PPS signal. When it reaches 0, indicate that PPS signal is 151 * missing. 152 */ 153 static inline void pps_dec_valid(void) 154 { 155 if (pps_valid > 0) 156 pps_valid--; 157 else { 158 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 159 STA_PPSWANDER | STA_PPSERROR); 160 pps_clear(); 161 } 162 } 163 164 static inline void pps_set_freq(s64 freq) 165 { 166 pps_freq = freq; 167 } 168 169 static inline int is_error_status(int status) 170 { 171 return (status & (STA_UNSYNC|STA_CLOCKERR)) 172 /* PPS signal lost when either PPS time or 173 * PPS frequency synchronization requested 174 */ 175 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 176 && !(status & STA_PPSSIGNAL)) 177 /* PPS jitter exceeded when 178 * PPS time synchronization requested */ 179 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 180 == (STA_PPSTIME|STA_PPSJITTER)) 181 /* PPS wander exceeded or calibration error when 182 * PPS frequency synchronization requested 183 */ 184 || ((status & STA_PPSFREQ) 185 && (status & (STA_PPSWANDER|STA_PPSERROR))); 186 } 187 188 static inline void pps_fill_timex(struct timex *txc) 189 { 190 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 191 PPM_SCALE_INV, NTP_SCALE_SHIFT); 192 txc->jitter = pps_jitter; 193 if (!(time_status & STA_NANO)) 194 txc->jitter /= NSEC_PER_USEC; 195 txc->shift = pps_shift; 196 txc->stabil = pps_stabil; 197 txc->jitcnt = pps_jitcnt; 198 txc->calcnt = pps_calcnt; 199 txc->errcnt = pps_errcnt; 200 txc->stbcnt = pps_stbcnt; 201 } 202 203 #else /* !CONFIG_NTP_PPS */ 204 205 static inline s64 ntp_offset_chunk(s64 offset) 206 { 207 return shift_right(offset, SHIFT_PLL + time_constant); 208 } 209 210 static inline void pps_reset_freq_interval(void) {} 211 static inline void pps_clear(void) {} 212 static inline void pps_dec_valid(void) {} 213 static inline void pps_set_freq(s64 freq) {} 214 215 static inline int is_error_status(int status) 216 { 217 return status & (STA_UNSYNC|STA_CLOCKERR); 218 } 219 220 static inline void pps_fill_timex(struct timex *txc) 221 { 222 /* PPS is not implemented, so these are zero */ 223 txc->ppsfreq = 0; 224 txc->jitter = 0; 225 txc->shift = 0; 226 txc->stabil = 0; 227 txc->jitcnt = 0; 228 txc->calcnt = 0; 229 txc->errcnt = 0; 230 txc->stbcnt = 0; 231 } 232 233 #endif /* CONFIG_NTP_PPS */ 234 235 236 /** 237 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 238 * 239 */ 240 static inline int ntp_synced(void) 241 { 242 return !(time_status & STA_UNSYNC); 243 } 244 245 246 /* 247 * NTP methods: 248 */ 249 250 /* 251 * Update (tick_length, tick_length_base, tick_nsec), based 252 * on (tick_usec, ntp_tick_adj, time_freq): 253 */ 254 static void ntp_update_frequency(void) 255 { 256 u64 second_length; 257 u64 new_base; 258 259 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 260 << NTP_SCALE_SHIFT; 261 262 second_length += ntp_tick_adj; 263 second_length += time_freq; 264 265 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 266 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 267 268 /* 269 * Don't wait for the next second_overflow, apply 270 * the change to the tick length immediately: 271 */ 272 tick_length += new_base - tick_length_base; 273 tick_length_base = new_base; 274 } 275 276 static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 277 { 278 time_status &= ~STA_MODE; 279 280 if (secs < MINSEC) 281 return 0; 282 283 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 284 return 0; 285 286 time_status |= STA_MODE; 287 288 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 289 } 290 291 static void ntp_update_offset(long offset) 292 { 293 s64 freq_adj; 294 s64 offset64; 295 long secs; 296 297 if (!(time_status & STA_PLL)) 298 return; 299 300 if (!(time_status & STA_NANO)) 301 offset *= NSEC_PER_USEC; 302 303 /* 304 * Scale the phase adjustment and 305 * clamp to the operating range. 306 */ 307 offset = min(offset, MAXPHASE); 308 offset = max(offset, -MAXPHASE); 309 310 /* 311 * Select how the frequency is to be controlled 312 * and in which mode (PLL or FLL). 313 */ 314 secs = get_seconds() - time_reftime; 315 if (unlikely(time_status & STA_FREQHOLD)) 316 secs = 0; 317 318 time_reftime = get_seconds(); 319 320 offset64 = offset; 321 freq_adj = ntp_update_offset_fll(offset64, secs); 322 323 /* 324 * Clamp update interval to reduce PLL gain with low 325 * sampling rate (e.g. intermittent network connection) 326 * to avoid instability. 327 */ 328 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 329 secs = 1 << (SHIFT_PLL + 1 + time_constant); 330 331 freq_adj += (offset64 * secs) << 332 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 333 334 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 335 336 time_freq = max(freq_adj, -MAXFREQ_SCALED); 337 338 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 339 } 340 341 /** 342 * ntp_clear - Clears the NTP state variables 343 */ 344 void ntp_clear(void) 345 { 346 time_adjust = 0; /* stop active adjtime() */ 347 time_status |= STA_UNSYNC; 348 time_maxerror = NTP_PHASE_LIMIT; 349 time_esterror = NTP_PHASE_LIMIT; 350 351 ntp_update_frequency(); 352 353 tick_length = tick_length_base; 354 time_offset = 0; 355 356 ntp_next_leap_sec = TIME64_MAX; 357 /* Clear PPS state variables */ 358 pps_clear(); 359 } 360 361 362 u64 ntp_tick_length(void) 363 { 364 return tick_length; 365 } 366 367 /** 368 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t 369 * 370 * Provides the time of the next leapsecond against CLOCK_REALTIME in 371 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending. 372 */ 373 ktime_t ntp_get_next_leap(void) 374 { 375 ktime_t ret; 376 377 if ((time_state == TIME_INS) && (time_status & STA_INS)) 378 return ktime_set(ntp_next_leap_sec, 0); 379 ret.tv64 = KTIME_MAX; 380 return ret; 381 } 382 383 /* 384 * this routine handles the overflow of the microsecond field 385 * 386 * The tricky bits of code to handle the accurate clock support 387 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 388 * They were originally developed for SUN and DEC kernels. 389 * All the kudos should go to Dave for this stuff. 390 * 391 * Also handles leap second processing, and returns leap offset 392 */ 393 int second_overflow(unsigned long secs) 394 { 395 s64 delta; 396 int leap = 0; 397 398 /* 399 * Leap second processing. If in leap-insert state at the end of the 400 * day, the system clock is set back one second; if in leap-delete 401 * state, the system clock is set ahead one second. 402 */ 403 switch (time_state) { 404 case TIME_OK: 405 if (time_status & STA_INS) { 406 time_state = TIME_INS; 407 ntp_next_leap_sec = secs + SECS_PER_DAY - 408 (secs % SECS_PER_DAY); 409 } else if (time_status & STA_DEL) { 410 time_state = TIME_DEL; 411 ntp_next_leap_sec = secs + SECS_PER_DAY - 412 ((secs+1) % SECS_PER_DAY); 413 } 414 break; 415 case TIME_INS: 416 if (!(time_status & STA_INS)) { 417 ntp_next_leap_sec = TIME64_MAX; 418 time_state = TIME_OK; 419 } else if (secs % SECS_PER_DAY == 0) { 420 leap = -1; 421 time_state = TIME_OOP; 422 printk(KERN_NOTICE 423 "Clock: inserting leap second 23:59:60 UTC\n"); 424 } 425 break; 426 case TIME_DEL: 427 if (!(time_status & STA_DEL)) { 428 ntp_next_leap_sec = TIME64_MAX; 429 time_state = TIME_OK; 430 } else if ((secs + 1) % SECS_PER_DAY == 0) { 431 leap = 1; 432 ntp_next_leap_sec = TIME64_MAX; 433 time_state = TIME_WAIT; 434 printk(KERN_NOTICE 435 "Clock: deleting leap second 23:59:59 UTC\n"); 436 } 437 break; 438 case TIME_OOP: 439 ntp_next_leap_sec = TIME64_MAX; 440 time_state = TIME_WAIT; 441 break; 442 case TIME_WAIT: 443 if (!(time_status & (STA_INS | STA_DEL))) 444 time_state = TIME_OK; 445 break; 446 } 447 448 449 /* Bump the maxerror field */ 450 time_maxerror += MAXFREQ / NSEC_PER_USEC; 451 if (time_maxerror > NTP_PHASE_LIMIT) { 452 time_maxerror = NTP_PHASE_LIMIT; 453 time_status |= STA_UNSYNC; 454 } 455 456 /* Compute the phase adjustment for the next second */ 457 tick_length = tick_length_base; 458 459 delta = ntp_offset_chunk(time_offset); 460 time_offset -= delta; 461 tick_length += delta; 462 463 /* Check PPS signal */ 464 pps_dec_valid(); 465 466 if (!time_adjust) 467 goto out; 468 469 if (time_adjust > MAX_TICKADJ) { 470 time_adjust -= MAX_TICKADJ; 471 tick_length += MAX_TICKADJ_SCALED; 472 goto out; 473 } 474 475 if (time_adjust < -MAX_TICKADJ) { 476 time_adjust += MAX_TICKADJ; 477 tick_length -= MAX_TICKADJ_SCALED; 478 goto out; 479 } 480 481 tick_length += (s64)(time_adjust * NSEC_PER_USEC / NTP_INTERVAL_FREQ) 482 << NTP_SCALE_SHIFT; 483 time_adjust = 0; 484 485 out: 486 return leap; 487 } 488 489 #ifdef CONFIG_GENERIC_CMOS_UPDATE 490 int __weak update_persistent_clock(struct timespec now) 491 { 492 return -ENODEV; 493 } 494 495 int __weak update_persistent_clock64(struct timespec64 now64) 496 { 497 struct timespec now; 498 499 now = timespec64_to_timespec(now64); 500 return update_persistent_clock(now); 501 } 502 #endif 503 504 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) 505 static void sync_cmos_clock(struct work_struct *work); 506 507 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); 508 509 static void sync_cmos_clock(struct work_struct *work) 510 { 511 struct timespec64 now; 512 struct timespec64 next; 513 int fail = 1; 514 515 /* 516 * If we have an externally synchronized Linux clock, then update 517 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be 518 * called as close as possible to 500 ms before the new second starts. 519 * This code is run on a timer. If the clock is set, that timer 520 * may not expire at the correct time. Thus, we adjust... 521 * We want the clock to be within a couple of ticks from the target. 522 */ 523 if (!ntp_synced()) { 524 /* 525 * Not synced, exit, do not restart a timer (if one is 526 * running, let it run out). 527 */ 528 return; 529 } 530 531 getnstimeofday64(&now); 532 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) { 533 struct timespec64 adjust = now; 534 535 fail = -ENODEV; 536 if (persistent_clock_is_local) 537 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 538 #ifdef CONFIG_GENERIC_CMOS_UPDATE 539 fail = update_persistent_clock64(adjust); 540 #endif 541 542 #ifdef CONFIG_RTC_SYSTOHC 543 if (fail == -ENODEV) 544 fail = rtc_set_ntp_time(adjust); 545 #endif 546 } 547 548 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); 549 if (next.tv_nsec <= 0) 550 next.tv_nsec += NSEC_PER_SEC; 551 552 if (!fail || fail == -ENODEV) 553 next.tv_sec = 659; 554 else 555 next.tv_sec = 0; 556 557 if (next.tv_nsec >= NSEC_PER_SEC) { 558 next.tv_sec++; 559 next.tv_nsec -= NSEC_PER_SEC; 560 } 561 queue_delayed_work(system_power_efficient_wq, 562 &sync_cmos_work, timespec64_to_jiffies(&next)); 563 } 564 565 void ntp_notify_cmos_timer(void) 566 { 567 queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0); 568 } 569 570 #else 571 void ntp_notify_cmos_timer(void) { } 572 #endif 573 574 575 /* 576 * Propagate a new txc->status value into the NTP state: 577 */ 578 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts) 579 { 580 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 581 time_state = TIME_OK; 582 time_status = STA_UNSYNC; 583 ntp_next_leap_sec = TIME64_MAX; 584 /* restart PPS frequency calibration */ 585 pps_reset_freq_interval(); 586 } 587 588 /* 589 * If we turn on PLL adjustments then reset the 590 * reference time to current time. 591 */ 592 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 593 time_reftime = get_seconds(); 594 595 /* only set allowed bits */ 596 time_status &= STA_RONLY; 597 time_status |= txc->status & ~STA_RONLY; 598 } 599 600 601 static inline void process_adjtimex_modes(struct timex *txc, 602 struct timespec64 *ts, 603 s32 *time_tai) 604 { 605 if (txc->modes & ADJ_STATUS) 606 process_adj_status(txc, ts); 607 608 if (txc->modes & ADJ_NANO) 609 time_status |= STA_NANO; 610 611 if (txc->modes & ADJ_MICRO) 612 time_status &= ~STA_NANO; 613 614 if (txc->modes & ADJ_FREQUENCY) { 615 time_freq = txc->freq * PPM_SCALE; 616 time_freq = min(time_freq, MAXFREQ_SCALED); 617 time_freq = max(time_freq, -MAXFREQ_SCALED); 618 /* update pps_freq */ 619 pps_set_freq(time_freq); 620 } 621 622 if (txc->modes & ADJ_MAXERROR) 623 time_maxerror = txc->maxerror; 624 625 if (txc->modes & ADJ_ESTERROR) 626 time_esterror = txc->esterror; 627 628 if (txc->modes & ADJ_TIMECONST) { 629 time_constant = txc->constant; 630 if (!(time_status & STA_NANO)) 631 time_constant += 4; 632 time_constant = min(time_constant, (long)MAXTC); 633 time_constant = max(time_constant, 0l); 634 } 635 636 if (txc->modes & ADJ_TAI && txc->constant > 0) 637 *time_tai = txc->constant; 638 639 if (txc->modes & ADJ_OFFSET) 640 ntp_update_offset(txc->offset); 641 642 if (txc->modes & ADJ_TICK) 643 tick_usec = txc->tick; 644 645 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 646 ntp_update_frequency(); 647 } 648 649 650 651 /** 652 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex 653 */ 654 int ntp_validate_timex(struct timex *txc) 655 { 656 if (txc->modes & ADJ_ADJTIME) { 657 /* singleshot must not be used with any other mode bits */ 658 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT)) 659 return -EINVAL; 660 if (!(txc->modes & ADJ_OFFSET_READONLY) && 661 !capable(CAP_SYS_TIME)) 662 return -EPERM; 663 } else { 664 /* In order to modify anything, you gotta be super-user! */ 665 if (txc->modes && !capable(CAP_SYS_TIME)) 666 return -EPERM; 667 /* 668 * if the quartz is off by more than 10% then 669 * something is VERY wrong! 670 */ 671 if (txc->modes & ADJ_TICK && 672 (txc->tick < 900000/USER_HZ || 673 txc->tick > 1100000/USER_HZ)) 674 return -EINVAL; 675 } 676 677 if ((txc->modes & ADJ_SETOFFSET) && (!capable(CAP_SYS_TIME))) 678 return -EPERM; 679 680 /* 681 * Check for potential multiplication overflows that can 682 * only happen on 64-bit systems: 683 */ 684 if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) { 685 if (LLONG_MIN / PPM_SCALE > txc->freq) 686 return -EINVAL; 687 if (LLONG_MAX / PPM_SCALE < txc->freq) 688 return -EINVAL; 689 } 690 691 return 0; 692 } 693 694 695 /* 696 * adjtimex mainly allows reading (and writing, if superuser) of 697 * kernel time-keeping variables. used by xntpd. 698 */ 699 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai) 700 { 701 int result; 702 703 if (txc->modes & ADJ_ADJTIME) { 704 long save_adjust = time_adjust; 705 706 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 707 /* adjtime() is independent from ntp_adjtime() */ 708 time_adjust = txc->offset; 709 ntp_update_frequency(); 710 } 711 txc->offset = save_adjust; 712 } else { 713 714 /* If there are input parameters, then process them: */ 715 if (txc->modes) 716 process_adjtimex_modes(txc, ts, time_tai); 717 718 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 719 NTP_SCALE_SHIFT); 720 if (!(time_status & STA_NANO)) 721 txc->offset /= NSEC_PER_USEC; 722 } 723 724 result = time_state; /* mostly `TIME_OK' */ 725 /* check for errors */ 726 if (is_error_status(time_status)) 727 result = TIME_ERROR; 728 729 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 730 PPM_SCALE_INV, NTP_SCALE_SHIFT); 731 txc->maxerror = time_maxerror; 732 txc->esterror = time_esterror; 733 txc->status = time_status; 734 txc->constant = time_constant; 735 txc->precision = 1; 736 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 737 txc->tick = tick_usec; 738 txc->tai = *time_tai; 739 740 /* fill PPS status fields */ 741 pps_fill_timex(txc); 742 743 txc->time.tv_sec = (time_t)ts->tv_sec; 744 txc->time.tv_usec = ts->tv_nsec; 745 if (!(time_status & STA_NANO)) 746 txc->time.tv_usec /= NSEC_PER_USEC; 747 748 /* Handle leapsec adjustments */ 749 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 750 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 751 result = TIME_OOP; 752 txc->tai++; 753 txc->time.tv_sec--; 754 } 755 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 756 result = TIME_WAIT; 757 txc->tai--; 758 txc->time.tv_sec++; 759 } 760 if ((time_state == TIME_OOP) && 761 (ts->tv_sec == ntp_next_leap_sec)) { 762 result = TIME_WAIT; 763 } 764 } 765 766 return result; 767 } 768 769 #ifdef CONFIG_NTP_PPS 770 771 /* actually struct pps_normtime is good old struct timespec, but it is 772 * semantically different (and it is the reason why it was invented): 773 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 774 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 775 struct pps_normtime { 776 s64 sec; /* seconds */ 777 long nsec; /* nanoseconds */ 778 }; 779 780 /* normalize the timestamp so that nsec is in the 781 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 782 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 783 { 784 struct pps_normtime norm = { 785 .sec = ts.tv_sec, 786 .nsec = ts.tv_nsec 787 }; 788 789 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 790 norm.nsec -= NSEC_PER_SEC; 791 norm.sec++; 792 } 793 794 return norm; 795 } 796 797 /* get current phase correction and jitter */ 798 static inline long pps_phase_filter_get(long *jitter) 799 { 800 *jitter = pps_tf[0] - pps_tf[1]; 801 if (*jitter < 0) 802 *jitter = -*jitter; 803 804 /* TODO: test various filters */ 805 return pps_tf[0]; 806 } 807 808 /* add the sample to the phase filter */ 809 static inline void pps_phase_filter_add(long err) 810 { 811 pps_tf[2] = pps_tf[1]; 812 pps_tf[1] = pps_tf[0]; 813 pps_tf[0] = err; 814 } 815 816 /* decrease frequency calibration interval length. 817 * It is halved after four consecutive unstable intervals. 818 */ 819 static inline void pps_dec_freq_interval(void) 820 { 821 if (--pps_intcnt <= -PPS_INTCOUNT) { 822 pps_intcnt = -PPS_INTCOUNT; 823 if (pps_shift > PPS_INTMIN) { 824 pps_shift--; 825 pps_intcnt = 0; 826 } 827 } 828 } 829 830 /* increase frequency calibration interval length. 831 * It is doubled after four consecutive stable intervals. 832 */ 833 static inline void pps_inc_freq_interval(void) 834 { 835 if (++pps_intcnt >= PPS_INTCOUNT) { 836 pps_intcnt = PPS_INTCOUNT; 837 if (pps_shift < PPS_INTMAX) { 838 pps_shift++; 839 pps_intcnt = 0; 840 } 841 } 842 } 843 844 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 845 * timestamps 846 * 847 * At the end of the calibration interval the difference between the 848 * first and last MONOTONIC_RAW clock timestamps divided by the length 849 * of the interval becomes the frequency update. If the interval was 850 * too long, the data are discarded. 851 * Returns the difference between old and new frequency values. 852 */ 853 static long hardpps_update_freq(struct pps_normtime freq_norm) 854 { 855 long delta, delta_mod; 856 s64 ftemp; 857 858 /* check if the frequency interval was too long */ 859 if (freq_norm.sec > (2 << pps_shift)) { 860 time_status |= STA_PPSERROR; 861 pps_errcnt++; 862 pps_dec_freq_interval(); 863 printk_deferred(KERN_ERR 864 "hardpps: PPSERROR: interval too long - %lld s\n", 865 freq_norm.sec); 866 return 0; 867 } 868 869 /* here the raw frequency offset and wander (stability) is 870 * calculated. If the wander is less than the wander threshold 871 * the interval is increased; otherwise it is decreased. 872 */ 873 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 874 freq_norm.sec); 875 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 876 pps_freq = ftemp; 877 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 878 printk_deferred(KERN_WARNING 879 "hardpps: PPSWANDER: change=%ld\n", delta); 880 time_status |= STA_PPSWANDER; 881 pps_stbcnt++; 882 pps_dec_freq_interval(); 883 } else { /* good sample */ 884 pps_inc_freq_interval(); 885 } 886 887 /* the stability metric is calculated as the average of recent 888 * frequency changes, but is used only for performance 889 * monitoring 890 */ 891 delta_mod = delta; 892 if (delta_mod < 0) 893 delta_mod = -delta_mod; 894 pps_stabil += (div_s64(((s64)delta_mod) << 895 (NTP_SCALE_SHIFT - SHIFT_USEC), 896 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 897 898 /* if enabled, the system clock frequency is updated */ 899 if ((time_status & STA_PPSFREQ) != 0 && 900 (time_status & STA_FREQHOLD) == 0) { 901 time_freq = pps_freq; 902 ntp_update_frequency(); 903 } 904 905 return delta; 906 } 907 908 /* correct REALTIME clock phase error against PPS signal */ 909 static void hardpps_update_phase(long error) 910 { 911 long correction = -error; 912 long jitter; 913 914 /* add the sample to the median filter */ 915 pps_phase_filter_add(correction); 916 correction = pps_phase_filter_get(&jitter); 917 918 /* Nominal jitter is due to PPS signal noise. If it exceeds the 919 * threshold, the sample is discarded; otherwise, if so enabled, 920 * the time offset is updated. 921 */ 922 if (jitter > (pps_jitter << PPS_POPCORN)) { 923 printk_deferred(KERN_WARNING 924 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 925 jitter, (pps_jitter << PPS_POPCORN)); 926 time_status |= STA_PPSJITTER; 927 pps_jitcnt++; 928 } else if (time_status & STA_PPSTIME) { 929 /* correct the time using the phase offset */ 930 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 931 NTP_INTERVAL_FREQ); 932 /* cancel running adjtime() */ 933 time_adjust = 0; 934 } 935 /* update jitter */ 936 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 937 } 938 939 /* 940 * __hardpps() - discipline CPU clock oscillator to external PPS signal 941 * 942 * This routine is called at each PPS signal arrival in order to 943 * discipline the CPU clock oscillator to the PPS signal. It takes two 944 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 945 * is used to correct clock phase error and the latter is used to 946 * correct the frequency. 947 * 948 * This code is based on David Mills's reference nanokernel 949 * implementation. It was mostly rewritten but keeps the same idea. 950 */ 951 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 952 { 953 struct pps_normtime pts_norm, freq_norm; 954 955 pts_norm = pps_normalize_ts(*phase_ts); 956 957 /* clear the error bits, they will be set again if needed */ 958 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 959 960 /* indicate signal presence */ 961 time_status |= STA_PPSSIGNAL; 962 pps_valid = PPS_VALID; 963 964 /* when called for the first time, 965 * just start the frequency interval */ 966 if (unlikely(pps_fbase.tv_sec == 0)) { 967 pps_fbase = *raw_ts; 968 return; 969 } 970 971 /* ok, now we have a base for frequency calculation */ 972 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 973 974 /* check that the signal is in the range 975 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 976 if ((freq_norm.sec == 0) || 977 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 978 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 979 time_status |= STA_PPSJITTER; 980 /* restart the frequency calibration interval */ 981 pps_fbase = *raw_ts; 982 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 983 return; 984 } 985 986 /* signal is ok */ 987 988 /* check if the current frequency interval is finished */ 989 if (freq_norm.sec >= (1 << pps_shift)) { 990 pps_calcnt++; 991 /* restart the frequency calibration interval */ 992 pps_fbase = *raw_ts; 993 hardpps_update_freq(freq_norm); 994 } 995 996 hardpps_update_phase(pts_norm.nsec); 997 998 } 999 #endif /* CONFIG_NTP_PPS */ 1000 1001 static int __init ntp_tick_adj_setup(char *str) 1002 { 1003 int rc = kstrtol(str, 0, (long *)&ntp_tick_adj); 1004 1005 if (rc) 1006 return rc; 1007 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1008 1009 return 1; 1010 } 1011 1012 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1013 1014 void __init ntp_init(void) 1015 { 1016 ntp_clear(); 1017 } 1018