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 #include <linux/math64.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 = TICK_USEC; 34 35 /* SHIFTED_HZ period (nsecs): */ 36 unsigned long tick_nsec; 37 38 static u64 tick_length; 39 static u64 tick_length_base; 40 41 #define SECS_PER_DAY 86400 42 #define MAX_TICKADJ 500LL /* usecs */ 43 #define MAX_TICKADJ_SCALED \ 44 (((MAX_TICKADJ * NSEC_PER_USEC) << NTP_SCALE_SHIFT) / NTP_INTERVAL_FREQ) 45 46 /* 47 * phase-lock loop variables 48 */ 49 50 /* 51 * clock synchronization status 52 * 53 * (TIME_ERROR prevents overwriting the CMOS clock) 54 */ 55 static int time_state = TIME_OK; 56 57 /* clock status bits: */ 58 static int time_status = STA_UNSYNC; 59 60 /* time adjustment (nsecs): */ 61 static s64 time_offset; 62 63 /* pll time constant: */ 64 static long time_constant = 2; 65 66 /* maximum error (usecs): */ 67 static long time_maxerror = NTP_PHASE_LIMIT; 68 69 /* estimated error (usecs): */ 70 static long time_esterror = NTP_PHASE_LIMIT; 71 72 /* frequency offset (scaled nsecs/secs): */ 73 static s64 time_freq; 74 75 /* time at last adjustment (secs): */ 76 static time64_t time_reftime; 77 78 static long time_adjust; 79 80 /* constant (boot-param configurable) NTP tick adjustment (upscaled) */ 81 static s64 ntp_tick_adj; 82 83 /* second value of the next pending leapsecond, or TIME64_MAX if no leap */ 84 static time64_t ntp_next_leap_sec = TIME64_MAX; 85 86 #ifdef CONFIG_NTP_PPS 87 88 /* 89 * The following variables are used when a pulse-per-second (PPS) signal 90 * is available. They establish the engineering parameters of the clock 91 * discipline loop when controlled by the PPS signal. 92 */ 93 #define PPS_VALID 10 /* PPS signal watchdog max (s) */ 94 #define PPS_POPCORN 4 /* popcorn spike threshold (shift) */ 95 #define PPS_INTMIN 2 /* min freq interval (s) (shift) */ 96 #define PPS_INTMAX 8 /* max freq interval (s) (shift) */ 97 #define PPS_INTCOUNT 4 /* number of consecutive good intervals to 98 increase pps_shift or consecutive bad 99 intervals to decrease it */ 100 #define PPS_MAXWANDER 100000 /* max PPS freq wander (ns/s) */ 101 102 static int pps_valid; /* signal watchdog counter */ 103 static long pps_tf[3]; /* phase median filter */ 104 static long pps_jitter; /* current jitter (ns) */ 105 static struct timespec64 pps_fbase; /* beginning of the last freq interval */ 106 static int pps_shift; /* current interval duration (s) (shift) */ 107 static int pps_intcnt; /* interval counter */ 108 static s64 pps_freq; /* frequency offset (scaled ns/s) */ 109 static long pps_stabil; /* current stability (scaled ns/s) */ 110 111 /* 112 * PPS signal quality monitors 113 */ 114 static long pps_calcnt; /* calibration intervals */ 115 static long pps_jitcnt; /* jitter limit exceeded */ 116 static long pps_stbcnt; /* stability limit exceeded */ 117 static long pps_errcnt; /* calibration errors */ 118 119 120 /* PPS kernel consumer compensates the whole phase error immediately. 121 * Otherwise, reduce the offset by a fixed factor times the time constant. 122 */ 123 static inline s64 ntp_offset_chunk(s64 offset) 124 { 125 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) 126 return offset; 127 else 128 return shift_right(offset, SHIFT_PLL + time_constant); 129 } 130 131 static inline void pps_reset_freq_interval(void) 132 { 133 /* the PPS calibration interval may end 134 surprisingly early */ 135 pps_shift = PPS_INTMIN; 136 pps_intcnt = 0; 137 } 138 139 /** 140 * pps_clear - Clears the PPS state variables 141 */ 142 static inline void pps_clear(void) 143 { 144 pps_reset_freq_interval(); 145 pps_tf[0] = 0; 146 pps_tf[1] = 0; 147 pps_tf[2] = 0; 148 pps_fbase.tv_sec = pps_fbase.tv_nsec = 0; 149 pps_freq = 0; 150 } 151 152 /* Decrease pps_valid to indicate that another second has passed since 153 * the last PPS signal. When it reaches 0, indicate that PPS signal is 154 * missing. 155 */ 156 static inline void pps_dec_valid(void) 157 { 158 if (pps_valid > 0) 159 pps_valid--; 160 else { 161 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 162 STA_PPSWANDER | STA_PPSERROR); 163 pps_clear(); 164 } 165 } 166 167 static inline void pps_set_freq(s64 freq) 168 { 169 pps_freq = freq; 170 } 171 172 static inline int is_error_status(int status) 173 { 174 return (status & (STA_UNSYNC|STA_CLOCKERR)) 175 /* PPS signal lost when either PPS time or 176 * PPS frequency synchronization requested 177 */ 178 || ((status & (STA_PPSFREQ|STA_PPSTIME)) 179 && !(status & STA_PPSSIGNAL)) 180 /* PPS jitter exceeded when 181 * PPS time synchronization requested */ 182 || ((status & (STA_PPSTIME|STA_PPSJITTER)) 183 == (STA_PPSTIME|STA_PPSJITTER)) 184 /* PPS wander exceeded or calibration error when 185 * PPS frequency synchronization requested 186 */ 187 || ((status & STA_PPSFREQ) 188 && (status & (STA_PPSWANDER|STA_PPSERROR))); 189 } 190 191 static inline void pps_fill_timex(struct timex *txc) 192 { 193 txc->ppsfreq = shift_right((pps_freq >> PPM_SCALE_INV_SHIFT) * 194 PPM_SCALE_INV, NTP_SCALE_SHIFT); 195 txc->jitter = pps_jitter; 196 if (!(time_status & STA_NANO)) 197 txc->jitter /= NSEC_PER_USEC; 198 txc->shift = pps_shift; 199 txc->stabil = pps_stabil; 200 txc->jitcnt = pps_jitcnt; 201 txc->calcnt = pps_calcnt; 202 txc->errcnt = pps_errcnt; 203 txc->stbcnt = pps_stbcnt; 204 } 205 206 #else /* !CONFIG_NTP_PPS */ 207 208 static inline s64 ntp_offset_chunk(s64 offset) 209 { 210 return shift_right(offset, SHIFT_PLL + time_constant); 211 } 212 213 static inline void pps_reset_freq_interval(void) {} 214 static inline void pps_clear(void) {} 215 static inline void pps_dec_valid(void) {} 216 static inline void pps_set_freq(s64 freq) {} 217 218 static inline int is_error_status(int status) 219 { 220 return status & (STA_UNSYNC|STA_CLOCKERR); 221 } 222 223 static inline void pps_fill_timex(struct timex *txc) 224 { 225 /* PPS is not implemented, so these are zero */ 226 txc->ppsfreq = 0; 227 txc->jitter = 0; 228 txc->shift = 0; 229 txc->stabil = 0; 230 txc->jitcnt = 0; 231 txc->calcnt = 0; 232 txc->errcnt = 0; 233 txc->stbcnt = 0; 234 } 235 236 #endif /* CONFIG_NTP_PPS */ 237 238 239 /** 240 * ntp_synced - Returns 1 if the NTP status is not UNSYNC 241 * 242 */ 243 static inline int ntp_synced(void) 244 { 245 return !(time_status & STA_UNSYNC); 246 } 247 248 249 /* 250 * NTP methods: 251 */ 252 253 /* 254 * Update (tick_length, tick_length_base, tick_nsec), based 255 * on (tick_usec, ntp_tick_adj, time_freq): 256 */ 257 static void ntp_update_frequency(void) 258 { 259 u64 second_length; 260 u64 new_base; 261 262 second_length = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) 263 << NTP_SCALE_SHIFT; 264 265 second_length += ntp_tick_adj; 266 second_length += time_freq; 267 268 tick_nsec = div_u64(second_length, HZ) >> NTP_SCALE_SHIFT; 269 new_base = div_u64(second_length, NTP_INTERVAL_FREQ); 270 271 /* 272 * Don't wait for the next second_overflow, apply 273 * the change to the tick length immediately: 274 */ 275 tick_length += new_base - tick_length_base; 276 tick_length_base = new_base; 277 } 278 279 static inline s64 ntp_update_offset_fll(s64 offset64, long secs) 280 { 281 time_status &= ~STA_MODE; 282 283 if (secs < MINSEC) 284 return 0; 285 286 if (!(time_status & STA_FLL) && (secs <= MAXSEC)) 287 return 0; 288 289 time_status |= STA_MODE; 290 291 return div64_long(offset64 << (NTP_SCALE_SHIFT - SHIFT_FLL), secs); 292 } 293 294 static void ntp_update_offset(long offset) 295 { 296 s64 freq_adj; 297 s64 offset64; 298 long secs; 299 300 if (!(time_status & STA_PLL)) 301 return; 302 303 if (!(time_status & STA_NANO)) { 304 /* Make sure the multiplication below won't overflow */ 305 offset = clamp(offset, -USEC_PER_SEC, USEC_PER_SEC); 306 offset *= NSEC_PER_USEC; 307 } 308 309 /* 310 * Scale the phase adjustment and 311 * clamp to the operating range. 312 */ 313 offset = clamp(offset, -MAXPHASE, MAXPHASE); 314 315 /* 316 * Select how the frequency is to be controlled 317 * and in which mode (PLL or FLL). 318 */ 319 secs = (long)(__ktime_get_real_seconds() - time_reftime); 320 if (unlikely(time_status & STA_FREQHOLD)) 321 secs = 0; 322 323 time_reftime = __ktime_get_real_seconds(); 324 325 offset64 = offset; 326 freq_adj = ntp_update_offset_fll(offset64, secs); 327 328 /* 329 * Clamp update interval to reduce PLL gain with low 330 * sampling rate (e.g. intermittent network connection) 331 * to avoid instability. 332 */ 333 if (unlikely(secs > 1 << (SHIFT_PLL + 1 + time_constant))) 334 secs = 1 << (SHIFT_PLL + 1 + time_constant); 335 336 freq_adj += (offset64 * secs) << 337 (NTP_SCALE_SHIFT - 2 * (SHIFT_PLL + 2 + time_constant)); 338 339 freq_adj = min(freq_adj + time_freq, MAXFREQ_SCALED); 340 341 time_freq = max(freq_adj, -MAXFREQ_SCALED); 342 343 time_offset = div_s64(offset64 << NTP_SCALE_SHIFT, NTP_INTERVAL_FREQ); 344 } 345 346 /** 347 * ntp_clear - Clears the NTP state variables 348 */ 349 void ntp_clear(void) 350 { 351 time_adjust = 0; /* stop active adjtime() */ 352 time_status |= STA_UNSYNC; 353 time_maxerror = NTP_PHASE_LIMIT; 354 time_esterror = NTP_PHASE_LIMIT; 355 356 ntp_update_frequency(); 357 358 tick_length = tick_length_base; 359 time_offset = 0; 360 361 ntp_next_leap_sec = TIME64_MAX; 362 /* Clear PPS state variables */ 363 pps_clear(); 364 } 365 366 367 u64 ntp_tick_length(void) 368 { 369 return tick_length; 370 } 371 372 /** 373 * ntp_get_next_leap - Returns the next leapsecond in CLOCK_REALTIME ktime_t 374 * 375 * Provides the time of the next leapsecond against CLOCK_REALTIME in 376 * a ktime_t format. Returns KTIME_MAX if no leapsecond is pending. 377 */ 378 ktime_t ntp_get_next_leap(void) 379 { 380 ktime_t ret; 381 382 if ((time_state == TIME_INS) && (time_status & STA_INS)) 383 return ktime_set(ntp_next_leap_sec, 0); 384 ret.tv64 = 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 #ifdef CONFIG_GENERIC_CMOS_UPDATE 496 int __weak update_persistent_clock(struct timespec now) 497 { 498 return -ENODEV; 499 } 500 501 int __weak update_persistent_clock64(struct timespec64 now64) 502 { 503 struct timespec now; 504 505 now = timespec64_to_timespec(now64); 506 return update_persistent_clock(now); 507 } 508 #endif 509 510 #if defined(CONFIG_GENERIC_CMOS_UPDATE) || defined(CONFIG_RTC_SYSTOHC) 511 static void sync_cmos_clock(struct work_struct *work); 512 513 static DECLARE_DELAYED_WORK(sync_cmos_work, sync_cmos_clock); 514 515 static void sync_cmos_clock(struct work_struct *work) 516 { 517 struct timespec64 now; 518 struct timespec64 next; 519 int fail = 1; 520 521 /* 522 * If we have an externally synchronized Linux clock, then update 523 * CMOS clock accordingly every ~11 minutes. Set_rtc_mmss() has to be 524 * called as close as possible to 500 ms before the new second starts. 525 * This code is run on a timer. If the clock is set, that timer 526 * may not expire at the correct time. Thus, we adjust... 527 * We want the clock to be within a couple of ticks from the target. 528 */ 529 if (!ntp_synced()) { 530 /* 531 * Not synced, exit, do not restart a timer (if one is 532 * running, let it run out). 533 */ 534 return; 535 } 536 537 getnstimeofday64(&now); 538 if (abs(now.tv_nsec - (NSEC_PER_SEC / 2)) <= tick_nsec * 5) { 539 struct timespec64 adjust = now; 540 541 fail = -ENODEV; 542 if (persistent_clock_is_local) 543 adjust.tv_sec -= (sys_tz.tz_minuteswest * 60); 544 #ifdef CONFIG_GENERIC_CMOS_UPDATE 545 fail = update_persistent_clock64(adjust); 546 #endif 547 548 #ifdef CONFIG_RTC_SYSTOHC 549 if (fail == -ENODEV) 550 fail = rtc_set_ntp_time(adjust); 551 #endif 552 } 553 554 next.tv_nsec = (NSEC_PER_SEC / 2) - now.tv_nsec - (TICK_NSEC / 2); 555 if (next.tv_nsec <= 0) 556 next.tv_nsec += NSEC_PER_SEC; 557 558 if (!fail || fail == -ENODEV) 559 next.tv_sec = 659; 560 else 561 next.tv_sec = 0; 562 563 if (next.tv_nsec >= NSEC_PER_SEC) { 564 next.tv_sec++; 565 next.tv_nsec -= NSEC_PER_SEC; 566 } 567 queue_delayed_work(system_power_efficient_wq, 568 &sync_cmos_work, timespec64_to_jiffies(&next)); 569 } 570 571 void ntp_notify_cmos_timer(void) 572 { 573 queue_delayed_work(system_power_efficient_wq, &sync_cmos_work, 0); 574 } 575 576 #else 577 void ntp_notify_cmos_timer(void) { } 578 #endif 579 580 581 /* 582 * Propagate a new txc->status value into the NTP state: 583 */ 584 static inline void process_adj_status(struct timex *txc, struct timespec64 *ts) 585 { 586 if ((time_status & STA_PLL) && !(txc->status & STA_PLL)) { 587 time_state = TIME_OK; 588 time_status = STA_UNSYNC; 589 ntp_next_leap_sec = TIME64_MAX; 590 /* restart PPS frequency calibration */ 591 pps_reset_freq_interval(); 592 } 593 594 /* 595 * If we turn on PLL adjustments then reset the 596 * reference time to current time. 597 */ 598 if (!(time_status & STA_PLL) && (txc->status & STA_PLL)) 599 time_reftime = __ktime_get_real_seconds(); 600 601 /* only set allowed bits */ 602 time_status &= STA_RONLY; 603 time_status |= txc->status & ~STA_RONLY; 604 } 605 606 607 static inline void process_adjtimex_modes(struct timex *txc, 608 struct timespec64 *ts, 609 s32 *time_tai) 610 { 611 if (txc->modes & ADJ_STATUS) 612 process_adj_status(txc, ts); 613 614 if (txc->modes & ADJ_NANO) 615 time_status |= STA_NANO; 616 617 if (txc->modes & ADJ_MICRO) 618 time_status &= ~STA_NANO; 619 620 if (txc->modes & ADJ_FREQUENCY) { 621 time_freq = txc->freq * PPM_SCALE; 622 time_freq = min(time_freq, MAXFREQ_SCALED); 623 time_freq = max(time_freq, -MAXFREQ_SCALED); 624 /* update pps_freq */ 625 pps_set_freq(time_freq); 626 } 627 628 if (txc->modes & ADJ_MAXERROR) 629 time_maxerror = txc->maxerror; 630 631 if (txc->modes & ADJ_ESTERROR) 632 time_esterror = txc->esterror; 633 634 if (txc->modes & ADJ_TIMECONST) { 635 time_constant = txc->constant; 636 if (!(time_status & STA_NANO)) 637 time_constant += 4; 638 time_constant = min(time_constant, (long)MAXTC); 639 time_constant = max(time_constant, 0l); 640 } 641 642 if (txc->modes & ADJ_TAI && txc->constant > 0) 643 *time_tai = txc->constant; 644 645 if (txc->modes & ADJ_OFFSET) 646 ntp_update_offset(txc->offset); 647 648 if (txc->modes & ADJ_TICK) 649 tick_usec = txc->tick; 650 651 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 652 ntp_update_frequency(); 653 } 654 655 656 657 /** 658 * ntp_validate_timex - Ensures the timex is ok for use in do_adjtimex 659 */ 660 int ntp_validate_timex(struct timex *txc) 661 { 662 if (txc->modes & ADJ_ADJTIME) { 663 /* singleshot must not be used with any other mode bits */ 664 if (!(txc->modes & ADJ_OFFSET_SINGLESHOT)) 665 return -EINVAL; 666 if (!(txc->modes & ADJ_OFFSET_READONLY) && 667 !capable(CAP_SYS_TIME)) 668 return -EPERM; 669 } else { 670 /* In order to modify anything, you gotta be super-user! */ 671 if (txc->modes && !capable(CAP_SYS_TIME)) 672 return -EPERM; 673 /* 674 * if the quartz is off by more than 10% then 675 * something is VERY wrong! 676 */ 677 if (txc->modes & ADJ_TICK && 678 (txc->tick < 900000/USER_HZ || 679 txc->tick > 1100000/USER_HZ)) 680 return -EINVAL; 681 } 682 683 if (txc->modes & ADJ_SETOFFSET) { 684 /* In order to inject time, you gotta be super-user! */ 685 if (!capable(CAP_SYS_TIME)) 686 return -EPERM; 687 688 if (txc->modes & ADJ_NANO) { 689 struct timespec ts; 690 691 ts.tv_sec = txc->time.tv_sec; 692 ts.tv_nsec = txc->time.tv_usec; 693 if (!timespec_inject_offset_valid(&ts)) 694 return -EINVAL; 695 696 } else { 697 if (!timeval_inject_offset_valid(&txc->time)) 698 return -EINVAL; 699 } 700 } 701 702 /* 703 * Check for potential multiplication overflows that can 704 * only happen on 64-bit systems: 705 */ 706 if ((txc->modes & ADJ_FREQUENCY) && (BITS_PER_LONG == 64)) { 707 if (LLONG_MIN / PPM_SCALE > txc->freq) 708 return -EINVAL; 709 if (LLONG_MAX / PPM_SCALE < txc->freq) 710 return -EINVAL; 711 } 712 713 return 0; 714 } 715 716 717 /* 718 * adjtimex mainly allows reading (and writing, if superuser) of 719 * kernel time-keeping variables. used by xntpd. 720 */ 721 int __do_adjtimex(struct timex *txc, struct timespec64 *ts, s32 *time_tai) 722 { 723 int result; 724 725 if (txc->modes & ADJ_ADJTIME) { 726 long save_adjust = time_adjust; 727 728 if (!(txc->modes & ADJ_OFFSET_READONLY)) { 729 /* adjtime() is independent from ntp_adjtime() */ 730 time_adjust = txc->offset; 731 ntp_update_frequency(); 732 } 733 txc->offset = save_adjust; 734 } else { 735 736 /* If there are input parameters, then process them: */ 737 if (txc->modes) 738 process_adjtimex_modes(txc, ts, time_tai); 739 740 txc->offset = shift_right(time_offset * NTP_INTERVAL_FREQ, 741 NTP_SCALE_SHIFT); 742 if (!(time_status & STA_NANO)) 743 txc->offset /= NSEC_PER_USEC; 744 } 745 746 result = time_state; /* mostly `TIME_OK' */ 747 /* check for errors */ 748 if (is_error_status(time_status)) 749 result = TIME_ERROR; 750 751 txc->freq = shift_right((time_freq >> PPM_SCALE_INV_SHIFT) * 752 PPM_SCALE_INV, NTP_SCALE_SHIFT); 753 txc->maxerror = time_maxerror; 754 txc->esterror = time_esterror; 755 txc->status = time_status; 756 txc->constant = time_constant; 757 txc->precision = 1; 758 txc->tolerance = MAXFREQ_SCALED / PPM_SCALE; 759 txc->tick = tick_usec; 760 txc->tai = *time_tai; 761 762 /* fill PPS status fields */ 763 pps_fill_timex(txc); 764 765 txc->time.tv_sec = (time_t)ts->tv_sec; 766 txc->time.tv_usec = ts->tv_nsec; 767 if (!(time_status & STA_NANO)) 768 txc->time.tv_usec /= NSEC_PER_USEC; 769 770 /* Handle leapsec adjustments */ 771 if (unlikely(ts->tv_sec >= ntp_next_leap_sec)) { 772 if ((time_state == TIME_INS) && (time_status & STA_INS)) { 773 result = TIME_OOP; 774 txc->tai++; 775 txc->time.tv_sec--; 776 } 777 if ((time_state == TIME_DEL) && (time_status & STA_DEL)) { 778 result = TIME_WAIT; 779 txc->tai--; 780 txc->time.tv_sec++; 781 } 782 if ((time_state == TIME_OOP) && 783 (ts->tv_sec == ntp_next_leap_sec)) { 784 result = TIME_WAIT; 785 } 786 } 787 788 return result; 789 } 790 791 #ifdef CONFIG_NTP_PPS 792 793 /* actually struct pps_normtime is good old struct timespec, but it is 794 * semantically different (and it is the reason why it was invented): 795 * pps_normtime.nsec has a range of ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] 796 * while timespec.tv_nsec has a range of [0, NSEC_PER_SEC) */ 797 struct pps_normtime { 798 s64 sec; /* seconds */ 799 long nsec; /* nanoseconds */ 800 }; 801 802 /* normalize the timestamp so that nsec is in the 803 ( -NSEC_PER_SEC / 2, NSEC_PER_SEC / 2 ] interval */ 804 static inline struct pps_normtime pps_normalize_ts(struct timespec64 ts) 805 { 806 struct pps_normtime norm = { 807 .sec = ts.tv_sec, 808 .nsec = ts.tv_nsec 809 }; 810 811 if (norm.nsec > (NSEC_PER_SEC >> 1)) { 812 norm.nsec -= NSEC_PER_SEC; 813 norm.sec++; 814 } 815 816 return norm; 817 } 818 819 /* get current phase correction and jitter */ 820 static inline long pps_phase_filter_get(long *jitter) 821 { 822 *jitter = pps_tf[0] - pps_tf[1]; 823 if (*jitter < 0) 824 *jitter = -*jitter; 825 826 /* TODO: test various filters */ 827 return pps_tf[0]; 828 } 829 830 /* add the sample to the phase filter */ 831 static inline void pps_phase_filter_add(long err) 832 { 833 pps_tf[2] = pps_tf[1]; 834 pps_tf[1] = pps_tf[0]; 835 pps_tf[0] = err; 836 } 837 838 /* decrease frequency calibration interval length. 839 * It is halved after four consecutive unstable intervals. 840 */ 841 static inline void pps_dec_freq_interval(void) 842 { 843 if (--pps_intcnt <= -PPS_INTCOUNT) { 844 pps_intcnt = -PPS_INTCOUNT; 845 if (pps_shift > PPS_INTMIN) { 846 pps_shift--; 847 pps_intcnt = 0; 848 } 849 } 850 } 851 852 /* increase frequency calibration interval length. 853 * It is doubled after four consecutive stable intervals. 854 */ 855 static inline void pps_inc_freq_interval(void) 856 { 857 if (++pps_intcnt >= PPS_INTCOUNT) { 858 pps_intcnt = PPS_INTCOUNT; 859 if (pps_shift < PPS_INTMAX) { 860 pps_shift++; 861 pps_intcnt = 0; 862 } 863 } 864 } 865 866 /* update clock frequency based on MONOTONIC_RAW clock PPS signal 867 * timestamps 868 * 869 * At the end of the calibration interval the difference between the 870 * first and last MONOTONIC_RAW clock timestamps divided by the length 871 * of the interval becomes the frequency update. If the interval was 872 * too long, the data are discarded. 873 * Returns the difference between old and new frequency values. 874 */ 875 static long hardpps_update_freq(struct pps_normtime freq_norm) 876 { 877 long delta, delta_mod; 878 s64 ftemp; 879 880 /* check if the frequency interval was too long */ 881 if (freq_norm.sec > (2 << pps_shift)) { 882 time_status |= STA_PPSERROR; 883 pps_errcnt++; 884 pps_dec_freq_interval(); 885 printk_deferred(KERN_ERR 886 "hardpps: PPSERROR: interval too long - %lld s\n", 887 freq_norm.sec); 888 return 0; 889 } 890 891 /* here the raw frequency offset and wander (stability) is 892 * calculated. If the wander is less than the wander threshold 893 * the interval is increased; otherwise it is decreased. 894 */ 895 ftemp = div_s64(((s64)(-freq_norm.nsec)) << NTP_SCALE_SHIFT, 896 freq_norm.sec); 897 delta = shift_right(ftemp - pps_freq, NTP_SCALE_SHIFT); 898 pps_freq = ftemp; 899 if (delta > PPS_MAXWANDER || delta < -PPS_MAXWANDER) { 900 printk_deferred(KERN_WARNING 901 "hardpps: PPSWANDER: change=%ld\n", delta); 902 time_status |= STA_PPSWANDER; 903 pps_stbcnt++; 904 pps_dec_freq_interval(); 905 } else { /* good sample */ 906 pps_inc_freq_interval(); 907 } 908 909 /* the stability metric is calculated as the average of recent 910 * frequency changes, but is used only for performance 911 * monitoring 912 */ 913 delta_mod = delta; 914 if (delta_mod < 0) 915 delta_mod = -delta_mod; 916 pps_stabil += (div_s64(((s64)delta_mod) << 917 (NTP_SCALE_SHIFT - SHIFT_USEC), 918 NSEC_PER_USEC) - pps_stabil) >> PPS_INTMIN; 919 920 /* if enabled, the system clock frequency is updated */ 921 if ((time_status & STA_PPSFREQ) != 0 && 922 (time_status & STA_FREQHOLD) == 0) { 923 time_freq = pps_freq; 924 ntp_update_frequency(); 925 } 926 927 return delta; 928 } 929 930 /* correct REALTIME clock phase error against PPS signal */ 931 static void hardpps_update_phase(long error) 932 { 933 long correction = -error; 934 long jitter; 935 936 /* add the sample to the median filter */ 937 pps_phase_filter_add(correction); 938 correction = pps_phase_filter_get(&jitter); 939 940 /* Nominal jitter is due to PPS signal noise. If it exceeds the 941 * threshold, the sample is discarded; otherwise, if so enabled, 942 * the time offset is updated. 943 */ 944 if (jitter > (pps_jitter << PPS_POPCORN)) { 945 printk_deferred(KERN_WARNING 946 "hardpps: PPSJITTER: jitter=%ld, limit=%ld\n", 947 jitter, (pps_jitter << PPS_POPCORN)); 948 time_status |= STA_PPSJITTER; 949 pps_jitcnt++; 950 } else if (time_status & STA_PPSTIME) { 951 /* correct the time using the phase offset */ 952 time_offset = div_s64(((s64)correction) << NTP_SCALE_SHIFT, 953 NTP_INTERVAL_FREQ); 954 /* cancel running adjtime() */ 955 time_adjust = 0; 956 } 957 /* update jitter */ 958 pps_jitter += (jitter - pps_jitter) >> PPS_INTMIN; 959 } 960 961 /* 962 * __hardpps() - discipline CPU clock oscillator to external PPS signal 963 * 964 * This routine is called at each PPS signal arrival in order to 965 * discipline the CPU clock oscillator to the PPS signal. It takes two 966 * parameters: REALTIME and MONOTONIC_RAW clock timestamps. The former 967 * is used to correct clock phase error and the latter is used to 968 * correct the frequency. 969 * 970 * This code is based on David Mills's reference nanokernel 971 * implementation. It was mostly rewritten but keeps the same idea. 972 */ 973 void __hardpps(const struct timespec64 *phase_ts, const struct timespec64 *raw_ts) 974 { 975 struct pps_normtime pts_norm, freq_norm; 976 977 pts_norm = pps_normalize_ts(*phase_ts); 978 979 /* clear the error bits, they will be set again if needed */ 980 time_status &= ~(STA_PPSJITTER | STA_PPSWANDER | STA_PPSERROR); 981 982 /* indicate signal presence */ 983 time_status |= STA_PPSSIGNAL; 984 pps_valid = PPS_VALID; 985 986 /* when called for the first time, 987 * just start the frequency interval */ 988 if (unlikely(pps_fbase.tv_sec == 0)) { 989 pps_fbase = *raw_ts; 990 return; 991 } 992 993 /* ok, now we have a base for frequency calculation */ 994 freq_norm = pps_normalize_ts(timespec64_sub(*raw_ts, pps_fbase)); 995 996 /* check that the signal is in the range 997 * [1s - MAXFREQ us, 1s + MAXFREQ us], otherwise reject it */ 998 if ((freq_norm.sec == 0) || 999 (freq_norm.nsec > MAXFREQ * freq_norm.sec) || 1000 (freq_norm.nsec < -MAXFREQ * freq_norm.sec)) { 1001 time_status |= STA_PPSJITTER; 1002 /* restart the frequency calibration interval */ 1003 pps_fbase = *raw_ts; 1004 printk_deferred(KERN_ERR "hardpps: PPSJITTER: bad pulse\n"); 1005 return; 1006 } 1007 1008 /* signal is ok */ 1009 1010 /* check if the current frequency interval is finished */ 1011 if (freq_norm.sec >= (1 << pps_shift)) { 1012 pps_calcnt++; 1013 /* restart the frequency calibration interval */ 1014 pps_fbase = *raw_ts; 1015 hardpps_update_freq(freq_norm); 1016 } 1017 1018 hardpps_update_phase(pts_norm.nsec); 1019 1020 } 1021 #endif /* CONFIG_NTP_PPS */ 1022 1023 static int __init ntp_tick_adj_setup(char *str) 1024 { 1025 int rc = kstrtol(str, 0, (long *)&ntp_tick_adj); 1026 1027 if (rc) 1028 return rc; 1029 ntp_tick_adj <<= NTP_SCALE_SHIFT; 1030 1031 return 1; 1032 } 1033 1034 __setup("ntp_tick_adj=", ntp_tick_adj_setup); 1035 1036 void __init ntp_init(void) 1037 { 1038 ntp_clear(); 1039 } 1040