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