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