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