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