Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_ntptime.c
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1 /*- 2 *********************************************************************** 3 * * 4 * Copyright (c) David L. Mills 1993-2001 * 5 * * 6 * Permission to use, copy, modify, and distribute this software and * 7 * its documentation for any purpose and without fee is hereby * 8 * granted, provided that the above copyright notice appears in all * 9 * copies and that both the copyright notice and this permission * 10 * notice appear in supporting documentation, and that the name * 11 * University of Delaware not be used in advertising or publicity * 12 * pertaining to distribution of the software without specific, * 13 * written prior permission. The University of Delaware makes no * 14 * representations about the suitability this software for any * 15 * purpose. It is provided "as is" without express or implied * 16 * warranty. * 17 * * 18 **********************************************************************/ 19 20 /* 21 * Adapted from the original sources for FreeBSD and timecounters by: 22 * Poul-Henning Kamp <phk@FreeBSD.org>. 23 * 24 * The 32bit version of the "LP" macros seems a bit past its "sell by" 25 * date so I have retained only the 64bit version and included it directly 26 * in this file. 27 * 28 * Only minor changes done to interface with the timecounters over in 29 * sys/kern/kern_clock.c. Some of the comments below may be (even more) 30 * confusing and/or plain wrong in that context. 31 */ 32 33 #include <sys/cdefs.h> 34 __FBSDID("$FreeBSD$"); 35 36 #include "opt_ntp.h" 37 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/sysproto.h> 41 #include <sys/eventhandler.h> 42 #include <sys/kernel.h> 43 #include <sys/priv.h> 44 #include <sys/proc.h> 45 #include <sys/lock.h> 46 #include <sys/mutex.h> 47 #include <sys/time.h> 48 #include <sys/timex.h> 49 #include <sys/timetc.h> 50 #include <sys/timepps.h> 51 #include <sys/syscallsubr.h> 52 #include <sys/sysctl.h> 53 54 #ifdef PPS_SYNC 55 FEATURE(pps_sync, "Support usage of external PPS signal by kernel PLL"); 56 #endif 57 58 /* 59 * Single-precision macros for 64-bit machines 60 */ 61 typedef int64_t l_fp; 62 #define L_ADD(v, u) ((v) += (u)) 63 #define L_SUB(v, u) ((v) -= (u)) 64 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32) 65 #define L_NEG(v) ((v) = -(v)) 66 #define L_RSHIFT(v, n) \ 67 do { \ 68 if ((v) < 0) \ 69 (v) = -(-(v) >> (n)); \ 70 else \ 71 (v) = (v) >> (n); \ 72 } while (0) 73 #define L_MPY(v, a) ((v) *= (a)) 74 #define L_CLR(v) ((v) = 0) 75 #define L_ISNEG(v) ((v) < 0) 76 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32) 77 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 78 79 /* 80 * Generic NTP kernel interface 81 * 82 * These routines constitute the Network Time Protocol (NTP) interfaces 83 * for user and daemon application programs. The ntp_gettime() routine 84 * provides the time, maximum error (synch distance) and estimated error 85 * (dispersion) to client user application programs. The ntp_adjtime() 86 * routine is used by the NTP daemon to adjust the system clock to an 87 * externally derived time. The time offset and related variables set by 88 * this routine are used by other routines in this module to adjust the 89 * phase and frequency of the clock discipline loop which controls the 90 * system clock. 91 * 92 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 93 * defined), the time at each tick interrupt is derived directly from 94 * the kernel time variable. When the kernel time is reckoned in 95 * microseconds, (NTP_NANO undefined), the time is derived from the 96 * kernel time variable together with a variable representing the 97 * leftover nanoseconds at the last tick interrupt. In either case, the 98 * current nanosecond time is reckoned from these values plus an 99 * interpolated value derived by the clock routines in another 100 * architecture-specific module. The interpolation can use either a 101 * dedicated counter or a processor cycle counter (PCC) implemented in 102 * some architectures. 103 * 104 * Note that all routines must run at priority splclock or higher. 105 */ 106 /* 107 * Phase/frequency-lock loop (PLL/FLL) definitions 108 * 109 * The nanosecond clock discipline uses two variable types, time 110 * variables and frequency variables. Both types are represented as 64- 111 * bit fixed-point quantities with the decimal point between two 32-bit 112 * halves. On a 32-bit machine, each half is represented as a single 113 * word and mathematical operations are done using multiple-precision 114 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 115 * used. 116 * 117 * A time variable is a signed 64-bit fixed-point number in ns and 118 * fraction. It represents the remaining time offset to be amortized 119 * over succeeding tick interrupts. The maximum time offset is about 120 * 0.5 s and the resolution is about 2.3e-10 ns. 121 * 122 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 123 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 124 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 125 * |s s s| ns | 126 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 127 * | fraction | 128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 * 130 * A frequency variable is a signed 64-bit fixed-point number in ns/s 131 * and fraction. It represents the ns and fraction to be added to the 132 * kernel time variable at each second. The maximum frequency offset is 133 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 134 * 135 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 136 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 137 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 138 * |s s s s s s s s s s s s s| ns/s | 139 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 140 * | fraction | 141 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 142 */ 143 /* 144 * The following variables establish the state of the PLL/FLL and the 145 * residual time and frequency offset of the local clock. 146 */ 147 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 148 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 149 150 static int time_state = TIME_OK; /* clock state */ 151 int time_status = STA_UNSYNC; /* clock status bits */ 152 static long time_tai; /* TAI offset (s) */ 153 static long time_monitor; /* last time offset scaled (ns) */ 154 static long time_constant; /* poll interval (shift) (s) */ 155 static long time_precision = 1; /* clock precision (ns) */ 156 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 157 long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 158 static long time_reftime; /* uptime at last adjustment (s) */ 159 static l_fp time_offset; /* time offset (ns) */ 160 static l_fp time_freq; /* frequency offset (ns/s) */ 161 static l_fp time_adj; /* tick adjust (ns/s) */ 162 163 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 164 165 static struct mtx ntp_lock; 166 MTX_SYSINIT(ntp, &ntp_lock, "ntp", MTX_SPIN); 167 168 #define NTP_LOCK() mtx_lock_spin(&ntp_lock) 169 #define NTP_UNLOCK() mtx_unlock_spin(&ntp_lock) 170 #define NTP_ASSERT_LOCKED() mtx_assert(&ntp_lock, MA_OWNED) 171 172 #ifdef PPS_SYNC 173 /* 174 * The following variables are used when a pulse-per-second (PPS) signal 175 * is available and connected via a modem control lead. They establish 176 * the engineering parameters of the clock discipline loop when 177 * controlled by the PPS signal. 178 */ 179 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 180 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 181 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 182 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 183 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 184 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 185 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 186 187 static struct timespec pps_tf[3]; /* phase median filter */ 188 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 189 static long pps_fcount; /* frequency accumulator */ 190 static long pps_jitter; /* nominal jitter (ns) */ 191 static long pps_stabil; /* nominal stability (scaled ns/s) */ 192 static long pps_lastsec; /* time at last calibration (s) */ 193 static int pps_valid; /* signal watchdog counter */ 194 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 195 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 196 static int pps_intcnt; /* wander counter */ 197 198 /* 199 * PPS signal quality monitors 200 */ 201 static long pps_calcnt; /* calibration intervals */ 202 static long pps_jitcnt; /* jitter limit exceeded */ 203 static long pps_stbcnt; /* stability limit exceeded */ 204 static long pps_errcnt; /* calibration errors */ 205 #endif /* PPS_SYNC */ 206 /* 207 * End of phase/frequency-lock loop (PLL/FLL) definitions 208 */ 209 210 static void hardupdate(long offset); 211 static void ntp_gettime1(struct ntptimeval *ntvp); 212 static bool ntp_is_time_error(int tsl); 213 214 static bool 215 ntp_is_time_error(int tsl) 216 { 217 218 /* 219 * Status word error decode. If any of these conditions occur, 220 * an error is returned, instead of the status word. Most 221 * applications will care only about the fact the system clock 222 * may not be trusted, not about the details. 223 * 224 * Hardware or software error 225 */ 226 if ((tsl & (STA_UNSYNC | STA_CLOCKERR)) || 227 228 /* 229 * PPS signal lost when either time or frequency synchronization 230 * requested 231 */ 232 (tsl & (STA_PPSFREQ | STA_PPSTIME) && 233 !(tsl & STA_PPSSIGNAL)) || 234 235 /* 236 * PPS jitter exceeded when time synchronization requested 237 */ 238 (tsl & STA_PPSTIME && tsl & STA_PPSJITTER) || 239 240 /* 241 * PPS wander exceeded or calibration error when frequency 242 * synchronization requested 243 */ 244 (tsl & STA_PPSFREQ && 245 tsl & (STA_PPSWANDER | STA_PPSERROR))) 246 return (true); 247 248 return (false); 249 } 250 251 static void 252 ntp_gettime1(struct ntptimeval *ntvp) 253 { 254 struct timespec atv; /* nanosecond time */ 255 256 NTP_ASSERT_LOCKED(); 257 258 nanotime(&atv); 259 ntvp->time.tv_sec = atv.tv_sec; 260 ntvp->time.tv_nsec = atv.tv_nsec; 261 ntvp->maxerror = time_maxerror; 262 ntvp->esterror = time_esterror; 263 ntvp->tai = time_tai; 264 ntvp->time_state = time_state; 265 266 if (ntp_is_time_error(time_status)) 267 ntvp->time_state = TIME_ERROR; 268 } 269 270 /* 271 * ntp_gettime() - NTP user application interface 272 * 273 * See the timex.h header file for synopsis and API description. Note that 274 * the TAI offset is returned in the ntvtimeval.tai structure member. 275 */ 276 #ifndef _SYS_SYSPROTO_H_ 277 struct ntp_gettime_args { 278 struct ntptimeval *ntvp; 279 }; 280 #endif 281 /* ARGSUSED */ 282 int 283 sys_ntp_gettime(struct thread *td, struct ntp_gettime_args *uap) 284 { 285 struct ntptimeval ntv; 286 287 memset(&ntv, 0, sizeof(ntv)); 288 289 NTP_LOCK(); 290 ntp_gettime1(&ntv); 291 NTP_UNLOCK(); 292 293 td->td_retval[0] = ntv.time_state; 294 return (copyout(&ntv, uap->ntvp, sizeof(ntv))); 295 } 296 297 static int 298 ntp_sysctl(SYSCTL_HANDLER_ARGS) 299 { 300 struct ntptimeval ntv; /* temporary structure */ 301 302 memset(&ntv, 0, sizeof(ntv)); 303 304 NTP_LOCK(); 305 ntp_gettime1(&ntv); 306 NTP_UNLOCK(); 307 308 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req)); 309 } 310 311 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 312 ""); 313 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE | CTLFLAG_RD | 314 CTLFLAG_MPSAFE, 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", 315 ""); 316 317 #ifdef PPS_SYNC 318 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, 319 &pps_shiftmax, 0, "Max interval duration (sec) (shift)"); 320 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, 321 &pps_shift, 0, "Interval duration (sec) (shift)"); 322 SYSCTL_LONG(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, 323 &time_monitor, 0, "Last time offset scaled (ns)"); 324 325 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD | CTLFLAG_MPSAFE, 326 &pps_freq, 0, 327 "Scaled frequency offset (ns/sec)"); 328 SYSCTL_S64(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD | CTLFLAG_MPSAFE, 329 &time_freq, 0, 330 "Frequency offset (ns/sec)"); 331 #endif 332 333 /* 334 * ntp_adjtime() - NTP daemon application interface 335 * 336 * See the timex.h header file for synopsis and API description. Note that 337 * the timex.constant structure member has a dual purpose to set the time 338 * constant and to set the TAI offset. 339 */ 340 int 341 kern_ntp_adjtime(struct thread *td, struct timex *ntv, int *retvalp) 342 { 343 long freq; /* frequency ns/s) */ 344 int modes; /* mode bits from structure */ 345 int error, retval; 346 347 /* 348 * Update selected clock variables - only the superuser can 349 * change anything. Note that there is no error checking here on 350 * the assumption the superuser should know what it is doing. 351 * Note that either the time constant or TAI offset are loaded 352 * from the ntv.constant member, depending on the mode bits. If 353 * the STA_PLL bit in the status word is cleared, the state and 354 * status words are reset to the initial values at boot. 355 */ 356 modes = ntv->modes; 357 error = 0; 358 if (modes) 359 error = priv_check(td, PRIV_NTP_ADJTIME); 360 if (error != 0) 361 return (error); 362 NTP_LOCK(); 363 if (modes & MOD_MAXERROR) 364 time_maxerror = ntv->maxerror; 365 if (modes & MOD_ESTERROR) 366 time_esterror = ntv->esterror; 367 if (modes & MOD_STATUS) { 368 if (time_status & STA_PLL && !(ntv->status & STA_PLL)) { 369 time_state = TIME_OK; 370 time_status = STA_UNSYNC; 371 #ifdef PPS_SYNC 372 pps_shift = PPS_FAVG; 373 #endif /* PPS_SYNC */ 374 } 375 time_status &= STA_RONLY; 376 time_status |= ntv->status & ~STA_RONLY; 377 } 378 if (modes & MOD_TIMECONST) { 379 if (ntv->constant < 0) 380 time_constant = 0; 381 else if (ntv->constant > MAXTC) 382 time_constant = MAXTC; 383 else 384 time_constant = ntv->constant; 385 } 386 if (modes & MOD_TAI) { 387 if (ntv->constant > 0) /* XXX zero & negative numbers ? */ 388 time_tai = ntv->constant; 389 } 390 #ifdef PPS_SYNC 391 if (modes & MOD_PPSMAX) { 392 if (ntv->shift < PPS_FAVG) 393 pps_shiftmax = PPS_FAVG; 394 else if (ntv->shift > PPS_FAVGMAX) 395 pps_shiftmax = PPS_FAVGMAX; 396 else 397 pps_shiftmax = ntv->shift; 398 } 399 #endif /* PPS_SYNC */ 400 if (modes & MOD_NANO) 401 time_status |= STA_NANO; 402 if (modes & MOD_MICRO) 403 time_status &= ~STA_NANO; 404 if (modes & MOD_CLKB) 405 time_status |= STA_CLK; 406 if (modes & MOD_CLKA) 407 time_status &= ~STA_CLK; 408 if (modes & MOD_FREQUENCY) { 409 freq = (ntv->freq * 1000LL) >> 16; 410 if (freq > MAXFREQ) 411 L_LINT(time_freq, MAXFREQ); 412 else if (freq < -MAXFREQ) 413 L_LINT(time_freq, -MAXFREQ); 414 else { 415 /* 416 * ntv->freq is [PPM * 2^16] = [us/s * 2^16] 417 * time_freq is [ns/s * 2^32] 418 */ 419 time_freq = ntv->freq * 1000LL * 65536LL; 420 } 421 #ifdef PPS_SYNC 422 pps_freq = time_freq; 423 #endif /* PPS_SYNC */ 424 } 425 if (modes & MOD_OFFSET) { 426 if (time_status & STA_NANO) 427 hardupdate(ntv->offset); 428 else 429 hardupdate(ntv->offset * 1000); 430 } 431 432 /* 433 * Retrieve all clock variables. Note that the TAI offset is 434 * returned only by ntp_gettime(); 435 */ 436 if (time_status & STA_NANO) 437 ntv->offset = L_GINT(time_offset); 438 else 439 ntv->offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 440 ntv->freq = L_GINT((time_freq / 1000LL) << 16); 441 ntv->maxerror = time_maxerror; 442 ntv->esterror = time_esterror; 443 ntv->status = time_status; 444 ntv->constant = time_constant; 445 if (time_status & STA_NANO) 446 ntv->precision = time_precision; 447 else 448 ntv->precision = time_precision / 1000; 449 ntv->tolerance = MAXFREQ * SCALE_PPM; 450 #ifdef PPS_SYNC 451 ntv->shift = pps_shift; 452 ntv->ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 453 if (time_status & STA_NANO) 454 ntv->jitter = pps_jitter; 455 else 456 ntv->jitter = pps_jitter / 1000; 457 ntv->stabil = pps_stabil; 458 ntv->calcnt = pps_calcnt; 459 ntv->errcnt = pps_errcnt; 460 ntv->jitcnt = pps_jitcnt; 461 ntv->stbcnt = pps_stbcnt; 462 #endif /* PPS_SYNC */ 463 retval = ntp_is_time_error(time_status) ? TIME_ERROR : time_state; 464 NTP_UNLOCK(); 465 466 *retvalp = retval; 467 return (0); 468 } 469 470 #ifndef _SYS_SYSPROTO_H_ 471 struct ntp_adjtime_args { 472 struct timex *tp; 473 }; 474 #endif 475 476 int 477 sys_ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 478 { 479 struct timex ntv; 480 int error, retval; 481 482 error = copyin(uap->tp, &ntv, sizeof(ntv)); 483 if (error == 0) { 484 error = kern_ntp_adjtime(td, &ntv, &retval); 485 if (error == 0) { 486 error = copyout(&ntv, uap->tp, sizeof(ntv)); 487 if (error == 0) 488 td->td_retval[0] = retval; 489 } 490 } 491 return (error); 492 } 493 494 /* 495 * second_overflow() - called after ntp_tick_adjust() 496 * 497 * This routine is ordinarily called immediately following the above 498 * routine ntp_tick_adjust(). While these two routines are normally 499 * combined, they are separated here only for the purposes of 500 * simulation. 501 */ 502 void 503 ntp_update_second(int64_t *adjustment, time_t *newsec) 504 { 505 int tickrate; 506 l_fp ftemp; /* 32/64-bit temporary */ 507 508 NTP_LOCK(); 509 510 /* 511 * On rollover of the second both the nanosecond and microsecond 512 * clocks are updated and the state machine cranked as 513 * necessary. The phase adjustment to be used for the next 514 * second is calculated and the maximum error is increased by 515 * the tolerance. 516 */ 517 time_maxerror += MAXFREQ / 1000; 518 519 /* 520 * Leap second processing. If in leap-insert state at 521 * the end of the day, the system clock is set back one 522 * second; if in leap-delete state, the system clock is 523 * set ahead one second. The nano_time() routine or 524 * external clock driver will insure that reported time 525 * is always monotonic. 526 */ 527 switch (time_state) { 528 /* 529 * No warning. 530 */ 531 case TIME_OK: 532 if (time_status & STA_INS) 533 time_state = TIME_INS; 534 else if (time_status & STA_DEL) 535 time_state = TIME_DEL; 536 break; 537 538 /* 539 * Insert second 23:59:60 following second 540 * 23:59:59. 541 */ 542 case TIME_INS: 543 if (!(time_status & STA_INS)) 544 time_state = TIME_OK; 545 else if ((*newsec) % 86400 == 0) { 546 (*newsec)--; 547 time_state = TIME_OOP; 548 time_tai++; 549 } 550 break; 551 552 /* 553 * Delete second 23:59:59. 554 */ 555 case TIME_DEL: 556 if (!(time_status & STA_DEL)) 557 time_state = TIME_OK; 558 else if (((*newsec) + 1) % 86400 == 0) { 559 (*newsec)++; 560 time_tai--; 561 time_state = TIME_WAIT; 562 } 563 break; 564 565 /* 566 * Insert second in progress. 567 */ 568 case TIME_OOP: 569 time_state = TIME_WAIT; 570 break; 571 572 /* 573 * Wait for status bits to clear. 574 */ 575 case TIME_WAIT: 576 if (!(time_status & (STA_INS | STA_DEL))) 577 time_state = TIME_OK; 578 } 579 580 /* 581 * Compute the total time adjustment for the next second 582 * in ns. The offset is reduced by a factor depending on 583 * whether the PPS signal is operating. Note that the 584 * value is in effect scaled by the clock frequency, 585 * since the adjustment is added at each tick interrupt. 586 */ 587 ftemp = time_offset; 588 #ifdef PPS_SYNC 589 /* XXX even if PPS signal dies we should finish adjustment ? */ 590 if (time_status & STA_PPSTIME && time_status & 591 STA_PPSSIGNAL) 592 L_RSHIFT(ftemp, pps_shift); 593 else 594 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 595 #else 596 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 597 #endif /* PPS_SYNC */ 598 time_adj = ftemp; 599 L_SUB(time_offset, ftemp); 600 L_ADD(time_adj, time_freq); 601 602 /* 603 * Apply any correction from adjtime(2). If more than one second 604 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500 PPM) 605 * until the last second is slewed the final < 500 usecs. 606 */ 607 if (time_adjtime != 0) { 608 if (time_adjtime > 1000000) 609 tickrate = 5000; 610 else if (time_adjtime < -1000000) 611 tickrate = -5000; 612 else if (time_adjtime > 500) 613 tickrate = 500; 614 else if (time_adjtime < -500) 615 tickrate = -500; 616 else 617 tickrate = time_adjtime; 618 time_adjtime -= tickrate; 619 L_LINT(ftemp, tickrate * 1000); 620 L_ADD(time_adj, ftemp); 621 } 622 *adjustment = time_adj; 623 624 #ifdef PPS_SYNC 625 if (pps_valid > 0) 626 pps_valid--; 627 else 628 time_status &= ~STA_PPSSIGNAL; 629 #endif /* PPS_SYNC */ 630 631 NTP_UNLOCK(); 632 } 633 634 /* 635 * hardupdate() - local clock update 636 * 637 * This routine is called by ntp_adjtime() to update the local clock 638 * phase and frequency. The implementation is of an adaptive-parameter, 639 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 640 * time and frequency offset estimates for each call. If the kernel PPS 641 * discipline code is configured (PPS_SYNC), the PPS signal itself 642 * determines the new time offset, instead of the calling argument. 643 * Presumably, calls to ntp_adjtime() occur only when the caller 644 * believes the local clock is valid within some bound (+-128 ms with 645 * NTP). If the caller's time is far different than the PPS time, an 646 * argument will ensue, and it's not clear who will lose. 647 * 648 * For uncompensated quartz crystal oscillators and nominal update 649 * intervals less than 256 s, operation should be in phase-lock mode, 650 * where the loop is disciplined to phase. For update intervals greater 651 * than 1024 s, operation should be in frequency-lock mode, where the 652 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 653 * is selected by the STA_MODE status bit. 654 */ 655 static void 656 hardupdate(offset) 657 long offset; /* clock offset (ns) */ 658 { 659 long mtemp; 660 l_fp ftemp; 661 662 NTP_ASSERT_LOCKED(); 663 664 /* 665 * Select how the phase is to be controlled and from which 666 * source. If the PPS signal is present and enabled to 667 * discipline the time, the PPS offset is used; otherwise, the 668 * argument offset is used. 669 */ 670 if (!(time_status & STA_PLL)) 671 return; 672 if (!(time_status & STA_PPSTIME && time_status & 673 STA_PPSSIGNAL)) { 674 if (offset > MAXPHASE) 675 time_monitor = MAXPHASE; 676 else if (offset < -MAXPHASE) 677 time_monitor = -MAXPHASE; 678 else 679 time_monitor = offset; 680 L_LINT(time_offset, time_monitor); 681 } 682 683 /* 684 * Select how the frequency is to be controlled and in which 685 * mode (PLL or FLL). If the PPS signal is present and enabled 686 * to discipline the frequency, the PPS frequency is used; 687 * otherwise, the argument offset is used to compute it. 688 */ 689 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 690 time_reftime = time_uptime; 691 return; 692 } 693 if (time_status & STA_FREQHOLD || time_reftime == 0) 694 time_reftime = time_uptime; 695 mtemp = time_uptime - time_reftime; 696 L_LINT(ftemp, time_monitor); 697 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 698 L_MPY(ftemp, mtemp); 699 L_ADD(time_freq, ftemp); 700 time_status &= ~STA_MODE; 701 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 702 MAXSEC)) { 703 L_LINT(ftemp, (time_monitor << 4) / mtemp); 704 L_RSHIFT(ftemp, SHIFT_FLL + 4); 705 L_ADD(time_freq, ftemp); 706 time_status |= STA_MODE; 707 } 708 time_reftime = time_uptime; 709 if (L_GINT(time_freq) > MAXFREQ) 710 L_LINT(time_freq, MAXFREQ); 711 else if (L_GINT(time_freq) < -MAXFREQ) 712 L_LINT(time_freq, -MAXFREQ); 713 } 714 715 #ifdef PPS_SYNC 716 /* 717 * hardpps() - discipline CPU clock oscillator to external PPS signal 718 * 719 * This routine is called at each PPS interrupt in order to discipline 720 * the CPU clock oscillator to the PPS signal. There are two independent 721 * first-order feedback loops, one for the phase, the other for the 722 * frequency. The phase loop measures and grooms the PPS phase offset 723 * and leaves it in a handy spot for the seconds overflow routine. The 724 * frequency loop averages successive PPS phase differences and 725 * calculates the PPS frequency offset, which is also processed by the 726 * seconds overflow routine. The code requires the caller to capture the 727 * time and architecture-dependent hardware counter values in 728 * nanoseconds at the on-time PPS signal transition. 729 * 730 * Note that, on some Unix systems this routine runs at an interrupt 731 * priority level higher than the timer interrupt routine hardclock(). 732 * Therefore, the variables used are distinct from the hardclock() 733 * variables, except for the actual time and frequency variables, which 734 * are determined by this routine and updated atomically. 735 * 736 * tsp - time at PPS 737 * nsec - hardware counter at PPS 738 */ 739 void 740 hardpps(struct timespec *tsp, long nsec) 741 { 742 long u_sec, u_nsec, v_nsec; /* temps */ 743 l_fp ftemp; 744 745 NTP_LOCK(); 746 747 /* 748 * The signal is first processed by a range gate and frequency 749 * discriminator. The range gate rejects noise spikes outside 750 * the range +-500 us. The frequency discriminator rejects input 751 * signals with apparent frequency outside the range 1 +-500 752 * PPM. If two hits occur in the same second, we ignore the 753 * later hit; if not and a hit occurs outside the range gate, 754 * keep the later hit for later comparison, but do not process 755 * it. 756 */ 757 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 758 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 759 pps_valid = PPS_VALID; 760 u_sec = tsp->tv_sec; 761 u_nsec = tsp->tv_nsec; 762 if (u_nsec >= (NANOSECOND >> 1)) { 763 u_nsec -= NANOSECOND; 764 u_sec++; 765 } 766 v_nsec = u_nsec - pps_tf[0].tv_nsec; 767 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - MAXFREQ) 768 goto out; 769 pps_tf[2] = pps_tf[1]; 770 pps_tf[1] = pps_tf[0]; 771 pps_tf[0].tv_sec = u_sec; 772 pps_tf[0].tv_nsec = u_nsec; 773 774 /* 775 * Compute the difference between the current and previous 776 * counter values. If the difference exceeds 0.5 s, assume it 777 * has wrapped around, so correct 1.0 s. If the result exceeds 778 * the tick interval, the sample point has crossed a tick 779 * boundary during the last second, so correct the tick. Very 780 * intricate. 781 */ 782 u_nsec = nsec; 783 if (u_nsec > (NANOSECOND >> 1)) 784 u_nsec -= NANOSECOND; 785 else if (u_nsec < -(NANOSECOND >> 1)) 786 u_nsec += NANOSECOND; 787 pps_fcount += u_nsec; 788 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 789 goto out; 790 time_status &= ~STA_PPSJITTER; 791 792 /* 793 * A three-stage median filter is used to help denoise the PPS 794 * time. The median sample becomes the time offset estimate; the 795 * difference between the other two samples becomes the time 796 * dispersion (jitter) estimate. 797 */ 798 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 799 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 800 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 801 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 802 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 803 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 804 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 805 } else { 806 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 807 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 808 } 809 } else { 810 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 811 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 812 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 813 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 814 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 815 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 816 } else { 817 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 818 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 819 } 820 } 821 822 /* 823 * Nominal jitter is due to PPS signal noise and interrupt 824 * latency. If it exceeds the popcorn threshold, the sample is 825 * discarded. otherwise, if so enabled, the time offset is 826 * updated. We can tolerate a modest loss of data here without 827 * much degrading time accuracy. 828 * 829 * The measurements being checked here were made with the system 830 * timecounter, so the popcorn threshold is not allowed to fall below 831 * the number of nanoseconds in two ticks of the timecounter. For a 832 * timecounter running faster than 1 GHz the lower bound is 2ns, just 833 * to avoid a nonsensical threshold of zero. 834 */ 835 if (u_nsec > lmax(pps_jitter << PPS_POPCORN, 836 2 * (NANOSECOND / (long)qmin(NANOSECOND, tc_getfrequency())))) { 837 time_status |= STA_PPSJITTER; 838 pps_jitcnt++; 839 } else if (time_status & STA_PPSTIME) { 840 time_monitor = -v_nsec; 841 L_LINT(time_offset, time_monitor); 842 } 843 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 844 u_sec = pps_tf[0].tv_sec - pps_lastsec; 845 if (u_sec < (1 << pps_shift)) 846 goto out; 847 848 /* 849 * At the end of the calibration interval the difference between 850 * the first and last counter values becomes the scaled 851 * frequency. It will later be divided by the length of the 852 * interval to determine the frequency update. If the frequency 853 * exceeds a sanity threshold, or if the actual calibration 854 * interval is not equal to the expected length, the data are 855 * discarded. We can tolerate a modest loss of data here without 856 * much degrading frequency accuracy. 857 */ 858 pps_calcnt++; 859 v_nsec = -pps_fcount; 860 pps_lastsec = pps_tf[0].tv_sec; 861 pps_fcount = 0; 862 u_nsec = MAXFREQ << pps_shift; 863 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << pps_shift)) { 864 time_status |= STA_PPSERROR; 865 pps_errcnt++; 866 goto out; 867 } 868 869 /* 870 * Here the raw frequency offset and wander (stability) is 871 * calculated. If the wander is less than the wander threshold 872 * for four consecutive averaging intervals, the interval is 873 * doubled; if it is greater than the threshold for four 874 * consecutive intervals, the interval is halved. The scaled 875 * frequency offset is converted to frequency offset. The 876 * stability metric is calculated as the average of recent 877 * frequency changes, but is used only for performance 878 * monitoring. 879 */ 880 L_LINT(ftemp, v_nsec); 881 L_RSHIFT(ftemp, pps_shift); 882 L_SUB(ftemp, pps_freq); 883 u_nsec = L_GINT(ftemp); 884 if (u_nsec > PPS_MAXWANDER) { 885 L_LINT(ftemp, PPS_MAXWANDER); 886 pps_intcnt--; 887 time_status |= STA_PPSWANDER; 888 pps_stbcnt++; 889 } else if (u_nsec < -PPS_MAXWANDER) { 890 L_LINT(ftemp, -PPS_MAXWANDER); 891 pps_intcnt--; 892 time_status |= STA_PPSWANDER; 893 pps_stbcnt++; 894 } else { 895 pps_intcnt++; 896 } 897 if (pps_intcnt >= 4) { 898 pps_intcnt = 4; 899 if (pps_shift < pps_shiftmax) { 900 pps_shift++; 901 pps_intcnt = 0; 902 } 903 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 904 pps_intcnt = -4; 905 if (pps_shift > PPS_FAVG) { 906 pps_shift--; 907 pps_intcnt = 0; 908 } 909 } 910 if (u_nsec < 0) 911 u_nsec = -u_nsec; 912 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 913 914 /* 915 * The PPS frequency is recalculated and clamped to the maximum 916 * MAXFREQ. If enabled, the system clock frequency is updated as 917 * well. 918 */ 919 L_ADD(pps_freq, ftemp); 920 u_nsec = L_GINT(pps_freq); 921 if (u_nsec > MAXFREQ) 922 L_LINT(pps_freq, MAXFREQ); 923 else if (u_nsec < -MAXFREQ) 924 L_LINT(pps_freq, -MAXFREQ); 925 if (time_status & STA_PPSFREQ) 926 time_freq = pps_freq; 927 928 out: 929 NTP_UNLOCK(); 930 } 931 #endif /* PPS_SYNC */ 932 933 #ifndef _SYS_SYSPROTO_H_ 934 struct adjtime_args { 935 struct timeval *delta; 936 struct timeval *olddelta; 937 }; 938 #endif 939 /* ARGSUSED */ 940 int 941 sys_adjtime(struct thread *td, struct adjtime_args *uap) 942 { 943 struct timeval delta, olddelta, *deltap; 944 int error; 945 946 if (uap->delta) { 947 error = copyin(uap->delta, &delta, sizeof(delta)); 948 if (error) 949 return (error); 950 deltap = δ 951 } else 952 deltap = NULL; 953 error = kern_adjtime(td, deltap, &olddelta); 954 if (uap->olddelta && error == 0) 955 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta)); 956 return (error); 957 } 958 959 int 960 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta) 961 { 962 struct timeval atv; 963 int64_t ltr, ltw; 964 int error; 965 966 if (delta != NULL) { 967 error = priv_check(td, PRIV_ADJTIME); 968 if (error != 0) 969 return (error); 970 ltw = (int64_t)delta->tv_sec * 1000000 + delta->tv_usec; 971 } 972 NTP_LOCK(); 973 ltr = time_adjtime; 974 if (delta != NULL) 975 time_adjtime = ltw; 976 NTP_UNLOCK(); 977 if (olddelta != NULL) { 978 atv.tv_sec = ltr / 1000000; 979 atv.tv_usec = ltr % 1000000; 980 if (atv.tv_usec < 0) { 981 atv.tv_usec += 1000000; 982 atv.tv_sec--; 983 } 984 *olddelta = atv; 985 } 986 return (0); 987 } 988 989 static struct callout resettodr_callout; 990 static int resettodr_period = 1800; 991 992 static void 993 periodic_resettodr(void *arg __unused) 994 { 995 996 /* 997 * Read of time_status is lock-less, which is fine since 998 * ntp_is_time_error() operates on the consistent read value. 999 */ 1000 if (!ntp_is_time_error(time_status)) 1001 resettodr(); 1002 if (resettodr_period > 0) 1003 callout_schedule(&resettodr_callout, resettodr_period * hz); 1004 } 1005 1006 static void 1007 shutdown_resettodr(void *arg __unused, int howto __unused) 1008 { 1009 1010 callout_drain(&resettodr_callout); 1011 /* Another unlocked read of time_status */ 1012 if (resettodr_period > 0 && !ntp_is_time_error(time_status)) 1013 resettodr(); 1014 } 1015 1016 static int 1017 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS) 1018 { 1019 int error; 1020 1021 error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req); 1022 if (error || !req->newptr) 1023 return (error); 1024 if (cold) 1025 goto done; 1026 if (resettodr_period == 0) 1027 callout_stop(&resettodr_callout); 1028 else 1029 callout_reset(&resettodr_callout, resettodr_period * hz, 1030 periodic_resettodr, NULL); 1031 done: 1032 return (0); 1033 } 1034 1035 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT | CTLFLAG_RWTUN | 1036 CTLFLAG_MPSAFE, &resettodr_period, 1800, sysctl_resettodr_period, "I", 1037 "Save system time to RTC with this period (in seconds)"); 1038 1039 static void 1040 start_periodic_resettodr(void *arg __unused) 1041 { 1042 1043 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL, 1044 SHUTDOWN_PRI_FIRST); 1045 callout_init(&resettodr_callout, 1); 1046 if (resettodr_period == 0) 1047 return; 1048 callout_reset(&resettodr_callout, resettodr_period * hz, 1049 periodic_resettodr, NULL); 1050 } 1051 1052 SYSINIT(periodic_resettodr, SI_SUB_LAST, SI_ORDER_MIDDLE, 1053 start_periodic_resettodr, NULL);
Cache object: 6163f2ece9788b69bdade08bcc00ef93
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