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/clock.h> 42 #include <sys/eventhandler.h> 43 #include <sys/kernel.h> 44 #include <sys/priv.h> 45 #include <sys/proc.h> 46 #include <sys/lock.h> 47 #include <sys/mutex.h> 48 #include <sys/time.h> 49 #include <sys/timex.h> 50 #include <sys/timetc.h> 51 #include <sys/timepps.h> 52 #include <sys/syscallsubr.h> 53 #include <sys/sysctl.h> 54 55 /* 56 * Single-precision macros for 64-bit machines 57 */ 58 typedef int64_t l_fp; 59 #define L_ADD(v, u) ((v) += (u)) 60 #define L_SUB(v, u) ((v) -= (u)) 61 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32) 62 #define L_NEG(v) ((v) = -(v)) 63 #define L_RSHIFT(v, n) \ 64 do { \ 65 if ((v) < 0) \ 66 (v) = -(-(v) >> (n)); \ 67 else \ 68 (v) = (v) >> (n); \ 69 } while (0) 70 #define L_MPY(v, a) ((v) *= (a)) 71 #define L_CLR(v) ((v) = 0) 72 #define L_ISNEG(v) ((v) < 0) 73 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32) 74 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 75 76 /* 77 * Generic NTP kernel interface 78 * 79 * These routines constitute the Network Time Protocol (NTP) interfaces 80 * for user and daemon application programs. The ntp_gettime() routine 81 * provides the time, maximum error (synch distance) and estimated error 82 * (dispersion) to client user application programs. The ntp_adjtime() 83 * routine is used by the NTP daemon to adjust the system clock to an 84 * externally derived time. The time offset and related variables set by 85 * this routine are used by other routines in this module to adjust the 86 * phase and frequency of the clock discipline loop which controls the 87 * system clock. 88 * 89 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 90 * defined), the time at each tick interrupt is derived directly from 91 * the kernel time variable. When the kernel time is reckoned in 92 * microseconds, (NTP_NANO undefined), the time is derived from the 93 * kernel time variable together with a variable representing the 94 * leftover nanoseconds at the last tick interrupt. In either case, the 95 * current nanosecond time is reckoned from these values plus an 96 * interpolated value derived by the clock routines in another 97 * architecture-specific module. The interpolation can use either a 98 * dedicated counter or a processor cycle counter (PCC) implemented in 99 * some architectures. 100 * 101 * Note that all routines must run at priority splclock or higher. 102 */ 103 /* 104 * Phase/frequency-lock loop (PLL/FLL) definitions 105 * 106 * The nanosecond clock discipline uses two variable types, time 107 * variables and frequency variables. Both types are represented as 64- 108 * bit fixed-point quantities with the decimal point between two 32-bit 109 * halves. On a 32-bit machine, each half is represented as a single 110 * word and mathematical operations are done using multiple-precision 111 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 112 * used. 113 * 114 * A time variable is a signed 64-bit fixed-point number in ns and 115 * fraction. It represents the remaining time offset to be amortized 116 * over succeeding tick interrupts. The maximum time offset is about 117 * 0.5 s and the resolution is about 2.3e-10 ns. 118 * 119 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 120 * 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 1 121 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 * |s s s| ns | 123 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 124 * | fraction | 125 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 126 * 127 * A frequency variable is a signed 64-bit fixed-point number in ns/s 128 * and fraction. It represents the ns and fraction to be added to the 129 * kernel time variable at each second. The maximum frequency offset is 130 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 131 * 132 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 133 * 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 1 134 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 * |s s s s s s s s s s s s s| ns/s | 136 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 137 * | fraction | 138 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 */ 140 /* 141 * The following variables establish the state of the PLL/FLL and the 142 * residual time and frequency offset of the local clock. 143 */ 144 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 145 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 146 147 static int time_state = TIME_OK; /* clock state */ 148 static int time_status = STA_UNSYNC; /* clock status bits */ 149 static long time_tai; /* TAI offset (s) */ 150 static long time_monitor; /* last time offset scaled (ns) */ 151 static long time_constant; /* poll interval (shift) (s) */ 152 static long time_precision = 1; /* clock precision (ns) */ 153 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 154 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 155 static long time_reftime; /* time at last adjustment (s) */ 156 static l_fp time_offset; /* time offset (ns) */ 157 static l_fp time_freq; /* frequency offset (ns/s) */ 158 static l_fp time_adj; /* tick adjust (ns/s) */ 159 160 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 161 162 #ifdef PPS_SYNC 163 /* 164 * The following variables are used when a pulse-per-second (PPS) signal 165 * is available and connected via a modem control lead. They establish 166 * the engineering parameters of the clock discipline loop when 167 * controlled by the PPS signal. 168 */ 169 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 170 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 171 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 172 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 173 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 174 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 175 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 176 177 static struct timespec pps_tf[3]; /* phase median filter */ 178 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 179 static long pps_fcount; /* frequency accumulator */ 180 static long pps_jitter; /* nominal jitter (ns) */ 181 static long pps_stabil; /* nominal stability (scaled ns/s) */ 182 static long pps_lastsec; /* time at last calibration (s) */ 183 static int pps_valid; /* signal watchdog counter */ 184 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 185 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 186 static int pps_intcnt; /* wander counter */ 187 188 /* 189 * PPS signal quality monitors 190 */ 191 static long pps_calcnt; /* calibration intervals */ 192 static long pps_jitcnt; /* jitter limit exceeded */ 193 static long pps_stbcnt; /* stability limit exceeded */ 194 static long pps_errcnt; /* calibration errors */ 195 #endif /* PPS_SYNC */ 196 /* 197 * End of phase/frequency-lock loop (PLL/FLL) definitions 198 */ 199 200 static void ntp_init(void); 201 static void hardupdate(long offset); 202 static void ntp_gettime1(struct ntptimeval *ntvp); 203 static int ntp_is_time_error(void); 204 205 static int 206 ntp_is_time_error(void) 207 { 208 /* 209 * Status word error decode. If any of these conditions occur, 210 * an error is returned, instead of the status word. Most 211 * applications will care only about the fact the system clock 212 * may not be trusted, not about the details. 213 * 214 * Hardware or software error 215 */ 216 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 217 218 /* 219 * PPS signal lost when either time or frequency synchronization 220 * requested 221 */ 222 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 223 !(time_status & STA_PPSSIGNAL)) || 224 225 /* 226 * PPS jitter exceeded when time synchronization requested 227 */ 228 (time_status & STA_PPSTIME && 229 time_status & STA_PPSJITTER) || 230 231 /* 232 * PPS wander exceeded or calibration error when frequency 233 * synchronization requested 234 */ 235 (time_status & STA_PPSFREQ && 236 time_status & (STA_PPSWANDER | STA_PPSERROR))) 237 return (1); 238 239 return (0); 240 } 241 242 static void 243 ntp_gettime1(struct ntptimeval *ntvp) 244 { 245 struct timespec atv; /* nanosecond time */ 246 247 GIANT_REQUIRED; 248 249 nanotime(&atv); 250 ntvp->time.tv_sec = atv.tv_sec; 251 ntvp->time.tv_nsec = atv.tv_nsec; 252 ntvp->maxerror = time_maxerror; 253 ntvp->esterror = time_esterror; 254 ntvp->tai = time_tai; 255 ntvp->time_state = time_state; 256 257 if (ntp_is_time_error()) 258 ntvp->time_state = TIME_ERROR; 259 } 260 261 /* 262 * ntp_gettime() - NTP user application interface 263 * 264 * See the timex.h header file for synopsis and API description. Note that 265 * the TAI offset is returned in the ntvtimeval.tai structure member. 266 */ 267 #ifndef _SYS_SYSPROTO_H_ 268 struct ntp_gettime_args { 269 struct ntptimeval *ntvp; 270 }; 271 #endif 272 /* ARGSUSED */ 273 int 274 ntp_gettime(struct thread *td, struct ntp_gettime_args *uap) 275 { 276 struct ntptimeval ntv; 277 278 mtx_lock(&Giant); 279 ntp_gettime1(&ntv); 280 mtx_unlock(&Giant); 281 282 td->td_retval[0] = ntv.time_state; 283 return (copyout(&ntv, uap->ntvp, sizeof(ntv))); 284 } 285 286 static int 287 ntp_sysctl(SYSCTL_HANDLER_ARGS) 288 { 289 struct ntptimeval ntv; /* temporary structure */ 290 291 ntp_gettime1(&ntv); 292 293 return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req)); 294 } 295 296 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 297 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 298 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 299 300 #ifdef PPS_SYNC 301 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 302 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 303 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 304 305 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 306 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 307 #endif 308 309 /* 310 * ntp_adjtime() - NTP daemon application interface 311 * 312 * See the timex.h header file for synopsis and API description. Note that 313 * the timex.constant structure member has a dual purpose to set the time 314 * constant and to set the TAI offset. 315 */ 316 #ifndef _SYS_SYSPROTO_H_ 317 struct ntp_adjtime_args { 318 struct timex *tp; 319 }; 320 #endif 321 322 int 323 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 324 { 325 struct timex ntv; /* temporary structure */ 326 long freq; /* frequency ns/s) */ 327 int modes; /* mode bits from structure */ 328 int s; /* caller priority */ 329 int error; 330 331 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 332 if (error) 333 return(error); 334 335 /* 336 * Update selected clock variables - only the superuser can 337 * change anything. Note that there is no error checking here on 338 * the assumption the superuser should know what it is doing. 339 * Note that either the time constant or TAI offset are loaded 340 * from the ntv.constant member, depending on the mode bits. If 341 * the STA_PLL bit in the status word is cleared, the state and 342 * status words are reset to the initial values at boot. 343 */ 344 mtx_lock(&Giant); 345 modes = ntv.modes; 346 if (modes) 347 error = priv_check(td, PRIV_NTP_ADJTIME); 348 if (error) 349 goto done2; 350 s = splclock(); 351 if (modes & MOD_MAXERROR) 352 time_maxerror = ntv.maxerror; 353 if (modes & MOD_ESTERROR) 354 time_esterror = ntv.esterror; 355 if (modes & MOD_STATUS) { 356 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 357 time_state = TIME_OK; 358 time_status = STA_UNSYNC; 359 #ifdef PPS_SYNC 360 pps_shift = PPS_FAVG; 361 #endif /* PPS_SYNC */ 362 } 363 time_status &= STA_RONLY; 364 time_status |= ntv.status & ~STA_RONLY; 365 } 366 if (modes & MOD_TIMECONST) { 367 if (ntv.constant < 0) 368 time_constant = 0; 369 else if (ntv.constant > MAXTC) 370 time_constant = MAXTC; 371 else 372 time_constant = ntv.constant; 373 } 374 if (modes & MOD_TAI) { 375 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 376 time_tai = ntv.constant; 377 } 378 #ifdef PPS_SYNC 379 if (modes & MOD_PPSMAX) { 380 if (ntv.shift < PPS_FAVG) 381 pps_shiftmax = PPS_FAVG; 382 else if (ntv.shift > PPS_FAVGMAX) 383 pps_shiftmax = PPS_FAVGMAX; 384 else 385 pps_shiftmax = ntv.shift; 386 } 387 #endif /* PPS_SYNC */ 388 if (modes & MOD_NANO) 389 time_status |= STA_NANO; 390 if (modes & MOD_MICRO) 391 time_status &= ~STA_NANO; 392 if (modes & MOD_CLKB) 393 time_status |= STA_CLK; 394 if (modes & MOD_CLKA) 395 time_status &= ~STA_CLK; 396 if (modes & MOD_FREQUENCY) { 397 freq = (ntv.freq * 1000LL) >> 16; 398 if (freq > MAXFREQ) 399 L_LINT(time_freq, MAXFREQ); 400 else if (freq < -MAXFREQ) 401 L_LINT(time_freq, -MAXFREQ); 402 else { 403 /* 404 * ntv.freq is [PPM * 2^16] = [us/s * 2^16] 405 * time_freq is [ns/s * 2^32] 406 */ 407 time_freq = ntv.freq * 1000LL * 65536LL; 408 } 409 #ifdef PPS_SYNC 410 pps_freq = time_freq; 411 #endif /* PPS_SYNC */ 412 } 413 if (modes & MOD_OFFSET) { 414 if (time_status & STA_NANO) 415 hardupdate(ntv.offset); 416 else 417 hardupdate(ntv.offset * 1000); 418 } 419 420 /* 421 * Retrieve all clock variables. Note that the TAI offset is 422 * returned only by ntp_gettime(); 423 */ 424 if (time_status & STA_NANO) 425 ntv.offset = L_GINT(time_offset); 426 else 427 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 428 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 429 ntv.maxerror = time_maxerror; 430 ntv.esterror = time_esterror; 431 ntv.status = time_status; 432 ntv.constant = time_constant; 433 if (time_status & STA_NANO) 434 ntv.precision = time_precision; 435 else 436 ntv.precision = time_precision / 1000; 437 ntv.tolerance = MAXFREQ * SCALE_PPM; 438 #ifdef PPS_SYNC 439 ntv.shift = pps_shift; 440 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 441 if (time_status & STA_NANO) 442 ntv.jitter = pps_jitter; 443 else 444 ntv.jitter = pps_jitter / 1000; 445 ntv.stabil = pps_stabil; 446 ntv.calcnt = pps_calcnt; 447 ntv.errcnt = pps_errcnt; 448 ntv.jitcnt = pps_jitcnt; 449 ntv.stbcnt = pps_stbcnt; 450 #endif /* PPS_SYNC */ 451 splx(s); 452 453 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 454 if (error) 455 goto done2; 456 457 if (ntp_is_time_error()) 458 td->td_retval[0] = TIME_ERROR; 459 else 460 td->td_retval[0] = time_state; 461 462 done2: 463 mtx_unlock(&Giant); 464 return (error); 465 } 466 467 /* 468 * second_overflow() - called after ntp_tick_adjust() 469 * 470 * This routine is ordinarily called immediately following the above 471 * routine ntp_tick_adjust(). While these two routines are normally 472 * combined, they are separated here only for the purposes of 473 * simulation. 474 */ 475 void 476 ntp_update_second(int64_t *adjustment, time_t *newsec) 477 { 478 int tickrate; 479 l_fp ftemp; /* 32/64-bit temporary */ 480 481 /* 482 * On rollover of the second both the nanosecond and microsecond 483 * clocks are updated and the state machine cranked as 484 * necessary. The phase adjustment to be used for the next 485 * second is calculated and the maximum error is increased by 486 * the tolerance. 487 */ 488 time_maxerror += MAXFREQ / 1000; 489 490 /* 491 * Leap second processing. If in leap-insert state at 492 * the end of the day, the system clock is set back one 493 * second; if in leap-delete state, the system clock is 494 * set ahead one second. The nano_time() routine or 495 * external clock driver will insure that reported time 496 * is always monotonic. 497 */ 498 switch (time_state) { 499 500 /* 501 * No warning. 502 */ 503 case TIME_OK: 504 if (time_status & STA_INS) 505 time_state = TIME_INS; 506 else if (time_status & STA_DEL) 507 time_state = TIME_DEL; 508 break; 509 510 /* 511 * Insert second 23:59:60 following second 512 * 23:59:59. 513 */ 514 case TIME_INS: 515 if (!(time_status & STA_INS)) 516 time_state = TIME_OK; 517 else if ((*newsec) % 86400 == 0) { 518 (*newsec)--; 519 time_state = TIME_OOP; 520 time_tai++; 521 } 522 break; 523 524 /* 525 * Delete second 23:59:59. 526 */ 527 case TIME_DEL: 528 if (!(time_status & STA_DEL)) 529 time_state = TIME_OK; 530 else if (((*newsec) + 1) % 86400 == 0) { 531 (*newsec)++; 532 time_tai--; 533 time_state = TIME_WAIT; 534 } 535 break; 536 537 /* 538 * Insert second in progress. 539 */ 540 case TIME_OOP: 541 time_state = TIME_WAIT; 542 break; 543 544 /* 545 * Wait for status bits to clear. 546 */ 547 case TIME_WAIT: 548 if (!(time_status & (STA_INS | STA_DEL))) 549 time_state = TIME_OK; 550 } 551 552 /* 553 * Compute the total time adjustment for the next second 554 * in ns. The offset is reduced by a factor depending on 555 * whether the PPS signal is operating. Note that the 556 * value is in effect scaled by the clock frequency, 557 * since the adjustment is added at each tick interrupt. 558 */ 559 ftemp = time_offset; 560 #ifdef PPS_SYNC 561 /* XXX even if PPS signal dies we should finish adjustment ? */ 562 if (time_status & STA_PPSTIME && time_status & 563 STA_PPSSIGNAL) 564 L_RSHIFT(ftemp, pps_shift); 565 else 566 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 567 #else 568 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 569 #endif /* PPS_SYNC */ 570 time_adj = ftemp; 571 L_SUB(time_offset, ftemp); 572 L_ADD(time_adj, time_freq); 573 574 /* 575 * Apply any correction from adjtime(2). If more than one second 576 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM) 577 * until the last second is slewed the final < 500 usecs. 578 */ 579 if (time_adjtime != 0) { 580 if (time_adjtime > 1000000) 581 tickrate = 5000; 582 else if (time_adjtime < -1000000) 583 tickrate = -5000; 584 else if (time_adjtime > 500) 585 tickrate = 500; 586 else if (time_adjtime < -500) 587 tickrate = -500; 588 else 589 tickrate = time_adjtime; 590 time_adjtime -= tickrate; 591 L_LINT(ftemp, tickrate * 1000); 592 L_ADD(time_adj, ftemp); 593 } 594 *adjustment = time_adj; 595 596 #ifdef PPS_SYNC 597 if (pps_valid > 0) 598 pps_valid--; 599 else 600 time_status &= ~STA_PPSSIGNAL; 601 #endif /* PPS_SYNC */ 602 } 603 604 /* 605 * ntp_init() - initialize variables and structures 606 * 607 * This routine must be called after the kernel variables hz and tick 608 * are set or changed and before the next tick interrupt. In this 609 * particular implementation, these values are assumed set elsewhere in 610 * the kernel. The design allows the clock frequency and tick interval 611 * to be changed while the system is running. So, this routine should 612 * probably be integrated with the code that does that. 613 */ 614 static void 615 ntp_init() 616 { 617 618 /* 619 * The following variables are initialized only at startup. Only 620 * those structures not cleared by the compiler need to be 621 * initialized, and these only in the simulator. In the actual 622 * kernel, any nonzero values here will quickly evaporate. 623 */ 624 L_CLR(time_offset); 625 L_CLR(time_freq); 626 #ifdef PPS_SYNC 627 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 628 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 629 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 630 pps_fcount = 0; 631 L_CLR(pps_freq); 632 #endif /* PPS_SYNC */ 633 } 634 635 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL); 636 637 /* 638 * hardupdate() - local clock update 639 * 640 * This routine is called by ntp_adjtime() to update the local clock 641 * phase and frequency. The implementation is of an adaptive-parameter, 642 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 643 * time and frequency offset estimates for each call. If the kernel PPS 644 * discipline code is configured (PPS_SYNC), the PPS signal itself 645 * determines the new time offset, instead of the calling argument. 646 * Presumably, calls to ntp_adjtime() occur only when the caller 647 * believes the local clock is valid within some bound (+-128 ms with 648 * NTP). If the caller's time is far different than the PPS time, an 649 * argument will ensue, and it's not clear who will lose. 650 * 651 * For uncompensated quartz crystal oscillators and nominal update 652 * intervals less than 256 s, operation should be in phase-lock mode, 653 * where the loop is disciplined to phase. For update intervals greater 654 * than 1024 s, operation should be in frequency-lock mode, where the 655 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 656 * is selected by the STA_MODE status bit. 657 */ 658 static void 659 hardupdate(offset) 660 long offset; /* clock offset (ns) */ 661 { 662 long mtemp; 663 l_fp ftemp; 664 665 /* 666 * Select how the phase is to be controlled and from which 667 * source. If the PPS signal is present and enabled to 668 * discipline the time, the PPS offset is used; otherwise, the 669 * argument offset is used. 670 */ 671 if (!(time_status & STA_PLL)) 672 return; 673 if (!(time_status & STA_PPSTIME && time_status & 674 STA_PPSSIGNAL)) { 675 if (offset > MAXPHASE) 676 time_monitor = MAXPHASE; 677 else if (offset < -MAXPHASE) 678 time_monitor = -MAXPHASE; 679 else 680 time_monitor = offset; 681 L_LINT(time_offset, time_monitor); 682 } 683 684 /* 685 * Select how the frequency is to be controlled and in which 686 * mode (PLL or FLL). If the PPS signal is present and enabled 687 * to discipline the frequency, the PPS frequency is used; 688 * otherwise, the argument offset is used to compute it. 689 */ 690 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 691 time_reftime = time_second; 692 return; 693 } 694 if (time_status & STA_FREQHOLD || time_reftime == 0) 695 time_reftime = time_second; 696 mtemp = time_second - time_reftime; 697 L_LINT(ftemp, time_monitor); 698 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 699 L_MPY(ftemp, mtemp); 700 L_ADD(time_freq, ftemp); 701 time_status &= ~STA_MODE; 702 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 703 MAXSEC)) { 704 L_LINT(ftemp, (time_monitor << 4) / mtemp); 705 L_RSHIFT(ftemp, SHIFT_FLL + 4); 706 L_ADD(time_freq, ftemp); 707 time_status |= STA_MODE; 708 } 709 time_reftime = time_second; 710 if (L_GINT(time_freq) > MAXFREQ) 711 L_LINT(time_freq, MAXFREQ); 712 else if (L_GINT(time_freq) < -MAXFREQ) 713 L_LINT(time_freq, -MAXFREQ); 714 } 715 716 #ifdef PPS_SYNC 717 /* 718 * hardpps() - discipline CPU clock oscillator to external PPS signal 719 * 720 * This routine is called at each PPS interrupt in order to discipline 721 * the CPU clock oscillator to the PPS signal. There are two independent 722 * first-order feedback loops, one for the phase, the other for the 723 * frequency. The phase loop measures and grooms the PPS phase offset 724 * and leaves it in a handy spot for the seconds overflow routine. The 725 * frequency loop averages successive PPS phase differences and 726 * calculates the PPS frequency offset, which is also processed by the 727 * seconds overflow routine. The code requires the caller to capture the 728 * time and architecture-dependent hardware counter values in 729 * nanoseconds at the on-time PPS signal transition. 730 * 731 * Note that, on some Unix systems this routine runs at an interrupt 732 * priority level higher than the timer interrupt routine hardclock(). 733 * Therefore, the variables used are distinct from the hardclock() 734 * variables, except for the actual time and frequency variables, which 735 * are determined by this routine and updated atomically. 736 */ 737 void 738 hardpps(tsp, nsec) 739 struct timespec *tsp; /* time at PPS */ 740 long nsec; /* hardware counter at PPS */ 741 { 742 long u_sec, u_nsec, v_nsec; /* temps */ 743 l_fp ftemp; 744 745 /* 746 * The signal is first processed by a range gate and frequency 747 * discriminator. The range gate rejects noise spikes outside 748 * the range +-500 us. The frequency discriminator rejects input 749 * signals with apparent frequency outside the range 1 +-500 750 * PPM. If two hits occur in the same second, we ignore the 751 * later hit; if not and a hit occurs outside the range gate, 752 * keep the later hit for later comparison, but do not process 753 * it. 754 */ 755 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 756 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 757 pps_valid = PPS_VALID; 758 u_sec = tsp->tv_sec; 759 u_nsec = tsp->tv_nsec; 760 if (u_nsec >= (NANOSECOND >> 1)) { 761 u_nsec -= NANOSECOND; 762 u_sec++; 763 } 764 v_nsec = u_nsec - pps_tf[0].tv_nsec; 765 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 766 MAXFREQ) 767 return; 768 pps_tf[2] = pps_tf[1]; 769 pps_tf[1] = pps_tf[0]; 770 pps_tf[0].tv_sec = u_sec; 771 pps_tf[0].tv_nsec = u_nsec; 772 773 /* 774 * Compute the difference between the current and previous 775 * counter values. If the difference exceeds 0.5 s, assume it 776 * has wrapped around, so correct 1.0 s. If the result exceeds 777 * the tick interval, the sample point has crossed a tick 778 * boundary during the last second, so correct the tick. Very 779 * intricate. 780 */ 781 u_nsec = nsec; 782 if (u_nsec > (NANOSECOND >> 1)) 783 u_nsec -= NANOSECOND; 784 else if (u_nsec < -(NANOSECOND >> 1)) 785 u_nsec += NANOSECOND; 786 pps_fcount += u_nsec; 787 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 788 return; 789 time_status &= ~STA_PPSJITTER; 790 791 /* 792 * A three-stage median filter is used to help denoise the PPS 793 * time. The median sample becomes the time offset estimate; the 794 * difference between the other two samples becomes the time 795 * dispersion (jitter) estimate. 796 */ 797 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 798 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 799 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 800 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 801 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 802 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 803 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 804 } else { 805 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 806 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 807 } 808 } else { 809 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 810 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 811 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 812 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 813 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 814 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 815 } else { 816 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 817 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 818 } 819 } 820 821 /* 822 * Nominal jitter is due to PPS signal noise and interrupt 823 * latency. If it exceeds the popcorn threshold, the sample is 824 * discarded. otherwise, if so enabled, the time offset is 825 * updated. We can tolerate a modest loss of data here without 826 * much degrading time accuracy. 827 */ 828 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 829 time_status |= STA_PPSJITTER; 830 pps_jitcnt++; 831 } else if (time_status & STA_PPSTIME) { 832 time_monitor = -v_nsec; 833 L_LINT(time_offset, time_monitor); 834 } 835 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 836 u_sec = pps_tf[0].tv_sec - pps_lastsec; 837 if (u_sec < (1 << pps_shift)) 838 return; 839 840 /* 841 * At the end of the calibration interval the difference between 842 * the first and last counter values becomes the scaled 843 * frequency. It will later be divided by the length of the 844 * interval to determine the frequency update. If the frequency 845 * exceeds a sanity threshold, or if the actual calibration 846 * interval is not equal to the expected length, the data are 847 * discarded. We can tolerate a modest loss of data here without 848 * much degrading frequency accuracy. 849 */ 850 pps_calcnt++; 851 v_nsec = -pps_fcount; 852 pps_lastsec = pps_tf[0].tv_sec; 853 pps_fcount = 0; 854 u_nsec = MAXFREQ << pps_shift; 855 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 856 pps_shift)) { 857 time_status |= STA_PPSERROR; 858 pps_errcnt++; 859 return; 860 } 861 862 /* 863 * Here the raw frequency offset and wander (stability) is 864 * calculated. If the wander is less than the wander threshold 865 * for four consecutive averaging intervals, the interval is 866 * doubled; if it is greater than the threshold for four 867 * consecutive intervals, the interval is halved. The scaled 868 * frequency offset is converted to frequency offset. The 869 * stability metric is calculated as the average of recent 870 * frequency changes, but is used only for performance 871 * monitoring. 872 */ 873 L_LINT(ftemp, v_nsec); 874 L_RSHIFT(ftemp, pps_shift); 875 L_SUB(ftemp, pps_freq); 876 u_nsec = L_GINT(ftemp); 877 if (u_nsec > PPS_MAXWANDER) { 878 L_LINT(ftemp, PPS_MAXWANDER); 879 pps_intcnt--; 880 time_status |= STA_PPSWANDER; 881 pps_stbcnt++; 882 } else if (u_nsec < -PPS_MAXWANDER) { 883 L_LINT(ftemp, -PPS_MAXWANDER); 884 pps_intcnt--; 885 time_status |= STA_PPSWANDER; 886 pps_stbcnt++; 887 } else { 888 pps_intcnt++; 889 } 890 if (pps_intcnt >= 4) { 891 pps_intcnt = 4; 892 if (pps_shift < pps_shiftmax) { 893 pps_shift++; 894 pps_intcnt = 0; 895 } 896 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 897 pps_intcnt = -4; 898 if (pps_shift > PPS_FAVG) { 899 pps_shift--; 900 pps_intcnt = 0; 901 } 902 } 903 if (u_nsec < 0) 904 u_nsec = -u_nsec; 905 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 906 907 /* 908 * The PPS frequency is recalculated and clamped to the maximum 909 * MAXFREQ. If enabled, the system clock frequency is updated as 910 * well. 911 */ 912 L_ADD(pps_freq, ftemp); 913 u_nsec = L_GINT(pps_freq); 914 if (u_nsec > MAXFREQ) 915 L_LINT(pps_freq, MAXFREQ); 916 else if (u_nsec < -MAXFREQ) 917 L_LINT(pps_freq, -MAXFREQ); 918 if (time_status & STA_PPSFREQ) 919 time_freq = pps_freq; 920 } 921 #endif /* PPS_SYNC */ 922 923 #ifndef _SYS_SYSPROTO_H_ 924 struct adjtime_args { 925 struct timeval *delta; 926 struct timeval *olddelta; 927 }; 928 #endif 929 /* ARGSUSED */ 930 int 931 adjtime(struct thread *td, struct adjtime_args *uap) 932 { 933 struct timeval delta, olddelta, *deltap; 934 int error; 935 936 if (uap->delta) { 937 error = copyin(uap->delta, &delta, sizeof(delta)); 938 if (error) 939 return (error); 940 deltap = δ 941 } else 942 deltap = NULL; 943 error = kern_adjtime(td, deltap, &olddelta); 944 if (uap->olddelta && error == 0) 945 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta)); 946 return (error); 947 } 948 949 int 950 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta) 951 { 952 struct timeval atv; 953 int error; 954 955 mtx_lock(&Giant); 956 if (olddelta) { 957 atv.tv_sec = time_adjtime / 1000000; 958 atv.tv_usec = time_adjtime % 1000000; 959 if (atv.tv_usec < 0) { 960 atv.tv_usec += 1000000; 961 atv.tv_sec--; 962 } 963 *olddelta = atv; 964 } 965 if (delta) { 966 if ((error = priv_check(td, PRIV_ADJTIME))) { 967 mtx_unlock(&Giant); 968 return (error); 969 } 970 time_adjtime = (int64_t)delta->tv_sec * 1000000 + 971 delta->tv_usec; 972 } 973 mtx_unlock(&Giant); 974 return (0); 975 } 976 977 static struct callout resettodr_callout; 978 static int resettodr_period = 1800; 979 980 static void 981 periodic_resettodr(void *arg __unused) 982 { 983 984 if (!ntp_is_time_error()) { 985 mtx_lock(&Giant); 986 resettodr(); 987 mtx_unlock(&Giant); 988 } 989 if (resettodr_period > 0) 990 callout_reset(&resettodr_callout, resettodr_period * hz, 991 periodic_resettodr, NULL); 992 } 993 994 static void 995 shutdown_resettodr(void *arg __unused, int howto __unused) 996 { 997 998 callout_drain(&resettodr_callout); 999 if (resettodr_period > 0 && !ntp_is_time_error()) { 1000 mtx_lock(&Giant); 1001 resettodr(); 1002 mtx_unlock(&Giant); 1003 } 1004 } 1005 1006 static int 1007 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS) 1008 { 1009 int error; 1010 1011 error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req); 1012 if (error || !req->newptr) 1013 return (error); 1014 if (resettodr_period == 0) 1015 callout_stop(&resettodr_callout); 1016 else 1017 callout_reset(&resettodr_callout, resettodr_period * hz, 1018 periodic_resettodr, NULL); 1019 return (0); 1020 } 1021 1022 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT|CTLFLAG_RW, 1023 &resettodr_period, 1800, sysctl_resettodr_period, "I", 1024 "Save system time to RTC with this period (in seconds)"); 1025 TUNABLE_INT("machdep.rtc_save_period", &resettodr_period); 1026 1027 static void 1028 start_periodic_resettodr(void *arg __unused) 1029 { 1030 1031 EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL, 1032 SHUTDOWN_PRI_FIRST); 1033 callout_init(&resettodr_callout, 1); 1034 if (resettodr_period == 0) 1035 return; 1036 callout_reset(&resettodr_callout, resettodr_period * hz, 1037 periodic_resettodr, NULL); 1038 } 1039 1040 SYSINIT(periodic_resettodr, SI_SUB_RUN_SCHEDULER, SI_ORDER_MIDDLE, 1041 start_periodic_resettodr, NULL);
Cache object: 40623d883d1500d9157de737d405eaf5
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