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: releng/5.4/sys/kern/kern_ntptime.c 145335 2005-04-20 19:11:07Z cvs2svn $"); 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/kernel.h> 42 #include <sys/proc.h> 43 #include <sys/lock.h> 44 #include <sys/mutex.h> 45 #include <sys/time.h> 46 #include <sys/timex.h> 47 #include <sys/timetc.h> 48 #include <sys/timepps.h> 49 #include <sys/sysctl.h> 50 51 /* 52 * Single-precision macros for 64-bit machines 53 */ 54 typedef int64_t l_fp; 55 #define L_ADD(v, u) ((v) += (u)) 56 #define L_SUB(v, u) ((v) -= (u)) 57 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32) 58 #define L_NEG(v) ((v) = -(v)) 59 #define L_RSHIFT(v, n) \ 60 do { \ 61 if ((v) < 0) \ 62 (v) = -(-(v) >> (n)); \ 63 else \ 64 (v) = (v) >> (n); \ 65 } while (0) 66 #define L_MPY(v, a) ((v) *= (a)) 67 #define L_CLR(v) ((v) = 0) 68 #define L_ISNEG(v) ((v) < 0) 69 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32) 70 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 71 72 /* 73 * Generic NTP kernel interface 74 * 75 * These routines constitute the Network Time Protocol (NTP) interfaces 76 * for user and daemon application programs. The ntp_gettime() routine 77 * provides the time, maximum error (synch distance) and estimated error 78 * (dispersion) to client user application programs. The ntp_adjtime() 79 * routine is used by the NTP daemon to adjust the system clock to an 80 * externally derived time. The time offset and related variables set by 81 * this routine are used by other routines in this module to adjust the 82 * phase and frequency of the clock discipline loop which controls the 83 * system clock. 84 * 85 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 86 * defined), the time at each tick interrupt is derived directly from 87 * the kernel time variable. When the kernel time is reckoned in 88 * microseconds, (NTP_NANO undefined), the time is derived from the 89 * kernel time variable together with a variable representing the 90 * leftover nanoseconds at the last tick interrupt. In either case, the 91 * current nanosecond time is reckoned from these values plus an 92 * interpolated value derived by the clock routines in another 93 * architecture-specific module. The interpolation can use either a 94 * dedicated counter or a processor cycle counter (PCC) implemented in 95 * some architectures. 96 * 97 * Note that all routines must run at priority splclock or higher. 98 */ 99 /* 100 * Phase/frequency-lock loop (PLL/FLL) definitions 101 * 102 * The nanosecond clock discipline uses two variable types, time 103 * variables and frequency variables. Both types are represented as 64- 104 * bit fixed-point quantities with the decimal point between two 32-bit 105 * halves. On a 32-bit machine, each half is represented as a single 106 * word and mathematical operations are done using multiple-precision 107 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 108 * used. 109 * 110 * A time variable is a signed 64-bit fixed-point number in ns and 111 * fraction. It represents the remaining time offset to be amortized 112 * over succeeding tick interrupts. The maximum time offset is about 113 * 0.5 s and the resolution is about 2.3e-10 ns. 114 * 115 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 116 * 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 1 117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 * |s s s| ns | 119 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 * | fraction | 121 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 * 123 * A frequency variable is a signed 64-bit fixed-point number in ns/s 124 * and fraction. It represents the ns and fraction to be added to the 125 * kernel time variable at each second. The maximum frequency offset is 126 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 127 * 128 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 129 * 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 1 130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 * |s s s s s s s s s s s s s| ns/s | 132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 133 * | fraction | 134 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 */ 136 /* 137 * The following variables establish the state of the PLL/FLL and the 138 * residual time and frequency offset of the local clock. 139 */ 140 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 141 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 142 143 static int time_state = TIME_OK; /* clock state */ 144 static int time_status = STA_UNSYNC; /* clock status bits */ 145 static long time_tai; /* TAI offset (s) */ 146 static long time_monitor; /* last time offset scaled (ns) */ 147 static long time_constant; /* poll interval (shift) (s) */ 148 static long time_precision = 1; /* clock precision (ns) */ 149 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 150 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 151 static long time_reftime; /* time at last adjustment (s) */ 152 static l_fp time_offset; /* time offset (ns) */ 153 static l_fp time_freq; /* frequency offset (ns/s) */ 154 static l_fp time_adj; /* tick adjust (ns/s) */ 155 156 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 157 158 #ifdef PPS_SYNC 159 /* 160 * The following variables are used when a pulse-per-second (PPS) signal 161 * is available and connected via a modem control lead. They establish 162 * the engineering parameters of the clock discipline loop when 163 * controlled by the PPS signal. 164 */ 165 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 166 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 167 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 168 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 169 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 170 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 171 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 172 173 static struct timespec pps_tf[3]; /* phase median filter */ 174 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 175 static long pps_fcount; /* frequency accumulator */ 176 static long pps_jitter; /* nominal jitter (ns) */ 177 static long pps_stabil; /* nominal stability (scaled ns/s) */ 178 static long pps_lastsec; /* time at last calibration (s) */ 179 static int pps_valid; /* signal watchdog counter */ 180 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 181 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 182 static int pps_intcnt; /* wander counter */ 183 184 /* 185 * PPS signal quality monitors 186 */ 187 static long pps_calcnt; /* calibration intervals */ 188 static long pps_jitcnt; /* jitter limit exceeded */ 189 static long pps_stbcnt; /* stability limit exceeded */ 190 static long pps_errcnt; /* calibration errors */ 191 #endif /* PPS_SYNC */ 192 /* 193 * End of phase/frequency-lock loop (PLL/FLL) definitions 194 */ 195 196 static void ntp_init(void); 197 static void hardupdate(long offset); 198 199 /* 200 * ntp_gettime() - NTP user application interface 201 * 202 * See the timex.h header file for synopsis and API description. Note 203 * that the TAI offset is returned in the ntvtimeval.tai structure 204 * member. 205 */ 206 static int 207 ntp_sysctl(SYSCTL_HANDLER_ARGS) 208 { 209 struct ntptimeval ntv; /* temporary structure */ 210 struct timespec atv; /* nanosecond time */ 211 212 nanotime(&atv); 213 ntv.time.tv_sec = atv.tv_sec; 214 ntv.time.tv_nsec = atv.tv_nsec; 215 ntv.maxerror = time_maxerror; 216 ntv.esterror = time_esterror; 217 ntv.tai = time_tai; 218 ntv.time_state = time_state; 219 220 /* 221 * Status word error decode. If any of these conditions occur, 222 * an error is returned, instead of the status word. Most 223 * applications will care only about the fact the system clock 224 * may not be trusted, not about the details. 225 * 226 * Hardware or software error 227 */ 228 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 229 230 /* 231 * PPS signal lost when either time or frequency synchronization 232 * requested 233 */ 234 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 235 !(time_status & STA_PPSSIGNAL)) || 236 237 /* 238 * PPS jitter exceeded when time synchronization requested 239 */ 240 (time_status & STA_PPSTIME && 241 time_status & STA_PPSJITTER) || 242 243 /* 244 * PPS wander exceeded or calibration error when frequency 245 * synchronization requested 246 */ 247 (time_status & STA_PPSFREQ && 248 time_status & (STA_PPSWANDER | STA_PPSERROR))) 249 ntv.time_state = TIME_ERROR; 250 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 251 } 252 253 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 254 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 255 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 256 257 #ifdef PPS_SYNC 258 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 259 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 260 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 261 262 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 263 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 264 #endif 265 /* 266 * ntp_adjtime() - NTP daemon application interface 267 * 268 * See the timex.h header file for synopsis and API description. Note 269 * that the timex.constant structure member has a dual purpose to set 270 * the time constant and to set the TAI offset. 271 */ 272 #ifndef _SYS_SYSPROTO_H_ 273 struct ntp_adjtime_args { 274 struct timex *tp; 275 }; 276 #endif 277 278 /* 279 * MPSAFE 280 */ 281 int 282 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 283 { 284 struct timex ntv; /* temporary structure */ 285 long freq; /* frequency ns/s) */ 286 int modes; /* mode bits from structure */ 287 int s; /* caller priority */ 288 int error; 289 290 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 291 if (error) 292 return(error); 293 294 /* 295 * Update selected clock variables - only the superuser can 296 * change anything. Note that there is no error checking here on 297 * the assumption the superuser should know what it is doing. 298 * Note that either the time constant or TAI offset are loaded 299 * from the ntv.constant member, depending on the mode bits. If 300 * the STA_PLL bit in the status word is cleared, the state and 301 * status words are reset to the initial values at boot. 302 */ 303 mtx_lock(&Giant); 304 modes = ntv.modes; 305 if (modes) 306 error = suser(td); 307 if (error) 308 goto done2; 309 s = splclock(); 310 if (modes & MOD_MAXERROR) 311 time_maxerror = ntv.maxerror; 312 if (modes & MOD_ESTERROR) 313 time_esterror = ntv.esterror; 314 if (modes & MOD_STATUS) { 315 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 316 time_state = TIME_OK; 317 time_status = STA_UNSYNC; 318 #ifdef PPS_SYNC 319 pps_shift = PPS_FAVG; 320 #endif /* PPS_SYNC */ 321 } 322 time_status &= STA_RONLY; 323 time_status |= ntv.status & ~STA_RONLY; 324 } 325 if (modes & MOD_TIMECONST) { 326 if (ntv.constant < 0) 327 time_constant = 0; 328 else if (ntv.constant > MAXTC) 329 time_constant = MAXTC; 330 else 331 time_constant = ntv.constant; 332 } 333 if (modes & MOD_TAI) { 334 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 335 time_tai = ntv.constant; 336 } 337 #ifdef PPS_SYNC 338 if (modes & MOD_PPSMAX) { 339 if (ntv.shift < PPS_FAVG) 340 pps_shiftmax = PPS_FAVG; 341 else if (ntv.shift > PPS_FAVGMAX) 342 pps_shiftmax = PPS_FAVGMAX; 343 else 344 pps_shiftmax = ntv.shift; 345 } 346 #endif /* PPS_SYNC */ 347 if (modes & MOD_NANO) 348 time_status |= STA_NANO; 349 if (modes & MOD_MICRO) 350 time_status &= ~STA_NANO; 351 if (modes & MOD_CLKB) 352 time_status |= STA_CLK; 353 if (modes & MOD_CLKA) 354 time_status &= ~STA_CLK; 355 if (modes & MOD_FREQUENCY) { 356 freq = (ntv.freq * 1000LL) >> 16; 357 if (freq > MAXFREQ) 358 L_LINT(time_freq, MAXFREQ); 359 else if (freq < -MAXFREQ) 360 L_LINT(time_freq, -MAXFREQ); 361 else { 362 /* 363 * ntv.freq is [PPM * 2^16] = [us/s * 2^16] 364 * time_freq is [ns/s * 2^32] 365 */ 366 time_freq = ntv.freq * 1000LL * 65536LL; 367 } 368 #ifdef PPS_SYNC 369 pps_freq = time_freq; 370 #endif /* PPS_SYNC */ 371 } 372 if (modes & MOD_OFFSET) { 373 if (time_status & STA_NANO) 374 hardupdate(ntv.offset); 375 else 376 hardupdate(ntv.offset * 1000); 377 } 378 379 /* 380 * Retrieve all clock variables. Note that the TAI offset is 381 * returned only by ntp_gettime(); 382 */ 383 if (time_status & STA_NANO) 384 ntv.offset = L_GINT(time_offset); 385 else 386 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 387 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 388 ntv.maxerror = time_maxerror; 389 ntv.esterror = time_esterror; 390 ntv.status = time_status; 391 ntv.constant = time_constant; 392 if (time_status & STA_NANO) 393 ntv.precision = time_precision; 394 else 395 ntv.precision = time_precision / 1000; 396 ntv.tolerance = MAXFREQ * SCALE_PPM; 397 #ifdef PPS_SYNC 398 ntv.shift = pps_shift; 399 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 400 if (time_status & STA_NANO) 401 ntv.jitter = pps_jitter; 402 else 403 ntv.jitter = pps_jitter / 1000; 404 ntv.stabil = pps_stabil; 405 ntv.calcnt = pps_calcnt; 406 ntv.errcnt = pps_errcnt; 407 ntv.jitcnt = pps_jitcnt; 408 ntv.stbcnt = pps_stbcnt; 409 #endif /* PPS_SYNC */ 410 splx(s); 411 412 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 413 if (error) 414 goto done2; 415 416 /* 417 * Status word error decode. See comments in 418 * ntp_gettime() routine. 419 */ 420 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 421 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 422 !(time_status & STA_PPSSIGNAL)) || 423 (time_status & STA_PPSTIME && 424 time_status & STA_PPSJITTER) || 425 (time_status & STA_PPSFREQ && 426 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 427 td->td_retval[0] = TIME_ERROR; 428 } else { 429 td->td_retval[0] = time_state; 430 } 431 done2: 432 mtx_unlock(&Giant); 433 return (error); 434 } 435 436 /* 437 * second_overflow() - called after ntp_tick_adjust() 438 * 439 * This routine is ordinarily called immediately following the above 440 * routine ntp_tick_adjust(). While these two routines are normally 441 * combined, they are separated here only for the purposes of 442 * simulation. 443 */ 444 void 445 ntp_update_second(int64_t *adjustment, time_t *newsec) 446 { 447 int tickrate; 448 l_fp ftemp; /* 32/64-bit temporary */ 449 450 /* 451 * On rollover of the second both the nanosecond and microsecond 452 * clocks are updated and the state machine cranked as 453 * necessary. The phase adjustment to be used for the next 454 * second is calculated and the maximum error is increased by 455 * the tolerance. 456 */ 457 time_maxerror += MAXFREQ / 1000; 458 459 /* 460 * Leap second processing. If in leap-insert state at 461 * the end of the day, the system clock is set back one 462 * second; if in leap-delete state, the system clock is 463 * set ahead one second. The nano_time() routine or 464 * external clock driver will insure that reported time 465 * is always monotonic. 466 */ 467 switch (time_state) { 468 469 /* 470 * No warning. 471 */ 472 case TIME_OK: 473 if (time_status & STA_INS) 474 time_state = TIME_INS; 475 else if (time_status & STA_DEL) 476 time_state = TIME_DEL; 477 break; 478 479 /* 480 * Insert second 23:59:60 following second 481 * 23:59:59. 482 */ 483 case TIME_INS: 484 if (!(time_status & STA_INS)) 485 time_state = TIME_OK; 486 else if ((*newsec) % 86400 == 0) { 487 (*newsec)--; 488 time_state = TIME_OOP; 489 time_tai++; 490 } 491 break; 492 493 /* 494 * Delete second 23:59:59. 495 */ 496 case TIME_DEL: 497 if (!(time_status & STA_DEL)) 498 time_state = TIME_OK; 499 else if (((*newsec) + 1) % 86400 == 0) { 500 (*newsec)++; 501 time_tai--; 502 time_state = TIME_WAIT; 503 } 504 break; 505 506 /* 507 * Insert second in progress. 508 */ 509 case TIME_OOP: 510 time_state = TIME_WAIT; 511 break; 512 513 /* 514 * Wait for status bits to clear. 515 */ 516 case TIME_WAIT: 517 if (!(time_status & (STA_INS | STA_DEL))) 518 time_state = TIME_OK; 519 } 520 521 /* 522 * Compute the total time adjustment for the next second 523 * in ns. The offset is reduced by a factor depending on 524 * whether the PPS signal is operating. Note that the 525 * value is in effect scaled by the clock frequency, 526 * since the adjustment is added at each tick interrupt. 527 */ 528 ftemp = time_offset; 529 #ifdef PPS_SYNC 530 /* XXX even if PPS signal dies we should finish adjustment ? */ 531 if (time_status & STA_PPSTIME && time_status & 532 STA_PPSSIGNAL) 533 L_RSHIFT(ftemp, pps_shift); 534 else 535 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 536 #else 537 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 538 #endif /* PPS_SYNC */ 539 time_adj = ftemp; 540 L_SUB(time_offset, ftemp); 541 L_ADD(time_adj, time_freq); 542 543 /* 544 * Apply any correction from adjtime(2). If more than one second 545 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM) 546 * until the last second is slewed the final < 500 usecs. 547 */ 548 if (time_adjtime != 0) { 549 if (time_adjtime > 1000000) 550 tickrate = 5000; 551 else if (time_adjtime < -1000000) 552 tickrate = -5000; 553 else if (time_adjtime > 500) 554 tickrate = 500; 555 else if (time_adjtime < -500) 556 tickrate = -500; 557 else 558 tickrate = time_adjtime; 559 time_adjtime -= tickrate; 560 L_LINT(ftemp, tickrate * 1000); 561 L_ADD(time_adj, ftemp); 562 } 563 *adjustment = time_adj; 564 565 #ifdef PPS_SYNC 566 if (pps_valid > 0) 567 pps_valid--; 568 else 569 time_status &= ~STA_PPSSIGNAL; 570 #endif /* PPS_SYNC */ 571 } 572 573 /* 574 * ntp_init() - initialize variables and structures 575 * 576 * This routine must be called after the kernel variables hz and tick 577 * are set or changed and before the next tick interrupt. In this 578 * particular implementation, these values are assumed set elsewhere in 579 * the kernel. The design allows the clock frequency and tick interval 580 * to be changed while the system is running. So, this routine should 581 * probably be integrated with the code that does that. 582 */ 583 static void 584 ntp_init() 585 { 586 587 /* 588 * The following variables are initialized only at startup. Only 589 * those structures not cleared by the compiler need to be 590 * initialized, and these only in the simulator. In the actual 591 * kernel, any nonzero values here will quickly evaporate. 592 */ 593 L_CLR(time_offset); 594 L_CLR(time_freq); 595 #ifdef PPS_SYNC 596 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 597 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 598 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 599 pps_fcount = 0; 600 L_CLR(pps_freq); 601 #endif /* PPS_SYNC */ 602 } 603 604 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL) 605 606 /* 607 * hardupdate() - local clock update 608 * 609 * This routine is called by ntp_adjtime() to update the local clock 610 * phase and frequency. The implementation is of an adaptive-parameter, 611 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 612 * time and frequency offset estimates for each call. If the kernel PPS 613 * discipline code is configured (PPS_SYNC), the PPS signal itself 614 * determines the new time offset, instead of the calling argument. 615 * Presumably, calls to ntp_adjtime() occur only when the caller 616 * believes the local clock is valid within some bound (+-128 ms with 617 * NTP). If the caller's time is far different than the PPS time, an 618 * argument will ensue, and it's not clear who will lose. 619 * 620 * For uncompensated quartz crystal oscillators and nominal update 621 * intervals less than 256 s, operation should be in phase-lock mode, 622 * where the loop is disciplined to phase. For update intervals greater 623 * than 1024 s, operation should be in frequency-lock mode, where the 624 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 625 * is selected by the STA_MODE status bit. 626 */ 627 static void 628 hardupdate(offset) 629 long offset; /* clock offset (ns) */ 630 { 631 long mtemp; 632 l_fp ftemp; 633 634 /* 635 * Select how the phase is to be controlled and from which 636 * source. If the PPS signal is present and enabled to 637 * discipline the time, the PPS offset is used; otherwise, the 638 * argument offset is used. 639 */ 640 if (!(time_status & STA_PLL)) 641 return; 642 if (!(time_status & STA_PPSTIME && time_status & 643 STA_PPSSIGNAL)) { 644 if (offset > MAXPHASE) 645 time_monitor = MAXPHASE; 646 else if (offset < -MAXPHASE) 647 time_monitor = -MAXPHASE; 648 else 649 time_monitor = offset; 650 L_LINT(time_offset, time_monitor); 651 } 652 653 /* 654 * Select how the frequency is to be controlled and in which 655 * mode (PLL or FLL). If the PPS signal is present and enabled 656 * to discipline the frequency, the PPS frequency is used; 657 * otherwise, the argument offset is used to compute it. 658 */ 659 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 660 time_reftime = time_second; 661 return; 662 } 663 if (time_status & STA_FREQHOLD || time_reftime == 0) 664 time_reftime = time_second; 665 mtemp = time_second - time_reftime; 666 L_LINT(ftemp, time_monitor); 667 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 668 L_MPY(ftemp, mtemp); 669 L_ADD(time_freq, ftemp); 670 time_status &= ~STA_MODE; 671 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 672 MAXSEC)) { 673 L_LINT(ftemp, (time_monitor << 4) / mtemp); 674 L_RSHIFT(ftemp, SHIFT_FLL + 4); 675 L_ADD(time_freq, ftemp); 676 time_status |= STA_MODE; 677 } 678 time_reftime = time_second; 679 if (L_GINT(time_freq) > MAXFREQ) 680 L_LINT(time_freq, MAXFREQ); 681 else if (L_GINT(time_freq) < -MAXFREQ) 682 L_LINT(time_freq, -MAXFREQ); 683 } 684 685 #ifdef PPS_SYNC 686 /* 687 * hardpps() - discipline CPU clock oscillator to external PPS signal 688 * 689 * This routine is called at each PPS interrupt in order to discipline 690 * the CPU clock oscillator to the PPS signal. There are two independent 691 * first-order feedback loops, one for the phase, the other for the 692 * frequency. The phase loop measures and grooms the PPS phase offset 693 * and leaves it in a handy spot for the seconds overflow routine. The 694 * frequency loop averages successive PPS phase differences and 695 * calculates the PPS frequency offset, which is also processed by the 696 * seconds overflow routine. The code requires the caller to capture the 697 * time and architecture-dependent hardware counter values in 698 * nanoseconds at the on-time PPS signal transition. 699 * 700 * Note that, on some Unix systems this routine runs at an interrupt 701 * priority level higher than the timer interrupt routine hardclock(). 702 * Therefore, the variables used are distinct from the hardclock() 703 * variables, except for the actual time and frequency variables, which 704 * are determined by this routine and updated atomically. 705 */ 706 void 707 hardpps(tsp, nsec) 708 struct timespec *tsp; /* time at PPS */ 709 long nsec; /* hardware counter at PPS */ 710 { 711 long u_sec, u_nsec, v_nsec; /* temps */ 712 l_fp ftemp; 713 714 /* 715 * The signal is first processed by a range gate and frequency 716 * discriminator. The range gate rejects noise spikes outside 717 * the range +-500 us. The frequency discriminator rejects input 718 * signals with apparent frequency outside the range 1 +-500 719 * PPM. If two hits occur in the same second, we ignore the 720 * later hit; if not and a hit occurs outside the range gate, 721 * keep the later hit for later comparison, but do not process 722 * it. 723 */ 724 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 725 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 726 pps_valid = PPS_VALID; 727 u_sec = tsp->tv_sec; 728 u_nsec = tsp->tv_nsec; 729 if (u_nsec >= (NANOSECOND >> 1)) { 730 u_nsec -= NANOSECOND; 731 u_sec++; 732 } 733 v_nsec = u_nsec - pps_tf[0].tv_nsec; 734 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 735 MAXFREQ) 736 return; 737 pps_tf[2] = pps_tf[1]; 738 pps_tf[1] = pps_tf[0]; 739 pps_tf[0].tv_sec = u_sec; 740 pps_tf[0].tv_nsec = u_nsec; 741 742 /* 743 * Compute the difference between the current and previous 744 * counter values. If the difference exceeds 0.5 s, assume it 745 * has wrapped around, so correct 1.0 s. If the result exceeds 746 * the tick interval, the sample point has crossed a tick 747 * boundary during the last second, so correct the tick. Very 748 * intricate. 749 */ 750 u_nsec = nsec; 751 if (u_nsec > (NANOSECOND >> 1)) 752 u_nsec -= NANOSECOND; 753 else if (u_nsec < -(NANOSECOND >> 1)) 754 u_nsec += NANOSECOND; 755 pps_fcount += u_nsec; 756 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 757 return; 758 time_status &= ~STA_PPSJITTER; 759 760 /* 761 * A three-stage median filter is used to help denoise the PPS 762 * time. The median sample becomes the time offset estimate; the 763 * difference between the other two samples becomes the time 764 * dispersion (jitter) estimate. 765 */ 766 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 767 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 768 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 769 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 770 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 771 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 772 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 773 } else { 774 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 775 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 776 } 777 } else { 778 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 779 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 780 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 781 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 782 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 783 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 784 } else { 785 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 786 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 787 } 788 } 789 790 /* 791 * Nominal jitter is due to PPS signal noise and interrupt 792 * latency. If it exceeds the popcorn threshold, the sample is 793 * discarded. otherwise, if so enabled, the time offset is 794 * updated. We can tolerate a modest loss of data here without 795 * much degrading time accuracy. 796 */ 797 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 798 time_status |= STA_PPSJITTER; 799 pps_jitcnt++; 800 } else if (time_status & STA_PPSTIME) { 801 time_monitor = -v_nsec; 802 L_LINT(time_offset, time_monitor); 803 } 804 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 805 u_sec = pps_tf[0].tv_sec - pps_lastsec; 806 if (u_sec < (1 << pps_shift)) 807 return; 808 809 /* 810 * At the end of the calibration interval the difference between 811 * the first and last counter values becomes the scaled 812 * frequency. It will later be divided by the length of the 813 * interval to determine the frequency update. If the frequency 814 * exceeds a sanity threshold, or if the actual calibration 815 * interval is not equal to the expected length, the data are 816 * discarded. We can tolerate a modest loss of data here without 817 * much degrading frequency accuracy. 818 */ 819 pps_calcnt++; 820 v_nsec = -pps_fcount; 821 pps_lastsec = pps_tf[0].tv_sec; 822 pps_fcount = 0; 823 u_nsec = MAXFREQ << pps_shift; 824 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 825 pps_shift)) { 826 time_status |= STA_PPSERROR; 827 pps_errcnt++; 828 return; 829 } 830 831 /* 832 * Here the raw frequency offset and wander (stability) is 833 * calculated. If the wander is less than the wander threshold 834 * for four consecutive averaging intervals, the interval is 835 * doubled; if it is greater than the threshold for four 836 * consecutive intervals, the interval is halved. The scaled 837 * frequency offset is converted to frequency offset. The 838 * stability metric is calculated as the average of recent 839 * frequency changes, but is used only for performance 840 * monitoring. 841 */ 842 L_LINT(ftemp, v_nsec); 843 L_RSHIFT(ftemp, pps_shift); 844 L_SUB(ftemp, pps_freq); 845 u_nsec = L_GINT(ftemp); 846 if (u_nsec > PPS_MAXWANDER) { 847 L_LINT(ftemp, PPS_MAXWANDER); 848 pps_intcnt--; 849 time_status |= STA_PPSWANDER; 850 pps_stbcnt++; 851 } else if (u_nsec < -PPS_MAXWANDER) { 852 L_LINT(ftemp, -PPS_MAXWANDER); 853 pps_intcnt--; 854 time_status |= STA_PPSWANDER; 855 pps_stbcnt++; 856 } else { 857 pps_intcnt++; 858 } 859 if (pps_intcnt >= 4) { 860 pps_intcnt = 4; 861 if (pps_shift < pps_shiftmax) { 862 pps_shift++; 863 pps_intcnt = 0; 864 } 865 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 866 pps_intcnt = -4; 867 if (pps_shift > PPS_FAVG) { 868 pps_shift--; 869 pps_intcnt = 0; 870 } 871 } 872 if (u_nsec < 0) 873 u_nsec = -u_nsec; 874 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 875 876 /* 877 * The PPS frequency is recalculated and clamped to the maximum 878 * MAXFREQ. If enabled, the system clock frequency is updated as 879 * well. 880 */ 881 L_ADD(pps_freq, ftemp); 882 u_nsec = L_GINT(pps_freq); 883 if (u_nsec > MAXFREQ) 884 L_LINT(pps_freq, MAXFREQ); 885 else if (u_nsec < -MAXFREQ) 886 L_LINT(pps_freq, -MAXFREQ); 887 if (time_status & STA_PPSFREQ) 888 time_freq = pps_freq; 889 } 890 #endif /* PPS_SYNC */ 891 892 #ifndef _SYS_SYSPROTO_H_ 893 struct adjtime_args { 894 struct timeval *delta; 895 struct timeval *olddelta; 896 }; 897 #endif 898 /* 899 * MPSAFE 900 */ 901 /* ARGSUSED */ 902 int 903 adjtime(struct thread *td, struct adjtime_args *uap) 904 { 905 struct timeval atv; 906 int error; 907 908 if ((error = suser(td))) 909 return (error); 910 911 mtx_lock(&Giant); 912 if (uap->olddelta) { 913 atv.tv_sec = time_adjtime / 1000000; 914 atv.tv_usec = time_adjtime % 1000000; 915 if (atv.tv_usec < 0) { 916 atv.tv_usec += 1000000; 917 atv.tv_sec--; 918 } 919 error = copyout(&atv, uap->olddelta, sizeof(atv)); 920 if (error) 921 goto done2; 922 } 923 if (uap->delta) { 924 error = copyin(uap->delta, &atv, sizeof(atv)); 925 if (error) 926 goto done2; 927 time_adjtime = (int64_t)atv.tv_sec * 1000000 + atv.tv_usec; 928 } 929 done2: 930 mtx_unlock(&Giant); 931 return (error); 932 } 933
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