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 * Copyright (c) David L. Mills 1993-2001 * 4 * * 5 * Permission to use, copy, modify, and distribute this software and * 6 * its documentation for any purpose and without fee is hereby * 7 * granted, provided that the above copyright notice appears in all * 8 * copies and that both the copyright notice and this permission * 9 * notice appear in supporting documentation, and that the name * 10 * University of Delaware not be used in advertising or publicity * 11 * pertaining to distribution of the software without specific, * 12 * written prior permission. The University of Delaware makes no * 13 * representations about the suitability this software for any * 14 * purpose. It is provided "as is" without express or implied * 15 * warranty. * 16 * * 17 **********************************************************************/ 18 19 /* 20 * Adapted from the original sources for FreeBSD and timecounters by: 21 * Poul-Henning Kamp <phk@FreeBSD.org>. 22 * 23 * The 32bit version of the "LP" macros seems a bit past its "sell by" 24 * date so I have retained only the 64bit version and included it directly 25 * in this file. 26 * 27 * Only minor changes done to interface with the timecounters over in 28 * sys/kern/kern_clock.c. Some of the comments below may be (even more) 29 * confusing and/or plain wrong in that context. 30 * 31 * $FreeBSD: releng/5.0/sys/kern/kern_ntptime.c 108837 2003-01-06 22:47:16Z peter $ 32 */ 33 34 #include "opt_ntp.h" 35 36 #include <sys/param.h> 37 #include <sys/systm.h> 38 #include <sys/sysproto.h> 39 #include <sys/kernel.h> 40 #include <sys/proc.h> 41 #include <sys/lock.h> 42 #include <sys/mutex.h> 43 #include <sys/time.h> 44 #include <sys/timex.h> 45 #include <sys/timetc.h> 46 #include <sys/timepps.h> 47 #include <sys/sysctl.h> 48 49 /* 50 * Single-precision macros for 64-bit machines 51 */ 52 typedef long long l_fp; 53 #define L_ADD(v, u) ((v) += (u)) 54 #define L_SUB(v, u) ((v) -= (u)) 55 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 56 #define L_NEG(v) ((v) = -(v)) 57 #define L_RSHIFT(v, n) \ 58 do { \ 59 if ((v) < 0) \ 60 (v) = -(-(v) >> (n)); \ 61 else \ 62 (v) = (v) >> (n); \ 63 } while (0) 64 #define L_MPY(v, a) ((v) *= (a)) 65 #define L_CLR(v) ((v) = 0) 66 #define L_ISNEG(v) ((v) < 0) 67 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 68 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 69 70 /* 71 * Generic NTP kernel interface 72 * 73 * These routines constitute the Network Time Protocol (NTP) interfaces 74 * for user and daemon application programs. The ntp_gettime() routine 75 * provides the time, maximum error (synch distance) and estimated error 76 * (dispersion) to client user application programs. The ntp_adjtime() 77 * routine is used by the NTP daemon to adjust the system clock to an 78 * externally derived time. The time offset and related variables set by 79 * this routine are used by other routines in this module to adjust the 80 * phase and frequency of the clock discipline loop which controls the 81 * system clock. 82 * 83 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 84 * defined), the time at each tick interrupt is derived directly from 85 * the kernel time variable. When the kernel time is reckoned in 86 * microseconds, (NTP_NANO undefined), the time is derived from the 87 * kernel time variable together with a variable representing the 88 * leftover nanoseconds at the last tick interrupt. In either case, the 89 * current nanosecond time is reckoned from these values plus an 90 * interpolated value derived by the clock routines in another 91 * architecture-specific module. The interpolation can use either a 92 * dedicated counter or a processor cycle counter (PCC) implemented in 93 * some architectures. 94 * 95 * Note that all routines must run at priority splclock or higher. 96 */ 97 /* 98 * Phase/frequency-lock loop (PLL/FLL) definitions 99 * 100 * The nanosecond clock discipline uses two variable types, time 101 * variables and frequency variables. Both types are represented as 64- 102 * bit fixed-point quantities with the decimal point between two 32-bit 103 * halves. On a 32-bit machine, each half is represented as a single 104 * word and mathematical operations are done using multiple-precision 105 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 106 * used. 107 * 108 * A time variable is a signed 64-bit fixed-point number in ns and 109 * fraction. It represents the remaining time offset to be amortized 110 * over succeeding tick interrupts. The maximum time offset is about 111 * 0.5 s and the resolution is about 2.3e-10 ns. 112 * 113 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 114 * 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 1 115 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 116 * |s s s| ns | 117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 * | fraction | 119 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 * 121 * A frequency variable is a signed 64-bit fixed-point number in ns/s 122 * and fraction. It represents the ns and fraction to be added to the 123 * kernel time variable at each second. The maximum frequency offset is 124 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 125 * 126 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 127 * 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 1 128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 * |s s s s s s s s s s s s s| ns/s | 130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 * | fraction | 132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 133 */ 134 /* 135 * The following variables establish the state of the PLL/FLL and the 136 * residual time and frequency offset of the local clock. 137 */ 138 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 139 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 140 141 static int time_state = TIME_OK; /* clock state */ 142 static int time_status = STA_UNSYNC; /* clock status bits */ 143 static long time_tai; /* TAI offset (s) */ 144 static long time_monitor; /* last time offset scaled (ns) */ 145 static long time_constant; /* poll interval (shift) (s) */ 146 static long time_precision = 1; /* clock precision (ns) */ 147 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 148 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 149 static long time_reftime; /* time at last adjustment (s) */ 150 static l_fp time_offset; /* time offset (ns) */ 151 static l_fp time_freq; /* frequency offset (ns/s) */ 152 static l_fp time_adj; /* tick adjust (ns/s) */ 153 154 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 155 156 #ifdef PPS_SYNC 157 /* 158 * The following variables are used when a pulse-per-second (PPS) signal 159 * is available and connected via a modem control lead. They establish 160 * the engineering parameters of the clock discipline loop when 161 * controlled by the PPS signal. 162 */ 163 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 164 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 165 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 166 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 167 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 168 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 169 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 170 171 static struct timespec pps_tf[3]; /* phase median filter */ 172 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 173 static long pps_fcount; /* frequency accumulator */ 174 static long pps_jitter; /* nominal jitter (ns) */ 175 static long pps_stabil; /* nominal stability (scaled ns/s) */ 176 static long pps_lastsec; /* time at last calibration (s) */ 177 static int pps_valid; /* signal watchdog counter */ 178 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 179 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 180 static int pps_intcnt; /* wander counter */ 181 182 /* 183 * PPS signal quality monitors 184 */ 185 static long pps_calcnt; /* calibration intervals */ 186 static long pps_jitcnt; /* jitter limit exceeded */ 187 static long pps_stbcnt; /* stability limit exceeded */ 188 static long pps_errcnt; /* calibration errors */ 189 #endif /* PPS_SYNC */ 190 /* 191 * End of phase/frequency-lock loop (PLL/FLL) definitions 192 */ 193 194 static void ntp_init(void); 195 static void hardupdate(long offset); 196 197 /* 198 * ntp_gettime() - NTP user application interface 199 * 200 * See the timex.h header file for synopsis and API description. Note 201 * that the TAI offset is returned in the ntvtimeval.tai structure 202 * member. 203 */ 204 static int 205 ntp_sysctl(SYSCTL_HANDLER_ARGS) 206 { 207 struct ntptimeval ntv; /* temporary structure */ 208 struct timespec atv; /* nanosecond time */ 209 210 nanotime(&atv); 211 ntv.time.tv_sec = atv.tv_sec; 212 ntv.time.tv_nsec = atv.tv_nsec; 213 ntv.maxerror = time_maxerror; 214 ntv.esterror = time_esterror; 215 ntv.tai = time_tai; 216 ntv.time_state = time_state; 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 ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 227 228 /* 229 * PPS signal lost when either time or frequency synchronization 230 * requested 231 */ 232 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 233 !(time_status & STA_PPSSIGNAL)) || 234 235 /* 236 * PPS jitter exceeded when time synchronization requested 237 */ 238 (time_status & STA_PPSTIME && 239 time_status & STA_PPSJITTER) || 240 241 /* 242 * PPS wander exceeded or calibration error when frequency 243 * synchronization requested 244 */ 245 (time_status & STA_PPSFREQ && 246 time_status & (STA_PPSWANDER | STA_PPSERROR))) 247 ntv.time_state = TIME_ERROR; 248 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 249 } 250 251 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 252 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 253 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 254 255 #ifdef PPS_SYNC 256 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 258 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 259 260 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 261 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 262 #endif 263 /* 264 * ntp_adjtime() - NTP daemon application interface 265 * 266 * See the timex.h header file for synopsis and API description. Note 267 * that the timex.constant structure member has a dual purpose to set 268 * the time constant and to set the TAI offset. 269 */ 270 #ifndef _SYS_SYSPROTO_H_ 271 struct ntp_adjtime_args { 272 struct timex *tp; 273 }; 274 #endif 275 276 /* 277 * MPSAFE 278 */ 279 int 280 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 281 { 282 struct timex ntv; /* temporary structure */ 283 long freq; /* frequency ns/s) */ 284 int modes; /* mode bits from structure */ 285 int s; /* caller priority */ 286 int error; 287 288 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 289 if (error) 290 return(error); 291 292 /* 293 * Update selected clock variables - only the superuser can 294 * change anything. Note that there is no error checking here on 295 * the assumption the superuser should know what it is doing. 296 * Note that either the time constant or TAI offset are loaded 297 * from the ntv.constant member, depending on the mode bits. If 298 * the STA_PLL bit in the status word is cleared, the state and 299 * status words are reset to the initial values at boot. 300 */ 301 mtx_lock(&Giant); 302 modes = ntv.modes; 303 if (modes) 304 error = suser(td); 305 if (error) 306 goto done2; 307 s = splclock(); 308 if (modes & MOD_MAXERROR) 309 time_maxerror = ntv.maxerror; 310 if (modes & MOD_ESTERROR) 311 time_esterror = ntv.esterror; 312 if (modes & MOD_STATUS) { 313 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 314 time_state = TIME_OK; 315 time_status = STA_UNSYNC; 316 #ifdef PPS_SYNC 317 pps_shift = PPS_FAVG; 318 #endif /* PPS_SYNC */ 319 } 320 time_status &= STA_RONLY; 321 time_status |= ntv.status & ~STA_RONLY; 322 } 323 if (modes & MOD_TIMECONST) { 324 if (ntv.constant < 0) 325 time_constant = 0; 326 else if (ntv.constant > MAXTC) 327 time_constant = MAXTC; 328 else 329 time_constant = ntv.constant; 330 } 331 if (modes & MOD_TAI) { 332 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 333 time_tai = ntv.constant; 334 } 335 #ifdef PPS_SYNC 336 if (modes & MOD_PPSMAX) { 337 if (ntv.shift < PPS_FAVG) 338 pps_shiftmax = PPS_FAVG; 339 else if (ntv.shift > PPS_FAVGMAX) 340 pps_shiftmax = PPS_FAVGMAX; 341 else 342 pps_shiftmax = ntv.shift; 343 } 344 #endif /* PPS_SYNC */ 345 if (modes & MOD_NANO) 346 time_status |= STA_NANO; 347 if (modes & MOD_MICRO) 348 time_status &= ~STA_NANO; 349 if (modes & MOD_CLKB) 350 time_status |= STA_CLK; 351 if (modes & MOD_CLKA) 352 time_status &= ~STA_CLK; 353 if (modes & MOD_OFFSET) { 354 if (time_status & STA_NANO) 355 hardupdate(ntv.offset); 356 else 357 hardupdate(ntv.offset * 1000); 358 } 359 if (modes & MOD_FREQUENCY) { 360 freq = (ntv.freq * 1000LL) >> 16; 361 if (freq > MAXFREQ) 362 L_LINT(time_freq, MAXFREQ); 363 else if (freq < -MAXFREQ) 364 L_LINT(time_freq, -MAXFREQ); 365 else 366 L_LINT(time_freq, freq); 367 #ifdef PPS_SYNC 368 pps_freq = time_freq; 369 #endif /* PPS_SYNC */ 370 } 371 372 /* 373 * Retrieve all clock variables. Note that the TAI offset is 374 * returned only by ntp_gettime(); 375 */ 376 if (time_status & STA_NANO) 377 ntv.offset = L_GINT(time_offset); 378 else 379 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 380 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 381 ntv.maxerror = time_maxerror; 382 ntv.esterror = time_esterror; 383 ntv.status = time_status; 384 ntv.constant = time_constant; 385 if (time_status & STA_NANO) 386 ntv.precision = time_precision; 387 else 388 ntv.precision = time_precision / 1000; 389 ntv.tolerance = MAXFREQ * SCALE_PPM; 390 #ifdef PPS_SYNC 391 ntv.shift = pps_shift; 392 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 393 if (time_status & STA_NANO) 394 ntv.jitter = pps_jitter; 395 else 396 ntv.jitter = pps_jitter / 1000; 397 ntv.stabil = pps_stabil; 398 ntv.calcnt = pps_calcnt; 399 ntv.errcnt = pps_errcnt; 400 ntv.jitcnt = pps_jitcnt; 401 ntv.stbcnt = pps_stbcnt; 402 #endif /* PPS_SYNC */ 403 splx(s); 404 405 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 406 if (error) 407 goto done2; 408 409 /* 410 * Status word error decode. See comments in 411 * ntp_gettime() routine. 412 */ 413 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 414 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 415 !(time_status & STA_PPSSIGNAL)) || 416 (time_status & STA_PPSTIME && 417 time_status & STA_PPSJITTER) || 418 (time_status & STA_PPSFREQ && 419 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 420 td->td_retval[0] = TIME_ERROR; 421 } else { 422 td->td_retval[0] = time_state; 423 } 424 done2: 425 mtx_unlock(&Giant); 426 return (error); 427 } 428 429 /* 430 * second_overflow() - called after ntp_tick_adjust() 431 * 432 * This routine is ordinarily called immediately following the above 433 * routine ntp_tick_adjust(). While these two routines are normally 434 * combined, they are separated here only for the purposes of 435 * simulation. 436 */ 437 void 438 ntp_update_second(int64_t *adjustment, time_t *newsec) 439 { 440 int tickrate; 441 l_fp ftemp; /* 32/64-bit temporary */ 442 443 /* 444 * On rollover of the second both the nanosecond and microsecond 445 * clocks are updated and the state machine cranked as 446 * necessary. The phase adjustment to be used for the next 447 * second is calculated and the maximum error is increased by 448 * the tolerance. 449 */ 450 time_maxerror += MAXFREQ / 1000; 451 452 /* 453 * Leap second processing. If in leap-insert state at 454 * the end of the day, the system clock is set back one 455 * second; if in leap-delete state, the system clock is 456 * set ahead one second. The nano_time() routine or 457 * external clock driver will insure that reported time 458 * is always monotonic. 459 */ 460 switch (time_state) { 461 462 /* 463 * No warning. 464 */ 465 case TIME_OK: 466 if (time_status & STA_INS) 467 time_state = TIME_INS; 468 else if (time_status & STA_DEL) 469 time_state = TIME_DEL; 470 break; 471 472 /* 473 * Insert second 23:59:60 following second 474 * 23:59:59. 475 */ 476 case TIME_INS: 477 if (!(time_status & STA_INS)) 478 time_state = TIME_OK; 479 else if ((*newsec) % 86400 == 0) { 480 (*newsec)--; 481 time_state = TIME_OOP; 482 } 483 break; 484 485 /* 486 * Delete second 23:59:59. 487 */ 488 case TIME_DEL: 489 if (!(time_status & STA_DEL)) 490 time_state = TIME_OK; 491 else if (((*newsec) + 1) % 86400 == 0) { 492 (*newsec)++; 493 time_tai--; 494 time_state = TIME_WAIT; 495 } 496 break; 497 498 /* 499 * Insert second in progress. 500 */ 501 case TIME_OOP: 502 time_tai++; 503 time_state = TIME_WAIT; 504 break; 505 506 /* 507 * Wait for status bits to clear. 508 */ 509 case TIME_WAIT: 510 if (!(time_status & (STA_INS | STA_DEL))) 511 time_state = TIME_OK; 512 } 513 514 /* 515 * Compute the total time adjustment for the next second 516 * in ns. The offset is reduced by a factor depending on 517 * whether the PPS signal is operating. Note that the 518 * value is in effect scaled by the clock frequency, 519 * since the adjustment is added at each tick interrupt. 520 */ 521 ftemp = time_offset; 522 #ifdef PPS_SYNC 523 /* XXX even if PPS signal dies we should finish adjustment ? */ 524 if (time_status & STA_PPSTIME && time_status & 525 STA_PPSSIGNAL) 526 L_RSHIFT(ftemp, pps_shift); 527 else 528 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 529 #else 530 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 531 #endif /* PPS_SYNC */ 532 time_adj = ftemp; 533 L_SUB(time_offset, ftemp); 534 L_ADD(time_adj, time_freq); 535 536 /* 537 * Apply any correction from adjtime(2). If more than one second 538 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM) 539 * until the last second is slewed the final < 500 usecs. 540 */ 541 if (time_adjtime != 0) { 542 if (time_adjtime > 1000000) 543 tickrate = 5000; 544 else if (time_adjtime < -1000000) 545 tickrate = -5000; 546 else if (time_adjtime > 500) 547 tickrate = 500; 548 else if (time_adjtime < -500) 549 tickrate = -500; 550 else if (time_adjtime != 0) 551 tickrate = time_adjtime; 552 else 553 tickrate = 0; /* GCC sucks! */ 554 time_adjtime -= tickrate; 555 L_LINT(ftemp, tickrate * 1000); 556 L_ADD(time_adj, ftemp); 557 } 558 *adjustment = time_adj; 559 560 #ifdef PPS_SYNC 561 if (pps_valid > 0) 562 pps_valid--; 563 else 564 time_status &= ~STA_PPSSIGNAL; 565 #endif /* PPS_SYNC */ 566 } 567 568 /* 569 * ntp_init() - initialize variables and structures 570 * 571 * This routine must be called after the kernel variables hz and tick 572 * are set or changed and before the next tick interrupt. In this 573 * particular implementation, these values are assumed set elsewhere in 574 * the kernel. The design allows the clock frequency and tick interval 575 * to be changed while the system is running. So, this routine should 576 * probably be integrated with the code that does that. 577 */ 578 static void 579 ntp_init() 580 { 581 582 /* 583 * The following variables are initialized only at startup. Only 584 * those structures not cleared by the compiler need to be 585 * initialized, and these only in the simulator. In the actual 586 * kernel, any nonzero values here will quickly evaporate. 587 */ 588 L_CLR(time_offset); 589 L_CLR(time_freq); 590 #ifdef PPS_SYNC 591 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 592 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 593 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 594 pps_fcount = 0; 595 L_CLR(pps_freq); 596 #endif /* PPS_SYNC */ 597 } 598 599 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL) 600 601 /* 602 * hardupdate() - local clock update 603 * 604 * This routine is called by ntp_adjtime() to update the local clock 605 * phase and frequency. The implementation is of an adaptive-parameter, 606 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 607 * time and frequency offset estimates for each call. If the kernel PPS 608 * discipline code is configured (PPS_SYNC), the PPS signal itself 609 * determines the new time offset, instead of the calling argument. 610 * Presumably, calls to ntp_adjtime() occur only when the caller 611 * believes the local clock is valid within some bound (+-128 ms with 612 * NTP). If the caller's time is far different than the PPS time, an 613 * argument will ensue, and it's not clear who will lose. 614 * 615 * For uncompensated quartz crystal oscillators and nominal update 616 * intervals less than 256 s, operation should be in phase-lock mode, 617 * where the loop is disciplined to phase. For update intervals greater 618 * than 1024 s, operation should be in frequency-lock mode, where the 619 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 620 * is selected by the STA_MODE status bit. 621 */ 622 static void 623 hardupdate(offset) 624 long offset; /* clock offset (ns) */ 625 { 626 long mtemp; 627 l_fp ftemp; 628 629 /* 630 * Select how the phase is to be controlled and from which 631 * source. If the PPS signal is present and enabled to 632 * discipline the time, the PPS offset is used; otherwise, the 633 * argument offset is used. 634 */ 635 if (!(time_status & STA_PLL)) 636 return; 637 if (!(time_status & STA_PPSTIME && time_status & 638 STA_PPSSIGNAL)) { 639 if (offset > MAXPHASE) 640 time_monitor = MAXPHASE; 641 else if (offset < -MAXPHASE) 642 time_monitor = -MAXPHASE; 643 else 644 time_monitor = offset; 645 L_LINT(time_offset, time_monitor); 646 } 647 648 /* 649 * Select how the frequency is to be controlled and in which 650 * mode (PLL or FLL). If the PPS signal is present and enabled 651 * to discipline the frequency, the PPS frequency is used; 652 * otherwise, the argument offset is used to compute it. 653 */ 654 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 655 time_reftime = time_second; 656 return; 657 } 658 if (time_status & STA_FREQHOLD || time_reftime == 0) 659 time_reftime = time_second; 660 mtemp = time_second - time_reftime; 661 L_LINT(ftemp, time_monitor); 662 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 663 L_MPY(ftemp, mtemp); 664 L_ADD(time_freq, ftemp); 665 time_status &= ~STA_MODE; 666 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 667 MAXSEC)) { 668 L_LINT(ftemp, (time_monitor << 4) / mtemp); 669 L_RSHIFT(ftemp, SHIFT_FLL + 4); 670 L_ADD(time_freq, ftemp); 671 time_status |= STA_MODE; 672 } 673 time_reftime = time_second; 674 if (L_GINT(time_freq) > MAXFREQ) 675 L_LINT(time_freq, MAXFREQ); 676 else if (L_GINT(time_freq) < -MAXFREQ) 677 L_LINT(time_freq, -MAXFREQ); 678 } 679 680 #ifdef PPS_SYNC 681 /* 682 * hardpps() - discipline CPU clock oscillator to external PPS signal 683 * 684 * This routine is called at each PPS interrupt in order to discipline 685 * the CPU clock oscillator to the PPS signal. There are two independent 686 * first-order feedback loops, one for the phase, the other for the 687 * frequency. The phase loop measures and grooms the PPS phase offset 688 * and leaves it in a handy spot for the seconds overflow routine. The 689 * frequency loop averages successive PPS phase differences and 690 * calculates the PPS frequency offset, which is also processed by the 691 * seconds overflow routine. The code requires the caller to capture the 692 * time and architecture-dependent hardware counter values in 693 * nanoseconds at the on-time PPS signal transition. 694 * 695 * Note that, on some Unix systems this routine runs at an interrupt 696 * priority level higher than the timer interrupt routine hardclock(). 697 * Therefore, the variables used are distinct from the hardclock() 698 * variables, except for the actual time and frequency variables, which 699 * are determined by this routine and updated atomically. 700 */ 701 void 702 hardpps(tsp, nsec) 703 struct timespec *tsp; /* time at PPS */ 704 long nsec; /* hardware counter at PPS */ 705 { 706 long u_sec, u_nsec, v_nsec; /* temps */ 707 l_fp ftemp; 708 709 /* 710 * The signal is first processed by a range gate and frequency 711 * discriminator. The range gate rejects noise spikes outside 712 * the range +-500 us. The frequency discriminator rejects input 713 * signals with apparent frequency outside the range 1 +-500 714 * PPM. If two hits occur in the same second, we ignore the 715 * later hit; if not and a hit occurs outside the range gate, 716 * keep the later hit for later comparison, but do not process 717 * it. 718 */ 719 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 720 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 721 pps_valid = PPS_VALID; 722 u_sec = tsp->tv_sec; 723 u_nsec = tsp->tv_nsec; 724 if (u_nsec >= (NANOSECOND >> 1)) { 725 u_nsec -= NANOSECOND; 726 u_sec++; 727 } 728 v_nsec = u_nsec - pps_tf[0].tv_nsec; 729 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 730 MAXFREQ) 731 return; 732 pps_tf[2] = pps_tf[1]; 733 pps_tf[1] = pps_tf[0]; 734 pps_tf[0].tv_sec = u_sec; 735 pps_tf[0].tv_nsec = u_nsec; 736 737 /* 738 * Compute the difference between the current and previous 739 * counter values. If the difference exceeds 0.5 s, assume it 740 * has wrapped around, so correct 1.0 s. If the result exceeds 741 * the tick interval, the sample point has crossed a tick 742 * boundary during the last second, so correct the tick. Very 743 * intricate. 744 */ 745 u_nsec = nsec; 746 if (u_nsec > (NANOSECOND >> 1)) 747 u_nsec -= NANOSECOND; 748 else if (u_nsec < -(NANOSECOND >> 1)) 749 u_nsec += NANOSECOND; 750 pps_fcount += u_nsec; 751 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 752 return; 753 time_status &= ~STA_PPSJITTER; 754 755 /* 756 * A three-stage median filter is used to help denoise the PPS 757 * time. The median sample becomes the time offset estimate; the 758 * difference between the other two samples becomes the time 759 * dispersion (jitter) estimate. 760 */ 761 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 762 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 763 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 764 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 765 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 766 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 767 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 768 } else { 769 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 770 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 771 } 772 } else { 773 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 774 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 775 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 776 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 777 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 778 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 779 } else { 780 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 781 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 782 } 783 } 784 785 /* 786 * Nominal jitter is due to PPS signal noise and interrupt 787 * latency. If it exceeds the popcorn threshold, the sample is 788 * discarded. otherwise, if so enabled, the time offset is 789 * updated. We can tolerate a modest loss of data here without 790 * much degrading time accuracy. 791 */ 792 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 793 time_status |= STA_PPSJITTER; 794 pps_jitcnt++; 795 } else if (time_status & STA_PPSTIME) { 796 time_monitor = -v_nsec; 797 L_LINT(time_offset, time_monitor); 798 } 799 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 800 u_sec = pps_tf[0].tv_sec - pps_lastsec; 801 if (u_sec < (1 << pps_shift)) 802 return; 803 804 /* 805 * At the end of the calibration interval the difference between 806 * the first and last counter values becomes the scaled 807 * frequency. It will later be divided by the length of the 808 * interval to determine the frequency update. If the frequency 809 * exceeds a sanity threshold, or if the actual calibration 810 * interval is not equal to the expected length, the data are 811 * discarded. We can tolerate a modest loss of data here without 812 * much degrading frequency accuracy. 813 */ 814 pps_calcnt++; 815 v_nsec = -pps_fcount; 816 pps_lastsec = pps_tf[0].tv_sec; 817 pps_fcount = 0; 818 u_nsec = MAXFREQ << pps_shift; 819 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 820 pps_shift)) { 821 time_status |= STA_PPSERROR; 822 pps_errcnt++; 823 return; 824 } 825 826 /* 827 * Here the raw frequency offset and wander (stability) is 828 * calculated. If the wander is less than the wander threshold 829 * for four consecutive averaging intervals, the interval is 830 * doubled; if it is greater than the threshold for four 831 * consecutive intervals, the interval is halved. The scaled 832 * frequency offset is converted to frequency offset. The 833 * stability metric is calculated as the average of recent 834 * frequency changes, but is used only for performance 835 * monitoring. 836 */ 837 L_LINT(ftemp, v_nsec); 838 L_RSHIFT(ftemp, pps_shift); 839 L_SUB(ftemp, pps_freq); 840 u_nsec = L_GINT(ftemp); 841 if (u_nsec > PPS_MAXWANDER) { 842 L_LINT(ftemp, PPS_MAXWANDER); 843 pps_intcnt--; 844 time_status |= STA_PPSWANDER; 845 pps_stbcnt++; 846 } else if (u_nsec < -PPS_MAXWANDER) { 847 L_LINT(ftemp, -PPS_MAXWANDER); 848 pps_intcnt--; 849 time_status |= STA_PPSWANDER; 850 pps_stbcnt++; 851 } else { 852 pps_intcnt++; 853 } 854 if (pps_intcnt >= 4) { 855 pps_intcnt = 4; 856 if (pps_shift < pps_shiftmax) { 857 pps_shift++; 858 pps_intcnt = 0; 859 } 860 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 861 pps_intcnt = -4; 862 if (pps_shift > PPS_FAVG) { 863 pps_shift--; 864 pps_intcnt = 0; 865 } 866 } 867 if (u_nsec < 0) 868 u_nsec = -u_nsec; 869 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 870 871 /* 872 * The PPS frequency is recalculated and clamped to the maximum 873 * MAXFREQ. If enabled, the system clock frequency is updated as 874 * well. 875 */ 876 L_ADD(pps_freq, ftemp); 877 u_nsec = L_GINT(pps_freq); 878 if (u_nsec > MAXFREQ) 879 L_LINT(pps_freq, MAXFREQ); 880 else if (u_nsec < -MAXFREQ) 881 L_LINT(pps_freq, -MAXFREQ); 882 if (time_status & STA_PPSFREQ) 883 time_freq = pps_freq; 884 } 885 #endif /* PPS_SYNC */ 886 887 #ifndef _SYS_SYSPROTO_H_ 888 struct adjtime_args { 889 struct timeval *delta; 890 struct timeval *olddelta; 891 }; 892 #endif 893 /* 894 * MPSAFE 895 */ 896 /* ARGSUSED */ 897 int 898 adjtime(struct thread *td, struct adjtime_args *uap) 899 { 900 struct timeval atv; 901 int error; 902 903 if ((error = suser(td))) 904 return (error); 905 906 mtx_lock(&Giant); 907 if (uap->olddelta) { 908 atv.tv_sec = time_adjtime / 1000000; 909 atv.tv_usec = time_adjtime % 1000000; 910 if (atv.tv_usec < 0) { 911 atv.tv_usec += 1000000; 912 atv.tv_sec--; 913 } 914 error = copyout(&atv, uap->olddelta, sizeof(atv)); 915 if (error) 916 goto done2; 917 } 918 if (uap->delta) { 919 error = copyin(uap->delta, &atv, sizeof(atv)); 920 if (error) 921 goto done2; 922 time_adjtime = (int64_t)atv.tv_sec * 1000000 + atv.tv_usec; 923 } 924 done2: 925 mtx_unlock(&Giant); 926 return (error); 927 } 928
Cache object: 924693a8c772671ed1a6f7cf5e69c7ee
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