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 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD: releng/5.2/sys/kern/kern_ntptime.c 116838 2003-06-25 20:56:40Z imp $"); 34 35 #include "opt_ntp.h" 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/sysproto.h> 40 #include <sys/kernel.h> 41 #include <sys/proc.h> 42 #include <sys/lock.h> 43 #include <sys/mutex.h> 44 #include <sys/time.h> 45 #include <sys/timex.h> 46 #include <sys/timetc.h> 47 #include <sys/timepps.h> 48 #include <sys/sysctl.h> 49 50 /* 51 * Single-precision macros for 64-bit machines 52 */ 53 typedef long long l_fp; 54 #define L_ADD(v, u) ((v) += (u)) 55 #define L_SUB(v, u) ((v) -= (u)) 56 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 57 #define L_NEG(v) ((v) = -(v)) 58 #define L_RSHIFT(v, n) \ 59 do { \ 60 if ((v) < 0) \ 61 (v) = -(-(v) >> (n)); \ 62 else \ 63 (v) = (v) >> (n); \ 64 } while (0) 65 #define L_MPY(v, a) ((v) *= (a)) 66 #define L_CLR(v) ((v) = 0) 67 #define L_ISNEG(v) ((v) < 0) 68 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 69 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 70 71 /* 72 * Generic NTP kernel interface 73 * 74 * These routines constitute the Network Time Protocol (NTP) interfaces 75 * for user and daemon application programs. The ntp_gettime() routine 76 * provides the time, maximum error (synch distance) and estimated error 77 * (dispersion) to client user application programs. The ntp_adjtime() 78 * routine is used by the NTP daemon to adjust the system clock to an 79 * externally derived time. The time offset and related variables set by 80 * this routine are used by other routines in this module to adjust the 81 * phase and frequency of the clock discipline loop which controls the 82 * system clock. 83 * 84 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 85 * defined), the time at each tick interrupt is derived directly from 86 * the kernel time variable. When the kernel time is reckoned in 87 * microseconds, (NTP_NANO undefined), the time is derived from the 88 * kernel time variable together with a variable representing the 89 * leftover nanoseconds at the last tick interrupt. In either case, the 90 * current nanosecond time is reckoned from these values plus an 91 * interpolated value derived by the clock routines in another 92 * architecture-specific module. The interpolation can use either a 93 * dedicated counter or a processor cycle counter (PCC) implemented in 94 * some architectures. 95 * 96 * Note that all routines must run at priority splclock or higher. 97 */ 98 /* 99 * Phase/frequency-lock loop (PLL/FLL) definitions 100 * 101 * The nanosecond clock discipline uses two variable types, time 102 * variables and frequency variables. Both types are represented as 64- 103 * bit fixed-point quantities with the decimal point between two 32-bit 104 * halves. On a 32-bit machine, each half is represented as a single 105 * word and mathematical operations are done using multiple-precision 106 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 107 * used. 108 * 109 * A time variable is a signed 64-bit fixed-point number in ns and 110 * fraction. It represents the remaining time offset to be amortized 111 * over succeeding tick interrupts. The maximum time offset is about 112 * 0.5 s and the resolution is about 2.3e-10 ns. 113 * 114 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 115 * 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 1 116 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 117 * |s s s| ns | 118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 119 * | fraction | 120 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 121 * 122 * A frequency variable is a signed 64-bit fixed-point number in ns/s 123 * and fraction. It represents the ns and fraction to be added to the 124 * kernel time variable at each second. The maximum frequency offset is 125 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 126 * 127 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 128 * 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 1 129 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 130 * |s s s s s s s s s s s s s| ns/s | 131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 * | fraction | 133 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 */ 135 /* 136 * The following variables establish the state of the PLL/FLL and the 137 * residual time and frequency offset of the local clock. 138 */ 139 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 140 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 141 142 static int time_state = TIME_OK; /* clock state */ 143 static int time_status = STA_UNSYNC; /* clock status bits */ 144 static long time_tai; /* TAI offset (s) */ 145 static long time_monitor; /* last time offset scaled (ns) */ 146 static long time_constant; /* poll interval (shift) (s) */ 147 static long time_precision = 1; /* clock precision (ns) */ 148 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 149 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 150 static long time_reftime; /* time at last adjustment (s) */ 151 static l_fp time_offset; /* time offset (ns) */ 152 static l_fp time_freq; /* frequency offset (ns/s) */ 153 static l_fp time_adj; /* tick adjust (ns/s) */ 154 155 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 156 157 #ifdef PPS_SYNC 158 /* 159 * The following variables are used when a pulse-per-second (PPS) signal 160 * is available and connected via a modem control lead. They establish 161 * the engineering parameters of the clock discipline loop when 162 * controlled by the PPS signal. 163 */ 164 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 165 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 166 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 167 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 168 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 169 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 170 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 171 172 static struct timespec pps_tf[3]; /* phase median filter */ 173 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 174 static long pps_fcount; /* frequency accumulator */ 175 static long pps_jitter; /* nominal jitter (ns) */ 176 static long pps_stabil; /* nominal stability (scaled ns/s) */ 177 static long pps_lastsec; /* time at last calibration (s) */ 178 static int pps_valid; /* signal watchdog counter */ 179 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 180 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 181 static int pps_intcnt; /* wander counter */ 182 183 /* 184 * PPS signal quality monitors 185 */ 186 static long pps_calcnt; /* calibration intervals */ 187 static long pps_jitcnt; /* jitter limit exceeded */ 188 static long pps_stbcnt; /* stability limit exceeded */ 189 static long pps_errcnt; /* calibration errors */ 190 #endif /* PPS_SYNC */ 191 /* 192 * End of phase/frequency-lock loop (PLL/FLL) definitions 193 */ 194 195 static void ntp_init(void); 196 static void hardupdate(long offset); 197 198 /* 199 * ntp_gettime() - NTP user application interface 200 * 201 * See the timex.h header file for synopsis and API description. Note 202 * that the TAI offset is returned in the ntvtimeval.tai structure 203 * member. 204 */ 205 static int 206 ntp_sysctl(SYSCTL_HANDLER_ARGS) 207 { 208 struct ntptimeval ntv; /* temporary structure */ 209 struct timespec atv; /* nanosecond time */ 210 211 nanotime(&atv); 212 ntv.time.tv_sec = atv.tv_sec; 213 ntv.time.tv_nsec = atv.tv_nsec; 214 ntv.maxerror = time_maxerror; 215 ntv.esterror = time_esterror; 216 ntv.tai = time_tai; 217 ntv.time_state = time_state; 218 219 /* 220 * Status word error decode. If any of these conditions occur, 221 * an error is returned, instead of the status word. Most 222 * applications will care only about the fact the system clock 223 * may not be trusted, not about the details. 224 * 225 * Hardware or software error 226 */ 227 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 228 229 /* 230 * PPS signal lost when either time or frequency synchronization 231 * requested 232 */ 233 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 234 !(time_status & STA_PPSSIGNAL)) || 235 236 /* 237 * PPS jitter exceeded when time synchronization requested 238 */ 239 (time_status & STA_PPSTIME && 240 time_status & STA_PPSJITTER) || 241 242 /* 243 * PPS wander exceeded or calibration error when frequency 244 * synchronization requested 245 */ 246 (time_status & STA_PPSFREQ && 247 time_status & (STA_PPSWANDER | STA_PPSERROR))) 248 ntv.time_state = TIME_ERROR; 249 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 250 } 251 252 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 253 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 254 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 255 256 #ifdef PPS_SYNC 257 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 258 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 259 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 260 261 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 262 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 263 #endif 264 /* 265 * ntp_adjtime() - NTP daemon application interface 266 * 267 * See the timex.h header file for synopsis and API description. Note 268 * that the timex.constant structure member has a dual purpose to set 269 * the time constant and to set the TAI offset. 270 */ 271 #ifndef _SYS_SYSPROTO_H_ 272 struct ntp_adjtime_args { 273 struct timex *tp; 274 }; 275 #endif 276 277 /* 278 * MPSAFE 279 */ 280 int 281 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 282 { 283 struct timex ntv; /* temporary structure */ 284 long freq; /* frequency ns/s) */ 285 int modes; /* mode bits from structure */ 286 int s; /* caller priority */ 287 int error; 288 289 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 290 if (error) 291 return(error); 292 293 /* 294 * Update selected clock variables - only the superuser can 295 * change anything. Note that there is no error checking here on 296 * the assumption the superuser should know what it is doing. 297 * Note that either the time constant or TAI offset are loaded 298 * from the ntv.constant member, depending on the mode bits. If 299 * the STA_PLL bit in the status word is cleared, the state and 300 * status words are reset to the initial values at boot. 301 */ 302 mtx_lock(&Giant); 303 modes = ntv.modes; 304 if (modes) 305 error = suser(td); 306 if (error) 307 goto done2; 308 s = splclock(); 309 if (modes & MOD_MAXERROR) 310 time_maxerror = ntv.maxerror; 311 if (modes & MOD_ESTERROR) 312 time_esterror = ntv.esterror; 313 if (modes & MOD_STATUS) { 314 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 315 time_state = TIME_OK; 316 time_status = STA_UNSYNC; 317 #ifdef PPS_SYNC 318 pps_shift = PPS_FAVG; 319 #endif /* PPS_SYNC */ 320 } 321 time_status &= STA_RONLY; 322 time_status |= ntv.status & ~STA_RONLY; 323 } 324 if (modes & MOD_TIMECONST) { 325 if (ntv.constant < 0) 326 time_constant = 0; 327 else if (ntv.constant > MAXTC) 328 time_constant = MAXTC; 329 else 330 time_constant = ntv.constant; 331 } 332 if (modes & MOD_TAI) { 333 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 334 time_tai = ntv.constant; 335 } 336 #ifdef PPS_SYNC 337 if (modes & MOD_PPSMAX) { 338 if (ntv.shift < PPS_FAVG) 339 pps_shiftmax = PPS_FAVG; 340 else if (ntv.shift > PPS_FAVGMAX) 341 pps_shiftmax = PPS_FAVGMAX; 342 else 343 pps_shiftmax = ntv.shift; 344 } 345 #endif /* PPS_SYNC */ 346 if (modes & MOD_NANO) 347 time_status |= STA_NANO; 348 if (modes & MOD_MICRO) 349 time_status &= ~STA_NANO; 350 if (modes & MOD_CLKB) 351 time_status |= STA_CLK; 352 if (modes & MOD_CLKA) 353 time_status &= ~STA_CLK; 354 if (modes & MOD_OFFSET) { 355 if (time_status & STA_NANO) 356 hardupdate(ntv.offset); 357 else 358 hardupdate(ntv.offset * 1000); 359 } 360 if (modes & MOD_FREQUENCY) { 361 freq = (ntv.freq * 1000LL) >> 16; 362 if (freq > MAXFREQ) 363 L_LINT(time_freq, MAXFREQ); 364 else if (freq < -MAXFREQ) 365 L_LINT(time_freq, -MAXFREQ); 366 else 367 L_LINT(time_freq, freq); 368 #ifdef PPS_SYNC 369 pps_freq = time_freq; 370 #endif /* PPS_SYNC */ 371 } 372 373 /* 374 * Retrieve all clock variables. Note that the TAI offset is 375 * returned only by ntp_gettime(); 376 */ 377 if (time_status & STA_NANO) 378 ntv.offset = L_GINT(time_offset); 379 else 380 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 381 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 382 ntv.maxerror = time_maxerror; 383 ntv.esterror = time_esterror; 384 ntv.status = time_status; 385 ntv.constant = time_constant; 386 if (time_status & STA_NANO) 387 ntv.precision = time_precision; 388 else 389 ntv.precision = time_precision / 1000; 390 ntv.tolerance = MAXFREQ * SCALE_PPM; 391 #ifdef PPS_SYNC 392 ntv.shift = pps_shift; 393 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 394 if (time_status & STA_NANO) 395 ntv.jitter = pps_jitter; 396 else 397 ntv.jitter = pps_jitter / 1000; 398 ntv.stabil = pps_stabil; 399 ntv.calcnt = pps_calcnt; 400 ntv.errcnt = pps_errcnt; 401 ntv.jitcnt = pps_jitcnt; 402 ntv.stbcnt = pps_stbcnt; 403 #endif /* PPS_SYNC */ 404 splx(s); 405 406 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 407 if (error) 408 goto done2; 409 410 /* 411 * Status word error decode. See comments in 412 * ntp_gettime() routine. 413 */ 414 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 415 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 416 !(time_status & STA_PPSSIGNAL)) || 417 (time_status & STA_PPSTIME && 418 time_status & STA_PPSJITTER) || 419 (time_status & STA_PPSFREQ && 420 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 421 td->td_retval[0] = TIME_ERROR; 422 } else { 423 td->td_retval[0] = time_state; 424 } 425 done2: 426 mtx_unlock(&Giant); 427 return (error); 428 } 429 430 /* 431 * second_overflow() - called after ntp_tick_adjust() 432 * 433 * This routine is ordinarily called immediately following the above 434 * routine ntp_tick_adjust(). While these two routines are normally 435 * combined, they are separated here only for the purposes of 436 * simulation. 437 */ 438 void 439 ntp_update_second(int64_t *adjustment, time_t *newsec) 440 { 441 int tickrate; 442 l_fp ftemp; /* 32/64-bit temporary */ 443 444 /* 445 * On rollover of the second both the nanosecond and microsecond 446 * clocks are updated and the state machine cranked as 447 * necessary. The phase adjustment to be used for the next 448 * second is calculated and the maximum error is increased by 449 * the tolerance. 450 */ 451 time_maxerror += MAXFREQ / 1000; 452 453 /* 454 * Leap second processing. If in leap-insert state at 455 * the end of the day, the system clock is set back one 456 * second; if in leap-delete state, the system clock is 457 * set ahead one second. The nano_time() routine or 458 * external clock driver will insure that reported time 459 * is always monotonic. 460 */ 461 switch (time_state) { 462 463 /* 464 * No warning. 465 */ 466 case TIME_OK: 467 if (time_status & STA_INS) 468 time_state = TIME_INS; 469 else if (time_status & STA_DEL) 470 time_state = TIME_DEL; 471 break; 472 473 /* 474 * Insert second 23:59:60 following second 475 * 23:59:59. 476 */ 477 case TIME_INS: 478 if (!(time_status & STA_INS)) 479 time_state = TIME_OK; 480 else if ((*newsec) % 86400 == 0) { 481 (*newsec)--; 482 time_state = TIME_OOP; 483 time_tai++; 484 } 485 break; 486 487 /* 488 * Delete second 23:59:59. 489 */ 490 case TIME_DEL: 491 if (!(time_status & STA_DEL)) 492 time_state = TIME_OK; 493 else if (((*newsec) + 1) % 86400 == 0) { 494 (*newsec)++; 495 time_tai--; 496 time_state = TIME_WAIT; 497 } 498 break; 499 500 /* 501 * Insert second in progress. 502 */ 503 case TIME_OOP: 504 time_state = TIME_WAIT; 505 break; 506 507 /* 508 * Wait for status bits to clear. 509 */ 510 case TIME_WAIT: 511 if (!(time_status & (STA_INS | STA_DEL))) 512 time_state = TIME_OK; 513 } 514 515 /* 516 * Compute the total time adjustment for the next second 517 * in ns. The offset is reduced by a factor depending on 518 * whether the PPS signal is operating. Note that the 519 * value is in effect scaled by the clock frequency, 520 * since the adjustment is added at each tick interrupt. 521 */ 522 ftemp = time_offset; 523 #ifdef PPS_SYNC 524 /* XXX even if PPS signal dies we should finish adjustment ? */ 525 if (time_status & STA_PPSTIME && time_status & 526 STA_PPSSIGNAL) 527 L_RSHIFT(ftemp, pps_shift); 528 else 529 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 530 #else 531 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 532 #endif /* PPS_SYNC */ 533 time_adj = ftemp; 534 L_SUB(time_offset, ftemp); 535 L_ADD(time_adj, time_freq); 536 537 /* 538 * Apply any correction from adjtime(2). If more than one second 539 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM) 540 * until the last second is slewed the final < 500 usecs. 541 */ 542 if (time_adjtime != 0) { 543 if (time_adjtime > 1000000) 544 tickrate = 5000; 545 else if (time_adjtime < -1000000) 546 tickrate = -5000; 547 else if (time_adjtime > 500) 548 tickrate = 500; 549 else if (time_adjtime < -500) 550 tickrate = -500; 551 else if (time_adjtime != 0) 552 tickrate = time_adjtime; 553 else 554 tickrate = 0; /* GCC sucks! */ 555 time_adjtime -= tickrate; 556 L_LINT(ftemp, tickrate * 1000); 557 L_ADD(time_adj, ftemp); 558 } 559 *adjustment = time_adj; 560 561 #ifdef PPS_SYNC 562 if (pps_valid > 0) 563 pps_valid--; 564 else 565 time_status &= ~STA_PPSSIGNAL; 566 #endif /* PPS_SYNC */ 567 } 568 569 /* 570 * ntp_init() - initialize variables and structures 571 * 572 * This routine must be called after the kernel variables hz and tick 573 * are set or changed and before the next tick interrupt. In this 574 * particular implementation, these values are assumed set elsewhere in 575 * the kernel. The design allows the clock frequency and tick interval 576 * to be changed while the system is running. So, this routine should 577 * probably be integrated with the code that does that. 578 */ 579 static void 580 ntp_init() 581 { 582 583 /* 584 * The following variables are initialized only at startup. Only 585 * those structures not cleared by the compiler need to be 586 * initialized, and these only in the simulator. In the actual 587 * kernel, any nonzero values here will quickly evaporate. 588 */ 589 L_CLR(time_offset); 590 L_CLR(time_freq); 591 #ifdef PPS_SYNC 592 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 593 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 594 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 595 pps_fcount = 0; 596 L_CLR(pps_freq); 597 #endif /* PPS_SYNC */ 598 } 599 600 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL) 601 602 /* 603 * hardupdate() - local clock update 604 * 605 * This routine is called by ntp_adjtime() to update the local clock 606 * phase and frequency. The implementation is of an adaptive-parameter, 607 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 608 * time and frequency offset estimates for each call. If the kernel PPS 609 * discipline code is configured (PPS_SYNC), the PPS signal itself 610 * determines the new time offset, instead of the calling argument. 611 * Presumably, calls to ntp_adjtime() occur only when the caller 612 * believes the local clock is valid within some bound (+-128 ms with 613 * NTP). If the caller's time is far different than the PPS time, an 614 * argument will ensue, and it's not clear who will lose. 615 * 616 * For uncompensated quartz crystal oscillators and nominal update 617 * intervals less than 256 s, operation should be in phase-lock mode, 618 * where the loop is disciplined to phase. For update intervals greater 619 * than 1024 s, operation should be in frequency-lock mode, where the 620 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 621 * is selected by the STA_MODE status bit. 622 */ 623 static void 624 hardupdate(offset) 625 long offset; /* clock offset (ns) */ 626 { 627 long mtemp; 628 l_fp ftemp; 629 630 /* 631 * Select how the phase is to be controlled and from which 632 * source. If the PPS signal is present and enabled to 633 * discipline the time, the PPS offset is used; otherwise, the 634 * argument offset is used. 635 */ 636 if (!(time_status & STA_PLL)) 637 return; 638 if (!(time_status & STA_PPSTIME && time_status & 639 STA_PPSSIGNAL)) { 640 if (offset > MAXPHASE) 641 time_monitor = MAXPHASE; 642 else if (offset < -MAXPHASE) 643 time_monitor = -MAXPHASE; 644 else 645 time_monitor = offset; 646 L_LINT(time_offset, time_monitor); 647 } 648 649 /* 650 * Select how the frequency is to be controlled and in which 651 * mode (PLL or FLL). If the PPS signal is present and enabled 652 * to discipline the frequency, the PPS frequency is used; 653 * otherwise, the argument offset is used to compute it. 654 */ 655 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 656 time_reftime = time_second; 657 return; 658 } 659 if (time_status & STA_FREQHOLD || time_reftime == 0) 660 time_reftime = time_second; 661 mtemp = time_second - time_reftime; 662 L_LINT(ftemp, time_monitor); 663 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 664 L_MPY(ftemp, mtemp); 665 L_ADD(time_freq, ftemp); 666 time_status &= ~STA_MODE; 667 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 668 MAXSEC)) { 669 L_LINT(ftemp, (time_monitor << 4) / mtemp); 670 L_RSHIFT(ftemp, SHIFT_FLL + 4); 671 L_ADD(time_freq, ftemp); 672 time_status |= STA_MODE; 673 } 674 time_reftime = time_second; 675 if (L_GINT(time_freq) > MAXFREQ) 676 L_LINT(time_freq, MAXFREQ); 677 else if (L_GINT(time_freq) < -MAXFREQ) 678 L_LINT(time_freq, -MAXFREQ); 679 } 680 681 #ifdef PPS_SYNC 682 /* 683 * hardpps() - discipline CPU clock oscillator to external PPS signal 684 * 685 * This routine is called at each PPS interrupt in order to discipline 686 * the CPU clock oscillator to the PPS signal. There are two independent 687 * first-order feedback loops, one for the phase, the other for the 688 * frequency. The phase loop measures and grooms the PPS phase offset 689 * and leaves it in a handy spot for the seconds overflow routine. The 690 * frequency loop averages successive PPS phase differences and 691 * calculates the PPS frequency offset, which is also processed by the 692 * seconds overflow routine. The code requires the caller to capture the 693 * time and architecture-dependent hardware counter values in 694 * nanoseconds at the on-time PPS signal transition. 695 * 696 * Note that, on some Unix systems this routine runs at an interrupt 697 * priority level higher than the timer interrupt routine hardclock(). 698 * Therefore, the variables used are distinct from the hardclock() 699 * variables, except for the actual time and frequency variables, which 700 * are determined by this routine and updated atomically. 701 */ 702 void 703 hardpps(tsp, nsec) 704 struct timespec *tsp; /* time at PPS */ 705 long nsec; /* hardware counter at PPS */ 706 { 707 long u_sec, u_nsec, v_nsec; /* temps */ 708 l_fp ftemp; 709 710 /* 711 * The signal is first processed by a range gate and frequency 712 * discriminator. The range gate rejects noise spikes outside 713 * the range +-500 us. The frequency discriminator rejects input 714 * signals with apparent frequency outside the range 1 +-500 715 * PPM. If two hits occur in the same second, we ignore the 716 * later hit; if not and a hit occurs outside the range gate, 717 * keep the later hit for later comparison, but do not process 718 * it. 719 */ 720 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 721 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 722 pps_valid = PPS_VALID; 723 u_sec = tsp->tv_sec; 724 u_nsec = tsp->tv_nsec; 725 if (u_nsec >= (NANOSECOND >> 1)) { 726 u_nsec -= NANOSECOND; 727 u_sec++; 728 } 729 v_nsec = u_nsec - pps_tf[0].tv_nsec; 730 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 731 MAXFREQ) 732 return; 733 pps_tf[2] = pps_tf[1]; 734 pps_tf[1] = pps_tf[0]; 735 pps_tf[0].tv_sec = u_sec; 736 pps_tf[0].tv_nsec = u_nsec; 737 738 /* 739 * Compute the difference between the current and previous 740 * counter values. If the difference exceeds 0.5 s, assume it 741 * has wrapped around, so correct 1.0 s. If the result exceeds 742 * the tick interval, the sample point has crossed a tick 743 * boundary during the last second, so correct the tick. Very 744 * intricate. 745 */ 746 u_nsec = nsec; 747 if (u_nsec > (NANOSECOND >> 1)) 748 u_nsec -= NANOSECOND; 749 else if (u_nsec < -(NANOSECOND >> 1)) 750 u_nsec += NANOSECOND; 751 pps_fcount += u_nsec; 752 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 753 return; 754 time_status &= ~STA_PPSJITTER; 755 756 /* 757 * A three-stage median filter is used to help denoise the PPS 758 * time. The median sample becomes the time offset estimate; the 759 * difference between the other two samples becomes the time 760 * dispersion (jitter) estimate. 761 */ 762 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 763 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 764 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 765 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 766 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 767 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 768 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 769 } else { 770 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 771 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 772 } 773 } else { 774 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 775 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 776 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 777 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 778 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 779 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 780 } else { 781 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 782 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 783 } 784 } 785 786 /* 787 * Nominal jitter is due to PPS signal noise and interrupt 788 * latency. If it exceeds the popcorn threshold, the sample is 789 * discarded. otherwise, if so enabled, the time offset is 790 * updated. We can tolerate a modest loss of data here without 791 * much degrading time accuracy. 792 */ 793 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 794 time_status |= STA_PPSJITTER; 795 pps_jitcnt++; 796 } else if (time_status & STA_PPSTIME) { 797 time_monitor = -v_nsec; 798 L_LINT(time_offset, time_monitor); 799 } 800 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 801 u_sec = pps_tf[0].tv_sec - pps_lastsec; 802 if (u_sec < (1 << pps_shift)) 803 return; 804 805 /* 806 * At the end of the calibration interval the difference between 807 * the first and last counter values becomes the scaled 808 * frequency. It will later be divided by the length of the 809 * interval to determine the frequency update. If the frequency 810 * exceeds a sanity threshold, or if the actual calibration 811 * interval is not equal to the expected length, the data are 812 * discarded. We can tolerate a modest loss of data here without 813 * much degrading frequency accuracy. 814 */ 815 pps_calcnt++; 816 v_nsec = -pps_fcount; 817 pps_lastsec = pps_tf[0].tv_sec; 818 pps_fcount = 0; 819 u_nsec = MAXFREQ << pps_shift; 820 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 821 pps_shift)) { 822 time_status |= STA_PPSERROR; 823 pps_errcnt++; 824 return; 825 } 826 827 /* 828 * Here the raw frequency offset and wander (stability) is 829 * calculated. If the wander is less than the wander threshold 830 * for four consecutive averaging intervals, the interval is 831 * doubled; if it is greater than the threshold for four 832 * consecutive intervals, the interval is halved. The scaled 833 * frequency offset is converted to frequency offset. The 834 * stability metric is calculated as the average of recent 835 * frequency changes, but is used only for performance 836 * monitoring. 837 */ 838 L_LINT(ftemp, v_nsec); 839 L_RSHIFT(ftemp, pps_shift); 840 L_SUB(ftemp, pps_freq); 841 u_nsec = L_GINT(ftemp); 842 if (u_nsec > PPS_MAXWANDER) { 843 L_LINT(ftemp, PPS_MAXWANDER); 844 pps_intcnt--; 845 time_status |= STA_PPSWANDER; 846 pps_stbcnt++; 847 } else if (u_nsec < -PPS_MAXWANDER) { 848 L_LINT(ftemp, -PPS_MAXWANDER); 849 pps_intcnt--; 850 time_status |= STA_PPSWANDER; 851 pps_stbcnt++; 852 } else { 853 pps_intcnt++; 854 } 855 if (pps_intcnt >= 4) { 856 pps_intcnt = 4; 857 if (pps_shift < pps_shiftmax) { 858 pps_shift++; 859 pps_intcnt = 0; 860 } 861 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 862 pps_intcnt = -4; 863 if (pps_shift > PPS_FAVG) { 864 pps_shift--; 865 pps_intcnt = 0; 866 } 867 } 868 if (u_nsec < 0) 869 u_nsec = -u_nsec; 870 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 871 872 /* 873 * The PPS frequency is recalculated and clamped to the maximum 874 * MAXFREQ. If enabled, the system clock frequency is updated as 875 * well. 876 */ 877 L_ADD(pps_freq, ftemp); 878 u_nsec = L_GINT(pps_freq); 879 if (u_nsec > MAXFREQ) 880 L_LINT(pps_freq, MAXFREQ); 881 else if (u_nsec < -MAXFREQ) 882 L_LINT(pps_freq, -MAXFREQ); 883 if (time_status & STA_PPSFREQ) 884 time_freq = pps_freq; 885 } 886 #endif /* PPS_SYNC */ 887 888 #ifndef _SYS_SYSPROTO_H_ 889 struct adjtime_args { 890 struct timeval *delta; 891 struct timeval *olddelta; 892 }; 893 #endif 894 /* 895 * MPSAFE 896 */ 897 /* ARGSUSED */ 898 int 899 adjtime(struct thread *td, struct adjtime_args *uap) 900 { 901 struct timeval atv; 902 int error; 903 904 if ((error = suser(td))) 905 return (error); 906 907 mtx_lock(&Giant); 908 if (uap->olddelta) { 909 atv.tv_sec = time_adjtime / 1000000; 910 atv.tv_usec = time_adjtime % 1000000; 911 if (atv.tv_usec < 0) { 912 atv.tv_usec += 1000000; 913 atv.tv_sec--; 914 } 915 error = copyout(&atv, uap->olddelta, sizeof(atv)); 916 if (error) 917 goto done2; 918 } 919 if (uap->delta) { 920 error = copyin(uap->delta, &atv, sizeof(atv)); 921 if (error) 922 goto done2; 923 time_adjtime = (int64_t)atv.tv_sec * 1000000 + atv.tv_usec; 924 } 925 done2: 926 mtx_unlock(&Giant); 927 return (error); 928 } 929
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