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: src/sys/kern/kern_ntptime.c,v 1.54.2.2 2005/04/21 20:33:05 ps Exp $"); 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/syscallsubr.h> 50 #include <sys/sysctl.h> 51 52 /* 53 * Single-precision macros for 64-bit machines 54 */ 55 typedef int64_t l_fp; 56 #define L_ADD(v, u) ((v) += (u)) 57 #define L_SUB(v, u) ((v) -= (u)) 58 #define L_ADDHI(v, a) ((v) += (int64_t)(a) << 32) 59 #define L_NEG(v) ((v) = -(v)) 60 #define L_RSHIFT(v, n) \ 61 do { \ 62 if ((v) < 0) \ 63 (v) = -(-(v) >> (n)); \ 64 else \ 65 (v) = (v) >> (n); \ 66 } while (0) 67 #define L_MPY(v, a) ((v) *= (a)) 68 #define L_CLR(v) ((v) = 0) 69 #define L_ISNEG(v) ((v) < 0) 70 #define L_LINT(v, a) ((v) = (int64_t)(a) << 32) 71 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 72 73 /* 74 * Generic NTP kernel interface 75 * 76 * These routines constitute the Network Time Protocol (NTP) interfaces 77 * for user and daemon application programs. The ntp_gettime() routine 78 * provides the time, maximum error (synch distance) and estimated error 79 * (dispersion) to client user application programs. The ntp_adjtime() 80 * routine is used by the NTP daemon to adjust the system clock to an 81 * externally derived time. The time offset and related variables set by 82 * this routine are used by other routines in this module to adjust the 83 * phase and frequency of the clock discipline loop which controls the 84 * system clock. 85 * 86 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 87 * defined), the time at each tick interrupt is derived directly from 88 * the kernel time variable. When the kernel time is reckoned in 89 * microseconds, (NTP_NANO undefined), the time is derived from the 90 * kernel time variable together with a variable representing the 91 * leftover nanoseconds at the last tick interrupt. In either case, the 92 * current nanosecond time is reckoned from these values plus an 93 * interpolated value derived by the clock routines in another 94 * architecture-specific module. The interpolation can use either a 95 * dedicated counter or a processor cycle counter (PCC) implemented in 96 * some architectures. 97 * 98 * Note that all routines must run at priority splclock or higher. 99 */ 100 /* 101 * Phase/frequency-lock loop (PLL/FLL) definitions 102 * 103 * The nanosecond clock discipline uses two variable types, time 104 * variables and frequency variables. Both types are represented as 64- 105 * bit fixed-point quantities with the decimal point between two 32-bit 106 * halves. On a 32-bit machine, each half is represented as a single 107 * word and mathematical operations are done using multiple-precision 108 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 109 * used. 110 * 111 * A time variable is a signed 64-bit fixed-point number in ns and 112 * fraction. It represents the remaining time offset to be amortized 113 * over succeeding tick interrupts. The maximum time offset is about 114 * 0.5 s and the resolution is about 2.3e-10 ns. 115 * 116 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 117 * 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 1 118 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 119 * |s s s| ns | 120 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 121 * | fraction | 122 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 123 * 124 * A frequency variable is a signed 64-bit fixed-point number in ns/s 125 * and fraction. It represents the ns and fraction to be added to the 126 * kernel time variable at each second. The maximum frequency offset is 127 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 128 * 129 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 130 * 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 1 131 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 132 * |s s s s s s s s s s s s s| ns/s | 133 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 134 * | fraction | 135 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 136 */ 137 /* 138 * The following variables establish the state of the PLL/FLL and the 139 * residual time and frequency offset of the local clock. 140 */ 141 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 142 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 143 144 static int time_state = TIME_OK; /* clock state */ 145 static int time_status = STA_UNSYNC; /* clock status bits */ 146 static long time_tai; /* TAI offset (s) */ 147 static long time_monitor; /* last time offset scaled (ns) */ 148 static long time_constant; /* poll interval (shift) (s) */ 149 static long time_precision = 1; /* clock precision (ns) */ 150 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 151 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 152 static long time_reftime; /* time at last adjustment (s) */ 153 static l_fp time_offset; /* time offset (ns) */ 154 static l_fp time_freq; /* frequency offset (ns/s) */ 155 static l_fp time_adj; /* tick adjust (ns/s) */ 156 157 static int64_t time_adjtime; /* correction from adjtime(2) (usec) */ 158 159 #ifdef PPS_SYNC 160 /* 161 * The following variables are used when a pulse-per-second (PPS) signal 162 * is available and connected via a modem control lead. They establish 163 * the engineering parameters of the clock discipline loop when 164 * controlled by the PPS signal. 165 */ 166 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 167 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 168 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 169 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 170 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 171 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 172 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 173 174 static struct timespec pps_tf[3]; /* phase median filter */ 175 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 176 static long pps_fcount; /* frequency accumulator */ 177 static long pps_jitter; /* nominal jitter (ns) */ 178 static long pps_stabil; /* nominal stability (scaled ns/s) */ 179 static long pps_lastsec; /* time at last calibration (s) */ 180 static int pps_valid; /* signal watchdog counter */ 181 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 182 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 183 static int pps_intcnt; /* wander counter */ 184 185 /* 186 * PPS signal quality monitors 187 */ 188 static long pps_calcnt; /* calibration intervals */ 189 static long pps_jitcnt; /* jitter limit exceeded */ 190 static long pps_stbcnt; /* stability limit exceeded */ 191 static long pps_errcnt; /* calibration errors */ 192 #endif /* PPS_SYNC */ 193 /* 194 * End of phase/frequency-lock loop (PLL/FLL) definitions 195 */ 196 197 static void ntp_init(void); 198 static void hardupdate(long offset); 199 200 /* 201 * ntp_gettime() - NTP user application interface 202 * 203 * See the timex.h header file for synopsis and API description. Note 204 * that the TAI offset is returned in the ntvtimeval.tai structure 205 * member. 206 */ 207 static int 208 ntp_sysctl(SYSCTL_HANDLER_ARGS) 209 { 210 struct ntptimeval ntv; /* temporary structure */ 211 struct timespec atv; /* nanosecond time */ 212 213 nanotime(&atv); 214 ntv.time.tv_sec = atv.tv_sec; 215 ntv.time.tv_nsec = atv.tv_nsec; 216 ntv.maxerror = time_maxerror; 217 ntv.esterror = time_esterror; 218 ntv.tai = time_tai; 219 ntv.time_state = time_state; 220 221 /* 222 * Status word error decode. If any of these conditions occur, 223 * an error is returned, instead of the status word. Most 224 * applications will care only about the fact the system clock 225 * may not be trusted, not about the details. 226 * 227 * Hardware or software error 228 */ 229 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 230 231 /* 232 * PPS signal lost when either time or frequency synchronization 233 * requested 234 */ 235 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 236 !(time_status & STA_PPSSIGNAL)) || 237 238 /* 239 * PPS jitter exceeded when time synchronization requested 240 */ 241 (time_status & STA_PPSTIME && 242 time_status & STA_PPSJITTER) || 243 244 /* 245 * PPS wander exceeded or calibration error when frequency 246 * synchronization requested 247 */ 248 (time_status & STA_PPSFREQ && 249 time_status & (STA_PPSWANDER | STA_PPSERROR))) 250 ntv.time_state = TIME_ERROR; 251 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 252 } 253 254 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 255 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 256 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 257 258 #ifdef PPS_SYNC 259 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 260 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 261 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 262 263 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 264 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 265 #endif 266 /* 267 * ntp_adjtime() - NTP daemon application interface 268 * 269 * See the timex.h header file for synopsis and API description. Note 270 * that the timex.constant structure member has a dual purpose to set 271 * the time constant and to set the TAI offset. 272 */ 273 #ifndef _SYS_SYSPROTO_H_ 274 struct ntp_adjtime_args { 275 struct timex *tp; 276 }; 277 #endif 278 279 /* 280 * MPSAFE 281 */ 282 int 283 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap) 284 { 285 struct timex ntv; /* temporary structure */ 286 long freq; /* frequency ns/s) */ 287 int modes; /* mode bits from structure */ 288 int s; /* caller priority */ 289 int error; 290 291 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 292 if (error) 293 return(error); 294 295 /* 296 * Update selected clock variables - only the superuser can 297 * change anything. Note that there is no error checking here on 298 * the assumption the superuser should know what it is doing. 299 * Note that either the time constant or TAI offset are loaded 300 * from the ntv.constant member, depending on the mode bits. If 301 * the STA_PLL bit in the status word is cleared, the state and 302 * status words are reset to the initial values at boot. 303 */ 304 mtx_lock(&Giant); 305 modes = ntv.modes; 306 if (modes) 307 error = suser(td); 308 if (error) 309 goto done2; 310 s = splclock(); 311 if (modes & MOD_MAXERROR) 312 time_maxerror = ntv.maxerror; 313 if (modes & MOD_ESTERROR) 314 time_esterror = ntv.esterror; 315 if (modes & MOD_STATUS) { 316 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 317 time_state = TIME_OK; 318 time_status = STA_UNSYNC; 319 #ifdef PPS_SYNC 320 pps_shift = PPS_FAVG; 321 #endif /* PPS_SYNC */ 322 } 323 time_status &= STA_RONLY; 324 time_status |= ntv.status & ~STA_RONLY; 325 } 326 if (modes & MOD_TIMECONST) { 327 if (ntv.constant < 0) 328 time_constant = 0; 329 else if (ntv.constant > MAXTC) 330 time_constant = MAXTC; 331 else 332 time_constant = ntv.constant; 333 } 334 if (modes & MOD_TAI) { 335 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 336 time_tai = ntv.constant; 337 } 338 #ifdef PPS_SYNC 339 if (modes & MOD_PPSMAX) { 340 if (ntv.shift < PPS_FAVG) 341 pps_shiftmax = PPS_FAVG; 342 else if (ntv.shift > PPS_FAVGMAX) 343 pps_shiftmax = PPS_FAVGMAX; 344 else 345 pps_shiftmax = ntv.shift; 346 } 347 #endif /* PPS_SYNC */ 348 if (modes & MOD_NANO) 349 time_status |= STA_NANO; 350 if (modes & MOD_MICRO) 351 time_status &= ~STA_NANO; 352 if (modes & MOD_CLKB) 353 time_status |= STA_CLK; 354 if (modes & MOD_CLKA) 355 time_status &= ~STA_CLK; 356 if (modes & MOD_FREQUENCY) { 357 freq = (ntv.freq * 1000LL) >> 16; 358 if (freq > MAXFREQ) 359 L_LINT(time_freq, MAXFREQ); 360 else if (freq < -MAXFREQ) 361 L_LINT(time_freq, -MAXFREQ); 362 else { 363 /* 364 * ntv.freq is [PPM * 2^16] = [us/s * 2^16] 365 * time_freq is [ns/s * 2^32] 366 */ 367 time_freq = ntv.freq * 1000LL * 65536LL; 368 } 369 #ifdef PPS_SYNC 370 pps_freq = time_freq; 371 #endif /* PPS_SYNC */ 372 } 373 if (modes & MOD_OFFSET) { 374 if (time_status & STA_NANO) 375 hardupdate(ntv.offset); 376 else 377 hardupdate(ntv.offset * 1000); 378 } 379 380 /* 381 * Retrieve all clock variables. Note that the TAI offset is 382 * returned only by ntp_gettime(); 383 */ 384 if (time_status & STA_NANO) 385 ntv.offset = L_GINT(time_offset); 386 else 387 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */ 388 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 389 ntv.maxerror = time_maxerror; 390 ntv.esterror = time_esterror; 391 ntv.status = time_status; 392 ntv.constant = time_constant; 393 if (time_status & STA_NANO) 394 ntv.precision = time_precision; 395 else 396 ntv.precision = time_precision / 1000; 397 ntv.tolerance = MAXFREQ * SCALE_PPM; 398 #ifdef PPS_SYNC 399 ntv.shift = pps_shift; 400 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 401 if (time_status & STA_NANO) 402 ntv.jitter = pps_jitter; 403 else 404 ntv.jitter = pps_jitter / 1000; 405 ntv.stabil = pps_stabil; 406 ntv.calcnt = pps_calcnt; 407 ntv.errcnt = pps_errcnt; 408 ntv.jitcnt = pps_jitcnt; 409 ntv.stbcnt = pps_stbcnt; 410 #endif /* PPS_SYNC */ 411 splx(s); 412 413 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 414 if (error) 415 goto done2; 416 417 /* 418 * Status word error decode. See comments in 419 * ntp_gettime() routine. 420 */ 421 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 422 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 423 !(time_status & STA_PPSSIGNAL)) || 424 (time_status & STA_PPSTIME && 425 time_status & STA_PPSJITTER) || 426 (time_status & STA_PPSFREQ && 427 time_status & (STA_PPSWANDER | STA_PPSERROR))) { 428 td->td_retval[0] = TIME_ERROR; 429 } else { 430 td->td_retval[0] = time_state; 431 } 432 done2: 433 mtx_unlock(&Giant); 434 return (error); 435 } 436 437 /* 438 * second_overflow() - called after ntp_tick_adjust() 439 * 440 * This routine is ordinarily called immediately following the above 441 * routine ntp_tick_adjust(). While these two routines are normally 442 * combined, they are separated here only for the purposes of 443 * simulation. 444 */ 445 void 446 ntp_update_second(int64_t *adjustment, time_t *newsec) 447 { 448 int tickrate; 449 l_fp ftemp; /* 32/64-bit temporary */ 450 451 /* 452 * On rollover of the second both the nanosecond and microsecond 453 * clocks are updated and the state machine cranked as 454 * necessary. The phase adjustment to be used for the next 455 * second is calculated and the maximum error is increased by 456 * the tolerance. 457 */ 458 time_maxerror += MAXFREQ / 1000; 459 460 /* 461 * Leap second processing. If in leap-insert state at 462 * the end of the day, the system clock is set back one 463 * second; if in leap-delete state, the system clock is 464 * set ahead one second. The nano_time() routine or 465 * external clock driver will insure that reported time 466 * is always monotonic. 467 */ 468 switch (time_state) { 469 470 /* 471 * No warning. 472 */ 473 case TIME_OK: 474 if (time_status & STA_INS) 475 time_state = TIME_INS; 476 else if (time_status & STA_DEL) 477 time_state = TIME_DEL; 478 break; 479 480 /* 481 * Insert second 23:59:60 following second 482 * 23:59:59. 483 */ 484 case TIME_INS: 485 if (!(time_status & STA_INS)) 486 time_state = TIME_OK; 487 else if ((*newsec) % 86400 == 0) { 488 (*newsec)--; 489 time_state = TIME_OOP; 490 time_tai++; 491 } 492 break; 493 494 /* 495 * Delete second 23:59:59. 496 */ 497 case TIME_DEL: 498 if (!(time_status & STA_DEL)) 499 time_state = TIME_OK; 500 else if (((*newsec) + 1) % 86400 == 0) { 501 (*newsec)++; 502 time_tai--; 503 time_state = TIME_WAIT; 504 } 505 break; 506 507 /* 508 * Insert second in progress. 509 */ 510 case TIME_OOP: 511 time_state = TIME_WAIT; 512 break; 513 514 /* 515 * Wait for status bits to clear. 516 */ 517 case TIME_WAIT: 518 if (!(time_status & (STA_INS | STA_DEL))) 519 time_state = TIME_OK; 520 } 521 522 /* 523 * Compute the total time adjustment for the next second 524 * in ns. The offset is reduced by a factor depending on 525 * whether the PPS signal is operating. Note that the 526 * value is in effect scaled by the clock frequency, 527 * since the adjustment is added at each tick interrupt. 528 */ 529 ftemp = time_offset; 530 #ifdef PPS_SYNC 531 /* XXX even if PPS signal dies we should finish adjustment ? */ 532 if (time_status & STA_PPSTIME && time_status & 533 STA_PPSSIGNAL) 534 L_RSHIFT(ftemp, pps_shift); 535 else 536 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 537 #else 538 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 539 #endif /* PPS_SYNC */ 540 time_adj = ftemp; 541 L_SUB(time_offset, ftemp); 542 L_ADD(time_adj, time_freq); 543 544 /* 545 * Apply any correction from adjtime(2). If more than one second 546 * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM) 547 * until the last second is slewed the final < 500 usecs. 548 */ 549 if (time_adjtime != 0) { 550 if (time_adjtime > 1000000) 551 tickrate = 5000; 552 else if (time_adjtime < -1000000) 553 tickrate = -5000; 554 else if (time_adjtime > 500) 555 tickrate = 500; 556 else if (time_adjtime < -500) 557 tickrate = -500; 558 else 559 tickrate = time_adjtime; 560 time_adjtime -= tickrate; 561 L_LINT(ftemp, tickrate * 1000); 562 L_ADD(time_adj, ftemp); 563 } 564 *adjustment = time_adj; 565 566 #ifdef PPS_SYNC 567 if (pps_valid > 0) 568 pps_valid--; 569 else 570 time_status &= ~STA_PPSSIGNAL; 571 #endif /* PPS_SYNC */ 572 } 573 574 /* 575 * ntp_init() - initialize variables and structures 576 * 577 * This routine must be called after the kernel variables hz and tick 578 * are set or changed and before the next tick interrupt. In this 579 * particular implementation, these values are assumed set elsewhere in 580 * the kernel. The design allows the clock frequency and tick interval 581 * to be changed while the system is running. So, this routine should 582 * probably be integrated with the code that does that. 583 */ 584 static void 585 ntp_init() 586 { 587 588 /* 589 * The following variables are initialized only at startup. Only 590 * those structures not cleared by the compiler need to be 591 * initialized, and these only in the simulator. In the actual 592 * kernel, any nonzero values here will quickly evaporate. 593 */ 594 L_CLR(time_offset); 595 L_CLR(time_freq); 596 #ifdef PPS_SYNC 597 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 598 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 599 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 600 pps_fcount = 0; 601 L_CLR(pps_freq); 602 #endif /* PPS_SYNC */ 603 } 604 605 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL) 606 607 /* 608 * hardupdate() - local clock update 609 * 610 * This routine is called by ntp_adjtime() to update the local clock 611 * phase and frequency. The implementation is of an adaptive-parameter, 612 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 613 * time and frequency offset estimates for each call. If the kernel PPS 614 * discipline code is configured (PPS_SYNC), the PPS signal itself 615 * determines the new time offset, instead of the calling argument. 616 * Presumably, calls to ntp_adjtime() occur only when the caller 617 * believes the local clock is valid within some bound (+-128 ms with 618 * NTP). If the caller's time is far different than the PPS time, an 619 * argument will ensue, and it's not clear who will lose. 620 * 621 * For uncompensated quartz crystal oscillators and nominal update 622 * intervals less than 256 s, operation should be in phase-lock mode, 623 * where the loop is disciplined to phase. For update intervals greater 624 * than 1024 s, operation should be in frequency-lock mode, where the 625 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 626 * is selected by the STA_MODE status bit. 627 */ 628 static void 629 hardupdate(offset) 630 long offset; /* clock offset (ns) */ 631 { 632 long mtemp; 633 l_fp ftemp; 634 635 /* 636 * Select how the phase is to be controlled and from which 637 * source. If the PPS signal is present and enabled to 638 * discipline the time, the PPS offset is used; otherwise, the 639 * argument offset is used. 640 */ 641 if (!(time_status & STA_PLL)) 642 return; 643 if (!(time_status & STA_PPSTIME && time_status & 644 STA_PPSSIGNAL)) { 645 if (offset > MAXPHASE) 646 time_monitor = MAXPHASE; 647 else if (offset < -MAXPHASE) 648 time_monitor = -MAXPHASE; 649 else 650 time_monitor = offset; 651 L_LINT(time_offset, time_monitor); 652 } 653 654 /* 655 * Select how the frequency is to be controlled and in which 656 * mode (PLL or FLL). If the PPS signal is present and enabled 657 * to discipline the frequency, the PPS frequency is used; 658 * otherwise, the argument offset is used to compute it. 659 */ 660 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 661 time_reftime = time_second; 662 return; 663 } 664 if (time_status & STA_FREQHOLD || time_reftime == 0) 665 time_reftime = time_second; 666 mtemp = time_second - time_reftime; 667 L_LINT(ftemp, time_monitor); 668 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 669 L_MPY(ftemp, mtemp); 670 L_ADD(time_freq, ftemp); 671 time_status &= ~STA_MODE; 672 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 673 MAXSEC)) { 674 L_LINT(ftemp, (time_monitor << 4) / mtemp); 675 L_RSHIFT(ftemp, SHIFT_FLL + 4); 676 L_ADD(time_freq, ftemp); 677 time_status |= STA_MODE; 678 } 679 time_reftime = time_second; 680 if (L_GINT(time_freq) > MAXFREQ) 681 L_LINT(time_freq, MAXFREQ); 682 else if (L_GINT(time_freq) < -MAXFREQ) 683 L_LINT(time_freq, -MAXFREQ); 684 } 685 686 #ifdef PPS_SYNC 687 /* 688 * hardpps() - discipline CPU clock oscillator to external PPS signal 689 * 690 * This routine is called at each PPS interrupt in order to discipline 691 * the CPU clock oscillator to the PPS signal. There are two independent 692 * first-order feedback loops, one for the phase, the other for the 693 * frequency. The phase loop measures and grooms the PPS phase offset 694 * and leaves it in a handy spot for the seconds overflow routine. The 695 * frequency loop averages successive PPS phase differences and 696 * calculates the PPS frequency offset, which is also processed by the 697 * seconds overflow routine. The code requires the caller to capture the 698 * time and architecture-dependent hardware counter values in 699 * nanoseconds at the on-time PPS signal transition. 700 * 701 * Note that, on some Unix systems this routine runs at an interrupt 702 * priority level higher than the timer interrupt routine hardclock(). 703 * Therefore, the variables used are distinct from the hardclock() 704 * variables, except for the actual time and frequency variables, which 705 * are determined by this routine and updated atomically. 706 */ 707 void 708 hardpps(tsp, nsec) 709 struct timespec *tsp; /* time at PPS */ 710 long nsec; /* hardware counter at PPS */ 711 { 712 long u_sec, u_nsec, v_nsec; /* temps */ 713 l_fp ftemp; 714 715 /* 716 * The signal is first processed by a range gate and frequency 717 * discriminator. The range gate rejects noise spikes outside 718 * the range +-500 us. The frequency discriminator rejects input 719 * signals with apparent frequency outside the range 1 +-500 720 * PPM. If two hits occur in the same second, we ignore the 721 * later hit; if not and a hit occurs outside the range gate, 722 * keep the later hit for later comparison, but do not process 723 * it. 724 */ 725 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 726 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 727 pps_valid = PPS_VALID; 728 u_sec = tsp->tv_sec; 729 u_nsec = tsp->tv_nsec; 730 if (u_nsec >= (NANOSECOND >> 1)) { 731 u_nsec -= NANOSECOND; 732 u_sec++; 733 } 734 v_nsec = u_nsec - pps_tf[0].tv_nsec; 735 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 736 MAXFREQ) 737 return; 738 pps_tf[2] = pps_tf[1]; 739 pps_tf[1] = pps_tf[0]; 740 pps_tf[0].tv_sec = u_sec; 741 pps_tf[0].tv_nsec = u_nsec; 742 743 /* 744 * Compute the difference between the current and previous 745 * counter values. If the difference exceeds 0.5 s, assume it 746 * has wrapped around, so correct 1.0 s. If the result exceeds 747 * the tick interval, the sample point has crossed a tick 748 * boundary during the last second, so correct the tick. Very 749 * intricate. 750 */ 751 u_nsec = nsec; 752 if (u_nsec > (NANOSECOND >> 1)) 753 u_nsec -= NANOSECOND; 754 else if (u_nsec < -(NANOSECOND >> 1)) 755 u_nsec += NANOSECOND; 756 pps_fcount += u_nsec; 757 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 758 return; 759 time_status &= ~STA_PPSJITTER; 760 761 /* 762 * A three-stage median filter is used to help denoise the PPS 763 * time. The median sample becomes the time offset estimate; the 764 * difference between the other two samples becomes the time 765 * dispersion (jitter) estimate. 766 */ 767 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 768 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 769 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 770 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 771 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 772 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 773 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 774 } else { 775 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 776 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 777 } 778 } else { 779 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 780 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 781 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 782 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 783 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 784 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 785 } else { 786 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 787 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 788 } 789 } 790 791 /* 792 * Nominal jitter is due to PPS signal noise and interrupt 793 * latency. If it exceeds the popcorn threshold, the sample is 794 * discarded. otherwise, if so enabled, the time offset is 795 * updated. We can tolerate a modest loss of data here without 796 * much degrading time accuracy. 797 */ 798 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 799 time_status |= STA_PPSJITTER; 800 pps_jitcnt++; 801 } else if (time_status & STA_PPSTIME) { 802 time_monitor = -v_nsec; 803 L_LINT(time_offset, time_monitor); 804 } 805 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 806 u_sec = pps_tf[0].tv_sec - pps_lastsec; 807 if (u_sec < (1 << pps_shift)) 808 return; 809 810 /* 811 * At the end of the calibration interval the difference between 812 * the first and last counter values becomes the scaled 813 * frequency. It will later be divided by the length of the 814 * interval to determine the frequency update. If the frequency 815 * exceeds a sanity threshold, or if the actual calibration 816 * interval is not equal to the expected length, the data are 817 * discarded. We can tolerate a modest loss of data here without 818 * much degrading frequency accuracy. 819 */ 820 pps_calcnt++; 821 v_nsec = -pps_fcount; 822 pps_lastsec = pps_tf[0].tv_sec; 823 pps_fcount = 0; 824 u_nsec = MAXFREQ << pps_shift; 825 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 826 pps_shift)) { 827 time_status |= STA_PPSERROR; 828 pps_errcnt++; 829 return; 830 } 831 832 /* 833 * Here the raw frequency offset and wander (stability) is 834 * calculated. If the wander is less than the wander threshold 835 * for four consecutive averaging intervals, the interval is 836 * doubled; if it is greater than the threshold for four 837 * consecutive intervals, the interval is halved. The scaled 838 * frequency offset is converted to frequency offset. The 839 * stability metric is calculated as the average of recent 840 * frequency changes, but is used only for performance 841 * monitoring. 842 */ 843 L_LINT(ftemp, v_nsec); 844 L_RSHIFT(ftemp, pps_shift); 845 L_SUB(ftemp, pps_freq); 846 u_nsec = L_GINT(ftemp); 847 if (u_nsec > PPS_MAXWANDER) { 848 L_LINT(ftemp, PPS_MAXWANDER); 849 pps_intcnt--; 850 time_status |= STA_PPSWANDER; 851 pps_stbcnt++; 852 } else if (u_nsec < -PPS_MAXWANDER) { 853 L_LINT(ftemp, -PPS_MAXWANDER); 854 pps_intcnt--; 855 time_status |= STA_PPSWANDER; 856 pps_stbcnt++; 857 } else { 858 pps_intcnt++; 859 } 860 if (pps_intcnt >= 4) { 861 pps_intcnt = 4; 862 if (pps_shift < pps_shiftmax) { 863 pps_shift++; 864 pps_intcnt = 0; 865 } 866 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 867 pps_intcnt = -4; 868 if (pps_shift > PPS_FAVG) { 869 pps_shift--; 870 pps_intcnt = 0; 871 } 872 } 873 if (u_nsec < 0) 874 u_nsec = -u_nsec; 875 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 876 877 /* 878 * The PPS frequency is recalculated and clamped to the maximum 879 * MAXFREQ. If enabled, the system clock frequency is updated as 880 * well. 881 */ 882 L_ADD(pps_freq, ftemp); 883 u_nsec = L_GINT(pps_freq); 884 if (u_nsec > MAXFREQ) 885 L_LINT(pps_freq, MAXFREQ); 886 else if (u_nsec < -MAXFREQ) 887 L_LINT(pps_freq, -MAXFREQ); 888 if (time_status & STA_PPSFREQ) 889 time_freq = pps_freq; 890 } 891 #endif /* PPS_SYNC */ 892 893 #ifndef _SYS_SYSPROTO_H_ 894 struct adjtime_args { 895 struct timeval *delta; 896 struct timeval *olddelta; 897 }; 898 #endif 899 /* 900 * MPSAFE 901 */ 902 /* ARGSUSED */ 903 int 904 adjtime(struct thread *td, struct adjtime_args *uap) 905 { 906 struct timeval delta, olddelta, *deltap; 907 int error; 908 909 if (uap->delta) { 910 error = copyin(uap->delta, &delta, sizeof(delta)); 911 if (error) 912 return (error); 913 deltap = δ 914 } else 915 deltap = NULL; 916 error = kern_adjtime(td, deltap, &olddelta); 917 if (uap->olddelta && error == 0) 918 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta)); 919 return (error); 920 } 921 922 int 923 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta) 924 { 925 struct timeval atv; 926 int error; 927 928 if ((error = suser(td))) 929 return (error); 930 931 mtx_lock(&Giant); 932 if (olddelta) { 933 atv.tv_sec = time_adjtime / 1000000; 934 atv.tv_usec = time_adjtime % 1000000; 935 if (atv.tv_usec < 0) { 936 atv.tv_usec += 1000000; 937 atv.tv_sec--; 938 } 939 *olddelta = atv; 940 } 941 if (delta) 942 time_adjtime = (int64_t)delta->tv_sec * 1000000 + 943 delta->tv_usec; 944 mtx_unlock(&Giant); 945 return (error); 946 } 947
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