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: src/sys/kern/kern_ntptime.c,v 1.32.2.2 2001/04/22 11:19:46 jhay Exp $ 32 * $DragonFly: src/sys/kern/kern_ntptime.c,v 1.13 2007/04/30 07:18:53 dillon Exp $ 33 */ 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/priv.h> 43 #include <sys/time.h> 44 #include <sys/timex.h> 45 #include <sys/timepps.h> 46 #include <sys/sysctl.h> 47 48 #include <sys/thread2.h> 49 #include <sys/mplock2.h> 50 51 /* 52 * Single-precision macros for 64-bit machines 53 */ 54 typedef long long l_fp; 55 #define L_ADD(v, u) ((v) += (u)) 56 #define L_SUB(v, u) ((v) -= (u)) 57 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 58 #define L_NEG(v) ((v) = -(v)) 59 #define L_RSHIFT(v, n) \ 60 do { \ 61 if ((v) < 0) \ 62 (v) = -(-(v) >> (n)); \ 63 else \ 64 (v) = (v) >> (n); \ 65 } while (0) 66 #define L_MPY(v, a) ((v) *= (a)) 67 #define L_CLR(v) ((v) = 0) 68 #define L_ISNEG(v) ((v) < 0) 69 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 70 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 71 72 /* 73 * Generic NTP kernel interface 74 * 75 * These routines constitute the Network Time Protocol (NTP) interfaces 76 * for user and daemon application programs. The ntp_gettime() routine 77 * provides the time, maximum error (synch distance) and estimated error 78 * (dispersion) to client user application programs. The ntp_adjtime() 79 * routine is used by the NTP daemon to adjust the system clock to an 80 * externally derived time. The time offset and related variables set by 81 * this routine are used by other routines in this module to adjust the 82 * phase and frequency of the clock discipline loop which controls the 83 * system clock. 84 * 85 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 86 * defined), the time at each tick interrupt is derived directly from 87 * the kernel time variable. When the kernel time is reckoned in 88 * microseconds, (NTP_NANO undefined), the time is derived from the 89 * kernel time variable together with a variable representing the 90 * leftover nanoseconds at the last tick interrupt. In either case, the 91 * current nanosecond time is reckoned from these values plus an 92 * interpolated value derived by the clock routines in another 93 * architecture-specific module. The interpolation can use either a 94 * dedicated counter or a processor cycle counter (PCC) implemented in 95 * some architectures. 96 * 97 * Note that all routines must run at priority splclock or higher. 98 */ 99 /* 100 * Phase/frequency-lock loop (PLL/FLL) definitions 101 * 102 * The nanosecond clock discipline uses two variable types, time 103 * variables and frequency variables. Both types are represented as 64- 104 * bit fixed-point quantities with the decimal point between two 32-bit 105 * halves. On a 32-bit machine, each half is represented as a single 106 * word and mathematical operations are done using multiple-precision 107 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 108 * used. 109 * 110 * A time variable is a signed 64-bit fixed-point number in ns and 111 * fraction. It represents the remaining time offset to be amortized 112 * over succeeding tick interrupts. The maximum time offset is about 113 * 0.5 s and the resolution is about 2.3e-10 ns. 114 * 115 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 116 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 * |s s s| ns | 119 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 120 * | fraction | 121 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 122 * 123 * A frequency variable is a signed 64-bit fixed-point number in ns/s 124 * and fraction. It represents the ns and fraction to be added to the 125 * kernel time variable at each second. The maximum frequency offset is 126 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 127 * 128 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 129 * 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 * |s s s s s s s s s s s s s| ns/s | 132 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 133 * | fraction | 134 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 135 */ 136 /* 137 * The following variables establish the state of the PLL/FLL and the 138 * residual time and frequency offset of the local clock. 139 */ 140 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 141 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 142 143 static int time_state = TIME_OK; /* clock state */ 144 static int time_status = STA_UNSYNC; /* clock status bits */ 145 static long time_tai; /* TAI offset (s) */ 146 static long time_monitor; /* last time offset scaled (ns) */ 147 static long time_constant; /* poll interval (shift) (s) */ 148 static long time_precision = 1; /* clock precision (ns) */ 149 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 150 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 151 static long time_reftime; /* time at last adjustment (s) */ 152 static long time_tick; /* nanoseconds per tick (ns) */ 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 #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 * MPALMOSTSAFE 272 */ 273 int 274 sys_ntp_adjtime(struct ntp_adjtime_args *uap) 275 { 276 struct thread *td = curthread; 277 struct timex ntv; /* temporary structure */ 278 long freq; /* frequency ns/s) */ 279 int modes; /* mode bits from structure */ 280 int error; 281 282 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 283 if (error) 284 return(error); 285 286 /* 287 * Update selected clock variables - only the superuser can 288 * change anything. Note that there is no error checking here on 289 * the assumption the superuser should know what it is doing. 290 * Note that either the time constant or TAI offset are loaded 291 * from the ntv.constant member, depending on the mode bits. If 292 * the STA_PLL bit in the status word is cleared, the state and 293 * status words are reset to the initial values at boot. 294 */ 295 modes = ntv.modes; 296 if (modes) 297 error = priv_check(td, PRIV_NTP_ADJTIME); 298 if (error) 299 return (error); 300 301 get_mplock(); 302 crit_enter(); 303 if (modes & MOD_MAXERROR) 304 time_maxerror = ntv.maxerror; 305 if (modes & MOD_ESTERROR) 306 time_esterror = ntv.esterror; 307 if (modes & MOD_STATUS) { 308 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 309 time_state = TIME_OK; 310 time_status = STA_UNSYNC; 311 #ifdef PPS_SYNC 312 pps_shift = PPS_FAVG; 313 #endif /* PPS_SYNC */ 314 } 315 time_status &= STA_RONLY; 316 time_status |= ntv.status & ~STA_RONLY; 317 } 318 if (modes & MOD_TIMECONST) { 319 if (ntv.constant < 0) 320 time_constant = 0; 321 else if (ntv.constant > MAXTC) 322 time_constant = MAXTC; 323 else 324 time_constant = ntv.constant; 325 } 326 if (modes & MOD_TAI) { 327 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 328 time_tai = ntv.constant; 329 } 330 #ifdef PPS_SYNC 331 if (modes & MOD_PPSMAX) { 332 if (ntv.shift < PPS_FAVG) 333 pps_shiftmax = PPS_FAVG; 334 else if (ntv.shift > PPS_FAVGMAX) 335 pps_shiftmax = PPS_FAVGMAX; 336 else 337 pps_shiftmax = ntv.shift; 338 } 339 #endif /* PPS_SYNC */ 340 if (modes & MOD_NANO) 341 time_status |= STA_NANO; 342 if (modes & MOD_MICRO) 343 time_status &= ~STA_NANO; 344 if (modes & MOD_CLKB) 345 time_status |= STA_CLK; 346 if (modes & MOD_CLKA) 347 time_status &= ~STA_CLK; 348 if (modes & MOD_OFFSET) { 349 if (time_status & STA_NANO) 350 hardupdate(ntv.offset); 351 else 352 hardupdate(ntv.offset * 1000); 353 } 354 /* 355 * Note: the userland specified frequency is in seconds per second 356 * times 65536e+6. Multiply by a thousand and divide by 65336 to 357 * get nanoseconds. 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 = time_monitor; 378 else 379 ntv.offset = time_monitor / 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 crit_exit(); 404 rel_mplock(); 405 406 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 407 if (error) 408 return (error); 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 uap->sysmsg_result = TIME_ERROR; 422 } else { 423 uap->sysmsg_result = time_state; 424 } 425 return (error); 426 } 427 428 /* 429 * second_overflow() - called after ntp_tick_adjust() 430 * 431 * This routine is ordinarily called from hardclock() whenever the seconds 432 * hand rolls over. It returns leap seconds to add or drop, and sets nsec_adj 433 * to the total adjustment to make over the next second in (ns << 32). 434 * 435 * This routine is only called by cpu #0. 436 */ 437 int 438 ntp_update_second(time_t newsec, int64_t *nsec_adj) 439 { 440 l_fp ftemp; /* 32/64-bit temporary */ 441 int adjsec = 0; 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 --adjsec; 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 ++adjsec; 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 * time_offset represents the total time adjustment we wish to 516 * make (over no particular period of time). time_freq represents 517 * the frequency compensation we wish to apply. 518 * 519 * time_adj represents the total adjustment we wish to make over 520 * one full second. hardclock usually applies this adjustment in 521 * time_adj / hz jumps, hz times a second. 522 */ 523 ftemp = time_offset; 524 #ifdef PPS_SYNC 525 /* XXX even if PPS signal dies we should finish adjustment ? */ 526 if ((time_status & STA_PPSTIME) && (time_status & 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; /* adjustment for part of the offset */ 534 L_SUB(time_offset, ftemp); 535 L_ADD(time_adj, time_freq); /* add frequency correction */ 536 *nsec_adj = time_adj; 537 #ifdef PPS_SYNC 538 if (pps_valid > 0) 539 pps_valid--; 540 else 541 time_status &= ~STA_PPSSIGNAL; 542 #endif /* PPS_SYNC */ 543 return(adjsec); 544 } 545 546 /* 547 * ntp_init() - initialize variables and structures 548 * 549 * This routine must be called after the kernel variables hz and tick 550 * are set or changed and before the next tick interrupt. In this 551 * particular implementation, these values are assumed set elsewhere in 552 * the kernel. The design allows the clock frequency and tick interval 553 * to be changed while the system is running. So, this routine should 554 * probably be integrated with the code that does that. 555 */ 556 static void 557 ntp_init(void) 558 { 559 560 /* 561 * The following variable must be initialized any time the 562 * kernel variable hz is changed. 563 */ 564 time_tick = NANOSECOND / hz; 565 566 /* 567 * The following variables are initialized only at startup. Only 568 * those structures not cleared by the compiler need to be 569 * initialized, and these only in the simulator. In the actual 570 * kernel, any nonzero values here will quickly evaporate. 571 */ 572 L_CLR(time_offset); 573 L_CLR(time_freq); 574 #ifdef PPS_SYNC 575 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 576 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 577 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 578 pps_fcount = 0; 579 L_CLR(pps_freq); 580 #endif /* PPS_SYNC */ 581 } 582 583 SYSINIT(ntpclocks, SI_BOOT2_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 584 585 /* 586 * hardupdate() - local clock update 587 * 588 * This routine is called by ntp_adjtime() to update the local clock 589 * phase and frequency. The implementation is of an adaptive-parameter, 590 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 591 * time and frequency offset estimates for each call. If the kernel PPS 592 * discipline code is configured (PPS_SYNC), the PPS signal itself 593 * determines the new time offset, instead of the calling argument. 594 * Presumably, calls to ntp_adjtime() occur only when the caller 595 * believes the local clock is valid within some bound (+-128 ms with 596 * NTP). If the caller's time is far different than the PPS time, an 597 * argument will ensue, and it's not clear who will lose. 598 * 599 * For uncompensated quartz crystal oscillators and nominal update 600 * intervals less than 256 s, operation should be in phase-lock mode, 601 * where the loop is disciplined to phase. For update intervals greater 602 * than 1024 s, operation should be in frequency-lock mode, where the 603 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 604 * is selected by the STA_MODE status bit. 605 */ 606 static void 607 hardupdate(long offset) 608 { 609 long mtemp; 610 l_fp ftemp; 611 globaldata_t gd; 612 613 gd = mycpu; 614 615 /* 616 * Select how the phase is to be controlled and from which 617 * source. If the PPS signal is present and enabled to 618 * discipline the time, the PPS offset is used; otherwise, the 619 * argument offset is used. 620 */ 621 if (!(time_status & STA_PLL)) 622 return; 623 if (!((time_status & STA_PPSTIME) && (time_status & STA_PPSSIGNAL))) { 624 if (offset > MAXPHASE) 625 time_monitor = MAXPHASE; 626 else if (offset < -MAXPHASE) 627 time_monitor = -MAXPHASE; 628 else 629 time_monitor = offset; 630 L_LINT(time_offset, time_monitor); 631 } 632 633 /* 634 * Select how the frequency is to be controlled and in which 635 * mode (PLL or FLL). If the PPS signal is present and enabled 636 * to discipline the frequency, the PPS frequency is used; 637 * otherwise, the argument offset is used to compute it. 638 * 639 * gd_time_seconds is basically an uncompensated uptime. We use 640 * this for consistency. 641 */ 642 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 643 time_reftime = time_second; 644 return; 645 } 646 if (time_status & STA_FREQHOLD || time_reftime == 0) 647 time_reftime = time_second; 648 mtemp = time_second - time_reftime; 649 L_LINT(ftemp, time_monitor); 650 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 651 L_MPY(ftemp, mtemp); 652 L_ADD(time_freq, ftemp); 653 time_status &= ~STA_MODE; 654 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 655 L_LINT(ftemp, (time_monitor << 4) / mtemp); 656 L_RSHIFT(ftemp, SHIFT_FLL + 4); 657 L_ADD(time_freq, ftemp); 658 time_status |= STA_MODE; 659 } 660 time_reftime = time_second; 661 if (L_GINT(time_freq) > MAXFREQ) 662 L_LINT(time_freq, MAXFREQ); 663 else if (L_GINT(time_freq) < -MAXFREQ) 664 L_LINT(time_freq, -MAXFREQ); 665 } 666 667 #ifdef PPS_SYNC 668 /* 669 * hardpps() - discipline CPU clock oscillator to external PPS signal 670 * 671 * This routine is called at each PPS interrupt in order to discipline 672 * the CPU clock oscillator to the PPS signal. There are two independent 673 * first-order feedback loops, one for the phase, the other for the 674 * frequency. The phase loop measures and grooms the PPS phase offset 675 * and leaves it in a handy spot for the seconds overflow routine. The 676 * frequency loop averages successive PPS phase differences and 677 * calculates the PPS frequency offset, which is also processed by the 678 * seconds overflow routine. The code requires the caller to capture the 679 * time and architecture-dependent hardware counter values in 680 * nanoseconds at the on-time PPS signal transition. 681 * 682 * Note that, on some Unix systems this routine runs at an interrupt 683 * priority level higher than the timer interrupt routine hardclock(). 684 * Therefore, the variables used are distinct from the hardclock() 685 * variables, except for the actual time and frequency variables, which 686 * are determined by this routine and updated atomically. 687 */ 688 void 689 hardpps(struct timespec *tsp, long nsec) 690 { 691 long u_sec, u_nsec, v_nsec; /* temps */ 692 l_fp ftemp; 693 694 /* 695 * The signal is first processed by a range gate and frequency 696 * discriminator. The range gate rejects noise spikes outside 697 * the range +-500 us. The frequency discriminator rejects input 698 * signals with apparent frequency outside the range 1 +-500 699 * PPM. If two hits occur in the same second, we ignore the 700 * later hit; if not and a hit occurs outside the range gate, 701 * keep the later hit for later comparison, but do not process 702 * it. 703 */ 704 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 705 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 706 pps_valid = PPS_VALID; 707 u_sec = tsp->tv_sec; 708 u_nsec = tsp->tv_nsec; 709 if (u_nsec >= (NANOSECOND >> 1)) { 710 u_nsec -= NANOSECOND; 711 u_sec++; 712 } 713 v_nsec = u_nsec - pps_tf[0].tv_nsec; 714 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 715 MAXFREQ) 716 return; 717 pps_tf[2] = pps_tf[1]; 718 pps_tf[1] = pps_tf[0]; 719 pps_tf[0].tv_sec = u_sec; 720 pps_tf[0].tv_nsec = u_nsec; 721 722 /* 723 * Compute the difference between the current and previous 724 * counter values. If the difference exceeds 0.5 s, assume it 725 * has wrapped around, so correct 1.0 s. If the result exceeds 726 * the tick interval, the sample point has crossed a tick 727 * boundary during the last second, so correct the tick. Very 728 * intricate. 729 */ 730 u_nsec = nsec; 731 if (u_nsec > (NANOSECOND >> 1)) 732 u_nsec -= NANOSECOND; 733 else if (u_nsec < -(NANOSECOND >> 1)) 734 u_nsec += NANOSECOND; 735 pps_fcount += u_nsec; 736 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 737 return; 738 time_status &= ~STA_PPSJITTER; 739 740 /* 741 * A three-stage median filter is used to help denoise the PPS 742 * time. The median sample becomes the time offset estimate; the 743 * difference between the other two samples becomes the time 744 * dispersion (jitter) estimate. 745 */ 746 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 747 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 748 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 749 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 750 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 751 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 752 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 753 } else { 754 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 755 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 756 } 757 } else { 758 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 759 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 760 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 761 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 762 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 763 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 764 } else { 765 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 766 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 767 } 768 } 769 770 /* 771 * Nominal jitter is due to PPS signal noise and interrupt 772 * latency. If it exceeds the popcorn threshold, the sample is 773 * discarded. otherwise, if so enabled, the time offset is 774 * updated. We can tolerate a modest loss of data here without 775 * much degrading time accuracy. 776 */ 777 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 778 time_status |= STA_PPSJITTER; 779 pps_jitcnt++; 780 } else if (time_status & STA_PPSTIME) { 781 time_monitor = -v_nsec; 782 L_LINT(time_offset, time_monitor); 783 } 784 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 785 u_sec = pps_tf[0].tv_sec - pps_lastsec; 786 if (u_sec < (1 << pps_shift)) 787 return; 788 789 /* 790 * At the end of the calibration interval the difference between 791 * the first and last counter values becomes the scaled 792 * frequency. It will later be divided by the length of the 793 * interval to determine the frequency update. If the frequency 794 * exceeds a sanity threshold, or if the actual calibration 795 * interval is not equal to the expected length, the data are 796 * discarded. We can tolerate a modest loss of data here without 797 * much degrading frequency accuracy. 798 */ 799 pps_calcnt++; 800 v_nsec = -pps_fcount; 801 pps_lastsec = pps_tf[0].tv_sec; 802 pps_fcount = 0; 803 u_nsec = MAXFREQ << pps_shift; 804 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 805 pps_shift)) { 806 time_status |= STA_PPSERROR; 807 pps_errcnt++; 808 return; 809 } 810 811 /* 812 * Here the raw frequency offset and wander (stability) is 813 * calculated. If the wander is less than the wander threshold 814 * for four consecutive averaging intervals, the interval is 815 * doubled; if it is greater than the threshold for four 816 * consecutive intervals, the interval is halved. The scaled 817 * frequency offset is converted to frequency offset. The 818 * stability metric is calculated as the average of recent 819 * frequency changes, but is used only for performance 820 * monitoring. 821 */ 822 L_LINT(ftemp, v_nsec); 823 L_RSHIFT(ftemp, pps_shift); 824 L_SUB(ftemp, pps_freq); 825 u_nsec = L_GINT(ftemp); 826 if (u_nsec > PPS_MAXWANDER) { 827 L_LINT(ftemp, PPS_MAXWANDER); 828 pps_intcnt--; 829 time_status |= STA_PPSWANDER; 830 pps_stbcnt++; 831 } else if (u_nsec < -PPS_MAXWANDER) { 832 L_LINT(ftemp, -PPS_MAXWANDER); 833 pps_intcnt--; 834 time_status |= STA_PPSWANDER; 835 pps_stbcnt++; 836 } else { 837 pps_intcnt++; 838 } 839 if (pps_intcnt >= 4) { 840 pps_intcnt = 4; 841 if (pps_shift < pps_shiftmax) { 842 pps_shift++; 843 pps_intcnt = 0; 844 } 845 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 846 pps_intcnt = -4; 847 if (pps_shift > PPS_FAVG) { 848 pps_shift--; 849 pps_intcnt = 0; 850 } 851 } 852 if (u_nsec < 0) 853 u_nsec = -u_nsec; 854 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 855 856 /* 857 * The PPS frequency is recalculated and clamped to the maximum 858 * MAXFREQ. If enabled, the system clock frequency is updated as 859 * well. 860 */ 861 L_ADD(pps_freq, ftemp); 862 u_nsec = L_GINT(pps_freq); 863 if (u_nsec > MAXFREQ) 864 L_LINT(pps_freq, MAXFREQ); 865 else if (u_nsec < -MAXFREQ) 866 L_LINT(pps_freq, -MAXFREQ); 867 if (time_status & STA_PPSFREQ) 868 time_freq = pps_freq; 869 } 870 #endif /* PPS_SYNC */ 871