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 * $FreeBSD$ 32 */ 33 34 #include "opt_ntp.h" 35 36 #include <sys/param.h> 37 #include <sys/systm.h> 38 #include <sys/sysproto.h> 39 #include <sys/kernel.h> 40 #include <sys/proc.h> 41 #include <sys/time.h> 42 #include <sys/timex.h> 43 #include <sys/timetc.h> 44 #include <sys/timepps.h> 45 #include <sys/sysctl.h> 46 47 /* 48 * Single-precision macros for 64-bit machines 49 */ 50 typedef long long l_fp; 51 #define L_ADD(v, u) ((v) += (u)) 52 #define L_SUB(v, u) ((v) -= (u)) 53 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 54 #define L_NEG(v) ((v) = -(v)) 55 #define L_RSHIFT(v, n) \ 56 do { \ 57 if ((v) < 0) \ 58 (v) = -(-(v) >> (n)); \ 59 else \ 60 (v) = (v) >> (n); \ 61 } while (0) 62 #define L_MPY(v, a) ((v) *= (a)) 63 #define L_CLR(v) ((v) = 0) 64 #define L_ISNEG(v) ((v) < 0) 65 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 66 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 67 68 /* 69 * Generic NTP kernel interface 70 * 71 * These routines constitute the Network Time Protocol (NTP) interfaces 72 * for user and daemon application programs. The ntp_gettime() routine 73 * provides the time, maximum error (synch distance) and estimated error 74 * (dispersion) to client user application programs. The ntp_adjtime() 75 * routine is used by the NTP daemon to adjust the system clock to an 76 * externally derived time. The time offset and related variables set by 77 * this routine are used by other routines in this module to adjust the 78 * phase and frequency of the clock discipline loop which controls the 79 * system clock. 80 * 81 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 82 * defined), the time at each tick interrupt is derived directly from 83 * the kernel time variable. When the kernel time is reckoned in 84 * microseconds, (NTP_NANO undefined), the time is derived from the 85 * kernel time variable together with a variable representing the 86 * leftover nanoseconds at the last tick interrupt. In either case, the 87 * current nanosecond time is reckoned from these values plus an 88 * interpolated value derived by the clock routines in another 89 * architecture-specific module. The interpolation can use either a 90 * dedicated counter or a processor cycle counter (PCC) implemented in 91 * some architectures. 92 * 93 * Note that all routines must run at priority splclock or higher. 94 */ 95 /* 96 * Phase/frequency-lock loop (PLL/FLL) definitions 97 * 98 * The nanosecond clock discipline uses two variable types, time 99 * variables and frequency variables. Both types are represented as 64- 100 * bit fixed-point quantities with the decimal point between two 32-bit 101 * halves. On a 32-bit machine, each half is represented as a single 102 * word and mathematical operations are done using multiple-precision 103 * arithmetic. On a 64-bit machine, ordinary computer arithmetic is 104 * used. 105 * 106 * A time variable is a signed 64-bit fixed-point number in ns and 107 * fraction. It represents the remaining time offset to be amortized 108 * over succeeding tick interrupts. The maximum time offset is about 109 * 0.5 s and the resolution is about 2.3e-10 ns. 110 * 111 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 112 * 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 1 113 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 114 * |s s s| ns | 115 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 116 * | fraction | 117 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 118 * 119 * A frequency variable is a signed 64-bit fixed-point number in ns/s 120 * and fraction. It represents the ns and fraction to be added to the 121 * kernel time variable at each second. The maximum frequency offset is 122 * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s. 123 * 124 * 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 125 * 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 1 126 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 127 * |s s s s s s s s s s s s s| ns/s | 128 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 129 * | fraction | 130 * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 131 */ 132 /* 133 * The following variables establish the state of the PLL/FLL and the 134 * residual time and frequency offset of the local clock. 135 */ 136 #define SHIFT_PLL 4 /* PLL loop gain (shift) */ 137 #define SHIFT_FLL 2 /* FLL loop gain (shift) */ 138 139 static int time_state = TIME_OK; /* clock state */ 140 static int time_status = STA_UNSYNC; /* clock status bits */ 141 static long time_tai; /* TAI offset (s) */ 142 static long time_monitor; /* last time offset scaled (ns) */ 143 static long time_constant; /* poll interval (shift) (s) */ 144 static long time_precision = 1; /* clock precision (ns) */ 145 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 146 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 147 static long time_reftime; /* time at last adjustment (s) */ 148 static long time_tick; /* nanoseconds per tick (ns) */ 149 static l_fp time_offset; /* time offset (ns) */ 150 static l_fp time_freq; /* frequency offset (ns/s) */ 151 static l_fp time_adj; /* tick adjust (ns/s) */ 152 153 #ifdef PPS_SYNC 154 /* 155 * The following variables are used when a pulse-per-second (PPS) signal 156 * is available and connected via a modem control lead. They establish 157 * the engineering parameters of the clock discipline loop when 158 * controlled by the PPS signal. 159 */ 160 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 161 #define PPS_FAVGDEF 8 /* default freq avg int (s) (shift) */ 162 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 163 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 164 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 165 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 166 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 167 168 static struct timespec pps_tf[3]; /* phase median filter */ 169 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 170 static long pps_fcount; /* frequency accumulator */ 171 static long pps_jitter; /* nominal jitter (ns) */ 172 static long pps_stabil; /* nominal stability (scaled ns/s) */ 173 static long pps_lastsec; /* time at last calibration (s) */ 174 static int pps_valid; /* signal watchdog counter */ 175 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 176 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 177 static int pps_intcnt; /* wander counter */ 178 179 /* 180 * PPS signal quality monitors 181 */ 182 static long pps_calcnt; /* calibration intervals */ 183 static long pps_jitcnt; /* jitter limit exceeded */ 184 static long pps_stbcnt; /* stability limit exceeded */ 185 static long pps_errcnt; /* calibration errors */ 186 #endif /* PPS_SYNC */ 187 /* 188 * End of phase/frequency-lock loop (PLL/FLL) definitions 189 */ 190 191 static void ntp_init(void); 192 static void hardupdate(long offset); 193 194 /* 195 * ntp_gettime() - NTP user application interface 196 * 197 * See the timex.h header file for synopsis and API description. Note 198 * that the TAI offset is returned in the ntvtimeval.tai structure 199 * member. 200 */ 201 static int 202 ntp_sysctl(SYSCTL_HANDLER_ARGS) 203 { 204 struct ntptimeval ntv; /* temporary structure */ 205 struct timespec atv; /* nanosecond time */ 206 207 nanotime(&atv); 208 ntv.time.tv_sec = atv.tv_sec; 209 ntv.time.tv_nsec = atv.tv_nsec; 210 ntv.maxerror = time_maxerror; 211 ntv.esterror = time_esterror; 212 ntv.tai = time_tai; 213 ntv.time_state = time_state; 214 215 /* 216 * Status word error decode. If any of these conditions occur, 217 * an error is returned, instead of the status word. Most 218 * applications will care only about the fact the system clock 219 * may not be trusted, not about the details. 220 * 221 * Hardware or software error 222 */ 223 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 224 225 /* 226 * PPS signal lost when either time or frequency synchronization 227 * requested 228 */ 229 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 230 !(time_status & STA_PPSSIGNAL)) || 231 232 /* 233 * PPS jitter exceeded when time synchronization requested 234 */ 235 (time_status & STA_PPSTIME && 236 time_status & STA_PPSJITTER) || 237 238 /* 239 * PPS wander exceeded or calibration error when frequency 240 * synchronization requested 241 */ 242 (time_status & STA_PPSFREQ && 243 time_status & (STA_PPSWANDER | STA_PPSERROR))) 244 ntv.time_state = TIME_ERROR; 245 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 246 } 247 248 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 249 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 250 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 251 252 #ifdef PPS_SYNC 253 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 254 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 255 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, ""); 256 257 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 258 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 259 #endif 260 /* 261 * ntp_adjtime() - NTP daemon application interface 262 * 263 * See the timex.h header file for synopsis and API description. Note 264 * that the timex.constant structure member has a dual purpose to set 265 * the time constant and to set the TAI offset. 266 */ 267 #ifndef _SYS_SYSPROTO_H_ 268 struct ntp_adjtime_args { 269 struct timex *tp; 270 }; 271 #endif 272 273 int 274 ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap) 275 { 276 struct timex ntv; /* temporary structure */ 277 long freq; /* frequency ns/s) */ 278 int modes; /* mode bits from structure */ 279 int s; /* caller priority */ 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 = suser(p); 298 if (error) 299 return (error); 300 s = splclock(); 301 if (modes & MOD_MAXERROR) 302 time_maxerror = ntv.maxerror; 303 if (modes & MOD_ESTERROR) 304 time_esterror = ntv.esterror; 305 if (modes & MOD_STATUS) { 306 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) { 307 time_state = TIME_OK; 308 time_status = STA_UNSYNC; 309 #ifdef PPS_SYNC 310 pps_shift = PPS_FAVG; 311 #endif /* PPS_SYNC */ 312 } 313 time_status &= STA_RONLY; 314 time_status |= ntv.status & ~STA_RONLY; 315 } 316 if (modes & MOD_TIMECONST) { 317 if (ntv.constant < 0) 318 time_constant = 0; 319 else if (ntv.constant > MAXTC) 320 time_constant = MAXTC; 321 else 322 time_constant = ntv.constant; 323 } 324 if (modes & MOD_TAI) { 325 if (ntv.constant > 0) /* XXX zero & negative numbers ? */ 326 time_tai = ntv.constant; 327 } 328 #ifdef PPS_SYNC 329 if (modes & MOD_PPSMAX) { 330 if (ntv.shift < PPS_FAVG) 331 pps_shiftmax = PPS_FAVG; 332 else if (ntv.shift > PPS_FAVGMAX) 333 pps_shiftmax = PPS_FAVGMAX; 334 else 335 pps_shiftmax = ntv.shift; 336 } 337 #endif /* PPS_SYNC */ 338 if (modes & MOD_NANO) 339 time_status |= STA_NANO; 340 if (modes & MOD_MICRO) 341 time_status &= ~STA_NANO; 342 if (modes & MOD_CLKB) 343 time_status |= STA_CLK; 344 if (modes & MOD_CLKA) 345 time_status &= ~STA_CLK; 346 if (modes & MOD_OFFSET) { 347 if (time_status & STA_NANO) 348 hardupdate(ntv.offset); 349 else 350 hardupdate(ntv.offset * 1000); 351 } 352 if (modes & MOD_FREQUENCY) { 353 freq = (ntv.freq * 1000LL) >> 16; 354 if (freq > MAXFREQ) 355 L_LINT(time_freq, MAXFREQ); 356 else if (freq < -MAXFREQ) 357 L_LINT(time_freq, -MAXFREQ); 358 else 359 L_LINT(time_freq, freq); 360 #ifdef PPS_SYNC 361 pps_freq = time_freq; 362 #endif /* PPS_SYNC */ 363 } 364 365 /* 366 * Retrieve all clock variables. Note that the TAI offset is 367 * returned only by ntp_gettime(); 368 */ 369 if (time_status & STA_NANO) 370 ntv.offset = time_monitor; 371 else 372 ntv.offset = time_monitor / 1000; /* XXX rounding ? */ 373 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 374 ntv.maxerror = time_maxerror; 375 ntv.esterror = time_esterror; 376 ntv.status = time_status; 377 ntv.constant = time_constant; 378 if (time_status & STA_NANO) 379 ntv.precision = time_precision; 380 else 381 ntv.precision = time_precision / 1000; 382 ntv.tolerance = MAXFREQ * SCALE_PPM; 383 #ifdef PPS_SYNC 384 ntv.shift = pps_shift; 385 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 386 if (time_status & STA_NANO) 387 ntv.jitter = pps_jitter; 388 else 389 ntv.jitter = pps_jitter / 1000; 390 ntv.stabil = pps_stabil; 391 ntv.calcnt = pps_calcnt; 392 ntv.errcnt = pps_errcnt; 393 ntv.jitcnt = pps_jitcnt; 394 ntv.stbcnt = pps_stbcnt; 395 #endif /* PPS_SYNC */ 396 splx(s); 397 398 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 399 if (error) 400 return (error); 401 402 /* 403 * Status word error decode. See comments in 404 * ntp_gettime() routine. 405 */ 406 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 407 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 408 !(time_status & STA_PPSSIGNAL)) || 409 (time_status & STA_PPSTIME && 410 time_status & STA_PPSJITTER) || 411 (time_status & STA_PPSFREQ && 412 time_status & (STA_PPSWANDER | STA_PPSERROR))) 413 p->p_retval[0] = TIME_ERROR; 414 else 415 p->p_retval[0] = time_state; 416 return (error); 417 } 418 419 /* 420 * second_overflow() - called after ntp_tick_adjust() 421 * 422 * This routine is ordinarily called immediately following the above 423 * routine ntp_tick_adjust(). While these two routines are normally 424 * combined, they are separated here only for the purposes of 425 * simulation. 426 */ 427 void 428 ntp_update_second(struct timecounter *tcp) 429 { 430 u_int32_t *newsec; 431 l_fp ftemp; /* 32/64-bit temporary */ 432 433 newsec = &tcp->tc_offset_sec; 434 /* 435 * On rollover of the second both the nanosecond and microsecond 436 * clocks are updated and the state machine cranked as 437 * necessary. The phase adjustment to be used for the next 438 * second is calculated and the maximum error is increased by 439 * the tolerance. 440 */ 441 time_maxerror += MAXFREQ / 1000; 442 443 /* 444 * Leap second processing. If in leap-insert state at 445 * the end of the day, the system clock is set back one 446 * second; if in leap-delete state, the system clock is 447 * set ahead one second. The nano_time() routine or 448 * external clock driver will insure that reported time 449 * is always monotonic. 450 */ 451 switch (time_state) { 452 453 /* 454 * No warning. 455 */ 456 case TIME_OK: 457 if (time_status & STA_INS) 458 time_state = TIME_INS; 459 else if (time_status & STA_DEL) 460 time_state = TIME_DEL; 461 break; 462 463 /* 464 * Insert second 23:59:60 following second 465 * 23:59:59. 466 */ 467 case TIME_INS: 468 if (!(time_status & STA_INS)) 469 time_state = TIME_OK; 470 else if ((*newsec) % 86400 == 0) { 471 (*newsec)--; 472 time_state = TIME_OOP; 473 } 474 break; 475 476 /* 477 * Delete second 23:59:59. 478 */ 479 case TIME_DEL: 480 if (!(time_status & STA_DEL)) 481 time_state = TIME_OK; 482 else if (((*newsec) + 1) % 86400 == 0) { 483 (*newsec)++; 484 time_tai--; 485 time_state = TIME_WAIT; 486 } 487 break; 488 489 /* 490 * Insert second in progress. 491 */ 492 case TIME_OOP: 493 time_tai++; 494 time_state = TIME_WAIT; 495 break; 496 497 /* 498 * Wait for status bits to clear. 499 */ 500 case TIME_WAIT: 501 if (!(time_status & (STA_INS | STA_DEL))) 502 time_state = TIME_OK; 503 } 504 505 /* 506 * Compute the total time adjustment for the next second 507 * in ns. The offset is reduced by a factor depending on 508 * whether the PPS signal is operating. Note that the 509 * value is in effect scaled by the clock frequency, 510 * since the adjustment is added at each tick interrupt. 511 */ 512 ftemp = time_offset; 513 #ifdef PPS_SYNC 514 /* XXX even if PPS signal dies we should finish adjustment ? */ 515 if (time_status & STA_PPSTIME && time_status & 516 STA_PPSSIGNAL) 517 L_RSHIFT(ftemp, pps_shift); 518 else 519 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 520 #else 521 L_RSHIFT(ftemp, SHIFT_PLL + time_constant); 522 #endif /* PPS_SYNC */ 523 time_adj = ftemp; 524 L_SUB(time_offset, ftemp); 525 L_ADD(time_adj, time_freq); 526 tcp->tc_adjustment = time_adj; 527 #ifdef PPS_SYNC 528 if (pps_valid > 0) 529 pps_valid--; 530 else 531 time_status &= ~STA_PPSSIGNAL; 532 #endif /* PPS_SYNC */ 533 } 534 535 /* 536 * ntp_init() - initialize variables and structures 537 * 538 * This routine must be called after the kernel variables hz and tick 539 * are set or changed and before the next tick interrupt. In this 540 * particular implementation, these values are assumed set elsewhere in 541 * the kernel. The design allows the clock frequency and tick interval 542 * to be changed while the system is running. So, this routine should 543 * probably be integrated with the code that does that. 544 */ 545 static void 546 ntp_init() 547 { 548 549 /* 550 * The following variable must be initialized any time the 551 * kernel variable hz is changed. 552 */ 553 time_tick = NANOSECOND / hz; 554 555 /* 556 * The following variables are initialized only at startup. Only 557 * those structures not cleared by the compiler need to be 558 * initialized, and these only in the simulator. In the actual 559 * kernel, any nonzero values here will quickly evaporate. 560 */ 561 L_CLR(time_offset); 562 L_CLR(time_freq); 563 #ifdef PPS_SYNC 564 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 565 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 566 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 567 pps_fcount = 0; 568 L_CLR(pps_freq); 569 #endif /* PPS_SYNC */ 570 } 571 572 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 573 574 /* 575 * hardupdate() - local clock update 576 * 577 * This routine is called by ntp_adjtime() to update the local clock 578 * phase and frequency. The implementation is of an adaptive-parameter, 579 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 580 * time and frequency offset estimates for each call. If the kernel PPS 581 * discipline code is configured (PPS_SYNC), the PPS signal itself 582 * determines the new time offset, instead of the calling argument. 583 * Presumably, calls to ntp_adjtime() occur only when the caller 584 * believes the local clock is valid within some bound (+-128 ms with 585 * NTP). If the caller's time is far different than the PPS time, an 586 * argument will ensue, and it's not clear who will lose. 587 * 588 * For uncompensated quartz crystal oscillators and nominal update 589 * intervals less than 256 s, operation should be in phase-lock mode, 590 * where the loop is disciplined to phase. For update intervals greater 591 * than 1024 s, operation should be in frequency-lock mode, where the 592 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 593 * is selected by the STA_MODE status bit. 594 */ 595 static void 596 hardupdate(offset) 597 long offset; /* clock offset (ns) */ 598 { 599 long mtemp; 600 l_fp ftemp; 601 602 /* 603 * Select how the phase is to be controlled and from which 604 * source. If the PPS signal is present and enabled to 605 * discipline the time, the PPS offset is used; otherwise, the 606 * argument offset is used. 607 */ 608 if (!(time_status & STA_PLL)) 609 return; 610 if (!(time_status & STA_PPSTIME && time_status & 611 STA_PPSSIGNAL)) { 612 if (offset > MAXPHASE) 613 time_monitor = MAXPHASE; 614 else if (offset < -MAXPHASE) 615 time_monitor = -MAXPHASE; 616 else 617 time_monitor = offset; 618 L_LINT(time_offset, time_monitor); 619 } 620 621 /* 622 * Select how the frequency is to be controlled and in which 623 * mode (PLL or FLL). If the PPS signal is present and enabled 624 * to discipline the frequency, the PPS frequency is used; 625 * otherwise, the argument offset is used to compute it. 626 */ 627 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 628 time_reftime = time_second; 629 return; 630 } 631 if (time_status & STA_FREQHOLD || time_reftime == 0) 632 time_reftime = time_second; 633 mtemp = time_second - time_reftime; 634 L_LINT(ftemp, time_monitor); 635 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 636 L_MPY(ftemp, mtemp); 637 L_ADD(time_freq, ftemp); 638 time_status &= ~STA_MODE; 639 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > 640 MAXSEC)) { 641 L_LINT(ftemp, (time_monitor << 4) / mtemp); 642 L_RSHIFT(ftemp, SHIFT_FLL + 4); 643 L_ADD(time_freq, ftemp); 644 time_status |= STA_MODE; 645 } 646 time_reftime = time_second; 647 if (L_GINT(time_freq) > MAXFREQ) 648 L_LINT(time_freq, MAXFREQ); 649 else if (L_GINT(time_freq) < -MAXFREQ) 650 L_LINT(time_freq, -MAXFREQ); 651 } 652 653 #ifdef PPS_SYNC 654 /* 655 * hardpps() - discipline CPU clock oscillator to external PPS signal 656 * 657 * This routine is called at each PPS interrupt in order to discipline 658 * the CPU clock oscillator to the PPS signal. There are two independent 659 * first-order feedback loops, one for the phase, the other for the 660 * frequency. The phase loop measures and grooms the PPS phase offset 661 * and leaves it in a handy spot for the seconds overflow routine. The 662 * frequency loop averages successive PPS phase differences and 663 * calculates the PPS frequency offset, which is also processed by the 664 * seconds overflow routine. The code requires the caller to capture the 665 * time and architecture-dependent hardware counter values in 666 * nanoseconds at the on-time PPS signal transition. 667 * 668 * Note that, on some Unix systems this routine runs at an interrupt 669 * priority level higher than the timer interrupt routine hardclock(). 670 * Therefore, the variables used are distinct from the hardclock() 671 * variables, except for the actual time and frequency variables, which 672 * are determined by this routine and updated atomically. 673 */ 674 void 675 hardpps(tsp, nsec) 676 struct timespec *tsp; /* time at PPS */ 677 long nsec; /* hardware counter at PPS */ 678 { 679 long u_sec, u_nsec, v_nsec; /* temps */ 680 l_fp ftemp; 681 682 /* 683 * The signal is first processed by a range gate and frequency 684 * discriminator. The range gate rejects noise spikes outside 685 * the range +-500 us. The frequency discriminator rejects input 686 * signals with apparent frequency outside the range 1 +-500 687 * PPM. If two hits occur in the same second, we ignore the 688 * later hit; if not and a hit occurs outside the range gate, 689 * keep the later hit for later comparison, but do not process 690 * it. 691 */ 692 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 693 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 694 pps_valid = PPS_VALID; 695 u_sec = tsp->tv_sec; 696 u_nsec = tsp->tv_nsec; 697 if (u_nsec >= (NANOSECOND >> 1)) { 698 u_nsec -= NANOSECOND; 699 u_sec++; 700 } 701 v_nsec = u_nsec - pps_tf[0].tv_nsec; 702 if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND - 703 MAXFREQ) 704 return; 705 pps_tf[2] = pps_tf[1]; 706 pps_tf[1] = pps_tf[0]; 707 pps_tf[0].tv_sec = u_sec; 708 pps_tf[0].tv_nsec = u_nsec; 709 710 /* 711 * Compute the difference between the current and previous 712 * counter values. If the difference exceeds 0.5 s, assume it 713 * has wrapped around, so correct 1.0 s. If the result exceeds 714 * the tick interval, the sample point has crossed a tick 715 * boundary during the last second, so correct the tick. Very 716 * intricate. 717 */ 718 u_nsec = nsec; 719 if (u_nsec > (NANOSECOND >> 1)) 720 u_nsec -= NANOSECOND; 721 else if (u_nsec < -(NANOSECOND >> 1)) 722 u_nsec += NANOSECOND; 723 pps_fcount += u_nsec; 724 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) 725 return; 726 time_status &= ~STA_PPSJITTER; 727 728 /* 729 * A three-stage median filter is used to help denoise the PPS 730 * time. The median sample becomes the time offset estimate; the 731 * difference between the other two samples becomes the time 732 * dispersion (jitter) estimate. 733 */ 734 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 735 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 736 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 737 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 738 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 739 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 740 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 741 } else { 742 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 743 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 744 } 745 } else { 746 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 747 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 748 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 749 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 750 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 751 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 752 } else { 753 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 754 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 755 } 756 } 757 758 /* 759 * Nominal jitter is due to PPS signal noise and interrupt 760 * latency. If it exceeds the popcorn threshold, the sample is 761 * discarded. otherwise, if so enabled, the time offset is 762 * updated. We can tolerate a modest loss of data here without 763 * much degrading time accuracy. 764 */ 765 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 766 time_status |= STA_PPSJITTER; 767 pps_jitcnt++; 768 } else if (time_status & STA_PPSTIME) { 769 time_monitor = -v_nsec; 770 L_LINT(time_offset, time_monitor); 771 } 772 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 773 u_sec = pps_tf[0].tv_sec - pps_lastsec; 774 if (u_sec < (1 << pps_shift)) 775 return; 776 777 /* 778 * At the end of the calibration interval the difference between 779 * the first and last counter values becomes the scaled 780 * frequency. It will later be divided by the length of the 781 * interval to determine the frequency update. If the frequency 782 * exceeds a sanity threshold, or if the actual calibration 783 * interval is not equal to the expected length, the data are 784 * discarded. We can tolerate a modest loss of data here without 785 * much degrading frequency accuracy. 786 */ 787 pps_calcnt++; 788 v_nsec = -pps_fcount; 789 pps_lastsec = pps_tf[0].tv_sec; 790 pps_fcount = 0; 791 u_nsec = MAXFREQ << pps_shift; 792 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 793 pps_shift)) { 794 time_status |= STA_PPSERROR; 795 pps_errcnt++; 796 return; 797 } 798 799 /* 800 * Here the raw frequency offset and wander (stability) is 801 * calculated. If the wander is less than the wander threshold 802 * for four consecutive averaging intervals, the interval is 803 * doubled; if it is greater than the threshold for four 804 * consecutive intervals, the interval is halved. The scaled 805 * frequency offset is converted to frequency offset. The 806 * stability metric is calculated as the average of recent 807 * frequency changes, but is used only for performance 808 * monitoring. 809 */ 810 L_LINT(ftemp, v_nsec); 811 L_RSHIFT(ftemp, pps_shift); 812 L_SUB(ftemp, pps_freq); 813 u_nsec = L_GINT(ftemp); 814 if (u_nsec > PPS_MAXWANDER) { 815 L_LINT(ftemp, PPS_MAXWANDER); 816 pps_intcnt--; 817 time_status |= STA_PPSWANDER; 818 pps_stbcnt++; 819 } else if (u_nsec < -PPS_MAXWANDER) { 820 L_LINT(ftemp, -PPS_MAXWANDER); 821 pps_intcnt--; 822 time_status |= STA_PPSWANDER; 823 pps_stbcnt++; 824 } else { 825 pps_intcnt++; 826 } 827 if (pps_intcnt >= 4) { 828 pps_intcnt = 4; 829 if (pps_shift < pps_shiftmax) { 830 pps_shift++; 831 pps_intcnt = 0; 832 } 833 } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) { 834 pps_intcnt = -4; 835 if (pps_shift > PPS_FAVG) { 836 pps_shift--; 837 pps_intcnt = 0; 838 } 839 } 840 if (u_nsec < 0) 841 u_nsec = -u_nsec; 842 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 843 844 /* 845 * The PPS frequency is recalculated and clamped to the maximum 846 * MAXFREQ. If enabled, the system clock frequency is updated as 847 * well. 848 */ 849 L_ADD(pps_freq, ftemp); 850 u_nsec = L_GINT(pps_freq); 851 if (u_nsec > MAXFREQ) 852 L_LINT(pps_freq, MAXFREQ); 853 else if (u_nsec < -MAXFREQ) 854 L_LINT(pps_freq, -MAXFREQ); 855 if (time_status & STA_PPSFREQ) 856 time_freq = pps_freq; 857 } 858 #endif /* PPS_SYNC */ 859