1 /*********************************************************************** 2 * * 3 * Copyright (c) David L. Mills 1993-1999 * 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/timepps.h> 44 #include <sys/sysctl.h> 45 46 /* 47 * Single-precision macros for 64-bit machines 48 */ 49 typedef long long l_fp; 50 #define L_ADD(v, u) ((v) += (u)) 51 #define L_SUB(v, u) ((v) -= (u)) 52 #define L_ADDHI(v, a) ((v) += (long long)(a) << 32) 53 #define L_NEG(v) ((v) = -(v)) 54 #define L_RSHIFT(v, n) \ 55 do { \ 56 if ((v) < 0) \ 57 (v) = -(-(v) >> (n)); \ 58 else \ 59 (v) = (v) >> (n); \ 60 } while (0) 61 #define L_MPY(v, a) ((v) *= (a)) 62 #define L_CLR(v) ((v) = 0) 63 #define L_ISNEG(v) ((v) < 0) 64 #define L_LINT(v, a) ((v) = (long long)(a) << 32) 65 #define L_GINT(v) ((v) < 0 ? -(-(v) >> 32) : (v) >> 32) 66 67 /* 68 * Generic NTP kernel interface 69 * 70 * These routines constitute the Network Time Protocol (NTP) interfaces 71 * for user and daemon application programs. The ntp_gettime() routine 72 * provides the time, maximum error (synch distance) and estimated error 73 * (dispersion) to client user application programs. The ntp_adjtime() 74 * routine is used by the NTP daemon to adjust the system clock to an 75 * externally derived time. The time offset and related variables set by 76 * this routine are used by other routines in this module to adjust the 77 * phase and frequency of the clock discipline loop which controls the 78 * system clock. 79 * 80 * When the kernel time is reckoned directly in nanoseconds (NTP_NANO 81 * defined), the time at each tick interrupt is derived directly from 82 * the kernel time variable. When the kernel time is reckoned in 83 * microseconds, (NTP_NANO undefined), the time is derived from the 84 * kernel time variable together with a variable representing the 85 * leftover nanoseconds at the last tick interrupt. In either case, the 86 * current nanosecond time is reckoned from these values plus an 87 * interpolated value derived by the clock routines in another 88 * architecture-specific module. The interpolation can use either a 89 * dedicated counter or a processor cycle counter (PCC) implemented in 90 * some architectures. 91 * 92 * Note that all routines must run at priority splclock or higher. 93 */ 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_constant; /* poll interval (shift) (s) */ 142 static long time_precision = 1; /* clock precision (ns) */ 143 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */ 144 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */ 145 static long time_reftime; /* time at last adjustment (s) */ 146 static long time_tick; /* nanoseconds per tick (ns) */ 147 static l_fp time_offset; /* time offset (ns) */ 148 static l_fp time_freq; /* frequency offset (ns/s) */ 149 static l_fp time_adj; /* resulting adjustment */ 150 151 #ifdef PPS_SYNC 152 /* 153 * The following variables are used when a pulse-per-second (PPS) signal 154 * is available and connected via a modem control lead. They establish 155 * the engineering parameters of the clock discipline loop when 156 * controlled by the PPS signal. 157 */ 158 #define PPS_FAVG 2 /* min freq avg interval (s) (shift) */ 159 #define PPS_FAVGDEF 7 /* default freq avg int (s) (shift) */ 160 #define PPS_FAVGMAX 15 /* max freq avg interval (s) (shift) */ 161 #define PPS_PAVG 4 /* phase avg interval (s) (shift) */ 162 #define PPS_VALID 120 /* PPS signal watchdog max (s) */ 163 #define PPS_MAXWANDER 100000 /* max PPS wander (ns/s) */ 164 #define PPS_POPCORN 2 /* popcorn spike threshold (shift) */ 165 166 static struct timespec pps_tf[3]; /* phase median filter */ 167 static l_fp pps_offset; /* time offset (ns) */ 168 static l_fp pps_freq; /* scaled frequency offset (ns/s) */ 169 static long pps_fcount; /* frequency accumulator */ 170 static long pps_jitter; /* nominal jitter (ns) */ 171 static long pps_stabil; /* nominal stability (scaled ns/s) */ 172 static long pps_lastsec; /* time at last calibration (s) */ 173 static int pps_valid; /* signal watchdog counter */ 174 static int pps_shift = PPS_FAVG; /* interval duration (s) (shift) */ 175 static int pps_shiftmax = PPS_FAVGDEF; /* max interval duration (s) (shift) */ 176 static int pps_intcnt; /* wander counter */ 177 static int pps_letgo; /* PLL frequency hold-off */ 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. 198 */ 199 static int 200 ntp_sysctl SYSCTL_HANDLER_ARGS 201 { 202 struct ntptimeval ntv; /* temporary structure */ 203 struct timespec atv; /* nanosecond time */ 204 205 nanotime(&atv); 206 ntv.time.tv_sec = atv.tv_sec; 207 ntv.time.tv_nsec = atv.tv_nsec; 208 ntv.maxerror = time_maxerror; 209 ntv.esterror = time_esterror; 210 ntv.time_state = time_state; 211 212 /* 213 * Status word error decode. If any of these conditions occur, 214 * an error is returned, instead of the status word. Most 215 * applications will care only about the fact the system clock 216 * may not be trusted, not about the details. 217 * 218 * Hardware or software error 219 */ 220 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 221 222 /* 223 * PPS signal lost when either time or frequency synchronization 224 * requested 225 */ 226 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 227 !(time_status & STA_PPSSIGNAL)) || 228 229 /* 230 * PPS jitter exceeded when time synchronization requested 231 */ 232 (time_status & STA_PPSTIME && 233 time_status & STA_PPSJITTER) || 234 235 /* 236 * PPS wander exceeded or calibration error when frequency 237 * synchronization requested 238 */ 239 (time_status & STA_PPSFREQ && 240 time_status & (STA_PPSWANDER | STA_PPSERROR))) 241 ntv.time_state = TIME_ERROR; 242 return (sysctl_handle_opaque(oidp, &ntv, sizeof ntv, req)); 243 } 244 245 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, ""); 246 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD, 247 0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", ""); 248 249 #ifdef PPS_SYNC 250 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, ""); 251 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, ""); 252 253 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", ""); 254 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", ""); 255 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_offset, CTLFLAG_RD, &pps_offset, sizeof(pps_offset), "I", ""); 256 #endif 257 /* 258 * ntp_adjtime() - NTP daemon application interface 259 * 260 * See the timex.h header file for synopsis and API description. 261 */ 262 #ifndef _SYS_SYSPROTO_H_ 263 struct ntp_adjtime_args { 264 struct timex *tp; 265 }; 266 #endif 267 268 int 269 ntp_adjtime(struct proc *p, struct ntp_adjtime_args *uap) 270 { 271 struct timex ntv; /* temporary structure */ 272 long freq; /* frequency ns/s) */ 273 int modes; /* mode bits from structure */ 274 int s; /* caller priority */ 275 int error; 276 277 error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv)); 278 if (error) 279 return(error); 280 281 /* 282 * Update selected clock variables - only the superuser can 283 * change anything. Note that there is no error checking here on 284 * the assumption the superuser should know what it is doing. 285 */ 286 modes = ntv.modes; 287 if (modes) 288 error = suser(p); 289 if (error) 290 return (error); 291 s = splclock(); 292 if (modes & MOD_FREQUENCY) { 293 freq = (ntv.freq * 1000LL) >> 16; 294 if (freq > MAXFREQ) 295 L_LINT(time_freq, MAXFREQ); 296 else if (freq < -MAXFREQ) 297 L_LINT(time_freq, -MAXFREQ); 298 else 299 L_LINT(time_freq, freq); 300 301 #ifdef PPS_SYNC 302 pps_freq = time_freq; 303 #endif /* PPS_SYNC */ 304 } 305 if (modes & MOD_MAXERROR) 306 time_maxerror = ntv.maxerror; 307 if (modes & MOD_ESTERROR) 308 time_esterror = ntv.esterror; 309 if (modes & MOD_STATUS) { 310 time_status &= STA_RONLY; 311 time_status |= ntv.status & ~STA_RONLY; 312 } 313 if (modes & MOD_TIMECONST) { 314 if (ntv.constant < 0) 315 time_constant = 0; 316 else if (ntv.constant > MAXTC) 317 time_constant = MAXTC; 318 else 319 time_constant = ntv.constant; 320 } 321 #ifdef PPS_SYNC 322 if (modes & MOD_PPSMAX) { 323 if (ntv.shift < PPS_FAVG) 324 pps_shiftmax = PPS_FAVG; 325 else if (ntv.shift > PPS_FAVGMAX) 326 pps_shiftmax = PPS_FAVGMAX; 327 else 328 pps_shiftmax = ntv.shift; 329 } 330 #endif /* PPS_SYNC */ 331 if (modes & MOD_NANO) 332 time_status |= STA_NANO; 333 if (modes & MOD_MICRO) 334 time_status &= ~STA_NANO; 335 if (modes & MOD_CLKB) 336 time_status |= STA_CLK; 337 if (modes & MOD_CLKA) 338 time_status &= ~STA_CLK; 339 if (modes & MOD_OFFSET) { 340 if (time_status & STA_NANO) 341 hardupdate(ntv.offset); 342 else 343 hardupdate(ntv.offset * 1000); 344 } 345 346 /* 347 * Retrieve all clock variables 348 */ 349 if (time_status & STA_NANO) 350 ntv.offset = L_GINT(time_offset); 351 else 352 ntv.offset = L_GINT(time_offset) / 1000; 353 ntv.freq = L_GINT((time_freq / 1000LL) << 16); 354 ntv.maxerror = time_maxerror; 355 ntv.esterror = time_esterror; 356 ntv.status = time_status; 357 ntv.constant = time_constant; 358 if (time_status & STA_NANO) 359 ntv.precision = time_precision; 360 else 361 ntv.precision = time_precision / 1000; 362 ntv.tolerance = MAXFREQ * SCALE_PPM; 363 #ifdef PPS_SYNC 364 ntv.shift = pps_shift; 365 ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16); 366 if (time_status & STA_NANO) 367 ntv.jitter = pps_jitter; 368 else 369 ntv.jitter = pps_jitter / 1000; 370 ntv.stabil = pps_stabil; 371 ntv.calcnt = pps_calcnt; 372 ntv.errcnt = pps_errcnt; 373 ntv.jitcnt = pps_jitcnt; 374 ntv.stbcnt = pps_stbcnt; 375 #endif /* PPS_SYNC */ 376 splx(s); 377 378 error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv)); 379 if (error) 380 return (error); 381 382 /* 383 * Status word error decode. See comments in 384 * ntp_gettime() routine. 385 */ 386 if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) || 387 (time_status & (STA_PPSFREQ | STA_PPSTIME) && 388 !(time_status & STA_PPSSIGNAL)) || 389 (time_status & STA_PPSTIME && 390 time_status & STA_PPSJITTER) || 391 (time_status & STA_PPSFREQ && 392 time_status & (STA_PPSWANDER | STA_PPSERROR))) 393 p->p_retval[0] = TIME_ERROR; 394 else 395 p->p_retval[0] = time_state; 396 return (error); 397 } 398 399 /* 400 * second_overflow() - called after ntp_tick_adjust() 401 * 402 * This routine is ordinarily called immediately following the above 403 * routine ntp_tick_adjust(). While these two routines are normally 404 * combined, they are separated here only for the purposes of 405 * simulation. 406 */ 407 void 408 ntp_update_second(struct timecounter *tcp) 409 { 410 u_int32_t *newsec; 411 412 newsec = &tcp->tc_offset_sec; 413 /* 414 * On rollover of the second both the nanosecond and microsecond 415 * clocks are updated and the state machine cranked as 416 * necessary. The phase adjustment to be used for the next 417 * second is calculated and the maximum error is increased by 418 * the tolerance. 419 */ 420 time_maxerror += MAXFREQ / 1000; 421 422 /* 423 * Leap second processing. If in leap-insert state at 424 * the end of the day, the system clock is set back one 425 * second; if in leap-delete state, the system clock is 426 * set ahead one second. The nano_time() routine or 427 * external clock driver will insure that reported time 428 * is always monotonic. 429 */ 430 switch (time_state) { 431 432 /* 433 * No warning. 434 */ 435 case TIME_OK: 436 if (time_status & STA_INS) 437 time_state = TIME_INS; 438 else if (time_status & STA_DEL) 439 time_state = TIME_DEL; 440 break; 441 442 /* 443 * Insert second 23:59:60 following second 444 * 23:59:59. 445 */ 446 case TIME_INS: 447 if (!(time_status & STA_INS)) 448 time_state = TIME_OK; 449 else if ((*newsec) % 86400 == 0) { 450 (*newsec)--; 451 time_state = TIME_OOP; 452 } 453 break; 454 455 /* 456 * Delete second 23:59:59. 457 */ 458 case TIME_DEL: 459 if (!(time_status & STA_DEL)) 460 time_state = TIME_OK; 461 else if (((*newsec) + 1) % 86400 == 0) { 462 (*newsec)++; 463 time_state = TIME_WAIT; 464 } 465 break; 466 467 /* 468 * Insert second in progress. 469 */ 470 case TIME_OOP: 471 time_state = TIME_WAIT; 472 break; 473 474 /* 475 * Wait for status bits to clear. 476 */ 477 case TIME_WAIT: 478 if (!(time_status & (STA_INS | STA_DEL))) 479 time_state = TIME_OK; 480 } 481 482 /* 483 * Compute the total time adjustment for the next second 484 * in ns. The offset is reduced by a factor depending on 485 * whether the PPS signal is operating. Note that the 486 * value is in effect scaled by the clock frequency, 487 * since the adjustment is added at each tick interrupt. 488 */ 489 #ifdef PPS_SYNC 490 /* XXX even if signal dies we should finish adjustment ? */ 491 if (time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL) { 492 time_adj = pps_offset; 493 L_RSHIFT(time_adj, pps_shift); 494 L_SUB(pps_offset, time_adj); 495 } else { 496 time_adj = time_offset; 497 L_RSHIFT(time_adj, SHIFT_PLL + time_constant); 498 L_SUB(time_offset, time_adj); 499 } 500 #else 501 time_adj = time_offset; 502 L_RSHIFT(time_adj, SHIFT_PLL + time_constant); 503 L_SUB(time_offset, time_adj); 504 #endif /* PPS_SYNC */ 505 L_ADD(time_adj, time_freq); 506 tcp->tc_adjustment = time_adj; 507 #ifdef PPS_SYNC 508 if (pps_valid > 0) 509 pps_valid--; 510 else 511 time_status &= ~(STA_PPSSIGNAL | STA_PPSJITTER | 512 STA_PPSWANDER | STA_PPSERROR); 513 #endif /* PPS_SYNC */ 514 } 515 516 /* 517 * ntp_init() - initialize variables and structures 518 * 519 * This routine must be called after the kernel variables hz and tick 520 * are set or changed and before the next tick interrupt. In this 521 * particular implementation, these values are assumed set elsewhere in 522 * the kernel. The design allows the clock frequency and tick interval 523 * to be changed while the system is running. So, this routine should 524 * probably be integrated with the code that does that. 525 */ 526 static void 527 ntp_init() 528 { 529 530 /* 531 * The following variable must be initialized any time the 532 * kernel variable hz is changed. 533 */ 534 time_tick = NANOSECOND / hz; 535 536 /* 537 * The following variables are initialized only at startup. Only 538 * those structures not cleared by the compiler need to be 539 * initialized, and these only in the simulator. In the actual 540 * kernel, any nonzero values here will quickly evaporate. 541 */ 542 L_CLR(time_offset); 543 L_CLR(time_freq); 544 #ifdef PPS_SYNC 545 pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0; 546 pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0; 547 pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0; 548 pps_fcount = 0; 549 L_CLR(pps_freq); 550 #endif /* PPS_SYNC */ 551 } 552 553 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_FIRST, ntp_init, NULL) 554 555 /* 556 * hardupdate() - local clock update 557 * 558 * This routine is called by ntp_adjtime() to update the local clock 559 * phase and frequency. The implementation is of an adaptive-parameter, 560 * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new 561 * time and frequency offset estimates for each call. If the kernel PPS 562 * discipline code is configured (PPS_SYNC), the PPS signal itself 563 * determines the new time offset, instead of the calling argument. 564 * Presumably, calls to ntp_adjtime() occur only when the caller 565 * believes the local clock is valid within some bound (+-128 ms with 566 * NTP). If the caller's time is far different than the PPS time, an 567 * argument will ensue, and it's not clear who will lose. 568 * 569 * For uncompensated quartz crystal oscillators and nominal update 570 * intervals less than 256 s, operation should be in phase-lock mode, 571 * where the loop is disciplined to phase. For update intervals greater 572 * than 1024 s, operation should be in frequency-lock mode, where the 573 * loop is disciplined to frequency. Between 256 s and 1024 s, the mode 574 * is selected by the STA_MODE status bit. 575 */ 576 static void 577 hardupdate(offset) 578 long offset; /* clock offset (ns) */ 579 { 580 long ltemp, mtemp; 581 l_fp ftemp; 582 583 /* 584 * Select how the phase is to be controlled and from which 585 * source. If the PPS signal is present and enabled to 586 * discipline the time, the PPS offset is used; otherwise, the 587 * argument offset is used. 588 */ 589 if (!(time_status & STA_PLL)) 590 return; 591 ltemp = offset; 592 if (ltemp > MAXPHASE) 593 ltemp = MAXPHASE; 594 else if (ltemp < -MAXPHASE) 595 ltemp = -MAXPHASE; 596 if (!(time_status & STA_PPSTIME && time_status & STA_PPSSIGNAL)) 597 L_LINT(time_offset, ltemp); 598 599 /* 600 * Select how the frequency is to be controlled and in which 601 * mode (PLL or FLL). If the PPS signal is present and enabled 602 * to discipline the frequency, the PPS frequency is used; 603 * otherwise, the argument offset is used to compute it. 604 */ 605 if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) { 606 time_reftime = time_second; 607 return; 608 } 609 if (time_status & STA_FREQHOLD || time_reftime == 0) 610 time_reftime = time_second; 611 mtemp = time_second - time_reftime; 612 L_LINT(ftemp, ltemp); 613 L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1); 614 L_MPY(ftemp, mtemp); 615 L_ADD(time_freq, ftemp); 616 time_status &= ~STA_MODE; 617 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 618 L_LINT(ftemp, (ltemp << 4) / mtemp); 619 L_RSHIFT(ftemp, SHIFT_FLL + 4); 620 L_ADD(time_freq, ftemp); 621 time_status |= STA_MODE; 622 } 623 time_reftime = time_second; 624 if (L_GINT(time_freq) > MAXFREQ) 625 L_LINT(time_freq, MAXFREQ); 626 else if (L_GINT(time_freq) < -MAXFREQ) 627 L_LINT(time_freq, -MAXFREQ); 628 } 629 630 #ifdef PPS_SYNC 631 /* 632 * hardpps() - discipline CPU clock oscillator to external PPS signal 633 * 634 * This routine is called at each PPS interrupt in order to discipline 635 * the CPU clock oscillator to the PPS signal. It measures the PPS phase 636 * and leaves it in a handy spot for the hardclock() routine. It 637 * integrates successive PPS phase differences and calculates the 638 * frequency offset. This is used in hardclock() to discipline the CPU 639 * clock oscillator so that the intrinsic frequency error is cancelled 640 * out. The code requires the caller to capture the time and 641 * architecture-dependent hardware counter values in nanoseconds at the 642 * on-time PPS signal transition. 643 * 644 * Note that, on some Unix systems this routine runs at an interrupt 645 * priority level higher than the timer interrupt routine hardclock(). 646 * Therefore, the variables used are distinct from the hardclock() 647 * variables, except for the actual time and frequency variables, which 648 * are determined by this routine and updated atomically. 649 */ 650 void 651 hardpps(tsp, nsec) 652 struct timespec *tsp; /* time at PPS */ 653 long nsec; /* hardware counter at PPS */ 654 { 655 long u_sec, u_nsec, v_nsec, w_nsec; /* temps */ 656 l_fp ftemp; 657 658 /* 659 * The signal is first processed by a frequency discriminator 660 * which rejects noise and input signals with frequencies 661 * outside the range 1 +-MAXFREQ PPS. If two hits occur in the 662 * same second, we ignore the later hit; if not and a hit occurs 663 * outside the range gate, keep the later hit but do not 664 * process it. 665 */ 666 time_status |= STA_PPSSIGNAL | STA_PPSJITTER; 667 time_status &= ~(STA_PPSWANDER | STA_PPSERROR); 668 pps_valid = PPS_VALID; 669 u_sec = tsp->tv_sec; 670 u_nsec = tsp->tv_nsec; 671 if (u_nsec >= (NANOSECOND >> 1)) { 672 u_nsec -= NANOSECOND; 673 u_sec++; 674 } 675 v_nsec = u_nsec - pps_tf[0].tv_nsec; 676 if (u_sec == pps_tf[0].tv_sec && v_nsec < -MAXFREQ) { 677 return; 678 } 679 pps_tf[2] = pps_tf[1]; 680 pps_tf[1] = pps_tf[0]; 681 pps_tf[0].tv_sec = u_sec; 682 pps_tf[0].tv_nsec = u_nsec; 683 684 /* 685 * Compute the difference between the current and previous 686 * counter values. If the difference exceeds 0.5 s, assume it 687 * has wrapped around, so correct 1.0 s. If the result exceeds 688 * the tick interval, the sample point has crossed a tick 689 * boundary during the last second, so correct the tick. Very 690 * intricate. 691 */ 692 u_nsec = nsec; 693 if (u_nsec > (NANOSECOND >> 1)) 694 u_nsec -= NANOSECOND; 695 else if (u_nsec < -(NANOSECOND >> 1)) 696 u_nsec += NANOSECOND; 697 pps_fcount += u_nsec; 698 if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ) { 699 return; 700 } 701 time_status &= ~STA_PPSJITTER; 702 703 /* 704 * A three-stage median filter is used to help denoise the PPS 705 * time. The median sample becomes the time offset estimate; the 706 * difference between the other two samples becomes the time 707 * dispersion (jitter) estimate. 708 */ 709 if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) { 710 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) { 711 v_nsec = pps_tf[1].tv_nsec; /* 0 1 2 */ 712 u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec; 713 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) { 714 v_nsec = pps_tf[0].tv_nsec; /* 2 0 1 */ 715 u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec; 716 } else { 717 v_nsec = pps_tf[2].tv_nsec; /* 0 2 1 */ 718 u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec; 719 } 720 } else { 721 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) { 722 v_nsec = pps_tf[1].tv_nsec; /* 2 1 0 */ 723 u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec; 724 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) { 725 v_nsec = pps_tf[0].tv_nsec; /* 1 0 2 */ 726 u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec; 727 } else { 728 v_nsec = pps_tf[2].tv_nsec; /* 1 2 0 */ 729 u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec; 730 } 731 } 732 733 /* 734 * Nominal jitter is due to PPS signal noise and interrupt 735 * latency. If it exceeds the popcorn threshold, 736 * the sample is discarded. otherwise, if so enabled, the time 737 * offset is updated. We can tolerate a modest loss of data here 738 * without degrading time accuracy. 739 */ 740 if (u_nsec > (pps_jitter << PPS_POPCORN)) { 741 time_status |= STA_PPSJITTER; 742 pps_jitcnt++; 743 } else if (time_status & STA_PPSTIME) { 744 L_LINT(time_offset, -v_nsec); 745 L_LINT(pps_offset, -v_nsec); 746 747 if (pps_letgo >= 2) { 748 L_LINT(ftemp, -v_nsec); 749 L_RSHIFT(ftemp, (pps_shift * 2)); 750 L_ADD(ftemp, time_freq); 751 w_nsec = L_GINT(ftemp); 752 if (w_nsec > MAXFREQ) 753 L_LINT(ftemp, MAXFREQ); 754 else if (w_nsec < -MAXFREQ) 755 L_LINT(ftemp, -MAXFREQ); 756 time_freq = ftemp; 757 } 758 759 } 760 pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG; 761 u_sec = pps_tf[0].tv_sec - pps_lastsec; 762 if (u_sec < (1 << pps_shift)) 763 return; 764 765 /* 766 * At the end of the calibration interval the difference between 767 * the first and last counter values becomes the scaled 768 * frequency. It will later be divided by the length of the 769 * interval to determine the frequency update. If the frequency 770 * exceeds a sanity threshold, or if the actual calibration 771 * interval is not equal to the expected length, the data are 772 * discarded. We can tolerate a modest loss of data here without 773 * degrading frequency ccuracy. 774 */ 775 pps_calcnt++; 776 v_nsec = -pps_fcount; 777 pps_lastsec = pps_tf[0].tv_sec; 778 pps_fcount = 0; 779 u_nsec = MAXFREQ << pps_shift; 780 if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 << 781 pps_shift)) { 782 time_status |= STA_PPSERROR; 783 pps_errcnt++; 784 return; 785 } 786 787 /* 788 * Here the raw frequency offset and wander (stability) is 789 * calculated. If the wander is less than the wander threshold 790 * for four consecutive averaging intervals, the interval is 791 * doubled; if it is greater than the threshold for four 792 * consecutive intervals, the interval is halved. The scaled 793 * frequency offset is converted to frequency offset. The 794 * stability metric is calculated as the average of recent 795 * frequency changes, but is used only for performance 796 * monitoring. 797 */ 798 L_LINT(ftemp, v_nsec); 799 L_RSHIFT(ftemp, pps_shift); 800 L_SUB(ftemp, pps_freq); 801 u_nsec = L_GINT(ftemp); 802 if (u_nsec > PPS_MAXWANDER) { 803 L_LINT(ftemp, PPS_MAXWANDER); 804 pps_intcnt--; 805 time_status |= STA_PPSWANDER; 806 pps_stbcnt++; 807 } else if (u_nsec < -PPS_MAXWANDER) { 808 L_LINT(ftemp, -PPS_MAXWANDER); 809 pps_intcnt--; 810 time_status |= STA_PPSWANDER; 811 pps_stbcnt++; 812 } else { 813 pps_intcnt++; 814 } 815 if (!(time_status & STA_PPSFREQ)) { 816 pps_intcnt = 0; 817 pps_shift = PPS_FAVG; 818 } else if (pps_shift > pps_shiftmax) { 819 /* If we lowered pps_shiftmax */ 820 pps_shift = pps_shiftmax; 821 pps_intcnt = 0; 822 } else if (pps_intcnt >= 4) { 823 pps_intcnt = 4; 824 if (pps_shift < pps_shiftmax) { 825 pps_shift++; 826 pps_intcnt = 0; 827 } 828 } else if (pps_intcnt <= -4) { 829 pps_intcnt = -4; 830 if (pps_shift > PPS_FAVG) { 831 pps_shift--; 832 pps_intcnt = 0; 833 } 834 } 835 if (u_nsec < 0) 836 u_nsec = -u_nsec; 837 pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG; 838 839 /* 840 * The PPS frequency is recalculated and clamped to the maximum 841 * MAXFREQ. If enabled, the system clock frequency is updated as 842 * well. 843 */ 844 L_ADD(pps_freq, ftemp); 845 u_nsec = L_GINT(pps_freq); 846 if (u_nsec > MAXFREQ) 847 L_LINT(pps_freq, MAXFREQ); 848 else if (u_nsec < -MAXFREQ) 849 L_LINT(pps_freq, -MAXFREQ); 850 if ((time_status & (STA_PPSFREQ | STA_PPSTIME)) == STA_PPSFREQ) { 851 pps_letgo = 0; 852 time_freq = pps_freq; 853 } else if (time_status & STA_PPSTIME) { 854 if (pps_letgo < 2) 855 pps_letgo++; 856 } 857 } 858 #endif /* PPS_SYNC */ 859