sys/kern/kern_ntptime.c

   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("$FreeBSD$");
  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/priv.h>
  43 #include <sys/proc.h>
  44 #include <sys/lock.h>
  45 #include <sys/mutex.h>
  46 #include <sys/time.h>
  47 #include <sys/timex.h>
  48 #include <sys/timetc.h>
  49 #include <sys/timepps.h>
  50 #include <sys/syscallsubr.h>
  51 #include <sys/sysctl.h>
  52
  53 /*
  54  * Single-precision macros for 64-bit machines
  55  */
  56 typedef int64_t l_fp;
  57 #define L_ADD(v, u)     ((v) += (u))
  58 #define L_SUB(v, u)     ((v) -= (u))
  59 #define L_ADDHI(v, a)   ((v) += (int64_t)(a) << 32)
  60 #define L_NEG(v)        ((v) = -(v))
  61 #define L_RSHIFT(v, n) \
  62         do { \
  63                 if ((v) < 0) \
  64                         (v) = -(-(v) >> (n)); \
  65                 else \
  66                         (v) = (v) >> (n); \
  67         } while (0)
  68 #define L_MPY(v, a)     ((v) *= (a))
  69 #define L_CLR(v)        ((v) = 0)
  70 #define L_ISNEG(v)      ((v) < 0)
  71 #define L_LINT(v, a)    ((v) = (int64_t)(a) << 32)
  72 #define L_GINT(v)       ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
  73
  74 /*
  75  * Generic NTP kernel interface
  76  *
  77  * These routines constitute the Network Time Protocol (NTP) interfaces
  78  * for user and daemon application programs. The ntp_gettime() routine
  79  * provides the time, maximum error (synch distance) and estimated error
  80  * (dispersion) to client user application programs. The ntp_adjtime()
  81  * routine is used by the NTP daemon to adjust the system clock to an
  82  * externally derived time. The time offset and related variables set by
  83  * this routine are used by other routines in this module to adjust the
  84  * phase and frequency of the clock discipline loop which controls the
  85  * system clock.
  86  *
  87  * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
  88  * defined), the time at each tick interrupt is derived directly from
  89  * the kernel time variable. When the kernel time is reckoned in
  90  * microseconds, (NTP_NANO undefined), the time is derived from the
  91  * kernel time variable together with a variable representing the
  92  * leftover nanoseconds at the last tick interrupt. In either case, the
  93  * current nanosecond time is reckoned from these values plus an
  94  * interpolated value derived by the clock routines in another
  95  * architecture-specific module. The interpolation can use either a
  96  * dedicated counter or a processor cycle counter (PCC) implemented in
  97  * some architectures.
  98  *
  99  * Note that all routines must run at priority splclock or higher.
 100  */
 101 /*
 102  * Phase/frequency-lock loop (PLL/FLL) definitions
 103  *
 104  * The nanosecond clock discipline uses two variable types, time
 105  * variables and frequency variables. Both types are represented as 64-
 106  * bit fixed-point quantities with the decimal point between two 32-bit
 107  * halves. On a 32-bit machine, each half is represented as a single
 108  * word and mathematical operations are done using multiple-precision
 109  * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
 110  * used.
 111  *
 112  * A time variable is a signed 64-bit fixed-point number in ns and
 113  * fraction. It represents the remaining time offset to be amortized
 114  * over succeeding tick interrupts. The maximum time offset is about
 115  * 0.5 s and the resolution is about 2.3e-10 ns.
 116  *
 117  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
 118  *  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
 119  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 120  * |s s s|                       ns                                |
 121  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 122  * |                        fraction                               |
 123  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 124  *
 125  * A frequency variable is a signed 64-bit fixed-point number in ns/s
 126  * and fraction. It represents the ns and fraction to be added to the
 127  * kernel time variable at each second. The maximum frequency offset is
 128  * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
 129  *
 130  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
 131  *  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
 132  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 133  * |s s s s s s s s s s s s s|            ns/s                     |
 134  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 135  * |                        fraction                               |
 136  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 137  */
 138 /*
 139  * The following variables establish the state of the PLL/FLL and the
 140  * residual time and frequency offset of the local clock.
 141  */
 142 #define SHIFT_PLL       4               /* PLL loop gain (shift) */
 143 #define SHIFT_FLL       2               /* FLL loop gain (shift) */
 144
 145 static int time_state = TIME_OK;        /* clock state */
 146 static int time_status = STA_UNSYNC;    /* clock status bits */
 147 static long time_tai;                   /* TAI offset (s) */
 148 static long time_monitor;               /* last time offset scaled (ns) */
 149 static long time_constant;              /* poll interval (shift) (s) */
 150 static long time_precision = 1;         /* clock precision (ns) */
 151 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
 152 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
 153 static long time_reftime;               /* time at last adjustment (s) */
 154 static l_fp time_offset;                /* time offset (ns) */
 155 static l_fp time_freq;                  /* frequency offset (ns/s) */
 156 static l_fp time_adj;                   /* tick adjust (ns/s) */
 157
 158 static int64_t time_adjtime;            /* correction from adjtime(2) (usec) */
 159
 160 #ifdef PPS_SYNC
 161 /*
 162  * The following variables are used when a pulse-per-second (PPS) signal
 163  * is available and connected via a modem control lead. They establish
 164  * the engineering parameters of the clock discipline loop when
 165  * controlled by the PPS signal.
 166  */
 167 #define PPS_FAVG        2               /* min freq avg interval (s) (shift) */
 168 #define PPS_FAVGDEF     8               /* default freq avg int (s) (shift) */
 169 #define PPS_FAVGMAX     15              /* max freq avg interval (s) (shift) */
 170 #define PPS_PAVG        4               /* phase avg interval (s) (shift) */
 171 #define PPS_VALID       120             /* PPS signal watchdog max (s) */
 172 #define PPS_MAXWANDER   100000          /* max PPS wander (ns/s) */
 173 #define PPS_POPCORN     2               /* popcorn spike threshold (shift) */
 174
 175 static struct timespec pps_tf[3];       /* phase median filter */
 176 static l_fp pps_freq;                   /* scaled frequency offset (ns/s) */
 177 static long pps_fcount;                 /* frequency accumulator */
 178 static long pps_jitter;                 /* nominal jitter (ns) */
 179 static long pps_stabil;                 /* nominal stability (scaled ns/s) */
 180 static long pps_lastsec;                /* time at last calibration (s) */
 181 static int pps_valid;                   /* signal watchdog counter */
 182 static int pps_shift = PPS_FAVG;        /* interval duration (s) (shift) */
 183 static int pps_shiftmax = PPS_FAVGDEF;  /* max interval duration (s) (shift) */
 184 static int pps_intcnt;                  /* wander counter */
 185
 186 /*
 187  * PPS signal quality monitors
 188  */
 189 static long pps_calcnt;                 /* calibration intervals */
 190 static long pps_jitcnt;                 /* jitter limit exceeded */
 191 static long pps_stbcnt;                 /* stability limit exceeded */
 192 static long pps_errcnt;                 /* calibration errors */
 193 #endif /* PPS_SYNC */
 194 /*
 195  * End of phase/frequency-lock loop (PLL/FLL) definitions
 196  */
 197
 198 static void ntp_init(void);
 199 static void hardupdate(long offset);
 200 static void ntp_gettime1(struct ntptimeval *ntvp);
 201
 202 static void
 203 ntp_gettime1(struct ntptimeval *ntvp)
 204 {
 205         struct timespec atv;    /* nanosecond time */
 206
 207         GIANT_REQUIRED;
 208
 209         nanotime(&atv);
 210         ntvp->time.tv_sec = atv.tv_sec;
 211         ntvp->time.tv_nsec = atv.tv_nsec;
 212         ntvp->maxerror = time_maxerror;
 213         ntvp->esterror = time_esterror;
 214         ntvp->tai = time_tai;
 215         ntvp->time_state = time_state;
 216
 217         /*
 218          * Status word error decode. If any of these conditions occur,
 219          * an error is returned, instead of the status word. Most
 220          * applications will care only about the fact the system clock
 221          * may not be trusted, not about the details.
 222          *
 223          * Hardware or software error
 224          */
 225         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
 226
 227         /*
 228          * PPS signal lost when either time or frequency synchronization
 229          * requested
 230          */
 231             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
 232             !(time_status & STA_PPSSIGNAL)) ||
 233
 234         /*
 235          * PPS jitter exceeded when time synchronization requested
 236          */
 237             (time_status & STA_PPSTIME &&
 238             time_status & STA_PPSJITTER) ||
 239
 240         /*
 241          * PPS wander exceeded or calibration error when frequency
 242          * synchronization requested
 243          */
 244             (time_status & STA_PPSFREQ &&
 245             time_status & (STA_PPSWANDER | STA_PPSERROR)))
 246                 ntvp->time_state = TIME_ERROR;
 247 }
 248
 249 /*
 250  * ntp_gettime() - NTP user application interface
 251  *
 252  * See the timex.h header file for synopsis and API description.  Note that
 253  * the TAI offset is returned in the ntvtimeval.tai structure member.
 254  */
 255 #ifndef _SYS_SYSPROTO_H_
 256 struct ntp_gettime_args {
 257         struct ntptimeval *ntvp;
 258 };
 259 #endif
 260 /* ARGSUSED */
 261 int
 262 ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
 263 {
 264         struct ntptimeval ntv;
 265
 266         mtx_lock(&Giant);
 267         ntp_gettime1(&ntv);
 268         mtx_unlock(&Giant);
 269
 270         td->td_retval[0] = ntv.time_state;
 271         return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
 272 }
 273
 274 static int
 275 ntp_sysctl(SYSCTL_HANDLER_ARGS)
 276 {
 277         struct ntptimeval ntv;  /* temporary structure */
 278
 279         ntp_gettime1(&ntv);
 280
 281         return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
 282 }
 283
 284 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
 285 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
 286         0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
 287
 288 #ifdef PPS_SYNC
 289 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
 290 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
 291 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD, &time_monitor, 0, "");
 292
 293 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
 294 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
 295 #endif
 296
 297 /*
 298  * ntp_adjtime() - NTP daemon application interface
 299  *
 300  * See the timex.h header file for synopsis and API description.  Note that
 301  * the timex.constant structure member has a dual purpose to set the time
 302  * constant and to set the TAI offset.
 303  */
 304 #ifndef _SYS_SYSPROTO_H_
 305 struct ntp_adjtime_args {
 306         struct timex *tp;
 307 };
 308 #endif
 309
 310 int
 311 ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
 312 {
 313         struct timex ntv;       /* temporary structure */
 314         long freq;              /* frequency ns/s) */
 315         int modes;              /* mode bits from structure */
 316         int s;                  /* caller priority */
 317         int error;
 318
 319         error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
 320         if (error)
 321                 return(error);
 322
 323         /*
 324          * Update selected clock variables - only the superuser can
 325          * change anything. Note that there is no error checking here on
 326          * the assumption the superuser should know what it is doing.
 327          * Note that either the time constant or TAI offset are loaded
 328          * from the ntv.constant member, depending on the mode bits. If
 329          * the STA_PLL bit in the status word is cleared, the state and
 330          * status words are reset to the initial values at boot.
 331          */
 332         mtx_lock(&Giant);
 333         modes = ntv.modes;
 334         if (modes)
 335                 error = priv_check(td, PRIV_NTP_ADJTIME);
 336         if (error)
 337                 goto done2;
 338         s = splclock();
 339         if (modes & MOD_MAXERROR)
 340                 time_maxerror = ntv.maxerror;
 341         if (modes & MOD_ESTERROR)
 342                 time_esterror = ntv.esterror;
 343         if (modes & MOD_STATUS) {
 344                 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
 345                         time_state = TIME_OK;
 346                         time_status = STA_UNSYNC;
 347 #ifdef PPS_SYNC
 348                         pps_shift = PPS_FAVG;
 349 #endif /* PPS_SYNC */
 350                 }
 351                 time_status &= STA_RONLY;
 352                 time_status |= ntv.status & ~STA_RONLY;
 353         }
 354         if (modes & MOD_TIMECONST) {
 355                 if (ntv.constant < 0)
 356                         time_constant = 0;
 357                 else if (ntv.constant > MAXTC)
 358                         time_constant = MAXTC;
 359                 else
 360                         time_constant = ntv.constant;
 361         }
 362         if (modes & MOD_TAI) {
 363                 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
 364                         time_tai = ntv.constant;
 365         }
 366 #ifdef PPS_SYNC
 367         if (modes & MOD_PPSMAX) {
 368                 if (ntv.shift < PPS_FAVG)
 369                         pps_shiftmax = PPS_FAVG;
 370                 else if (ntv.shift > PPS_FAVGMAX)
 371                         pps_shiftmax = PPS_FAVGMAX;
 372                 else
 373                         pps_shiftmax = ntv.shift;
 374         }
 375 #endif /* PPS_SYNC */
 376         if (modes & MOD_NANO)
 377                 time_status |= STA_NANO;
 378         if (modes & MOD_MICRO)
 379                 time_status &= ~STA_NANO;
 380         if (modes & MOD_CLKB)
 381                 time_status |= STA_CLK;
 382         if (modes & MOD_CLKA)
 383                 time_status &= ~STA_CLK;
 384         if (modes & MOD_FREQUENCY) {
 385                 freq = (ntv.freq * 1000LL) >> 16;
 386                 if (freq > MAXFREQ)
 387                         L_LINT(time_freq, MAXFREQ);
 388                 else if (freq < -MAXFREQ)
 389                         L_LINT(time_freq, -MAXFREQ);
 390                 else {
 391                         /*
 392                          * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
 393                          * time_freq is [ns/s * 2^32]
 394                          */
 395                         time_freq = ntv.freq * 1000LL * 65536LL;
 396                 }
 397 #ifdef PPS_SYNC
 398                 pps_freq = time_freq;
 399 #endif /* PPS_SYNC */
 400         }
 401         if (modes & MOD_OFFSET) {
 402                 if (time_status & STA_NANO)
 403                         hardupdate(ntv.offset);
 404                 else
 405                         hardupdate(ntv.offset * 1000);
 406         }
 407
 408         /*
 409          * Retrieve all clock variables. Note that the TAI offset is
 410          * returned only by ntp_gettime();
 411          */
 412         if (time_status & STA_NANO)
 413                 ntv.offset = L_GINT(time_offset);
 414         else
 415                 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
 416         ntv.freq = L_GINT((time_freq / 1000LL) << 16);
 417         ntv.maxerror = time_maxerror;
 418         ntv.esterror = time_esterror;
 419         ntv.status = time_status;
 420         ntv.constant = time_constant;
 421         if (time_status & STA_NANO)
 422                 ntv.precision = time_precision;
 423         else
 424                 ntv.precision = time_precision / 1000;
 425         ntv.tolerance = MAXFREQ * SCALE_PPM;
 426 #ifdef PPS_SYNC
 427         ntv.shift = pps_shift;
 428         ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
 429         if (time_status & STA_NANO)
 430                 ntv.jitter = pps_jitter;
 431         else
 432                 ntv.jitter = pps_jitter / 1000;
 433         ntv.stabil = pps_stabil;
 434         ntv.calcnt = pps_calcnt;
 435         ntv.errcnt = pps_errcnt;
 436         ntv.jitcnt = pps_jitcnt;
 437         ntv.stbcnt = pps_stbcnt;
 438 #endif /* PPS_SYNC */
 439         splx(s);
 440
 441         error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
 442         if (error)
 443                 goto done2;
 444
 445         /*
 446          * Status word error decode. See comments in
 447          * ntp_gettime() routine.
 448          */
 449         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
 450             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
 451             !(time_status & STA_PPSSIGNAL)) ||
 452             (time_status & STA_PPSTIME &&
 453             time_status & STA_PPSJITTER) ||
 454             (time_status & STA_PPSFREQ &&
 455             time_status & (STA_PPSWANDER | STA_PPSERROR))) {
 456                 td->td_retval[0] = TIME_ERROR;
 457         } else {
 458                 td->td_retval[0] = time_state;
 459         }
 460 done2:
 461         mtx_unlock(&Giant);
 462         return (error);
 463 }
 464
 465 /*
 466  * second_overflow() - called after ntp_tick_adjust()
 467  *
 468  * This routine is ordinarily called immediately following the above
 469  * routine ntp_tick_adjust(). While these two routines are normally
 470  * combined, they are separated here only for the purposes of
 471  * simulation.
 472  */
 473 void
 474 ntp_update_second(int64_t *adjustment, time_t *newsec)
 475 {
 476         int tickrate;
 477         l_fp ftemp;             /* 32/64-bit temporary */
 478
 479         /*
 480          * On rollover of the second both the nanosecond and microsecond
 481          * clocks are updated and the state machine cranked as
 482          * necessary. The phase adjustment to be used for the next
 483          * second is calculated and the maximum error is increased by
 484          * the tolerance.
 485          */
 486         time_maxerror += MAXFREQ / 1000;
 487
 488         /*
 489          * Leap second processing. If in leap-insert state at
 490          * the end of the day, the system clock is set back one
 491          * second; if in leap-delete state, the system clock is
 492          * set ahead one second. The nano_time() routine or
 493          * external clock driver will insure that reported time
 494          * is always monotonic.
 495          */
 496         switch (time_state) {
 497
 498                 /*
 499                  * No warning.
 500                  */
 501                 case TIME_OK:
 502                 if (time_status & STA_INS)
 503                         time_state = TIME_INS;
 504                 else if (time_status & STA_DEL)
 505                         time_state = TIME_DEL;
 506                 break;
 507
 508                 /*
 509                  * Insert second 23:59:60 following second
 510                  * 23:59:59.
 511                  */
 512                 case TIME_INS:
 513                 if (!(time_status & STA_INS))
 514                         time_state = TIME_OK;
 515                 else if ((*newsec) % 86400 == 0) {
 516                         (*newsec)--;
 517                         time_state = TIME_OOP;
 518                         time_tai++;
 519                 }
 520                 break;
 521
 522                 /*
 523                  * Delete second 23:59:59.
 524                  */
 525                 case TIME_DEL:
 526                 if (!(time_status & STA_DEL))
 527                         time_state = TIME_OK;
 528                 else if (((*newsec) + 1) % 86400 == 0) {
 529                         (*newsec)++;
 530                         time_tai--;
 531                         time_state = TIME_WAIT;
 532                 }
 533                 break;
 534
 535                 /*
 536                  * Insert second in progress.
 537                  */
 538                 case TIME_OOP:
 539                         time_state = TIME_WAIT;
 540                 break;
 541
 542                 /*
 543                  * Wait for status bits to clear.
 544                  */
 545                 case TIME_WAIT:
 546                 if (!(time_status & (STA_INS | STA_DEL)))
 547                         time_state = TIME_OK;
 548         }
 549
 550         /*
 551          * Compute the total time adjustment for the next second
 552          * in ns. The offset is reduced by a factor depending on
 553          * whether the PPS signal is operating. Note that the
 554          * value is in effect scaled by the clock frequency,
 555          * since the adjustment is added at each tick interrupt.
 556          */
 557         ftemp = time_offset;
 558 #ifdef PPS_SYNC
 559         /* XXX even if PPS signal dies we should finish adjustment ? */
 560         if (time_status & STA_PPSTIME && time_status &
 561             STA_PPSSIGNAL)
 562                 L_RSHIFT(ftemp, pps_shift);
 563         else
 564                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
 565 #else
 566                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
 567 #endif /* PPS_SYNC */
 568         time_adj = ftemp;
 569         L_SUB(time_offset, ftemp);
 570         L_ADD(time_adj, time_freq);
 571
 572         /*
 573          * Apply any correction from adjtime(2).  If more than one second
 574          * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
 575          * until the last second is slewed the final < 500 usecs.
 576          */
 577         if (time_adjtime != 0) {
 578                 if (time_adjtime > 1000000)
 579                         tickrate = 5000;
 580                 else if (time_adjtime < -1000000)
 581                         tickrate = -5000;
 582                 else if (time_adjtime > 500)
 583                         tickrate = 500;
 584                 else if (time_adjtime < -500)
 585                         tickrate = -500;
 586                 else
 587                         tickrate = time_adjtime;
 588                 time_adjtime -= tickrate;
 589                 L_LINT(ftemp, tickrate * 1000);
 590                 L_ADD(time_adj, ftemp);
 591         }
 592         *adjustment = time_adj;
 593
 594 #ifdef PPS_SYNC
 595         if (pps_valid > 0)
 596                 pps_valid--;
 597         else
 598                 time_status &= ~STA_PPSSIGNAL;
 599 #endif /* PPS_SYNC */
 600 }
 601
 602 /*
 603  * ntp_init() - initialize variables and structures
 604  *
 605  * This routine must be called after the kernel variables hz and tick
 606  * are set or changed and before the next tick interrupt. In this
 607  * particular implementation, these values are assumed set elsewhere in
 608  * the kernel. The design allows the clock frequency and tick interval
 609  * to be changed while the system is running. So, this routine should
 610  * probably be integrated with the code that does that.
 611  */
 612 static void
 613 ntp_init()
 614 {
 615
 616         /*
 617          * The following variables are initialized only at startup. Only
 618          * those structures not cleared by the compiler need to be
 619          * initialized, and these only in the simulator. In the actual
 620          * kernel, any nonzero values here will quickly evaporate.
 621          */
 622         L_CLR(time_offset);
 623         L_CLR(time_freq);
 624 #ifdef PPS_SYNC
 625         pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
 626         pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
 627         pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
 628         pps_fcount = 0;
 629         L_CLR(pps_freq);
 630 #endif /* PPS_SYNC */
 631 }
 632
 633 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL);
 634
 635 /*
 636  * hardupdate() - local clock update
 637  *
 638  * This routine is called by ntp_adjtime() to update the local clock
 639  * phase and frequency. The implementation is of an adaptive-parameter,
 640  * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
 641  * time and frequency offset estimates for each call. If the kernel PPS
 642  * discipline code is configured (PPS_SYNC), the PPS signal itself
 643  * determines the new time offset, instead of the calling argument.
 644  * Presumably, calls to ntp_adjtime() occur only when the caller
 645  * believes the local clock is valid within some bound (+-128 ms with
 646  * NTP). If the caller's time is far different than the PPS time, an
 647  * argument will ensue, and it's not clear who will lose.
 648  *
 649  * For uncompensated quartz crystal oscillators and nominal update
 650  * intervals less than 256 s, operation should be in phase-lock mode,
 651  * where the loop is disciplined to phase. For update intervals greater
 652  * than 1024 s, operation should be in frequency-lock mode, where the
 653  * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
 654  * is selected by the STA_MODE status bit.
 655  */
 656 static void
 657 hardupdate(offset)
 658         long offset;            /* clock offset (ns) */
 659 {
 660         long mtemp;
 661         l_fp ftemp;
 662
 663         /*
 664          * Select how the phase is to be controlled and from which
 665          * source. If the PPS signal is present and enabled to
 666          * discipline the time, the PPS offset is used; otherwise, the
 667          * argument offset is used.
 668          */
 669         if (!(time_status & STA_PLL))
 670                 return;
 671         if (!(time_status & STA_PPSTIME && time_status &
 672             STA_PPSSIGNAL)) {
 673                 if (offset > MAXPHASE)
 674                         time_monitor = MAXPHASE;
 675                 else if (offset < -MAXPHASE)
 676                         time_monitor = -MAXPHASE;
 677                 else
 678                         time_monitor = offset;
 679                 L_LINT(time_offset, time_monitor);
 680         }
 681
 682         /*
 683          * Select how the frequency is to be controlled and in which
 684          * mode (PLL or FLL). If the PPS signal is present and enabled
 685          * to discipline the frequency, the PPS frequency is used;
 686          * otherwise, the argument offset is used to compute it.
 687          */
 688         if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
 689                 time_reftime = time_second;
 690                 return;
 691         }
 692         if (time_status & STA_FREQHOLD || time_reftime == 0)
 693                 time_reftime = time_second;
 694         mtemp = time_second - time_reftime;
 695         L_LINT(ftemp, time_monitor);
 696         L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
 697         L_MPY(ftemp, mtemp);
 698         L_ADD(time_freq, ftemp);
 699         time_status &= ~STA_MODE;
 700         if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
 701             MAXSEC)) {
 702                 L_LINT(ftemp, (time_monitor << 4) / mtemp);
 703                 L_RSHIFT(ftemp, SHIFT_FLL + 4);
 704                 L_ADD(time_freq, ftemp);
 705                 time_status |= STA_MODE;
 706         }
 707         time_reftime = time_second;
 708         if (L_GINT(time_freq) > MAXFREQ)
 709                 L_LINT(time_freq, MAXFREQ);
 710         else if (L_GINT(time_freq) < -MAXFREQ)
 711                 L_LINT(time_freq, -MAXFREQ);
 712 }
 713
 714 #ifdef PPS_SYNC
 715 /*
 716  * hardpps() - discipline CPU clock oscillator to external PPS signal
 717  *
 718  * This routine is called at each PPS interrupt in order to discipline
 719  * the CPU clock oscillator to the PPS signal. There are two independent
 720  * first-order feedback loops, one for the phase, the other for the
 721  * frequency. The phase loop measures and grooms the PPS phase offset
 722  * and leaves it in a handy spot for the seconds overflow routine. The
 723  * frequency loop averages successive PPS phase differences and
 724  * calculates the PPS frequency offset, which is also processed by the
 725  * seconds overflow routine. The code requires the caller to capture the
 726  * time and architecture-dependent hardware counter values in
 727  * nanoseconds at the on-time PPS signal transition.
 728  *
 729  * Note that, on some Unix systems this routine runs at an interrupt
 730  * priority level higher than the timer interrupt routine hardclock().
 731  * Therefore, the variables used are distinct from the hardclock()
 732  * variables, except for the actual time and frequency variables, which
 733  * are determined by this routine and updated atomically.
 734  */
 735 void
 736 hardpps(tsp, nsec)
 737         struct timespec *tsp;   /* time at PPS */
 738         long nsec;              /* hardware counter at PPS */
 739 {
 740         long u_sec, u_nsec, v_nsec; /* temps */
 741         l_fp ftemp;
 742
 743         /*
 744          * The signal is first processed by a range gate and frequency
 745          * discriminator. The range gate rejects noise spikes outside
 746          * the range +-500 us. The frequency discriminator rejects input
 747          * signals with apparent frequency outside the range 1 +-500
 748          * PPM. If two hits occur in the same second, we ignore the
 749          * later hit; if not and a hit occurs outside the range gate,
 750          * keep the later hit for later comparison, but do not process
 751          * it.
 752          */
 753         time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
 754         time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
 755         pps_valid = PPS_VALID;
 756         u_sec = tsp->tv_sec;
 757         u_nsec = tsp->tv_nsec;
 758         if (u_nsec >= (NANOSECOND >> 1)) {
 759                 u_nsec -= NANOSECOND;
 760                 u_sec++;
 761         }
 762         v_nsec = u_nsec - pps_tf[0].tv_nsec;
 763         if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
 764             MAXFREQ)
 765                 return;
 766         pps_tf[2] = pps_tf[1];
 767         pps_tf[1] = pps_tf[0];
 768         pps_tf[0].tv_sec = u_sec;
 769         pps_tf[0].tv_nsec = u_nsec;
 770
 771         /*
 772          * Compute the difference between the current and previous
 773          * counter values. If the difference exceeds 0.5 s, assume it
 774          * has wrapped around, so correct 1.0 s. If the result exceeds
 775          * the tick interval, the sample point has crossed a tick
 776          * boundary during the last second, so correct the tick. Very
 777          * intricate.
 778          */
 779         u_nsec = nsec;
 780         if (u_nsec > (NANOSECOND >> 1))
 781                 u_nsec -= NANOSECOND;
 782         else if (u_nsec < -(NANOSECOND >> 1))
 783                 u_nsec += NANOSECOND;
 784         pps_fcount += u_nsec;
 785         if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
 786                 return;
 787         time_status &= ~STA_PPSJITTER;
 788
 789         /*
 790          * A three-stage median filter is used to help denoise the PPS
 791          * time. The median sample becomes the time offset estimate; the
 792          * difference between the other two samples becomes the time
 793          * dispersion (jitter) estimate.
 794          */
 795         if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
 796                 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
 797                         v_nsec = pps_tf[1].tv_nsec;     /* 0 1 2 */
 798                         u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
 799                 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
 800                         v_nsec = pps_tf[0].tv_nsec;     /* 2 0 1 */
 801                         u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
 802                 } else {
 803                         v_nsec = pps_tf[2].tv_nsec;     /* 0 2 1 */
 804                         u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
 805                 }
 806         } else {
 807                 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
 808                         v_nsec = pps_tf[1].tv_nsec;     /* 2 1 0 */
 809                         u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
 810                 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
 811                         v_nsec = pps_tf[0].tv_nsec;     /* 1 0 2 */
 812                         u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
 813                 } else {
 814                         v_nsec = pps_tf[2].tv_nsec;     /* 1 2 0 */
 815                         u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
 816                 }
 817         }
 818
 819         /*
 820          * Nominal jitter is due to PPS signal noise and interrupt
 821          * latency. If it exceeds the popcorn threshold, the sample is
 822          * discarded. otherwise, if so enabled, the time offset is
 823          * updated. We can tolerate a modest loss of data here without
 824          * much degrading time accuracy.
 825          */
 826         if (u_nsec > (pps_jitter << PPS_POPCORN)) {
 827                 time_status |= STA_PPSJITTER;
 828                 pps_jitcnt++;
 829         } else if (time_status & STA_PPSTIME) {
 830                 time_monitor = -v_nsec;
 831                 L_LINT(time_offset, time_monitor);
 832         }
 833         pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
 834         u_sec = pps_tf[0].tv_sec - pps_lastsec;
 835         if (u_sec < (1 << pps_shift))
 836                 return;
 837
 838         /*
 839          * At the end of the calibration interval the difference between
 840          * the first and last counter values becomes the scaled
 841          * frequency. It will later be divided by the length of the
 842          * interval to determine the frequency update. If the frequency
 843          * exceeds a sanity threshold, or if the actual calibration
 844          * interval is not equal to the expected length, the data are
 845          * discarded. We can tolerate a modest loss of data here without
 846          * much degrading frequency accuracy.
 847          */
 848         pps_calcnt++;
 849         v_nsec = -pps_fcount;
 850         pps_lastsec = pps_tf[0].tv_sec;
 851         pps_fcount = 0;
 852         u_nsec = MAXFREQ << pps_shift;
 853         if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
 854             pps_shift)) {
 855                 time_status |= STA_PPSERROR;
 856                 pps_errcnt++;
 857                 return;
 858         }
 859
 860         /*
 861          * Here the raw frequency offset and wander (stability) is
 862          * calculated. If the wander is less than the wander threshold
 863          * for four consecutive averaging intervals, the interval is
 864          * doubled; if it is greater than the threshold for four
 865          * consecutive intervals, the interval is halved. The scaled
 866          * frequency offset is converted to frequency offset. The
 867          * stability metric is calculated as the average of recent
 868          * frequency changes, but is used only for performance
 869          * monitoring.
 870          */
 871         L_LINT(ftemp, v_nsec);
 872         L_RSHIFT(ftemp, pps_shift);
 873         L_SUB(ftemp, pps_freq);
 874         u_nsec = L_GINT(ftemp);
 875         if (u_nsec > PPS_MAXWANDER) {
 876                 L_LINT(ftemp, PPS_MAXWANDER);
 877                 pps_intcnt--;
 878                 time_status |= STA_PPSWANDER;
 879                 pps_stbcnt++;
 880         } else if (u_nsec < -PPS_MAXWANDER) {
 881                 L_LINT(ftemp, -PPS_MAXWANDER);
 882                 pps_intcnt--;
 883                 time_status |= STA_PPSWANDER;
 884                 pps_stbcnt++;
 885         } else {
 886                 pps_intcnt++;
 887         }
 888         if (pps_intcnt >= 4) {
 889                 pps_intcnt = 4;
 890                 if (pps_shift < pps_shiftmax) {
 891                         pps_shift++;
 892                         pps_intcnt = 0;
 893                 }
 894         } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
 895                 pps_intcnt = -4;
 896                 if (pps_shift > PPS_FAVG) {
 897                         pps_shift--;
 898                         pps_intcnt = 0;
 899                 }
 900         }
 901         if (u_nsec < 0)
 902                 u_nsec = -u_nsec;
 903         pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
 904
 905         /*
 906          * The PPS frequency is recalculated and clamped to the maximum
 907          * MAXFREQ. If enabled, the system clock frequency is updated as
 908          * well.
 909          */
 910         L_ADD(pps_freq, ftemp);
 911         u_nsec = L_GINT(pps_freq);
 912         if (u_nsec > MAXFREQ)
 913                 L_LINT(pps_freq, MAXFREQ);
 914         else if (u_nsec < -MAXFREQ)
 915                 L_LINT(pps_freq, -MAXFREQ);
 916         if (time_status & STA_PPSFREQ)
 917                 time_freq = pps_freq;
 918 }
 919 #endif /* PPS_SYNC */
 920
 921 #ifndef _SYS_SYSPROTO_H_
 922 struct adjtime_args {
 923         struct timeval *delta;
 924         struct timeval *olddelta;
 925 };
 926 #endif
 927 /* ARGSUSED */
 928 int
 929 adjtime(struct thread *td, struct adjtime_args *uap)
 930 {
 931         struct timeval delta, olddelta, *deltap;
 932         int error;
 933
 934         if (uap->delta) {
 935                 error = copyin(uap->delta, &delta, sizeof(delta));
 936                 if (error)
 937                         return (error);
 938                 deltap = &delta;
 939         } else
 940                 deltap = NULL;
 941         error = kern_adjtime(td, deltap, &olddelta);
 942         if (uap->olddelta && error == 0)
 943                 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
 944         return (error);
 945 }
 946
 947 int
 948 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
 949 {
 950         struct timeval atv;
 951         int error;
 952
 953         mtx_lock(&Giant);
 954         if (olddelta) {
 955                 atv.tv_sec = time_adjtime / 1000000;
 956                 atv.tv_usec = time_adjtime % 1000000;
 957                 if (atv.tv_usec < 0) {
 958                         atv.tv_usec += 1000000;
 959                         atv.tv_sec--;
 960                 }
 961                 *olddelta = atv;
 962         }
 963         if (delta) {
 964                 if ((error = priv_check(td, PRIV_ADJTIME))) {
 965                         mtx_unlock(&Giant);
 966                         return (error);
 967                 }
 968                 time_adjtime = (int64_t)delta->tv_sec * 1000000 +
 969                     delta->tv_usec;
 970         }
 971         mtx_unlock(&Giant);
 972         return (0);
 973 }
 974