The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]

FreeBSD/Linux Kernel Cross Reference
sys/kern/kern_ntptime.c

Version: -  FREEBSD  -  FREEBSD-13-STABLE  -  FREEBSD-13-0  -  FREEBSD-12-STABLE  -  FREEBSD-12-0  -  FREEBSD-11-STABLE  -  FREEBSD-11-0  -  FREEBSD-10-STABLE  -  FREEBSD-10-0  -  FREEBSD-9-STABLE  -  FREEBSD-9-0  -  FREEBSD-8-STABLE  -  FREEBSD-8-0  -  FREEBSD-7-STABLE  -  FREEBSD-7-0  -  FREEBSD-6-STABLE  -  FREEBSD-6-0  -  FREEBSD-5-STABLE  -  FREEBSD-5-0  -  FREEBSD-4-STABLE  -  FREEBSD-3-STABLE  -  FREEBSD22  -  l41  -  OPENBSD  -  linux-2.6  -  MK84  -  PLAN9  -  xnu-8792 
SearchContext: -  none  -  3  -  10 

    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/eventhandler.h>
   42 #include <sys/kernel.h>
   43 #include <sys/priv.h>
   44 #include <sys/proc.h>
   45 #include <sys/lock.h>
   46 #include <sys/mutex.h>
   47 #include <sys/time.h>
   48 #include <sys/timex.h>
   49 #include <sys/timetc.h>
   50 #include <sys/timepps.h>
   51 #include <sys/syscallsubr.h>
   52 #include <sys/sysctl.h>
   53 
   54 #ifdef PPS_SYNC
   55 FEATURE(pps_sync, "Support usage of external PPS signal by kernel PLL");
   56 #endif
   57 
   58 /*
   59  * Single-precision macros for 64-bit machines
   60  */
   61 typedef int64_t l_fp;
   62 #define L_ADD(v, u)     ((v) += (u))
   63 #define L_SUB(v, u)     ((v) -= (u))
   64 #define L_ADDHI(v, a)   ((v) += (int64_t)(a) << 32)
   65 #define L_NEG(v)        ((v) = -(v))
   66 #define L_RSHIFT(v, n) \
   67         do { \
   68                 if ((v) < 0) \
   69                         (v) = -(-(v) >> (n)); \
   70                 else \
   71                         (v) = (v) >> (n); \
   72         } while (0)
   73 #define L_MPY(v, a)     ((v) *= (a))
   74 #define L_CLR(v)        ((v) = 0)
   75 #define L_ISNEG(v)      ((v) < 0)
   76 #define L_LINT(v, a)    ((v) = (int64_t)(a) << 32)
   77 #define L_GINT(v)       ((v) < 0 ? -(-(v) >> 32) : (v) >> 32)
   78 
   79 /*
   80  * Generic NTP kernel interface
   81  *
   82  * These routines constitute the Network Time Protocol (NTP) interfaces
   83  * for user and daemon application programs. The ntp_gettime() routine
   84  * provides the time, maximum error (synch distance) and estimated error
   85  * (dispersion) to client user application programs. The ntp_adjtime()
   86  * routine is used by the NTP daemon to adjust the system clock to an
   87  * externally derived time. The time offset and related variables set by
   88  * this routine are used by other routines in this module to adjust the
   89  * phase and frequency of the clock discipline loop which controls the
   90  * system clock.
   91  *
   92  * When the kernel time is reckoned directly in nanoseconds (NTP_NANO
   93  * defined), the time at each tick interrupt is derived directly from
   94  * the kernel time variable. When the kernel time is reckoned in
   95  * microseconds, (NTP_NANO undefined), the time is derived from the
   96  * kernel time variable together with a variable representing the
   97  * leftover nanoseconds at the last tick interrupt. In either case, the
   98  * current nanosecond time is reckoned from these values plus an
   99  * interpolated value derived by the clock routines in another
  100  * architecture-specific module. The interpolation can use either a
  101  * dedicated counter or a processor cycle counter (PCC) implemented in
  102  * some architectures.
  103  *
  104  * Note that all routines must run at priority splclock or higher.
  105  */
  106 /*
  107  * Phase/frequency-lock loop (PLL/FLL) definitions
  108  *
  109  * The nanosecond clock discipline uses two variable types, time
  110  * variables and frequency variables. Both types are represented as 64-
  111  * bit fixed-point quantities with the decimal point between two 32-bit
  112  * halves. On a 32-bit machine, each half is represented as a single
  113  * word and mathematical operations are done using multiple-precision
  114  * arithmetic. On a 64-bit machine, ordinary computer arithmetic is
  115  * used.
  116  *
  117  * A time variable is a signed 64-bit fixed-point number in ns and
  118  * fraction. It represents the remaining time offset to be amortized
  119  * over succeeding tick interrupts. The maximum time offset is about
  120  * 0.5 s and the resolution is about 2.3e-10 ns.
  121  *
  122  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
  123  *  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
  124  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  125  * |s s s|                       ns                                |
  126  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  127  * |                        fraction                               |
  128  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  129  *
  130  * A frequency variable is a signed 64-bit fixed-point number in ns/s
  131  * and fraction. It represents the ns and fraction to be added to the
  132  * kernel time variable at each second. The maximum frequency offset is
  133  * about +-500000 ns/s and the resolution is about 2.3e-10 ns/s.
  134  *
  135  *                      1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3
  136  *  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
  137  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  138  * |s s s s s s s s s s s s s|            ns/s                     |
  139  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  140  * |                        fraction                               |
  141  * +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  142  */
  143 /*
  144  * The following variables establish the state of the PLL/FLL and the
  145  * residual time and frequency offset of the local clock.
  146  */
  147 #define SHIFT_PLL       4               /* PLL loop gain (shift) */
  148 #define SHIFT_FLL       2               /* FLL loop gain (shift) */
  149 
  150 static int time_state = TIME_OK;        /* clock state */
  151 static int time_status = STA_UNSYNC;    /* clock status bits */
  152 static long time_tai;                   /* TAI offset (s) */
  153 static long time_monitor;               /* last time offset scaled (ns) */
  154 static long time_constant;              /* poll interval (shift) (s) */
  155 static long time_precision = 1;         /* clock precision (ns) */
  156 static long time_maxerror = MAXPHASE / 1000; /* maximum error (us) */
  157 static long time_esterror = MAXPHASE / 1000; /* estimated error (us) */
  158 static long time_reftime;               /* time at last adjustment (s) */
  159 static l_fp time_offset;                /* time offset (ns) */
  160 static l_fp time_freq;                  /* frequency offset (ns/s) */
  161 static l_fp time_adj;                   /* tick adjust (ns/s) */
  162 
  163 static int64_t time_adjtime;            /* correction from adjtime(2) (usec) */
  164 
  165 #ifdef PPS_SYNC
  166 /*
  167  * The following variables are used when a pulse-per-second (PPS) signal
  168  * is available and connected via a modem control lead. They establish
  169  * the engineering parameters of the clock discipline loop when
  170  * controlled by the PPS signal.
  171  */
  172 #define PPS_FAVG        2               /* min freq avg interval (s) (shift) */
  173 #define PPS_FAVGDEF     8               /* default freq avg int (s) (shift) */
  174 #define PPS_FAVGMAX     15              /* max freq avg interval (s) (shift) */
  175 #define PPS_PAVG        4               /* phase avg interval (s) (shift) */
  176 #define PPS_VALID       120             /* PPS signal watchdog max (s) */
  177 #define PPS_MAXWANDER   100000          /* max PPS wander (ns/s) */
  178 #define PPS_POPCORN     2               /* popcorn spike threshold (shift) */
  179 
  180 static struct timespec pps_tf[3];       /* phase median filter */
  181 static l_fp pps_freq;                   /* scaled frequency offset (ns/s) */
  182 static long pps_fcount;                 /* frequency accumulator */
  183 static long pps_jitter;                 /* nominal jitter (ns) */
  184 static long pps_stabil;                 /* nominal stability (scaled ns/s) */
  185 static long pps_lastsec;                /* time at last calibration (s) */
  186 static int pps_valid;                   /* signal watchdog counter */
  187 static int pps_shift = PPS_FAVG;        /* interval duration (s) (shift) */
  188 static int pps_shiftmax = PPS_FAVGDEF;  /* max interval duration (s) (shift) */
  189 static int pps_intcnt;                  /* wander counter */
  190 
  191 /*
  192  * PPS signal quality monitors
  193  */
  194 static long pps_calcnt;                 /* calibration intervals */
  195 static long pps_jitcnt;                 /* jitter limit exceeded */
  196 static long pps_stbcnt;                 /* stability limit exceeded */
  197 static long pps_errcnt;                 /* calibration errors */
  198 #endif /* PPS_SYNC */
  199 /*
  200  * End of phase/frequency-lock loop (PLL/FLL) definitions
  201  */
  202 
  203 static void ntp_init(void);
  204 static void hardupdate(long offset);
  205 static void ntp_gettime1(struct ntptimeval *ntvp);
  206 static int ntp_is_time_error(void);
  207 
  208 static int
  209 ntp_is_time_error(void)
  210 {
  211         /*
  212          * Status word error decode. If any of these conditions occur,
  213          * an error is returned, instead of the status word. Most
  214          * applications will care only about the fact the system clock
  215          * may not be trusted, not about the details.
  216          *
  217          * Hardware or software error
  218          */
  219         if ((time_status & (STA_UNSYNC | STA_CLOCKERR)) ||
  220 
  221         /*
  222          * PPS signal lost when either time or frequency synchronization
  223          * requested
  224          */
  225             (time_status & (STA_PPSFREQ | STA_PPSTIME) &&
  226             !(time_status & STA_PPSSIGNAL)) ||
  227 
  228         /*
  229          * PPS jitter exceeded when time synchronization requested
  230          */
  231             (time_status & STA_PPSTIME &&
  232             time_status & STA_PPSJITTER) ||
  233 
  234         /*
  235          * PPS wander exceeded or calibration error when frequency
  236          * synchronization requested
  237          */
  238             (time_status & STA_PPSFREQ &&
  239             time_status & (STA_PPSWANDER | STA_PPSERROR)))
  240                 return (1);
  241 
  242         return (0);
  243 }
  244 
  245 static void
  246 ntp_gettime1(struct ntptimeval *ntvp)
  247 {
  248         struct timespec atv;    /* nanosecond time */
  249 
  250         GIANT_REQUIRED;
  251 
  252         nanotime(&atv);
  253         ntvp->time.tv_sec = atv.tv_sec;
  254         ntvp->time.tv_nsec = atv.tv_nsec;
  255         ntvp->maxerror = time_maxerror;
  256         ntvp->esterror = time_esterror;
  257         ntvp->tai = time_tai;
  258         ntvp->time_state = time_state;
  259 
  260         if (ntp_is_time_error())
  261                 ntvp->time_state = TIME_ERROR;
  262 }
  263 
  264 /*
  265  * ntp_gettime() - NTP user application interface
  266  *
  267  * See the timex.h header file for synopsis and API description.  Note that
  268  * the TAI offset is returned in the ntvtimeval.tai structure member.
  269  */
  270 #ifndef _SYS_SYSPROTO_H_
  271 struct ntp_gettime_args {
  272         struct ntptimeval *ntvp;
  273 };
  274 #endif
  275 /* ARGSUSED */
  276 int
  277 sys_ntp_gettime(struct thread *td, struct ntp_gettime_args *uap)
  278 {       
  279         struct ntptimeval ntv;
  280 
  281         mtx_lock(&Giant);
  282         ntp_gettime1(&ntv);
  283         mtx_unlock(&Giant);
  284 
  285         td->td_retval[0] = ntv.time_state;
  286         return (copyout(&ntv, uap->ntvp, sizeof(ntv)));
  287 }
  288 
  289 static int
  290 ntp_sysctl(SYSCTL_HANDLER_ARGS)
  291 {
  292         struct ntptimeval ntv;  /* temporary structure */
  293 
  294         ntp_gettime1(&ntv);
  295 
  296         return (sysctl_handle_opaque(oidp, &ntv, sizeof(ntv), req));
  297 }
  298 
  299 SYSCTL_NODE(_kern, OID_AUTO, ntp_pll, CTLFLAG_RW, 0, "");
  300 SYSCTL_PROC(_kern_ntp_pll, OID_AUTO, gettime, CTLTYPE_OPAQUE|CTLFLAG_RD,
  301         0, sizeof(struct ntptimeval) , ntp_sysctl, "S,ntptimeval", "");
  302 
  303 #ifdef PPS_SYNC
  304 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shiftmax, CTLFLAG_RW, &pps_shiftmax, 0, "");
  305 SYSCTL_INT(_kern_ntp_pll, OID_AUTO, pps_shift, CTLFLAG_RW, &pps_shift, 0, "");
  306 SYSCTL_LONG(_kern_ntp_pll, OID_AUTO, time_monitor, CTLFLAG_RD,
  307     &time_monitor, 0, "");
  308 
  309 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, pps_freq, CTLFLAG_RD, &pps_freq, sizeof(pps_freq), "I", "");
  310 SYSCTL_OPAQUE(_kern_ntp_pll, OID_AUTO, time_freq, CTLFLAG_RD, &time_freq, sizeof(time_freq), "I", "");
  311 #endif
  312 
  313 /*
  314  * ntp_adjtime() - NTP daemon application interface
  315  *
  316  * See the timex.h header file for synopsis and API description.  Note that
  317  * the timex.constant structure member has a dual purpose to set the time
  318  * constant and to set the TAI offset.
  319  */
  320 #ifndef _SYS_SYSPROTO_H_
  321 struct ntp_adjtime_args {
  322         struct timex *tp;
  323 };
  324 #endif
  325 
  326 int
  327 sys_ntp_adjtime(struct thread *td, struct ntp_adjtime_args *uap)
  328 {
  329         struct timex ntv;       /* temporary structure */
  330         long freq;              /* frequency ns/s) */
  331         int modes;              /* mode bits from structure */
  332         int s;                  /* caller priority */
  333         int error;
  334 
  335         error = copyin((caddr_t)uap->tp, (caddr_t)&ntv, sizeof(ntv));
  336         if (error)
  337                 return(error);
  338 
  339         /*
  340          * Update selected clock variables - only the superuser can
  341          * change anything. Note that there is no error checking here on
  342          * the assumption the superuser should know what it is doing.
  343          * Note that either the time constant or TAI offset are loaded
  344          * from the ntv.constant member, depending on the mode bits. If
  345          * the STA_PLL bit in the status word is cleared, the state and
  346          * status words are reset to the initial values at boot.
  347          */
  348         mtx_lock(&Giant);
  349         modes = ntv.modes;
  350         if (modes)
  351                 error = priv_check(td, PRIV_NTP_ADJTIME);
  352         if (error)
  353                 goto done2;
  354         s = splclock();
  355         if (modes & MOD_MAXERROR)
  356                 time_maxerror = ntv.maxerror;
  357         if (modes & MOD_ESTERROR)
  358                 time_esterror = ntv.esterror;
  359         if (modes & MOD_STATUS) {
  360                 if (time_status & STA_PLL && !(ntv.status & STA_PLL)) {
  361                         time_state = TIME_OK;
  362                         time_status = STA_UNSYNC;
  363 #ifdef PPS_SYNC
  364                         pps_shift = PPS_FAVG;
  365 #endif /* PPS_SYNC */
  366                 }
  367                 time_status &= STA_RONLY;
  368                 time_status |= ntv.status & ~STA_RONLY;
  369         }
  370         if (modes & MOD_TIMECONST) {
  371                 if (ntv.constant < 0)
  372                         time_constant = 0;
  373                 else if (ntv.constant > MAXTC)
  374                         time_constant = MAXTC;
  375                 else
  376                         time_constant = ntv.constant;
  377         }
  378         if (modes & MOD_TAI) {
  379                 if (ntv.constant > 0) /* XXX zero & negative numbers ? */
  380                         time_tai = ntv.constant;
  381         }
  382 #ifdef PPS_SYNC
  383         if (modes & MOD_PPSMAX) {
  384                 if (ntv.shift < PPS_FAVG)
  385                         pps_shiftmax = PPS_FAVG;
  386                 else if (ntv.shift > PPS_FAVGMAX)
  387                         pps_shiftmax = PPS_FAVGMAX;
  388                 else
  389                         pps_shiftmax = ntv.shift;
  390         }
  391 #endif /* PPS_SYNC */
  392         if (modes & MOD_NANO)
  393                 time_status |= STA_NANO;
  394         if (modes & MOD_MICRO)
  395                 time_status &= ~STA_NANO;
  396         if (modes & MOD_CLKB)
  397                 time_status |= STA_CLK;
  398         if (modes & MOD_CLKA)
  399                 time_status &= ~STA_CLK;
  400         if (modes & MOD_FREQUENCY) {
  401                 freq = (ntv.freq * 1000LL) >> 16;
  402                 if (freq > MAXFREQ)
  403                         L_LINT(time_freq, MAXFREQ);
  404                 else if (freq < -MAXFREQ)
  405                         L_LINT(time_freq, -MAXFREQ);
  406                 else {
  407                         /*
  408                          * ntv.freq is [PPM * 2^16] = [us/s * 2^16]
  409                          * time_freq is [ns/s * 2^32]
  410                          */
  411                         time_freq = ntv.freq * 1000LL * 65536LL;
  412                 }
  413 #ifdef PPS_SYNC
  414                 pps_freq = time_freq;
  415 #endif /* PPS_SYNC */
  416         }
  417         if (modes & MOD_OFFSET) {
  418                 if (time_status & STA_NANO)
  419                         hardupdate(ntv.offset);
  420                 else
  421                         hardupdate(ntv.offset * 1000);
  422         }
  423 
  424         /*
  425          * Retrieve all clock variables. Note that the TAI offset is
  426          * returned only by ntp_gettime();
  427          */
  428         if (time_status & STA_NANO)
  429                 ntv.offset = L_GINT(time_offset);
  430         else
  431                 ntv.offset = L_GINT(time_offset) / 1000; /* XXX rounding ? */
  432         ntv.freq = L_GINT((time_freq / 1000LL) << 16);
  433         ntv.maxerror = time_maxerror;
  434         ntv.esterror = time_esterror;
  435         ntv.status = time_status;
  436         ntv.constant = time_constant;
  437         if (time_status & STA_NANO)
  438                 ntv.precision = time_precision;
  439         else
  440                 ntv.precision = time_precision / 1000;
  441         ntv.tolerance = MAXFREQ * SCALE_PPM;
  442 #ifdef PPS_SYNC
  443         ntv.shift = pps_shift;
  444         ntv.ppsfreq = L_GINT((pps_freq / 1000LL) << 16);
  445         if (time_status & STA_NANO)
  446                 ntv.jitter = pps_jitter;
  447         else
  448                 ntv.jitter = pps_jitter / 1000;
  449         ntv.stabil = pps_stabil;
  450         ntv.calcnt = pps_calcnt;
  451         ntv.errcnt = pps_errcnt;
  452         ntv.jitcnt = pps_jitcnt;
  453         ntv.stbcnt = pps_stbcnt;
  454 #endif /* PPS_SYNC */
  455         splx(s);
  456 
  457         error = copyout((caddr_t)&ntv, (caddr_t)uap->tp, sizeof(ntv));
  458         if (error)
  459                 goto done2;
  460 
  461         if (ntp_is_time_error())
  462                 td->td_retval[0] = TIME_ERROR;
  463         else
  464                 td->td_retval[0] = time_state;
  465 
  466 done2:
  467         mtx_unlock(&Giant);
  468         return (error);
  469 }
  470 
  471 /*
  472  * second_overflow() - called after ntp_tick_adjust()
  473  *
  474  * This routine is ordinarily called immediately following the above
  475  * routine ntp_tick_adjust(). While these two routines are normally
  476  * combined, they are separated here only for the purposes of
  477  * simulation.
  478  */
  479 void
  480 ntp_update_second(int64_t *adjustment, time_t *newsec)
  481 {
  482         int tickrate;
  483         l_fp ftemp;             /* 32/64-bit temporary */
  484 
  485         /*
  486          * On rollover of the second both the nanosecond and microsecond
  487          * clocks are updated and the state machine cranked as
  488          * necessary. The phase adjustment to be used for the next
  489          * second is calculated and the maximum error is increased by
  490          * the tolerance.
  491          */
  492         time_maxerror += MAXFREQ / 1000;
  493 
  494         /*
  495          * Leap second processing. If in leap-insert state at
  496          * the end of the day, the system clock is set back one
  497          * second; if in leap-delete state, the system clock is
  498          * set ahead one second. The nano_time() routine or
  499          * external clock driver will insure that reported time
  500          * is always monotonic.
  501          */
  502         switch (time_state) {
  503 
  504                 /*
  505                  * No warning.
  506                  */
  507                 case TIME_OK:
  508                 if (time_status & STA_INS)
  509                         time_state = TIME_INS;
  510                 else if (time_status & STA_DEL)
  511                         time_state = TIME_DEL;
  512                 break;
  513 
  514                 /*
  515                  * Insert second 23:59:60 following second
  516                  * 23:59:59.
  517                  */
  518                 case TIME_INS:
  519                 if (!(time_status & STA_INS))
  520                         time_state = TIME_OK;
  521                 else if ((*newsec) % 86400 == 0) {
  522                         (*newsec)--;
  523                         time_state = TIME_OOP;
  524                         time_tai++;
  525                 }
  526                 break;
  527 
  528                 /*
  529                  * Delete second 23:59:59.
  530                  */
  531                 case TIME_DEL:
  532                 if (!(time_status & STA_DEL))
  533                         time_state = TIME_OK;
  534                 else if (((*newsec) + 1) % 86400 == 0) {
  535                         (*newsec)++;
  536                         time_tai--;
  537                         time_state = TIME_WAIT;
  538                 }
  539                 break;
  540 
  541                 /*
  542                  * Insert second in progress.
  543                  */
  544                 case TIME_OOP:
  545                         time_state = TIME_WAIT;
  546                 break;
  547 
  548                 /*
  549                  * Wait for status bits to clear.
  550                  */
  551                 case TIME_WAIT:
  552                 if (!(time_status & (STA_INS | STA_DEL)))
  553                         time_state = TIME_OK;
  554         }
  555 
  556         /*
  557          * Compute the total time adjustment for the next second
  558          * in ns. The offset is reduced by a factor depending on
  559          * whether the PPS signal is operating. Note that the
  560          * value is in effect scaled by the clock frequency,
  561          * since the adjustment is added at each tick interrupt.
  562          */
  563         ftemp = time_offset;
  564 #ifdef PPS_SYNC
  565         /* XXX even if PPS signal dies we should finish adjustment ? */
  566         if (time_status & STA_PPSTIME && time_status &
  567             STA_PPSSIGNAL)
  568                 L_RSHIFT(ftemp, pps_shift);
  569         else
  570                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
  571 #else
  572                 L_RSHIFT(ftemp, SHIFT_PLL + time_constant);
  573 #endif /* PPS_SYNC */
  574         time_adj = ftemp;
  575         L_SUB(time_offset, ftemp);
  576         L_ADD(time_adj, time_freq);
  577         
  578         /*
  579          * Apply any correction from adjtime(2).  If more than one second
  580          * off we slew at a rate of 5ms/s (5000 PPM) else 500us/s (500PPM)
  581          * until the last second is slewed the final < 500 usecs.
  582          */
  583         if (time_adjtime != 0) {
  584                 if (time_adjtime > 1000000)
  585                         tickrate = 5000;
  586                 else if (time_adjtime < -1000000)
  587                         tickrate = -5000;
  588                 else if (time_adjtime > 500)
  589                         tickrate = 500;
  590                 else if (time_adjtime < -500)
  591                         tickrate = -500;
  592                 else
  593                         tickrate = time_adjtime;
  594                 time_adjtime -= tickrate;
  595                 L_LINT(ftemp, tickrate * 1000);
  596                 L_ADD(time_adj, ftemp);
  597         }
  598         *adjustment = time_adj;
  599                 
  600 #ifdef PPS_SYNC
  601         if (pps_valid > 0)
  602                 pps_valid--;
  603         else
  604                 time_status &= ~STA_PPSSIGNAL;
  605 #endif /* PPS_SYNC */
  606 }
  607 
  608 /*
  609  * ntp_init() - initialize variables and structures
  610  *
  611  * This routine must be called after the kernel variables hz and tick
  612  * are set or changed and before the next tick interrupt. In this
  613  * particular implementation, these values are assumed set elsewhere in
  614  * the kernel. The design allows the clock frequency and tick interval
  615  * to be changed while the system is running. So, this routine should
  616  * probably be integrated with the code that does that.
  617  */
  618 static void
  619 ntp_init()
  620 {
  621 
  622         /*
  623          * The following variables are initialized only at startup. Only
  624          * those structures not cleared by the compiler need to be
  625          * initialized, and these only in the simulator. In the actual
  626          * kernel, any nonzero values here will quickly evaporate.
  627          */
  628         L_CLR(time_offset);
  629         L_CLR(time_freq);
  630 #ifdef PPS_SYNC
  631         pps_tf[0].tv_sec = pps_tf[0].tv_nsec = 0;
  632         pps_tf[1].tv_sec = pps_tf[1].tv_nsec = 0;
  633         pps_tf[2].tv_sec = pps_tf[2].tv_nsec = 0;
  634         pps_fcount = 0;
  635         L_CLR(pps_freq);
  636 #endif /* PPS_SYNC */      
  637 }
  638 
  639 SYSINIT(ntpclocks, SI_SUB_CLOCKS, SI_ORDER_MIDDLE, ntp_init, NULL);
  640 
  641 /*
  642  * hardupdate() - local clock update
  643  *
  644  * This routine is called by ntp_adjtime() to update the local clock
  645  * phase and frequency. The implementation is of an adaptive-parameter,
  646  * hybrid phase/frequency-lock loop (PLL/FLL). The routine computes new
  647  * time and frequency offset estimates for each call. If the kernel PPS
  648  * discipline code is configured (PPS_SYNC), the PPS signal itself
  649  * determines the new time offset, instead of the calling argument.
  650  * Presumably, calls to ntp_adjtime() occur only when the caller
  651  * believes the local clock is valid within some bound (+-128 ms with
  652  * NTP). If the caller's time is far different than the PPS time, an
  653  * argument will ensue, and it's not clear who will lose.
  654  *
  655  * For uncompensated quartz crystal oscillators and nominal update
  656  * intervals less than 256 s, operation should be in phase-lock mode,
  657  * where the loop is disciplined to phase. For update intervals greater
  658  * than 1024 s, operation should be in frequency-lock mode, where the
  659  * loop is disciplined to frequency. Between 256 s and 1024 s, the mode
  660  * is selected by the STA_MODE status bit.
  661  */
  662 static void
  663 hardupdate(offset)
  664         long offset;            /* clock offset (ns) */
  665 {
  666         long mtemp;
  667         l_fp ftemp;
  668 
  669         /*
  670          * Select how the phase is to be controlled and from which
  671          * source. If the PPS signal is present and enabled to
  672          * discipline the time, the PPS offset is used; otherwise, the
  673          * argument offset is used.
  674          */
  675         if (!(time_status & STA_PLL))
  676                 return;
  677         if (!(time_status & STA_PPSTIME && time_status &
  678             STA_PPSSIGNAL)) {
  679                 if (offset > MAXPHASE)
  680                         time_monitor = MAXPHASE;
  681                 else if (offset < -MAXPHASE)
  682                         time_monitor = -MAXPHASE;
  683                 else
  684                         time_monitor = offset;
  685                 L_LINT(time_offset, time_monitor);
  686         }
  687 
  688         /*
  689          * Select how the frequency is to be controlled and in which
  690          * mode (PLL or FLL). If the PPS signal is present and enabled
  691          * to discipline the frequency, the PPS frequency is used;
  692          * otherwise, the argument offset is used to compute it.
  693          */
  694         if (time_status & STA_PPSFREQ && time_status & STA_PPSSIGNAL) {
  695                 time_reftime = time_second;
  696                 return;
  697         }
  698         if (time_status & STA_FREQHOLD || time_reftime == 0)
  699                 time_reftime = time_second;
  700         mtemp = time_second - time_reftime;
  701         L_LINT(ftemp, time_monitor);
  702         L_RSHIFT(ftemp, (SHIFT_PLL + 2 + time_constant) << 1);
  703         L_MPY(ftemp, mtemp);
  704         L_ADD(time_freq, ftemp);
  705         time_status &= ~STA_MODE;
  706         if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp >
  707             MAXSEC)) {
  708                 L_LINT(ftemp, (time_monitor << 4) / mtemp);
  709                 L_RSHIFT(ftemp, SHIFT_FLL + 4);
  710                 L_ADD(time_freq, ftemp);
  711                 time_status |= STA_MODE;
  712         }
  713         time_reftime = time_second;
  714         if (L_GINT(time_freq) > MAXFREQ)
  715                 L_LINT(time_freq, MAXFREQ);
  716         else if (L_GINT(time_freq) < -MAXFREQ)
  717                 L_LINT(time_freq, -MAXFREQ);
  718 }
  719 
  720 #ifdef PPS_SYNC
  721 /*
  722  * hardpps() - discipline CPU clock oscillator to external PPS signal
  723  *
  724  * This routine is called at each PPS interrupt in order to discipline
  725  * the CPU clock oscillator to the PPS signal. There are two independent
  726  * first-order feedback loops, one for the phase, the other for the
  727  * frequency. The phase loop measures and grooms the PPS phase offset
  728  * and leaves it in a handy spot for the seconds overflow routine. The
  729  * frequency loop averages successive PPS phase differences and
  730  * calculates the PPS frequency offset, which is also processed by the
  731  * seconds overflow routine. The code requires the caller to capture the
  732  * time and architecture-dependent hardware counter values in
  733  * nanoseconds at the on-time PPS signal transition.
  734  *
  735  * Note that, on some Unix systems this routine runs at an interrupt
  736  * priority level higher than the timer interrupt routine hardclock().
  737  * Therefore, the variables used are distinct from the hardclock()
  738  * variables, except for the actual time and frequency variables, which
  739  * are determined by this routine and updated atomically.
  740  */
  741 void
  742 hardpps(tsp, nsec)
  743         struct timespec *tsp;   /* time at PPS */
  744         long nsec;              /* hardware counter at PPS */
  745 {
  746         long u_sec, u_nsec, v_nsec; /* temps */
  747         l_fp ftemp;
  748 
  749         /*
  750          * The signal is first processed by a range gate and frequency
  751          * discriminator. The range gate rejects noise spikes outside
  752          * the range +-500 us. The frequency discriminator rejects input
  753          * signals with apparent frequency outside the range 1 +-500
  754          * PPM. If two hits occur in the same second, we ignore the
  755          * later hit; if not and a hit occurs outside the range gate,
  756          * keep the later hit for later comparison, but do not process
  757          * it.
  758          */
  759         time_status |= STA_PPSSIGNAL | STA_PPSJITTER;
  760         time_status &= ~(STA_PPSWANDER | STA_PPSERROR);
  761         pps_valid = PPS_VALID;
  762         u_sec = tsp->tv_sec;
  763         u_nsec = tsp->tv_nsec;
  764         if (u_nsec >= (NANOSECOND >> 1)) {
  765                 u_nsec -= NANOSECOND;
  766                 u_sec++;
  767         }
  768         v_nsec = u_nsec - pps_tf[0].tv_nsec;
  769         if (u_sec == pps_tf[0].tv_sec && v_nsec < NANOSECOND -
  770             MAXFREQ)
  771                 return;
  772         pps_tf[2] = pps_tf[1];
  773         pps_tf[1] = pps_tf[0];
  774         pps_tf[0].tv_sec = u_sec;
  775         pps_tf[0].tv_nsec = u_nsec;
  776 
  777         /*
  778          * Compute the difference between the current and previous
  779          * counter values. If the difference exceeds 0.5 s, assume it
  780          * has wrapped around, so correct 1.0 s. If the result exceeds
  781          * the tick interval, the sample point has crossed a tick
  782          * boundary during the last second, so correct the tick. Very
  783          * intricate.
  784          */
  785         u_nsec = nsec;
  786         if (u_nsec > (NANOSECOND >> 1))
  787                 u_nsec -= NANOSECOND;
  788         else if (u_nsec < -(NANOSECOND >> 1))
  789                 u_nsec += NANOSECOND;
  790         pps_fcount += u_nsec;
  791         if (v_nsec > MAXFREQ || v_nsec < -MAXFREQ)
  792                 return;
  793         time_status &= ~STA_PPSJITTER;
  794 
  795         /*
  796          * A three-stage median filter is used to help denoise the PPS
  797          * time. The median sample becomes the time offset estimate; the
  798          * difference between the other two samples becomes the time
  799          * dispersion (jitter) estimate.
  800          */
  801         if (pps_tf[0].tv_nsec > pps_tf[1].tv_nsec) {
  802                 if (pps_tf[1].tv_nsec > pps_tf[2].tv_nsec) {
  803                         v_nsec = pps_tf[1].tv_nsec;     /* 0 1 2 */
  804                         u_nsec = pps_tf[0].tv_nsec - pps_tf[2].tv_nsec;
  805                 } else if (pps_tf[2].tv_nsec > pps_tf[0].tv_nsec) {
  806                         v_nsec = pps_tf[0].tv_nsec;     /* 2 0 1 */
  807                         u_nsec = pps_tf[2].tv_nsec - pps_tf[1].tv_nsec;
  808                 } else {
  809                         v_nsec = pps_tf[2].tv_nsec;     /* 0 2 1 */
  810                         u_nsec = pps_tf[0].tv_nsec - pps_tf[1].tv_nsec;
  811                 }
  812         } else {
  813                 if (pps_tf[1].tv_nsec < pps_tf[2].tv_nsec) {
  814                         v_nsec = pps_tf[1].tv_nsec;     /* 2 1 0 */
  815                         u_nsec = pps_tf[2].tv_nsec - pps_tf[0].tv_nsec;
  816                 } else if (pps_tf[2].tv_nsec < pps_tf[0].tv_nsec) {
  817                         v_nsec = pps_tf[0].tv_nsec;     /* 1 0 2 */
  818                         u_nsec = pps_tf[1].tv_nsec - pps_tf[2].tv_nsec;
  819                 } else {
  820                         v_nsec = pps_tf[2].tv_nsec;     /* 1 2 0 */
  821                         u_nsec = pps_tf[1].tv_nsec - pps_tf[0].tv_nsec;
  822                 }
  823         }
  824 
  825         /*
  826          * Nominal jitter is due to PPS signal noise and interrupt
  827          * latency. If it exceeds the popcorn threshold, the sample is
  828          * discarded. otherwise, if so enabled, the time offset is
  829          * updated. We can tolerate a modest loss of data here without
  830          * much degrading time accuracy.
  831          */
  832         if (u_nsec > (pps_jitter << PPS_POPCORN)) {
  833                 time_status |= STA_PPSJITTER;
  834                 pps_jitcnt++;
  835         } else if (time_status & STA_PPSTIME) {
  836                 time_monitor = -v_nsec;
  837                 L_LINT(time_offset, time_monitor);
  838         }
  839         pps_jitter += (u_nsec - pps_jitter) >> PPS_FAVG;
  840         u_sec = pps_tf[0].tv_sec - pps_lastsec;
  841         if (u_sec < (1 << pps_shift))
  842                 return;
  843 
  844         /*
  845          * At the end of the calibration interval the difference between
  846          * the first and last counter values becomes the scaled
  847          * frequency. It will later be divided by the length of the
  848          * interval to determine the frequency update. If the frequency
  849          * exceeds a sanity threshold, or if the actual calibration
  850          * interval is not equal to the expected length, the data are
  851          * discarded. We can tolerate a modest loss of data here without
  852          * much degrading frequency accuracy.
  853          */
  854         pps_calcnt++;
  855         v_nsec = -pps_fcount;
  856         pps_lastsec = pps_tf[0].tv_sec;
  857         pps_fcount = 0;
  858         u_nsec = MAXFREQ << pps_shift;
  859         if (v_nsec > u_nsec || v_nsec < -u_nsec || u_sec != (1 <<
  860             pps_shift)) {
  861                 time_status |= STA_PPSERROR;
  862                 pps_errcnt++;
  863                 return;
  864         }
  865 
  866         /*
  867          * Here the raw frequency offset and wander (stability) is
  868          * calculated. If the wander is less than the wander threshold
  869          * for four consecutive averaging intervals, the interval is
  870          * doubled; if it is greater than the threshold for four
  871          * consecutive intervals, the interval is halved. The scaled
  872          * frequency offset is converted to frequency offset. The
  873          * stability metric is calculated as the average of recent
  874          * frequency changes, but is used only for performance
  875          * monitoring.
  876          */
  877         L_LINT(ftemp, v_nsec);
  878         L_RSHIFT(ftemp, pps_shift);
  879         L_SUB(ftemp, pps_freq);
  880         u_nsec = L_GINT(ftemp);
  881         if (u_nsec > PPS_MAXWANDER) {
  882                 L_LINT(ftemp, PPS_MAXWANDER);
  883                 pps_intcnt--;
  884                 time_status |= STA_PPSWANDER;
  885                 pps_stbcnt++;
  886         } else if (u_nsec < -PPS_MAXWANDER) {
  887                 L_LINT(ftemp, -PPS_MAXWANDER);
  888                 pps_intcnt--;
  889                 time_status |= STA_PPSWANDER;
  890                 pps_stbcnt++;
  891         } else {
  892                 pps_intcnt++;
  893         }
  894         if (pps_intcnt >= 4) {
  895                 pps_intcnt = 4;
  896                 if (pps_shift < pps_shiftmax) {
  897                         pps_shift++;
  898                         pps_intcnt = 0;
  899                 }
  900         } else if (pps_intcnt <= -4 || pps_shift > pps_shiftmax) {
  901                 pps_intcnt = -4;
  902                 if (pps_shift > PPS_FAVG) {
  903                         pps_shift--;
  904                         pps_intcnt = 0;
  905                 }
  906         }
  907         if (u_nsec < 0)
  908                 u_nsec = -u_nsec;
  909         pps_stabil += (u_nsec * SCALE_PPM - pps_stabil) >> PPS_FAVG;
  910 
  911         /*
  912          * The PPS frequency is recalculated and clamped to the maximum
  913          * MAXFREQ. If enabled, the system clock frequency is updated as
  914          * well.
  915          */
  916         L_ADD(pps_freq, ftemp);
  917         u_nsec = L_GINT(pps_freq);
  918         if (u_nsec > MAXFREQ)
  919                 L_LINT(pps_freq, MAXFREQ);
  920         else if (u_nsec < -MAXFREQ)
  921                 L_LINT(pps_freq, -MAXFREQ);
  922         if (time_status & STA_PPSFREQ)
  923                 time_freq = pps_freq;
  924 }
  925 #endif /* PPS_SYNC */
  926 
  927 #ifndef _SYS_SYSPROTO_H_
  928 struct adjtime_args {
  929         struct timeval *delta;
  930         struct timeval *olddelta;
  931 };
  932 #endif
  933 /* ARGSUSED */
  934 int
  935 sys_adjtime(struct thread *td, struct adjtime_args *uap)
  936 {
  937         struct timeval delta, olddelta, *deltap;
  938         int error;
  939 
  940         if (uap->delta) {
  941                 error = copyin(uap->delta, &delta, sizeof(delta));
  942                 if (error)
  943                         return (error);
  944                 deltap = &delta;
  945         } else
  946                 deltap = NULL;
  947         error = kern_adjtime(td, deltap, &olddelta);
  948         if (uap->olddelta && error == 0)
  949                 error = copyout(&olddelta, uap->olddelta, sizeof(olddelta));
  950         return (error);
  951 }
  952 
  953 int
  954 kern_adjtime(struct thread *td, struct timeval *delta, struct timeval *olddelta)
  955 {
  956         struct timeval atv;
  957         int error;
  958 
  959         mtx_lock(&Giant);
  960         if (olddelta) {
  961                 atv.tv_sec = time_adjtime / 1000000;
  962                 atv.tv_usec = time_adjtime % 1000000;
  963                 if (atv.tv_usec < 0) {
  964                         atv.tv_usec += 1000000;
  965                         atv.tv_sec--;
  966                 }
  967                 *olddelta = atv;
  968         }
  969         if (delta) {
  970                 if ((error = priv_check(td, PRIV_ADJTIME))) {
  971                         mtx_unlock(&Giant);
  972                         return (error);
  973                 }
  974                 time_adjtime = (int64_t)delta->tv_sec * 1000000 +
  975                     delta->tv_usec;
  976         }
  977         mtx_unlock(&Giant);
  978         return (0);
  979 }
  980 
  981 static struct callout resettodr_callout;
  982 static int resettodr_period = 1800;
  983 
  984 static void
  985 periodic_resettodr(void *arg __unused)
  986 {
  987 
  988         if (!ntp_is_time_error()) {
  989                 mtx_lock(&Giant);
  990                 resettodr();
  991                 mtx_unlock(&Giant);
  992         }
  993         if (resettodr_period > 0)
  994                 callout_schedule(&resettodr_callout, resettodr_period * hz);
  995 }
  996 
  997 static void
  998 shutdown_resettodr(void *arg __unused, int howto __unused)
  999 {
 1000 
 1001         callout_drain(&resettodr_callout);
 1002         if (resettodr_period > 0 && !ntp_is_time_error()) {
 1003                 mtx_lock(&Giant);
 1004                 resettodr();
 1005                 mtx_unlock(&Giant);
 1006         }
 1007 }
 1008 
 1009 static int
 1010 sysctl_resettodr_period(SYSCTL_HANDLER_ARGS)
 1011 {
 1012         int error;
 1013 
 1014         error = sysctl_handle_int(oidp, oidp->oid_arg1, oidp->oid_arg2, req);
 1015         if (error || !req->newptr)
 1016                 return (error);
 1017         if (resettodr_period == 0)
 1018                 callout_stop(&resettodr_callout);
 1019         else
 1020                 callout_reset(&resettodr_callout, resettodr_period * hz,
 1021                     periodic_resettodr, NULL);
 1022         return (0);
 1023 }
 1024 
 1025 SYSCTL_PROC(_machdep, OID_AUTO, rtc_save_period, CTLTYPE_INT|CTLFLAG_RW,
 1026         &resettodr_period, 1800, sysctl_resettodr_period, "I",
 1027         "Save system time to RTC with this period (in seconds)");
 1028 TUNABLE_INT("machdep.rtc_save_period", &resettodr_period);
 1029 
 1030 static void
 1031 start_periodic_resettodr(void *arg __unused)
 1032 {
 1033 
 1034         EVENTHANDLER_REGISTER(shutdown_pre_sync, shutdown_resettodr, NULL,
 1035             SHUTDOWN_PRI_FIRST);
 1036         callout_init(&resettodr_callout, 1);
 1037         if (resettodr_period == 0)
 1038                 return;
 1039         callout_reset(&resettodr_callout, resettodr_period * hz,
 1040             periodic_resettodr, NULL);
 1041 }
 1042 
 1043 SYSINIT(periodic_resettodr, SI_SUB_LAST, SI_ORDER_MIDDLE,
 1044         start_periodic_resettodr, NULL);

Cache object: 924156e69a1b08b647fdf106b31e1b34


[ source navigation ] [ diff markup ] [ identifier search ] [ freetext search ] [ file search ] [ list types ] [ track identifier ]


This page is part of the FreeBSD/Linux Linux Kernel Cross-Reference, and was automatically generated using a modified version of the LXR engine.