include/linux/timex.h

   1 /*****************************************************************************
   2  *                                                                           *
   3  * Copyright (c) David L. Mills 1993                                         *
   4  *                                                                           *
   5  * Permission to use, copy, modify, and distribute this software and its     *
   6  * documentation for any purpose and without fee is hereby granted, provided *
   7  * that the above copyright notice appears in all copies and that both the   *
   8  * copyright notice and this permission notice appear in supporting          *
   9  * documentation, and that the name University of Delaware not be used in    *
  10  * advertising or publicity pertaining to distribution of the software       *
  11  * without specific, written prior permission.  The University of Delaware   *
  12  * makes no representations about the suitability this software for any      *
  13  * purpose.  It is provided "as is" without express or implied warranty.     *
  14  *                                                                           *
  15  *****************************************************************************/
  16
  17 /*
  18  * Modification history timex.h
  19  *
  20  * 29 Dec 97    Russell King
  21  *      Moved CLOCK_TICK_RATE, CLOCK_TICK_FACTOR and FINETUNE to asm/timex.h
  22  *      for ARM machines
  23  *
  24  *  9 Jan 97    Adrian Sun
  25  *      Shifted LATCH define to allow access to alpha machines.
  26  *
  27  * 26 Sep 94    David L. Mills
  28  *      Added defines for hybrid phase/frequency-lock loop.
  29  *
  30  * 19 Mar 94    David L. Mills
  31  *      Moved defines from kernel routines to header file and added new
  32  *      defines for PPS phase-lock loop.
  33  *
  34  * 20 Feb 94    David L. Mills
  35  *      Revised status codes and structures for external clock and PPS
  36  *      signal discipline.
  37  *
  38  * 28 Nov 93    David L. Mills
  39  *      Adjusted parameters to improve stability and increase poll
  40  *      interval.
  41  *
  42  * 17 Sep 93    David L. Mills
  43  *      Created file $NTP/include/sys/timex.h
  44  * 07 Oct 93    Torsten Duwe
  45  *      Derived linux/timex.h
  46  * 1995-08-13    Torsten Duwe
  47  *      kernel PLL updated to 1994-12-13 specs (rfc-1589)
  48  * 1997-08-30    Ulrich Windl
  49  *      Added new constant NTP_PHASE_LIMIT
  50  * 2004-08-12    Christoph Lameter
  51  *      Reworked time interpolation logic
  52  */
  53 #ifndef _LINUX_TIMEX_H
  54 #define _LINUX_TIMEX_H
  55
  56 #include <linux/config.h>
  57 #include <linux/compiler.h>
  58 #include <linux/time.h>
  59
  60 #include <asm/param.h>
  61 #include <asm/timex.h>
  62
  63 /*
  64  * SHIFT_KG and SHIFT_KF establish the damping of the PLL and are chosen
  65  * for a slightly underdamped convergence characteristic. SHIFT_KH
  66  * establishes the damping of the FLL and is chosen by wisdom and black
  67  * art.
  68  *
  69  * MAXTC establishes the maximum time constant of the PLL. With the
  70  * SHIFT_KG and SHIFT_KF values given and a time constant range from
  71  * zero to MAXTC, the PLL will converge in 15 minutes to 16 hours,
  72  * respectively.
  73  */
  74 #define SHIFT_KG 6              /* phase factor (shift) */
  75 #define SHIFT_KF 16             /* PLL frequency factor (shift) */
  76 #define SHIFT_KH 2              /* FLL frequency factor (shift) */
  77 #define MAXTC 6                 /* maximum time constant (shift) */
  78
  79 /*
  80  * The SHIFT_SCALE define establishes the decimal point of the time_phase
  81  * variable which serves as an extension to the low-order bits of the
  82  * system clock variable. The SHIFT_UPDATE define establishes the decimal
  83  * point of the time_offset variable which represents the current offset
  84  * with respect to standard time. The FINENSEC define represents 1 nsec in
  85  * scaled units.
  86  *
  87  * SHIFT_USEC defines the scaling (shift) of the time_freq and
  88  * time_tolerance variables, which represent the current frequency
  89  * offset and maximum frequency tolerance.
  90  *
  91  * FINENSEC is 1 ns in SHIFT_UPDATE units of the time_phase variable.
  92  */
  93 #define SHIFT_SCALE 22          /* phase scale (shift) */
  94 #define SHIFT_UPDATE (SHIFT_KG + MAXTC) /* time offset scale (shift) */
  95 #define SHIFT_USEC 16           /* frequency offset scale (shift) */
  96 #define FINENSEC (1L << (SHIFT_SCALE - 10)) /* ~1 ns in phase units */
  97
  98 #define MAXPHASE 512000L        /* max phase error (us) */
  99 #define MAXFREQ (512L << SHIFT_USEC)  /* max frequency error (ppm) */
 100 #define MAXTIME (200L << PPS_AVG) /* max PPS error (jitter) (200 us) */
 101 #define MINSEC 16L              /* min interval between updates (s) */
 102 #define MAXSEC 1200L            /* max interval between updates (s) */
 103 #define NTP_PHASE_LIMIT (MAXPHASE << 5) /* beyond max. dispersion */
 104
 105 /*
 106  * The following defines are used only if a pulse-per-second (PPS)
 107  * signal is available and connected via a modem control lead, such as
 108  * produced by the optional ppsclock feature incorporated in the Sun
 109  * asynch driver. They establish the design parameters of the frequency-
 110  * lock loop used to discipline the CPU clock oscillator to the PPS
 111  * signal.
 112  *
 113  * PPS_AVG is the averaging factor for the frequency loop, as well as
 114  * the time and frequency dispersion.
 115  *
 116  * PPS_SHIFT and PPS_SHIFTMAX specify the minimum and maximum
 117  * calibration intervals, respectively, in seconds as a power of two.
 118  *
 119  * PPS_VALID is the maximum interval before the PPS signal is considered
 120  * invalid and protocol updates used directly instead.
 121  *
 122  * MAXGLITCH is the maximum interval before a time offset of more than
 123  * MAXTIME is believed.
 124  */
 125 #define PPS_AVG 2               /* pps averaging constant (shift) */
 126 #define PPS_SHIFT 2             /* min interval duration (s) (shift) */
 127 #define PPS_SHIFTMAX 8          /* max interval duration (s) (shift) */
 128 #define PPS_VALID 120           /* pps signal watchdog max (s) */
 129 #define MAXGLITCH 30            /* pps signal glitch max (s) */
 130
 131 /*
 132  * syscall interface - used (mainly by NTP daemon)
 133  * to discipline kernel clock oscillator
 134  */
 135 struct timex {
 136         unsigned int modes;     /* mode selector */
 137         long offset;            /* time offset (usec) */
 138         long freq;              /* frequency offset (scaled ppm) */
 139         long maxerror;          /* maximum error (usec) */
 140         long esterror;          /* estimated error (usec) */
 141         int status;             /* clock command/status */
 142         long constant;          /* pll time constant */
 143         long precision;         /* clock precision (usec) (read only) */
 144         long tolerance;         /* clock frequency tolerance (ppm)
 145                                  * (read only)
 146                                  */
 147         struct timeval time;    /* (read only) */
 148         long tick;              /* (modified) usecs between clock ticks */
 149
 150         long ppsfreq;           /* pps frequency (scaled ppm) (ro) */
 151         long jitter;            /* pps jitter (us) (ro) */
 152         int shift;              /* interval duration (s) (shift) (ro) */
 153         long stabil;            /* pps stability (scaled ppm) (ro) */
 154         long jitcnt;            /* jitter limit exceeded (ro) */
 155         long calcnt;            /* calibration intervals (ro) */
 156         long errcnt;            /* calibration errors (ro) */
 157         long stbcnt;            /* stability limit exceeded (ro) */
 158
 159         int  :32; int  :32; int  :32; int  :32;
 160         int  :32; int  :32; int  :32; int  :32;
 161         int  :32; int  :32; int  :32; int  :32;
 162 };
 163
 164 /*
 165  * Mode codes (timex.mode)
 166  */
 167 #define ADJ_OFFSET              0x0001  /* time offset */
 168 #define ADJ_FREQUENCY           0x0002  /* frequency offset */
 169 #define ADJ_MAXERROR            0x0004  /* maximum time error */
 170 #define ADJ_ESTERROR            0x0008  /* estimated time error */
 171 #define ADJ_STATUS              0x0010  /* clock status */
 172 #define ADJ_TIMECONST           0x0020  /* pll time constant */
 173 #define ADJ_TICK                0x4000  /* tick value */
 174 #define ADJ_OFFSET_SINGLESHOT   0x8001  /* old-fashioned adjtime */
 175
 176 /* xntp 3.4 compatibility names */
 177 #define MOD_OFFSET      ADJ_OFFSET
 178 #define MOD_FREQUENCY   ADJ_FREQUENCY
 179 #define MOD_MAXERROR    ADJ_MAXERROR
 180 #define MOD_ESTERROR    ADJ_ESTERROR
 181 #define MOD_STATUS      ADJ_STATUS
 182 #define MOD_TIMECONST   ADJ_TIMECONST
 183 #define MOD_CLKB        ADJ_TICK
 184 #define MOD_CLKA        ADJ_OFFSET_SINGLESHOT /* 0x8000 in original */
 185
 186
 187 /*
 188  * Status codes (timex.status)
 189  */
 190 #define STA_PLL         0x0001  /* enable PLL updates (rw) */
 191 #define STA_PPSFREQ     0x0002  /* enable PPS freq discipline (rw) */
 192 #define STA_PPSTIME     0x0004  /* enable PPS time discipline (rw) */
 193 #define STA_FLL         0x0008  /* select frequency-lock mode (rw) */
 194
 195 #define STA_INS         0x0010  /* insert leap (rw) */
 196 #define STA_DEL         0x0020  /* delete leap (rw) */
 197 #define STA_UNSYNC      0x0040  /* clock unsynchronized (rw) */
 198 #define STA_FREQHOLD    0x0080  /* hold frequency (rw) */
 199
 200 #define STA_PPSSIGNAL   0x0100  /* PPS signal present (ro) */
 201 #define STA_PPSJITTER   0x0200  /* PPS signal jitter exceeded (ro) */
 202 #define STA_PPSWANDER   0x0400  /* PPS signal wander exceeded (ro) */
 203 #define STA_PPSERROR    0x0800  /* PPS signal calibration error (ro) */
 204
 205 #define STA_CLOCKERR    0x1000  /* clock hardware fault (ro) */
 206
 207 #define STA_RONLY (STA_PPSSIGNAL | STA_PPSJITTER | STA_PPSWANDER | \
 208     STA_PPSERROR | STA_CLOCKERR) /* read-only bits */
 209
 210 /*
 211  * Clock states (time_state)
 212  */
 213 #define TIME_OK         0       /* clock synchronized, no leap second */
 214 #define TIME_INS        1       /* insert leap second */
 215 #define TIME_DEL        2       /* delete leap second */
 216 #define TIME_OOP        3       /* leap second in progress */
 217 #define TIME_WAIT       4       /* leap second has occurred */
 218 #define TIME_ERROR      5       /* clock not synchronized */
 219 #define TIME_BAD        TIME_ERROR /* bw compat */
 220
 221 #ifdef __KERNEL__
 222 /*
 223  * kernel variables
 224  * Note: maximum error = NTP synch distance = dispersion + delay / 2;
 225  * estimated error = NTP dispersion.
 226  */
 227 extern unsigned long tick_usec;         /* USER_HZ period (usec) */
 228 extern unsigned long tick_nsec;         /* ACTHZ          period (nsec) */
 229 extern int tickadj;                     /* amount of adjustment per tick */
 230
 231 /*
 232  * phase-lock loop variables
 233  */
 234 extern int time_state;          /* clock status */
 235 extern int time_status;         /* clock synchronization status bits */
 236 extern long time_offset;        /* time adjustment (us) */
 237 extern long time_constant;      /* pll time constant */
 238 extern long time_tolerance;     /* frequency tolerance (ppm) */
 239 extern long time_precision;     /* clock precision (us) */
 240 extern long time_maxerror;      /* maximum error */
 241 extern long time_esterror;      /* estimated error */
 242
 243 extern long time_freq;          /* frequency offset (scaled ppm) */
 244 extern long time_reftime;       /* time at last adjustment (s) */
 245
 246 extern long time_adjust;        /* The amount of adjtime left */
 247 extern long time_next_adjust;   /* Value for time_adjust at next tick */
 248
 249 /* interface variables pps->timer interrupt */
 250 extern long pps_offset;         /* pps time offset (us) */
 251 extern long pps_jitter;         /* time dispersion (jitter) (us) */
 252 extern long pps_freq;           /* frequency offset (scaled ppm) */
 253 extern long pps_stabil;         /* frequency dispersion (scaled ppm) */
 254 extern long pps_valid;          /* pps signal watchdog counter */
 255
 256 /* interface variables pps->adjtimex */
 257 extern int pps_shift;           /* interval duration (s) (shift) */
 258 extern long pps_jitcnt;         /* jitter limit exceeded */
 259 extern long pps_calcnt;         /* calibration intervals */
 260 extern long pps_errcnt;         /* calibration errors */
 261 extern long pps_stbcnt;         /* stability limit exceeded */
 262
 263 /**
 264  * ntp_clear - Clears the NTP state variables
 265  *
 266  * Must be called while holding a write on the xtime_lock
 267  */
 268 static inline void ntp_clear(void)
 269 {
 270         time_adjust = 0;                /* stop active adjtime() */
 271         time_status |= STA_UNSYNC;
 272         time_maxerror = NTP_PHASE_LIMIT;
 273         time_esterror = NTP_PHASE_LIMIT;
 274 }
 275
 276 /**
 277  * ntp_synced - Returns 1 if the NTP status is not UNSYNC
 278  *
 279  */
 280 static inline int ntp_synced(void)
 281 {
 282         return !(time_status & STA_UNSYNC);
 283 }
 284
 285 /* Required to safely shift negative values */
 286 #define shift_right(x, s) ({    \
 287         __typeof__(x) __x = (x);        \
 288         __typeof__(s) __s = (s);        \
 289         __x < 0 ? -(-__x >> __s) : __x >> __s;  \
 290 })
 291
 292
 293 #ifdef CONFIG_TIME_INTERPOLATION
 294
 295 #define TIME_SOURCE_CPU 0
 296 #define TIME_SOURCE_MMIO64 1
 297 #define TIME_SOURCE_MMIO32 2
 298 #define TIME_SOURCE_FUNCTION 3
 299
 300 /* For proper operations time_interpolator clocks must run slightly slower
 301  * than the standard clock since the interpolator may only correct by having
 302  * time jump forward during a tick. A slower clock is usually a side effect
 303  * of the integer divide of the nanoseconds in a second by the frequency.
 304  * The accuracy of the division can be increased by specifying a shift.
 305  * However, this may cause the clock not to be slow enough.
 306  * The interpolator will self-tune the clock by slowing down if no
 307  * resets occur or speeding up if the time jumps per analysis cycle
 308  * become too high.
 309  *
 310  * Setting jitter compensates for a fluctuating timesource by comparing
 311  * to the last value read from the timesource to insure that an earlier value
 312  * is not returned by a later call. The price to pay
 313  * for the compensation is that the timer routines are not as scalable anymore.
 314  */
 315
 316 struct time_interpolator {
 317         u16 source;                     /* time source flags */
 318         u8 shift;                       /* increases accuracy of multiply by shifting. */
 319                                 /* Note that bits may be lost if shift is set too high */
 320         u8 jitter;                      /* if set compensate for fluctuations */
 321         u32 nsec_per_cyc;               /* set by register_time_interpolator() */
 322         void *addr;                     /* address of counter or function */
 323         u64 mask;                       /* mask the valid bits of the counter */
 324         unsigned long offset;           /* nsec offset at last update of interpolator */
 325         u64 last_counter;               /* counter value in units of the counter at last update */
 326         u64 last_cycle;                 /* Last timer value if TIME_SOURCE_JITTER is set */
 327         u64 frequency;                  /* frequency in counts/second */
 328         long drift;                     /* drift in parts-per-million (or -1) */
 329         unsigned long skips;            /* skips forward */
 330         unsigned long ns_skipped;       /* nanoseconds skipped */
 331         struct time_interpolator *next;
 332 };
 333
 334 extern void register_time_interpolator(struct time_interpolator *);
 335 extern void unregister_time_interpolator(struct time_interpolator *);
 336 extern void time_interpolator_reset(void);
 337 extern unsigned long time_interpolator_get_offset(void);
 338
 339 #else /* !CONFIG_TIME_INTERPOLATION */
 340
 341 static inline void
 342 time_interpolator_reset(void)
 343 {
 344 }
 345
 346 #endif /* !CONFIG_TIME_INTERPOLATION */
 347
 348 /* Returns how long ticks are at present, in ns / 2^(SHIFT_SCALE-10). */
 349 extern u64 current_tick_length(void);
 350
 351 #endif /* KERNEL */
 352
 353 #endif /* LINUX_TIMEX_H */