1 /* 2 * linux/kernel/time/ntp.c 3 * 4 * NTP state machine interfaces and logic. 5 * 6 * This code was mainly moved from kernel/timer.c and kernel/time.c 7 * Please see those files for relevant copyright info and historical 8 * changelogs. 9 */ 10 11 #include <linux/mm.h> 12 #include <linux/time.h> 13 #include <linux/timex.h> 14 15 #include <asm/div64.h> 16 #include <asm/timex.h> 17 18 /* 19 * Timekeeping variables 20 */ 21 unsigned long tick_usec = TICK_USEC; /* USER_HZ period (usec) */ 22 unsigned long tick_nsec; /* ACTHZ period (nsec) */ 23 static u64 tick_length, tick_length_base; 24 25 #define MAX_TICKADJ 500 /* microsecs */ 26 #define MAX_TICKADJ_SCALED (((u64)(MAX_TICKADJ * NSEC_PER_USEC) << \ 27 TICK_LENGTH_SHIFT) / HZ) 28 29 /* 30 * phase-lock loop variables 31 */ 32 /* TIME_ERROR prevents overwriting the CMOS clock */ 33 static int time_state = TIME_OK; /* clock synchronization status */ 34 int time_status = STA_UNSYNC; /* clock status bits */ 35 static long time_offset; /* time adjustment (ns) */ 36 static long time_constant = 2; /* pll time constant */ 37 long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */ 38 long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */ 39 long time_freq; /* frequency offset (scaled ppm)*/ 40 static long time_reftime; /* time at last adjustment (s) */ 41 long time_adjust; 42 43 #define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE) 44 #define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / \ 45 (s64)CLOCK_TICK_RATE) 46 47 static void ntp_update_frequency(void) 48 { 49 tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT; 50 tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT; 51 tick_length_base += (s64)time_freq << (TICK_LENGTH_SHIFT - SHIFT_NSEC); 52 53 do_div(tick_length_base, HZ); 54 55 tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT; 56 } 57 58 /** 59 * ntp_clear - Clears the NTP state variables 60 * 61 * Must be called while holding a write on the xtime_lock 62 */ 63 void ntp_clear(void) 64 { 65 time_adjust = 0; /* stop active adjtime() */ 66 time_status |= STA_UNSYNC; 67 time_maxerror = NTP_PHASE_LIMIT; 68 time_esterror = NTP_PHASE_LIMIT; 69 70 ntp_update_frequency(); 71 72 tick_length = tick_length_base; 73 time_offset = 0; 74 } 75 76 /* 77 * this routine handles the overflow of the microsecond field 78 * 79 * The tricky bits of code to handle the accurate clock support 80 * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. 81 * They were originally developed for SUN and DEC kernels. 82 * All the kudos should go to Dave for this stuff. 83 */ 84 void second_overflow(void) 85 { 86 long time_adj; 87 88 /* Bump the maxerror field */ 89 time_maxerror += MAXFREQ >> SHIFT_USEC; 90 if (time_maxerror > NTP_PHASE_LIMIT) { 91 time_maxerror = NTP_PHASE_LIMIT; 92 time_status |= STA_UNSYNC; 93 } 94 95 /* 96 * Leap second processing. If in leap-insert state at the end of the 97 * day, the system clock is set back one second; if in leap-delete 98 * state, the system clock is set ahead one second. The microtime() 99 * routine or external clock driver will insure that reported time is 100 * always monotonic. The ugly divides should be replaced. 101 */ 102 switch (time_state) { 103 case TIME_OK: 104 if (time_status & STA_INS) 105 time_state = TIME_INS; 106 else if (time_status & STA_DEL) 107 time_state = TIME_DEL; 108 break; 109 case TIME_INS: 110 if (xtime.tv_sec % 86400 == 0) { 111 xtime.tv_sec--; 112 wall_to_monotonic.tv_sec++; 113 /* 114 * The timer interpolator will make time change 115 * gradually instead of an immediate jump by one second 116 */ 117 time_interpolator_update(-NSEC_PER_SEC); 118 time_state = TIME_OOP; 119 clock_was_set(); 120 printk(KERN_NOTICE "Clock: inserting leap second " 121 "23:59:60 UTC\n"); 122 } 123 break; 124 case TIME_DEL: 125 if ((xtime.tv_sec + 1) % 86400 == 0) { 126 xtime.tv_sec++; 127 wall_to_monotonic.tv_sec--; 128 /* 129 * Use of time interpolator for a gradual change of 130 * time 131 */ 132 time_interpolator_update(NSEC_PER_SEC); 133 time_state = TIME_WAIT; 134 clock_was_set(); 135 printk(KERN_NOTICE "Clock: deleting leap second " 136 "23:59:59 UTC\n"); 137 } 138 break; 139 case TIME_OOP: 140 time_state = TIME_WAIT; 141 break; 142 case TIME_WAIT: 143 if (!(time_status & (STA_INS | STA_DEL))) 144 time_state = TIME_OK; 145 } 146 147 /* 148 * Compute the phase adjustment for the next second. The offset is 149 * reduced by a fixed factor times the time constant. 150 */ 151 tick_length = tick_length_base; 152 time_adj = shift_right(time_offset, SHIFT_PLL + time_constant); 153 time_offset -= time_adj; 154 tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE); 155 156 if (unlikely(time_adjust)) { 157 if (time_adjust > MAX_TICKADJ) { 158 time_adjust -= MAX_TICKADJ; 159 tick_length += MAX_TICKADJ_SCALED; 160 } else if (time_adjust < -MAX_TICKADJ) { 161 time_adjust += MAX_TICKADJ; 162 tick_length -= MAX_TICKADJ_SCALED; 163 } else { 164 tick_length += (s64)(time_adjust * NSEC_PER_USEC / 165 HZ) << TICK_LENGTH_SHIFT; 166 time_adjust = 0; 167 } 168 } 169 } 170 171 /* 172 * Return how long ticks are at the moment, that is, how much time 173 * update_wall_time_one_tick will add to xtime next time we call it 174 * (assuming no calls to do_adjtimex in the meantime). 175 * The return value is in fixed-point nanoseconds shifted by the 176 * specified number of bits to the right of the binary point. 177 * This function has no side-effects. 178 */ 179 u64 current_tick_length(void) 180 { 181 return tick_length; 182 } 183 184 185 void __attribute__ ((weak)) notify_arch_cmos_timer(void) 186 { 187 return; 188 } 189 190 /* adjtimex mainly allows reading (and writing, if superuser) of 191 * kernel time-keeping variables. used by xntpd. 192 */ 193 int do_adjtimex(struct timex *txc) 194 { 195 long ltemp, mtemp, save_adjust; 196 s64 freq_adj, temp64; 197 int result; 198 199 /* In order to modify anything, you gotta be super-user! */ 200 if (txc->modes && !capable(CAP_SYS_TIME)) 201 return -EPERM; 202 203 /* Now we validate the data before disabling interrupts */ 204 205 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) 206 /* singleshot must not be used with any other mode bits */ 207 if (txc->modes != ADJ_OFFSET_SINGLESHOT) 208 return -EINVAL; 209 210 if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET)) 211 /* adjustment Offset limited to +- .512 seconds */ 212 if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE ) 213 return -EINVAL; 214 215 /* if the quartz is off by more than 10% something is VERY wrong ! */ 216 if (txc->modes & ADJ_TICK) 217 if (txc->tick < 900000/USER_HZ || 218 txc->tick > 1100000/USER_HZ) 219 return -EINVAL; 220 221 write_seqlock_irq(&xtime_lock); 222 result = time_state; /* mostly `TIME_OK' */ 223 224 /* Save for later - semantics of adjtime is to return old value */ 225 save_adjust = time_adjust; 226 227 #if 0 /* STA_CLOCKERR is never set yet */ 228 time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */ 229 #endif 230 /* If there are input parameters, then process them */ 231 if (txc->modes) 232 { 233 if (txc->modes & ADJ_STATUS) /* only set allowed bits */ 234 time_status = (txc->status & ~STA_RONLY) | 235 (time_status & STA_RONLY); 236 237 if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */ 238 if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) { 239 result = -EINVAL; 240 goto leave; 241 } 242 time_freq = ((s64)txc->freq * NSEC_PER_USEC) >> (SHIFT_USEC - SHIFT_NSEC); 243 } 244 245 if (txc->modes & ADJ_MAXERROR) { 246 if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) { 247 result = -EINVAL; 248 goto leave; 249 } 250 time_maxerror = txc->maxerror; 251 } 252 253 if (txc->modes & ADJ_ESTERROR) { 254 if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) { 255 result = -EINVAL; 256 goto leave; 257 } 258 time_esterror = txc->esterror; 259 } 260 261 if (txc->modes & ADJ_TIMECONST) { /* p. 24 */ 262 if (txc->constant < 0) { /* NTP v4 uses values > 6 */ 263 result = -EINVAL; 264 goto leave; 265 } 266 time_constant = min(txc->constant + 4, (long)MAXTC); 267 } 268 269 if (txc->modes & ADJ_OFFSET) { /* values checked earlier */ 270 if (txc->modes == ADJ_OFFSET_SINGLESHOT) { 271 /* adjtime() is independent from ntp_adjtime() */ 272 time_adjust = txc->offset; 273 } 274 else if (time_status & STA_PLL) { 275 ltemp = txc->offset * NSEC_PER_USEC; 276 277 /* 278 * Scale the phase adjustment and 279 * clamp to the operating range. 280 */ 281 time_offset = min(ltemp, MAXPHASE * NSEC_PER_USEC); 282 time_offset = max(time_offset, -MAXPHASE * NSEC_PER_USEC); 283 284 /* 285 * Select whether the frequency is to be controlled 286 * and in which mode (PLL or FLL). Clamp to the operating 287 * range. Ugly multiply/divide should be replaced someday. 288 */ 289 290 if (time_status & STA_FREQHOLD || time_reftime == 0) 291 time_reftime = xtime.tv_sec; 292 mtemp = xtime.tv_sec - time_reftime; 293 time_reftime = xtime.tv_sec; 294 295 freq_adj = (s64)time_offset * mtemp; 296 freq_adj = shift_right(freq_adj, time_constant * 2 + 297 (SHIFT_PLL + 2) * 2 - SHIFT_NSEC); 298 if (mtemp >= MINSEC && (time_status & STA_FLL || mtemp > MAXSEC)) { 299 temp64 = (s64)time_offset << (SHIFT_NSEC - SHIFT_FLL); 300 if (time_offset < 0) { 301 temp64 = -temp64; 302 do_div(temp64, mtemp); 303 freq_adj -= temp64; 304 } else { 305 do_div(temp64, mtemp); 306 freq_adj += temp64; 307 } 308 } 309 freq_adj += time_freq; 310 freq_adj = min(freq_adj, (s64)MAXFREQ_NSEC); 311 time_freq = max(freq_adj, (s64)-MAXFREQ_NSEC); 312 time_offset = (time_offset / HZ) << SHIFT_UPDATE; 313 } /* STA_PLL */ 314 } /* txc->modes & ADJ_OFFSET */ 315 if (txc->modes & ADJ_TICK) 316 tick_usec = txc->tick; 317 318 if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) 319 ntp_update_frequency(); 320 } /* txc->modes */ 321 leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0) 322 result = TIME_ERROR; 323 324 if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) 325 txc->offset = save_adjust; 326 else 327 txc->offset = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000; 328 txc->freq = (time_freq / NSEC_PER_USEC) << (SHIFT_USEC - SHIFT_NSEC); 329 txc->maxerror = time_maxerror; 330 txc->esterror = time_esterror; 331 txc->status = time_status; 332 txc->constant = time_constant; 333 txc->precision = 1; 334 txc->tolerance = MAXFREQ; 335 txc->tick = tick_usec; 336 337 /* PPS is not implemented, so these are zero */ 338 txc->ppsfreq = 0; 339 txc->jitter = 0; 340 txc->shift = 0; 341 txc->stabil = 0; 342 txc->jitcnt = 0; 343 txc->calcnt = 0; 344 txc->errcnt = 0; 345 txc->stbcnt = 0; 346 write_sequnlock_irq(&xtime_lock); 347 do_gettimeofday(&txc->time); 348 notify_arch_cmos_timer(); 349 return(result); 350 } 351