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Commit | Line | Data |
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4c7ee8de JS |
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 | /* Don't completely fail for HZ > 500. */ | |
19 | int tickadj = 500/HZ ? : 1; /* microsecs */ | |
20 | ||
21 | /* | |
22 | * phase-lock loop variables | |
23 | */ | |
24 | /* TIME_ERROR prevents overwriting the CMOS clock */ | |
25 | int time_state = TIME_OK; /* clock synchronization status */ | |
26 | int time_status = STA_UNSYNC; /* clock status bits */ | |
27 | long time_offset; /* time adjustment (us) */ | |
28 | long time_constant = 2; /* pll time constant */ | |
29 | long time_tolerance = MAXFREQ; /* frequency tolerance (ppm) */ | |
30 | long time_precision = 1; /* clock precision (us) */ | |
31 | long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */ | |
32 | long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */ | |
33 | long time_freq = (((NSEC_PER_SEC + HZ/2) % HZ - HZ/2) << SHIFT_USEC) / NSEC_PER_USEC; | |
34 | /* frequency offset (scaled ppm)*/ | |
35 | static long time_adj; /* tick adjust (scaled 1 / HZ) */ | |
36 | long time_reftime; /* time at last adjustment (s) */ | |
37 | long time_adjust; | |
38 | long time_next_adjust; | |
39 | ||
40 | /* | |
41 | * this routine handles the overflow of the microsecond field | |
42 | * | |
43 | * The tricky bits of code to handle the accurate clock support | |
44 | * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. | |
45 | * They were originally developed for SUN and DEC kernels. | |
46 | * All the kudos should go to Dave for this stuff. | |
47 | */ | |
48 | void second_overflow(void) | |
49 | { | |
50 | long ltemp; | |
51 | ||
52 | /* Bump the maxerror field */ | |
53 | time_maxerror += time_tolerance >> SHIFT_USEC; | |
54 | if (time_maxerror > NTP_PHASE_LIMIT) { | |
55 | time_maxerror = NTP_PHASE_LIMIT; | |
56 | time_status |= STA_UNSYNC; | |
57 | } | |
58 | ||
59 | /* | |
60 | * Leap second processing. If in leap-insert state at the end of the | |
61 | * day, the system clock is set back one second; if in leap-delete | |
62 | * state, the system clock is set ahead one second. The microtime() | |
63 | * routine or external clock driver will insure that reported time is | |
64 | * always monotonic. The ugly divides should be replaced. | |
65 | */ | |
66 | switch (time_state) { | |
67 | case TIME_OK: | |
68 | if (time_status & STA_INS) | |
69 | time_state = TIME_INS; | |
70 | else if (time_status & STA_DEL) | |
71 | time_state = TIME_DEL; | |
72 | break; | |
73 | case TIME_INS: | |
74 | if (xtime.tv_sec % 86400 == 0) { | |
75 | xtime.tv_sec--; | |
76 | wall_to_monotonic.tv_sec++; | |
77 | /* | |
78 | * The timer interpolator will make time change | |
79 | * gradually instead of an immediate jump by one second | |
80 | */ | |
81 | time_interpolator_update(-NSEC_PER_SEC); | |
82 | time_state = TIME_OOP; | |
83 | clock_was_set(); | |
84 | printk(KERN_NOTICE "Clock: inserting leap second " | |
85 | "23:59:60 UTC\n"); | |
86 | } | |
87 | break; | |
88 | case TIME_DEL: | |
89 | if ((xtime.tv_sec + 1) % 86400 == 0) { | |
90 | xtime.tv_sec++; | |
91 | wall_to_monotonic.tv_sec--; | |
92 | /* | |
93 | * Use of time interpolator for a gradual change of | |
94 | * time | |
95 | */ | |
96 | time_interpolator_update(NSEC_PER_SEC); | |
97 | time_state = TIME_WAIT; | |
98 | clock_was_set(); | |
99 | printk(KERN_NOTICE "Clock: deleting leap second " | |
100 | "23:59:59 UTC\n"); | |
101 | } | |
102 | break; | |
103 | case TIME_OOP: | |
104 | time_state = TIME_WAIT; | |
105 | break; | |
106 | case TIME_WAIT: | |
107 | if (!(time_status & (STA_INS | STA_DEL))) | |
108 | time_state = TIME_OK; | |
109 | } | |
110 | ||
111 | /* | |
112 | * Compute the phase adjustment for the next second. In PLL mode, the | |
113 | * offset is reduced by a fixed factor times the time constant. In FLL | |
114 | * mode the offset is used directly. In either mode, the maximum phase | |
115 | * adjustment for each second is clamped so as to spread the adjustment | |
116 | * over not more than the number of seconds between updates. | |
117 | */ | |
118 | ltemp = time_offset; | |
119 | if (!(time_status & STA_FLL)) | |
120 | ltemp = shift_right(ltemp, SHIFT_KG + time_constant); | |
121 | ltemp = min(ltemp, (MAXPHASE / MINSEC) << SHIFT_UPDATE); | |
122 | ltemp = max(ltemp, -(MAXPHASE / MINSEC) << SHIFT_UPDATE); | |
123 | time_offset -= ltemp; | |
124 | time_adj = ltemp << (SHIFT_SCALE - SHIFT_HZ - SHIFT_UPDATE); | |
125 | ||
126 | /* | |
127 | * Compute the frequency estimate and additional phase adjustment due | |
128 | * to frequency error for the next second. | |
129 | */ | |
130 | ltemp = time_freq; | |
131 | time_adj += shift_right(ltemp,(SHIFT_USEC + SHIFT_HZ - SHIFT_SCALE)); | |
132 | ||
133 | #if HZ == 100 | |
134 | /* | |
135 | * Compensate for (HZ==100) != (1 << SHIFT_HZ). Add 25% and 3.125% to | |
136 | * get 128.125; => only 0.125% error (p. 14) | |
137 | */ | |
138 | time_adj += shift_right(time_adj, 2) + shift_right(time_adj, 5); | |
139 | #endif | |
140 | #if HZ == 250 | |
141 | /* | |
142 | * Compensate for (HZ==250) != (1 << SHIFT_HZ). Add 1.5625% and | |
143 | * 0.78125% to get 255.85938; => only 0.05% error (p. 14) | |
144 | */ | |
145 | time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7); | |
146 | #endif | |
147 | #if HZ == 1000 | |
148 | /* | |
149 | * Compensate for (HZ==1000) != (1 << SHIFT_HZ). Add 1.5625% and | |
150 | * 0.78125% to get 1023.4375; => only 0.05% error (p. 14) | |
151 | */ | |
152 | time_adj += shift_right(time_adj, 6) + shift_right(time_adj, 7); | |
153 | #endif | |
154 | } | |
155 | ||
156 | /* | |
157 | * Returns how many microseconds we need to add to xtime this tick | |
158 | * in doing an adjustment requested with adjtime. | |
159 | */ | |
160 | static long adjtime_adjustment(void) | |
161 | { | |
162 | long time_adjust_step; | |
163 | ||
164 | time_adjust_step = time_adjust; | |
165 | if (time_adjust_step) { | |
166 | /* | |
167 | * We are doing an adjtime thing. Prepare time_adjust_step to | |
168 | * be within bounds. Note that a positive time_adjust means we | |
169 | * want the clock to run faster. | |
170 | * | |
171 | * Limit the amount of the step to be in the range | |
172 | * -tickadj .. +tickadj | |
173 | */ | |
174 | time_adjust_step = min(time_adjust_step, (long)tickadj); | |
175 | time_adjust_step = max(time_adjust_step, (long)-tickadj); | |
176 | } | |
177 | return time_adjust_step; | |
178 | } | |
179 | ||
180 | /* in the NTP reference this is called "hardclock()" */ | |
181 | void update_ntp_one_tick(void) | |
182 | { | |
183 | long time_adjust_step; | |
184 | ||
185 | time_adjust_step = adjtime_adjustment(); | |
186 | if (time_adjust_step) | |
187 | /* Reduce by this step the amount of time left */ | |
188 | time_adjust -= time_adjust_step; | |
189 | ||
190 | /* Changes by adjtime() do not take effect till next tick. */ | |
191 | if (time_next_adjust != 0) { | |
192 | time_adjust = time_next_adjust; | |
193 | time_next_adjust = 0; | |
194 | } | |
195 | } | |
196 | ||
197 | /* | |
198 | * Return how long ticks are at the moment, that is, how much time | |
199 | * update_wall_time_one_tick will add to xtime next time we call it | |
200 | * (assuming no calls to do_adjtimex in the meantime). | |
201 | * The return value is in fixed-point nanoseconds shifted by the | |
202 | * specified number of bits to the right of the binary point. | |
203 | * This function has no side-effects. | |
204 | */ | |
205 | u64 current_tick_length(void) | |
206 | { | |
207 | long delta_nsec; | |
208 | u64 ret; | |
209 | ||
210 | /* calculate the finest interval NTP will allow. | |
211 | * ie: nanosecond value shifted by (SHIFT_SCALE - 10) | |
212 | */ | |
213 | delta_nsec = tick_nsec + adjtime_adjustment() * 1000; | |
214 | ret = (u64)delta_nsec << TICK_LENGTH_SHIFT; | |
215 | ret += (s64)time_adj << (TICK_LENGTH_SHIFT - (SHIFT_SCALE - 10)); | |
216 | ||
217 | return ret; | |
218 | } | |
219 | ||
220 | ||
221 | void __attribute__ ((weak)) notify_arch_cmos_timer(void) | |
222 | { | |
223 | return; | |
224 | } | |
225 | ||
226 | /* adjtimex mainly allows reading (and writing, if superuser) of | |
227 | * kernel time-keeping variables. used by xntpd. | |
228 | */ | |
229 | int do_adjtimex(struct timex *txc) | |
230 | { | |
231 | long ltemp, mtemp, save_adjust; | |
232 | int result; | |
233 | ||
234 | /* In order to modify anything, you gotta be super-user! */ | |
235 | if (txc->modes && !capable(CAP_SYS_TIME)) | |
236 | return -EPERM; | |
237 | ||
238 | /* Now we validate the data before disabling interrupts */ | |
239 | ||
240 | if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) | |
241 | /* singleshot must not be used with any other mode bits */ | |
242 | if (txc->modes != ADJ_OFFSET_SINGLESHOT) | |
243 | return -EINVAL; | |
244 | ||
245 | if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET)) | |
246 | /* adjustment Offset limited to +- .512 seconds */ | |
247 | if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE ) | |
248 | return -EINVAL; | |
249 | ||
250 | /* if the quartz is off by more than 10% something is VERY wrong ! */ | |
251 | if (txc->modes & ADJ_TICK) | |
252 | if (txc->tick < 900000/USER_HZ || | |
253 | txc->tick > 1100000/USER_HZ) | |
254 | return -EINVAL; | |
255 | ||
256 | write_seqlock_irq(&xtime_lock); | |
257 | result = time_state; /* mostly `TIME_OK' */ | |
258 | ||
259 | /* Save for later - semantics of adjtime is to return old value */ | |
260 | save_adjust = time_next_adjust ? time_next_adjust : time_adjust; | |
261 | ||
262 | #if 0 /* STA_CLOCKERR is never set yet */ | |
263 | time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */ | |
264 | #endif | |
265 | /* If there are input parameters, then process them */ | |
266 | if (txc->modes) | |
267 | { | |
268 | if (txc->modes & ADJ_STATUS) /* only set allowed bits */ | |
269 | time_status = (txc->status & ~STA_RONLY) | | |
270 | (time_status & STA_RONLY); | |
271 | ||
272 | if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */ | |
273 | if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) { | |
274 | result = -EINVAL; | |
275 | goto leave; | |
276 | } | |
277 | time_freq = txc->freq; | |
278 | } | |
279 | ||
280 | if (txc->modes & ADJ_MAXERROR) { | |
281 | if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) { | |
282 | result = -EINVAL; | |
283 | goto leave; | |
284 | } | |
285 | time_maxerror = txc->maxerror; | |
286 | } | |
287 | ||
288 | if (txc->modes & ADJ_ESTERROR) { | |
289 | if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) { | |
290 | result = -EINVAL; | |
291 | goto leave; | |
292 | } | |
293 | time_esterror = txc->esterror; | |
294 | } | |
295 | ||
296 | if (txc->modes & ADJ_TIMECONST) { /* p. 24 */ | |
297 | if (txc->constant < 0) { /* NTP v4 uses values > 6 */ | |
298 | result = -EINVAL; | |
299 | goto leave; | |
300 | } | |
301 | time_constant = txc->constant; | |
302 | } | |
303 | ||
304 | if (txc->modes & ADJ_OFFSET) { /* values checked earlier */ | |
305 | if (txc->modes == ADJ_OFFSET_SINGLESHOT) { | |
306 | /* adjtime() is independent from ntp_adjtime() */ | |
307 | if ((time_next_adjust = txc->offset) == 0) | |
308 | time_adjust = 0; | |
309 | } | |
310 | else if (time_status & STA_PLL) { | |
311 | ltemp = txc->offset; | |
312 | ||
313 | /* | |
314 | * Scale the phase adjustment and | |
315 | * clamp to the operating range. | |
316 | */ | |
317 | if (ltemp > MAXPHASE) | |
318 | time_offset = MAXPHASE << SHIFT_UPDATE; | |
319 | else if (ltemp < -MAXPHASE) | |
320 | time_offset = -(MAXPHASE << SHIFT_UPDATE); | |
321 | else | |
322 | time_offset = ltemp << SHIFT_UPDATE; | |
323 | ||
324 | /* | |
325 | * Select whether the frequency is to be controlled | |
326 | * and in which mode (PLL or FLL). Clamp to the operating | |
327 | * range. Ugly multiply/divide should be replaced someday. | |
328 | */ | |
329 | ||
330 | if (time_status & STA_FREQHOLD || time_reftime == 0) | |
331 | time_reftime = xtime.tv_sec; | |
332 | mtemp = xtime.tv_sec - time_reftime; | |
333 | time_reftime = xtime.tv_sec; | |
334 | if (time_status & STA_FLL) { | |
335 | if (mtemp >= MINSEC) { | |
336 | ltemp = (time_offset / mtemp) << (SHIFT_USEC - | |
337 | SHIFT_UPDATE); | |
338 | time_freq += shift_right(ltemp, SHIFT_KH); | |
339 | } else /* calibration interval too short (p. 12) */ | |
340 | result = TIME_ERROR; | |
341 | } else { /* PLL mode */ | |
342 | if (mtemp < MAXSEC) { | |
343 | ltemp *= mtemp; | |
344 | time_freq += shift_right(ltemp,(time_constant + | |
345 | time_constant + | |
346 | SHIFT_KF - SHIFT_USEC)); | |
347 | } else /* calibration interval too long (p. 12) */ | |
348 | result = TIME_ERROR; | |
349 | } | |
350 | time_freq = min(time_freq, time_tolerance); | |
351 | time_freq = max(time_freq, -time_tolerance); | |
352 | } /* STA_PLL */ | |
353 | } /* txc->modes & ADJ_OFFSET */ | |
354 | if (txc->modes & ADJ_TICK) { | |
355 | tick_usec = txc->tick; | |
356 | tick_nsec = TICK_USEC_TO_NSEC(tick_usec); | |
357 | } | |
358 | } /* txc->modes */ | |
359 | leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0) | |
360 | result = TIME_ERROR; | |
361 | ||
362 | if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) | |
363 | txc->offset = save_adjust; | |
364 | else { | |
365 | txc->offset = shift_right(time_offset, SHIFT_UPDATE); | |
366 | } | |
367 | txc->freq = time_freq; | |
368 | txc->maxerror = time_maxerror; | |
369 | txc->esterror = time_esterror; | |
370 | txc->status = time_status; | |
371 | txc->constant = time_constant; | |
372 | txc->precision = time_precision; | |
373 | txc->tolerance = time_tolerance; | |
374 | txc->tick = tick_usec; | |
375 | ||
376 | /* PPS is not implemented, so these are zero */ | |
377 | txc->ppsfreq = 0; | |
378 | txc->jitter = 0; | |
379 | txc->shift = 0; | |
380 | txc->stabil = 0; | |
381 | txc->jitcnt = 0; | |
382 | txc->calcnt = 0; | |
383 | txc->errcnt = 0; | |
384 | txc->stbcnt = 0; | |
385 | write_sequnlock_irq(&xtime_lock); | |
386 | do_gettimeofday(&txc->time); | |
387 | notify_arch_cmos_timer(); | |
388 | return(result); | |
389 | } |