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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 | ||
b0ee7556 RZ |
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 | ||
4c7ee8de JS |
25 | /* Don't completely fail for HZ > 500. */ |
26 | int tickadj = 500/HZ ? : 1; /* microsecs */ | |
27 | ||
28 | /* | |
29 | * phase-lock loop variables | |
30 | */ | |
31 | /* TIME_ERROR prevents overwriting the CMOS clock */ | |
32 | int time_state = TIME_OK; /* clock synchronization status */ | |
33 | int time_status = STA_UNSYNC; /* clock status bits */ | |
3d3675cc | 34 | long time_offset; /* time adjustment (ns) */ |
4c7ee8de JS |
35 | long time_constant = 2; /* pll time constant */ |
36 | long time_tolerance = MAXFREQ; /* frequency tolerance (ppm) */ | |
37 | long time_precision = 1; /* clock precision (us) */ | |
38 | long time_maxerror = NTP_PHASE_LIMIT; /* maximum error (us) */ | |
39 | long time_esterror = NTP_PHASE_LIMIT; /* estimated error (us) */ | |
dc6a43e4 | 40 | long time_freq; /* frequency offset (scaled ppm)*/ |
4c7ee8de JS |
41 | long time_reftime; /* time at last adjustment (s) */ |
42 | long time_adjust; | |
43 | long time_next_adjust; | |
44 | ||
b0ee7556 RZ |
45 | /** |
46 | * ntp_clear - Clears the NTP state variables | |
47 | * | |
48 | * Must be called while holding a write on the xtime_lock | |
49 | */ | |
50 | void ntp_clear(void) | |
51 | { | |
52 | time_adjust = 0; /* stop active adjtime() */ | |
53 | time_status |= STA_UNSYNC; | |
54 | time_maxerror = NTP_PHASE_LIMIT; | |
55 | time_esterror = NTP_PHASE_LIMIT; | |
56 | ||
57 | ntp_update_frequency(); | |
58 | ||
59 | tick_length = tick_length_base; | |
3d3675cc | 60 | time_offset = 0; |
b0ee7556 RZ |
61 | } |
62 | ||
63 | #define CLOCK_TICK_OVERFLOW (LATCH * HZ - CLOCK_TICK_RATE) | |
64 | #define CLOCK_TICK_ADJUST (((s64)CLOCK_TICK_OVERFLOW * NSEC_PER_SEC) / (s64)CLOCK_TICK_RATE) | |
65 | ||
66 | void ntp_update_frequency(void) | |
67 | { | |
68 | tick_length_base = (u64)(tick_usec * NSEC_PER_USEC * USER_HZ) << TICK_LENGTH_SHIFT; | |
69 | tick_length_base += (s64)CLOCK_TICK_ADJUST << TICK_LENGTH_SHIFT; | |
dc6a43e4 | 70 | tick_length_base += ((s64)time_freq * NSEC_PER_USEC) << (TICK_LENGTH_SHIFT - SHIFT_USEC); |
b0ee7556 RZ |
71 | |
72 | do_div(tick_length_base, HZ); | |
73 | ||
74 | tick_nsec = tick_length_base >> TICK_LENGTH_SHIFT; | |
75 | } | |
76 | ||
4c7ee8de JS |
77 | /* |
78 | * this routine handles the overflow of the microsecond field | |
79 | * | |
80 | * The tricky bits of code to handle the accurate clock support | |
81 | * were provided by Dave Mills (Mills@UDEL.EDU) of NTP fame. | |
82 | * They were originally developed for SUN and DEC kernels. | |
83 | * All the kudos should go to Dave for this stuff. | |
84 | */ | |
85 | void second_overflow(void) | |
86 | { | |
3d3675cc | 87 | long time_adj; |
4c7ee8de JS |
88 | |
89 | /* Bump the maxerror field */ | |
90 | time_maxerror += time_tolerance >> SHIFT_USEC; | |
91 | if (time_maxerror > NTP_PHASE_LIMIT) { | |
92 | time_maxerror = NTP_PHASE_LIMIT; | |
93 | time_status |= STA_UNSYNC; | |
94 | } | |
95 | ||
96 | /* | |
97 | * Leap second processing. If in leap-insert state at the end of the | |
98 | * day, the system clock is set back one second; if in leap-delete | |
99 | * state, the system clock is set ahead one second. The microtime() | |
100 | * routine or external clock driver will insure that reported time is | |
101 | * always monotonic. The ugly divides should be replaced. | |
102 | */ | |
103 | switch (time_state) { | |
104 | case TIME_OK: | |
105 | if (time_status & STA_INS) | |
106 | time_state = TIME_INS; | |
107 | else if (time_status & STA_DEL) | |
108 | time_state = TIME_DEL; | |
109 | break; | |
110 | case TIME_INS: | |
111 | if (xtime.tv_sec % 86400 == 0) { | |
112 | xtime.tv_sec--; | |
113 | wall_to_monotonic.tv_sec++; | |
114 | /* | |
115 | * The timer interpolator will make time change | |
116 | * gradually instead of an immediate jump by one second | |
117 | */ | |
118 | time_interpolator_update(-NSEC_PER_SEC); | |
119 | time_state = TIME_OOP; | |
120 | clock_was_set(); | |
121 | printk(KERN_NOTICE "Clock: inserting leap second " | |
122 | "23:59:60 UTC\n"); | |
123 | } | |
124 | break; | |
125 | case TIME_DEL: | |
126 | if ((xtime.tv_sec + 1) % 86400 == 0) { | |
127 | xtime.tv_sec++; | |
128 | wall_to_monotonic.tv_sec--; | |
129 | /* | |
130 | * Use of time interpolator for a gradual change of | |
131 | * time | |
132 | */ | |
133 | time_interpolator_update(NSEC_PER_SEC); | |
134 | time_state = TIME_WAIT; | |
135 | clock_was_set(); | |
136 | printk(KERN_NOTICE "Clock: deleting leap second " | |
137 | "23:59:59 UTC\n"); | |
138 | } | |
139 | break; | |
140 | case TIME_OOP: | |
141 | time_state = TIME_WAIT; | |
142 | break; | |
143 | case TIME_WAIT: | |
144 | if (!(time_status & (STA_INS | STA_DEL))) | |
145 | time_state = TIME_OK; | |
146 | } | |
147 | ||
148 | /* | |
149 | * Compute the phase adjustment for the next second. In PLL mode, the | |
150 | * offset is reduced by a fixed factor times the time constant. In FLL | |
151 | * mode the offset is used directly. In either mode, the maximum phase | |
152 | * adjustment for each second is clamped so as to spread the adjustment | |
153 | * over not more than the number of seconds between updates. | |
154 | */ | |
b0ee7556 | 155 | tick_length = tick_length_base; |
3d3675cc RZ |
156 | time_adj = time_offset; |
157 | if (!(time_status & STA_FLL)) | |
158 | time_adj = shift_right(time_adj, SHIFT_KG + time_constant); | |
159 | time_adj = min(time_adj, -((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC); | |
160 | time_adj = max(time_adj, ((MAXPHASE / HZ) << SHIFT_UPDATE) / MINSEC); | |
161 | time_offset -= time_adj; | |
162 | tick_length += (s64)time_adj << (TICK_LENGTH_SHIFT - SHIFT_UPDATE); | |
4c7ee8de JS |
163 | } |
164 | ||
165 | /* | |
166 | * Returns how many microseconds we need to add to xtime this tick | |
167 | * in doing an adjustment requested with adjtime. | |
168 | */ | |
169 | static long adjtime_adjustment(void) | |
170 | { | |
171 | long time_adjust_step; | |
172 | ||
173 | time_adjust_step = time_adjust; | |
174 | if (time_adjust_step) { | |
175 | /* | |
176 | * We are doing an adjtime thing. Prepare time_adjust_step to | |
177 | * be within bounds. Note that a positive time_adjust means we | |
178 | * want the clock to run faster. | |
179 | * | |
180 | * Limit the amount of the step to be in the range | |
181 | * -tickadj .. +tickadj | |
182 | */ | |
183 | time_adjust_step = min(time_adjust_step, (long)tickadj); | |
184 | time_adjust_step = max(time_adjust_step, (long)-tickadj); | |
185 | } | |
186 | return time_adjust_step; | |
187 | } | |
188 | ||
189 | /* in the NTP reference this is called "hardclock()" */ | |
190 | void update_ntp_one_tick(void) | |
191 | { | |
192 | long time_adjust_step; | |
193 | ||
194 | time_adjust_step = adjtime_adjustment(); | |
195 | if (time_adjust_step) | |
196 | /* Reduce by this step the amount of time left */ | |
197 | time_adjust -= time_adjust_step; | |
198 | ||
199 | /* Changes by adjtime() do not take effect till next tick. */ | |
200 | if (time_next_adjust != 0) { | |
201 | time_adjust = time_next_adjust; | |
202 | time_next_adjust = 0; | |
203 | } | |
204 | } | |
205 | ||
206 | /* | |
207 | * Return how long ticks are at the moment, that is, how much time | |
208 | * update_wall_time_one_tick will add to xtime next time we call it | |
209 | * (assuming no calls to do_adjtimex in the meantime). | |
210 | * The return value is in fixed-point nanoseconds shifted by the | |
211 | * specified number of bits to the right of the binary point. | |
212 | * This function has no side-effects. | |
213 | */ | |
214 | u64 current_tick_length(void) | |
215 | { | |
4c7ee8de JS |
216 | u64 ret; |
217 | ||
218 | /* calculate the finest interval NTP will allow. | |
4c7ee8de | 219 | */ |
b0ee7556 RZ |
220 | ret = tick_length; |
221 | ret += (u64)(adjtime_adjustment() * 1000) << TICK_LENGTH_SHIFT; | |
4c7ee8de JS |
222 | |
223 | return ret; | |
224 | } | |
225 | ||
226 | ||
227 | void __attribute__ ((weak)) notify_arch_cmos_timer(void) | |
228 | { | |
229 | return; | |
230 | } | |
231 | ||
232 | /* adjtimex mainly allows reading (and writing, if superuser) of | |
233 | * kernel time-keeping variables. used by xntpd. | |
234 | */ | |
235 | int do_adjtimex(struct timex *txc) | |
236 | { | |
237 | long ltemp, mtemp, save_adjust; | |
238 | int result; | |
239 | ||
240 | /* In order to modify anything, you gotta be super-user! */ | |
241 | if (txc->modes && !capable(CAP_SYS_TIME)) | |
242 | return -EPERM; | |
243 | ||
244 | /* Now we validate the data before disabling interrupts */ | |
245 | ||
246 | if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) | |
247 | /* singleshot must not be used with any other mode bits */ | |
248 | if (txc->modes != ADJ_OFFSET_SINGLESHOT) | |
249 | return -EINVAL; | |
250 | ||
251 | if (txc->modes != ADJ_OFFSET_SINGLESHOT && (txc->modes & ADJ_OFFSET)) | |
252 | /* adjustment Offset limited to +- .512 seconds */ | |
253 | if (txc->offset <= - MAXPHASE || txc->offset >= MAXPHASE ) | |
254 | return -EINVAL; | |
255 | ||
256 | /* if the quartz is off by more than 10% something is VERY wrong ! */ | |
257 | if (txc->modes & ADJ_TICK) | |
258 | if (txc->tick < 900000/USER_HZ || | |
259 | txc->tick > 1100000/USER_HZ) | |
260 | return -EINVAL; | |
261 | ||
262 | write_seqlock_irq(&xtime_lock); | |
263 | result = time_state; /* mostly `TIME_OK' */ | |
264 | ||
265 | /* Save for later - semantics of adjtime is to return old value */ | |
266 | save_adjust = time_next_adjust ? time_next_adjust : time_adjust; | |
267 | ||
268 | #if 0 /* STA_CLOCKERR is never set yet */ | |
269 | time_status &= ~STA_CLOCKERR; /* reset STA_CLOCKERR */ | |
270 | #endif | |
271 | /* If there are input parameters, then process them */ | |
272 | if (txc->modes) | |
273 | { | |
274 | if (txc->modes & ADJ_STATUS) /* only set allowed bits */ | |
275 | time_status = (txc->status & ~STA_RONLY) | | |
276 | (time_status & STA_RONLY); | |
277 | ||
278 | if (txc->modes & ADJ_FREQUENCY) { /* p. 22 */ | |
279 | if (txc->freq > MAXFREQ || txc->freq < -MAXFREQ) { | |
280 | result = -EINVAL; | |
281 | goto leave; | |
282 | } | |
283 | time_freq = txc->freq; | |
284 | } | |
285 | ||
286 | if (txc->modes & ADJ_MAXERROR) { | |
287 | if (txc->maxerror < 0 || txc->maxerror >= NTP_PHASE_LIMIT) { | |
288 | result = -EINVAL; | |
289 | goto leave; | |
290 | } | |
291 | time_maxerror = txc->maxerror; | |
292 | } | |
293 | ||
294 | if (txc->modes & ADJ_ESTERROR) { | |
295 | if (txc->esterror < 0 || txc->esterror >= NTP_PHASE_LIMIT) { | |
296 | result = -EINVAL; | |
297 | goto leave; | |
298 | } | |
299 | time_esterror = txc->esterror; | |
300 | } | |
301 | ||
302 | if (txc->modes & ADJ_TIMECONST) { /* p. 24 */ | |
303 | if (txc->constant < 0) { /* NTP v4 uses values > 6 */ | |
304 | result = -EINVAL; | |
305 | goto leave; | |
306 | } | |
307 | time_constant = txc->constant; | |
308 | } | |
309 | ||
310 | if (txc->modes & ADJ_OFFSET) { /* values checked earlier */ | |
311 | if (txc->modes == ADJ_OFFSET_SINGLESHOT) { | |
312 | /* adjtime() is independent from ntp_adjtime() */ | |
313 | if ((time_next_adjust = txc->offset) == 0) | |
314 | time_adjust = 0; | |
315 | } | |
316 | else if (time_status & STA_PLL) { | |
317 | ltemp = txc->offset; | |
318 | ||
319 | /* | |
320 | * Scale the phase adjustment and | |
321 | * clamp to the operating range. | |
322 | */ | |
3d3675cc RZ |
323 | time_offset = min(ltemp, MAXPHASE); |
324 | time_offset = max(time_offset, -MAXPHASE); | |
4c7ee8de JS |
325 | |
326 | /* | |
327 | * Select whether the frequency is to be controlled | |
328 | * and in which mode (PLL or FLL). Clamp to the operating | |
329 | * range. Ugly multiply/divide should be replaced someday. | |
330 | */ | |
331 | ||
332 | if (time_status & STA_FREQHOLD || time_reftime == 0) | |
333 | time_reftime = xtime.tv_sec; | |
334 | mtemp = xtime.tv_sec - time_reftime; | |
335 | time_reftime = xtime.tv_sec; | |
336 | if (time_status & STA_FLL) { | |
337 | if (mtemp >= MINSEC) { | |
3d3675cc | 338 | ltemp = ((time_offset << 12) / mtemp) << (SHIFT_USEC - 12); |
4c7ee8de JS |
339 | time_freq += shift_right(ltemp, SHIFT_KH); |
340 | } else /* calibration interval too short (p. 12) */ | |
341 | result = TIME_ERROR; | |
342 | } else { /* PLL mode */ | |
343 | if (mtemp < MAXSEC) { | |
344 | ltemp *= mtemp; | |
345 | time_freq += shift_right(ltemp,(time_constant + | |
346 | time_constant + | |
347 | SHIFT_KF - SHIFT_USEC)); | |
348 | } else /* calibration interval too long (p. 12) */ | |
349 | result = TIME_ERROR; | |
350 | } | |
351 | time_freq = min(time_freq, time_tolerance); | |
352 | time_freq = max(time_freq, -time_tolerance); | |
3d3675cc | 353 | time_offset = (time_offset * NSEC_PER_USEC / HZ) << SHIFT_UPDATE; |
4c7ee8de JS |
354 | } /* STA_PLL */ |
355 | } /* txc->modes & ADJ_OFFSET */ | |
b0ee7556 | 356 | if (txc->modes & ADJ_TICK) |
4c7ee8de | 357 | tick_usec = txc->tick; |
b0ee7556 | 358 | |
dc6a43e4 | 359 | if (txc->modes & (ADJ_TICK|ADJ_FREQUENCY|ADJ_OFFSET)) |
b0ee7556 | 360 | ntp_update_frequency(); |
4c7ee8de JS |
361 | } /* txc->modes */ |
362 | leave: if ((time_status & (STA_UNSYNC|STA_CLOCKERR)) != 0) | |
363 | result = TIME_ERROR; | |
364 | ||
365 | if ((txc->modes & ADJ_OFFSET_SINGLESHOT) == ADJ_OFFSET_SINGLESHOT) | |
366 | txc->offset = save_adjust; | |
3d3675cc RZ |
367 | else |
368 | txc->offset = shift_right(time_offset, SHIFT_UPDATE) * HZ / 1000; | |
4c7ee8de JS |
369 | txc->freq = time_freq; |
370 | txc->maxerror = time_maxerror; | |
371 | txc->esterror = time_esterror; | |
372 | txc->status = time_status; | |
373 | txc->constant = time_constant; | |
374 | txc->precision = time_precision; | |
375 | txc->tolerance = time_tolerance; | |
376 | txc->tick = tick_usec; | |
377 | ||
378 | /* PPS is not implemented, so these are zero */ | |
379 | txc->ppsfreq = 0; | |
380 | txc->jitter = 0; | |
381 | txc->shift = 0; | |
382 | txc->stabil = 0; | |
383 | txc->jitcnt = 0; | |
384 | txc->calcnt = 0; | |
385 | txc->errcnt = 0; | |
386 | txc->stbcnt = 0; | |
387 | write_sequnlock_irq(&xtime_lock); | |
388 | do_gettimeofday(&txc->time); | |
389 | notify_arch_cmos_timer(); | |
390 | return(result); | |
391 | } |