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8524070b JS |
1 | /* |
2 | * linux/kernel/time/timekeeping.c | |
3 | * | |
4 | * Kernel timekeeping code and accessor functions | |
5 | * | |
6 | * This code was moved from linux/kernel/timer.c. | |
7 | * Please see that file for copyright and history logs. | |
8 | * | |
9 | */ | |
10 | ||
11 | #include <linux/module.h> | |
12 | #include <linux/interrupt.h> | |
13 | #include <linux/percpu.h> | |
14 | #include <linux/init.h> | |
15 | #include <linux/mm.h> | |
16 | #include <linux/sysdev.h> | |
17 | #include <linux/clocksource.h> | |
18 | #include <linux/jiffies.h> | |
19 | #include <linux/time.h> | |
20 | #include <linux/tick.h> | |
21 | ||
22 | ||
23 | /* | |
24 | * This read-write spinlock protects us from races in SMP while | |
25 | * playing with xtime and avenrun. | |
26 | */ | |
27 | __attribute__((weak)) __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock); | |
28 | ||
29 | EXPORT_SYMBOL(xtime_lock); | |
30 | ||
31 | ||
32 | /* | |
33 | * The current time | |
34 | * wall_to_monotonic is what we need to add to xtime (or xtime corrected | |
35 | * for sub jiffie times) to get to monotonic time. Monotonic is pegged | |
36 | * at zero at system boot time, so wall_to_monotonic will be negative, | |
37 | * however, we will ALWAYS keep the tv_nsec part positive so we can use | |
38 | * the usual normalization. | |
39 | */ | |
40 | struct timespec xtime __attribute__ ((aligned (16))); | |
41 | struct timespec wall_to_monotonic __attribute__ ((aligned (16))); | |
42 | ||
43 | EXPORT_SYMBOL(xtime); | |
44 | ||
45 | ||
46 | static struct clocksource *clock; /* pointer to current clocksource */ | |
47 | ||
48 | ||
49 | #ifdef CONFIG_GENERIC_TIME | |
50 | /** | |
51 | * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook | |
52 | * | |
53 | * private function, must hold xtime_lock lock when being | |
54 | * called. Returns the number of nanoseconds since the | |
55 | * last call to update_wall_time() (adjusted by NTP scaling) | |
56 | */ | |
57 | static inline s64 __get_nsec_offset(void) | |
58 | { | |
59 | cycle_t cycle_now, cycle_delta; | |
60 | s64 ns_offset; | |
61 | ||
62 | /* read clocksource: */ | |
63 | cycle_now = clocksource_read(clock); | |
64 | ||
65 | /* calculate the delta since the last update_wall_time: */ | |
66 | cycle_delta = (cycle_now - clock->cycle_last) & clock->mask; | |
67 | ||
68 | /* convert to nanoseconds: */ | |
69 | ns_offset = cyc2ns(clock, cycle_delta); | |
70 | ||
71 | return ns_offset; | |
72 | } | |
73 | ||
74 | /** | |
75 | * __get_realtime_clock_ts - Returns the time of day in a timespec | |
76 | * @ts: pointer to the timespec to be set | |
77 | * | |
78 | * Returns the time of day in a timespec. Used by | |
79 | * do_gettimeofday() and get_realtime_clock_ts(). | |
80 | */ | |
81 | static inline void __get_realtime_clock_ts(struct timespec *ts) | |
82 | { | |
83 | unsigned long seq; | |
84 | s64 nsecs; | |
85 | ||
86 | do { | |
87 | seq = read_seqbegin(&xtime_lock); | |
88 | ||
89 | *ts = xtime; | |
90 | nsecs = __get_nsec_offset(); | |
91 | ||
92 | } while (read_seqretry(&xtime_lock, seq)); | |
93 | ||
94 | timespec_add_ns(ts, nsecs); | |
95 | } | |
96 | ||
97 | /** | |
98 | * getnstimeofday - Returns the time of day in a timespec | |
99 | * @ts: pointer to the timespec to be set | |
100 | * | |
101 | * Returns the time of day in a timespec. | |
102 | */ | |
103 | void getnstimeofday(struct timespec *ts) | |
104 | { | |
105 | __get_realtime_clock_ts(ts); | |
106 | } | |
107 | ||
108 | EXPORT_SYMBOL(getnstimeofday); | |
109 | ||
110 | /** | |
111 | * do_gettimeofday - Returns the time of day in a timeval | |
112 | * @tv: pointer to the timeval to be set | |
113 | * | |
114 | * NOTE: Users should be converted to using get_realtime_clock_ts() | |
115 | */ | |
116 | void do_gettimeofday(struct timeval *tv) | |
117 | { | |
118 | struct timespec now; | |
119 | ||
120 | __get_realtime_clock_ts(&now); | |
121 | tv->tv_sec = now.tv_sec; | |
122 | tv->tv_usec = now.tv_nsec/1000; | |
123 | } | |
124 | ||
125 | EXPORT_SYMBOL(do_gettimeofday); | |
126 | /** | |
127 | * do_settimeofday - Sets the time of day | |
128 | * @tv: pointer to the timespec variable containing the new time | |
129 | * | |
130 | * Sets the time of day to the new time and update NTP and notify hrtimers | |
131 | */ | |
132 | int do_settimeofday(struct timespec *tv) | |
133 | { | |
134 | unsigned long flags; | |
135 | time_t wtm_sec, sec = tv->tv_sec; | |
136 | long wtm_nsec, nsec = tv->tv_nsec; | |
137 | ||
138 | if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC) | |
139 | return -EINVAL; | |
140 | ||
141 | write_seqlock_irqsave(&xtime_lock, flags); | |
142 | ||
143 | nsec -= __get_nsec_offset(); | |
144 | ||
145 | wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec); | |
146 | wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec); | |
147 | ||
148 | set_normalized_timespec(&xtime, sec, nsec); | |
149 | set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec); | |
150 | ||
151 | clock->error = 0; | |
152 | ntp_clear(); | |
153 | ||
154 | update_vsyscall(&xtime, clock); | |
155 | ||
156 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
157 | ||
158 | /* signal hrtimers about time change */ | |
159 | clock_was_set(); | |
160 | ||
161 | return 0; | |
162 | } | |
163 | ||
164 | EXPORT_SYMBOL(do_settimeofday); | |
165 | ||
166 | /** | |
167 | * change_clocksource - Swaps clocksources if a new one is available | |
168 | * | |
169 | * Accumulates current time interval and initializes new clocksource | |
170 | */ | |
171 | static void change_clocksource(void) | |
172 | { | |
173 | struct clocksource *new; | |
174 | cycle_t now; | |
175 | u64 nsec; | |
176 | ||
177 | new = clocksource_get_next(); | |
178 | ||
179 | if (clock == new) | |
180 | return; | |
181 | ||
182 | now = clocksource_read(new); | |
183 | nsec = __get_nsec_offset(); | |
184 | timespec_add_ns(&xtime, nsec); | |
185 | ||
186 | clock = new; | |
187 | clock->cycle_last = now; | |
188 | ||
189 | clock->error = 0; | |
190 | clock->xtime_nsec = 0; | |
191 | clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); | |
192 | ||
193 | tick_clock_notify(); | |
194 | ||
195 | printk(KERN_INFO "Time: %s clocksource has been installed.\n", | |
196 | clock->name); | |
197 | } | |
198 | #else | |
199 | static inline void change_clocksource(void) { } | |
200 | #endif | |
201 | ||
202 | /** | |
203 | * timekeeping_is_continuous - check to see if timekeeping is free running | |
204 | */ | |
205 | int timekeeping_is_continuous(void) | |
206 | { | |
207 | unsigned long seq; | |
208 | int ret; | |
209 | ||
210 | do { | |
211 | seq = read_seqbegin(&xtime_lock); | |
212 | ||
213 | ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES; | |
214 | ||
215 | } while (read_seqretry(&xtime_lock, seq)); | |
216 | ||
217 | return ret; | |
218 | } | |
219 | ||
220 | /** | |
221 | * read_persistent_clock - Return time in seconds from the persistent clock. | |
222 | * | |
223 | * Weak dummy function for arches that do not yet support it. | |
224 | * Returns seconds from epoch using the battery backed persistent clock. | |
225 | * Returns zero if unsupported. | |
226 | * | |
227 | * XXX - Do be sure to remove it once all arches implement it. | |
228 | */ | |
229 | unsigned long __attribute__((weak)) read_persistent_clock(void) | |
230 | { | |
231 | return 0; | |
232 | } | |
233 | ||
234 | /* | |
235 | * timekeeping_init - Initializes the clocksource and common timekeeping values | |
236 | */ | |
237 | void __init timekeeping_init(void) | |
238 | { | |
239 | unsigned long flags; | |
240 | unsigned long sec = read_persistent_clock(); | |
241 | ||
242 | write_seqlock_irqsave(&xtime_lock, flags); | |
243 | ||
244 | ntp_clear(); | |
245 | ||
246 | clock = clocksource_get_next(); | |
247 | clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH); | |
248 | clock->cycle_last = clocksource_read(clock); | |
249 | ||
250 | xtime.tv_sec = sec; | |
251 | xtime.tv_nsec = 0; | |
252 | set_normalized_timespec(&wall_to_monotonic, | |
253 | -xtime.tv_sec, -xtime.tv_nsec); | |
254 | ||
255 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
256 | } | |
257 | ||
258 | /* flag for if timekeeping is suspended */ | |
259 | static int timekeeping_suspended; | |
260 | /* time in seconds when suspend began */ | |
261 | static unsigned long timekeeping_suspend_time; | |
262 | ||
263 | /** | |
264 | * timekeeping_resume - Resumes the generic timekeeping subsystem. | |
265 | * @dev: unused | |
266 | * | |
267 | * This is for the generic clocksource timekeeping. | |
268 | * xtime/wall_to_monotonic/jiffies/etc are | |
269 | * still managed by arch specific suspend/resume code. | |
270 | */ | |
271 | static int timekeeping_resume(struct sys_device *dev) | |
272 | { | |
273 | unsigned long flags; | |
274 | unsigned long now = read_persistent_clock(); | |
275 | ||
276 | write_seqlock_irqsave(&xtime_lock, flags); | |
277 | ||
278 | if (now && (now > timekeeping_suspend_time)) { | |
279 | unsigned long sleep_length = now - timekeeping_suspend_time; | |
280 | ||
281 | xtime.tv_sec += sleep_length; | |
282 | wall_to_monotonic.tv_sec -= sleep_length; | |
283 | } | |
284 | /* re-base the last cycle value */ | |
285 | clock->cycle_last = clocksource_read(clock); | |
286 | clock->error = 0; | |
287 | timekeeping_suspended = 0; | |
288 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
289 | ||
290 | touch_softlockup_watchdog(); | |
291 | ||
292 | clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL); | |
293 | ||
294 | /* Resume hrtimers */ | |
295 | hres_timers_resume(); | |
296 | ||
297 | return 0; | |
298 | } | |
299 | ||
300 | static int timekeeping_suspend(struct sys_device *dev, pm_message_t state) | |
301 | { | |
302 | unsigned long flags; | |
303 | ||
304 | write_seqlock_irqsave(&xtime_lock, flags); | |
305 | timekeeping_suspended = 1; | |
306 | timekeeping_suspend_time = read_persistent_clock(); | |
307 | write_sequnlock_irqrestore(&xtime_lock, flags); | |
308 | ||
309 | clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL); | |
310 | ||
311 | return 0; | |
312 | } | |
313 | ||
314 | /* sysfs resume/suspend bits for timekeeping */ | |
315 | static struct sysdev_class timekeeping_sysclass = { | |
316 | .resume = timekeeping_resume, | |
317 | .suspend = timekeeping_suspend, | |
318 | set_kset_name("timekeeping"), | |
319 | }; | |
320 | ||
321 | static struct sys_device device_timer = { | |
322 | .id = 0, | |
323 | .cls = &timekeeping_sysclass, | |
324 | }; | |
325 | ||
326 | static int __init timekeeping_init_device(void) | |
327 | { | |
328 | int error = sysdev_class_register(&timekeeping_sysclass); | |
329 | if (!error) | |
330 | error = sysdev_register(&device_timer); | |
331 | return error; | |
332 | } | |
333 | ||
334 | device_initcall(timekeeping_init_device); | |
335 | ||
336 | /* | |
337 | * If the error is already larger, we look ahead even further | |
338 | * to compensate for late or lost adjustments. | |
339 | */ | |
340 | static __always_inline int clocksource_bigadjust(s64 error, s64 *interval, | |
341 | s64 *offset) | |
342 | { | |
343 | s64 tick_error, i; | |
344 | u32 look_ahead, adj; | |
345 | s32 error2, mult; | |
346 | ||
347 | /* | |
348 | * Use the current error value to determine how much to look ahead. | |
349 | * The larger the error the slower we adjust for it to avoid problems | |
350 | * with losing too many ticks, otherwise we would overadjust and | |
351 | * produce an even larger error. The smaller the adjustment the | |
352 | * faster we try to adjust for it, as lost ticks can do less harm | |
353 | * here. This is tuned so that an error of about 1 msec is adusted | |
354 | * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks). | |
355 | */ | |
356 | error2 = clock->error >> (TICK_LENGTH_SHIFT + 22 - 2 * SHIFT_HZ); | |
357 | error2 = abs(error2); | |
358 | for (look_ahead = 0; error2 > 0; look_ahead++) | |
359 | error2 >>= 2; | |
360 | ||
361 | /* | |
362 | * Now calculate the error in (1 << look_ahead) ticks, but first | |
363 | * remove the single look ahead already included in the error. | |
364 | */ | |
365 | tick_error = current_tick_length() >> | |
366 | (TICK_LENGTH_SHIFT - clock->shift + 1); | |
367 | tick_error -= clock->xtime_interval >> 1; | |
368 | error = ((error - tick_error) >> look_ahead) + tick_error; | |
369 | ||
370 | /* Finally calculate the adjustment shift value. */ | |
371 | i = *interval; | |
372 | mult = 1; | |
373 | if (error < 0) { | |
374 | error = -error; | |
375 | *interval = -*interval; | |
376 | *offset = -*offset; | |
377 | mult = -1; | |
378 | } | |
379 | for (adj = 0; error > i; adj++) | |
380 | error >>= 1; | |
381 | ||
382 | *interval <<= adj; | |
383 | *offset <<= adj; | |
384 | return mult << adj; | |
385 | } | |
386 | ||
387 | /* | |
388 | * Adjust the multiplier to reduce the error value, | |
389 | * this is optimized for the most common adjustments of -1,0,1, | |
390 | * for other values we can do a bit more work. | |
391 | */ | |
392 | static void clocksource_adjust(struct clocksource *clock, s64 offset) | |
393 | { | |
394 | s64 error, interval = clock->cycle_interval; | |
395 | int adj; | |
396 | ||
397 | error = clock->error >> (TICK_LENGTH_SHIFT - clock->shift - 1); | |
398 | if (error > interval) { | |
399 | error >>= 2; | |
400 | if (likely(error <= interval)) | |
401 | adj = 1; | |
402 | else | |
403 | adj = clocksource_bigadjust(error, &interval, &offset); | |
404 | } else if (error < -interval) { | |
405 | error >>= 2; | |
406 | if (likely(error >= -interval)) { | |
407 | adj = -1; | |
408 | interval = -interval; | |
409 | offset = -offset; | |
410 | } else | |
411 | adj = clocksource_bigadjust(error, &interval, &offset); | |
412 | } else | |
413 | return; | |
414 | ||
415 | clock->mult += adj; | |
416 | clock->xtime_interval += interval; | |
417 | clock->xtime_nsec -= offset; | |
418 | clock->error -= (interval - offset) << | |
419 | (TICK_LENGTH_SHIFT - clock->shift); | |
420 | } | |
421 | ||
422 | /** | |
423 | * update_wall_time - Uses the current clocksource to increment the wall time | |
424 | * | |
425 | * Called from the timer interrupt, must hold a write on xtime_lock. | |
426 | */ | |
427 | void update_wall_time(void) | |
428 | { | |
429 | cycle_t offset; | |
430 | ||
431 | /* Make sure we're fully resumed: */ | |
432 | if (unlikely(timekeeping_suspended)) | |
433 | return; | |
434 | ||
435 | #ifdef CONFIG_GENERIC_TIME | |
436 | offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask; | |
437 | #else | |
438 | offset = clock->cycle_interval; | |
439 | #endif | |
440 | clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift; | |
441 | ||
442 | /* normally this loop will run just once, however in the | |
443 | * case of lost or late ticks, it will accumulate correctly. | |
444 | */ | |
445 | while (offset >= clock->cycle_interval) { | |
446 | /* accumulate one interval */ | |
447 | clock->xtime_nsec += clock->xtime_interval; | |
448 | clock->cycle_last += clock->cycle_interval; | |
449 | offset -= clock->cycle_interval; | |
450 | ||
451 | if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) { | |
452 | clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift; | |
453 | xtime.tv_sec++; | |
454 | second_overflow(); | |
455 | } | |
456 | ||
457 | /* interpolator bits */ | |
458 | time_interpolator_update(clock->xtime_interval | |
459 | >> clock->shift); | |
460 | ||
461 | /* accumulate error between NTP and clock interval */ | |
462 | clock->error += current_tick_length(); | |
463 | clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift); | |
464 | } | |
465 | ||
466 | /* correct the clock when NTP error is too big */ | |
467 | clocksource_adjust(clock, offset); | |
468 | ||
469 | /* store full nanoseconds into xtime */ | |
470 | xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift; | |
471 | clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift; | |
472 | ||
473 | /* check to see if there is a new clocksource to use */ | |
474 | change_clocksource(); | |
475 | update_vsyscall(&xtime, clock); | |
476 | } |