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1 | /* |
2 | * linux/kernel/time/clocksource.c |
3 | * |
4 | * This file contains the functions which manage clocksource drivers. |
5 | * |
6 | * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com) |
7 | * |
8 | * This program is free software; you can redistribute it and/or modify |
9 | * it under the terms of the GNU General Public License as published by |
10 | * the Free Software Foundation; either version 2 of the License, or |
11 | * (at your option) any later version. |
12 | * |
13 | * This program is distributed in the hope that it will be useful, |
14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
16 | * GNU General Public License for more details. |
17 | * |
18 | * You should have received a copy of the GNU General Public License |
19 | * along with this program; if not, write to the Free Software |
20 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. |
21 | * |
22 | * TODO WishList: |
23 | * o Allow clocksource drivers to be unregistered |
24 | */ |
25 | |
26 | #include <linux/clocksource.h> |
27 | #include <linux/sysdev.h> |
28 | #include <linux/init.h> |
29 | #include <linux/module.h> |
30 | #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ |
31 | #include <linux/tick.h> |
32 | #include <linux/kthread.h> |
33 | |
34 | void timecounter_init(struct timecounter *tc, |
35 | const struct cyclecounter *cc, |
36 | u64 start_tstamp) |
37 | { |
38 | tc->cc = cc; |
39 | tc->cycle_last = cc->read(cc); |
40 | tc->nsec = start_tstamp; |
41 | } |
42 | EXPORT_SYMBOL_GPL(timecounter_init); |
43 | |
44 | /** |
45 | * timecounter_read_delta - get nanoseconds since last call of this function |
46 | * @tc: Pointer to time counter |
47 | * |
48 | * When the underlying cycle counter runs over, this will be handled |
49 | * correctly as long as it does not run over more than once between |
50 | * calls. |
51 | * |
52 | * The first call to this function for a new time counter initializes |
53 | * the time tracking and returns an undefined result. |
54 | */ |
55 | static u64 timecounter_read_delta(struct timecounter *tc) |
56 | { |
57 | cycle_t cycle_now, cycle_delta; |
58 | u64 ns_offset; |
59 | |
60 | /* read cycle counter: */ |
61 | cycle_now = tc->cc->read(tc->cc); |
62 | |
63 | /* calculate the delta since the last timecounter_read_delta(): */ |
64 | cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask; |
65 | |
66 | /* convert to nanoseconds: */ |
67 | ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta); |
68 | |
69 | /* update time stamp of timecounter_read_delta() call: */ |
70 | tc->cycle_last = cycle_now; |
71 | |
72 | return ns_offset; |
73 | } |
74 | |
75 | u64 timecounter_read(struct timecounter *tc) |
76 | { |
77 | u64 nsec; |
78 | |
79 | /* increment time by nanoseconds since last call */ |
80 | nsec = timecounter_read_delta(tc); |
81 | nsec += tc->nsec; |
82 | tc->nsec = nsec; |
83 | |
84 | return nsec; |
85 | } |
86 | EXPORT_SYMBOL_GPL(timecounter_read); |
87 | |
88 | u64 timecounter_cyc2time(struct timecounter *tc, |
89 | cycle_t cycle_tstamp) |
90 | { |
91 | u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask; |
92 | u64 nsec; |
93 | |
94 | /* |
95 | * Instead of always treating cycle_tstamp as more recent |
96 | * than tc->cycle_last, detect when it is too far in the |
97 | * future and treat it as old time stamp instead. |
98 | */ |
99 | if (cycle_delta > tc->cc->mask / 2) { |
100 | cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask; |
101 | nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta); |
102 | } else { |
103 | nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec; |
104 | } |
105 | |
106 | return nsec; |
107 | } |
108 | EXPORT_SYMBOL_GPL(timecounter_cyc2time); |
109 | |
110 | /** |
111 | * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks |
112 | * @mult: pointer to mult variable |
113 | * @shift: pointer to shift variable |
114 | * @from: frequency to convert from |
115 | * @to: frequency to convert to |
116 | * @minsec: guaranteed runtime conversion range in seconds |
117 | * |
118 | * The function evaluates the shift/mult pair for the scaled math |
119 | * operations of clocksources and clockevents. |
120 | * |
121 | * @to and @from are frequency values in HZ. For clock sources @to is |
122 | * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock |
123 | * event @to is the counter frequency and @from is NSEC_PER_SEC. |
124 | * |
125 | * The @minsec conversion range argument controls the time frame in |
126 | * seconds which must be covered by the runtime conversion with the |
127 | * calculated mult and shift factors. This guarantees that no 64bit |
128 | * overflow happens when the input value of the conversion is |
129 | * multiplied with the calculated mult factor. Larger ranges may |
130 | * reduce the conversion accuracy by chosing smaller mult and shift |
131 | * factors. |
132 | */ |
133 | void |
134 | clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 minsec) |
135 | { |
136 | u64 tmp; |
137 | u32 sft, sftacc= 32; |
138 | |
139 | /* |
140 | * Calculate the shift factor which is limiting the conversion |
141 | * range: |
142 | */ |
143 | tmp = ((u64)minsec * from) >> 32; |
144 | while (tmp) { |
145 | tmp >>=1; |
146 | sftacc--; |
147 | } |
148 | |
149 | /* |
150 | * Find the conversion shift/mult pair which has the best |
151 | * accuracy and fits the maxsec conversion range: |
152 | */ |
153 | for (sft = 32; sft > 0; sft--) { |
154 | tmp = (u64) to << sft; |
155 | do_div(tmp, from); |
156 | if ((tmp >> sftacc) == 0) |
157 | break; |
158 | } |
159 | *mult = tmp; |
160 | *shift = sft; |
161 | } |
162 | |
163 | /*[Clocksource internal variables]--------- |
164 | * curr_clocksource: |
165 | * currently selected clocksource. |
166 | * clocksource_list: |
167 | * linked list with the registered clocksources |
168 | * clocksource_mutex: |
169 | * protects manipulations to curr_clocksource and the clocksource_list |
170 | * override_name: |
171 | * Name of the user-specified clocksource. |
172 | */ |
173 | static struct clocksource *curr_clocksource; |
174 | static LIST_HEAD(clocksource_list); |
175 | static DEFINE_MUTEX(clocksource_mutex); |
176 | static char override_name[32]; |
177 | static int finished_booting; |
178 | |
179 | #ifdef CONFIG_CLOCKSOURCE_WATCHDOG |
180 | static void clocksource_watchdog_work(struct work_struct *work); |
181 | |
182 | static LIST_HEAD(watchdog_list); |
183 | static struct clocksource *watchdog; |
184 | static struct timer_list watchdog_timer; |
185 | static DECLARE_WORK(watchdog_work, clocksource_watchdog_work); |
186 | static DEFINE_SPINLOCK(watchdog_lock); |
187 | static cycle_t watchdog_last; |
188 | static int watchdog_running; |
189 | |
190 | static int clocksource_watchdog_kthread(void *data); |
191 | static void __clocksource_change_rating(struct clocksource *cs, int rating); |
192 | |
193 | /* |
194 | * Interval: 0.5sec Threshold: 0.0625s |
195 | */ |
196 | #define WATCHDOG_INTERVAL (HZ >> 1) |
197 | #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4) |
198 | |
199 | static void clocksource_watchdog_work(struct work_struct *work) |
200 | { |
201 | /* |
202 | * If kthread_run fails the next watchdog scan over the |
203 | * watchdog_list will find the unstable clock again. |
204 | */ |
205 | kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog"); |
206 | } |
207 | |
208 | static void __clocksource_unstable(struct clocksource *cs) |
209 | { |
210 | cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG); |
211 | cs->flags |= CLOCK_SOURCE_UNSTABLE; |
212 | if (finished_booting) |
213 | schedule_work(&watchdog_work); |
214 | } |
215 | |
216 | static void clocksource_unstable(struct clocksource *cs, int64_t delta) |
217 | { |
218 | printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n", |
219 | cs->name, delta); |
220 | __clocksource_unstable(cs); |
221 | } |
222 | |
223 | /** |
224 | * clocksource_mark_unstable - mark clocksource unstable via watchdog |
225 | * @cs: clocksource to be marked unstable |
226 | * |
227 | * This function is called instead of clocksource_change_rating from |
228 | * cpu hotplug code to avoid a deadlock between the clocksource mutex |
229 | * and the cpu hotplug mutex. It defers the update of the clocksource |
230 | * to the watchdog thread. |
231 | */ |
232 | void clocksource_mark_unstable(struct clocksource *cs) |
233 | { |
234 | unsigned long flags; |
235 | |
236 | spin_lock_irqsave(&watchdog_lock, flags); |
237 | if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) { |
238 | if (list_empty(&cs->wd_list)) |
239 | list_add(&cs->wd_list, &watchdog_list); |
240 | __clocksource_unstable(cs); |
241 | } |
242 | spin_unlock_irqrestore(&watchdog_lock, flags); |
243 | } |
244 | |
245 | static void clocksource_watchdog(unsigned long data) |
246 | { |
247 | struct clocksource *cs; |
248 | cycle_t csnow, wdnow; |
249 | int64_t wd_nsec, cs_nsec; |
250 | int next_cpu; |
251 | |
252 | spin_lock(&watchdog_lock); |
253 | if (!watchdog_running) |
254 | goto out; |
255 | |
256 | wdnow = watchdog->read(watchdog); |
257 | wd_nsec = clocksource_cyc2ns((wdnow - watchdog_last) & watchdog->mask, |
258 | watchdog->mult, watchdog->shift); |
259 | watchdog_last = wdnow; |
260 | |
261 | list_for_each_entry(cs, &watchdog_list, wd_list) { |
262 | |
263 | /* Clocksource already marked unstable? */ |
264 | if (cs->flags & CLOCK_SOURCE_UNSTABLE) { |
265 | if (finished_booting) |
266 | schedule_work(&watchdog_work); |
267 | continue; |
268 | } |
269 | |
270 | csnow = cs->read(cs); |
271 | |
272 | /* Clocksource initialized ? */ |
273 | if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) { |
274 | cs->flags |= CLOCK_SOURCE_WATCHDOG; |
275 | cs->wd_last = csnow; |
276 | continue; |
277 | } |
278 | |
279 | /* Check the deviation from the watchdog clocksource. */ |
280 | cs_nsec = clocksource_cyc2ns((csnow - cs->wd_last) & |
281 | cs->mask, cs->mult, cs->shift); |
282 | cs->wd_last = csnow; |
283 | if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) { |
284 | clocksource_unstable(cs, cs_nsec - wd_nsec); |
285 | continue; |
286 | } |
287 | |
288 | if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && |
289 | (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) && |
290 | (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) { |
291 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; |
292 | /* |
293 | * We just marked the clocksource as highres-capable, |
294 | * notify the rest of the system as well so that we |
295 | * transition into high-res mode: |
296 | */ |
297 | tick_clock_notify(); |
298 | } |
299 | } |
300 | |
301 | /* |
302 | * Cycle through CPUs to check if the CPUs stay synchronized |
303 | * to each other. |
304 | */ |
305 | next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask); |
306 | if (next_cpu >= nr_cpu_ids) |
307 | next_cpu = cpumask_first(cpu_online_mask); |
308 | watchdog_timer.expires += WATCHDOG_INTERVAL; |
309 | add_timer_on(&watchdog_timer, next_cpu); |
310 | out: |
311 | spin_unlock(&watchdog_lock); |
312 | } |
313 | |
314 | static inline void clocksource_start_watchdog(void) |
315 | { |
316 | if (watchdog_running || !watchdog || list_empty(&watchdog_list)) |
317 | return; |
318 | init_timer(&watchdog_timer); |
319 | watchdog_timer.function = clocksource_watchdog; |
320 | watchdog_last = watchdog->read(watchdog); |
321 | watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL; |
322 | add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask)); |
323 | watchdog_running = 1; |
324 | } |
325 | |
326 | static inline void clocksource_stop_watchdog(void) |
327 | { |
328 | if (!watchdog_running || (watchdog && !list_empty(&watchdog_list))) |
329 | return; |
330 | del_timer(&watchdog_timer); |
331 | watchdog_running = 0; |
332 | } |
333 | |
334 | static inline void clocksource_reset_watchdog(void) |
335 | { |
336 | struct clocksource *cs; |
337 | |
338 | list_for_each_entry(cs, &watchdog_list, wd_list) |
339 | cs->flags &= ~CLOCK_SOURCE_WATCHDOG; |
340 | } |
341 | |
342 | static void clocksource_resume_watchdog(void) |
343 | { |
344 | unsigned long flags; |
345 | |
346 | /* |
347 | * We use trylock here to avoid a potential dead lock when |
348 | * kgdb calls this code after the kernel has been stopped with |
349 | * watchdog_lock held. When watchdog_lock is held we just |
350 | * return and accept, that the watchdog might trigger and mark |
351 | * the monitored clock source (usually TSC) unstable. |
352 | * |
353 | * This does not affect the other caller clocksource_resume() |
354 | * because at this point the kernel is UP, interrupts are |
355 | * disabled and nothing can hold watchdog_lock. |
356 | */ |
357 | if (!spin_trylock_irqsave(&watchdog_lock, flags)) |
358 | return; |
359 | clocksource_reset_watchdog(); |
360 | spin_unlock_irqrestore(&watchdog_lock, flags); |
361 | } |
362 | |
363 | static void clocksource_enqueue_watchdog(struct clocksource *cs) |
364 | { |
365 | unsigned long flags; |
366 | |
367 | spin_lock_irqsave(&watchdog_lock, flags); |
368 | if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { |
369 | /* cs is a clocksource to be watched. */ |
370 | list_add(&cs->wd_list, &watchdog_list); |
371 | cs->flags &= ~CLOCK_SOURCE_WATCHDOG; |
372 | } else { |
373 | /* cs is a watchdog. */ |
374 | if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) |
375 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; |
376 | /* Pick the best watchdog. */ |
377 | if (!watchdog || cs->rating > watchdog->rating) { |
378 | watchdog = cs; |
379 | /* Reset watchdog cycles */ |
380 | clocksource_reset_watchdog(); |
381 | } |
382 | } |
383 | /* Check if the watchdog timer needs to be started. */ |
384 | clocksource_start_watchdog(); |
385 | spin_unlock_irqrestore(&watchdog_lock, flags); |
386 | } |
387 | |
388 | static void clocksource_dequeue_watchdog(struct clocksource *cs) |
389 | { |
390 | struct clocksource *tmp; |
391 | unsigned long flags; |
392 | |
393 | spin_lock_irqsave(&watchdog_lock, flags); |
394 | if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) { |
395 | /* cs is a watched clocksource. */ |
396 | list_del_init(&cs->wd_list); |
397 | } else if (cs == watchdog) { |
398 | /* Reset watchdog cycles */ |
399 | clocksource_reset_watchdog(); |
400 | /* Current watchdog is removed. Find an alternative. */ |
401 | watchdog = NULL; |
402 | list_for_each_entry(tmp, &clocksource_list, list) { |
403 | if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY) |
404 | continue; |
405 | if (!watchdog || tmp->rating > watchdog->rating) |
406 | watchdog = tmp; |
407 | } |
408 | } |
409 | cs->flags &= ~CLOCK_SOURCE_WATCHDOG; |
410 | /* Check if the watchdog timer needs to be stopped. */ |
411 | clocksource_stop_watchdog(); |
412 | spin_unlock_irqrestore(&watchdog_lock, flags); |
413 | } |
414 | |
415 | static int clocksource_watchdog_kthread(void *data) |
416 | { |
417 | struct clocksource *cs, *tmp; |
418 | unsigned long flags; |
419 | LIST_HEAD(unstable); |
420 | |
421 | mutex_lock(&clocksource_mutex); |
422 | spin_lock_irqsave(&watchdog_lock, flags); |
423 | list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) |
424 | if (cs->flags & CLOCK_SOURCE_UNSTABLE) { |
425 | list_del_init(&cs->wd_list); |
426 | list_add(&cs->wd_list, &unstable); |
427 | } |
428 | /* Check if the watchdog timer needs to be stopped. */ |
429 | clocksource_stop_watchdog(); |
430 | spin_unlock_irqrestore(&watchdog_lock, flags); |
431 | |
432 | /* Needs to be done outside of watchdog lock */ |
433 | list_for_each_entry_safe(cs, tmp, &unstable, wd_list) { |
434 | list_del_init(&cs->wd_list); |
435 | __clocksource_change_rating(cs, 0); |
436 | } |
437 | mutex_unlock(&clocksource_mutex); |
438 | return 0; |
439 | } |
440 | |
441 | #else /* CONFIG_CLOCKSOURCE_WATCHDOG */ |
442 | |
443 | static void clocksource_enqueue_watchdog(struct clocksource *cs) |
444 | { |
445 | if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) |
446 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; |
447 | } |
448 | |
449 | static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { } |
450 | static inline void clocksource_resume_watchdog(void) { } |
451 | static inline int clocksource_watchdog_kthread(void *data) { return 0; } |
452 | |
453 | #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */ |
454 | |
455 | /** |
456 | * clocksource_suspend - suspend the clocksource(s) |
457 | */ |
458 | void clocksource_suspend(void) |
459 | { |
460 | struct clocksource *cs; |
461 | |
462 | list_for_each_entry_reverse(cs, &clocksource_list, list) |
463 | if (cs->suspend) |
464 | cs->suspend(cs); |
465 | } |
466 | |
467 | /** |
468 | * clocksource_resume - resume the clocksource(s) |
469 | */ |
470 | void clocksource_resume(void) |
471 | { |
472 | struct clocksource *cs; |
473 | |
474 | list_for_each_entry(cs, &clocksource_list, list) |
475 | if (cs->resume) |
476 | cs->resume(cs); |
477 | |
478 | clocksource_resume_watchdog(); |
479 | } |
480 | |
481 | /** |
482 | * clocksource_touch_watchdog - Update watchdog |
483 | * |
484 | * Update the watchdog after exception contexts such as kgdb so as not |
485 | * to incorrectly trip the watchdog. This might fail when the kernel |
486 | * was stopped in code which holds watchdog_lock. |
487 | */ |
488 | void clocksource_touch_watchdog(void) |
489 | { |
490 | clocksource_resume_watchdog(); |
491 | } |
492 | |
493 | /** |
494 | * clocksource_max_deferment - Returns max time the clocksource can be deferred |
495 | * @cs: Pointer to clocksource |
496 | * |
497 | */ |
498 | static u64 clocksource_max_deferment(struct clocksource *cs) |
499 | { |
500 | u64 max_nsecs, max_cycles; |
501 | |
502 | /* |
503 | * Calculate the maximum number of cycles that we can pass to the |
504 | * cyc2ns function without overflowing a 64-bit signed result. The |
505 | * maximum number of cycles is equal to ULLONG_MAX/cs->mult which |
506 | * is equivalent to the below. |
507 | * max_cycles < (2^63)/cs->mult |
508 | * max_cycles < 2^(log2((2^63)/cs->mult)) |
509 | * max_cycles < 2^(log2(2^63) - log2(cs->mult)) |
510 | * max_cycles < 2^(63 - log2(cs->mult)) |
511 | * max_cycles < 1 << (63 - log2(cs->mult)) |
512 | * Please note that we add 1 to the result of the log2 to account for |
513 | * any rounding errors, ensure the above inequality is satisfied and |
514 | * no overflow will occur. |
515 | */ |
516 | max_cycles = 1ULL << (63 - (ilog2(cs->mult) + 1)); |
517 | |
518 | /* |
519 | * The actual maximum number of cycles we can defer the clocksource is |
520 | * determined by the minimum of max_cycles and cs->mask. |
521 | */ |
522 | max_cycles = min_t(u64, max_cycles, (u64) cs->mask); |
523 | max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult, cs->shift); |
524 | |
525 | /* |
526 | * To ensure that the clocksource does not wrap whilst we are idle, |
527 | * limit the time the clocksource can be deferred by 12.5%. Please |
528 | * note a margin of 12.5% is used because this can be computed with |
529 | * a shift, versus say 10% which would require division. |
530 | */ |
531 | return max_nsecs - (max_nsecs >> 5); |
532 | } |
533 | |
534 | #ifdef CONFIG_GENERIC_TIME |
535 | |
536 | /** |
537 | * clocksource_select - Select the best clocksource available |
538 | * |
539 | * Private function. Must hold clocksource_mutex when called. |
540 | * |
541 | * Select the clocksource with the best rating, or the clocksource, |
542 | * which is selected by userspace override. |
543 | */ |
544 | static void clocksource_select(void) |
545 | { |
546 | struct clocksource *best, *cs; |
547 | |
548 | if (!finished_booting || list_empty(&clocksource_list)) |
549 | return; |
550 | /* First clocksource on the list has the best rating. */ |
551 | best = list_first_entry(&clocksource_list, struct clocksource, list); |
552 | /* Check for the override clocksource. */ |
553 | list_for_each_entry(cs, &clocksource_list, list) { |
554 | if (strcmp(cs->name, override_name) != 0) |
555 | continue; |
556 | /* |
557 | * Check to make sure we don't switch to a non-highres |
558 | * capable clocksource if the tick code is in oneshot |
559 | * mode (highres or nohz) |
560 | */ |
561 | if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && |
562 | tick_oneshot_mode_active()) { |
563 | /* Override clocksource cannot be used. */ |
564 | printk(KERN_WARNING "Override clocksource %s is not " |
565 | "HRT compatible. Cannot switch while in " |
566 | "HRT/NOHZ mode\n", cs->name); |
567 | override_name[0] = 0; |
568 | } else |
569 | /* Override clocksource can be used. */ |
570 | best = cs; |
571 | break; |
572 | } |
573 | if (curr_clocksource != best) { |
574 | printk(KERN_INFO "Switching to clocksource %s\n", best->name); |
575 | curr_clocksource = best; |
576 | timekeeping_notify(curr_clocksource); |
577 | } |
578 | } |
579 | |
580 | #else /* CONFIG_GENERIC_TIME */ |
581 | |
582 | static inline void clocksource_select(void) { } |
583 | |
584 | #endif |
585 | |
586 | /* |
587 | * clocksource_done_booting - Called near the end of core bootup |
588 | * |
589 | * Hack to avoid lots of clocksource churn at boot time. |
590 | * We use fs_initcall because we want this to start before |
591 | * device_initcall but after subsys_initcall. |
592 | */ |
593 | static int __init clocksource_done_booting(void) |
594 | { |
595 | mutex_lock(&clocksource_mutex); |
596 | curr_clocksource = clocksource_default_clock(); |
597 | mutex_unlock(&clocksource_mutex); |
598 | |
599 | finished_booting = 1; |
600 | |
601 | /* |
602 | * Run the watchdog first to eliminate unstable clock sources |
603 | */ |
604 | clocksource_watchdog_kthread(NULL); |
605 | |
606 | mutex_lock(&clocksource_mutex); |
607 | clocksource_select(); |
608 | mutex_unlock(&clocksource_mutex); |
609 | return 0; |
610 | } |
611 | fs_initcall(clocksource_done_booting); |
612 | |
613 | /* |
614 | * Enqueue the clocksource sorted by rating |
615 | */ |
616 | static void clocksource_enqueue(struct clocksource *cs) |
617 | { |
618 | struct list_head *entry = &clocksource_list; |
619 | struct clocksource *tmp; |
620 | |
621 | list_for_each_entry(tmp, &clocksource_list, list) |
622 | /* Keep track of the place, where to insert */ |
623 | if (tmp->rating >= cs->rating) |
624 | entry = &tmp->list; |
625 | list_add(&cs->list, entry); |
626 | } |
627 | |
628 | /** |
629 | * clocksource_register - Used to install new clocksources |
630 | * @t: clocksource to be registered |
631 | * |
632 | * Returns -EBUSY if registration fails, zero otherwise. |
633 | */ |
634 | int clocksource_register(struct clocksource *cs) |
635 | { |
636 | /* calculate max idle time permitted for this clocksource */ |
637 | cs->max_idle_ns = clocksource_max_deferment(cs); |
638 | |
639 | mutex_lock(&clocksource_mutex); |
640 | clocksource_enqueue(cs); |
641 | clocksource_select(); |
642 | clocksource_enqueue_watchdog(cs); |
643 | mutex_unlock(&clocksource_mutex); |
644 | return 0; |
645 | } |
646 | EXPORT_SYMBOL(clocksource_register); |
647 | |
648 | static void __clocksource_change_rating(struct clocksource *cs, int rating) |
649 | { |
650 | list_del(&cs->list); |
651 | cs->rating = rating; |
652 | clocksource_enqueue(cs); |
653 | clocksource_select(); |
654 | } |
655 | |
656 | /** |
657 | * clocksource_change_rating - Change the rating of a registered clocksource |
658 | */ |
659 | void clocksource_change_rating(struct clocksource *cs, int rating) |
660 | { |
661 | mutex_lock(&clocksource_mutex); |
662 | __clocksource_change_rating(cs, rating); |
663 | mutex_unlock(&clocksource_mutex); |
664 | } |
665 | EXPORT_SYMBOL(clocksource_change_rating); |
666 | |
667 | /** |
668 | * clocksource_unregister - remove a registered clocksource |
669 | */ |
670 | void clocksource_unregister(struct clocksource *cs) |
671 | { |
672 | mutex_lock(&clocksource_mutex); |
673 | clocksource_dequeue_watchdog(cs); |
674 | list_del(&cs->list); |
675 | clocksource_select(); |
676 | mutex_unlock(&clocksource_mutex); |
677 | } |
678 | EXPORT_SYMBOL(clocksource_unregister); |
679 | |
680 | #ifdef CONFIG_SYSFS |
681 | /** |
682 | * sysfs_show_current_clocksources - sysfs interface for current clocksource |
683 | * @dev: unused |
684 | * @buf: char buffer to be filled with clocksource list |
685 | * |
686 | * Provides sysfs interface for listing current clocksource. |
687 | */ |
688 | static ssize_t |
689 | sysfs_show_current_clocksources(struct sys_device *dev, |
690 | struct sysdev_attribute *attr, char *buf) |
691 | { |
692 | ssize_t count = 0; |
693 | |
694 | mutex_lock(&clocksource_mutex); |
695 | count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name); |
696 | mutex_unlock(&clocksource_mutex); |
697 | |
698 | return count; |
699 | } |
700 | |
701 | /** |
702 | * sysfs_override_clocksource - interface for manually overriding clocksource |
703 | * @dev: unused |
704 | * @buf: name of override clocksource |
705 | * @count: length of buffer |
706 | * |
707 | * Takes input from sysfs interface for manually overriding the default |
708 | * clocksource selection. |
709 | */ |
710 | static ssize_t sysfs_override_clocksource(struct sys_device *dev, |
711 | struct sysdev_attribute *attr, |
712 | const char *buf, size_t count) |
713 | { |
714 | size_t ret = count; |
715 | |
716 | /* strings from sysfs write are not 0 terminated! */ |
717 | if (count >= sizeof(override_name)) |
718 | return -EINVAL; |
719 | |
720 | /* strip of \n: */ |
721 | if (buf[count-1] == '\n') |
722 | count--; |
723 | |
724 | mutex_lock(&clocksource_mutex); |
725 | |
726 | if (count > 0) |
727 | memcpy(override_name, buf, count); |
728 | override_name[count] = 0; |
729 | clocksource_select(); |
730 | |
731 | mutex_unlock(&clocksource_mutex); |
732 | |
733 | return ret; |
734 | } |
735 | |
736 | /** |
737 | * sysfs_show_available_clocksources - sysfs interface for listing clocksource |
738 | * @dev: unused |
739 | * @buf: char buffer to be filled with clocksource list |
740 | * |
741 | * Provides sysfs interface for listing registered clocksources |
742 | */ |
743 | static ssize_t |
744 | sysfs_show_available_clocksources(struct sys_device *dev, |
745 | struct sysdev_attribute *attr, |
746 | char *buf) |
747 | { |
748 | struct clocksource *src; |
749 | ssize_t count = 0; |
750 | |
751 | mutex_lock(&clocksource_mutex); |
752 | list_for_each_entry(src, &clocksource_list, list) { |
753 | /* |
754 | * Don't show non-HRES clocksource if the tick code is |
755 | * in one shot mode (highres=on or nohz=on) |
756 | */ |
757 | if (!tick_oneshot_mode_active() || |
758 | (src->flags & CLOCK_SOURCE_VALID_FOR_HRES)) |
759 | count += snprintf(buf + count, |
760 | max((ssize_t)PAGE_SIZE - count, (ssize_t)0), |
761 | "%s ", src->name); |
762 | } |
763 | mutex_unlock(&clocksource_mutex); |
764 | |
765 | count += snprintf(buf + count, |
766 | max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n"); |
767 | |
768 | return count; |
769 | } |
770 | |
771 | /* |
772 | * Sysfs setup bits: |
773 | */ |
774 | static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources, |
775 | sysfs_override_clocksource); |
776 | |
777 | static SYSDEV_ATTR(available_clocksource, 0444, |
778 | sysfs_show_available_clocksources, NULL); |
779 | |
780 | static struct sysdev_class clocksource_sysclass = { |
781 | .name = "clocksource", |
782 | }; |
783 | |
784 | static struct sys_device device_clocksource = { |
785 | .id = 0, |
786 | .cls = &clocksource_sysclass, |
787 | }; |
788 | |
789 | static int __init init_clocksource_sysfs(void) |
790 | { |
791 | int error = sysdev_class_register(&clocksource_sysclass); |
792 | |
793 | if (!error) |
794 | error = sysdev_register(&device_clocksource); |
795 | if (!error) |
796 | error = sysdev_create_file( |
797 | &device_clocksource, |
798 | &attr_current_clocksource); |
799 | if (!error) |
800 | error = sysdev_create_file( |
801 | &device_clocksource, |
802 | &attr_available_clocksource); |
803 | return error; |
804 | } |
805 | |
806 | device_initcall(init_clocksource_sysfs); |
807 | #endif /* CONFIG_SYSFS */ |
808 | |
809 | /** |
810 | * boot_override_clocksource - boot clock override |
811 | * @str: override name |
812 | * |
813 | * Takes a clocksource= boot argument and uses it |
814 | * as the clocksource override name. |
815 | */ |
816 | static int __init boot_override_clocksource(char* str) |
817 | { |
818 | mutex_lock(&clocksource_mutex); |
819 | if (str) |
820 | strlcpy(override_name, str, sizeof(override_name)); |
821 | mutex_unlock(&clocksource_mutex); |
822 | return 1; |
823 | } |
824 | |
825 | __setup("clocksource=", boot_override_clocksource); |
826 | |
827 | /** |
828 | * boot_override_clock - Compatibility layer for deprecated boot option |
829 | * @str: override name |
830 | * |
831 | * DEPRECATED! Takes a clock= boot argument and uses it |
832 | * as the clocksource override name |
833 | */ |
834 | static int __init boot_override_clock(char* str) |
835 | { |
836 | if (!strcmp(str, "pmtmr")) { |
837 | printk("Warning: clock=pmtmr is deprecated. " |
838 | "Use clocksource=acpi_pm.\n"); |
839 | return boot_override_clocksource("acpi_pm"); |
840 | } |
841 | printk("Warning! clock= boot option is deprecated. " |
842 | "Use clocksource=xyz\n"); |
843 | return boot_override_clocksource(str); |
844 | } |
845 | |
846 | __setup("clock=", boot_override_clock); |
847 |
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