projects/linux·blob v2.6.39 · refs

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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 ([email protected])
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
34void 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}
42EXPORT_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 */
55static 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
75u64 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}
86EXPORT_SYMBOL_GPL(timecounter_read);
87
88u64 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}
108EXPORT_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 * @maxsec: 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 @maxsec 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 */
133void
134clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
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)maxsec * 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 tmp += from / 2;
156 do_div(tmp, from);
157 if ((tmp >> sftacc) == 0)
158 break;
159 }
160 *mult = tmp;
161 *shift = sft;
162}
163
164/*[Clocksource internal variables]---------
165 * curr_clocksource:
166 * currently selected clocksource.
167 * clocksource_list:
168 * linked list with the registered clocksources
169 * clocksource_mutex:
170 * protects manipulations to curr_clocksource and the clocksource_list
171 * override_name:
172 * Name of the user-specified clocksource.
173 */
174static struct clocksource *curr_clocksource;
175static LIST_HEAD(clocksource_list);
176static DEFINE_MUTEX(clocksource_mutex);
177static char override_name[32];
178static int finished_booting;
179
180#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
181static void clocksource_watchdog_work(struct work_struct *work);
182
183static LIST_HEAD(watchdog_list);
184static struct clocksource *watchdog;
185static struct timer_list watchdog_timer;
186static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
187static DEFINE_SPINLOCK(watchdog_lock);
188static cycle_t watchdog_last;
189static int watchdog_running;
190
191static int clocksource_watchdog_kthread(void *data);
192static void __clocksource_change_rating(struct clocksource *cs, int rating);
193
194/*
195 * Interval: 0.5sec Threshold: 0.0625s
196 */
197#define WATCHDOG_INTERVAL (HZ >> 1)
198#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
199
200static void clocksource_watchdog_work(struct work_struct *work)
201{
202 /*
203 * If kthread_run fails the next watchdog scan over the
204 * watchdog_list will find the unstable clock again.
205 */
206 kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
207}
208
209static void __clocksource_unstable(struct clocksource *cs)
210{
211 cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
212 cs->flags |= CLOCK_SOURCE_UNSTABLE;
213 if (finished_booting)
214 schedule_work(&watchdog_work);
215}
216
217static void clocksource_unstable(struct clocksource *cs, int64_t delta)
218{
219 printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
220 cs->name, delta);
221 __clocksource_unstable(cs);
222}
223
224/**
225 * clocksource_mark_unstable - mark clocksource unstable via watchdog
226 * @cs: clocksource to be marked unstable
227 *
228 * This function is called instead of clocksource_change_rating from
229 * cpu hotplug code to avoid a deadlock between the clocksource mutex
230 * and the cpu hotplug mutex. It defers the update of the clocksource
231 * to the watchdog thread.
232 */
233void clocksource_mark_unstable(struct clocksource *cs)
234{
235 unsigned long flags;
236
237 spin_lock_irqsave(&watchdog_lock, flags);
238 if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
239 if (list_empty(&cs->wd_list))
240 list_add(&cs->wd_list, &watchdog_list);
241 __clocksource_unstable(cs);
242 }
243 spin_unlock_irqrestore(&watchdog_lock, flags);
244}
245
246static void clocksource_watchdog(unsigned long data)
247{
248 struct clocksource *cs;
249 cycle_t csnow, wdnow;
250 int64_t wd_nsec, cs_nsec;
251 int next_cpu;
252
253 spin_lock(&watchdog_lock);
254 if (!watchdog_running)
255 goto out;
256
257 wdnow = watchdog->read(watchdog);
258 wd_nsec = clocksource_cyc2ns((wdnow - watchdog_last) & watchdog->mask,
259 watchdog->mult, watchdog->shift);
260 watchdog_last = wdnow;
261
262 list_for_each_entry(cs, &watchdog_list, wd_list) {
263
264 /* Clocksource already marked unstable? */
265 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
266 if (finished_booting)
267 schedule_work(&watchdog_work);
268 continue;
269 }
270
271 csnow = cs->read(cs);
272
273 /* Clocksource initialized ? */
274 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
275 cs->flags |= CLOCK_SOURCE_WATCHDOG;
276 cs->wd_last = csnow;
277 continue;
278 }
279
280 /* Check the deviation from the watchdog clocksource. */
281 cs_nsec = clocksource_cyc2ns((csnow - cs->wd_last) &
282 cs->mask, cs->mult, cs->shift);
283 cs->wd_last = csnow;
284 if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
285 clocksource_unstable(cs, cs_nsec - wd_nsec);
286 continue;
287 }
288
289 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
290 (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
291 (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
292 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
293 /*
294 * We just marked the clocksource as highres-capable,
295 * notify the rest of the system as well so that we
296 * transition into high-res mode:
297 */
298 tick_clock_notify();
299 }
300 }
301
302 /*
303 * Cycle through CPUs to check if the CPUs stay synchronized
304 * to each other.
305 */
306 next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
307 if (next_cpu >= nr_cpu_ids)
308 next_cpu = cpumask_first(cpu_online_mask);
309 watchdog_timer.expires += WATCHDOG_INTERVAL;
310 add_timer_on(&watchdog_timer, next_cpu);
311out:
312 spin_unlock(&watchdog_lock);
313}
314
315static inline void clocksource_start_watchdog(void)
316{
317 if (watchdog_running || !watchdog || list_empty(&watchdog_list))
318 return;
319 init_timer(&watchdog_timer);
320 watchdog_timer.function = clocksource_watchdog;
321 watchdog_last = watchdog->read(watchdog);
322 watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
323 add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
324 watchdog_running = 1;
325}
326
327static inline void clocksource_stop_watchdog(void)
328{
329 if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
330 return;
331 del_timer(&watchdog_timer);
332 watchdog_running = 0;
333}
334
335static inline void clocksource_reset_watchdog(void)
336{
337 struct clocksource *cs;
338
339 list_for_each_entry(cs, &watchdog_list, wd_list)
340 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
341}
342
343static void clocksource_resume_watchdog(void)
344{
345 unsigned long flags;
346
347 /*
348 * We use trylock here to avoid a potential dead lock when
349 * kgdb calls this code after the kernel has been stopped with
350 * watchdog_lock held. When watchdog_lock is held we just
351 * return and accept, that the watchdog might trigger and mark
352 * the monitored clock source (usually TSC) unstable.
353 *
354 * This does not affect the other caller clocksource_resume()
355 * because at this point the kernel is UP, interrupts are
356 * disabled and nothing can hold watchdog_lock.
357 */
358 if (!spin_trylock_irqsave(&watchdog_lock, flags))
359 return;
360 clocksource_reset_watchdog();
361 spin_unlock_irqrestore(&watchdog_lock, flags);
362}
363
364static void clocksource_enqueue_watchdog(struct clocksource *cs)
365{
366 unsigned long flags;
367
368 spin_lock_irqsave(&watchdog_lock, flags);
369 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
370 /* cs is a clocksource to be watched. */
371 list_add(&cs->wd_list, &watchdog_list);
372 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
373 } else {
374 /* cs is a watchdog. */
375 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
376 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
377 /* Pick the best watchdog. */
378 if (!watchdog || cs->rating > watchdog->rating) {
379 watchdog = cs;
380 /* Reset watchdog cycles */
381 clocksource_reset_watchdog();
382 }
383 }
384 /* Check if the watchdog timer needs to be started. */
385 clocksource_start_watchdog();
386 spin_unlock_irqrestore(&watchdog_lock, flags);
387}
388
389static void clocksource_dequeue_watchdog(struct clocksource *cs)
390{
391 struct clocksource *tmp;
392 unsigned long flags;
393
394 spin_lock_irqsave(&watchdog_lock, flags);
395 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
396 /* cs is a watched clocksource. */
397 list_del_init(&cs->wd_list);
398 } else if (cs == watchdog) {
399 /* Reset watchdog cycles */
400 clocksource_reset_watchdog();
401 /* Current watchdog is removed. Find an alternative. */
402 watchdog = NULL;
403 list_for_each_entry(tmp, &clocksource_list, list) {
404 if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY)
405 continue;
406 if (!watchdog || tmp->rating > watchdog->rating)
407 watchdog = tmp;
408 }
409 }
410 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
411 /* Check if the watchdog timer needs to be stopped. */
412 clocksource_stop_watchdog();
413 spin_unlock_irqrestore(&watchdog_lock, flags);
414}
415
416static int clocksource_watchdog_kthread(void *data)
417{
418 struct clocksource *cs, *tmp;
419 unsigned long flags;
420 LIST_HEAD(unstable);
421
422 mutex_lock(&clocksource_mutex);
423 spin_lock_irqsave(&watchdog_lock, flags);
424 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)
425 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
426 list_del_init(&cs->wd_list);
427 list_add(&cs->wd_list, &unstable);
428 }
429 /* Check if the watchdog timer needs to be stopped. */
430 clocksource_stop_watchdog();
431 spin_unlock_irqrestore(&watchdog_lock, flags);
432
433 /* Needs to be done outside of watchdog lock */
434 list_for_each_entry_safe(cs, tmp, &unstable, wd_list) {
435 list_del_init(&cs->wd_list);
436 __clocksource_change_rating(cs, 0);
437 }
438 mutex_unlock(&clocksource_mutex);
439 return 0;
440}
441
442#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
443
444static void clocksource_enqueue_watchdog(struct clocksource *cs)
445{
446 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
447 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
448}
449
450static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
451static inline void clocksource_resume_watchdog(void) { }
452static inline int clocksource_watchdog_kthread(void *data) { return 0; }
453
454#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
455
456/**
457 * clocksource_suspend - suspend the clocksource(s)
458 */
459void clocksource_suspend(void)
460{
461 struct clocksource *cs;
462
463 list_for_each_entry_reverse(cs, &clocksource_list, list)
464 if (cs->suspend)
465 cs->suspend(cs);
466}
467
468/**
469 * clocksource_resume - resume the clocksource(s)
470 */
471void clocksource_resume(void)
472{
473 struct clocksource *cs;
474
475 list_for_each_entry(cs, &clocksource_list, list)
476 if (cs->resume)
477 cs->resume(cs);
478
479 clocksource_resume_watchdog();
480}
481
482/**
483 * clocksource_touch_watchdog - Update watchdog
484 *
485 * Update the watchdog after exception contexts such as kgdb so as not
486 * to incorrectly trip the watchdog. This might fail when the kernel
487 * was stopped in code which holds watchdog_lock.
488 */
489void clocksource_touch_watchdog(void)
490{
491 clocksource_resume_watchdog();
492}
493
494/**
495 * clocksource_max_deferment - Returns max time the clocksource can be deferred
496 * @cs: Pointer to clocksource
497 *
498 */
499static u64 clocksource_max_deferment(struct clocksource *cs)
500{
501 u64 max_nsecs, max_cycles;
502
503 /*
504 * Calculate the maximum number of cycles that we can pass to the
505 * cyc2ns function without overflowing a 64-bit signed result. The
506 * maximum number of cycles is equal to ULLONG_MAX/cs->mult which
507 * is equivalent to the below.
508 * max_cycles < (2^63)/cs->mult
509 * max_cycles < 2^(log2((2^63)/cs->mult))
510 * max_cycles < 2^(log2(2^63) - log2(cs->mult))
511 * max_cycles < 2^(63 - log2(cs->mult))
512 * max_cycles < 1 << (63 - log2(cs->mult))
513 * Please note that we add 1 to the result of the log2 to account for
514 * any rounding errors, ensure the above inequality is satisfied and
515 * no overflow will occur.
516 */
517 max_cycles = 1ULL << (63 - (ilog2(cs->mult) + 1));
518
519 /*
520 * The actual maximum number of cycles we can defer the clocksource is
521 * determined by the minimum of max_cycles and cs->mask.
522 */
523 max_cycles = min_t(u64, max_cycles, (u64) cs->mask);
524 max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult, cs->shift);
525
526 /*
527 * To ensure that the clocksource does not wrap whilst we are idle,
528 * limit the time the clocksource can be deferred by 12.5%. Please
529 * note a margin of 12.5% is used because this can be computed with
530 * a shift, versus say 10% which would require division.
531 */
532 return max_nsecs - (max_nsecs >> 5);
533}
534
535#ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
536
537/**
538 * clocksource_select - Select the best clocksource available
539 *
540 * Private function. Must hold clocksource_mutex when called.
541 *
542 * Select the clocksource with the best rating, or the clocksource,
543 * which is selected by userspace override.
544 */
545static void clocksource_select(void)
546{
547 struct clocksource *best, *cs;
548
549 if (!finished_booting || list_empty(&clocksource_list))
550 return;
551 /* First clocksource on the list has the best rating. */
552 best = list_first_entry(&clocksource_list, struct clocksource, list);
553 /* Check for the override clocksource. */
554 list_for_each_entry(cs, &clocksource_list, list) {
555 if (strcmp(cs->name, override_name) != 0)
556 continue;
557 /*
558 * Check to make sure we don't switch to a non-highres
559 * capable clocksource if the tick code is in oneshot
560 * mode (highres or nohz)
561 */
562 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
563 tick_oneshot_mode_active()) {
564 /* Override clocksource cannot be used. */
565 printk(KERN_WARNING "Override clocksource %s is not "
566 "HRT compatible. Cannot switch while in "
567 "HRT/NOHZ mode\n", cs->name);
568 override_name[0] = 0;
569 } else
570 /* Override clocksource can be used. */
571 best = cs;
572 break;
573 }
574 if (curr_clocksource != best) {
575 printk(KERN_INFO "Switching to clocksource %s\n", best->name);
576 curr_clocksource = best;
577 timekeeping_notify(curr_clocksource);
578 }
579}
580
581#else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */
582
583static inline void clocksource_select(void) { }
584
585#endif
586
587/*
588 * clocksource_done_booting - Called near the end of core bootup
589 *
590 * Hack to avoid lots of clocksource churn at boot time.
591 * We use fs_initcall because we want this to start before
592 * device_initcall but after subsys_initcall.
593 */
594static int __init clocksource_done_booting(void)
595{
596 mutex_lock(&clocksource_mutex);
597 curr_clocksource = clocksource_default_clock();
598 mutex_unlock(&clocksource_mutex);
599
600 finished_booting = 1;
601
602 /*
603 * Run the watchdog first to eliminate unstable clock sources
604 */
605 clocksource_watchdog_kthread(NULL);
606
607 mutex_lock(&clocksource_mutex);
608 clocksource_select();
609 mutex_unlock(&clocksource_mutex);
610 return 0;
611}
612fs_initcall(clocksource_done_booting);
613
614/*
615 * Enqueue the clocksource sorted by rating
616 */
617static void clocksource_enqueue(struct clocksource *cs)
618{
619 struct list_head *entry = &clocksource_list;
620 struct clocksource *tmp;
621
622 list_for_each_entry(tmp, &clocksource_list, list)
623 /* Keep track of the place, where to insert */
624 if (tmp->rating >= cs->rating)
625 entry = &tmp->list;
626 list_add(&cs->list, entry);
627}
628
629
630/*
631 * Maximum time we expect to go between ticks. This includes idle
632 * tickless time. It provides the trade off between selecting a
633 * mult/shift pair that is very precise but can only handle a short
634 * period of time, vs. a mult/shift pair that can handle long periods
635 * of time but isn't as precise.
636 *
637 * This is a subsystem constant, and actual hardware limitations
638 * may override it (ie: clocksources that wrap every 3 seconds).
639 */
640#define MAX_UPDATE_LENGTH 5 /* Seconds */
641
642/**
643 * __clocksource_updatefreq_scale - Used update clocksource with new freq
644 * @t: clocksource to be registered
645 * @scale: Scale factor multiplied against freq to get clocksource hz
646 * @freq: clocksource frequency (cycles per second) divided by scale
647 *
648 * This should only be called from the clocksource->enable() method.
649 *
650 * This *SHOULD NOT* be called directly! Please use the
651 * clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions.
652 */
653void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
654{
655 /*
656 * Ideally we want to use some of the limits used in
657 * clocksource_max_deferment, to provide a more informed
658 * MAX_UPDATE_LENGTH. But for now this just gets the
659 * register interface working properly.
660 */
661 clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
662 NSEC_PER_SEC/scale,
663 MAX_UPDATE_LENGTH*scale);
664 cs->max_idle_ns = clocksource_max_deferment(cs);
665}
666EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
667
668/**
669 * __clocksource_register_scale - Used to install new clocksources
670 * @t: clocksource to be registered
671 * @scale: Scale factor multiplied against freq to get clocksource hz
672 * @freq: clocksource frequency (cycles per second) divided by scale
673 *
674 * Returns -EBUSY if registration fails, zero otherwise.
675 *
676 * This *SHOULD NOT* be called directly! Please use the
677 * clocksource_register_hz() or clocksource_register_khz helper functions.
678 */
679int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
680{
681
682 /* Initialize mult/shift and max_idle_ns */
683 __clocksource_updatefreq_scale(cs, scale, freq);
684
685 /* Add clocksource to the clcoksource list */
686 mutex_lock(&clocksource_mutex);
687 clocksource_enqueue(cs);
688 clocksource_enqueue_watchdog(cs);
689 clocksource_select();
690 mutex_unlock(&clocksource_mutex);
691 return 0;
692}
693EXPORT_SYMBOL_GPL(__clocksource_register_scale);
694
695
696/**
697 * clocksource_register - Used to install new clocksources
698 * @t: clocksource to be registered
699 *
700 * Returns -EBUSY if registration fails, zero otherwise.
701 */
702int clocksource_register(struct clocksource *cs)
703{
704 /* calculate max idle time permitted for this clocksource */
705 cs->max_idle_ns = clocksource_max_deferment(cs);
706
707 mutex_lock(&clocksource_mutex);
708 clocksource_enqueue(cs);
709 clocksource_enqueue_watchdog(cs);
710 clocksource_select();
711 mutex_unlock(&clocksource_mutex);
712 return 0;
713}
714EXPORT_SYMBOL(clocksource_register);
715
716static void __clocksource_change_rating(struct clocksource *cs, int rating)
717{
718 list_del(&cs->list);
719 cs->rating = rating;
720 clocksource_enqueue(cs);
721 clocksource_select();
722}
723
724/**
725 * clocksource_change_rating - Change the rating of a registered clocksource
726 */
727void clocksource_change_rating(struct clocksource *cs, int rating)
728{
729 mutex_lock(&clocksource_mutex);
730 __clocksource_change_rating(cs, rating);
731 mutex_unlock(&clocksource_mutex);
732}
733EXPORT_SYMBOL(clocksource_change_rating);
734
735/**
736 * clocksource_unregister - remove a registered clocksource
737 */
738void clocksource_unregister(struct clocksource *cs)
739{
740 mutex_lock(&clocksource_mutex);
741 clocksource_dequeue_watchdog(cs);
742 list_del(&cs->list);
743 clocksource_select();
744 mutex_unlock(&clocksource_mutex);
745}
746EXPORT_SYMBOL(clocksource_unregister);
747
748#ifdef CONFIG_SYSFS
749/**
750 * sysfs_show_current_clocksources - sysfs interface for current clocksource
751 * @dev: unused
752 * @buf: char buffer to be filled with clocksource list
753 *
754 * Provides sysfs interface for listing current clocksource.
755 */
756static ssize_t
757sysfs_show_current_clocksources(struct sys_device *dev,
758 struct sysdev_attribute *attr, char *buf)
759{
760 ssize_t count = 0;
761
762 mutex_lock(&clocksource_mutex);
763 count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
764 mutex_unlock(&clocksource_mutex);
765
766 return count;
767}
768
769/**
770 * sysfs_override_clocksource - interface for manually overriding clocksource
771 * @dev: unused
772 * @buf: name of override clocksource
773 * @count: length of buffer
774 *
775 * Takes input from sysfs interface for manually overriding the default
776 * clocksource selection.
777 */
778static ssize_t sysfs_override_clocksource(struct sys_device *dev,
779 struct sysdev_attribute *attr,
780 const char *buf, size_t count)
781{
782 size_t ret = count;
783
784 /* strings from sysfs write are not 0 terminated! */
785 if (count >= sizeof(override_name))
786 return -EINVAL;
787
788 /* strip of \n: */
789 if (buf[count-1] == '\n')
790 count--;
791
792 mutex_lock(&clocksource_mutex);
793
794 if (count > 0)
795 memcpy(override_name, buf, count);
796 override_name[count] = 0;
797 clocksource_select();
798
799 mutex_unlock(&clocksource_mutex);
800
801 return ret;
802}
803
804/**
805 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
806 * @dev: unused
807 * @buf: char buffer to be filled with clocksource list
808 *
809 * Provides sysfs interface for listing registered clocksources
810 */
811static ssize_t
812sysfs_show_available_clocksources(struct sys_device *dev,
813 struct sysdev_attribute *attr,
814 char *buf)
815{
816 struct clocksource *src;
817 ssize_t count = 0;
818
819 mutex_lock(&clocksource_mutex);
820 list_for_each_entry(src, &clocksource_list, list) {
821 /*
822 * Don't show non-HRES clocksource if the tick code is
823 * in one shot mode (highres=on or nohz=on)
824 */
825 if (!tick_oneshot_mode_active() ||
826 (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
827 count += snprintf(buf + count,
828 max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
829 "%s ", src->name);
830 }
831 mutex_unlock(&clocksource_mutex);
832
833 count += snprintf(buf + count,
834 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
835
836 return count;
837}
838
839/*
840 * Sysfs setup bits:
841 */
842static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources,
843 sysfs_override_clocksource);
844
845static SYSDEV_ATTR(available_clocksource, 0444,
846 sysfs_show_available_clocksources, NULL);
847
848static struct sysdev_class clocksource_sysclass = {
849 .name = "clocksource",
850};
851
852static struct sys_device device_clocksource = {
853 .id = 0,
854 .cls = &clocksource_sysclass,
855};
856
857static int __init init_clocksource_sysfs(void)
858{
859 int error = sysdev_class_register(&clocksource_sysclass);
860
861 if (!error)
862 error = sysdev_register(&device_clocksource);
863 if (!error)
864 error = sysdev_create_file(
865 &device_clocksource,
866 &attr_current_clocksource);
867 if (!error)
868 error = sysdev_create_file(
869 &device_clocksource,
870 &attr_available_clocksource);
871 return error;
872}
873
874device_initcall(init_clocksource_sysfs);
875#endif /* CONFIG_SYSFS */
876
877/**
878 * boot_override_clocksource - boot clock override
879 * @str: override name
880 *
881 * Takes a clocksource= boot argument and uses it
882 * as the clocksource override name.
883 */
884static int __init boot_override_clocksource(char* str)
885{
886 mutex_lock(&clocksource_mutex);
887 if (str)
888 strlcpy(override_name, str, sizeof(override_name));
889 mutex_unlock(&clocksource_mutex);
890 return 1;
891}
892
893__setup("clocksource=", boot_override_clocksource);
894
895/**
896 * boot_override_clock - Compatibility layer for deprecated boot option
897 * @str: override name
898 *
899 * DEPRECATED! Takes a clock= boot argument and uses it
900 * as the clocksource override name
901 */
902static int __init boot_override_clock(char* str)
903{
904 if (!strcmp(str, "pmtmr")) {
905 printk("Warning: clock=pmtmr is deprecated. "
906 "Use clocksource=acpi_pm.\n");
907 return boot_override_clocksource("acpi_pm");
908 }
909 printk("Warning! clock= boot option is deprecated. "
910 "Use clocksource=xyz\n");
911 return boot_override_clocksource(str);
912}
913
914__setup("clock=", boot_override_clock);