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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/device.h>
27#include <linux/clocksource.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#include "tick-internal.h"
35
36void timecounter_init(struct timecounter *tc,
37 const struct cyclecounter *cc,
38 u64 start_tstamp)
39{
40 tc->cc = cc;
41 tc->cycle_last = cc->read(cc);
42 tc->nsec = start_tstamp;
43}
44EXPORT_SYMBOL_GPL(timecounter_init);
45
46/**
47 * timecounter_read_delta - get nanoseconds since last call of this function
48 * @tc: Pointer to time counter
49 *
50 * When the underlying cycle counter runs over, this will be handled
51 * correctly as long as it does not run over more than once between
52 * calls.
53 *
54 * The first call to this function for a new time counter initializes
55 * the time tracking and returns an undefined result.
56 */
57static u64 timecounter_read_delta(struct timecounter *tc)
58{
59 cycle_t cycle_now, cycle_delta;
60 u64 ns_offset;
61
62 /* read cycle counter: */
63 cycle_now = tc->cc->read(tc->cc);
64
65 /* calculate the delta since the last timecounter_read_delta(): */
66 cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
67
68 /* convert to nanoseconds: */
69 ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta);
70
71 /* update time stamp of timecounter_read_delta() call: */
72 tc->cycle_last = cycle_now;
73
74 return ns_offset;
75}
76
77u64 timecounter_read(struct timecounter *tc)
78{
79 u64 nsec;
80
81 /* increment time by nanoseconds since last call */
82 nsec = timecounter_read_delta(tc);
83 nsec += tc->nsec;
84 tc->nsec = nsec;
85
86 return nsec;
87}
88EXPORT_SYMBOL_GPL(timecounter_read);
89
90u64 timecounter_cyc2time(struct timecounter *tc,
91 cycle_t cycle_tstamp)
92{
93 u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask;
94 u64 nsec;
95
96 /*
97 * Instead of always treating cycle_tstamp as more recent
98 * than tc->cycle_last, detect when it is too far in the
99 * future and treat it as old time stamp instead.
100 */
101 if (cycle_delta > tc->cc->mask / 2) {
102 cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask;
103 nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta);
104 } else {
105 nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec;
106 }
107
108 return nsec;
109}
110EXPORT_SYMBOL_GPL(timecounter_cyc2time);
111
112/**
113 * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
114 * @mult: pointer to mult variable
115 * @shift: pointer to shift variable
116 * @from: frequency to convert from
117 * @to: frequency to convert to
118 * @maxsec: guaranteed runtime conversion range in seconds
119 *
120 * The function evaluates the shift/mult pair for the scaled math
121 * operations of clocksources and clockevents.
122 *
123 * @to and @from are frequency values in HZ. For clock sources @to is
124 * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
125 * event @to is the counter frequency and @from is NSEC_PER_SEC.
126 *
127 * The @maxsec conversion range argument controls the time frame in
128 * seconds which must be covered by the runtime conversion with the
129 * calculated mult and shift factors. This guarantees that no 64bit
130 * overflow happens when the input value of the conversion is
131 * multiplied with the calculated mult factor. Larger ranges may
132 * reduce the conversion accuracy by chosing smaller mult and shift
133 * factors.
134 */
135void
136clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
137{
138 u64 tmp;
139 u32 sft, sftacc= 32;
140
141 /*
142 * Calculate the shift factor which is limiting the conversion
143 * range:
144 */
145 tmp = ((u64)maxsec * from) >> 32;
146 while (tmp) {
147 tmp >>=1;
148 sftacc--;
149 }
150
151 /*
152 * Find the conversion shift/mult pair which has the best
153 * accuracy and fits the maxsec conversion range:
154 */
155 for (sft = 32; sft > 0; sft--) {
156 tmp = (u64) to << sft;
157 tmp += from / 2;
158 do_div(tmp, from);
159 if ((tmp >> sftacc) == 0)
160 break;
161 }
162 *mult = tmp;
163 *shift = sft;
164}
165
166/*[Clocksource internal variables]---------
167 * curr_clocksource:
168 * currently selected clocksource.
169 * clocksource_list:
170 * linked list with the registered clocksources
171 * clocksource_mutex:
172 * protects manipulations to curr_clocksource and the clocksource_list
173 * override_name:
174 * Name of the user-specified clocksource.
175 */
176static struct clocksource *curr_clocksource;
177static LIST_HEAD(clocksource_list);
178static DEFINE_MUTEX(clocksource_mutex);
179static char override_name[CS_NAME_LEN];
180static int finished_booting;
181
182#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
183static void clocksource_watchdog_work(struct work_struct *work);
184static void clocksource_select(void);
185
186static LIST_HEAD(watchdog_list);
187static struct clocksource *watchdog;
188static struct timer_list watchdog_timer;
189static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
190static DEFINE_SPINLOCK(watchdog_lock);
191static int watchdog_running;
192static atomic_t watchdog_reset_pending;
193
194static int clocksource_watchdog_kthread(void *data);
195static void __clocksource_change_rating(struct clocksource *cs, int rating);
196
197/*
198 * Interval: 0.5sec Threshold: 0.0625s
199 */
200#define WATCHDOG_INTERVAL (HZ >> 1)
201#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
202
203static void clocksource_watchdog_work(struct work_struct *work)
204{
205 /*
206 * If kthread_run fails the next watchdog scan over the
207 * watchdog_list will find the unstable clock again.
208 */
209 kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
210}
211
212static void __clocksource_unstable(struct clocksource *cs)
213{
214 cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
215 cs->flags |= CLOCK_SOURCE_UNSTABLE;
216 if (finished_booting)
217 schedule_work(&watchdog_work);
218}
219
220static void clocksource_unstable(struct clocksource *cs, int64_t delta)
221{
222 printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
223 cs->name, delta);
224 __clocksource_unstable(cs);
225}
226
227/**
228 * clocksource_mark_unstable - mark clocksource unstable via watchdog
229 * @cs: clocksource to be marked unstable
230 *
231 * This function is called instead of clocksource_change_rating from
232 * cpu hotplug code to avoid a deadlock between the clocksource mutex
233 * and the cpu hotplug mutex. It defers the update of the clocksource
234 * to the watchdog thread.
235 */
236void clocksource_mark_unstable(struct clocksource *cs)
237{
238 unsigned long flags;
239
240 spin_lock_irqsave(&watchdog_lock, flags);
241 if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
242 if (list_empty(&cs->wd_list))
243 list_add(&cs->wd_list, &watchdog_list);
244 __clocksource_unstable(cs);
245 }
246 spin_unlock_irqrestore(&watchdog_lock, flags);
247}
248
249static void clocksource_watchdog(unsigned long data)
250{
251 struct clocksource *cs;
252 cycle_t csnow, wdnow;
253 int64_t wd_nsec, cs_nsec;
254 int next_cpu, reset_pending;
255
256 spin_lock(&watchdog_lock);
257 if (!watchdog_running)
258 goto out;
259
260 reset_pending = atomic_read(&watchdog_reset_pending);
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 local_irq_disable();
272 csnow = cs->read(cs);
273 wdnow = watchdog->read(watchdog);
274 local_irq_enable();
275
276 /* Clocksource initialized ? */
277 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
278 atomic_read(&watchdog_reset_pending)) {
279 cs->flags |= CLOCK_SOURCE_WATCHDOG;
280 cs->wd_last = wdnow;
281 cs->cs_last = csnow;
282 continue;
283 }
284
285 wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog->mask,
286 watchdog->mult, watchdog->shift);
287
288 cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) &
289 cs->mask, cs->mult, cs->shift);
290 cs->cs_last = csnow;
291 cs->wd_last = wdnow;
292
293 if (atomic_read(&watchdog_reset_pending))
294 continue;
295
296 /* Check the deviation from the watchdog clocksource. */
297 if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) {
298 clocksource_unstable(cs, cs_nsec - wd_nsec);
299 continue;
300 }
301
302 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
303 (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
304 (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
305 /* Mark it valid for high-res. */
306 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
307
308 /*
309 * clocksource_done_booting() will sort it if
310 * finished_booting is not set yet.
311 */
312 if (!finished_booting)
313 continue;
314
315 /*
316 * If this is not the current clocksource let
317 * the watchdog thread reselect it. Due to the
318 * change to high res this clocksource might
319 * be preferred now. If it is the current
320 * clocksource let the tick code know about
321 * that change.
322 */
323 if (cs != curr_clocksource) {
324 cs->flags |= CLOCK_SOURCE_RESELECT;
325 schedule_work(&watchdog_work);
326 } else {
327 tick_clock_notify();
328 }
329 }
330 }
331
332 /*
333 * We only clear the watchdog_reset_pending, when we did a
334 * full cycle through all clocksources.
335 */
336 if (reset_pending)
337 atomic_dec(&watchdog_reset_pending);
338
339 /*
340 * Cycle through CPUs to check if the CPUs stay synchronized
341 * to each other.
342 */
343 next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
344 if (next_cpu >= nr_cpu_ids)
345 next_cpu = cpumask_first(cpu_online_mask);
346 watchdog_timer.expires += WATCHDOG_INTERVAL;
347 add_timer_on(&watchdog_timer, next_cpu);
348out:
349 spin_unlock(&watchdog_lock);
350}
351
352static inline void clocksource_start_watchdog(void)
353{
354 if (watchdog_running || !watchdog || list_empty(&watchdog_list))
355 return;
356 init_timer(&watchdog_timer);
357 watchdog_timer.function = clocksource_watchdog;
358 watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
359 add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
360 watchdog_running = 1;
361}
362
363static inline void clocksource_stop_watchdog(void)
364{
365 if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
366 return;
367 del_timer(&watchdog_timer);
368 watchdog_running = 0;
369}
370
371static inline void clocksource_reset_watchdog(void)
372{
373 struct clocksource *cs;
374
375 list_for_each_entry(cs, &watchdog_list, wd_list)
376 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
377}
378
379static void clocksource_resume_watchdog(void)
380{
381 atomic_inc(&watchdog_reset_pending);
382}
383
384static void clocksource_enqueue_watchdog(struct clocksource *cs)
385{
386 unsigned long flags;
387
388 spin_lock_irqsave(&watchdog_lock, flags);
389 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
390 /* cs is a clocksource to be watched. */
391 list_add(&cs->wd_list, &watchdog_list);
392 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
393 } else {
394 /* cs is a watchdog. */
395 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
396 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
397 /* Pick the best watchdog. */
398 if (!watchdog || cs->rating > watchdog->rating) {
399 watchdog = cs;
400 /* Reset watchdog cycles */
401 clocksource_reset_watchdog();
402 }
403 }
404 /* Check if the watchdog timer needs to be started. */
405 clocksource_start_watchdog();
406 spin_unlock_irqrestore(&watchdog_lock, flags);
407}
408
409static void clocksource_dequeue_watchdog(struct clocksource *cs)
410{
411 unsigned long flags;
412
413 spin_lock_irqsave(&watchdog_lock, flags);
414 if (cs != watchdog) {
415 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
416 /* cs is a watched clocksource. */
417 list_del_init(&cs->wd_list);
418 /* Check if the watchdog timer needs to be stopped. */
419 clocksource_stop_watchdog();
420 }
421 }
422 spin_unlock_irqrestore(&watchdog_lock, flags);
423}
424
425static int __clocksource_watchdog_kthread(void)
426{
427 struct clocksource *cs, *tmp;
428 unsigned long flags;
429 LIST_HEAD(unstable);
430 int select = 0;
431
432 spin_lock_irqsave(&watchdog_lock, flags);
433 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
434 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
435 list_del_init(&cs->wd_list);
436 list_add(&cs->wd_list, &unstable);
437 select = 1;
438 }
439 if (cs->flags & CLOCK_SOURCE_RESELECT) {
440 cs->flags &= ~CLOCK_SOURCE_RESELECT;
441 select = 1;
442 }
443 }
444 /* Check if the watchdog timer needs to be stopped. */
445 clocksource_stop_watchdog();
446 spin_unlock_irqrestore(&watchdog_lock, flags);
447
448 /* Needs to be done outside of watchdog lock */
449 list_for_each_entry_safe(cs, tmp, &unstable, wd_list) {
450 list_del_init(&cs->wd_list);
451 __clocksource_change_rating(cs, 0);
452 }
453 return select;
454}
455
456static int clocksource_watchdog_kthread(void *data)
457{
458 mutex_lock(&clocksource_mutex);
459 if (__clocksource_watchdog_kthread())
460 clocksource_select();
461 mutex_unlock(&clocksource_mutex);
462 return 0;
463}
464
465static bool clocksource_is_watchdog(struct clocksource *cs)
466{
467 return cs == watchdog;
468}
469
470#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
471
472static void clocksource_enqueue_watchdog(struct clocksource *cs)
473{
474 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
475 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
476}
477
478static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
479static inline void clocksource_resume_watchdog(void) { }
480static inline int __clocksource_watchdog_kthread(void) { return 0; }
481static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
482void clocksource_mark_unstable(struct clocksource *cs) { }
483
484#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
485
486/**
487 * clocksource_suspend - suspend the clocksource(s)
488 */
489void clocksource_suspend(void)
490{
491 struct clocksource *cs;
492
493 list_for_each_entry_reverse(cs, &clocksource_list, list)
494 if (cs->suspend)
495 cs->suspend(cs);
496}
497
498/**
499 * clocksource_resume - resume the clocksource(s)
500 */
501void clocksource_resume(void)
502{
503 struct clocksource *cs;
504
505 list_for_each_entry(cs, &clocksource_list, list)
506 if (cs->resume)
507 cs->resume(cs);
508
509 clocksource_resume_watchdog();
510}
511
512/**
513 * clocksource_touch_watchdog - Update watchdog
514 *
515 * Update the watchdog after exception contexts such as kgdb so as not
516 * to incorrectly trip the watchdog. This might fail when the kernel
517 * was stopped in code which holds watchdog_lock.
518 */
519void clocksource_touch_watchdog(void)
520{
521 clocksource_resume_watchdog();
522}
523
524/**
525 * clocksource_max_adjustment- Returns max adjustment amount
526 * @cs: Pointer to clocksource
527 *
528 */
529static u32 clocksource_max_adjustment(struct clocksource *cs)
530{
531 u64 ret;
532 /*
533 * We won't try to correct for more than 11% adjustments (110,000 ppm),
534 */
535 ret = (u64)cs->mult * 11;
536 do_div(ret,100);
537 return (u32)ret;
538}
539
540/**
541 * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
542 * @mult: cycle to nanosecond multiplier
543 * @shift: cycle to nanosecond divisor (power of two)
544 * @maxadj: maximum adjustment value to mult (~11%)
545 * @mask: bitmask for two's complement subtraction of non 64 bit counters
546 */
547u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask)
548{
549 u64 max_nsecs, max_cycles;
550
551 /*
552 * Calculate the maximum number of cycles that we can pass to the
553 * cyc2ns function without overflowing a 64-bit signed result. The
554 * maximum number of cycles is equal to ULLONG_MAX/(mult+maxadj)
555 * which is equivalent to the below.
556 * max_cycles < (2^63)/(mult + maxadj)
557 * max_cycles < 2^(log2((2^63)/(mult + maxadj)))
558 * max_cycles < 2^(log2(2^63) - log2(mult + maxadj))
559 * max_cycles < 2^(63 - log2(mult + maxadj))
560 * max_cycles < 1 << (63 - log2(mult + maxadj))
561 * Please note that we add 1 to the result of the log2 to account for
562 * any rounding errors, ensure the above inequality is satisfied and
563 * no overflow will occur.
564 */
565 max_cycles = 1ULL << (63 - (ilog2(mult + maxadj) + 1));
566
567 /*
568 * The actual maximum number of cycles we can defer the clocksource is
569 * determined by the minimum of max_cycles and mask.
570 * Note: Here we subtract the maxadj to make sure we don't sleep for
571 * too long if there's a large negative adjustment.
572 */
573 max_cycles = min(max_cycles, mask);
574 max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
575
576 return max_nsecs;
577}
578
579/**
580 * clocksource_max_deferment - Returns max time the clocksource can be deferred
581 * @cs: Pointer to clocksource
582 *
583 */
584static u64 clocksource_max_deferment(struct clocksource *cs)
585{
586 u64 max_nsecs;
587
588 max_nsecs = clocks_calc_max_nsecs(cs->mult, cs->shift, cs->maxadj,
589 cs->mask);
590 /*
591 * To ensure that the clocksource does not wrap whilst we are idle,
592 * limit the time the clocksource can be deferred by 12.5%. Please
593 * note a margin of 12.5% is used because this can be computed with
594 * a shift, versus say 10% which would require division.
595 */
596 return max_nsecs - (max_nsecs >> 3);
597}
598
599#ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
600
601static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
602{
603 struct clocksource *cs;
604
605 if (!finished_booting || list_empty(&clocksource_list))
606 return NULL;
607
608 /*
609 * We pick the clocksource with the highest rating. If oneshot
610 * mode is active, we pick the highres valid clocksource with
611 * the best rating.
612 */
613 list_for_each_entry(cs, &clocksource_list, list) {
614 if (skipcur && cs == curr_clocksource)
615 continue;
616 if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES))
617 continue;
618 return cs;
619 }
620 return NULL;
621}
622
623static void __clocksource_select(bool skipcur)
624{
625 bool oneshot = tick_oneshot_mode_active();
626 struct clocksource *best, *cs;
627
628 /* Find the best suitable clocksource */
629 best = clocksource_find_best(oneshot, skipcur);
630 if (!best)
631 return;
632
633 /* Check for the override clocksource. */
634 list_for_each_entry(cs, &clocksource_list, list) {
635 if (skipcur && cs == curr_clocksource)
636 continue;
637 if (strcmp(cs->name, override_name) != 0)
638 continue;
639 /*
640 * Check to make sure we don't switch to a non-highres
641 * capable clocksource if the tick code is in oneshot
642 * mode (highres or nohz)
643 */
644 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
645 /* Override clocksource cannot be used. */
646 printk(KERN_WARNING "Override clocksource %s is not "
647 "HRT compatible. Cannot switch while in "
648 "HRT/NOHZ mode\n", cs->name);
649 override_name[0] = 0;
650 } else
651 /* Override clocksource can be used. */
652 best = cs;
653 break;
654 }
655
656 if (curr_clocksource != best && !timekeeping_notify(best)) {
657 pr_info("Switched to clocksource %s\n", best->name);
658 curr_clocksource = best;
659 }
660}
661
662/**
663 * clocksource_select - Select the best clocksource available
664 *
665 * Private function. Must hold clocksource_mutex when called.
666 *
667 * Select the clocksource with the best rating, or the clocksource,
668 * which is selected by userspace override.
669 */
670static void clocksource_select(void)
671{
672 return __clocksource_select(false);
673}
674
675static void clocksource_select_fallback(void)
676{
677 return __clocksource_select(true);
678}
679
680#else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */
681
682static inline void clocksource_select(void) { }
683static inline void clocksource_select_fallback(void) { }
684
685#endif
686
687/*
688 * clocksource_done_booting - Called near the end of core bootup
689 *
690 * Hack to avoid lots of clocksource churn at boot time.
691 * We use fs_initcall because we want this to start before
692 * device_initcall but after subsys_initcall.
693 */
694static int __init clocksource_done_booting(void)
695{
696 mutex_lock(&clocksource_mutex);
697 curr_clocksource = clocksource_default_clock();
698 finished_booting = 1;
699 /*
700 * Run the watchdog first to eliminate unstable clock sources
701 */
702 __clocksource_watchdog_kthread();
703 clocksource_select();
704 mutex_unlock(&clocksource_mutex);
705 return 0;
706}
707fs_initcall(clocksource_done_booting);
708
709/*
710 * Enqueue the clocksource sorted by rating
711 */
712static void clocksource_enqueue(struct clocksource *cs)
713{
714 struct list_head *entry = &clocksource_list;
715 struct clocksource *tmp;
716
717 list_for_each_entry(tmp, &clocksource_list, list)
718 /* Keep track of the place, where to insert */
719 if (tmp->rating >= cs->rating)
720 entry = &tmp->list;
721 list_add(&cs->list, entry);
722}
723
724/**
725 * __clocksource_updatefreq_scale - Used update clocksource with new freq
726 * @cs: clocksource to be registered
727 * @scale: Scale factor multiplied against freq to get clocksource hz
728 * @freq: clocksource frequency (cycles per second) divided by scale
729 *
730 * This should only be called from the clocksource->enable() method.
731 *
732 * This *SHOULD NOT* be called directly! Please use the
733 * clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions.
734 */
735void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
736{
737 u64 sec;
738 /*
739 * Calc the maximum number of seconds which we can run before
740 * wrapping around. For clocksources which have a mask > 32bit
741 * we need to limit the max sleep time to have a good
742 * conversion precision. 10 minutes is still a reasonable
743 * amount. That results in a shift value of 24 for a
744 * clocksource with mask >= 40bit and f >= 4GHz. That maps to
745 * ~ 0.06ppm granularity for NTP. We apply the same 12.5%
746 * margin as we do in clocksource_max_deferment()
747 */
748 sec = (cs->mask - (cs->mask >> 3));
749 do_div(sec, freq);
750 do_div(sec, scale);
751 if (!sec)
752 sec = 1;
753 else if (sec > 600 && cs->mask > UINT_MAX)
754 sec = 600;
755
756 clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
757 NSEC_PER_SEC / scale, sec * scale);
758
759 /*
760 * for clocksources that have large mults, to avoid overflow.
761 * Since mult may be adjusted by ntp, add an safety extra margin
762 *
763 */
764 cs->maxadj = clocksource_max_adjustment(cs);
765 while ((cs->mult + cs->maxadj < cs->mult)
766 || (cs->mult - cs->maxadj > cs->mult)) {
767 cs->mult >>= 1;
768 cs->shift--;
769 cs->maxadj = clocksource_max_adjustment(cs);
770 }
771
772 cs->max_idle_ns = clocksource_max_deferment(cs);
773}
774EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
775
776/**
777 * __clocksource_register_scale - Used to install new clocksources
778 * @cs: clocksource to be registered
779 * @scale: Scale factor multiplied against freq to get clocksource hz
780 * @freq: clocksource frequency (cycles per second) divided by scale
781 *
782 * Returns -EBUSY if registration fails, zero otherwise.
783 *
784 * This *SHOULD NOT* be called directly! Please use the
785 * clocksource_register_hz() or clocksource_register_khz helper functions.
786 */
787int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
788{
789
790 /* Initialize mult/shift and max_idle_ns */
791 __clocksource_updatefreq_scale(cs, scale, freq);
792
793 /* Add clocksource to the clcoksource list */
794 mutex_lock(&clocksource_mutex);
795 clocksource_enqueue(cs);
796 clocksource_enqueue_watchdog(cs);
797 clocksource_select();
798 mutex_unlock(&clocksource_mutex);
799 return 0;
800}
801EXPORT_SYMBOL_GPL(__clocksource_register_scale);
802
803
804/**
805 * clocksource_register - Used to install new clocksources
806 * @cs: clocksource to be registered
807 *
808 * Returns -EBUSY if registration fails, zero otherwise.
809 */
810int clocksource_register(struct clocksource *cs)
811{
812 /* calculate max adjustment for given mult/shift */
813 cs->maxadj = clocksource_max_adjustment(cs);
814 WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
815 "Clocksource %s might overflow on 11%% adjustment\n",
816 cs->name);
817
818 /* calculate max idle time permitted for this clocksource */
819 cs->max_idle_ns = clocksource_max_deferment(cs);
820
821 mutex_lock(&clocksource_mutex);
822 clocksource_enqueue(cs);
823 clocksource_enqueue_watchdog(cs);
824 clocksource_select();
825 mutex_unlock(&clocksource_mutex);
826 return 0;
827}
828EXPORT_SYMBOL(clocksource_register);
829
830static void __clocksource_change_rating(struct clocksource *cs, int rating)
831{
832 list_del(&cs->list);
833 cs->rating = rating;
834 clocksource_enqueue(cs);
835}
836
837/**
838 * clocksource_change_rating - Change the rating of a registered clocksource
839 * @cs: clocksource to be changed
840 * @rating: new rating
841 */
842void clocksource_change_rating(struct clocksource *cs, int rating)
843{
844 mutex_lock(&clocksource_mutex);
845 __clocksource_change_rating(cs, rating);
846 clocksource_select();
847 mutex_unlock(&clocksource_mutex);
848}
849EXPORT_SYMBOL(clocksource_change_rating);
850
851/*
852 * Unbind clocksource @cs. Called with clocksource_mutex held
853 */
854static int clocksource_unbind(struct clocksource *cs)
855{
856 /*
857 * I really can't convince myself to support this on hardware
858 * designed by lobotomized monkeys.
859 */
860 if (clocksource_is_watchdog(cs))
861 return -EBUSY;
862
863 if (cs == curr_clocksource) {
864 /* Select and try to install a replacement clock source */
865 clocksource_select_fallback();
866 if (curr_clocksource == cs)
867 return -EBUSY;
868 }
869 clocksource_dequeue_watchdog(cs);
870 list_del_init(&cs->list);
871 return 0;
872}
873
874/**
875 * clocksource_unregister - remove a registered clocksource
876 * @cs: clocksource to be unregistered
877 */
878int clocksource_unregister(struct clocksource *cs)
879{
880 int ret = 0;
881
882 mutex_lock(&clocksource_mutex);
883 if (!list_empty(&cs->list))
884 ret = clocksource_unbind(cs);
885 mutex_unlock(&clocksource_mutex);
886 return ret;
887}
888EXPORT_SYMBOL(clocksource_unregister);
889
890#ifdef CONFIG_SYSFS
891/**
892 * sysfs_show_current_clocksources - sysfs interface for current clocksource
893 * @dev: unused
894 * @attr: unused
895 * @buf: char buffer to be filled with clocksource list
896 *
897 * Provides sysfs interface for listing current clocksource.
898 */
899static ssize_t
900sysfs_show_current_clocksources(struct device *dev,
901 struct device_attribute *attr, char *buf)
902{
903 ssize_t count = 0;
904
905 mutex_lock(&clocksource_mutex);
906 count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
907 mutex_unlock(&clocksource_mutex);
908
909 return count;
910}
911
912ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
913{
914 size_t ret = cnt;
915
916 /* strings from sysfs write are not 0 terminated! */
917 if (!cnt || cnt >= CS_NAME_LEN)
918 return -EINVAL;
919
920 /* strip of \n: */
921 if (buf[cnt-1] == '\n')
922 cnt--;
923 if (cnt > 0)
924 memcpy(dst, buf, cnt);
925 dst[cnt] = 0;
926 return ret;
927}
928
929/**
930 * sysfs_override_clocksource - interface for manually overriding clocksource
931 * @dev: unused
932 * @attr: unused
933 * @buf: name of override clocksource
934 * @count: length of buffer
935 *
936 * Takes input from sysfs interface for manually overriding the default
937 * clocksource selection.
938 */
939static ssize_t sysfs_override_clocksource(struct device *dev,
940 struct device_attribute *attr,
941 const char *buf, size_t count)
942{
943 ssize_t ret;
944
945 mutex_lock(&clocksource_mutex);
946
947 ret = sysfs_get_uname(buf, override_name, count);
948 if (ret >= 0)
949 clocksource_select();
950
951 mutex_unlock(&clocksource_mutex);
952
953 return ret;
954}
955
956/**
957 * sysfs_unbind_current_clocksource - interface for manually unbinding clocksource
958 * @dev: unused
959 * @attr: unused
960 * @buf: unused
961 * @count: length of buffer
962 *
963 * Takes input from sysfs interface for manually unbinding a clocksource.
964 */
965static ssize_t sysfs_unbind_clocksource(struct device *dev,
966 struct device_attribute *attr,
967 const char *buf, size_t count)
968{
969 struct clocksource *cs;
970 char name[CS_NAME_LEN];
971 ssize_t ret;
972
973 ret = sysfs_get_uname(buf, name, count);
974 if (ret < 0)
975 return ret;
976
977 ret = -ENODEV;
978 mutex_lock(&clocksource_mutex);
979 list_for_each_entry(cs, &clocksource_list, list) {
980 if (strcmp(cs->name, name))
981 continue;
982 ret = clocksource_unbind(cs);
983 break;
984 }
985 mutex_unlock(&clocksource_mutex);
986
987 return ret ? ret : count;
988}
989
990/**
991 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
992 * @dev: unused
993 * @attr: unused
994 * @buf: char buffer to be filled with clocksource list
995 *
996 * Provides sysfs interface for listing registered clocksources
997 */
998static ssize_t
999sysfs_show_available_clocksources(struct device *dev,
1000 struct device_attribute *attr,
1001 char *buf)
1002{
1003 struct clocksource *src;
1004 ssize_t count = 0;
1005
1006 mutex_lock(&clocksource_mutex);
1007 list_for_each_entry(src, &clocksource_list, list) {
1008 /*
1009 * Don't show non-HRES clocksource if the tick code is
1010 * in one shot mode (highres=on or nohz=on)
1011 */
1012 if (!tick_oneshot_mode_active() ||
1013 (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
1014 count += snprintf(buf + count,
1015 max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
1016 "%s ", src->name);
1017 }
1018 mutex_unlock(&clocksource_mutex);
1019
1020 count += snprintf(buf + count,
1021 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
1022
1023 return count;
1024}
1025
1026/*
1027 * Sysfs setup bits:
1028 */
1029static DEVICE_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources,
1030 sysfs_override_clocksource);
1031
1032static DEVICE_ATTR(unbind_clocksource, 0200, NULL, sysfs_unbind_clocksource);
1033
1034static DEVICE_ATTR(available_clocksource, 0444,
1035 sysfs_show_available_clocksources, NULL);
1036
1037static struct bus_type clocksource_subsys = {
1038 .name = "clocksource",
1039 .dev_name = "clocksource",
1040};
1041
1042static struct device device_clocksource = {
1043 .id = 0,
1044 .bus = &clocksource_subsys,
1045};
1046
1047static int __init init_clocksource_sysfs(void)
1048{
1049 int error = subsys_system_register(&clocksource_subsys, NULL);
1050
1051 if (!error)
1052 error = device_register(&device_clocksource);
1053 if (!error)
1054 error = device_create_file(
1055 &device_clocksource,
1056 &dev_attr_current_clocksource);
1057 if (!error)
1058 error = device_create_file(&device_clocksource,
1059 &dev_attr_unbind_clocksource);
1060 if (!error)
1061 error = device_create_file(
1062 &device_clocksource,
1063 &dev_attr_available_clocksource);
1064 return error;
1065}
1066
1067device_initcall(init_clocksource_sysfs);
1068#endif /* CONFIG_SYSFS */
1069
1070/**
1071 * boot_override_clocksource - boot clock override
1072 * @str: override name
1073 *
1074 * Takes a clocksource= boot argument and uses it
1075 * as the clocksource override name.
1076 */
1077static int __init boot_override_clocksource(char* str)
1078{
1079 mutex_lock(&clocksource_mutex);
1080 if (str)
1081 strlcpy(override_name, str, sizeof(override_name));
1082 mutex_unlock(&clocksource_mutex);
1083 return 1;
1084}
1085
1086__setup("clocksource=", boot_override_clocksource);
1087
1088/**
1089 * boot_override_clock - Compatibility layer for deprecated boot option
1090 * @str: override name
1091 *
1092 * DEPRECATED! Takes a clock= boot argument and uses it
1093 * as the clocksource override name
1094 */
1095static int __init boot_override_clock(char* str)
1096{
1097 if (!strcmp(str, "pmtmr")) {
1098 printk("Warning: clock=pmtmr is deprecated. "
1099 "Use clocksource=acpi_pm.\n");
1100 return boot_override_clocksource("acpi_pm");
1101 }
1102 printk("Warning! clock= boot option is deprecated. "
1103 "Use clocksource=xyz\n");
1104 return boot_override_clocksource(str);
1105}
1106
1107__setup("clock=", boot_override_clock);
1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * This file contains the functions which manage clocksource drivers.
4 *
5 * Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
6 */
7
8#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
9
10#include <linux/device.h>
11#include <linux/clocksource.h>
12#include <linux/init.h>
13#include <linux/module.h>
14#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
15#include <linux/tick.h>
16#include <linux/kthread.h>
17#include <linux/prandom.h>
18#include <linux/cpu.h>
19
20#include "tick-internal.h"
21#include "timekeeping_internal.h"
22
23/**
24 * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
25 * @mult: pointer to mult variable
26 * @shift: pointer to shift variable
27 * @from: frequency to convert from
28 * @to: frequency to convert to
29 * @maxsec: guaranteed runtime conversion range in seconds
30 *
31 * The function evaluates the shift/mult pair for the scaled math
32 * operations of clocksources and clockevents.
33 *
34 * @to and @from are frequency values in HZ. For clock sources @to is
35 * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
36 * event @to is the counter frequency and @from is NSEC_PER_SEC.
37 *
38 * The @maxsec conversion range argument controls the time frame in
39 * seconds which must be covered by the runtime conversion with the
40 * calculated mult and shift factors. This guarantees that no 64bit
41 * overflow happens when the input value of the conversion is
42 * multiplied with the calculated mult factor. Larger ranges may
43 * reduce the conversion accuracy by choosing smaller mult and shift
44 * factors.
45 */
46void
47clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
48{
49 u64 tmp;
50 u32 sft, sftacc= 32;
51
52 /*
53 * Calculate the shift factor which is limiting the conversion
54 * range:
55 */
56 tmp = ((u64)maxsec * from) >> 32;
57 while (tmp) {
58 tmp >>=1;
59 sftacc--;
60 }
61
62 /*
63 * Find the conversion shift/mult pair which has the best
64 * accuracy and fits the maxsec conversion range:
65 */
66 for (sft = 32; sft > 0; sft--) {
67 tmp = (u64) to << sft;
68 tmp += from / 2;
69 do_div(tmp, from);
70 if ((tmp >> sftacc) == 0)
71 break;
72 }
73 *mult = tmp;
74 *shift = sft;
75}
76EXPORT_SYMBOL_GPL(clocks_calc_mult_shift);
77
78/*[Clocksource internal variables]---------
79 * curr_clocksource:
80 * currently selected clocksource.
81 * suspend_clocksource:
82 * used to calculate the suspend time.
83 * clocksource_list:
84 * linked list with the registered clocksources
85 * clocksource_mutex:
86 * protects manipulations to curr_clocksource and the clocksource_list
87 * override_name:
88 * Name of the user-specified clocksource.
89 */
90static struct clocksource *curr_clocksource;
91static struct clocksource *suspend_clocksource;
92static LIST_HEAD(clocksource_list);
93static DEFINE_MUTEX(clocksource_mutex);
94static char override_name[CS_NAME_LEN];
95static int finished_booting;
96static u64 suspend_start;
97
98/*
99 * Threshold: 0.0312s, when doubled: 0.0625s.
100 * Also a default for cs->uncertainty_margin when registering clocks.
101 */
102#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5)
103
104/*
105 * Maximum permissible delay between two readouts of the watchdog
106 * clocksource surrounding a read of the clocksource being validated.
107 * This delay could be due to SMIs, NMIs, or to VCPU preemptions. Used as
108 * a lower bound for cs->uncertainty_margin values when registering clocks.
109 */
110#define WATCHDOG_MAX_SKEW (50 * NSEC_PER_USEC)
111
112#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
113static void clocksource_watchdog_work(struct work_struct *work);
114static void clocksource_select(void);
115
116static LIST_HEAD(watchdog_list);
117static struct clocksource *watchdog;
118static struct timer_list watchdog_timer;
119static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
120static DEFINE_SPINLOCK(watchdog_lock);
121static int watchdog_running;
122static atomic_t watchdog_reset_pending;
123
124static inline void clocksource_watchdog_lock(unsigned long *flags)
125{
126 spin_lock_irqsave(&watchdog_lock, *flags);
127}
128
129static inline void clocksource_watchdog_unlock(unsigned long *flags)
130{
131 spin_unlock_irqrestore(&watchdog_lock, *flags);
132}
133
134static int clocksource_watchdog_kthread(void *data);
135static void __clocksource_change_rating(struct clocksource *cs, int rating);
136
137/*
138 * Interval: 0.5sec.
139 */
140#define WATCHDOG_INTERVAL (HZ >> 1)
141
142static void clocksource_watchdog_work(struct work_struct *work)
143{
144 /*
145 * We cannot directly run clocksource_watchdog_kthread() here, because
146 * clocksource_select() calls timekeeping_notify() which uses
147 * stop_machine(). One cannot use stop_machine() from a workqueue() due
148 * lock inversions wrt CPU hotplug.
149 *
150 * Also, we only ever run this work once or twice during the lifetime
151 * of the kernel, so there is no point in creating a more permanent
152 * kthread for this.
153 *
154 * If kthread_run fails the next watchdog scan over the
155 * watchdog_list will find the unstable clock again.
156 */
157 kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
158}
159
160static void __clocksource_unstable(struct clocksource *cs)
161{
162 cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
163 cs->flags |= CLOCK_SOURCE_UNSTABLE;
164
165 /*
166 * If the clocksource is registered clocksource_watchdog_kthread() will
167 * re-rate and re-select.
168 */
169 if (list_empty(&cs->list)) {
170 cs->rating = 0;
171 return;
172 }
173
174 if (cs->mark_unstable)
175 cs->mark_unstable(cs);
176
177 /* kick clocksource_watchdog_kthread() */
178 if (finished_booting)
179 schedule_work(&watchdog_work);
180}
181
182/**
183 * clocksource_mark_unstable - mark clocksource unstable via watchdog
184 * @cs: clocksource to be marked unstable
185 *
186 * This function is called by the x86 TSC code to mark clocksources as unstable;
187 * it defers demotion and re-selection to a kthread.
188 */
189void clocksource_mark_unstable(struct clocksource *cs)
190{
191 unsigned long flags;
192
193 spin_lock_irqsave(&watchdog_lock, flags);
194 if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
195 if (!list_empty(&cs->list) && list_empty(&cs->wd_list))
196 list_add(&cs->wd_list, &watchdog_list);
197 __clocksource_unstable(cs);
198 }
199 spin_unlock_irqrestore(&watchdog_lock, flags);
200}
201
202ulong max_cswd_read_retries = 3;
203module_param(max_cswd_read_retries, ulong, 0644);
204EXPORT_SYMBOL_GPL(max_cswd_read_retries);
205static int verify_n_cpus = 8;
206module_param(verify_n_cpus, int, 0644);
207
208static bool cs_watchdog_read(struct clocksource *cs, u64 *csnow, u64 *wdnow)
209{
210 unsigned int nretries;
211 u64 wd_end, wd_delta;
212 int64_t wd_delay;
213
214 for (nretries = 0; nretries <= max_cswd_read_retries; nretries++) {
215 local_irq_disable();
216 *wdnow = watchdog->read(watchdog);
217 *csnow = cs->read(cs);
218 wd_end = watchdog->read(watchdog);
219 local_irq_enable();
220
221 wd_delta = clocksource_delta(wd_end, *wdnow, watchdog->mask);
222 wd_delay = clocksource_cyc2ns(wd_delta, watchdog->mult,
223 watchdog->shift);
224 if (wd_delay <= WATCHDOG_MAX_SKEW) {
225 if (nretries > 1 || nretries >= max_cswd_read_retries) {
226 pr_warn("timekeeping watchdog on CPU%d: %s retried %d times before success\n",
227 smp_processor_id(), watchdog->name, nretries);
228 }
229 return true;
230 }
231 }
232
233 pr_warn("timekeeping watchdog on CPU%d: %s read-back delay of %lldns, attempt %d, marking unstable\n",
234 smp_processor_id(), watchdog->name, wd_delay, nretries);
235 return false;
236}
237
238static u64 csnow_mid;
239static cpumask_t cpus_ahead;
240static cpumask_t cpus_behind;
241static cpumask_t cpus_chosen;
242
243static void clocksource_verify_choose_cpus(void)
244{
245 int cpu, i, n = verify_n_cpus;
246
247 if (n < 0) {
248 /* Check all of the CPUs. */
249 cpumask_copy(&cpus_chosen, cpu_online_mask);
250 cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
251 return;
252 }
253
254 /* If no checking desired, or no other CPU to check, leave. */
255 cpumask_clear(&cpus_chosen);
256 if (n == 0 || num_online_cpus() <= 1)
257 return;
258
259 /* Make sure to select at least one CPU other than the current CPU. */
260 cpu = cpumask_next(-1, cpu_online_mask);
261 if (cpu == smp_processor_id())
262 cpu = cpumask_next(cpu, cpu_online_mask);
263 if (WARN_ON_ONCE(cpu >= nr_cpu_ids))
264 return;
265 cpumask_set_cpu(cpu, &cpus_chosen);
266
267 /* Force a sane value for the boot parameter. */
268 if (n > nr_cpu_ids)
269 n = nr_cpu_ids;
270
271 /*
272 * Randomly select the specified number of CPUs. If the same
273 * CPU is selected multiple times, that CPU is checked only once,
274 * and no replacement CPU is selected. This gracefully handles
275 * situations where verify_n_cpus is greater than the number of
276 * CPUs that are currently online.
277 */
278 for (i = 1; i < n; i++) {
279 cpu = prandom_u32() % nr_cpu_ids;
280 cpu = cpumask_next(cpu - 1, cpu_online_mask);
281 if (cpu >= nr_cpu_ids)
282 cpu = cpumask_next(-1, cpu_online_mask);
283 if (!WARN_ON_ONCE(cpu >= nr_cpu_ids))
284 cpumask_set_cpu(cpu, &cpus_chosen);
285 }
286
287 /* Don't verify ourselves. */
288 cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
289}
290
291static void clocksource_verify_one_cpu(void *csin)
292{
293 struct clocksource *cs = (struct clocksource *)csin;
294
295 csnow_mid = cs->read(cs);
296}
297
298void clocksource_verify_percpu(struct clocksource *cs)
299{
300 int64_t cs_nsec, cs_nsec_max = 0, cs_nsec_min = LLONG_MAX;
301 u64 csnow_begin, csnow_end;
302 int cpu, testcpu;
303 s64 delta;
304
305 if (verify_n_cpus == 0)
306 return;
307 cpumask_clear(&cpus_ahead);
308 cpumask_clear(&cpus_behind);
309 get_online_cpus();
310 preempt_disable();
311 clocksource_verify_choose_cpus();
312 if (cpumask_weight(&cpus_chosen) == 0) {
313 preempt_enable();
314 put_online_cpus();
315 pr_warn("Not enough CPUs to check clocksource '%s'.\n", cs->name);
316 return;
317 }
318 testcpu = smp_processor_id();
319 pr_warn("Checking clocksource %s synchronization from CPU %d to CPUs %*pbl.\n", cs->name, testcpu, cpumask_pr_args(&cpus_chosen));
320 for_each_cpu(cpu, &cpus_chosen) {
321 if (cpu == testcpu)
322 continue;
323 csnow_begin = cs->read(cs);
324 smp_call_function_single(cpu, clocksource_verify_one_cpu, cs, 1);
325 csnow_end = cs->read(cs);
326 delta = (s64)((csnow_mid - csnow_begin) & cs->mask);
327 if (delta < 0)
328 cpumask_set_cpu(cpu, &cpus_behind);
329 delta = (csnow_end - csnow_mid) & cs->mask;
330 if (delta < 0)
331 cpumask_set_cpu(cpu, &cpus_ahead);
332 delta = clocksource_delta(csnow_end, csnow_begin, cs->mask);
333 cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
334 if (cs_nsec > cs_nsec_max)
335 cs_nsec_max = cs_nsec;
336 if (cs_nsec < cs_nsec_min)
337 cs_nsec_min = cs_nsec;
338 }
339 preempt_enable();
340 put_online_cpus();
341 if (!cpumask_empty(&cpus_ahead))
342 pr_warn(" CPUs %*pbl ahead of CPU %d for clocksource %s.\n",
343 cpumask_pr_args(&cpus_ahead), testcpu, cs->name);
344 if (!cpumask_empty(&cpus_behind))
345 pr_warn(" CPUs %*pbl behind CPU %d for clocksource %s.\n",
346 cpumask_pr_args(&cpus_behind), testcpu, cs->name);
347 if (!cpumask_empty(&cpus_ahead) || !cpumask_empty(&cpus_behind))
348 pr_warn(" CPU %d check durations %lldns - %lldns for clocksource %s.\n",
349 testcpu, cs_nsec_min, cs_nsec_max, cs->name);
350}
351EXPORT_SYMBOL_GPL(clocksource_verify_percpu);
352
353static void clocksource_watchdog(struct timer_list *unused)
354{
355 u64 csnow, wdnow, cslast, wdlast, delta;
356 int next_cpu, reset_pending;
357 int64_t wd_nsec, cs_nsec;
358 struct clocksource *cs;
359 u32 md;
360
361 spin_lock(&watchdog_lock);
362 if (!watchdog_running)
363 goto out;
364
365 reset_pending = atomic_read(&watchdog_reset_pending);
366
367 list_for_each_entry(cs, &watchdog_list, wd_list) {
368
369 /* Clocksource already marked unstable? */
370 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
371 if (finished_booting)
372 schedule_work(&watchdog_work);
373 continue;
374 }
375
376 if (!cs_watchdog_read(cs, &csnow, &wdnow)) {
377 /* Clock readout unreliable, so give it up. */
378 __clocksource_unstable(cs);
379 continue;
380 }
381
382 /* Clocksource initialized ? */
383 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
384 atomic_read(&watchdog_reset_pending)) {
385 cs->flags |= CLOCK_SOURCE_WATCHDOG;
386 cs->wd_last = wdnow;
387 cs->cs_last = csnow;
388 continue;
389 }
390
391 delta = clocksource_delta(wdnow, cs->wd_last, watchdog->mask);
392 wd_nsec = clocksource_cyc2ns(delta, watchdog->mult,
393 watchdog->shift);
394
395 delta = clocksource_delta(csnow, cs->cs_last, cs->mask);
396 cs_nsec = clocksource_cyc2ns(delta, cs->mult, cs->shift);
397 wdlast = cs->wd_last; /* save these in case we print them */
398 cslast = cs->cs_last;
399 cs->cs_last = csnow;
400 cs->wd_last = wdnow;
401
402 if (atomic_read(&watchdog_reset_pending))
403 continue;
404
405 /* Check the deviation from the watchdog clocksource. */
406 md = cs->uncertainty_margin + watchdog->uncertainty_margin;
407 if (abs(cs_nsec - wd_nsec) > md) {
408 pr_warn("timekeeping watchdog on CPU%d: Marking clocksource '%s' as unstable because the skew is too large:\n",
409 smp_processor_id(), cs->name);
410 pr_warn(" '%s' wd_nsec: %lld wd_now: %llx wd_last: %llx mask: %llx\n",
411 watchdog->name, wd_nsec, wdnow, wdlast, watchdog->mask);
412 pr_warn(" '%s' cs_nsec: %lld cs_now: %llx cs_last: %llx mask: %llx\n",
413 cs->name, cs_nsec, csnow, cslast, cs->mask);
414 if (curr_clocksource == cs)
415 pr_warn(" '%s' is current clocksource.\n", cs->name);
416 else if (curr_clocksource)
417 pr_warn(" '%s' (not '%s') is current clocksource.\n", curr_clocksource->name, cs->name);
418 else
419 pr_warn(" No current clocksource.\n");
420 __clocksource_unstable(cs);
421 continue;
422 }
423
424 if (cs == curr_clocksource && cs->tick_stable)
425 cs->tick_stable(cs);
426
427 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
428 (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
429 (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
430 /* Mark it valid for high-res. */
431 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
432
433 /*
434 * clocksource_done_booting() will sort it if
435 * finished_booting is not set yet.
436 */
437 if (!finished_booting)
438 continue;
439
440 /*
441 * If this is not the current clocksource let
442 * the watchdog thread reselect it. Due to the
443 * change to high res this clocksource might
444 * be preferred now. If it is the current
445 * clocksource let the tick code know about
446 * that change.
447 */
448 if (cs != curr_clocksource) {
449 cs->flags |= CLOCK_SOURCE_RESELECT;
450 schedule_work(&watchdog_work);
451 } else {
452 tick_clock_notify();
453 }
454 }
455 }
456
457 /*
458 * We only clear the watchdog_reset_pending, when we did a
459 * full cycle through all clocksources.
460 */
461 if (reset_pending)
462 atomic_dec(&watchdog_reset_pending);
463
464 /*
465 * Cycle through CPUs to check if the CPUs stay synchronized
466 * to each other.
467 */
468 next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
469 if (next_cpu >= nr_cpu_ids)
470 next_cpu = cpumask_first(cpu_online_mask);
471
472 /*
473 * Arm timer if not already pending: could race with concurrent
474 * pair clocksource_stop_watchdog() clocksource_start_watchdog().
475 */
476 if (!timer_pending(&watchdog_timer)) {
477 watchdog_timer.expires += WATCHDOG_INTERVAL;
478 add_timer_on(&watchdog_timer, next_cpu);
479 }
480out:
481 spin_unlock(&watchdog_lock);
482}
483
484static inline void clocksource_start_watchdog(void)
485{
486 if (watchdog_running || !watchdog || list_empty(&watchdog_list))
487 return;
488 timer_setup(&watchdog_timer, clocksource_watchdog, 0);
489 watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
490 add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
491 watchdog_running = 1;
492}
493
494static inline void clocksource_stop_watchdog(void)
495{
496 if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
497 return;
498 del_timer(&watchdog_timer);
499 watchdog_running = 0;
500}
501
502static inline void clocksource_reset_watchdog(void)
503{
504 struct clocksource *cs;
505
506 list_for_each_entry(cs, &watchdog_list, wd_list)
507 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
508}
509
510static void clocksource_resume_watchdog(void)
511{
512 atomic_inc(&watchdog_reset_pending);
513}
514
515static void clocksource_enqueue_watchdog(struct clocksource *cs)
516{
517 INIT_LIST_HEAD(&cs->wd_list);
518
519 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
520 /* cs is a clocksource to be watched. */
521 list_add(&cs->wd_list, &watchdog_list);
522 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
523 } else {
524 /* cs is a watchdog. */
525 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
526 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
527 }
528}
529
530static void clocksource_select_watchdog(bool fallback)
531{
532 struct clocksource *cs, *old_wd;
533 unsigned long flags;
534
535 spin_lock_irqsave(&watchdog_lock, flags);
536 /* save current watchdog */
537 old_wd = watchdog;
538 if (fallback)
539 watchdog = NULL;
540
541 list_for_each_entry(cs, &clocksource_list, list) {
542 /* cs is a clocksource to be watched. */
543 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
544 continue;
545
546 /* Skip current if we were requested for a fallback. */
547 if (fallback && cs == old_wd)
548 continue;
549
550 /* Pick the best watchdog. */
551 if (!watchdog || cs->rating > watchdog->rating)
552 watchdog = cs;
553 }
554 /* If we failed to find a fallback restore the old one. */
555 if (!watchdog)
556 watchdog = old_wd;
557
558 /* If we changed the watchdog we need to reset cycles. */
559 if (watchdog != old_wd)
560 clocksource_reset_watchdog();
561
562 /* Check if the watchdog timer needs to be started. */
563 clocksource_start_watchdog();
564 spin_unlock_irqrestore(&watchdog_lock, flags);
565}
566
567static void clocksource_dequeue_watchdog(struct clocksource *cs)
568{
569 if (cs != watchdog) {
570 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
571 /* cs is a watched clocksource. */
572 list_del_init(&cs->wd_list);
573 /* Check if the watchdog timer needs to be stopped. */
574 clocksource_stop_watchdog();
575 }
576 }
577}
578
579static int __clocksource_watchdog_kthread(void)
580{
581 struct clocksource *cs, *tmp;
582 unsigned long flags;
583 int select = 0;
584
585 /* Do any required per-CPU skew verification. */
586 if (curr_clocksource &&
587 curr_clocksource->flags & CLOCK_SOURCE_UNSTABLE &&
588 curr_clocksource->flags & CLOCK_SOURCE_VERIFY_PERCPU)
589 clocksource_verify_percpu(curr_clocksource);
590
591 spin_lock_irqsave(&watchdog_lock, flags);
592 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
593 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
594 list_del_init(&cs->wd_list);
595 __clocksource_change_rating(cs, 0);
596 select = 1;
597 }
598 if (cs->flags & CLOCK_SOURCE_RESELECT) {
599 cs->flags &= ~CLOCK_SOURCE_RESELECT;
600 select = 1;
601 }
602 }
603 /* Check if the watchdog timer needs to be stopped. */
604 clocksource_stop_watchdog();
605 spin_unlock_irqrestore(&watchdog_lock, flags);
606
607 return select;
608}
609
610static int clocksource_watchdog_kthread(void *data)
611{
612 mutex_lock(&clocksource_mutex);
613 if (__clocksource_watchdog_kthread())
614 clocksource_select();
615 mutex_unlock(&clocksource_mutex);
616 return 0;
617}
618
619static bool clocksource_is_watchdog(struct clocksource *cs)
620{
621 return cs == watchdog;
622}
623
624#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
625
626static void clocksource_enqueue_watchdog(struct clocksource *cs)
627{
628 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
629 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
630}
631
632static void clocksource_select_watchdog(bool fallback) { }
633static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
634static inline void clocksource_resume_watchdog(void) { }
635static inline int __clocksource_watchdog_kthread(void) { return 0; }
636static bool clocksource_is_watchdog(struct clocksource *cs) { return false; }
637void clocksource_mark_unstable(struct clocksource *cs) { }
638
639static inline void clocksource_watchdog_lock(unsigned long *flags) { }
640static inline void clocksource_watchdog_unlock(unsigned long *flags) { }
641
642#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
643
644static bool clocksource_is_suspend(struct clocksource *cs)
645{
646 return cs == suspend_clocksource;
647}
648
649static void __clocksource_suspend_select(struct clocksource *cs)
650{
651 /*
652 * Skip the clocksource which will be stopped in suspend state.
653 */
654 if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
655 return;
656
657 /*
658 * The nonstop clocksource can be selected as the suspend clocksource to
659 * calculate the suspend time, so it should not supply suspend/resume
660 * interfaces to suspend the nonstop clocksource when system suspends.
661 */
662 if (cs->suspend || cs->resume) {
663 pr_warn("Nonstop clocksource %s should not supply suspend/resume interfaces\n",
664 cs->name);
665 }
666
667 /* Pick the best rating. */
668 if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
669 suspend_clocksource = cs;
670}
671
672/**
673 * clocksource_suspend_select - Select the best clocksource for suspend timing
674 * @fallback: if select a fallback clocksource
675 */
676static void clocksource_suspend_select(bool fallback)
677{
678 struct clocksource *cs, *old_suspend;
679
680 old_suspend = suspend_clocksource;
681 if (fallback)
682 suspend_clocksource = NULL;
683
684 list_for_each_entry(cs, &clocksource_list, list) {
685 /* Skip current if we were requested for a fallback. */
686 if (fallback && cs == old_suspend)
687 continue;
688
689 __clocksource_suspend_select(cs);
690 }
691}
692
693/**
694 * clocksource_start_suspend_timing - Start measuring the suspend timing
695 * @cs: current clocksource from timekeeping
696 * @start_cycles: current cycles from timekeeping
697 *
698 * This function will save the start cycle values of suspend timer to calculate
699 * the suspend time when resuming system.
700 *
701 * This function is called late in the suspend process from timekeeping_suspend(),
702 * that means processes are frozen, non-boot cpus and interrupts are disabled
703 * now. It is therefore possible to start the suspend timer without taking the
704 * clocksource mutex.
705 */
706void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles)
707{
708 if (!suspend_clocksource)
709 return;
710
711 /*
712 * If current clocksource is the suspend timer, we should use the
713 * tkr_mono.cycle_last value as suspend_start to avoid same reading
714 * from suspend timer.
715 */
716 if (clocksource_is_suspend(cs)) {
717 suspend_start = start_cycles;
718 return;
719 }
720
721 if (suspend_clocksource->enable &&
722 suspend_clocksource->enable(suspend_clocksource)) {
723 pr_warn_once("Failed to enable the non-suspend-able clocksource.\n");
724 return;
725 }
726
727 suspend_start = suspend_clocksource->read(suspend_clocksource);
728}
729
730/**
731 * clocksource_stop_suspend_timing - Stop measuring the suspend timing
732 * @cs: current clocksource from timekeeping
733 * @cycle_now: current cycles from timekeeping
734 *
735 * This function will calculate the suspend time from suspend timer.
736 *
737 * Returns nanoseconds since suspend started, 0 if no usable suspend clocksource.
738 *
739 * This function is called early in the resume process from timekeeping_resume(),
740 * that means there is only one cpu, no processes are running and the interrupts
741 * are disabled. It is therefore possible to stop the suspend timer without
742 * taking the clocksource mutex.
743 */
744u64 clocksource_stop_suspend_timing(struct clocksource *cs, u64 cycle_now)
745{
746 u64 now, delta, nsec = 0;
747
748 if (!suspend_clocksource)
749 return 0;
750
751 /*
752 * If current clocksource is the suspend timer, we should use the
753 * tkr_mono.cycle_last value from timekeeping as current cycle to
754 * avoid same reading from suspend timer.
755 */
756 if (clocksource_is_suspend(cs))
757 now = cycle_now;
758 else
759 now = suspend_clocksource->read(suspend_clocksource);
760
761 if (now > suspend_start) {
762 delta = clocksource_delta(now, suspend_start,
763 suspend_clocksource->mask);
764 nsec = mul_u64_u32_shr(delta, suspend_clocksource->mult,
765 suspend_clocksource->shift);
766 }
767
768 /*
769 * Disable the suspend timer to save power if current clocksource is
770 * not the suspend timer.
771 */
772 if (!clocksource_is_suspend(cs) && suspend_clocksource->disable)
773 suspend_clocksource->disable(suspend_clocksource);
774
775 return nsec;
776}
777
778/**
779 * clocksource_suspend - suspend the clocksource(s)
780 */
781void clocksource_suspend(void)
782{
783 struct clocksource *cs;
784
785 list_for_each_entry_reverse(cs, &clocksource_list, list)
786 if (cs->suspend)
787 cs->suspend(cs);
788}
789
790/**
791 * clocksource_resume - resume the clocksource(s)
792 */
793void clocksource_resume(void)
794{
795 struct clocksource *cs;
796
797 list_for_each_entry(cs, &clocksource_list, list)
798 if (cs->resume)
799 cs->resume(cs);
800
801 clocksource_resume_watchdog();
802}
803
804/**
805 * clocksource_touch_watchdog - Update watchdog
806 *
807 * Update the watchdog after exception contexts such as kgdb so as not
808 * to incorrectly trip the watchdog. This might fail when the kernel
809 * was stopped in code which holds watchdog_lock.
810 */
811void clocksource_touch_watchdog(void)
812{
813 clocksource_resume_watchdog();
814}
815
816/**
817 * clocksource_max_adjustment- Returns max adjustment amount
818 * @cs: Pointer to clocksource
819 *
820 */
821static u32 clocksource_max_adjustment(struct clocksource *cs)
822{
823 u64 ret;
824 /*
825 * We won't try to correct for more than 11% adjustments (110,000 ppm),
826 */
827 ret = (u64)cs->mult * 11;
828 do_div(ret,100);
829 return (u32)ret;
830}
831
832/**
833 * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
834 * @mult: cycle to nanosecond multiplier
835 * @shift: cycle to nanosecond divisor (power of two)
836 * @maxadj: maximum adjustment value to mult (~11%)
837 * @mask: bitmask for two's complement subtraction of non 64 bit counters
838 * @max_cyc: maximum cycle value before potential overflow (does not include
839 * any safety margin)
840 *
841 * NOTE: This function includes a safety margin of 50%, in other words, we
842 * return half the number of nanoseconds the hardware counter can technically
843 * cover. This is done so that we can potentially detect problems caused by
844 * delayed timers or bad hardware, which might result in time intervals that
845 * are larger than what the math used can handle without overflows.
846 */
847u64 clocks_calc_max_nsecs(u32 mult, u32 shift, u32 maxadj, u64 mask, u64 *max_cyc)
848{
849 u64 max_nsecs, max_cycles;
850
851 /*
852 * Calculate the maximum number of cycles that we can pass to the
853 * cyc2ns() function without overflowing a 64-bit result.
854 */
855 max_cycles = ULLONG_MAX;
856 do_div(max_cycles, mult+maxadj);
857
858 /*
859 * The actual maximum number of cycles we can defer the clocksource is
860 * determined by the minimum of max_cycles and mask.
861 * Note: Here we subtract the maxadj to make sure we don't sleep for
862 * too long if there's a large negative adjustment.
863 */
864 max_cycles = min(max_cycles, mask);
865 max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
866
867 /* return the max_cycles value as well if requested */
868 if (max_cyc)
869 *max_cyc = max_cycles;
870
871 /* Return 50% of the actual maximum, so we can detect bad values */
872 max_nsecs >>= 1;
873
874 return max_nsecs;
875}
876
877/**
878 * clocksource_update_max_deferment - Updates the clocksource max_idle_ns & max_cycles
879 * @cs: Pointer to clocksource to be updated
880 *
881 */
882static inline void clocksource_update_max_deferment(struct clocksource *cs)
883{
884 cs->max_idle_ns = clocks_calc_max_nsecs(cs->mult, cs->shift,
885 cs->maxadj, cs->mask,
886 &cs->max_cycles);
887}
888
889static struct clocksource *clocksource_find_best(bool oneshot, bool skipcur)
890{
891 struct clocksource *cs;
892
893 if (!finished_booting || list_empty(&clocksource_list))
894 return NULL;
895
896 /*
897 * We pick the clocksource with the highest rating. If oneshot
898 * mode is active, we pick the highres valid clocksource with
899 * the best rating.
900 */
901 list_for_each_entry(cs, &clocksource_list, list) {
902 if (skipcur && cs == curr_clocksource)
903 continue;
904 if (oneshot && !(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES))
905 continue;
906 return cs;
907 }
908 return NULL;
909}
910
911static void __clocksource_select(bool skipcur)
912{
913 bool oneshot = tick_oneshot_mode_active();
914 struct clocksource *best, *cs;
915
916 /* Find the best suitable clocksource */
917 best = clocksource_find_best(oneshot, skipcur);
918 if (!best)
919 return;
920
921 if (!strlen(override_name))
922 goto found;
923
924 /* Check for the override clocksource. */
925 list_for_each_entry(cs, &clocksource_list, list) {
926 if (skipcur && cs == curr_clocksource)
927 continue;
928 if (strcmp(cs->name, override_name) != 0)
929 continue;
930 /*
931 * Check to make sure we don't switch to a non-highres
932 * capable clocksource if the tick code is in oneshot
933 * mode (highres or nohz)
934 */
935 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
936 /* Override clocksource cannot be used. */
937 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
938 pr_warn("Override clocksource %s is unstable and not HRT compatible - cannot switch while in HRT/NOHZ mode\n",
939 cs->name);
940 override_name[0] = 0;
941 } else {
942 /*
943 * The override cannot be currently verified.
944 * Deferring to let the watchdog check.
945 */
946 pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
947 cs->name);
948 }
949 } else
950 /* Override clocksource can be used. */
951 best = cs;
952 break;
953 }
954
955found:
956 if (curr_clocksource != best && !timekeeping_notify(best)) {
957 pr_info("Switched to clocksource %s\n", best->name);
958 curr_clocksource = best;
959 }
960}
961
962/**
963 * clocksource_select - Select the best clocksource available
964 *
965 * Private function. Must hold clocksource_mutex when called.
966 *
967 * Select the clocksource with the best rating, or the clocksource,
968 * which is selected by userspace override.
969 */
970static void clocksource_select(void)
971{
972 __clocksource_select(false);
973}
974
975static void clocksource_select_fallback(void)
976{
977 __clocksource_select(true);
978}
979
980/*
981 * clocksource_done_booting - Called near the end of core bootup
982 *
983 * Hack to avoid lots of clocksource churn at boot time.
984 * We use fs_initcall because we want this to start before
985 * device_initcall but after subsys_initcall.
986 */
987static int __init clocksource_done_booting(void)
988{
989 mutex_lock(&clocksource_mutex);
990 curr_clocksource = clocksource_default_clock();
991 finished_booting = 1;
992 /*
993 * Run the watchdog first to eliminate unstable clock sources
994 */
995 __clocksource_watchdog_kthread();
996 clocksource_select();
997 mutex_unlock(&clocksource_mutex);
998 return 0;
999}
1000fs_initcall(clocksource_done_booting);
1001
1002/*
1003 * Enqueue the clocksource sorted by rating
1004 */
1005static void clocksource_enqueue(struct clocksource *cs)
1006{
1007 struct list_head *entry = &clocksource_list;
1008 struct clocksource *tmp;
1009
1010 list_for_each_entry(tmp, &clocksource_list, list) {
1011 /* Keep track of the place, where to insert */
1012 if (tmp->rating < cs->rating)
1013 break;
1014 entry = &tmp->list;
1015 }
1016 list_add(&cs->list, entry);
1017}
1018
1019/**
1020 * __clocksource_update_freq_scale - Used update clocksource with new freq
1021 * @cs: clocksource to be registered
1022 * @scale: Scale factor multiplied against freq to get clocksource hz
1023 * @freq: clocksource frequency (cycles per second) divided by scale
1024 *
1025 * This should only be called from the clocksource->enable() method.
1026 *
1027 * This *SHOULD NOT* be called directly! Please use the
1028 * __clocksource_update_freq_hz() or __clocksource_update_freq_khz() helper
1029 * functions.
1030 */
1031void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq)
1032{
1033 u64 sec;
1034
1035 /*
1036 * Default clocksources are *special* and self-define their mult/shift.
1037 * But, you're not special, so you should specify a freq value.
1038 */
1039 if (freq) {
1040 /*
1041 * Calc the maximum number of seconds which we can run before
1042 * wrapping around. For clocksources which have a mask > 32-bit
1043 * we need to limit the max sleep time to have a good
1044 * conversion precision. 10 minutes is still a reasonable
1045 * amount. That results in a shift value of 24 for a
1046 * clocksource with mask >= 40-bit and f >= 4GHz. That maps to
1047 * ~ 0.06ppm granularity for NTP.
1048 */
1049 sec = cs->mask;
1050 do_div(sec, freq);
1051 do_div(sec, scale);
1052 if (!sec)
1053 sec = 1;
1054 else if (sec > 600 && cs->mask > UINT_MAX)
1055 sec = 600;
1056
1057 clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
1058 NSEC_PER_SEC / scale, sec * scale);
1059 }
1060
1061 /*
1062 * If the uncertainty margin is not specified, calculate it.
1063 * If both scale and freq are non-zero, calculate the clock
1064 * period, but bound below at 2*WATCHDOG_MAX_SKEW. However,
1065 * if either of scale or freq is zero, be very conservative and
1066 * take the tens-of-milliseconds WATCHDOG_THRESHOLD value for the
1067 * uncertainty margin. Allow stupidly small uncertainty margins
1068 * to be specified by the caller for testing purposes, but warn
1069 * to discourage production use of this capability.
1070 */
1071 if (scale && freq && !cs->uncertainty_margin) {
1072 cs->uncertainty_margin = NSEC_PER_SEC / (scale * freq);
1073 if (cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW)
1074 cs->uncertainty_margin = 2 * WATCHDOG_MAX_SKEW;
1075 } else if (!cs->uncertainty_margin) {
1076 cs->uncertainty_margin = WATCHDOG_THRESHOLD;
1077 }
1078 WARN_ON_ONCE(cs->uncertainty_margin < 2 * WATCHDOG_MAX_SKEW);
1079
1080 /*
1081 * Ensure clocksources that have large 'mult' values don't overflow
1082 * when adjusted.
1083 */
1084 cs->maxadj = clocksource_max_adjustment(cs);
1085 while (freq && ((cs->mult + cs->maxadj < cs->mult)
1086 || (cs->mult - cs->maxadj > cs->mult))) {
1087 cs->mult >>= 1;
1088 cs->shift--;
1089 cs->maxadj = clocksource_max_adjustment(cs);
1090 }
1091
1092 /*
1093 * Only warn for *special* clocksources that self-define
1094 * their mult/shift values and don't specify a freq.
1095 */
1096 WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
1097 "timekeeping: Clocksource %s might overflow on 11%% adjustment\n",
1098 cs->name);
1099
1100 clocksource_update_max_deferment(cs);
1101
1102 pr_info("%s: mask: 0x%llx max_cycles: 0x%llx, max_idle_ns: %lld ns\n",
1103 cs->name, cs->mask, cs->max_cycles, cs->max_idle_ns);
1104}
1105EXPORT_SYMBOL_GPL(__clocksource_update_freq_scale);
1106
1107/**
1108 * __clocksource_register_scale - Used to install new clocksources
1109 * @cs: clocksource to be registered
1110 * @scale: Scale factor multiplied against freq to get clocksource hz
1111 * @freq: clocksource frequency (cycles per second) divided by scale
1112 *
1113 * Returns -EBUSY if registration fails, zero otherwise.
1114 *
1115 * This *SHOULD NOT* be called directly! Please use the
1116 * clocksource_register_hz() or clocksource_register_khz helper functions.
1117 */
1118int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
1119{
1120 unsigned long flags;
1121
1122 clocksource_arch_init(cs);
1123
1124 if (WARN_ON_ONCE((unsigned int)cs->id >= CSID_MAX))
1125 cs->id = CSID_GENERIC;
1126 if (cs->vdso_clock_mode < 0 ||
1127 cs->vdso_clock_mode >= VDSO_CLOCKMODE_MAX) {
1128 pr_warn("clocksource %s registered with invalid VDSO mode %d. Disabling VDSO support.\n",
1129 cs->name, cs->vdso_clock_mode);
1130 cs->vdso_clock_mode = VDSO_CLOCKMODE_NONE;
1131 }
1132
1133 /* Initialize mult/shift and max_idle_ns */
1134 __clocksource_update_freq_scale(cs, scale, freq);
1135
1136 /* Add clocksource to the clocksource list */
1137 mutex_lock(&clocksource_mutex);
1138
1139 clocksource_watchdog_lock(&flags);
1140 clocksource_enqueue(cs);
1141 clocksource_enqueue_watchdog(cs);
1142 clocksource_watchdog_unlock(&flags);
1143
1144 clocksource_select();
1145 clocksource_select_watchdog(false);
1146 __clocksource_suspend_select(cs);
1147 mutex_unlock(&clocksource_mutex);
1148 return 0;
1149}
1150EXPORT_SYMBOL_GPL(__clocksource_register_scale);
1151
1152static void __clocksource_change_rating(struct clocksource *cs, int rating)
1153{
1154 list_del(&cs->list);
1155 cs->rating = rating;
1156 clocksource_enqueue(cs);
1157}
1158
1159/**
1160 * clocksource_change_rating - Change the rating of a registered clocksource
1161 * @cs: clocksource to be changed
1162 * @rating: new rating
1163 */
1164void clocksource_change_rating(struct clocksource *cs, int rating)
1165{
1166 unsigned long flags;
1167
1168 mutex_lock(&clocksource_mutex);
1169 clocksource_watchdog_lock(&flags);
1170 __clocksource_change_rating(cs, rating);
1171 clocksource_watchdog_unlock(&flags);
1172
1173 clocksource_select();
1174 clocksource_select_watchdog(false);
1175 clocksource_suspend_select(false);
1176 mutex_unlock(&clocksource_mutex);
1177}
1178EXPORT_SYMBOL(clocksource_change_rating);
1179
1180/*
1181 * Unbind clocksource @cs. Called with clocksource_mutex held
1182 */
1183static int clocksource_unbind(struct clocksource *cs)
1184{
1185 unsigned long flags;
1186
1187 if (clocksource_is_watchdog(cs)) {
1188 /* Select and try to install a replacement watchdog. */
1189 clocksource_select_watchdog(true);
1190 if (clocksource_is_watchdog(cs))
1191 return -EBUSY;
1192 }
1193
1194 if (cs == curr_clocksource) {
1195 /* Select and try to install a replacement clock source */
1196 clocksource_select_fallback();
1197 if (curr_clocksource == cs)
1198 return -EBUSY;
1199 }
1200
1201 if (clocksource_is_suspend(cs)) {
1202 /*
1203 * Select and try to install a replacement suspend clocksource.
1204 * If no replacement suspend clocksource, we will just let the
1205 * clocksource go and have no suspend clocksource.
1206 */
1207 clocksource_suspend_select(true);
1208 }
1209
1210 clocksource_watchdog_lock(&flags);
1211 clocksource_dequeue_watchdog(cs);
1212 list_del_init(&cs->list);
1213 clocksource_watchdog_unlock(&flags);
1214
1215 return 0;
1216}
1217
1218/**
1219 * clocksource_unregister - remove a registered clocksource
1220 * @cs: clocksource to be unregistered
1221 */
1222int clocksource_unregister(struct clocksource *cs)
1223{
1224 int ret = 0;
1225
1226 mutex_lock(&clocksource_mutex);
1227 if (!list_empty(&cs->list))
1228 ret = clocksource_unbind(cs);
1229 mutex_unlock(&clocksource_mutex);
1230 return ret;
1231}
1232EXPORT_SYMBOL(clocksource_unregister);
1233
1234#ifdef CONFIG_SYSFS
1235/**
1236 * current_clocksource_show - sysfs interface for current clocksource
1237 * @dev: unused
1238 * @attr: unused
1239 * @buf: char buffer to be filled with clocksource list
1240 *
1241 * Provides sysfs interface for listing current clocksource.
1242 */
1243static ssize_t current_clocksource_show(struct device *dev,
1244 struct device_attribute *attr,
1245 char *buf)
1246{
1247 ssize_t count = 0;
1248
1249 mutex_lock(&clocksource_mutex);
1250 count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
1251 mutex_unlock(&clocksource_mutex);
1252
1253 return count;
1254}
1255
1256ssize_t sysfs_get_uname(const char *buf, char *dst, size_t cnt)
1257{
1258 size_t ret = cnt;
1259
1260 /* strings from sysfs write are not 0 terminated! */
1261 if (!cnt || cnt >= CS_NAME_LEN)
1262 return -EINVAL;
1263
1264 /* strip of \n: */
1265 if (buf[cnt-1] == '\n')
1266 cnt--;
1267 if (cnt > 0)
1268 memcpy(dst, buf, cnt);
1269 dst[cnt] = 0;
1270 return ret;
1271}
1272
1273/**
1274 * current_clocksource_store - interface for manually overriding clocksource
1275 * @dev: unused
1276 * @attr: unused
1277 * @buf: name of override clocksource
1278 * @count: length of buffer
1279 *
1280 * Takes input from sysfs interface for manually overriding the default
1281 * clocksource selection.
1282 */
1283static ssize_t current_clocksource_store(struct device *dev,
1284 struct device_attribute *attr,
1285 const char *buf, size_t count)
1286{
1287 ssize_t ret;
1288
1289 mutex_lock(&clocksource_mutex);
1290
1291 ret = sysfs_get_uname(buf, override_name, count);
1292 if (ret >= 0)
1293 clocksource_select();
1294
1295 mutex_unlock(&clocksource_mutex);
1296
1297 return ret;
1298}
1299static DEVICE_ATTR_RW(current_clocksource);
1300
1301/**
1302 * unbind_clocksource_store - interface for manually unbinding clocksource
1303 * @dev: unused
1304 * @attr: unused
1305 * @buf: unused
1306 * @count: length of buffer
1307 *
1308 * Takes input from sysfs interface for manually unbinding a clocksource.
1309 */
1310static ssize_t unbind_clocksource_store(struct device *dev,
1311 struct device_attribute *attr,
1312 const char *buf, size_t count)
1313{
1314 struct clocksource *cs;
1315 char name[CS_NAME_LEN];
1316 ssize_t ret;
1317
1318 ret = sysfs_get_uname(buf, name, count);
1319 if (ret < 0)
1320 return ret;
1321
1322 ret = -ENODEV;
1323 mutex_lock(&clocksource_mutex);
1324 list_for_each_entry(cs, &clocksource_list, list) {
1325 if (strcmp(cs->name, name))
1326 continue;
1327 ret = clocksource_unbind(cs);
1328 break;
1329 }
1330 mutex_unlock(&clocksource_mutex);
1331
1332 return ret ? ret : count;
1333}
1334static DEVICE_ATTR_WO(unbind_clocksource);
1335
1336/**
1337 * available_clocksource_show - sysfs interface for listing clocksource
1338 * @dev: unused
1339 * @attr: unused
1340 * @buf: char buffer to be filled with clocksource list
1341 *
1342 * Provides sysfs interface for listing registered clocksources
1343 */
1344static ssize_t available_clocksource_show(struct device *dev,
1345 struct device_attribute *attr,
1346 char *buf)
1347{
1348 struct clocksource *src;
1349 ssize_t count = 0;
1350
1351 mutex_lock(&clocksource_mutex);
1352 list_for_each_entry(src, &clocksource_list, list) {
1353 /*
1354 * Don't show non-HRES clocksource if the tick code is
1355 * in one shot mode (highres=on or nohz=on)
1356 */
1357 if (!tick_oneshot_mode_active() ||
1358 (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
1359 count += snprintf(buf + count,
1360 max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
1361 "%s ", src->name);
1362 }
1363 mutex_unlock(&clocksource_mutex);
1364
1365 count += snprintf(buf + count,
1366 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
1367
1368 return count;
1369}
1370static DEVICE_ATTR_RO(available_clocksource);
1371
1372static struct attribute *clocksource_attrs[] = {
1373 &dev_attr_current_clocksource.attr,
1374 &dev_attr_unbind_clocksource.attr,
1375 &dev_attr_available_clocksource.attr,
1376 NULL
1377};
1378ATTRIBUTE_GROUPS(clocksource);
1379
1380static struct bus_type clocksource_subsys = {
1381 .name = "clocksource",
1382 .dev_name = "clocksource",
1383};
1384
1385static struct device device_clocksource = {
1386 .id = 0,
1387 .bus = &clocksource_subsys,
1388 .groups = clocksource_groups,
1389};
1390
1391static int __init init_clocksource_sysfs(void)
1392{
1393 int error = subsys_system_register(&clocksource_subsys, NULL);
1394
1395 if (!error)
1396 error = device_register(&device_clocksource);
1397
1398 return error;
1399}
1400
1401device_initcall(init_clocksource_sysfs);
1402#endif /* CONFIG_SYSFS */
1403
1404/**
1405 * boot_override_clocksource - boot clock override
1406 * @str: override name
1407 *
1408 * Takes a clocksource= boot argument and uses it
1409 * as the clocksource override name.
1410 */
1411static int __init boot_override_clocksource(char* str)
1412{
1413 mutex_lock(&clocksource_mutex);
1414 if (str)
1415 strlcpy(override_name, str, sizeof(override_name));
1416 mutex_unlock(&clocksource_mutex);
1417 return 1;
1418}
1419
1420__setup("clocksource=", boot_override_clocksource);
1421
1422/**
1423 * boot_override_clock - Compatibility layer for deprecated boot option
1424 * @str: override name
1425 *
1426 * DEPRECATED! Takes a clock= boot argument and uses it
1427 * as the clocksource override name
1428 */
1429static int __init boot_override_clock(char* str)
1430{
1431 if (!strcmp(str, "pmtmr")) {
1432 pr_warn("clock=pmtmr is deprecated - use clocksource=acpi_pm\n");
1433 return boot_override_clocksource("acpi_pm");
1434 }
1435 pr_warn("clock= boot option is deprecated - use clocksource=xyz\n");
1436 return boot_override_clocksource(str);
1437}
1438
1439__setup("clock=", boot_override_clock);