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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>
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
25
26
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29
30
31
32
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40
41
42
43
44
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
54
55
56 tmp = ((u64)maxsec * from) >> 32;
57 while (tmp) {
58 tmp >>=1;
59 sftacc--;
60 }
61
62
63
64
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
79
80
81
82
83
84
85
86
87
88
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
100
101
102#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 5)
103
104
105
106
107
108
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
139
140#define WATCHDOG_INTERVAL (HZ >> 1)
141
142static void clocksource_watchdog_work(struct work_struct *work)
143{
144
145
146
147
148
149
150
151
152
153
154
155
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
167
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
178 if (finished_booting)
179 schedule_work(&watchdog_work);
180}
181
182
183
184
185
186
187
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
249 cpumask_copy(&cpus_chosen, cpu_online_mask);
250 cpumask_clear_cpu(smp_processor_id(), &cpus_chosen);
251 return;
252 }
253
254
255 cpumask_clear(&cpus_chosen);
256 if (n == 0 || num_online_cpus() <= 1)
257 return;
258
259
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
268 if (n > nr_cpu_ids)
269 n = nr_cpu_ids;
270
271
272
273
274
275
276
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
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 cpus_read_lock();
310 preempt_disable();
311 clocksource_verify_choose_cpus();
312 if (cpumask_weight(&cpus_chosen) == 0) {
313 preempt_enable();
314 cpus_read_unlock();
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 cpus_read_unlock();
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
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
378 __clocksource_unstable(cs);
379 continue;
380 }
381
382
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;
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
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
431 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
432
433
434
435
436
437 if (!finished_booting)
438 continue;
439
440
441
442
443
444
445
446
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
459
460
461 if (reset_pending)
462 atomic_dec(&watchdog_reset_pending);
463
464
465
466
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
474
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
521 list_add(&cs->wd_list, &watchdog_list);
522 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
523 } else {
524
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
537 old_wd = watchdog;
538 if (fallback)
539 watchdog = NULL;
540
541 list_for_each_entry(cs, &clocksource_list, list) {
542
543 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY)
544 continue;
545
546
547 if (fallback && cs == old_wd)
548 continue;
549
550
551 if (!watchdog || cs->rating > watchdog->rating)
552 watchdog = cs;
553 }
554
555 if (!watchdog)
556 watchdog = old_wd;
557
558
559 if (watchdog != old_wd)
560 clocksource_reset_watchdog();
561
562
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
572 list_del_init(&cs->wd_list);
573
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
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
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
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
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
653
654 if (!(cs->flags & CLOCK_SOURCE_SUSPEND_NONSTOP))
655 return;
656
657
658
659
660
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
668 if (!suspend_clocksource || cs->rating > suspend_clocksource->rating)
669 suspend_clocksource = cs;
670}
671
672
673
674
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
686 if (fallback && cs == old_suspend)
687 continue;
688
689 __clocksource_suspend_select(cs);
690 }
691}
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706void clocksource_start_suspend_timing(struct clocksource *cs, u64 start_cycles)
707{
708 if (!suspend_clocksource)
709 return;
710
711
712
713
714
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
732
733
734
735
736
737
738
739
740
741
742
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
753
754
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
770
771
772 if (!clocksource_is_suspend(cs) && suspend_clocksource->disable)
773 suspend_clocksource->disable(suspend_clocksource);
774
775 return nsec;
776}
777
778
779
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
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
806
807
808
809
810
811void clocksource_touch_watchdog(void)
812{
813 clocksource_resume_watchdog();
814}
815
816
817
818
819
820
821static u32 clocksource_max_adjustment(struct clocksource *cs)
822{
823 u64 ret;
824
825
826
827 ret = (u64)cs->mult * 11;
828 do_div(ret,100);
829 return (u32)ret;
830}
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
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
853
854
855 max_cycles = ULLONG_MAX;
856 do_div(max_cycles, mult+maxadj);
857
858
859
860
861
862
863
864 max_cycles = min(max_cycles, mask);
865 max_nsecs = clocksource_cyc2ns(max_cycles, mult - maxadj, shift);
866
867
868 if (max_cyc)
869 *max_cyc = max_cycles;
870
871
872 max_nsecs >>= 1;
873
874 return max_nsecs;
875}
876
877
878
879
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
898
899
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
917 best = clocksource_find_best(oneshot, skipcur);
918 if (!best)
919 return;
920
921 if (!strlen(override_name))
922 goto found;
923
924
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
932
933
934
935 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) && oneshot) {
936
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
944
945
946 pr_info("Override clocksource %s is not currently HRT compatible - deferring\n",
947 cs->name);
948 }
949 } else
950
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
964
965
966
967
968
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
982
983
984
985
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
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
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
1012 if (tmp->rating < cs->rating)
1013 break;
1014 entry = &tmp->list;
1015 }
1016 list_add(&cs->list, entry);
1017}
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031void __clocksource_update_freq_scale(struct clocksource *cs, u32 scale, u32 freq)
1032{
1033 u64 sec;
1034
1035
1036
1037
1038
1039 if (freq) {
1040
1041
1042
1043
1044
1045
1046
1047
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
1063
1064
1065
1066
1067
1068
1069
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
1082
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
1094
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
1109
1110
1111
1112
1113
1114
1115
1116
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
1134 __clocksource_update_freq_scale(cs, scale, freq);
1135
1136
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
1161
1162
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
1182
1183static int clocksource_unbind(struct clocksource *cs)
1184{
1185 unsigned long flags;
1186
1187 if (clocksource_is_watchdog(cs)) {
1188
1189 clocksource_select_watchdog(true);
1190 if (clocksource_is_watchdog(cs))
1191 return -EBUSY;
1192 }
1193
1194 if (cs == curr_clocksource) {
1195
1196 clocksource_select_fallback();
1197 if (curr_clocksource == cs)
1198 return -EBUSY;
1199 }
1200
1201 if (clocksource_is_suspend(cs)) {
1202
1203
1204
1205
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
1220
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
1237
1238
1239
1240
1241
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
1261 if (!cnt || cnt >= CS_NAME_LEN)
1262 return -EINVAL;
1263
1264
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
1275
1276
1277
1278
1279
1280
1281
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
1303
1304
1305
1306
1307
1308
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
1338
1339
1340
1341
1342
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
1355
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
1403
1404
1405
1406
1407
1408
1409
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
1424
1425
1426
1427
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);
1440