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