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