2
* linux/kernel/time/clocksource.c
4
* This file contains the functions which manage clocksource drivers.
6
* Copyright (C) 2004, 2005 IBM, John Stultz (johnstul@us.ibm.com)
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.
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.
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.
23
* o Allow clocksource drivers to be unregistered
26
#include <linux/clocksource.h>
27
#include <linux/sysdev.h>
28
#include <linux/init.h>
29
#include <linux/module.h>
30
#include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
31
#include <linux/tick.h>
32
#include <linux/kthread.h>
34
void timecounter_init(struct timecounter *tc,
35
const struct cyclecounter *cc,
39
tc->cycle_last = cc->read(cc);
40
tc->nsec = start_tstamp;
42
EXPORT_SYMBOL_GPL(timecounter_init);
45
* timecounter_read_delta - get nanoseconds since last call of this function
46
* @tc: Pointer to time counter
48
* When the underlying cycle counter runs over, this will be handled
49
* correctly as long as it does not run over more than once between
52
* The first call to this function for a new time counter initializes
53
* the time tracking and returns an undefined result.
55
static u64 timecounter_read_delta(struct timecounter *tc)
57
cycle_t cycle_now, cycle_delta;
60
/* read cycle counter: */
61
cycle_now = tc->cc->read(tc->cc);
63
/* calculate the delta since the last timecounter_read_delta(): */
64
cycle_delta = (cycle_now - tc->cycle_last) & tc->cc->mask;
66
/* convert to nanoseconds: */
67
ns_offset = cyclecounter_cyc2ns(tc->cc, cycle_delta);
69
/* update time stamp of timecounter_read_delta() call: */
70
tc->cycle_last = cycle_now;
75
u64 timecounter_read(struct timecounter *tc)
79
/* increment time by nanoseconds since last call */
80
nsec = timecounter_read_delta(tc);
86
EXPORT_SYMBOL_GPL(timecounter_read);
88
u64 timecounter_cyc2time(struct timecounter *tc,
91
u64 cycle_delta = (cycle_tstamp - tc->cycle_last) & tc->cc->mask;
95
* Instead of always treating cycle_tstamp as more recent
96
* than tc->cycle_last, detect when it is too far in the
97
* future and treat it as old time stamp instead.
99
if (cycle_delta > tc->cc->mask / 2) {
100
cycle_delta = (tc->cycle_last - cycle_tstamp) & tc->cc->mask;
101
nsec = tc->nsec - cyclecounter_cyc2ns(tc->cc, cycle_delta);
103
nsec = cyclecounter_cyc2ns(tc->cc, cycle_delta) + tc->nsec;
108
EXPORT_SYMBOL_GPL(timecounter_cyc2time);
111
* clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
112
* @mult: pointer to mult variable
113
* @shift: pointer to shift variable
114
* @from: frequency to convert from
115
* @to: frequency to convert to
116
* @maxsec: guaranteed runtime conversion range in seconds
118
* The function evaluates the shift/mult pair for the scaled math
119
* operations of clocksources and clockevents.
121
* @to and @from are frequency values in HZ. For clock sources @to is
122
* NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
123
* event @to is the counter frequency and @from is NSEC_PER_SEC.
125
* The @maxsec conversion range argument controls the time frame in
126
* seconds which must be covered by the runtime conversion with the
127
* calculated mult and shift factors. This guarantees that no 64bit
128
* overflow happens when the input value of the conversion is
129
* multiplied with the calculated mult factor. Larger ranges may
130
* reduce the conversion accuracy by chosing smaller mult and shift
134
clocks_calc_mult_shift(u32 *mult, u32 *shift, u32 from, u32 to, u32 maxsec)
140
* Calculate the shift factor which is limiting the conversion
143
tmp = ((u64)maxsec * from) >> 32;
150
* Find the conversion shift/mult pair which has the best
151
* accuracy and fits the maxsec conversion range:
153
for (sft = 32; sft > 0; sft--) {
154
tmp = (u64) to << sft;
157
if ((tmp >> sftacc) == 0)
164
/*[Clocksource internal variables]---------
166
* currently selected clocksource.
168
* linked list with the registered clocksources
170
* protects manipulations to curr_clocksource and the clocksource_list
172
* Name of the user-specified clocksource.
174
static struct clocksource *curr_clocksource;
175
static LIST_HEAD(clocksource_list);
176
static DEFINE_MUTEX(clocksource_mutex);
177
static char override_name[32];
178
static int finished_booting;
180
#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
181
static void clocksource_watchdog_work(struct work_struct *work);
183
static LIST_HEAD(watchdog_list);
184
static struct clocksource *watchdog;
185
static struct timer_list watchdog_timer;
186
static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
187
static DEFINE_SPINLOCK(watchdog_lock);
188
static int watchdog_running;
189
static atomic_t watchdog_reset_pending;
191
static int clocksource_watchdog_kthread(void *data);
192
static void __clocksource_change_rating(struct clocksource *cs, int rating);
195
* Interval: 0.5sec Threshold: 0.0625s
197
#define WATCHDOG_INTERVAL (HZ >> 1)
198
#define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
200
static void clocksource_watchdog_work(struct work_struct *work)
203
* If kthread_run fails the next watchdog scan over the
204
* watchdog_list will find the unstable clock again.
206
kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
209
static void __clocksource_unstable(struct clocksource *cs)
211
cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
212
cs->flags |= CLOCK_SOURCE_UNSTABLE;
213
if (finished_booting)
214
schedule_work(&watchdog_work);
217
static void clocksource_unstable(struct clocksource *cs, int64_t delta)
219
printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
221
__clocksource_unstable(cs);
225
* clocksource_mark_unstable - mark clocksource unstable via watchdog
226
* @cs: clocksource to be marked unstable
228
* This function is called instead of clocksource_change_rating from
229
* cpu hotplug code to avoid a deadlock between the clocksource mutex
230
* and the cpu hotplug mutex. It defers the update of the clocksource
231
* to the watchdog thread.
233
void clocksource_mark_unstable(struct clocksource *cs)
237
spin_lock_irqsave(&watchdog_lock, flags);
238
if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
239
if (list_empty(&cs->wd_list))
240
list_add(&cs->wd_list, &watchdog_list);
241
__clocksource_unstable(cs);
243
spin_unlock_irqrestore(&watchdog_lock, flags);
246
static void clocksource_watchdog(unsigned long data)
248
struct clocksource *cs;
249
cycle_t csnow, wdnow;
250
int64_t wd_nsec, cs_nsec;
251
int next_cpu, reset_pending;
253
spin_lock(&watchdog_lock);
254
if (!watchdog_running)
257
reset_pending = atomic_read(&watchdog_reset_pending);
259
list_for_each_entry(cs, &watchdog_list, wd_list) {
261
/* Clocksource already marked unstable? */
262
if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
263
if (finished_booting)
264
schedule_work(&watchdog_work);
269
csnow = cs->read(cs);
270
wdnow = watchdog->read(watchdog);
273
/* Clocksource initialized ? */
274
if (!(cs->flags & CLOCK_SOURCE_WATCHDOG) ||
275
atomic_read(&watchdog_reset_pending)) {
276
cs->flags |= CLOCK_SOURCE_WATCHDOG;
282
wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog->mask,
283
watchdog->mult, watchdog->shift);
285
cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) &
286
cs->mask, cs->mult, cs->shift);
290
if (atomic_read(&watchdog_reset_pending))
293
/* Check the deviation from the watchdog clocksource. */
294
if ((abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD)) {
295
clocksource_unstable(cs, cs_nsec - wd_nsec);
299
if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
300
(cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
301
(watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
302
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
304
* We just marked the clocksource as highres-capable,
305
* notify the rest of the system as well so that we
306
* transition into high-res mode:
313
* We only clear the watchdog_reset_pending, when we did a
314
* full cycle through all clocksources.
317
atomic_dec(&watchdog_reset_pending);
320
* Cycle through CPUs to check if the CPUs stay synchronized
323
next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
324
if (next_cpu >= nr_cpu_ids)
325
next_cpu = cpumask_first(cpu_online_mask);
326
watchdog_timer.expires += WATCHDOG_INTERVAL;
327
add_timer_on(&watchdog_timer, next_cpu);
329
spin_unlock(&watchdog_lock);
332
static inline void clocksource_start_watchdog(void)
334
if (watchdog_running || !watchdog || list_empty(&watchdog_list))
336
init_timer(&watchdog_timer);
337
watchdog_timer.function = clocksource_watchdog;
338
watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
339
add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
340
watchdog_running = 1;
343
static inline void clocksource_stop_watchdog(void)
345
if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
347
del_timer(&watchdog_timer);
348
watchdog_running = 0;
351
static inline void clocksource_reset_watchdog(void)
353
struct clocksource *cs;
355
list_for_each_entry(cs, &watchdog_list, wd_list)
356
cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
359
static void clocksource_resume_watchdog(void)
361
atomic_inc(&watchdog_reset_pending);
364
static void clocksource_enqueue_watchdog(struct clocksource *cs)
368
spin_lock_irqsave(&watchdog_lock, flags);
369
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
370
/* cs is a clocksource to be watched. */
371
list_add(&cs->wd_list, &watchdog_list);
372
cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
374
/* cs is a watchdog. */
375
if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
376
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
377
/* Pick the best watchdog. */
378
if (!watchdog || cs->rating > watchdog->rating) {
380
/* Reset watchdog cycles */
381
clocksource_reset_watchdog();
384
/* Check if the watchdog timer needs to be started. */
385
clocksource_start_watchdog();
386
spin_unlock_irqrestore(&watchdog_lock, flags);
389
static void clocksource_dequeue_watchdog(struct clocksource *cs)
391
struct clocksource *tmp;
394
spin_lock_irqsave(&watchdog_lock, flags);
395
if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
396
/* cs is a watched clocksource. */
397
list_del_init(&cs->wd_list);
398
} else if (cs == watchdog) {
399
/* Reset watchdog cycles */
400
clocksource_reset_watchdog();
401
/* Current watchdog is removed. Find an alternative. */
403
list_for_each_entry(tmp, &clocksource_list, list) {
404
if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY)
406
if (!watchdog || tmp->rating > watchdog->rating)
410
cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
411
/* Check if the watchdog timer needs to be stopped. */
412
clocksource_stop_watchdog();
413
spin_unlock_irqrestore(&watchdog_lock, flags);
416
static int clocksource_watchdog_kthread(void *data)
418
struct clocksource *cs, *tmp;
422
mutex_lock(&clocksource_mutex);
423
spin_lock_irqsave(&watchdog_lock, flags);
424
list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)
425
if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
426
list_del_init(&cs->wd_list);
427
list_add(&cs->wd_list, &unstable);
429
/* Check if the watchdog timer needs to be stopped. */
430
clocksource_stop_watchdog();
431
spin_unlock_irqrestore(&watchdog_lock, flags);
433
/* Needs to be done outside of watchdog lock */
434
list_for_each_entry_safe(cs, tmp, &unstable, wd_list) {
435
list_del_init(&cs->wd_list);
436
__clocksource_change_rating(cs, 0);
438
mutex_unlock(&clocksource_mutex);
442
#else /* CONFIG_CLOCKSOURCE_WATCHDOG */
444
static void clocksource_enqueue_watchdog(struct clocksource *cs)
446
if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
447
cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
450
static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
451
static inline void clocksource_resume_watchdog(void) { }
452
static inline int clocksource_watchdog_kthread(void *data) { return 0; }
454
#endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
457
* clocksource_suspend - suspend the clocksource(s)
459
void clocksource_suspend(void)
461
struct clocksource *cs;
463
list_for_each_entry_reverse(cs, &clocksource_list, list)
469
* clocksource_resume - resume the clocksource(s)
471
void clocksource_resume(void)
473
struct clocksource *cs;
475
list_for_each_entry(cs, &clocksource_list, list)
479
clocksource_resume_watchdog();
483
* clocksource_touch_watchdog - Update watchdog
485
* Update the watchdog after exception contexts such as kgdb so as not
486
* to incorrectly trip the watchdog. This might fail when the kernel
487
* was stopped in code which holds watchdog_lock.
489
void clocksource_touch_watchdog(void)
491
clocksource_resume_watchdog();
495
* clocksource_max_adjustment- Returns max adjustment amount
496
* @cs: Pointer to clocksource
499
static u32 clocksource_max_adjustment(struct clocksource *cs)
503
* We won't try to correct for more then 11% adjustments (110,000 ppm),
505
ret = (u64)cs->mult * 11;
511
* clocksource_max_deferment - Returns max time the clocksource can be deferred
512
* @cs: Pointer to clocksource
515
static u64 clocksource_max_deferment(struct clocksource *cs)
517
u64 max_nsecs, max_cycles;
520
* Calculate the maximum number of cycles that we can pass to the
521
* cyc2ns function without overflowing a 64-bit signed result. The
522
* maximum number of cycles is equal to ULLONG_MAX/(cs->mult+cs->maxadj)
523
* which is equivalent to the below.
524
* max_cycles < (2^63)/(cs->mult + cs->maxadj)
525
* max_cycles < 2^(log2((2^63)/(cs->mult + cs->maxadj)))
526
* max_cycles < 2^(log2(2^63) - log2(cs->mult + cs->maxadj))
527
* max_cycles < 2^(63 - log2(cs->mult + cs->maxadj))
528
* max_cycles < 1 << (63 - log2(cs->mult + cs->maxadj))
529
* Please note that we add 1 to the result of the log2 to account for
530
* any rounding errors, ensure the above inequality is satisfied and
531
* no overflow will occur.
533
max_cycles = 1ULL << (63 - (ilog2(cs->mult + cs->maxadj) + 1));
536
* The actual maximum number of cycles we can defer the clocksource is
537
* determined by the minimum of max_cycles and cs->mask.
538
* Note: Here we subtract the maxadj to make sure we don't sleep for
539
* too long if there's a large negative adjustment.
541
max_cycles = min_t(u64, max_cycles, (u64) cs->mask);
542
max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult - cs->maxadj,
546
* To ensure that the clocksource does not wrap whilst we are idle,
547
* limit the time the clocksource can be deferred by 12.5%. Please
548
* note a margin of 12.5% is used because this can be computed with
549
* a shift, versus say 10% which would require division.
551
return max_nsecs - (max_nsecs >> 3);
554
#ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
557
* clocksource_select - Select the best clocksource available
559
* Private function. Must hold clocksource_mutex when called.
561
* Select the clocksource with the best rating, or the clocksource,
562
* which is selected by userspace override.
564
static void clocksource_select(void)
566
struct clocksource *best, *cs;
568
if (!finished_booting || list_empty(&clocksource_list))
570
/* First clocksource on the list has the best rating. */
571
best = list_first_entry(&clocksource_list, struct clocksource, list);
572
/* Check for the override clocksource. */
573
list_for_each_entry(cs, &clocksource_list, list) {
574
if (strcmp(cs->name, override_name) != 0)
577
* Check to make sure we don't switch to a non-highres
578
* capable clocksource if the tick code is in oneshot
579
* mode (highres or nohz)
581
if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
582
tick_oneshot_mode_active()) {
583
/* Override clocksource cannot be used. */
584
printk(KERN_WARNING "Override clocksource %s is not "
585
"HRT compatible. Cannot switch while in "
586
"HRT/NOHZ mode\n", cs->name);
587
override_name[0] = 0;
589
/* Override clocksource can be used. */
593
if (curr_clocksource != best) {
594
printk(KERN_INFO "Switching to clocksource %s\n", best->name);
595
curr_clocksource = best;
596
timekeeping_notify(curr_clocksource);
600
#else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */
602
static inline void clocksource_select(void) { }
607
* clocksource_done_booting - Called near the end of core bootup
609
* Hack to avoid lots of clocksource churn at boot time.
610
* We use fs_initcall because we want this to start before
611
* device_initcall but after subsys_initcall.
613
static int __init clocksource_done_booting(void)
615
mutex_lock(&clocksource_mutex);
616
curr_clocksource = clocksource_default_clock();
617
mutex_unlock(&clocksource_mutex);
619
finished_booting = 1;
622
* Run the watchdog first to eliminate unstable clock sources
624
clocksource_watchdog_kthread(NULL);
626
mutex_lock(&clocksource_mutex);
627
clocksource_select();
628
mutex_unlock(&clocksource_mutex);
631
fs_initcall(clocksource_done_booting);
634
* Enqueue the clocksource sorted by rating
636
static void clocksource_enqueue(struct clocksource *cs)
638
struct list_head *entry = &clocksource_list;
639
struct clocksource *tmp;
641
list_for_each_entry(tmp, &clocksource_list, list)
642
/* Keep track of the place, where to insert */
643
if (tmp->rating >= cs->rating)
645
list_add(&cs->list, entry);
649
* __clocksource_updatefreq_scale - Used update clocksource with new freq
650
* @cs: clocksource to be registered
651
* @scale: Scale factor multiplied against freq to get clocksource hz
652
* @freq: clocksource frequency (cycles per second) divided by scale
654
* This should only be called from the clocksource->enable() method.
656
* This *SHOULD NOT* be called directly! Please use the
657
* clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions.
659
void __clocksource_updatefreq_scale(struct clocksource *cs, u32 scale, u32 freq)
663
* Calc the maximum number of seconds which we can run before
664
* wrapping around. For clocksources which have a mask > 32bit
665
* we need to limit the max sleep time to have a good
666
* conversion precision. 10 minutes is still a reasonable
667
* amount. That results in a shift value of 24 for a
668
* clocksource with mask >= 40bit and f >= 4GHz. That maps to
669
* ~ 0.06ppm granularity for NTP. We apply the same 12.5%
670
* margin as we do in clocksource_max_deferment()
672
sec = (cs->mask - (cs->mask >> 3));
677
else if (sec > 600 && cs->mask > UINT_MAX)
680
clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
681
NSEC_PER_SEC / scale, sec * scale);
684
* for clocksources that have large mults, to avoid overflow.
685
* Since mult may be adjusted by ntp, add an safety extra margin
688
cs->maxadj = clocksource_max_adjustment(cs);
689
while ((cs->mult + cs->maxadj < cs->mult)
690
|| (cs->mult - cs->maxadj > cs->mult)) {
693
cs->maxadj = clocksource_max_adjustment(cs);
696
cs->max_idle_ns = clocksource_max_deferment(cs);
698
EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale);
701
* __clocksource_register_scale - Used to install new clocksources
702
* @cs: clocksource to be registered
703
* @scale: Scale factor multiplied against freq to get clocksource hz
704
* @freq: clocksource frequency (cycles per second) divided by scale
706
* Returns -EBUSY if registration fails, zero otherwise.
708
* This *SHOULD NOT* be called directly! Please use the
709
* clocksource_register_hz() or clocksource_register_khz helper functions.
711
int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
714
/* Initialize mult/shift and max_idle_ns */
715
__clocksource_updatefreq_scale(cs, scale, freq);
717
/* Add clocksource to the clcoksource list */
718
mutex_lock(&clocksource_mutex);
719
clocksource_enqueue(cs);
720
clocksource_enqueue_watchdog(cs);
721
clocksource_select();
722
mutex_unlock(&clocksource_mutex);
725
EXPORT_SYMBOL_GPL(__clocksource_register_scale);
729
* clocksource_register - Used to install new clocksources
730
* @cs: clocksource to be registered
732
* Returns -EBUSY if registration fails, zero otherwise.
734
int clocksource_register(struct clocksource *cs)
736
/* calculate max adjustment for given mult/shift */
737
cs->maxadj = clocksource_max_adjustment(cs);
738
WARN_ONCE(cs->mult + cs->maxadj < cs->mult,
739
"Clocksource %s might overflow on 11%% adjustment\n",
742
/* calculate max idle time permitted for this clocksource */
743
cs->max_idle_ns = clocksource_max_deferment(cs);
745
mutex_lock(&clocksource_mutex);
746
clocksource_enqueue(cs);
747
clocksource_enqueue_watchdog(cs);
748
clocksource_select();
749
mutex_unlock(&clocksource_mutex);
752
EXPORT_SYMBOL(clocksource_register);
754
static void __clocksource_change_rating(struct clocksource *cs, int rating)
758
clocksource_enqueue(cs);
759
clocksource_select();
763
* clocksource_change_rating - Change the rating of a registered clocksource
764
* @cs: clocksource to be changed
765
* @rating: new rating
767
void clocksource_change_rating(struct clocksource *cs, int rating)
769
mutex_lock(&clocksource_mutex);
770
__clocksource_change_rating(cs, rating);
771
mutex_unlock(&clocksource_mutex);
773
EXPORT_SYMBOL(clocksource_change_rating);
776
* clocksource_unregister - remove a registered clocksource
777
* @cs: clocksource to be unregistered
779
void clocksource_unregister(struct clocksource *cs)
781
mutex_lock(&clocksource_mutex);
782
clocksource_dequeue_watchdog(cs);
784
clocksource_select();
785
mutex_unlock(&clocksource_mutex);
787
EXPORT_SYMBOL(clocksource_unregister);
791
* sysfs_show_current_clocksources - sysfs interface for current clocksource
794
* @buf: char buffer to be filled with clocksource list
796
* Provides sysfs interface for listing current clocksource.
799
sysfs_show_current_clocksources(struct sys_device *dev,
800
struct sysdev_attribute *attr, char *buf)
804
mutex_lock(&clocksource_mutex);
805
count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
806
mutex_unlock(&clocksource_mutex);
812
* sysfs_override_clocksource - interface for manually overriding clocksource
815
* @buf: name of override clocksource
816
* @count: length of buffer
818
* Takes input from sysfs interface for manually overriding the default
819
* clocksource selection.
821
static ssize_t sysfs_override_clocksource(struct sys_device *dev,
822
struct sysdev_attribute *attr,
823
const char *buf, size_t count)
827
/* strings from sysfs write are not 0 terminated! */
828
if (count >= sizeof(override_name))
832
if (buf[count-1] == '\n')
835
mutex_lock(&clocksource_mutex);
838
memcpy(override_name, buf, count);
839
override_name[count] = 0;
840
clocksource_select();
842
mutex_unlock(&clocksource_mutex);
848
* sysfs_show_available_clocksources - sysfs interface for listing clocksource
851
* @buf: char buffer to be filled with clocksource list
853
* Provides sysfs interface for listing registered clocksources
856
sysfs_show_available_clocksources(struct sys_device *dev,
857
struct sysdev_attribute *attr,
860
struct clocksource *src;
863
mutex_lock(&clocksource_mutex);
864
list_for_each_entry(src, &clocksource_list, list) {
866
* Don't show non-HRES clocksource if the tick code is
867
* in one shot mode (highres=on or nohz=on)
869
if (!tick_oneshot_mode_active() ||
870
(src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
871
count += snprintf(buf + count,
872
max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
875
mutex_unlock(&clocksource_mutex);
877
count += snprintf(buf + count,
878
max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
886
static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources,
887
sysfs_override_clocksource);
889
static SYSDEV_ATTR(available_clocksource, 0444,
890
sysfs_show_available_clocksources, NULL);
892
static struct sysdev_class clocksource_sysclass = {
893
.name = "clocksource",
896
static struct sys_device device_clocksource = {
898
.cls = &clocksource_sysclass,
901
static int __init init_clocksource_sysfs(void)
903
int error = sysdev_class_register(&clocksource_sysclass);
906
error = sysdev_register(&device_clocksource);
908
error = sysdev_create_file(
910
&attr_current_clocksource);
912
error = sysdev_create_file(
914
&attr_available_clocksource);
918
device_initcall(init_clocksource_sysfs);
919
#endif /* CONFIG_SYSFS */
922
* boot_override_clocksource - boot clock override
923
* @str: override name
925
* Takes a clocksource= boot argument and uses it
926
* as the clocksource override name.
928
static int __init boot_override_clocksource(char* str)
930
mutex_lock(&clocksource_mutex);
932
strlcpy(override_name, str, sizeof(override_name));
933
mutex_unlock(&clocksource_mutex);
937
__setup("clocksource=", boot_override_clocksource);
940
* boot_override_clock - Compatibility layer for deprecated boot option
941
* @str: override name
943
* DEPRECATED! Takes a clock= boot argument and uses it
944
* as the clocksource override name
946
static int __init boot_override_clock(char* str)
948
if (!strcmp(str, "pmtmr")) {
949
printk("Warning: clock=pmtmr is deprecated. "
950
"Use clocksource=acpi_pm.\n");
951
return boot_override_clocksource("acpi_pm");
953
printk("Warning! clock= boot option is deprecated. "
954
"Use clocksource=xyz\n");
955
return boot_override_clocksource(str);
958
__setup("clock=", boot_override_clock);