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 * @minsec: 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 @minsec 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 minsec)
140 * Calculate the shift factor which is limiting the conversion
143 tmp = ((u64)minsec * 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;
156 if ((tmp >> sftacc) == 0)
163 /*[Clocksource internal variables]---------
165 * currently selected clocksource.
167 * linked list with the registered clocksources
169 * protects manipulations to curr_clocksource and the clocksource_list
171 * Name of the user-specified clocksource.
173 static struct clocksource *curr_clocksource;
174 static LIST_HEAD(clocksource_list);
175 static DEFINE_MUTEX(clocksource_mutex);
176 static char override_name[32];
177 static int finished_booting;
179 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
180 static void clocksource_watchdog_work(struct work_struct *work);
182 static LIST_HEAD(watchdog_list);
183 static struct clocksource *watchdog;
184 static struct timer_list watchdog_timer;
185 static DECLARE_WORK(watchdog_work, clocksource_watchdog_work);
186 static DEFINE_SPINLOCK(watchdog_lock);
187 static int watchdog_running;
189 static int clocksource_watchdog_kthread(void *data);
190 static void __clocksource_change_rating(struct clocksource *cs, int rating);
193 * Interval: 0.5sec Threshold: 0.0625s
195 #define WATCHDOG_INTERVAL (HZ >> 1)
196 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
198 static void clocksource_watchdog_work(struct work_struct *work)
201 * If kthread_run fails the next watchdog scan over the
202 * watchdog_list will find the unstable clock again.
204 kthread_run(clocksource_watchdog_kthread, NULL, "kwatchdog");
207 static void __clocksource_unstable(struct clocksource *cs)
209 cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
210 cs->flags |= CLOCK_SOURCE_UNSTABLE;
211 if (finished_booting)
212 schedule_work(&watchdog_work);
215 static void clocksource_unstable(struct clocksource *cs, int64_t delta)
217 printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
219 __clocksource_unstable(cs);
223 * clocksource_mark_unstable - mark clocksource unstable via watchdog
224 * @cs: clocksource to be marked unstable
226 * This function is called instead of clocksource_change_rating from
227 * cpu hotplug code to avoid a deadlock between the clocksource mutex
228 * and the cpu hotplug mutex. It defers the update of the clocksource
229 * to the watchdog thread.
231 void clocksource_mark_unstable(struct clocksource *cs)
235 spin_lock_irqsave(&watchdog_lock, flags);
236 if (!(cs->flags & CLOCK_SOURCE_UNSTABLE)) {
237 if (list_empty(&cs->wd_list))
238 list_add(&cs->wd_list, &watchdog_list);
239 __clocksource_unstable(cs);
241 spin_unlock_irqrestore(&watchdog_lock, flags);
244 static void clocksource_watchdog(unsigned long data)
246 struct clocksource *cs;
247 cycle_t csnow, wdnow;
248 int64_t wd_nsec, cs_nsec;
251 spin_lock(&watchdog_lock);
252 if (!watchdog_running)
255 list_for_each_entry(cs, &watchdog_list, wd_list) {
257 /* Clocksource already marked unstable? */
258 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
259 if (finished_booting)
260 schedule_work(&watchdog_work);
265 csnow = cs->read(cs);
266 wdnow = watchdog->read(watchdog);
269 /* Clocksource initialized ? */
270 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
271 cs->flags |= CLOCK_SOURCE_WATCHDOG;
277 wd_nsec = clocksource_cyc2ns((wdnow - cs->wd_last) & watchdog->mask,
278 watchdog->mult, watchdog->shift);
280 cs_nsec = clocksource_cyc2ns((csnow - cs->cs_last) &
281 cs->mask, cs->mult, cs->shift);
285 /* Check the deviation from the watchdog clocksource. */
286 if (abs(cs_nsec - wd_nsec) > WATCHDOG_THRESHOLD) {
287 clocksource_unstable(cs, cs_nsec - wd_nsec);
291 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
292 (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
293 (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
294 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
296 * We just marked the clocksource as highres-capable,
297 * notify the rest of the system as well so that we
298 * transition into high-res mode:
305 * Cycle through CPUs to check if the CPUs stay synchronized
308 next_cpu = cpumask_next(raw_smp_processor_id(), cpu_online_mask);
309 if (next_cpu >= nr_cpu_ids)
310 next_cpu = cpumask_first(cpu_online_mask);
311 watchdog_timer.expires += WATCHDOG_INTERVAL;
312 add_timer_on(&watchdog_timer, next_cpu);
314 spin_unlock(&watchdog_lock);
317 static inline void clocksource_start_watchdog(void)
319 if (watchdog_running || !watchdog || list_empty(&watchdog_list))
321 init_timer(&watchdog_timer);
322 watchdog_timer.function = clocksource_watchdog;
323 watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
324 add_timer_on(&watchdog_timer, cpumask_first(cpu_online_mask));
325 watchdog_running = 1;
328 static inline void clocksource_stop_watchdog(void)
330 if (!watchdog_running || (watchdog && !list_empty(&watchdog_list)))
332 del_timer(&watchdog_timer);
333 watchdog_running = 0;
336 static inline void clocksource_reset_watchdog(void)
338 struct clocksource *cs;
340 list_for_each_entry(cs, &watchdog_list, wd_list)
341 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
344 static void clocksource_resume_watchdog(void)
349 * We use trylock here to avoid a potential dead lock when
350 * kgdb calls this code after the kernel has been stopped with
351 * watchdog_lock held. When watchdog_lock is held we just
352 * return and accept, that the watchdog might trigger and mark
353 * the monitored clock source (usually TSC) unstable.
355 * This does not affect the other caller clocksource_resume()
356 * because at this point the kernel is UP, interrupts are
357 * disabled and nothing can hold watchdog_lock.
359 if (!spin_trylock_irqsave(&watchdog_lock, flags))
361 clocksource_reset_watchdog();
362 spin_unlock_irqrestore(&watchdog_lock, flags);
365 static void clocksource_enqueue_watchdog(struct clocksource *cs)
369 spin_lock_irqsave(&watchdog_lock, flags);
370 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
371 /* cs is a clocksource to be watched. */
372 list_add(&cs->wd_list, &watchdog_list);
373 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
375 /* cs is a watchdog. */
376 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
377 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
378 /* Pick the best watchdog. */
379 if (!watchdog || cs->rating > watchdog->rating) {
381 /* Reset watchdog cycles */
382 clocksource_reset_watchdog();
385 /* Check if the watchdog timer needs to be started. */
386 clocksource_start_watchdog();
387 spin_unlock_irqrestore(&watchdog_lock, flags);
390 static void clocksource_dequeue_watchdog(struct clocksource *cs)
392 struct clocksource *tmp;
395 spin_lock_irqsave(&watchdog_lock, flags);
396 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
397 /* cs is a watched clocksource. */
398 list_del_init(&cs->wd_list);
399 } else if (cs == watchdog) {
400 /* Reset watchdog cycles */
401 clocksource_reset_watchdog();
402 /* Current watchdog is removed. Find an alternative. */
404 list_for_each_entry(tmp, &clocksource_list, list) {
405 if (tmp == cs || tmp->flags & CLOCK_SOURCE_MUST_VERIFY)
407 if (!watchdog || tmp->rating > watchdog->rating)
411 cs->flags &= ~CLOCK_SOURCE_WATCHDOG;
412 /* Check if the watchdog timer needs to be stopped. */
413 clocksource_stop_watchdog();
414 spin_unlock_irqrestore(&watchdog_lock, flags);
417 static int clocksource_watchdog_kthread(void *data)
419 struct clocksource *cs, *tmp;
423 mutex_lock(&clocksource_mutex);
424 spin_lock_irqsave(&watchdog_lock, flags);
425 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list)
426 if (cs->flags & CLOCK_SOURCE_UNSTABLE) {
427 list_del_init(&cs->wd_list);
428 list_add(&cs->wd_list, &unstable);
430 /* Check if the watchdog timer needs to be stopped. */
431 clocksource_stop_watchdog();
432 spin_unlock_irqrestore(&watchdog_lock, flags);
434 /* Needs to be done outside of watchdog lock */
435 list_for_each_entry_safe(cs, tmp, &unstable, wd_list) {
436 list_del_init(&cs->wd_list);
437 __clocksource_change_rating(cs, 0);
439 mutex_unlock(&clocksource_mutex);
443 #else /* CONFIG_CLOCKSOURCE_WATCHDOG */
445 static void clocksource_enqueue_watchdog(struct clocksource *cs)
447 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
448 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
451 static inline void clocksource_dequeue_watchdog(struct clocksource *cs) { }
452 static inline void clocksource_resume_watchdog(void) { }
453 static inline int clocksource_watchdog_kthread(void *data) { return 0; }
455 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
458 * clocksource_suspend - suspend the clocksource(s)
460 void clocksource_suspend(void)
462 struct clocksource *cs;
464 list_for_each_entry_reverse(cs, &clocksource_list, list)
470 * clocksource_resume - resume the clocksource(s)
472 void clocksource_resume(void)
474 struct clocksource *cs;
476 list_for_each_entry(cs, &clocksource_list, list)
480 clocksource_resume_watchdog();
484 * clocksource_touch_watchdog - Update watchdog
486 * Update the watchdog after exception contexts such as kgdb so as not
487 * to incorrectly trip the watchdog. This might fail when the kernel
488 * was stopped in code which holds watchdog_lock.
490 void clocksource_touch_watchdog(void)
492 clocksource_resume_watchdog();
496 * clocksource_max_deferment - Returns max time the clocksource can be deferred
497 * @cs: Pointer to clocksource
500 static u64 clocksource_max_deferment(struct clocksource *cs)
502 u64 max_nsecs, max_cycles;
505 * Calculate the maximum number of cycles that we can pass to the
506 * cyc2ns function without overflowing a 64-bit signed result. The
507 * maximum number of cycles is equal to ULLONG_MAX/cs->mult which
508 * is equivalent to the below.
509 * max_cycles < (2^63)/cs->mult
510 * max_cycles < 2^(log2((2^63)/cs->mult))
511 * max_cycles < 2^(log2(2^63) - log2(cs->mult))
512 * max_cycles < 2^(63 - log2(cs->mult))
513 * max_cycles < 1 << (63 - log2(cs->mult))
514 * Please note that we add 1 to the result of the log2 to account for
515 * any rounding errors, ensure the above inequality is satisfied and
516 * no overflow will occur.
518 max_cycles = 1ULL << (63 - (ilog2(cs->mult) + 1));
521 * The actual maximum number of cycles we can defer the clocksource is
522 * determined by the minimum of max_cycles and cs->mask.
524 max_cycles = min_t(u64, max_cycles, (u64) cs->mask);
525 max_nsecs = clocksource_cyc2ns(max_cycles, cs->mult, cs->shift);
528 * To ensure that the clocksource does not wrap whilst we are idle,
529 * limit the time the clocksource can be deferred by 12.5%. Please
530 * note a margin of 12.5% is used because this can be computed with
531 * a shift, versus say 10% which would require division.
533 return max_nsecs - (max_nsecs >> 5);
536 #ifdef CONFIG_GENERIC_TIME
539 * clocksource_select - Select the best clocksource available
541 * Private function. Must hold clocksource_mutex when called.
543 * Select the clocksource with the best rating, or the clocksource,
544 * which is selected by userspace override.
546 static void clocksource_select(void)
548 struct clocksource *best, *cs;
550 if (!finished_booting || list_empty(&clocksource_list))
552 /* First clocksource on the list has the best rating. */
553 best = list_first_entry(&clocksource_list, struct clocksource, list);
554 /* Check for the override clocksource. */
555 list_for_each_entry(cs, &clocksource_list, list) {
556 if (strcmp(cs->name, override_name) != 0)
559 * Check to make sure we don't switch to a non-highres
560 * capable clocksource if the tick code is in oneshot
561 * mode (highres or nohz)
563 if (!(cs->flags & CLOCK_SOURCE_VALID_FOR_HRES) &&
564 tick_oneshot_mode_active()) {
565 /* Override clocksource cannot be used. */
566 printk(KERN_WARNING "Override clocksource %s is not "
567 "HRT compatible. Cannot switch while in "
568 "HRT/NOHZ mode\n", cs->name);
569 override_name[0] = 0;
571 /* Override clocksource can be used. */
575 if (curr_clocksource != best) {
576 printk(KERN_INFO "Switching to clocksource %s\n", best->name);
577 curr_clocksource = best;
578 timekeeping_notify(curr_clocksource);
582 #else /* CONFIG_GENERIC_TIME */
584 static inline void clocksource_select(void) { }
589 * clocksource_done_booting - Called near the end of core bootup
591 * Hack to avoid lots of clocksource churn at boot time.
592 * We use fs_initcall because we want this to start before
593 * device_initcall but after subsys_initcall.
595 static int __init clocksource_done_booting(void)
597 mutex_lock(&clocksource_mutex);
598 curr_clocksource = clocksource_default_clock();
599 mutex_unlock(&clocksource_mutex);
601 finished_booting = 1;
604 * Run the watchdog first to eliminate unstable clock sources
606 clocksource_watchdog_kthread(NULL);
608 mutex_lock(&clocksource_mutex);
609 clocksource_select();
610 mutex_unlock(&clocksource_mutex);
613 fs_initcall(clocksource_done_booting);
616 * Enqueue the clocksource sorted by rating
618 static void clocksource_enqueue(struct clocksource *cs)
620 struct list_head *entry = &clocksource_list;
621 struct clocksource *tmp;
623 list_for_each_entry(tmp, &clocksource_list, list)
624 /* Keep track of the place, where to insert */
625 if (tmp->rating >= cs->rating)
627 list_add(&cs->list, entry);
632 * Maximum time we expect to go between ticks. This includes idle
633 * tickless time. It provides the trade off between selecting a
634 * mult/shift pair that is very precise but can only handle a short
635 * period of time, vs. a mult/shift pair that can handle long periods
636 * of time but isn't as precise.
638 * This is a subsystem constant, and actual hardware limitations
639 * may override it (ie: clocksources that wrap every 3 seconds).
641 #define MAX_UPDATE_LENGTH 5 /* Seconds */
644 * __clocksource_register_scale - Used to install new clocksources
645 * @t: clocksource to be registered
646 * @scale: Scale factor multiplied against freq to get clocksource hz
647 * @freq: clocksource frequency (cycles per second) divided by scale
649 * Returns -EBUSY if registration fails, zero otherwise.
651 * This *SHOULD NOT* be called directly! Please use the
652 * clocksource_register_hz() or clocksource_register_khz helper functions.
654 int __clocksource_register_scale(struct clocksource *cs, u32 scale, u32 freq)
658 * Ideally we want to use some of the limits used in
659 * clocksource_max_deferment, to provide a more informed
660 * MAX_UPDATE_LENGTH. But for now this just gets the
661 * register interface working properly.
663 clocks_calc_mult_shift(&cs->mult, &cs->shift, freq,
665 MAX_UPDATE_LENGTH*scale);
666 cs->max_idle_ns = clocksource_max_deferment(cs);
668 mutex_lock(&clocksource_mutex);
669 clocksource_enqueue(cs);
670 clocksource_enqueue_watchdog(cs);
671 clocksource_select();
672 mutex_unlock(&clocksource_mutex);
675 EXPORT_SYMBOL_GPL(__clocksource_register_scale);
679 * clocksource_register - Used to install new clocksources
680 * @t: clocksource to be registered
682 * Returns -EBUSY if registration fails, zero otherwise.
684 int clocksource_register(struct clocksource *cs)
686 /* calculate max idle time permitted for this clocksource */
687 cs->max_idle_ns = clocksource_max_deferment(cs);
689 mutex_lock(&clocksource_mutex);
690 clocksource_enqueue(cs);
691 clocksource_select();
692 clocksource_enqueue_watchdog(cs);
693 mutex_unlock(&clocksource_mutex);
696 EXPORT_SYMBOL(clocksource_register);
698 static void __clocksource_change_rating(struct clocksource *cs, int rating)
702 clocksource_enqueue(cs);
703 clocksource_select();
707 * clocksource_change_rating - Change the rating of a registered clocksource
709 void clocksource_change_rating(struct clocksource *cs, int rating)
711 mutex_lock(&clocksource_mutex);
712 __clocksource_change_rating(cs, rating);
713 mutex_unlock(&clocksource_mutex);
715 EXPORT_SYMBOL(clocksource_change_rating);
718 * clocksource_unregister - remove a registered clocksource
720 void clocksource_unregister(struct clocksource *cs)
722 mutex_lock(&clocksource_mutex);
723 clocksource_dequeue_watchdog(cs);
725 clocksource_select();
726 mutex_unlock(&clocksource_mutex);
728 EXPORT_SYMBOL(clocksource_unregister);
732 * sysfs_show_current_clocksources - sysfs interface for current clocksource
734 * @buf: char buffer to be filled with clocksource list
736 * Provides sysfs interface for listing current clocksource.
739 sysfs_show_current_clocksources(struct sys_device *dev,
740 struct sysdev_attribute *attr, char *buf)
744 mutex_lock(&clocksource_mutex);
745 count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
746 mutex_unlock(&clocksource_mutex);
752 * sysfs_override_clocksource - interface for manually overriding clocksource
754 * @buf: name of override clocksource
755 * @count: length of buffer
757 * Takes input from sysfs interface for manually overriding the default
758 * clocksource selection.
760 static ssize_t sysfs_override_clocksource(struct sys_device *dev,
761 struct sysdev_attribute *attr,
762 const char *buf, size_t count)
766 /* strings from sysfs write are not 0 terminated! */
767 if (count >= sizeof(override_name))
771 if (buf[count-1] == '\n')
774 mutex_lock(&clocksource_mutex);
777 memcpy(override_name, buf, count);
778 override_name[count] = 0;
779 clocksource_select();
781 mutex_unlock(&clocksource_mutex);
787 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
789 * @buf: char buffer to be filled with clocksource list
791 * Provides sysfs interface for listing registered clocksources
794 sysfs_show_available_clocksources(struct sys_device *dev,
795 struct sysdev_attribute *attr,
798 struct clocksource *src;
801 mutex_lock(&clocksource_mutex);
802 list_for_each_entry(src, &clocksource_list, list) {
804 * Don't show non-HRES clocksource if the tick code is
805 * in one shot mode (highres=on or nohz=on)
807 if (!tick_oneshot_mode_active() ||
808 (src->flags & CLOCK_SOURCE_VALID_FOR_HRES))
809 count += snprintf(buf + count,
810 max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
813 mutex_unlock(&clocksource_mutex);
815 count += snprintf(buf + count,
816 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
824 static SYSDEV_ATTR(current_clocksource, 0644, sysfs_show_current_clocksources,
825 sysfs_override_clocksource);
827 static SYSDEV_ATTR(available_clocksource, 0444,
828 sysfs_show_available_clocksources, NULL);
830 static struct sysdev_class clocksource_sysclass = {
831 .name = "clocksource",
834 static struct sys_device device_clocksource = {
836 .cls = &clocksource_sysclass,
839 static int __init init_clocksource_sysfs(void)
841 int error = sysdev_class_register(&clocksource_sysclass);
844 error = sysdev_register(&device_clocksource);
846 error = sysdev_create_file(
848 &attr_current_clocksource);
850 error = sysdev_create_file(
852 &attr_available_clocksource);
856 device_initcall(init_clocksource_sysfs);
857 #endif /* CONFIG_SYSFS */
860 * boot_override_clocksource - boot clock override
861 * @str: override name
863 * Takes a clocksource= boot argument and uses it
864 * as the clocksource override name.
866 static int __init boot_override_clocksource(char* str)
868 mutex_lock(&clocksource_mutex);
870 strlcpy(override_name, str, sizeof(override_name));
871 mutex_unlock(&clocksource_mutex);
875 __setup("clocksource=", boot_override_clocksource);
878 * boot_override_clock - Compatibility layer for deprecated boot option
879 * @str: override name
881 * DEPRECATED! Takes a clock= boot argument and uses it
882 * as the clocksource override name
884 static int __init boot_override_clock(char* str)
886 if (!strcmp(str, "pmtmr")) {
887 printk("Warning: clock=pmtmr is deprecated. "
888 "Use clocksource=acpi_pm.\n");
889 return boot_override_clocksource("acpi_pm");
891 printk("Warning! clock= boot option is deprecated. "
892 "Use clocksource=xyz\n");
893 return boot_override_clocksource(str);
896 __setup("clock=", boot_override_clock);