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/device.h>
27 #include <linux/clocksource.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 #include "tick-internal.h"
35 #include "timekeeping_internal.h"
37 void timecounter_init(struct timecounter
*tc
,
38 const struct cyclecounter
*cc
,
42 tc
->cycle_last
= cc
->read(cc
);
43 tc
->nsec
= start_tstamp
;
45 EXPORT_SYMBOL_GPL(timecounter_init
);
48 * timecounter_read_delta - get nanoseconds since last call of this function
49 * @tc: Pointer to time counter
51 * When the underlying cycle counter runs over, this will be handled
52 * correctly as long as it does not run over more than once between
55 * The first call to this function for a new time counter initializes
56 * the time tracking and returns an undefined result.
58 static u64
timecounter_read_delta(struct timecounter
*tc
)
60 cycle_t cycle_now
, cycle_delta
;
63 /* read cycle counter: */
64 cycle_now
= tc
->cc
->read(tc
->cc
);
66 /* calculate the delta since the last timecounter_read_delta(): */
67 cycle_delta
= (cycle_now
- tc
->cycle_last
) & tc
->cc
->mask
;
69 /* convert to nanoseconds: */
70 ns_offset
= cyclecounter_cyc2ns(tc
->cc
, cycle_delta
);
72 /* update time stamp of timecounter_read_delta() call: */
73 tc
->cycle_last
= cycle_now
;
78 u64
timecounter_read(struct timecounter
*tc
)
82 /* increment time by nanoseconds since last call */
83 nsec
= timecounter_read_delta(tc
);
89 EXPORT_SYMBOL_GPL(timecounter_read
);
91 u64
timecounter_cyc2time(struct timecounter
*tc
,
94 u64 cycle_delta
= (cycle_tstamp
- tc
->cycle_last
) & tc
->cc
->mask
;
98 * Instead of always treating cycle_tstamp as more recent
99 * than tc->cycle_last, detect when it is too far in the
100 * future and treat it as old time stamp instead.
102 if (cycle_delta
> tc
->cc
->mask
/ 2) {
103 cycle_delta
= (tc
->cycle_last
- cycle_tstamp
) & tc
->cc
->mask
;
104 nsec
= tc
->nsec
- cyclecounter_cyc2ns(tc
->cc
, cycle_delta
);
106 nsec
= cyclecounter_cyc2ns(tc
->cc
, cycle_delta
) + tc
->nsec
;
111 EXPORT_SYMBOL_GPL(timecounter_cyc2time
);
114 * clocks_calc_mult_shift - calculate mult/shift factors for scaled math of clocks
115 * @mult: pointer to mult variable
116 * @shift: pointer to shift variable
117 * @from: frequency to convert from
118 * @to: frequency to convert to
119 * @maxsec: guaranteed runtime conversion range in seconds
121 * The function evaluates the shift/mult pair for the scaled math
122 * operations of clocksources and clockevents.
124 * @to and @from are frequency values in HZ. For clock sources @to is
125 * NSEC_PER_SEC == 1GHz and @from is the counter frequency. For clock
126 * event @to is the counter frequency and @from is NSEC_PER_SEC.
128 * The @maxsec conversion range argument controls the time frame in
129 * seconds which must be covered by the runtime conversion with the
130 * calculated mult and shift factors. This guarantees that no 64bit
131 * overflow happens when the input value of the conversion is
132 * multiplied with the calculated mult factor. Larger ranges may
133 * reduce the conversion accuracy by chosing smaller mult and shift
137 clocks_calc_mult_shift(u32
*mult
, u32
*shift
, u32 from
, u32 to
, u32 maxsec
)
143 * Calculate the shift factor which is limiting the conversion
146 tmp
= ((u64
)maxsec
* from
) >> 32;
153 * Find the conversion shift/mult pair which has the best
154 * accuracy and fits the maxsec conversion range:
156 for (sft
= 32; sft
> 0; sft
--) {
157 tmp
= (u64
) to
<< sft
;
160 if ((tmp
>> sftacc
) == 0)
167 /*[Clocksource internal variables]---------
169 * currently selected clocksource.
171 * linked list with the registered clocksources
173 * protects manipulations to curr_clocksource and the clocksource_list
175 * Name of the user-specified clocksource.
177 static struct clocksource
*curr_clocksource
;
178 static LIST_HEAD(clocksource_list
);
179 static DEFINE_MUTEX(clocksource_mutex
);
180 static char override_name
[CS_NAME_LEN
];
181 static int finished_booting
;
183 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
184 static void clocksource_watchdog_work(struct work_struct
*work
);
185 static void clocksource_select(void);
187 static LIST_HEAD(watchdog_list
);
188 static struct clocksource
*watchdog
;
189 static struct timer_list watchdog_timer
;
190 static DECLARE_WORK(watchdog_work
, clocksource_watchdog_work
);
191 static DEFINE_SPINLOCK(watchdog_lock
);
192 static int watchdog_running
;
193 static atomic_t watchdog_reset_pending
;
195 static int clocksource_watchdog_kthread(void *data
);
196 static void __clocksource_change_rating(struct clocksource
*cs
, int rating
);
199 * Interval: 0.5sec Threshold: 0.0625s
201 #define WATCHDOG_INTERVAL (HZ >> 1)
202 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
204 static void clocksource_watchdog_work(struct work_struct
*work
)
207 * If kthread_run fails the next watchdog scan over the
208 * watchdog_list will find the unstable clock again.
210 kthread_run(clocksource_watchdog_kthread
, NULL
, "kwatchdog");
213 static void __clocksource_unstable(struct clocksource
*cs
)
215 cs
->flags
&= ~(CLOCK_SOURCE_VALID_FOR_HRES
| CLOCK_SOURCE_WATCHDOG
);
216 cs
->flags
|= CLOCK_SOURCE_UNSTABLE
;
217 if (finished_booting
)
218 schedule_work(&watchdog_work
);
221 static void clocksource_unstable(struct clocksource
*cs
, int64_t delta
)
223 printk(KERN_WARNING
"Clocksource %s unstable (delta = %Ld ns)\n",
225 __clocksource_unstable(cs
);
229 * clocksource_mark_unstable - mark clocksource unstable via watchdog
230 * @cs: clocksource to be marked unstable
232 * This function is called instead of clocksource_change_rating from
233 * cpu hotplug code to avoid a deadlock between the clocksource mutex
234 * and the cpu hotplug mutex. It defers the update of the clocksource
235 * to the watchdog thread.
237 void clocksource_mark_unstable(struct clocksource
*cs
)
241 spin_lock_irqsave(&watchdog_lock
, flags
);
242 if (!(cs
->flags
& CLOCK_SOURCE_UNSTABLE
)) {
243 if (list_empty(&cs
->wd_list
))
244 list_add(&cs
->wd_list
, &watchdog_list
);
245 __clocksource_unstable(cs
);
247 spin_unlock_irqrestore(&watchdog_lock
, flags
);
250 static void clocksource_watchdog(unsigned long data
)
252 struct clocksource
*cs
;
253 cycle_t csnow
, wdnow
, delta
;
254 int64_t wd_nsec
, cs_nsec
;
255 int next_cpu
, reset_pending
;
257 spin_lock(&watchdog_lock
);
258 if (!watchdog_running
)
261 reset_pending
= atomic_read(&watchdog_reset_pending
);
263 list_for_each_entry(cs
, &watchdog_list
, wd_list
) {
265 /* Clocksource already marked unstable? */
266 if (cs
->flags
& CLOCK_SOURCE_UNSTABLE
) {
267 if (finished_booting
)
268 schedule_work(&watchdog_work
);
273 csnow
= cs
->read(cs
);
274 wdnow
= watchdog
->read(watchdog
);
277 /* Clocksource initialized ? */
278 if (!(cs
->flags
& CLOCK_SOURCE_WATCHDOG
) ||
279 atomic_read(&watchdog_reset_pending
)) {
280 cs
->flags
|= CLOCK_SOURCE_WATCHDOG
;
286 delta
= clocksource_delta(wdnow
, cs
->wd_last
, watchdog
->mask
);
287 wd_nsec
= clocksource_cyc2ns(delta
, watchdog
->mult
,
290 delta
= clocksource_delta(csnow
, cs
->cs_last
, cs
->mask
);
291 cs_nsec
= clocksource_cyc2ns(delta
, cs
->mult
, cs
->shift
);
295 if (atomic_read(&watchdog_reset_pending
))
298 /* Check the deviation from the watchdog clocksource. */
299 if ((abs(cs_nsec
- wd_nsec
) > WATCHDOG_THRESHOLD
)) {
300 clocksource_unstable(cs
, cs_nsec
- wd_nsec
);
304 if (!(cs
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
) &&
305 (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
) &&
306 (watchdog
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)) {
307 /* Mark it valid for high-res. */
308 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
311 * clocksource_done_booting() will sort it if
312 * finished_booting is not set yet.
314 if (!finished_booting
)
318 * If this is not the current clocksource let
319 * the watchdog thread reselect it. Due to the
320 * change to high res this clocksource might
321 * be preferred now. If it is the current
322 * clocksource let the tick code know about
325 if (cs
!= curr_clocksource
) {
326 cs
->flags
|= CLOCK_SOURCE_RESELECT
;
327 schedule_work(&watchdog_work
);
335 * We only clear the watchdog_reset_pending, when we did a
336 * full cycle through all clocksources.
339 atomic_dec(&watchdog_reset_pending
);
342 * Cycle through CPUs to check if the CPUs stay synchronized
345 next_cpu
= cpumask_next(raw_smp_processor_id(), cpu_online_mask
);
346 if (next_cpu
>= nr_cpu_ids
)
347 next_cpu
= cpumask_first(cpu_online_mask
);
348 watchdog_timer
.expires
+= WATCHDOG_INTERVAL
;
349 add_timer_on(&watchdog_timer
, next_cpu
);
351 spin_unlock(&watchdog_lock
);
354 static inline void clocksource_start_watchdog(void)
356 if (watchdog_running
|| !watchdog
|| list_empty(&watchdog_list
))
358 init_timer(&watchdog_timer
);
359 watchdog_timer
.function
= clocksource_watchdog
;
360 watchdog_timer
.expires
= jiffies
+ WATCHDOG_INTERVAL
;
361 add_timer_on(&watchdog_timer
, cpumask_first(cpu_online_mask
));
362 watchdog_running
= 1;
365 static inline void clocksource_stop_watchdog(void)
367 if (!watchdog_running
|| (watchdog
&& !list_empty(&watchdog_list
)))
369 del_timer(&watchdog_timer
);
370 watchdog_running
= 0;
373 static inline void clocksource_reset_watchdog(void)
375 struct clocksource
*cs
;
377 list_for_each_entry(cs
, &watchdog_list
, wd_list
)
378 cs
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
381 static void clocksource_resume_watchdog(void)
383 atomic_inc(&watchdog_reset_pending
);
386 static void clocksource_enqueue_watchdog(struct clocksource
*cs
)
390 spin_lock_irqsave(&watchdog_lock
, flags
);
391 if (cs
->flags
& CLOCK_SOURCE_MUST_VERIFY
) {
392 /* cs is a clocksource to be watched. */
393 list_add(&cs
->wd_list
, &watchdog_list
);
394 cs
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
396 /* cs is a watchdog. */
397 if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)
398 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
399 /* Pick the best watchdog. */
400 if (!watchdog
|| cs
->rating
> watchdog
->rating
) {
402 /* Reset watchdog cycles */
403 clocksource_reset_watchdog();
406 /* Check if the watchdog timer needs to be started. */
407 clocksource_start_watchdog();
408 spin_unlock_irqrestore(&watchdog_lock
, flags
);
411 static void clocksource_dequeue_watchdog(struct clocksource
*cs
)
415 spin_lock_irqsave(&watchdog_lock
, flags
);
416 if (cs
!= watchdog
) {
417 if (cs
->flags
& CLOCK_SOURCE_MUST_VERIFY
) {
418 /* cs is a watched clocksource. */
419 list_del_init(&cs
->wd_list
);
420 /* Check if the watchdog timer needs to be stopped. */
421 clocksource_stop_watchdog();
424 spin_unlock_irqrestore(&watchdog_lock
, flags
);
427 static int __clocksource_watchdog_kthread(void)
429 struct clocksource
*cs
, *tmp
;
434 spin_lock_irqsave(&watchdog_lock
, flags
);
435 list_for_each_entry_safe(cs
, tmp
, &watchdog_list
, wd_list
) {
436 if (cs
->flags
& CLOCK_SOURCE_UNSTABLE
) {
437 list_del_init(&cs
->wd_list
);
438 list_add(&cs
->wd_list
, &unstable
);
441 if (cs
->flags
& CLOCK_SOURCE_RESELECT
) {
442 cs
->flags
&= ~CLOCK_SOURCE_RESELECT
;
446 /* Check if the watchdog timer needs to be stopped. */
447 clocksource_stop_watchdog();
448 spin_unlock_irqrestore(&watchdog_lock
, flags
);
450 /* Needs to be done outside of watchdog lock */
451 list_for_each_entry_safe(cs
, tmp
, &unstable
, wd_list
) {
452 list_del_init(&cs
->wd_list
);
453 __clocksource_change_rating(cs
, 0);
458 static int clocksource_watchdog_kthread(void *data
)
460 mutex_lock(&clocksource_mutex
);
461 if (__clocksource_watchdog_kthread())
462 clocksource_select();
463 mutex_unlock(&clocksource_mutex
);
467 static bool clocksource_is_watchdog(struct clocksource
*cs
)
469 return cs
== watchdog
;
472 #else /* CONFIG_CLOCKSOURCE_WATCHDOG */
474 static void clocksource_enqueue_watchdog(struct clocksource
*cs
)
476 if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)
477 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
480 static inline void clocksource_dequeue_watchdog(struct clocksource
*cs
) { }
481 static inline void clocksource_resume_watchdog(void) { }
482 static inline int __clocksource_watchdog_kthread(void) { return 0; }
483 static bool clocksource_is_watchdog(struct clocksource
*cs
) { return false; }
484 void clocksource_mark_unstable(struct clocksource
*cs
) { }
486 #endif /* CONFIG_CLOCKSOURCE_WATCHDOG */
489 * clocksource_suspend - suspend the clocksource(s)
491 void clocksource_suspend(void)
493 struct clocksource
*cs
;
495 list_for_each_entry_reverse(cs
, &clocksource_list
, list
)
501 * clocksource_resume - resume the clocksource(s)
503 void clocksource_resume(void)
505 struct clocksource
*cs
;
507 list_for_each_entry(cs
, &clocksource_list
, list
)
511 clocksource_resume_watchdog();
515 * clocksource_touch_watchdog - Update watchdog
517 * Update the watchdog after exception contexts such as kgdb so as not
518 * to incorrectly trip the watchdog. This might fail when the kernel
519 * was stopped in code which holds watchdog_lock.
521 void clocksource_touch_watchdog(void)
523 clocksource_resume_watchdog();
527 * clocksource_max_adjustment- Returns max adjustment amount
528 * @cs: Pointer to clocksource
531 static u32
clocksource_max_adjustment(struct clocksource
*cs
)
535 * We won't try to correct for more than 11% adjustments (110,000 ppm),
537 ret
= (u64
)cs
->mult
* 11;
543 * clocks_calc_max_nsecs - Returns maximum nanoseconds that can be converted
544 * @mult: cycle to nanosecond multiplier
545 * @shift: cycle to nanosecond divisor (power of two)
546 * @maxadj: maximum adjustment value to mult (~11%)
547 * @mask: bitmask for two's complement subtraction of non 64 bit counters
549 u64
clocks_calc_max_nsecs(u32 mult
, u32 shift
, u32 maxadj
, u64 mask
)
551 u64 max_nsecs
, max_cycles
;
554 * Calculate the maximum number of cycles that we can pass to the
555 * cyc2ns function without overflowing a 64-bit signed result. The
556 * maximum number of cycles is equal to ULLONG_MAX/(mult+maxadj)
557 * which is equivalent to the below.
558 * max_cycles < (2^63)/(mult + maxadj)
559 * max_cycles < 2^(log2((2^63)/(mult + maxadj)))
560 * max_cycles < 2^(log2(2^63) - log2(mult + maxadj))
561 * max_cycles < 2^(63 - log2(mult + maxadj))
562 * max_cycles < 1 << (63 - log2(mult + maxadj))
563 * Please note that we add 1 to the result of the log2 to account for
564 * any rounding errors, ensure the above inequality is satisfied and
565 * no overflow will occur.
567 max_cycles
= 1ULL << (63 - (ilog2(mult
+ maxadj
) + 1));
570 * The actual maximum number of cycles we can defer the clocksource is
571 * determined by the minimum of max_cycles and mask.
572 * Note: Here we subtract the maxadj to make sure we don't sleep for
573 * too long if there's a large negative adjustment.
575 max_cycles
= min(max_cycles
, mask
);
576 max_nsecs
= clocksource_cyc2ns(max_cycles
, mult
- maxadj
, shift
);
582 * clocksource_max_deferment - Returns max time the clocksource can be deferred
583 * @cs: Pointer to clocksource
586 static u64
clocksource_max_deferment(struct clocksource
*cs
)
590 max_nsecs
= clocks_calc_max_nsecs(cs
->mult
, cs
->shift
, cs
->maxadj
,
593 * To ensure that the clocksource does not wrap whilst we are idle,
594 * limit the time the clocksource can be deferred by 12.5%. Please
595 * note a margin of 12.5% is used because this can be computed with
596 * a shift, versus say 10% which would require division.
598 return max_nsecs
- (max_nsecs
>> 3);
601 #ifndef CONFIG_ARCH_USES_GETTIMEOFFSET
603 static struct clocksource
*clocksource_find_best(bool oneshot
, bool skipcur
)
605 struct clocksource
*cs
;
607 if (!finished_booting
|| list_empty(&clocksource_list
))
611 * We pick the clocksource with the highest rating. If oneshot
612 * mode is active, we pick the highres valid clocksource with
615 list_for_each_entry(cs
, &clocksource_list
, list
) {
616 if (skipcur
&& cs
== curr_clocksource
)
618 if (oneshot
&& !(cs
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
))
625 static void __clocksource_select(bool skipcur
)
627 bool oneshot
= tick_oneshot_mode_active();
628 struct clocksource
*best
, *cs
;
630 /* Find the best suitable clocksource */
631 best
= clocksource_find_best(oneshot
, skipcur
);
635 /* Check for the override clocksource. */
636 list_for_each_entry(cs
, &clocksource_list
, list
) {
637 if (skipcur
&& cs
== curr_clocksource
)
639 if (strcmp(cs
->name
, override_name
) != 0)
642 * Check to make sure we don't switch to a non-highres
643 * capable clocksource if the tick code is in oneshot
644 * mode (highres or nohz)
646 if (!(cs
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
) && oneshot
) {
647 /* Override clocksource cannot be used. */
648 printk(KERN_WARNING
"Override clocksource %s is not "
649 "HRT compatible. Cannot switch while in "
650 "HRT/NOHZ mode\n", cs
->name
);
651 override_name
[0] = 0;
653 /* Override clocksource can be used. */
658 if (curr_clocksource
!= best
&& !timekeeping_notify(best
)) {
659 pr_info("Switched to clocksource %s\n", best
->name
);
660 curr_clocksource
= best
;
665 * clocksource_select - Select the best clocksource available
667 * Private function. Must hold clocksource_mutex when called.
669 * Select the clocksource with the best rating, or the clocksource,
670 * which is selected by userspace override.
672 static void clocksource_select(void)
674 return __clocksource_select(false);
677 static void clocksource_select_fallback(void)
679 return __clocksource_select(true);
682 #else /* !CONFIG_ARCH_USES_GETTIMEOFFSET */
684 static inline void clocksource_select(void) { }
685 static inline void clocksource_select_fallback(void) { }
690 * clocksource_done_booting - Called near the end of core bootup
692 * Hack to avoid lots of clocksource churn at boot time.
693 * We use fs_initcall because we want this to start before
694 * device_initcall but after subsys_initcall.
696 static int __init
clocksource_done_booting(void)
698 mutex_lock(&clocksource_mutex
);
699 curr_clocksource
= clocksource_default_clock();
700 finished_booting
= 1;
702 * Run the watchdog first to eliminate unstable clock sources
704 __clocksource_watchdog_kthread();
705 clocksource_select();
706 mutex_unlock(&clocksource_mutex
);
709 fs_initcall(clocksource_done_booting
);
712 * Enqueue the clocksource sorted by rating
714 static void clocksource_enqueue(struct clocksource
*cs
)
716 struct list_head
*entry
= &clocksource_list
;
717 struct clocksource
*tmp
;
719 list_for_each_entry(tmp
, &clocksource_list
, list
)
720 /* Keep track of the place, where to insert */
721 if (tmp
->rating
>= cs
->rating
)
723 list_add(&cs
->list
, entry
);
727 * __clocksource_updatefreq_scale - Used update clocksource with new freq
728 * @cs: clocksource to be registered
729 * @scale: Scale factor multiplied against freq to get clocksource hz
730 * @freq: clocksource frequency (cycles per second) divided by scale
732 * This should only be called from the clocksource->enable() method.
734 * This *SHOULD NOT* be called directly! Please use the
735 * clocksource_updatefreq_hz() or clocksource_updatefreq_khz helper functions.
737 void __clocksource_updatefreq_scale(struct clocksource
*cs
, u32 scale
, u32 freq
)
741 * Calc the maximum number of seconds which we can run before
742 * wrapping around. For clocksources which have a mask > 32bit
743 * we need to limit the max sleep time to have a good
744 * conversion precision. 10 minutes is still a reasonable
745 * amount. That results in a shift value of 24 for a
746 * clocksource with mask >= 40bit and f >= 4GHz. That maps to
747 * ~ 0.06ppm granularity for NTP. We apply the same 12.5%
748 * margin as we do in clocksource_max_deferment()
750 sec
= (cs
->mask
- (cs
->mask
>> 3));
755 else if (sec
> 600 && cs
->mask
> UINT_MAX
)
758 clocks_calc_mult_shift(&cs
->mult
, &cs
->shift
, freq
,
759 NSEC_PER_SEC
/ scale
, sec
* scale
);
762 * for clocksources that have large mults, to avoid overflow.
763 * Since mult may be adjusted by ntp, add an safety extra margin
766 cs
->maxadj
= clocksource_max_adjustment(cs
);
767 while ((cs
->mult
+ cs
->maxadj
< cs
->mult
)
768 || (cs
->mult
- cs
->maxadj
> cs
->mult
)) {
771 cs
->maxadj
= clocksource_max_adjustment(cs
);
774 cs
->max_idle_ns
= clocksource_max_deferment(cs
);
776 EXPORT_SYMBOL_GPL(__clocksource_updatefreq_scale
);
779 * __clocksource_register_scale - Used to install new clocksources
780 * @cs: clocksource to be registered
781 * @scale: Scale factor multiplied against freq to get clocksource hz
782 * @freq: clocksource frequency (cycles per second) divided by scale
784 * Returns -EBUSY if registration fails, zero otherwise.
786 * This *SHOULD NOT* be called directly! Please use the
787 * clocksource_register_hz() or clocksource_register_khz helper functions.
789 int __clocksource_register_scale(struct clocksource
*cs
, u32 scale
, u32 freq
)
792 /* Initialize mult/shift and max_idle_ns */
793 __clocksource_updatefreq_scale(cs
, scale
, freq
);
795 /* Add clocksource to the clcoksource list */
796 mutex_lock(&clocksource_mutex
);
797 clocksource_enqueue(cs
);
798 clocksource_enqueue_watchdog(cs
);
799 clocksource_select();
800 mutex_unlock(&clocksource_mutex
);
803 EXPORT_SYMBOL_GPL(__clocksource_register_scale
);
807 * clocksource_register - Used to install new clocksources
808 * @cs: clocksource to be registered
810 * Returns -EBUSY if registration fails, zero otherwise.
812 int clocksource_register(struct clocksource
*cs
)
814 /* calculate max adjustment for given mult/shift */
815 cs
->maxadj
= clocksource_max_adjustment(cs
);
816 WARN_ONCE(cs
->mult
+ cs
->maxadj
< cs
->mult
,
817 "Clocksource %s might overflow on 11%% adjustment\n",
820 /* calculate max idle time permitted for this clocksource */
821 cs
->max_idle_ns
= clocksource_max_deferment(cs
);
823 mutex_lock(&clocksource_mutex
);
824 clocksource_enqueue(cs
);
825 clocksource_enqueue_watchdog(cs
);
826 clocksource_select();
827 mutex_unlock(&clocksource_mutex
);
830 EXPORT_SYMBOL(clocksource_register
);
832 static void __clocksource_change_rating(struct clocksource
*cs
, int rating
)
836 clocksource_enqueue(cs
);
840 * clocksource_change_rating - Change the rating of a registered clocksource
841 * @cs: clocksource to be changed
842 * @rating: new rating
844 void clocksource_change_rating(struct clocksource
*cs
, int rating
)
846 mutex_lock(&clocksource_mutex
);
847 __clocksource_change_rating(cs
, rating
);
848 clocksource_select();
849 mutex_unlock(&clocksource_mutex
);
851 EXPORT_SYMBOL(clocksource_change_rating
);
854 * Unbind clocksource @cs. Called with clocksource_mutex held
856 static int clocksource_unbind(struct clocksource
*cs
)
859 * I really can't convince myself to support this on hardware
860 * designed by lobotomized monkeys.
862 if (clocksource_is_watchdog(cs
))
865 if (cs
== curr_clocksource
) {
866 /* Select and try to install a replacement clock source */
867 clocksource_select_fallback();
868 if (curr_clocksource
== cs
)
871 clocksource_dequeue_watchdog(cs
);
872 list_del_init(&cs
->list
);
877 * clocksource_unregister - remove a registered clocksource
878 * @cs: clocksource to be unregistered
880 int clocksource_unregister(struct clocksource
*cs
)
884 mutex_lock(&clocksource_mutex
);
885 if (!list_empty(&cs
->list
))
886 ret
= clocksource_unbind(cs
);
887 mutex_unlock(&clocksource_mutex
);
890 EXPORT_SYMBOL(clocksource_unregister
);
894 * sysfs_show_current_clocksources - sysfs interface for current clocksource
897 * @buf: char buffer to be filled with clocksource list
899 * Provides sysfs interface for listing current clocksource.
902 sysfs_show_current_clocksources(struct device
*dev
,
903 struct device_attribute
*attr
, char *buf
)
907 mutex_lock(&clocksource_mutex
);
908 count
= snprintf(buf
, PAGE_SIZE
, "%s\n", curr_clocksource
->name
);
909 mutex_unlock(&clocksource_mutex
);
914 ssize_t
sysfs_get_uname(const char *buf
, char *dst
, size_t cnt
)
918 /* strings from sysfs write are not 0 terminated! */
919 if (!cnt
|| cnt
>= CS_NAME_LEN
)
923 if (buf
[cnt
-1] == '\n')
926 memcpy(dst
, buf
, cnt
);
932 * sysfs_override_clocksource - interface for manually overriding clocksource
935 * @buf: name of override clocksource
936 * @count: length of buffer
938 * Takes input from sysfs interface for manually overriding the default
939 * clocksource selection.
941 static ssize_t
sysfs_override_clocksource(struct device
*dev
,
942 struct device_attribute
*attr
,
943 const char *buf
, size_t count
)
947 mutex_lock(&clocksource_mutex
);
949 ret
= sysfs_get_uname(buf
, override_name
, count
);
951 clocksource_select();
953 mutex_unlock(&clocksource_mutex
);
959 * sysfs_unbind_current_clocksource - interface for manually unbinding clocksource
963 * @count: length of buffer
965 * Takes input from sysfs interface for manually unbinding a clocksource.
967 static ssize_t
sysfs_unbind_clocksource(struct device
*dev
,
968 struct device_attribute
*attr
,
969 const char *buf
, size_t count
)
971 struct clocksource
*cs
;
972 char name
[CS_NAME_LEN
];
975 ret
= sysfs_get_uname(buf
, name
, count
);
980 mutex_lock(&clocksource_mutex
);
981 list_for_each_entry(cs
, &clocksource_list
, list
) {
982 if (strcmp(cs
->name
, name
))
984 ret
= clocksource_unbind(cs
);
987 mutex_unlock(&clocksource_mutex
);
989 return ret
? ret
: count
;
993 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
996 * @buf: char buffer to be filled with clocksource list
998 * Provides sysfs interface for listing registered clocksources
1001 sysfs_show_available_clocksources(struct device
*dev
,
1002 struct device_attribute
*attr
,
1005 struct clocksource
*src
;
1008 mutex_lock(&clocksource_mutex
);
1009 list_for_each_entry(src
, &clocksource_list
, list
) {
1011 * Don't show non-HRES clocksource if the tick code is
1012 * in one shot mode (highres=on or nohz=on)
1014 if (!tick_oneshot_mode_active() ||
1015 (src
->flags
& CLOCK_SOURCE_VALID_FOR_HRES
))
1016 count
+= snprintf(buf
+ count
,
1017 max((ssize_t
)PAGE_SIZE
- count
, (ssize_t
)0),
1020 mutex_unlock(&clocksource_mutex
);
1022 count
+= snprintf(buf
+ count
,
1023 max((ssize_t
)PAGE_SIZE
- count
, (ssize_t
)0), "\n");
1031 static DEVICE_ATTR(current_clocksource
, 0644, sysfs_show_current_clocksources
,
1032 sysfs_override_clocksource
);
1034 static DEVICE_ATTR(unbind_clocksource
, 0200, NULL
, sysfs_unbind_clocksource
);
1036 static DEVICE_ATTR(available_clocksource
, 0444,
1037 sysfs_show_available_clocksources
, NULL
);
1039 static struct bus_type clocksource_subsys
= {
1040 .name
= "clocksource",
1041 .dev_name
= "clocksource",
1044 static struct device device_clocksource
= {
1046 .bus
= &clocksource_subsys
,
1049 static int __init
init_clocksource_sysfs(void)
1051 int error
= subsys_system_register(&clocksource_subsys
, NULL
);
1054 error
= device_register(&device_clocksource
);
1056 error
= device_create_file(
1057 &device_clocksource
,
1058 &dev_attr_current_clocksource
);
1060 error
= device_create_file(&device_clocksource
,
1061 &dev_attr_unbind_clocksource
);
1063 error
= device_create_file(
1064 &device_clocksource
,
1065 &dev_attr_available_clocksource
);
1069 device_initcall(init_clocksource_sysfs
);
1070 #endif /* CONFIG_SYSFS */
1073 * boot_override_clocksource - boot clock override
1074 * @str: override name
1076 * Takes a clocksource= boot argument and uses it
1077 * as the clocksource override name.
1079 static int __init
boot_override_clocksource(char* str
)
1081 mutex_lock(&clocksource_mutex
);
1083 strlcpy(override_name
, str
, sizeof(override_name
));
1084 mutex_unlock(&clocksource_mutex
);
1088 __setup("clocksource=", boot_override_clocksource
);
1091 * boot_override_clock - Compatibility layer for deprecated boot option
1092 * @str: override name
1094 * DEPRECATED! Takes a clock= boot argument and uses it
1095 * as the clocksource override name
1097 static int __init
boot_override_clock(char* str
)
1099 if (!strcmp(str
, "pmtmr")) {
1100 printk("Warning: clock=pmtmr is deprecated. "
1101 "Use clocksource=acpi_pm.\n");
1102 return boot_override_clocksource("acpi_pm");
1104 printk("Warning! clock= boot option is deprecated. "
1105 "Use clocksource=xyz\n");
1106 return boot_override_clocksource(str
);
1109 __setup("clock=", boot_override_clock
);