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
24 * o get rid of clocksource_jiffies extern
27 #include <linux/clocksource.h>
28 #include <linux/sysdev.h>
29 #include <linux/init.h>
30 #include <linux/module.h>
31 #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */
32 #include <linux/tick.h>
34 /* XXX - Would like a better way for initializing curr_clocksource */
35 extern struct clocksource clocksource_jiffies
;
37 /*[Clocksource internal variables]---------
39 * currently selected clocksource. Initialized to clocksource_jiffies.
41 * pending next selected clocksource.
43 * linked list with the registered clocksources
45 * protects manipulations to curr_clocksource and next_clocksource
46 * and the clocksource_list
48 * Name of the user-specified clocksource.
50 static struct clocksource
*curr_clocksource
= &clocksource_jiffies
;
51 static struct clocksource
*next_clocksource
;
52 static struct clocksource
*clocksource_override
;
53 static LIST_HEAD(clocksource_list
);
54 static DEFINE_SPINLOCK(clocksource_lock
);
55 static char override_name
[32];
56 static int finished_booting
;
58 /* clocksource_done_booting - Called near the end of core bootup
60 * Hack to avoid lots of clocksource churn at boot time.
61 * We use fs_initcall because we want this to start before
62 * device_initcall but after subsys_initcall.
64 static int __init
clocksource_done_booting(void)
69 fs_initcall(clocksource_done_booting
);
71 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
72 static LIST_HEAD(watchdog_list
);
73 static struct clocksource
*watchdog
;
74 static struct timer_list watchdog_timer
;
75 static DEFINE_SPINLOCK(watchdog_lock
);
76 static cycle_t watchdog_last
;
78 * Interval: 0.5sec Treshold: 0.0625s
80 #define WATCHDOG_INTERVAL (HZ >> 1)
81 #define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4)
83 static void clocksource_ratewd(struct clocksource
*cs
, int64_t delta
)
85 if (delta
> -WATCHDOG_TRESHOLD
&& delta
< WATCHDOG_TRESHOLD
)
88 printk(KERN_WARNING
"Clocksource %s unstable (delta = %Ld ns)\n",
90 cs
->flags
&= ~(CLOCK_SOURCE_VALID_FOR_HRES
| CLOCK_SOURCE_WATCHDOG
);
91 clocksource_change_rating(cs
, 0);
92 cs
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
93 list_del(&cs
->wd_list
);
96 static void clocksource_watchdog(unsigned long data
)
98 struct clocksource
*cs
, *tmp
;
100 int64_t wd_nsec
, cs_nsec
;
102 spin_lock(&watchdog_lock
);
104 wdnow
= watchdog
->read();
105 wd_nsec
= cyc2ns(watchdog
, (wdnow
- watchdog_last
) & watchdog
->mask
);
106 watchdog_last
= wdnow
;
108 list_for_each_entry_safe(cs
, tmp
, &watchdog_list
, wd_list
) {
111 if (!(cs
->flags
& CLOCK_SOURCE_WATCHDOG
)) {
112 if ((cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
) &&
113 (watchdog
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)) {
114 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
116 * We just marked the clocksource as
117 * highres-capable, notify the rest of the
118 * system as well so that we transition
119 * into high-res mode:
123 cs
->flags
|= CLOCK_SOURCE_WATCHDOG
;
126 cs_nsec
= cyc2ns(cs
, (csnow
- cs
->wd_last
) & cs
->mask
);
128 /* Check the delta. Might remove from the list ! */
129 clocksource_ratewd(cs
, cs_nsec
- wd_nsec
);
133 if (!list_empty(&watchdog_list
)) {
134 __mod_timer(&watchdog_timer
,
135 watchdog_timer
.expires
+ WATCHDOG_INTERVAL
);
137 spin_unlock(&watchdog_lock
);
139 static void clocksource_check_watchdog(struct clocksource
*cs
)
141 struct clocksource
*cse
;
144 spin_lock_irqsave(&watchdog_lock
, flags
);
145 if (cs
->flags
& CLOCK_SOURCE_MUST_VERIFY
) {
146 int started
= !list_empty(&watchdog_list
);
148 list_add(&cs
->wd_list
, &watchdog_list
);
149 if (!started
&& watchdog
) {
150 watchdog_last
= watchdog
->read();
151 watchdog_timer
.expires
= jiffies
+ WATCHDOG_INTERVAL
;
152 add_timer(&watchdog_timer
);
154 } else if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
) {
155 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
157 if (!watchdog
|| cs
->rating
> watchdog
->rating
) {
159 del_timer(&watchdog_timer
);
161 init_timer(&watchdog_timer
);
162 watchdog_timer
.function
= clocksource_watchdog
;
164 /* Reset watchdog cycles */
165 list_for_each_entry(cse
, &watchdog_list
, wd_list
)
166 cse
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
167 /* Start if list is not empty */
168 if (!list_empty(&watchdog_list
)) {
169 watchdog_last
= watchdog
->read();
170 watchdog_timer
.expires
=
171 jiffies
+ WATCHDOG_INTERVAL
;
172 add_timer(&watchdog_timer
);
176 spin_unlock_irqrestore(&watchdog_lock
, flags
);
179 static void clocksource_check_watchdog(struct clocksource
*cs
)
181 if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)
182 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
187 * clocksource_get_next - Returns the selected clocksource
190 struct clocksource
*clocksource_get_next(void)
194 spin_lock_irqsave(&clocksource_lock
, flags
);
195 if (next_clocksource
&& finished_booting
) {
196 curr_clocksource
= next_clocksource
;
197 next_clocksource
= NULL
;
199 spin_unlock_irqrestore(&clocksource_lock
, flags
);
201 return curr_clocksource
;
205 * select_clocksource - Selects the best registered clocksource.
207 * Private function. Must hold clocksource_lock when called.
209 * Select the clocksource with the best rating, or the clocksource,
210 * which is selected by userspace override.
212 static struct clocksource
*select_clocksource(void)
214 struct clocksource
*next
;
216 if (list_empty(&clocksource_list
))
219 if (clocksource_override
)
220 next
= clocksource_override
;
222 next
= list_entry(clocksource_list
.next
, struct clocksource
,
225 if (next
== curr_clocksource
)
232 * Enqueue the clocksource sorted by rating
234 static int clocksource_enqueue(struct clocksource
*c
)
236 struct list_head
*tmp
, *entry
= &clocksource_list
;
238 list_for_each(tmp
, &clocksource_list
) {
239 struct clocksource
*cs
;
241 cs
= list_entry(tmp
, struct clocksource
, list
);
244 /* Keep track of the place, where to insert */
245 if (cs
->rating
>= c
->rating
)
248 list_add(&c
->list
, entry
);
250 if (strlen(c
->name
) == strlen(override_name
) &&
251 !strcmp(c
->name
, override_name
))
252 clocksource_override
= c
;
258 * clocksource_register - Used to install new clocksources
259 * @t: clocksource to be registered
261 * Returns -EBUSY if registration fails, zero otherwise.
263 int clocksource_register(struct clocksource
*c
)
268 spin_lock_irqsave(&clocksource_lock
, flags
);
269 ret
= clocksource_enqueue(c
);
271 next_clocksource
= select_clocksource();
272 spin_unlock_irqrestore(&clocksource_lock
, flags
);
274 clocksource_check_watchdog(c
);
277 EXPORT_SYMBOL(clocksource_register
);
280 * clocksource_change_rating - Change the rating of a registered clocksource
283 void clocksource_change_rating(struct clocksource
*cs
, int rating
)
287 spin_lock_irqsave(&clocksource_lock
, flags
);
290 clocksource_enqueue(cs
);
291 next_clocksource
= select_clocksource();
292 spin_unlock_irqrestore(&clocksource_lock
, flags
);
297 * sysfs_show_current_clocksources - sysfs interface for current clocksource
299 * @buf: char buffer to be filled with clocksource list
301 * Provides sysfs interface for listing current clocksource.
304 sysfs_show_current_clocksources(struct sys_device
*dev
, char *buf
)
308 spin_lock_irq(&clocksource_lock
);
309 curr
+= sprintf(curr
, "%s ", curr_clocksource
->name
);
310 spin_unlock_irq(&clocksource_lock
);
312 curr
+= sprintf(curr
, "\n");
318 * sysfs_override_clocksource - interface for manually overriding clocksource
320 * @buf: name of override clocksource
321 * @count: length of buffer
323 * Takes input from sysfs interface for manually overriding the default
324 * clocksource selction.
326 static ssize_t
sysfs_override_clocksource(struct sys_device
*dev
,
327 const char *buf
, size_t count
)
329 struct clocksource
*ovr
= NULL
;
330 struct list_head
*tmp
;
334 /* strings from sysfs write are not 0 terminated! */
335 if (count
>= sizeof(override_name
))
339 if (buf
[count
-1] == '\n')
342 spin_lock_irq(&clocksource_lock
);
345 memcpy(override_name
, buf
, count
);
346 override_name
[count
] = 0;
348 len
= strlen(override_name
);
350 ovr
= clocksource_override
;
351 /* try to select it: */
352 list_for_each(tmp
, &clocksource_list
) {
353 struct clocksource
*cs
;
355 cs
= list_entry(tmp
, struct clocksource
, list
);
356 if (strlen(cs
->name
) == len
&&
357 !strcmp(cs
->name
, override_name
))
362 /* Reselect, when the override name has changed */
363 if (ovr
!= clocksource_override
) {
364 clocksource_override
= ovr
;
365 next_clocksource
= select_clocksource();
368 spin_unlock_irq(&clocksource_lock
);
374 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
376 * @buf: char buffer to be filled with clocksource list
378 * Provides sysfs interface for listing registered clocksources
381 sysfs_show_available_clocksources(struct sys_device
*dev
, char *buf
)
383 struct list_head
*tmp
;
386 spin_lock_irq(&clocksource_lock
);
387 list_for_each(tmp
, &clocksource_list
) {
388 struct clocksource
*src
;
390 src
= list_entry(tmp
, struct clocksource
, list
);
391 curr
+= sprintf(curr
, "%s ", src
->name
);
393 spin_unlock_irq(&clocksource_lock
);
395 curr
+= sprintf(curr
, "\n");
403 static SYSDEV_ATTR(current_clocksource
, 0600, sysfs_show_current_clocksources
,
404 sysfs_override_clocksource
);
406 static SYSDEV_ATTR(available_clocksource
, 0600,
407 sysfs_show_available_clocksources
, NULL
);
409 static struct sysdev_class clocksource_sysclass
= {
410 set_kset_name("clocksource"),
413 static struct sys_device device_clocksource
= {
415 .cls
= &clocksource_sysclass
,
418 static int __init
init_clocksource_sysfs(void)
420 int error
= sysdev_class_register(&clocksource_sysclass
);
423 error
= sysdev_register(&device_clocksource
);
425 error
= sysdev_create_file(
427 &attr_current_clocksource
);
429 error
= sysdev_create_file(
431 &attr_available_clocksource
);
435 device_initcall(init_clocksource_sysfs
);
436 #endif /* CONFIG_SYSFS */
439 * boot_override_clocksource - boot clock override
440 * @str: override name
442 * Takes a clocksource= boot argument and uses it
443 * as the clocksource override name.
445 static int __init
boot_override_clocksource(char* str
)
448 spin_lock_irqsave(&clocksource_lock
, flags
);
450 strlcpy(override_name
, str
, sizeof(override_name
));
451 spin_unlock_irqrestore(&clocksource_lock
, flags
);
455 __setup("clocksource=", boot_override_clocksource
);
458 * boot_override_clock - Compatibility layer for deprecated boot option
459 * @str: override name
461 * DEPRECATED! Takes a clock= boot argument and uses it
462 * as the clocksource override name
464 static int __init
boot_override_clock(char* str
)
466 if (!strcmp(str
, "pmtmr")) {
467 printk("Warning: clock=pmtmr is deprecated. "
468 "Use clocksource=acpi_pm.\n");
469 return boot_override_clocksource("acpi_pm");
471 printk("Warning! clock= boot option is deprecated. "
472 "Use clocksource=xyz\n");
473 return boot_override_clocksource(str
);
476 __setup("clock=", boot_override_clock
);