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 bootup
60 * Hack to avoid lots of clocksource churn at boot time
62 static int __init
clocksource_done_booting(void)
67 late_initcall(clocksource_done_booting
);
69 #ifdef CONFIG_CLOCKSOURCE_WATCHDOG
70 static LIST_HEAD(watchdog_list
);
71 static struct clocksource
*watchdog
;
72 static struct timer_list watchdog_timer
;
73 static DEFINE_SPINLOCK(watchdog_lock
);
74 static cycle_t watchdog_last
;
76 * Interval: 0.5sec Treshold: 0.0625s
78 #define WATCHDOG_INTERVAL (HZ >> 1)
79 #define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4)
81 static void clocksource_ratewd(struct clocksource
*cs
, int64_t delta
)
83 if (delta
> -WATCHDOG_TRESHOLD
&& delta
< WATCHDOG_TRESHOLD
)
86 printk(KERN_WARNING
"Clocksource %s unstable (delta = %Ld ns)\n",
88 cs
->flags
&= ~(CLOCK_SOURCE_VALID_FOR_HRES
| CLOCK_SOURCE_WATCHDOG
);
89 clocksource_change_rating(cs
, 0);
90 cs
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
91 list_del(&cs
->wd_list
);
94 static void clocksource_watchdog(unsigned long data
)
96 struct clocksource
*cs
, *tmp
;
98 int64_t wd_nsec
, cs_nsec
;
100 spin_lock(&watchdog_lock
);
102 wdnow
= watchdog
->read();
103 wd_nsec
= cyc2ns(watchdog
, (wdnow
- watchdog_last
) & watchdog
->mask
);
104 watchdog_last
= wdnow
;
106 list_for_each_entry_safe(cs
, tmp
, &watchdog_list
, wd_list
) {
109 if (!(cs
->flags
& CLOCK_SOURCE_WATCHDOG
)) {
110 if ((cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
) &&
111 (watchdog
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)) {
112 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
114 * We just marked the clocksource as
115 * highres-capable, notify the rest of the
116 * system as well so that we transition
117 * into high-res mode:
121 cs
->flags
|= CLOCK_SOURCE_WATCHDOG
;
124 cs_nsec
= cyc2ns(cs
, (csnow
- cs
->wd_last
) & cs
->mask
);
126 /* Check the delta. Might remove from the list ! */
127 clocksource_ratewd(cs
, cs_nsec
- wd_nsec
);
131 if (!list_empty(&watchdog_list
)) {
132 __mod_timer(&watchdog_timer
,
133 watchdog_timer
.expires
+ WATCHDOG_INTERVAL
);
135 spin_unlock(&watchdog_lock
);
137 static void clocksource_check_watchdog(struct clocksource
*cs
)
139 struct clocksource
*cse
;
142 spin_lock_irqsave(&watchdog_lock
, flags
);
143 if (cs
->flags
& CLOCK_SOURCE_MUST_VERIFY
) {
144 int started
= !list_empty(&watchdog_list
);
146 list_add(&cs
->wd_list
, &watchdog_list
);
147 if (!started
&& watchdog
) {
148 watchdog_last
= watchdog
->read();
149 watchdog_timer
.expires
= jiffies
+ WATCHDOG_INTERVAL
;
150 add_timer(&watchdog_timer
);
152 } else if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
) {
153 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
155 if (!watchdog
|| cs
->rating
> watchdog
->rating
) {
157 del_timer(&watchdog_timer
);
159 init_timer(&watchdog_timer
);
160 watchdog_timer
.function
= clocksource_watchdog
;
162 /* Reset watchdog cycles */
163 list_for_each_entry(cse
, &watchdog_list
, wd_list
)
164 cse
->flags
&= ~CLOCK_SOURCE_WATCHDOG
;
165 /* Start if list is not empty */
166 if (!list_empty(&watchdog_list
)) {
167 watchdog_last
= watchdog
->read();
168 watchdog_timer
.expires
=
169 jiffies
+ WATCHDOG_INTERVAL
;
170 add_timer(&watchdog_timer
);
174 spin_unlock_irqrestore(&watchdog_lock
, flags
);
177 static void clocksource_check_watchdog(struct clocksource
*cs
)
179 if (cs
->flags
& CLOCK_SOURCE_IS_CONTINUOUS
)
180 cs
->flags
|= CLOCK_SOURCE_VALID_FOR_HRES
;
185 * clocksource_get_next - Returns the selected clocksource
188 struct clocksource
*clocksource_get_next(void)
192 spin_lock_irqsave(&clocksource_lock
, flags
);
193 if (next_clocksource
&& finished_booting
) {
194 curr_clocksource
= next_clocksource
;
195 next_clocksource
= NULL
;
197 spin_unlock_irqrestore(&clocksource_lock
, flags
);
199 return curr_clocksource
;
203 * select_clocksource - Selects the best registered clocksource.
205 * Private function. Must hold clocksource_lock when called.
207 * Select the clocksource with the best rating, or the clocksource,
208 * which is selected by userspace override.
210 static struct clocksource
*select_clocksource(void)
212 struct clocksource
*next
;
214 if (list_empty(&clocksource_list
))
217 if (clocksource_override
)
218 next
= clocksource_override
;
220 next
= list_entry(clocksource_list
.next
, struct clocksource
,
223 if (next
== curr_clocksource
)
230 * Enqueue the clocksource sorted by rating
232 static int clocksource_enqueue(struct clocksource
*c
)
234 struct list_head
*tmp
, *entry
= &clocksource_list
;
236 list_for_each(tmp
, &clocksource_list
) {
237 struct clocksource
*cs
;
239 cs
= list_entry(tmp
, struct clocksource
, list
);
242 /* Keep track of the place, where to insert */
243 if (cs
->rating
>= c
->rating
)
246 list_add(&c
->list
, entry
);
248 if (strlen(c
->name
) == strlen(override_name
) &&
249 !strcmp(c
->name
, override_name
))
250 clocksource_override
= c
;
256 * clocksource_register - Used to install new clocksources
257 * @t: clocksource to be registered
259 * Returns -EBUSY if registration fails, zero otherwise.
261 int clocksource_register(struct clocksource
*c
)
266 spin_lock_irqsave(&clocksource_lock
, flags
);
267 ret
= clocksource_enqueue(c
);
269 next_clocksource
= select_clocksource();
270 spin_unlock_irqrestore(&clocksource_lock
, flags
);
272 clocksource_check_watchdog(c
);
275 EXPORT_SYMBOL(clocksource_register
);
278 * clocksource_change_rating - Change the rating of a registered clocksource
281 void clocksource_change_rating(struct clocksource
*cs
, int rating
)
285 spin_lock_irqsave(&clocksource_lock
, flags
);
288 clocksource_enqueue(cs
);
289 next_clocksource
= select_clocksource();
290 spin_unlock_irqrestore(&clocksource_lock
, flags
);
295 * sysfs_show_current_clocksources - sysfs interface for current clocksource
297 * @buf: char buffer to be filled with clocksource list
299 * Provides sysfs interface for listing current clocksource.
302 sysfs_show_current_clocksources(struct sys_device
*dev
, char *buf
)
306 spin_lock_irq(&clocksource_lock
);
307 curr
+= sprintf(curr
, "%s ", curr_clocksource
->name
);
308 spin_unlock_irq(&clocksource_lock
);
310 curr
+= sprintf(curr
, "\n");
316 * sysfs_override_clocksource - interface for manually overriding clocksource
318 * @buf: name of override clocksource
319 * @count: length of buffer
321 * Takes input from sysfs interface for manually overriding the default
322 * clocksource selction.
324 static ssize_t
sysfs_override_clocksource(struct sys_device
*dev
,
325 const char *buf
, size_t count
)
327 struct clocksource
*ovr
= NULL
;
328 struct list_head
*tmp
;
332 /* strings from sysfs write are not 0 terminated! */
333 if (count
>= sizeof(override_name
))
337 if (buf
[count
-1] == '\n')
340 spin_lock_irq(&clocksource_lock
);
343 memcpy(override_name
, buf
, count
);
344 override_name
[count
] = 0;
346 len
= strlen(override_name
);
348 ovr
= clocksource_override
;
349 /* try to select it: */
350 list_for_each(tmp
, &clocksource_list
) {
351 struct clocksource
*cs
;
353 cs
= list_entry(tmp
, struct clocksource
, list
);
354 if (strlen(cs
->name
) == len
&&
355 !strcmp(cs
->name
, override_name
))
360 /* Reselect, when the override name has changed */
361 if (ovr
!= clocksource_override
) {
362 clocksource_override
= ovr
;
363 next_clocksource
= select_clocksource();
366 spin_unlock_irq(&clocksource_lock
);
372 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
374 * @buf: char buffer to be filled with clocksource list
376 * Provides sysfs interface for listing registered clocksources
379 sysfs_show_available_clocksources(struct sys_device
*dev
, char *buf
)
381 struct list_head
*tmp
;
384 spin_lock_irq(&clocksource_lock
);
385 list_for_each(tmp
, &clocksource_list
) {
386 struct clocksource
*src
;
388 src
= list_entry(tmp
, struct clocksource
, list
);
389 curr
+= sprintf(curr
, "%s ", src
->name
);
391 spin_unlock_irq(&clocksource_lock
);
393 curr
+= sprintf(curr
, "\n");
401 static SYSDEV_ATTR(current_clocksource
, 0600, sysfs_show_current_clocksources
,
402 sysfs_override_clocksource
);
404 static SYSDEV_ATTR(available_clocksource
, 0600,
405 sysfs_show_available_clocksources
, NULL
);
407 static struct sysdev_class clocksource_sysclass
= {
408 set_kset_name("clocksource"),
411 static struct sys_device device_clocksource
= {
413 .cls
= &clocksource_sysclass
,
416 static int __init
init_clocksource_sysfs(void)
418 int error
= sysdev_class_register(&clocksource_sysclass
);
421 error
= sysdev_register(&device_clocksource
);
423 error
= sysdev_create_file(
425 &attr_current_clocksource
);
427 error
= sysdev_create_file(
429 &attr_available_clocksource
);
433 device_initcall(init_clocksource_sysfs
);
434 #endif /* CONFIG_SYSFS */
437 * boot_override_clocksource - boot clock override
438 * @str: override name
440 * Takes a clocksource= boot argument and uses it
441 * as the clocksource override name.
443 static int __init
boot_override_clocksource(char* str
)
446 spin_lock_irqsave(&clocksource_lock
, flags
);
448 strlcpy(override_name
, str
, sizeof(override_name
));
449 spin_unlock_irqrestore(&clocksource_lock
, flags
);
453 __setup("clocksource=", boot_override_clocksource
);
456 * boot_override_clock - Compatibility layer for deprecated boot option
457 * @str: override name
459 * DEPRECATED! Takes a clock= boot argument and uses it
460 * as the clocksource override name
462 static int __init
boot_override_clock(char* str
)
464 if (!strcmp(str
, "pmtmr")) {
465 printk("Warning: clock=pmtmr is deprecated. "
466 "Use clocksource=acpi_pm.\n");
467 return boot_override_clocksource("acpi_pm");
469 printk("Warning! clock= boot option is deprecated. "
470 "Use clocksource=xyz\n");
471 return boot_override_clocksource(str
);
474 __setup("clock=", boot_override_clock
);