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;
77 static unsigned long watchdog_resumed;
80 * Interval: 0.5sec Threshold: 0.0625s
82 #define WATCHDOG_INTERVAL (HZ >> 1)
83 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
85 static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
87 if (delta > -WATCHDOG_THRESHOLD && delta < WATCHDOG_THRESHOLD)
90 printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
92 cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
93 clocksource_change_rating(cs, 0);
94 list_del(&cs->wd_list);
97 static void clocksource_watchdog(unsigned long data)
99 struct clocksource *cs, *tmp;
100 cycle_t csnow, wdnow;
101 int64_t wd_nsec, cs_nsec;
104 spin_lock(&watchdog_lock);
106 resumed = test_and_clear_bit(0, &watchdog_resumed);
108 wdnow = watchdog->read();
109 wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
110 watchdog_last = wdnow;
112 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
115 if (unlikely(resumed)) {
121 if (!(cs->flags & CLOCK_SOURCE_WATCHDOG)) {
122 if ((cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) &&
123 (watchdog->flags & CLOCK_SOURCE_IS_CONTINUOUS)) {
124 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
126 * We just marked the clocksource as
127 * highres-capable, notify the rest of the
128 * system as well so that we transition
129 * into high-res mode:
133 cs->flags |= CLOCK_SOURCE_WATCHDOG;
136 cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
138 /* Check the delta. Might remove from the list ! */
139 clocksource_ratewd(cs, cs_nsec - wd_nsec);
143 if (!list_empty(&watchdog_list)) {
144 __mod_timer(&watchdog_timer,
145 watchdog_timer.expires + WATCHDOG_INTERVAL);
147 spin_unlock(&watchdog_lock);
149 static void clocksource_resume_watchdog(void)
151 set_bit(0, &watchdog_resumed);
154 static void clocksource_check_watchdog(struct clocksource *cs)
156 struct clocksource *cse;
159 spin_lock_irqsave(&watchdog_lock, flags);
160 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
161 int started = !list_empty(&watchdog_list);
163 list_add(&cs->wd_list, &watchdog_list);
164 if (!started && watchdog) {
165 watchdog_last = watchdog->read();
166 watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
167 add_timer(&watchdog_timer);
170 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
171 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
173 if (!watchdog || cs->rating > watchdog->rating) {
175 del_timer(&watchdog_timer);
177 init_timer(&watchdog_timer);
178 watchdog_timer.function = clocksource_watchdog;
180 /* Reset watchdog cycles */
181 list_for_each_entry(cse, &watchdog_list, wd_list)
182 cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
183 /* Start if list is not empty */
184 if (!list_empty(&watchdog_list)) {
185 watchdog_last = watchdog->read();
186 watchdog_timer.expires =
187 jiffies + WATCHDOG_INTERVAL;
188 add_timer(&watchdog_timer);
192 spin_unlock_irqrestore(&watchdog_lock, flags);
195 static void clocksource_check_watchdog(struct clocksource *cs)
197 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
198 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
201 static inline void clocksource_resume_watchdog(void) { }
205 * clocksource_resume - resume the clocksource(s)
207 void clocksource_resume(void)
209 struct clocksource *cs;
212 spin_lock_irqsave(&clocksource_lock, flags);
214 list_for_each_entry(cs, &clocksource_list, list) {
219 clocksource_resume_watchdog();
221 spin_unlock_irqrestore(&clocksource_lock, flags);
225 * clocksource_touch_watchdog - Update watchdog
227 * Update the watchdog after exception contexts such as kgdb so as not
228 * to incorrectly trip the watchdog.
231 void clocksource_touch_watchdog(void)
233 clocksource_resume_watchdog();
237 * clocksource_get_next - Returns the selected clocksource
240 struct clocksource *clocksource_get_next(void)
244 spin_lock_irqsave(&clocksource_lock, flags);
245 if (next_clocksource && finished_booting) {
246 curr_clocksource = next_clocksource;
247 next_clocksource = NULL;
249 spin_unlock_irqrestore(&clocksource_lock, flags);
251 return curr_clocksource;
255 * select_clocksource - Selects the best registered clocksource.
257 * Private function. Must hold clocksource_lock when called.
259 * Select the clocksource with the best rating, or the clocksource,
260 * which is selected by userspace override.
262 static struct clocksource *select_clocksource(void)
264 struct clocksource *next;
266 if (list_empty(&clocksource_list))
269 if (clocksource_override)
270 next = clocksource_override;
272 next = list_entry(clocksource_list.next, struct clocksource,
275 if (next == curr_clocksource)
282 * Enqueue the clocksource sorted by rating
284 static int clocksource_enqueue(struct clocksource *c)
286 struct list_head *tmp, *entry = &clocksource_list;
288 list_for_each(tmp, &clocksource_list) {
289 struct clocksource *cs;
291 cs = list_entry(tmp, struct clocksource, list);
294 /* Keep track of the place, where to insert */
295 if (cs->rating >= c->rating)
298 list_add(&c->list, entry);
300 if (strlen(c->name) == strlen(override_name) &&
301 !strcmp(c->name, override_name))
302 clocksource_override = c;
308 * clocksource_register - Used to install new clocksources
309 * @t: clocksource to be registered
311 * Returns -EBUSY if registration fails, zero otherwise.
313 int clocksource_register(struct clocksource *c)
318 spin_lock_irqsave(&clocksource_lock, flags);
319 ret = clocksource_enqueue(c);
321 next_clocksource = select_clocksource();
322 spin_unlock_irqrestore(&clocksource_lock, flags);
324 clocksource_check_watchdog(c);
327 EXPORT_SYMBOL(clocksource_register);
330 * clocksource_change_rating - Change the rating of a registered clocksource
333 void clocksource_change_rating(struct clocksource *cs, int rating)
337 spin_lock_irqsave(&clocksource_lock, flags);
340 clocksource_enqueue(cs);
341 next_clocksource = select_clocksource();
342 spin_unlock_irqrestore(&clocksource_lock, flags);
346 * clocksource_unregister - remove a registered clocksource
348 void clocksource_unregister(struct clocksource *cs)
352 spin_lock_irqsave(&clocksource_lock, flags);
354 if (clocksource_override == cs)
355 clocksource_override = NULL;
356 next_clocksource = select_clocksource();
357 spin_unlock_irqrestore(&clocksource_lock, flags);
362 * sysfs_show_current_clocksources - sysfs interface for current clocksource
364 * @buf: char buffer to be filled with clocksource list
366 * Provides sysfs interface for listing current clocksource.
369 sysfs_show_current_clocksources(struct sys_device *dev, char *buf)
373 spin_lock_irq(&clocksource_lock);
374 count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
375 spin_unlock_irq(&clocksource_lock);
381 * sysfs_override_clocksource - interface for manually overriding clocksource
383 * @buf: name of override clocksource
384 * @count: length of buffer
386 * Takes input from sysfs interface for manually overriding the default
387 * clocksource selction.
389 static ssize_t sysfs_override_clocksource(struct sys_device *dev,
390 const char *buf, size_t count)
392 struct clocksource *ovr = NULL;
396 /* strings from sysfs write are not 0 terminated! */
397 if (count >= sizeof(override_name))
401 if (buf[count-1] == '\n')
404 spin_lock_irq(&clocksource_lock);
407 memcpy(override_name, buf, count);
408 override_name[count] = 0;
410 len = strlen(override_name);
412 struct clocksource *cs;
414 ovr = clocksource_override;
415 /* try to select it: */
416 list_for_each_entry(cs, &clocksource_list, list) {
417 if (strlen(cs->name) == len &&
418 !strcmp(cs->name, override_name))
423 /* Reselect, when the override name has changed */
424 if (ovr != clocksource_override) {
425 clocksource_override = ovr;
426 next_clocksource = select_clocksource();
429 spin_unlock_irq(&clocksource_lock);
435 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
437 * @buf: char buffer to be filled with clocksource list
439 * Provides sysfs interface for listing registered clocksources
442 sysfs_show_available_clocksources(struct sys_device *dev, char *buf)
444 struct clocksource *src;
447 spin_lock_irq(&clocksource_lock);
448 list_for_each_entry(src, &clocksource_list, list) {
449 count += snprintf(buf + count,
450 max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
453 spin_unlock_irq(&clocksource_lock);
455 count += snprintf(buf + count,
456 max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
464 static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources,
465 sysfs_override_clocksource);
467 static SYSDEV_ATTR(available_clocksource, 0600,
468 sysfs_show_available_clocksources, NULL);
470 static struct sysdev_class clocksource_sysclass = {
471 .name = "clocksource",
474 static struct sys_device device_clocksource = {
476 .cls = &clocksource_sysclass,
479 static int __init init_clocksource_sysfs(void)
481 int error = sysdev_class_register(&clocksource_sysclass);
484 error = sysdev_register(&device_clocksource);
486 error = sysdev_create_file(
488 &attr_current_clocksource);
490 error = sysdev_create_file(
492 &attr_available_clocksource);
496 device_initcall(init_clocksource_sysfs);
497 #endif /* CONFIG_SYSFS */
500 * boot_override_clocksource - boot clock override
501 * @str: override name
503 * Takes a clocksource= boot argument and uses it
504 * as the clocksource override name.
506 static int __init boot_override_clocksource(char* str)
509 spin_lock_irqsave(&clocksource_lock, flags);
511 strlcpy(override_name, str, sizeof(override_name));
512 spin_unlock_irqrestore(&clocksource_lock, flags);
516 __setup("clocksource=", boot_override_clocksource);
519 * boot_override_clock - Compatibility layer for deprecated boot option
520 * @str: override name
522 * DEPRECATED! Takes a clock= boot argument and uses it
523 * as the clocksource override name
525 static int __init boot_override_clock(char* str)
527 if (!strcmp(str, "pmtmr")) {
528 printk("Warning: clock=pmtmr is deprecated. "
529 "Use clocksource=acpi_pm.\n");
530 return boot_override_clocksource("acpi_pm");
532 printk("Warning! clock= boot option is deprecated. "
533 "Use clocksource=xyz\n");
534 return boot_override_clocksource(str);
537 __setup("clock=", boot_override_clock);