projects/linux·blob v2.6.21 · refs

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1/*
2 * linux/kernel/time/clocksource.c
3 *
4 * This file contains the functions which manage clocksource drivers.
5 *
6 * Copyright (C) 2004, 2005 IBM, John Stultz ([email protected])
7 *
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.
12 *
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.
17 *
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.
21 *
22 * TODO WishList:
23 * o Allow clocksource drivers to be unregistered
24 * o get rid of clocksource_jiffies extern
25 */
26
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>
33
34/* XXX - Would like a better way for initializing curr_clocksource */
35extern struct clocksource clocksource_jiffies;
36
37/*[Clocksource internal variables]---------
38 * curr_clocksource:
39 * currently selected clocksource. Initialized to clocksource_jiffies.
40 * next_clocksource:
41 * pending next selected clocksource.
42 * clocksource_list:
43 * linked list with the registered clocksources
44 * clocksource_lock:
45 * protects manipulations to curr_clocksource and next_clocksource
46 * and the clocksource_list
47 * override_name:
48 * Name of the user-specified clocksource.
49 */
50static struct clocksource *curr_clocksource = &clocksource_jiffies;
51static struct clocksource *next_clocksource;
52static struct clocksource *clocksource_override;
53static LIST_HEAD(clocksource_list);
54static DEFINE_SPINLOCK(clocksource_lock);
55static char override_name[32];
56static int finished_booting;
57
58/* clocksource_done_booting - Called near the end of core bootup
59 *
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.
63 */
64static int __init clocksource_done_booting(void)
65{
66 finished_booting = 1;
67 return 0;
68}
69fs_initcall(clocksource_done_booting);
70
71#ifdef CONFIG_CLOCKSOURCE_WATCHDOG
72static LIST_HEAD(watchdog_list);
73static struct clocksource *watchdog;
74static struct timer_list watchdog_timer;
75static DEFINE_SPINLOCK(watchdog_lock);
76static cycle_t watchdog_last;
77/*
78 * Interval: 0.5sec Treshold: 0.0625s
79 */
80#define WATCHDOG_INTERVAL (HZ >> 1)
81#define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4)
82
83static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
84{
85 if (delta > -WATCHDOG_TRESHOLD && delta < WATCHDOG_TRESHOLD)
86 return;
87
88 printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
89 cs->name, delta);
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);
94}
95
96static void clocksource_watchdog(unsigned long data)
97{
98 struct clocksource *cs, *tmp;
99 cycle_t csnow, wdnow;
100 int64_t wd_nsec, cs_nsec;
101
102 spin_lock(&watchdog_lock);
103
104 wdnow = watchdog->read();
105 wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
106 watchdog_last = wdnow;
107
108 list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
109 csnow = cs->read();
110 /* Initialized ? */
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;
115 /*
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:
120 */
121 tick_clock_notify();
122 }
123 cs->flags |= CLOCK_SOURCE_WATCHDOG;
124 cs->wd_last = csnow;
125 } else {
126 cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
127 cs->wd_last = csnow;
128 /* Check the delta. Might remove from the list ! */
129 clocksource_ratewd(cs, cs_nsec - wd_nsec);
130 }
131 }
132
133 if (!list_empty(&watchdog_list)) {
134 __mod_timer(&watchdog_timer,
135 watchdog_timer.expires + WATCHDOG_INTERVAL);
136 }
137 spin_unlock(&watchdog_lock);
138}
139static void clocksource_check_watchdog(struct clocksource *cs)
140{
141 struct clocksource *cse;
142 unsigned long flags;
143
144 spin_lock_irqsave(&watchdog_lock, flags);
145 if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
146 int started = !list_empty(&watchdog_list);
147
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);
153 }
154 } else {
155 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
156 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
157
158 if (!watchdog || cs->rating > watchdog->rating) {
159 if (watchdog)
160 del_timer(&watchdog_timer);
161 watchdog = cs;
162 init_timer(&watchdog_timer);
163 watchdog_timer.function = clocksource_watchdog;
164
165 /* Reset watchdog cycles */
166 list_for_each_entry(cse, &watchdog_list, wd_list)
167 cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
168 /* Start if list is not empty */
169 if (!list_empty(&watchdog_list)) {
170 watchdog_last = watchdog->read();
171 watchdog_timer.expires =
172 jiffies + WATCHDOG_INTERVAL;
173 add_timer(&watchdog_timer);
174 }
175 }
176 }
177 spin_unlock_irqrestore(&watchdog_lock, flags);
178}
179#else
180static void clocksource_check_watchdog(struct clocksource *cs)
181{
182 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
183 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
184}
185#endif
186
187/**
188 * clocksource_get_next - Returns the selected clocksource
189 *
190 */
191struct clocksource *clocksource_get_next(void)
192{
193 unsigned long flags;
194
195 spin_lock_irqsave(&clocksource_lock, flags);
196 if (next_clocksource && finished_booting) {
197 curr_clocksource = next_clocksource;
198 next_clocksource = NULL;
199 }
200 spin_unlock_irqrestore(&clocksource_lock, flags);
201
202 return curr_clocksource;
203}
204
205/**
206 * select_clocksource - Selects the best registered clocksource.
207 *
208 * Private function. Must hold clocksource_lock when called.
209 *
210 * Select the clocksource with the best rating, or the clocksource,
211 * which is selected by userspace override.
212 */
213static struct clocksource *select_clocksource(void)
214{
215 struct clocksource *next;
216
217 if (list_empty(&clocksource_list))
218 return NULL;
219
220 if (clocksource_override)
221 next = clocksource_override;
222 else
223 next = list_entry(clocksource_list.next, struct clocksource,
224 list);
225
226 if (next == curr_clocksource)
227 return NULL;
228
229 return next;
230}
231
232/*
233 * Enqueue the clocksource sorted by rating
234 */
235static int clocksource_enqueue(struct clocksource *c)
236{
237 struct list_head *tmp, *entry = &clocksource_list;
238
239 list_for_each(tmp, &clocksource_list) {
240 struct clocksource *cs;
241
242 cs = list_entry(tmp, struct clocksource, list);
243 if (cs == c)
244 return -EBUSY;
245 /* Keep track of the place, where to insert */
246 if (cs->rating >= c->rating)
247 entry = tmp;
248 }
249 list_add(&c->list, entry);
250
251 if (strlen(c->name) == strlen(override_name) &&
252 !strcmp(c->name, override_name))
253 clocksource_override = c;
254
255 return 0;
256}
257
258/**
259 * clocksource_register - Used to install new clocksources
260 * @t: clocksource to be registered
261 *
262 * Returns -EBUSY if registration fails, zero otherwise.
263 */
264int clocksource_register(struct clocksource *c)
265{
266 unsigned long flags;
267 int ret;
268
269 spin_lock_irqsave(&clocksource_lock, flags);
270 ret = clocksource_enqueue(c);
271 if (!ret)
272 next_clocksource = select_clocksource();
273 spin_unlock_irqrestore(&clocksource_lock, flags);
274 if (!ret)
275 clocksource_check_watchdog(c);
276 return ret;
277}
278EXPORT_SYMBOL(clocksource_register);
279
280/**
281 * clocksource_change_rating - Change the rating of a registered clocksource
282 *
283 */
284void clocksource_change_rating(struct clocksource *cs, int rating)
285{
286 unsigned long flags;
287
288 spin_lock_irqsave(&clocksource_lock, flags);
289 list_del(&cs->list);
290 cs->rating = rating;
291 clocksource_enqueue(cs);
292 next_clocksource = select_clocksource();
293 spin_unlock_irqrestore(&clocksource_lock, flags);
294}
295
296#ifdef CONFIG_SYSFS
297/**
298 * sysfs_show_current_clocksources - sysfs interface for current clocksource
299 * @dev: unused
300 * @buf: char buffer to be filled with clocksource list
301 *
302 * Provides sysfs interface for listing current clocksource.
303 */
304static ssize_t
305sysfs_show_current_clocksources(struct sys_device *dev, char *buf)
306{
307 char *curr = buf;
308
309 spin_lock_irq(&clocksource_lock);
310 curr += sprintf(curr, "%s ", curr_clocksource->name);
311 spin_unlock_irq(&clocksource_lock);
312
313 curr += sprintf(curr, "\n");
314
315 return curr - buf;
316}
317
318/**
319 * sysfs_override_clocksource - interface for manually overriding clocksource
320 * @dev: unused
321 * @buf: name of override clocksource
322 * @count: length of buffer
323 *
324 * Takes input from sysfs interface for manually overriding the default
325 * clocksource selction.
326 */
327static ssize_t sysfs_override_clocksource(struct sys_device *dev,
328 const char *buf, size_t count)
329{
330 struct clocksource *ovr = NULL;
331 struct list_head *tmp;
332 size_t ret = count;
333 int len;
334
335 /* strings from sysfs write are not 0 terminated! */
336 if (count >= sizeof(override_name))
337 return -EINVAL;
338
339 /* strip of \n: */
340 if (buf[count-1] == '\n')
341 count--;
342
343 spin_lock_irq(&clocksource_lock);
344
345 if (count > 0)
346 memcpy(override_name, buf, count);
347 override_name[count] = 0;
348
349 len = strlen(override_name);
350 if (len) {
351 ovr = clocksource_override;
352 /* try to select it: */
353 list_for_each(tmp, &clocksource_list) {
354 struct clocksource *cs;
355
356 cs = list_entry(tmp, struct clocksource, list);
357 if (strlen(cs->name) == len &&
358 !strcmp(cs->name, override_name))
359 ovr = cs;
360 }
361 }
362
363 /* Reselect, when the override name has changed */
364 if (ovr != clocksource_override) {
365 clocksource_override = ovr;
366 next_clocksource = select_clocksource();
367 }
368
369 spin_unlock_irq(&clocksource_lock);
370
371 return ret;
372}
373
374/**
375 * sysfs_show_available_clocksources - sysfs interface for listing clocksource
376 * @dev: unused
377 * @buf: char buffer to be filled with clocksource list
378 *
379 * Provides sysfs interface for listing registered clocksources
380 */
381static ssize_t
382sysfs_show_available_clocksources(struct sys_device *dev, char *buf)
383{
384 struct list_head *tmp;
385 char *curr = buf;
386
387 spin_lock_irq(&clocksource_lock);
388 list_for_each(tmp, &clocksource_list) {
389 struct clocksource *src;
390
391 src = list_entry(tmp, struct clocksource, list);
392 curr += sprintf(curr, "%s ", src->name);
393 }
394 spin_unlock_irq(&clocksource_lock);
395
396 curr += sprintf(curr, "\n");
397
398 return curr - buf;
399}
400
401/*
402 * Sysfs setup bits:
403 */
404static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources,
405 sysfs_override_clocksource);
406
407static SYSDEV_ATTR(available_clocksource, 0600,
408 sysfs_show_available_clocksources, NULL);
409
410static struct sysdev_class clocksource_sysclass = {
411 set_kset_name("clocksource"),
412};
413
414static struct sys_device device_clocksource = {
415 .id = 0,
416 .cls = &clocksource_sysclass,
417};
418
419static int __init init_clocksource_sysfs(void)
420{
421 int error = sysdev_class_register(&clocksource_sysclass);
422
423 if (!error)
424 error = sysdev_register(&device_clocksource);
425 if (!error)
426 error = sysdev_create_file(
427 &device_clocksource,
428 &attr_current_clocksource);
429 if (!error)
430 error = sysdev_create_file(
431 &device_clocksource,
432 &attr_available_clocksource);
433 return error;
434}
435
436device_initcall(init_clocksource_sysfs);
437#endif /* CONFIG_SYSFS */
438
439/**
440 * boot_override_clocksource - boot clock override
441 * @str: override name
442 *
443 * Takes a clocksource= boot argument and uses it
444 * as the clocksource override name.
445 */
446static int __init boot_override_clocksource(char* str)
447{
448 unsigned long flags;
449 spin_lock_irqsave(&clocksource_lock, flags);
450 if (str)
451 strlcpy(override_name, str, sizeof(override_name));
452 spin_unlock_irqrestore(&clocksource_lock, flags);
453 return 1;
454}
455
456__setup("clocksource=", boot_override_clocksource);
457
458/**
459 * boot_override_clock - Compatibility layer for deprecated boot option
460 * @str: override name
461 *
462 * DEPRECATED! Takes a clock= boot argument and uses it
463 * as the clocksource override name
464 */
465static int __init boot_override_clock(char* str)
466{
467 if (!strcmp(str, "pmtmr")) {
468 printk("Warning: clock=pmtmr is deprecated. "
469 "Use clocksource=acpi_pm.\n");
470 return boot_override_clocksource("acpi_pm");
471 }
472 printk("Warning! clock= boot option is deprecated. "
473 "Use clocksource=xyz\n");
474 return boot_override_clocksource(str);
475}
476
477__setup("clock=", boot_override_clock);