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734efb46 JS |
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 (johnstul@us.ibm.com) | |
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> | |
dc29a365 | 31 | #include <linux/sched.h> /* for spin_unlock_irq() using preempt_count() m68k */ |
79bf2bb3 | 32 | #include <linux/tick.h> |
734efb46 JS |
33 | |
34 | /* XXX - Would like a better way for initializing curr_clocksource */ | |
35 | extern 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 | */ | |
50 | static struct clocksource *curr_clocksource = &clocksource_jiffies; | |
51 | static struct clocksource *next_clocksource; | |
92c7e002 | 52 | static struct clocksource *clocksource_override; |
734efb46 JS |
53 | static LIST_HEAD(clocksource_list); |
54 | static DEFINE_SPINLOCK(clocksource_lock); | |
55 | static char override_name[32]; | |
56 | static int finished_booting; | |
57 | ||
6bb74df4 | 58 | /* clocksource_done_booting - Called near the end of core bootup |
734efb46 | 59 | * |
6bb74df4 JS |
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. | |
734efb46 | 63 | */ |
ad596171 | 64 | static int __init clocksource_done_booting(void) |
734efb46 JS |
65 | { |
66 | finished_booting = 1; | |
67 | return 0; | |
68 | } | |
6bb74df4 | 69 | fs_initcall(clocksource_done_booting); |
734efb46 | 70 | |
5d8b34fd TG |
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 | /* | |
78 | * Interval: 0.5sec Treshold: 0.0625s | |
79 | */ | |
80 | #define WATCHDOG_INTERVAL (HZ >> 1) | |
81 | #define WATCHDOG_TRESHOLD (NSEC_PER_SEC >> 4) | |
82 | ||
83 | static 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 | ||
96 | static 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; | |
79bf2bb3 TG |
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(); | |
5d8b34fd TG |
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 | } | |
139 | static 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 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) { | |
155 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; | |
156 | ||
157 | if (!watchdog || cs->rating > watchdog->rating) { | |
158 | if (watchdog) | |
159 | del_timer(&watchdog_timer); | |
160 | watchdog = cs; | |
161 | init_timer(&watchdog_timer); | |
162 | watchdog_timer.function = clocksource_watchdog; | |
163 | ||
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); | |
173 | } | |
174 | } | |
175 | } | |
176 | spin_unlock_irqrestore(&watchdog_lock, flags); | |
177 | } | |
178 | #else | |
179 | static void clocksource_check_watchdog(struct clocksource *cs) | |
180 | { | |
181 | if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS) | |
182 | cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES; | |
183 | } | |
184 | #endif | |
185 | ||
734efb46 | 186 | /** |
a2752549 | 187 | * clocksource_get_next - Returns the selected clocksource |
734efb46 JS |
188 | * |
189 | */ | |
a2752549 | 190 | struct clocksource *clocksource_get_next(void) |
734efb46 JS |
191 | { |
192 | unsigned long flags; | |
193 | ||
194 | spin_lock_irqsave(&clocksource_lock, flags); | |
195 | if (next_clocksource && finished_booting) { | |
196 | curr_clocksource = next_clocksource; | |
197 | next_clocksource = NULL; | |
198 | } | |
199 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
200 | ||
201 | return curr_clocksource; | |
202 | } | |
203 | ||
204 | /** | |
92c7e002 | 205 | * select_clocksource - Selects the best registered clocksource. |
734efb46 JS |
206 | * |
207 | * Private function. Must hold clocksource_lock when called. | |
208 | * | |
92c7e002 TG |
209 | * Select the clocksource with the best rating, or the clocksource, |
210 | * which is selected by userspace override. | |
734efb46 JS |
211 | */ |
212 | static struct clocksource *select_clocksource(void) | |
213 | { | |
5d8b34fd TG |
214 | struct clocksource *next; |
215 | ||
92c7e002 TG |
216 | if (list_empty(&clocksource_list)) |
217 | return NULL; | |
734efb46 | 218 | |
92c7e002 | 219 | if (clocksource_override) |
5d8b34fd TG |
220 | next = clocksource_override; |
221 | else | |
222 | next = list_entry(clocksource_list.next, struct clocksource, | |
223 | list); | |
734efb46 | 224 | |
5d8b34fd TG |
225 | if (next == curr_clocksource) |
226 | return NULL; | |
227 | ||
228 | return next; | |
734efb46 JS |
229 | } |
230 | ||
92c7e002 TG |
231 | /* |
232 | * Enqueue the clocksource sorted by rating | |
734efb46 | 233 | */ |
92c7e002 | 234 | static int clocksource_enqueue(struct clocksource *c) |
734efb46 | 235 | { |
92c7e002 | 236 | struct list_head *tmp, *entry = &clocksource_list; |
734efb46 JS |
237 | |
238 | list_for_each(tmp, &clocksource_list) { | |
92c7e002 TG |
239 | struct clocksource *cs; |
240 | ||
241 | cs = list_entry(tmp, struct clocksource, list); | |
242 | if (cs == c) | |
243 | return -EBUSY; | |
244 | /* Keep track of the place, where to insert */ | |
245 | if (cs->rating >= c->rating) | |
246 | entry = tmp; | |
734efb46 | 247 | } |
92c7e002 TG |
248 | list_add(&c->list, entry); |
249 | ||
250 | if (strlen(c->name) == strlen(override_name) && | |
251 | !strcmp(c->name, override_name)) | |
252 | clocksource_override = c; | |
734efb46 JS |
253 | |
254 | return 0; | |
255 | } | |
256 | ||
257 | /** | |
a2752549 | 258 | * clocksource_register - Used to install new clocksources |
734efb46 JS |
259 | * @t: clocksource to be registered |
260 | * | |
261 | * Returns -EBUSY if registration fails, zero otherwise. | |
262 | */ | |
a2752549 | 263 | int clocksource_register(struct clocksource *c) |
734efb46 | 264 | { |
734efb46 | 265 | unsigned long flags; |
5d8b34fd | 266 | int ret; |
734efb46 JS |
267 | |
268 | spin_lock_irqsave(&clocksource_lock, flags); | |
92c7e002 TG |
269 | ret = clocksource_enqueue(c); |
270 | if (!ret) | |
734efb46 | 271 | next_clocksource = select_clocksource(); |
734efb46 | 272 | spin_unlock_irqrestore(&clocksource_lock, flags); |
5d8b34fd TG |
273 | if (!ret) |
274 | clocksource_check_watchdog(c); | |
734efb46 JS |
275 | return ret; |
276 | } | |
a2752549 | 277 | EXPORT_SYMBOL(clocksource_register); |
734efb46 JS |
278 | |
279 | /** | |
92c7e002 | 280 | * clocksource_change_rating - Change the rating of a registered clocksource |
734efb46 | 281 | * |
734efb46 | 282 | */ |
92c7e002 | 283 | void clocksource_change_rating(struct clocksource *cs, int rating) |
734efb46 JS |
284 | { |
285 | unsigned long flags; | |
286 | ||
287 | spin_lock_irqsave(&clocksource_lock, flags); | |
92c7e002 | 288 | list_del(&cs->list); |
5d8b34fd | 289 | cs->rating = rating; |
92c7e002 | 290 | clocksource_enqueue(cs); |
734efb46 JS |
291 | next_clocksource = select_clocksource(); |
292 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
293 | } | |
294 | ||
2b013700 | 295 | #ifdef CONFIG_SYSFS |
734efb46 JS |
296 | /** |
297 | * sysfs_show_current_clocksources - sysfs interface for current clocksource | |
298 | * @dev: unused | |
299 | * @buf: char buffer to be filled with clocksource list | |
300 | * | |
301 | * Provides sysfs interface for listing current clocksource. | |
302 | */ | |
303 | static ssize_t | |
304 | sysfs_show_current_clocksources(struct sys_device *dev, char *buf) | |
305 | { | |
306 | char *curr = buf; | |
307 | ||
308 | spin_lock_irq(&clocksource_lock); | |
309 | curr += sprintf(curr, "%s ", curr_clocksource->name); | |
310 | spin_unlock_irq(&clocksource_lock); | |
311 | ||
312 | curr += sprintf(curr, "\n"); | |
313 | ||
314 | return curr - buf; | |
315 | } | |
316 | ||
317 | /** | |
318 | * sysfs_override_clocksource - interface for manually overriding clocksource | |
319 | * @dev: unused | |
320 | * @buf: name of override clocksource | |
321 | * @count: length of buffer | |
322 | * | |
323 | * Takes input from sysfs interface for manually overriding the default | |
324 | * clocksource selction. | |
325 | */ | |
326 | static ssize_t sysfs_override_clocksource(struct sys_device *dev, | |
327 | const char *buf, size_t count) | |
328 | { | |
92c7e002 TG |
329 | struct clocksource *ovr = NULL; |
330 | struct list_head *tmp; | |
734efb46 | 331 | size_t ret = count; |
92c7e002 TG |
332 | int len; |
333 | ||
734efb46 JS |
334 | /* strings from sysfs write are not 0 terminated! */ |
335 | if (count >= sizeof(override_name)) | |
336 | return -EINVAL; | |
337 | ||
338 | /* strip of \n: */ | |
339 | if (buf[count-1] == '\n') | |
340 | count--; | |
734efb46 JS |
341 | |
342 | spin_lock_irq(&clocksource_lock); | |
343 | ||
92c7e002 TG |
344 | if (count > 0) |
345 | memcpy(override_name, buf, count); | |
734efb46 JS |
346 | override_name[count] = 0; |
347 | ||
92c7e002 TG |
348 | len = strlen(override_name); |
349 | if (len) { | |
350 | ovr = clocksource_override; | |
351 | /* try to select it: */ | |
352 | list_for_each(tmp, &clocksource_list) { | |
353 | struct clocksource *cs; | |
354 | ||
355 | cs = list_entry(tmp, struct clocksource, list); | |
356 | if (strlen(cs->name) == len && | |
357 | !strcmp(cs->name, override_name)) | |
358 | ovr = cs; | |
359 | } | |
360 | } | |
361 | ||
362 | /* Reselect, when the override name has changed */ | |
363 | if (ovr != clocksource_override) { | |
364 | clocksource_override = ovr; | |
365 | next_clocksource = select_clocksource(); | |
366 | } | |
734efb46 JS |
367 | |
368 | spin_unlock_irq(&clocksource_lock); | |
369 | ||
370 | return ret; | |
371 | } | |
372 | ||
373 | /** | |
374 | * sysfs_show_available_clocksources - sysfs interface for listing clocksource | |
375 | * @dev: unused | |
376 | * @buf: char buffer to be filled with clocksource list | |
377 | * | |
378 | * Provides sysfs interface for listing registered clocksources | |
379 | */ | |
380 | static ssize_t | |
381 | sysfs_show_available_clocksources(struct sys_device *dev, char *buf) | |
382 | { | |
383 | struct list_head *tmp; | |
384 | char *curr = buf; | |
385 | ||
386 | spin_lock_irq(&clocksource_lock); | |
387 | list_for_each(tmp, &clocksource_list) { | |
388 | struct clocksource *src; | |
389 | ||
390 | src = list_entry(tmp, struct clocksource, list); | |
391 | curr += sprintf(curr, "%s ", src->name); | |
392 | } | |
393 | spin_unlock_irq(&clocksource_lock); | |
394 | ||
395 | curr += sprintf(curr, "\n"); | |
396 | ||
397 | return curr - buf; | |
398 | } | |
399 | ||
400 | /* | |
401 | * Sysfs setup bits: | |
402 | */ | |
403 | static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources, | |
f5f1a24a | 404 | sysfs_override_clocksource); |
734efb46 JS |
405 | |
406 | static SYSDEV_ATTR(available_clocksource, 0600, | |
f5f1a24a | 407 | sysfs_show_available_clocksources, NULL); |
734efb46 JS |
408 | |
409 | static struct sysdev_class clocksource_sysclass = { | |
410 | set_kset_name("clocksource"), | |
411 | }; | |
412 | ||
413 | static struct sys_device device_clocksource = { | |
414 | .id = 0, | |
415 | .cls = &clocksource_sysclass, | |
416 | }; | |
417 | ||
ad596171 | 418 | static int __init init_clocksource_sysfs(void) |
734efb46 JS |
419 | { |
420 | int error = sysdev_class_register(&clocksource_sysclass); | |
421 | ||
422 | if (!error) | |
423 | error = sysdev_register(&device_clocksource); | |
424 | if (!error) | |
425 | error = sysdev_create_file( | |
426 | &device_clocksource, | |
427 | &attr_current_clocksource); | |
428 | if (!error) | |
429 | error = sysdev_create_file( | |
430 | &device_clocksource, | |
431 | &attr_available_clocksource); | |
432 | return error; | |
433 | } | |
434 | ||
435 | device_initcall(init_clocksource_sysfs); | |
2b013700 | 436 | #endif /* CONFIG_SYSFS */ |
734efb46 JS |
437 | |
438 | /** | |
439 | * boot_override_clocksource - boot clock override | |
440 | * @str: override name | |
441 | * | |
442 | * Takes a clocksource= boot argument and uses it | |
443 | * as the clocksource override name. | |
444 | */ | |
445 | static int __init boot_override_clocksource(char* str) | |
446 | { | |
447 | unsigned long flags; | |
448 | spin_lock_irqsave(&clocksource_lock, flags); | |
449 | if (str) | |
450 | strlcpy(override_name, str, sizeof(override_name)); | |
451 | spin_unlock_irqrestore(&clocksource_lock, flags); | |
452 | return 1; | |
453 | } | |
454 | ||
455 | __setup("clocksource=", boot_override_clocksource); | |
456 | ||
457 | /** | |
458 | * boot_override_clock - Compatibility layer for deprecated boot option | |
459 | * @str: override name | |
460 | * | |
461 | * DEPRECATED! Takes a clock= boot argument and uses it | |
462 | * as the clocksource override name | |
463 | */ | |
464 | static int __init boot_override_clock(char* str) | |
465 | { | |
5d0cf410 JS |
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"); | |
470 | } | |
471 | printk("Warning! clock= boot option is deprecated. " | |
472 | "Use clocksource=xyz\n"); | |
734efb46 JS |
473 | return boot_override_clocksource(str); |
474 | } | |
475 | ||
476 | __setup("clock=", boot_override_clock); |