clocksource: remove redundant code
[sfrench/cifs-2.6.git] / kernel / time / clocksource.c
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>
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 */
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;
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;
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  */
64 static int __init clocksource_done_booting(void)
65 {
66         finished_booting = 1;
67         return 0;
68 }
69 fs_initcall(clocksource_done_booting);
70
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;
78
79 /*
80  * Interval: 0.5sec Threshold: 0.0625s
81  */
82 #define WATCHDOG_INTERVAL (HZ >> 1)
83 #define WATCHDOG_THRESHOLD (NSEC_PER_SEC >> 4)
84
85 static void clocksource_ratewd(struct clocksource *cs, int64_t delta)
86 {
87         if (delta > -WATCHDOG_THRESHOLD && delta < WATCHDOG_THRESHOLD)
88                 return;
89
90         printk(KERN_WARNING "Clocksource %s unstable (delta = %Ld ns)\n",
91                cs->name, delta);
92         cs->flags &= ~(CLOCK_SOURCE_VALID_FOR_HRES | CLOCK_SOURCE_WATCHDOG);
93         clocksource_change_rating(cs, 0);
94         list_del(&cs->wd_list);
95 }
96
97 static void clocksource_watchdog(unsigned long data)
98 {
99         struct clocksource *cs, *tmp;
100         cycle_t csnow, wdnow;
101         int64_t wd_nsec, cs_nsec;
102         int resumed;
103
104         spin_lock(&watchdog_lock);
105
106         resumed = test_and_clear_bit(0, &watchdog_resumed);
107
108         wdnow = watchdog->read();
109         wd_nsec = cyc2ns(watchdog, (wdnow - watchdog_last) & watchdog->mask);
110         watchdog_last = wdnow;
111
112         list_for_each_entry_safe(cs, tmp, &watchdog_list, wd_list) {
113                 csnow = cs->read();
114
115                 if (unlikely(resumed)) {
116                         cs->wd_last = csnow;
117                         continue;
118                 }
119
120                 /* Initialized ? */
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;
125                                 /*
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:
130                                  */
131                                 tick_clock_notify();
132                         }
133                         cs->flags |= CLOCK_SOURCE_WATCHDOG;
134                         cs->wd_last = csnow;
135                 } else {
136                         cs_nsec = cyc2ns(cs, (csnow - cs->wd_last) & cs->mask);
137                         cs->wd_last = csnow;
138                         /* Check the delta. Might remove from the list ! */
139                         clocksource_ratewd(cs, cs_nsec - wd_nsec);
140                 }
141         }
142
143         if (!list_empty(&watchdog_list)) {
144                 /* Cycle through CPUs to check if the CPUs stay synchronized to
145                  * each other. */
146                 int next_cpu = next_cpu(raw_smp_processor_id(), cpu_online_map);
147                 if (next_cpu >= NR_CPUS)
148                         next_cpu = first_cpu(cpu_online_map);
149                 watchdog_timer.expires += WATCHDOG_INTERVAL;
150                 add_timer_on(&watchdog_timer, next_cpu);
151         }
152         spin_unlock(&watchdog_lock);
153 }
154 static void clocksource_resume_watchdog(void)
155 {
156         set_bit(0, &watchdog_resumed);
157 }
158
159 static void clocksource_check_watchdog(struct clocksource *cs)
160 {
161         struct clocksource *cse;
162         unsigned long flags;
163
164         spin_lock_irqsave(&watchdog_lock, flags);
165         if (cs->flags & CLOCK_SOURCE_MUST_VERIFY) {
166                 int started = !list_empty(&watchdog_list);
167
168                 list_add(&cs->wd_list, &watchdog_list);
169                 if (!started && watchdog) {
170                         watchdog_last = watchdog->read();
171                         watchdog_timer.expires = jiffies + WATCHDOG_INTERVAL;
172                         add_timer_on(&watchdog_timer, first_cpu(cpu_online_map));
173                 }
174         } else {
175                 if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
176                         cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
177
178                 if (!watchdog || cs->rating > watchdog->rating) {
179                         if (watchdog)
180                                 del_timer(&watchdog_timer);
181                         watchdog = cs;
182                         init_timer_deferrable(&watchdog_timer);
183                         watchdog_timer.function = clocksource_watchdog;
184
185                         /* Reset watchdog cycles */
186                         list_for_each_entry(cse, &watchdog_list, wd_list)
187                                 cse->flags &= ~CLOCK_SOURCE_WATCHDOG;
188                         /* Start if list is not empty */
189                         if (!list_empty(&watchdog_list)) {
190                                 watchdog_last = watchdog->read();
191                                 watchdog_timer.expires =
192                                         jiffies + WATCHDOG_INTERVAL;
193                                 add_timer_on(&watchdog_timer,
194                                                 first_cpu(cpu_online_map));
195                         }
196                 }
197         }
198         spin_unlock_irqrestore(&watchdog_lock, flags);
199 }
200 #else
201 static void clocksource_check_watchdog(struct clocksource *cs)
202 {
203         if (cs->flags & CLOCK_SOURCE_IS_CONTINUOUS)
204                 cs->flags |= CLOCK_SOURCE_VALID_FOR_HRES;
205 }
206
207 static inline void clocksource_resume_watchdog(void) { }
208 #endif
209
210 /**
211  * clocksource_resume - resume the clocksource(s)
212  */
213 void clocksource_resume(void)
214 {
215         struct clocksource *cs;
216         unsigned long flags;
217
218         spin_lock_irqsave(&clocksource_lock, flags);
219
220         list_for_each_entry(cs, &clocksource_list, list) {
221                 if (cs->resume)
222                         cs->resume();
223         }
224
225         clocksource_resume_watchdog();
226
227         spin_unlock_irqrestore(&clocksource_lock, flags);
228 }
229
230 /**
231  * clocksource_get_next - Returns the selected clocksource
232  *
233  */
234 struct clocksource *clocksource_get_next(void)
235 {
236         unsigned long flags;
237
238         spin_lock_irqsave(&clocksource_lock, flags);
239         if (next_clocksource && finished_booting) {
240                 curr_clocksource = next_clocksource;
241                 next_clocksource = NULL;
242         }
243         spin_unlock_irqrestore(&clocksource_lock, flags);
244
245         return curr_clocksource;
246 }
247
248 /**
249  * select_clocksource - Selects the best registered clocksource.
250  *
251  * Private function. Must hold clocksource_lock when called.
252  *
253  * Select the clocksource with the best rating, or the clocksource,
254  * which is selected by userspace override.
255  */
256 static struct clocksource *select_clocksource(void)
257 {
258         struct clocksource *next;
259
260         if (list_empty(&clocksource_list))
261                 return NULL;
262
263         if (clocksource_override)
264                 next = clocksource_override;
265         else
266                 next = list_entry(clocksource_list.next, struct clocksource,
267                                   list);
268
269         if (next == curr_clocksource)
270                 return NULL;
271
272         return next;
273 }
274
275 /*
276  * Enqueue the clocksource sorted by rating
277  */
278 static int clocksource_enqueue(struct clocksource *c)
279 {
280         struct list_head *tmp, *entry = &clocksource_list;
281
282         list_for_each(tmp, &clocksource_list) {
283                 struct clocksource *cs;
284
285                 cs = list_entry(tmp, struct clocksource, list);
286                 if (cs == c)
287                         return -EBUSY;
288                 /* Keep track of the place, where to insert */
289                 if (cs->rating >= c->rating)
290                         entry = tmp;
291         }
292         list_add(&c->list, entry);
293
294         if (strlen(c->name) == strlen(override_name) &&
295             !strcmp(c->name, override_name))
296                 clocksource_override = c;
297
298         return 0;
299 }
300
301 /**
302  * clocksource_register - Used to install new clocksources
303  * @t:          clocksource to be registered
304  *
305  * Returns -EBUSY if registration fails, zero otherwise.
306  */
307 int clocksource_register(struct clocksource *c)
308 {
309         unsigned long flags;
310         int ret;
311
312         spin_lock_irqsave(&clocksource_lock, flags);
313         ret = clocksource_enqueue(c);
314         if (!ret)
315                 next_clocksource = select_clocksource();
316         spin_unlock_irqrestore(&clocksource_lock, flags);
317         if (!ret)
318                 clocksource_check_watchdog(c);
319         return ret;
320 }
321 EXPORT_SYMBOL(clocksource_register);
322
323 /**
324  * clocksource_change_rating - Change the rating of a registered clocksource
325  *
326  */
327 void clocksource_change_rating(struct clocksource *cs, int rating)
328 {
329         unsigned long flags;
330
331         spin_lock_irqsave(&clocksource_lock, flags);
332         list_del(&cs->list);
333         cs->rating = rating;
334         clocksource_enqueue(cs);
335         next_clocksource = select_clocksource();
336         spin_unlock_irqrestore(&clocksource_lock, flags);
337 }
338
339 /**
340  * clocksource_unregister - remove a registered clocksource
341  */
342 void clocksource_unregister(struct clocksource *cs)
343 {
344         unsigned long flags;
345
346         spin_lock_irqsave(&clocksource_lock, flags);
347         list_del(&cs->list);
348         if (clocksource_override == cs)
349                 clocksource_override = NULL;
350         next_clocksource = select_clocksource();
351         spin_unlock_irqrestore(&clocksource_lock, flags);
352 }
353
354 #ifdef CONFIG_SYSFS
355 /**
356  * sysfs_show_current_clocksources - sysfs interface for current clocksource
357  * @dev:        unused
358  * @buf:        char buffer to be filled with clocksource list
359  *
360  * Provides sysfs interface for listing current clocksource.
361  */
362 static ssize_t
363 sysfs_show_current_clocksources(struct sys_device *dev, char *buf)
364 {
365         ssize_t count = 0;
366
367         spin_lock_irq(&clocksource_lock);
368         count = snprintf(buf, PAGE_SIZE, "%s\n", curr_clocksource->name);
369         spin_unlock_irq(&clocksource_lock);
370
371         return count;
372 }
373
374 /**
375  * sysfs_override_clocksource - interface for manually overriding clocksource
376  * @dev:        unused
377  * @buf:        name of override clocksource
378  * @count:      length of buffer
379  *
380  * Takes input from sysfs interface for manually overriding the default
381  * clocksource selction.
382  */
383 static ssize_t sysfs_override_clocksource(struct sys_device *dev,
384                                           const char *buf, size_t count)
385 {
386         struct clocksource *ovr = NULL;
387         size_t ret = count;
388         int len;
389
390         /* strings from sysfs write are not 0 terminated! */
391         if (count >= sizeof(override_name))
392                 return -EINVAL;
393
394         /* strip of \n: */
395         if (buf[count-1] == '\n')
396                 count--;
397
398         spin_lock_irq(&clocksource_lock);
399
400         if (count > 0)
401                 memcpy(override_name, buf, count);
402         override_name[count] = 0;
403
404         len = strlen(override_name);
405         if (len) {
406                 struct clocksource *cs;
407
408                 ovr = clocksource_override;
409                 /* try to select it: */
410                 list_for_each_entry(cs, &clocksource_list, list) {
411                         if (strlen(cs->name) == len &&
412                             !strcmp(cs->name, override_name))
413                                 ovr = cs;
414                 }
415         }
416
417         /* Reselect, when the override name has changed */
418         if (ovr != clocksource_override) {
419                 clocksource_override = ovr;
420                 next_clocksource = select_clocksource();
421         }
422
423         spin_unlock_irq(&clocksource_lock);
424
425         return ret;
426 }
427
428 /**
429  * sysfs_show_available_clocksources - sysfs interface for listing clocksource
430  * @dev:        unused
431  * @buf:        char buffer to be filled with clocksource list
432  *
433  * Provides sysfs interface for listing registered clocksources
434  */
435 static ssize_t
436 sysfs_show_available_clocksources(struct sys_device *dev, char *buf)
437 {
438         struct clocksource *src;
439         ssize_t count = 0;
440
441         spin_lock_irq(&clocksource_lock);
442         list_for_each_entry(src, &clocksource_list, list) {
443                 count += snprintf(buf + count,
444                                   max((ssize_t)PAGE_SIZE - count, (ssize_t)0),
445                                   "%s ", src->name);
446         }
447         spin_unlock_irq(&clocksource_lock);
448
449         count += snprintf(buf + count,
450                           max((ssize_t)PAGE_SIZE - count, (ssize_t)0), "\n");
451
452         return count;
453 }
454
455 /*
456  * Sysfs setup bits:
457  */
458 static SYSDEV_ATTR(current_clocksource, 0600, sysfs_show_current_clocksources,
459                    sysfs_override_clocksource);
460
461 static SYSDEV_ATTR(available_clocksource, 0600,
462                    sysfs_show_available_clocksources, NULL);
463
464 static struct sysdev_class clocksource_sysclass = {
465         .name = "clocksource",
466 };
467
468 static struct sys_device device_clocksource = {
469         .id     = 0,
470         .cls    = &clocksource_sysclass,
471 };
472
473 static int __init init_clocksource_sysfs(void)
474 {
475         int error = sysdev_class_register(&clocksource_sysclass);
476
477         if (!error)
478                 error = sysdev_register(&device_clocksource);
479         if (!error)
480                 error = sysdev_create_file(
481                                 &device_clocksource,
482                                 &attr_current_clocksource);
483         if (!error)
484                 error = sysdev_create_file(
485                                 &device_clocksource,
486                                 &attr_available_clocksource);
487         return error;
488 }
489
490 device_initcall(init_clocksource_sysfs);
491 #endif /* CONFIG_SYSFS */
492
493 /**
494  * boot_override_clocksource - boot clock override
495  * @str:        override name
496  *
497  * Takes a clocksource= boot argument and uses it
498  * as the clocksource override name.
499  */
500 static int __init boot_override_clocksource(char* str)
501 {
502         unsigned long flags;
503         spin_lock_irqsave(&clocksource_lock, flags);
504         if (str)
505                 strlcpy(override_name, str, sizeof(override_name));
506         spin_unlock_irqrestore(&clocksource_lock, flags);
507         return 1;
508 }
509
510 __setup("clocksource=", boot_override_clocksource);
511
512 /**
513  * boot_override_clock - Compatibility layer for deprecated boot option
514  * @str:        override name
515  *
516  * DEPRECATED! Takes a clock= boot argument and uses it
517  * as the clocksource override name
518  */
519 static int __init boot_override_clock(char* str)
520 {
521         if (!strcmp(str, "pmtmr")) {
522                 printk("Warning: clock=pmtmr is deprecated. "
523                         "Use clocksource=acpi_pm.\n");
524                 return boot_override_clocksource("acpi_pm");
525         }
526         printk("Warning! clock= boot option is deprecated. "
527                 "Use clocksource=xyz\n");
528         return boot_override_clocksource(str);
529 }
530
531 __setup("clock=", boot_override_clock);