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authorjohn stultz <johnstul@us.ibm.com>2007-05-08 03:27:59 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 14:15:06 -0400
commit8524070b7982d76258942275908b7434cfcab4b4 (patch)
tree6e63c45c3b9ff6a86ad32b1de7adf48889eb0bfc /kernel/time/timekeeping.c
parent329c8d84ca1946c037d9859dc251b56d8b1b4630 (diff)
Move timekeeping code to timekeeping.c
Move the timekeeping code out of kernel/timer.c and into kernel/time/timekeeping.c. I made no cleanups or other changes in transit. [akpm@linux-foundation.org: build fix] Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/time/timekeeping.c')
-rw-r--r--kernel/time/timekeeping.c476
1 files changed, 476 insertions, 0 deletions
diff --git a/kernel/time/timekeeping.c b/kernel/time/timekeeping.c
new file mode 100644
index 000000000000..f9217bf644f6
--- /dev/null
+++ b/kernel/time/timekeeping.c
@@ -0,0 +1,476 @@
1/*
2 * linux/kernel/time/timekeeping.c
3 *
4 * Kernel timekeeping code and accessor functions
5 *
6 * This code was moved from linux/kernel/timer.c.
7 * Please see that file for copyright and history logs.
8 *
9 */
10
11#include <linux/module.h>
12#include <linux/interrupt.h>
13#include <linux/percpu.h>
14#include <linux/init.h>
15#include <linux/mm.h>
16#include <linux/sysdev.h>
17#include <linux/clocksource.h>
18#include <linux/jiffies.h>
19#include <linux/time.h>
20#include <linux/tick.h>
21
22
23/*
24 * This read-write spinlock protects us from races in SMP while
25 * playing with xtime and avenrun.
26 */
27__attribute__((weak)) __cacheline_aligned_in_smp DEFINE_SEQLOCK(xtime_lock);
28
29EXPORT_SYMBOL(xtime_lock);
30
31
32/*
33 * The current time
34 * wall_to_monotonic is what we need to add to xtime (or xtime corrected
35 * for sub jiffie times) to get to monotonic time. Monotonic is pegged
36 * at zero at system boot time, so wall_to_monotonic will be negative,
37 * however, we will ALWAYS keep the tv_nsec part positive so we can use
38 * the usual normalization.
39 */
40struct timespec xtime __attribute__ ((aligned (16)));
41struct timespec wall_to_monotonic __attribute__ ((aligned (16)));
42
43EXPORT_SYMBOL(xtime);
44
45
46static struct clocksource *clock; /* pointer to current clocksource */
47
48
49#ifdef CONFIG_GENERIC_TIME
50/**
51 * __get_nsec_offset - Returns nanoseconds since last call to periodic_hook
52 *
53 * private function, must hold xtime_lock lock when being
54 * called. Returns the number of nanoseconds since the
55 * last call to update_wall_time() (adjusted by NTP scaling)
56 */
57static inline s64 __get_nsec_offset(void)
58{
59 cycle_t cycle_now, cycle_delta;
60 s64 ns_offset;
61
62 /* read clocksource: */
63 cycle_now = clocksource_read(clock);
64
65 /* calculate the delta since the last update_wall_time: */
66 cycle_delta = (cycle_now - clock->cycle_last) & clock->mask;
67
68 /* convert to nanoseconds: */
69 ns_offset = cyc2ns(clock, cycle_delta);
70
71 return ns_offset;
72}
73
74/**
75 * __get_realtime_clock_ts - Returns the time of day in a timespec
76 * @ts: pointer to the timespec to be set
77 *
78 * Returns the time of day in a timespec. Used by
79 * do_gettimeofday() and get_realtime_clock_ts().
80 */
81static inline void __get_realtime_clock_ts(struct timespec *ts)
82{
83 unsigned long seq;
84 s64 nsecs;
85
86 do {
87 seq = read_seqbegin(&xtime_lock);
88
89 *ts = xtime;
90 nsecs = __get_nsec_offset();
91
92 } while (read_seqretry(&xtime_lock, seq));
93
94 timespec_add_ns(ts, nsecs);
95}
96
97/**
98 * getnstimeofday - Returns the time of day in a timespec
99 * @ts: pointer to the timespec to be set
100 *
101 * Returns the time of day in a timespec.
102 */
103void getnstimeofday(struct timespec *ts)
104{
105 __get_realtime_clock_ts(ts);
106}
107
108EXPORT_SYMBOL(getnstimeofday);
109
110/**
111 * do_gettimeofday - Returns the time of day in a timeval
112 * @tv: pointer to the timeval to be set
113 *
114 * NOTE: Users should be converted to using get_realtime_clock_ts()
115 */
116void do_gettimeofday(struct timeval *tv)
117{
118 struct timespec now;
119
120 __get_realtime_clock_ts(&now);
121 tv->tv_sec = now.tv_sec;
122 tv->tv_usec = now.tv_nsec/1000;
123}
124
125EXPORT_SYMBOL(do_gettimeofday);
126/**
127 * do_settimeofday - Sets the time of day
128 * @tv: pointer to the timespec variable containing the new time
129 *
130 * Sets the time of day to the new time and update NTP and notify hrtimers
131 */
132int do_settimeofday(struct timespec *tv)
133{
134 unsigned long flags;
135 time_t wtm_sec, sec = tv->tv_sec;
136 long wtm_nsec, nsec = tv->tv_nsec;
137
138 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
139 return -EINVAL;
140
141 write_seqlock_irqsave(&xtime_lock, flags);
142
143 nsec -= __get_nsec_offset();
144
145 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - sec);
146 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - nsec);
147
148 set_normalized_timespec(&xtime, sec, nsec);
149 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
150
151 clock->error = 0;
152 ntp_clear();
153
154 update_vsyscall(&xtime, clock);
155
156 write_sequnlock_irqrestore(&xtime_lock, flags);
157
158 /* signal hrtimers about time change */
159 clock_was_set();
160
161 return 0;
162}
163
164EXPORT_SYMBOL(do_settimeofday);
165
166/**
167 * change_clocksource - Swaps clocksources if a new one is available
168 *
169 * Accumulates current time interval and initializes new clocksource
170 */
171static void change_clocksource(void)
172{
173 struct clocksource *new;
174 cycle_t now;
175 u64 nsec;
176
177 new = clocksource_get_next();
178
179 if (clock == new)
180 return;
181
182 now = clocksource_read(new);
183 nsec = __get_nsec_offset();
184 timespec_add_ns(&xtime, nsec);
185
186 clock = new;
187 clock->cycle_last = now;
188
189 clock->error = 0;
190 clock->xtime_nsec = 0;
191 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
192
193 tick_clock_notify();
194
195 printk(KERN_INFO "Time: %s clocksource has been installed.\n",
196 clock->name);
197}
198#else
199static inline void change_clocksource(void) { }
200#endif
201
202/**
203 * timekeeping_is_continuous - check to see if timekeeping is free running
204 */
205int timekeeping_is_continuous(void)
206{
207 unsigned long seq;
208 int ret;
209
210 do {
211 seq = read_seqbegin(&xtime_lock);
212
213 ret = clock->flags & CLOCK_SOURCE_VALID_FOR_HRES;
214
215 } while (read_seqretry(&xtime_lock, seq));
216
217 return ret;
218}
219
220/**
221 * read_persistent_clock - Return time in seconds from the persistent clock.
222 *
223 * Weak dummy function for arches that do not yet support it.
224 * Returns seconds from epoch using the battery backed persistent clock.
225 * Returns zero if unsupported.
226 *
227 * XXX - Do be sure to remove it once all arches implement it.
228 */
229unsigned long __attribute__((weak)) read_persistent_clock(void)
230{
231 return 0;
232}
233
234/*
235 * timekeeping_init - Initializes the clocksource and common timekeeping values
236 */
237void __init timekeeping_init(void)
238{
239 unsigned long flags;
240 unsigned long sec = read_persistent_clock();
241
242 write_seqlock_irqsave(&xtime_lock, flags);
243
244 ntp_clear();
245
246 clock = clocksource_get_next();
247 clocksource_calculate_interval(clock, NTP_INTERVAL_LENGTH);
248 clock->cycle_last = clocksource_read(clock);
249
250 xtime.tv_sec = sec;
251 xtime.tv_nsec = 0;
252 set_normalized_timespec(&wall_to_monotonic,
253 -xtime.tv_sec, -xtime.tv_nsec);
254
255 write_sequnlock_irqrestore(&xtime_lock, flags);
256}
257
258/* flag for if timekeeping is suspended */
259static int timekeeping_suspended;
260/* time in seconds when suspend began */
261static unsigned long timekeeping_suspend_time;
262
263/**
264 * timekeeping_resume - Resumes the generic timekeeping subsystem.
265 * @dev: unused
266 *
267 * This is for the generic clocksource timekeeping.
268 * xtime/wall_to_monotonic/jiffies/etc are
269 * still managed by arch specific suspend/resume code.
270 */
271static int timekeeping_resume(struct sys_device *dev)
272{
273 unsigned long flags;
274 unsigned long now = read_persistent_clock();
275
276 write_seqlock_irqsave(&xtime_lock, flags);
277
278 if (now && (now > timekeeping_suspend_time)) {
279 unsigned long sleep_length = now - timekeeping_suspend_time;
280
281 xtime.tv_sec += sleep_length;
282 wall_to_monotonic.tv_sec -= sleep_length;
283 }
284 /* re-base the last cycle value */
285 clock->cycle_last = clocksource_read(clock);
286 clock->error = 0;
287 timekeeping_suspended = 0;
288 write_sequnlock_irqrestore(&xtime_lock, flags);
289
290 touch_softlockup_watchdog();
291
292 clockevents_notify(CLOCK_EVT_NOTIFY_RESUME, NULL);
293
294 /* Resume hrtimers */
295 hres_timers_resume();
296
297 return 0;
298}
299
300static int timekeeping_suspend(struct sys_device *dev, pm_message_t state)
301{
302 unsigned long flags;
303
304 write_seqlock_irqsave(&xtime_lock, flags);
305 timekeeping_suspended = 1;
306 timekeeping_suspend_time = read_persistent_clock();
307 write_sequnlock_irqrestore(&xtime_lock, flags);
308
309 clockevents_notify(CLOCK_EVT_NOTIFY_SUSPEND, NULL);
310
311 return 0;
312}
313
314/* sysfs resume/suspend bits for timekeeping */
315static struct sysdev_class timekeeping_sysclass = {
316 .resume = timekeeping_resume,
317 .suspend = timekeeping_suspend,
318 set_kset_name("timekeeping"),
319};
320
321static struct sys_device device_timer = {
322 .id = 0,
323 .cls = &timekeeping_sysclass,
324};
325
326static int __init timekeeping_init_device(void)
327{
328 int error = sysdev_class_register(&timekeeping_sysclass);
329 if (!error)
330 error = sysdev_register(&device_timer);
331 return error;
332}
333
334device_initcall(timekeeping_init_device);
335
336/*
337 * If the error is already larger, we look ahead even further
338 * to compensate for late or lost adjustments.
339 */
340static __always_inline int clocksource_bigadjust(s64 error, s64 *interval,
341 s64 *offset)
342{
343 s64 tick_error, i;
344 u32 look_ahead, adj;
345 s32 error2, mult;
346
347 /*
348 * Use the current error value to determine how much to look ahead.
349 * The larger the error the slower we adjust for it to avoid problems
350 * with losing too many ticks, otherwise we would overadjust and
351 * produce an even larger error. The smaller the adjustment the
352 * faster we try to adjust for it, as lost ticks can do less harm
353 * here. This is tuned so that an error of about 1 msec is adusted
354 * within about 1 sec (or 2^20 nsec in 2^SHIFT_HZ ticks).
355 */
356 error2 = clock->error >> (TICK_LENGTH_SHIFT + 22 - 2 * SHIFT_HZ);
357 error2 = abs(error2);
358 for (look_ahead = 0; error2 > 0; look_ahead++)
359 error2 >>= 2;
360
361 /*
362 * Now calculate the error in (1 << look_ahead) ticks, but first
363 * remove the single look ahead already included in the error.
364 */
365 tick_error = current_tick_length() >>
366 (TICK_LENGTH_SHIFT - clock->shift + 1);
367 tick_error -= clock->xtime_interval >> 1;
368 error = ((error - tick_error) >> look_ahead) + tick_error;
369
370 /* Finally calculate the adjustment shift value. */
371 i = *interval;
372 mult = 1;
373 if (error < 0) {
374 error = -error;
375 *interval = -*interval;
376 *offset = -*offset;
377 mult = -1;
378 }
379 for (adj = 0; error > i; adj++)
380 error >>= 1;
381
382 *interval <<= adj;
383 *offset <<= adj;
384 return mult << adj;
385}
386
387/*
388 * Adjust the multiplier to reduce the error value,
389 * this is optimized for the most common adjustments of -1,0,1,
390 * for other values we can do a bit more work.
391 */
392static void clocksource_adjust(struct clocksource *clock, s64 offset)
393{
394 s64 error, interval = clock->cycle_interval;
395 int adj;
396
397 error = clock->error >> (TICK_LENGTH_SHIFT - clock->shift - 1);
398 if (error > interval) {
399 error >>= 2;
400 if (likely(error <= interval))
401 adj = 1;
402 else
403 adj = clocksource_bigadjust(error, &interval, &offset);
404 } else if (error < -interval) {
405 error >>= 2;
406 if (likely(error >= -interval)) {
407 adj = -1;
408 interval = -interval;
409 offset = -offset;
410 } else
411 adj = clocksource_bigadjust(error, &interval, &offset);
412 } else
413 return;
414
415 clock->mult += adj;
416 clock->xtime_interval += interval;
417 clock->xtime_nsec -= offset;
418 clock->error -= (interval - offset) <<
419 (TICK_LENGTH_SHIFT - clock->shift);
420}
421
422/**
423 * update_wall_time - Uses the current clocksource to increment the wall time
424 *
425 * Called from the timer interrupt, must hold a write on xtime_lock.
426 */
427void update_wall_time(void)
428{
429 cycle_t offset;
430
431 /* Make sure we're fully resumed: */
432 if (unlikely(timekeeping_suspended))
433 return;
434
435#ifdef CONFIG_GENERIC_TIME
436 offset = (clocksource_read(clock) - clock->cycle_last) & clock->mask;
437#else
438 offset = clock->cycle_interval;
439#endif
440 clock->xtime_nsec += (s64)xtime.tv_nsec << clock->shift;
441
442 /* normally this loop will run just once, however in the
443 * case of lost or late ticks, it will accumulate correctly.
444 */
445 while (offset >= clock->cycle_interval) {
446 /* accumulate one interval */
447 clock->xtime_nsec += clock->xtime_interval;
448 clock->cycle_last += clock->cycle_interval;
449 offset -= clock->cycle_interval;
450
451 if (clock->xtime_nsec >= (u64)NSEC_PER_SEC << clock->shift) {
452 clock->xtime_nsec -= (u64)NSEC_PER_SEC << clock->shift;
453 xtime.tv_sec++;
454 second_overflow();
455 }
456
457 /* interpolator bits */
458 time_interpolator_update(clock->xtime_interval
459 >> clock->shift);
460
461 /* accumulate error between NTP and clock interval */
462 clock->error += current_tick_length();
463 clock->error -= clock->xtime_interval << (TICK_LENGTH_SHIFT - clock->shift);
464 }
465
466 /* correct the clock when NTP error is too big */
467 clocksource_adjust(clock, offset);
468
469 /* store full nanoseconds into xtime */
470 xtime.tv_nsec = (s64)clock->xtime_nsec >> clock->shift;
471 clock->xtime_nsec -= (s64)xtime.tv_nsec << clock->shift;
472
473 /* check to see if there is a new clocksource to use */
474 change_clocksource();
475 update_vsyscall(&xtime, clock);
476}