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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-04-16 18:20:36 -0400
commit1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 (patch)
tree0bba044c4ce775e45a88a51686b5d9f90697ea9d /arch/ppc/kernel/time.c
Linux-2.6.12-rc2v2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
Diffstat (limited to 'arch/ppc/kernel/time.c')
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diff --git a/arch/ppc/kernel/time.c b/arch/ppc/kernel/time.c
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1/*
2 * Common time routines among all ppc machines.
3 *
4 * Written by Cort Dougan (cort@cs.nmt.edu) to merge
5 * Paul Mackerras' version and mine for PReP and Pmac.
6 * MPC8xx/MBX changes by Dan Malek (dmalek@jlc.net).
7 *
8 * First round of bugfixes by Gabriel Paubert (paubert@iram.es)
9 * to make clock more stable (2.4.0-test5). The only thing
10 * that this code assumes is that the timebases have been synchronized
11 * by firmware on SMP and are never stopped (never do sleep
12 * on SMP then, nap and doze are OK).
13 *
14 * TODO (not necessarily in this file):
15 * - improve precision and reproducibility of timebase frequency
16 * measurement at boot time.
17 * - get rid of xtime_lock for gettimeofday (generic kernel problem
18 * to be implemented on all architectures for SMP scalability and
19 * eventually implementing gettimeofday without entering the kernel).
20 * - put all time/clock related variables in a single structure
21 * to minimize number of cache lines touched by gettimeofday()
22 * - for astronomical applications: add a new function to get
23 * non ambiguous timestamps even around leap seconds. This needs
24 * a new timestamp format and a good name.
25 *
26 *
27 * The following comment is partially obsolete (at least the long wait
28 * is no more a valid reason):
29 * Since the MPC8xx has a programmable interrupt timer, I decided to
30 * use that rather than the decrementer. Two reasons: 1.) the clock
31 * frequency is low, causing 2.) a long wait in the timer interrupt
32 * while ((d = get_dec()) == dval)
33 * loop. The MPC8xx can be driven from a variety of input clocks,
34 * so a number of assumptions have been made here because the kernel
35 * parameter HZ is a constant. We assume (correctly, today :-) that
36 * the MPC8xx on the MBX board is driven from a 32.768 kHz crystal.
37 * This is then divided by 4, providing a 8192 Hz clock into the PIT.
38 * Since it is not possible to get a nice 100 Hz clock out of this, without
39 * creating a software PLL, I have set HZ to 128. -- Dan
40 *
41 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
42 * "A Kernel Model for Precision Timekeeping" by Dave Mills
43 */
44
45#include <linux/config.h>
46#include <linux/errno.h>
47#include <linux/sched.h>
48#include <linux/kernel.h>
49#include <linux/param.h>
50#include <linux/string.h>
51#include <linux/mm.h>
52#include <linux/module.h>
53#include <linux/interrupt.h>
54#include <linux/timex.h>
55#include <linux/kernel_stat.h>
56#include <linux/mc146818rtc.h>
57#include <linux/time.h>
58#include <linux/init.h>
59#include <linux/profile.h>
60
61#include <asm/segment.h>
62#include <asm/io.h>
63#include <asm/nvram.h>
64#include <asm/cache.h>
65#include <asm/8xx_immap.h>
66#include <asm/machdep.h>
67
68#include <asm/time.h>
69
70/* XXX false sharing with below? */
71u64 jiffies_64 = INITIAL_JIFFIES;
72
73EXPORT_SYMBOL(jiffies_64);
74
75unsigned long disarm_decr[NR_CPUS];
76
77extern struct timezone sys_tz;
78
79/* keep track of when we need to update the rtc */
80time_t last_rtc_update;
81
82/* The decrementer counts down by 128 every 128ns on a 601. */
83#define DECREMENTER_COUNT_601 (1000000000 / HZ)
84
85unsigned tb_ticks_per_jiffy;
86unsigned tb_to_us;
87unsigned tb_last_stamp;
88unsigned long tb_to_ns_scale;
89
90extern unsigned long wall_jiffies;
91
92static long time_offset;
93
94DEFINE_SPINLOCK(rtc_lock);
95
96EXPORT_SYMBOL(rtc_lock);
97
98/* Timer interrupt helper function */
99static inline int tb_delta(unsigned *jiffy_stamp) {
100 int delta;
101 if (__USE_RTC()) {
102 delta = get_rtcl();
103 if (delta < *jiffy_stamp) *jiffy_stamp -= 1000000000;
104 delta -= *jiffy_stamp;
105 } else {
106 delta = get_tbl() - *jiffy_stamp;
107 }
108 return delta;
109}
110
111#ifdef CONFIG_SMP
112unsigned long profile_pc(struct pt_regs *regs)
113{
114 unsigned long pc = instruction_pointer(regs);
115
116 if (in_lock_functions(pc))
117 return regs->link;
118
119 return pc;
120}
121EXPORT_SYMBOL(profile_pc);
122#endif
123
124/*
125 * timer_interrupt - gets called when the decrementer overflows,
126 * with interrupts disabled.
127 * We set it up to overflow again in 1/HZ seconds.
128 */
129void timer_interrupt(struct pt_regs * regs)
130{
131 int next_dec;
132 unsigned long cpu = smp_processor_id();
133 unsigned jiffy_stamp = last_jiffy_stamp(cpu);
134 extern void do_IRQ(struct pt_regs *);
135
136 if (atomic_read(&ppc_n_lost_interrupts) != 0)
137 do_IRQ(regs);
138
139 irq_enter();
140
141 while ((next_dec = tb_ticks_per_jiffy - tb_delta(&jiffy_stamp)) <= 0) {
142 jiffy_stamp += tb_ticks_per_jiffy;
143
144 profile_tick(CPU_PROFILING, regs);
145 update_process_times(user_mode(regs));
146
147 if (smp_processor_id())
148 continue;
149
150 /* We are in an interrupt, no need to save/restore flags */
151 write_seqlock(&xtime_lock);
152 tb_last_stamp = jiffy_stamp;
153 do_timer(regs);
154
155 /*
156 * update the rtc when needed, this should be performed on the
157 * right fraction of a second. Half or full second ?
158 * Full second works on mk48t59 clocks, others need testing.
159 * Note that this update is basically only used through
160 * the adjtimex system calls. Setting the HW clock in
161 * any other way is a /dev/rtc and userland business.
162 * This is still wrong by -0.5/+1.5 jiffies because of the
163 * timer interrupt resolution and possible delay, but here we
164 * hit a quantization limit which can only be solved by higher
165 * resolution timers and decoupling time management from timer
166 * interrupts. This is also wrong on the clocks
167 * which require being written at the half second boundary.
168 * We should have an rtc call that only sets the minutes and
169 * seconds like on Intel to avoid problems with non UTC clocks.
170 */
171 if ( ppc_md.set_rtc_time && (time_status & STA_UNSYNC) == 0 &&
172 xtime.tv_sec - last_rtc_update >= 659 &&
173 abs((xtime.tv_nsec / 1000) - (1000000-1000000/HZ)) < 500000/HZ &&
174 jiffies - wall_jiffies == 1) {
175 if (ppc_md.set_rtc_time(xtime.tv_sec+1 + time_offset) == 0)
176 last_rtc_update = xtime.tv_sec+1;
177 else
178 /* Try again one minute later */
179 last_rtc_update += 60;
180 }
181 write_sequnlock(&xtime_lock);
182 }
183 if ( !disarm_decr[smp_processor_id()] )
184 set_dec(next_dec);
185 last_jiffy_stamp(cpu) = jiffy_stamp;
186
187 if (ppc_md.heartbeat && !ppc_md.heartbeat_count--)
188 ppc_md.heartbeat();
189
190 irq_exit();
191}
192
193/*
194 * This version of gettimeofday has microsecond resolution.
195 */
196void do_gettimeofday(struct timeval *tv)
197{
198 unsigned long flags;
199 unsigned long seq;
200 unsigned delta, lost_ticks, usec, sec;
201
202 do {
203 seq = read_seqbegin_irqsave(&xtime_lock, flags);
204 sec = xtime.tv_sec;
205 usec = (xtime.tv_nsec / 1000);
206 delta = tb_ticks_since(tb_last_stamp);
207#ifdef CONFIG_SMP
208 /* As long as timebases are not in sync, gettimeofday can only
209 * have jiffy resolution on SMP.
210 */
211 if (!smp_tb_synchronized)
212 delta = 0;
213#endif /* CONFIG_SMP */
214 lost_ticks = jiffies - wall_jiffies;
215 } while (read_seqretry_irqrestore(&xtime_lock, seq, flags));
216
217 usec += mulhwu(tb_to_us, tb_ticks_per_jiffy * lost_ticks + delta);
218 while (usec >= 1000000) {
219 sec++;
220 usec -= 1000000;
221 }
222 tv->tv_sec = sec;
223 tv->tv_usec = usec;
224}
225
226EXPORT_SYMBOL(do_gettimeofday);
227
228int do_settimeofday(struct timespec *tv)
229{
230 time_t wtm_sec, new_sec = tv->tv_sec;
231 long wtm_nsec, new_nsec = tv->tv_nsec;
232 unsigned long flags;
233 int tb_delta;
234
235 if ((unsigned long)tv->tv_nsec >= NSEC_PER_SEC)
236 return -EINVAL;
237
238 write_seqlock_irqsave(&xtime_lock, flags);
239 /* Updating the RTC is not the job of this code. If the time is
240 * stepped under NTP, the RTC will be update after STA_UNSYNC
241 * is cleared. Tool like clock/hwclock either copy the RTC
242 * to the system time, in which case there is no point in writing
243 * to the RTC again, or write to the RTC but then they don't call
244 * settimeofday to perform this operation. Note also that
245 * we don't touch the decrementer since:
246 * a) it would lose timer interrupt synchronization on SMP
247 * (if it is working one day)
248 * b) it could make one jiffy spuriously shorter or longer
249 * which would introduce another source of uncertainty potentially
250 * harmful to relatively short timers.
251 */
252
253 /* This works perfectly on SMP only if the tb are in sync but
254 * guarantees an error < 1 jiffy even if they are off by eons,
255 * still reasonable when gettimeofday resolution is 1 jiffy.
256 */
257 tb_delta = tb_ticks_since(last_jiffy_stamp(smp_processor_id()));
258 tb_delta += (jiffies - wall_jiffies) * tb_ticks_per_jiffy;
259
260 new_nsec -= 1000 * mulhwu(tb_to_us, tb_delta);
261
262 wtm_sec = wall_to_monotonic.tv_sec + (xtime.tv_sec - new_sec);
263 wtm_nsec = wall_to_monotonic.tv_nsec + (xtime.tv_nsec - new_nsec);
264
265 set_normalized_timespec(&xtime, new_sec, new_nsec);
266 set_normalized_timespec(&wall_to_monotonic, wtm_sec, wtm_nsec);
267
268 /* In case of a large backwards jump in time with NTP, we want the
269 * clock to be updated as soon as the PLL is again in lock.
270 */
271 last_rtc_update = new_sec - 658;
272
273 time_adjust = 0; /* stop active adjtime() */
274 time_status |= STA_UNSYNC;
275 time_state = TIME_ERROR; /* p. 24, (a) */
276 time_maxerror = NTP_PHASE_LIMIT;
277 time_esterror = NTP_PHASE_LIMIT;
278 write_sequnlock_irqrestore(&xtime_lock, flags);
279 clock_was_set();
280 return 0;
281}
282
283EXPORT_SYMBOL(do_settimeofday);
284
285/* This function is only called on the boot processor */
286void __init time_init(void)
287{
288 time_t sec, old_sec;
289 unsigned old_stamp, stamp, elapsed;
290
291 if (ppc_md.time_init != NULL)
292 time_offset = ppc_md.time_init();
293
294 if (__USE_RTC()) {
295 /* 601 processor: dec counts down by 128 every 128ns */
296 tb_ticks_per_jiffy = DECREMENTER_COUNT_601;
297 /* mulhwu_scale_factor(1000000000, 1000000) is 0x418937 */
298 tb_to_us = 0x418937;
299 } else {
300 ppc_md.calibrate_decr();
301 tb_to_ns_scale = mulhwu(tb_to_us, 1000 << 10);
302 }
303
304 /* Now that the decrementer is calibrated, it can be used in case the
305 * clock is stuck, but the fact that we have to handle the 601
306 * makes things more complex. Repeatedly read the RTC until the
307 * next second boundary to try to achieve some precision. If there
308 * is no RTC, we still need to set tb_last_stamp and
309 * last_jiffy_stamp(cpu 0) to the current stamp.
310 */
311 stamp = get_native_tbl();
312 if (ppc_md.get_rtc_time) {
313 sec = ppc_md.get_rtc_time();
314 elapsed = 0;
315 do {
316 old_stamp = stamp;
317 old_sec = sec;
318 stamp = get_native_tbl();
319 if (__USE_RTC() && stamp < old_stamp)
320 old_stamp -= 1000000000;
321 elapsed += stamp - old_stamp;
322 sec = ppc_md.get_rtc_time();
323 } while ( sec == old_sec && elapsed < 2*HZ*tb_ticks_per_jiffy);
324 if (sec==old_sec)
325 printk("Warning: real time clock seems stuck!\n");
326 xtime.tv_sec = sec;
327 xtime.tv_nsec = 0;
328 /* No update now, we just read the time from the RTC ! */
329 last_rtc_update = xtime.tv_sec;
330 }
331 last_jiffy_stamp(0) = tb_last_stamp = stamp;
332
333 /* Not exact, but the timer interrupt takes care of this */
334 set_dec(tb_ticks_per_jiffy);
335
336 /* If platform provided a timezone (pmac), we correct the time */
337 if (time_offset) {
338 sys_tz.tz_minuteswest = -time_offset / 60;
339 sys_tz.tz_dsttime = 0;
340 xtime.tv_sec -= time_offset;
341 }
342 set_normalized_timespec(&wall_to_monotonic,
343 -xtime.tv_sec, -xtime.tv_nsec);
344}
345
346#define FEBRUARY 2
347#define STARTOFTIME 1970
348#define SECDAY 86400L
349#define SECYR (SECDAY * 365)
350
351/*
352 * Note: this is wrong for 2100, but our signed 32-bit time_t will
353 * have overflowed long before that, so who cares. -- paulus
354 */
355#define leapyear(year) ((year) % 4 == 0)
356#define days_in_year(a) (leapyear(a) ? 366 : 365)
357#define days_in_month(a) (month_days[(a) - 1])
358
359static int month_days[12] = {
360 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
361};
362
363void to_tm(int tim, struct rtc_time * tm)
364{
365 register int i;
366 register long hms, day, gday;
367
368 gday = day = tim / SECDAY;
369 hms = tim % SECDAY;
370
371 /* Hours, minutes, seconds are easy */
372 tm->tm_hour = hms / 3600;
373 tm->tm_min = (hms % 3600) / 60;
374 tm->tm_sec = (hms % 3600) % 60;
375
376 /* Number of years in days */
377 for (i = STARTOFTIME; day >= days_in_year(i); i++)
378 day -= days_in_year(i);
379 tm->tm_year = i;
380
381 /* Number of months in days left */
382 if (leapyear(tm->tm_year))
383 days_in_month(FEBRUARY) = 29;
384 for (i = 1; day >= days_in_month(i); i++)
385 day -= days_in_month(i);
386 days_in_month(FEBRUARY) = 28;
387 tm->tm_mon = i;
388
389 /* Days are what is left over (+1) from all that. */
390 tm->tm_mday = day + 1;
391
392 /*
393 * Determine the day of week. Jan. 1, 1970 was a Thursday.
394 */
395 tm->tm_wday = (gday + 4) % 7;
396}
397
398/* Auxiliary function to compute scaling factors */
399/* Actually the choice of a timebase running at 1/4 the of the bus
400 * frequency giving resolution of a few tens of nanoseconds is quite nice.
401 * It makes this computation very precise (27-28 bits typically) which
402 * is optimistic considering the stability of most processor clock
403 * oscillators and the precision with which the timebase frequency
404 * is measured but does not harm.
405 */
406unsigned mulhwu_scale_factor(unsigned inscale, unsigned outscale) {
407 unsigned mlt=0, tmp, err;
408 /* No concern for performance, it's done once: use a stupid
409 * but safe and compact method to find the multiplier.
410 */
411 for (tmp = 1U<<31; tmp != 0; tmp >>= 1) {
412 if (mulhwu(inscale, mlt|tmp) < outscale) mlt|=tmp;
413 }
414 /* We might still be off by 1 for the best approximation.
415 * A side effect of this is that if outscale is too large
416 * the returned value will be zero.
417 * Many corner cases have been checked and seem to work,
418 * some might have been forgotten in the test however.
419 */
420 err = inscale*(mlt+1);
421 if (err <= inscale/2) mlt++;
422 return mlt;
423}
424
425unsigned long long sched_clock(void)
426{
427 unsigned long lo, hi, hi2;
428 unsigned long long tb;
429
430 if (!__USE_RTC()) {
431 do {
432 hi = get_tbu();
433 lo = get_tbl();
434 hi2 = get_tbu();
435 } while (hi2 != hi);
436 tb = ((unsigned long long) hi << 32) | lo;
437 tb = (tb * tb_to_ns_scale) >> 10;
438 } else {
439 do {
440 hi = get_rtcu();
441 lo = get_rtcl();
442 hi2 = get_rtcu();
443 } while (hi2 != hi);
444 tb = ((unsigned long long) hi) * 1000000000 + lo;
445 }
446 return tb;
447}