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*/
1 /*
2 * linux/kernel/time.c
3 *
4 * Copyright (C) 1991, 1992 Linus Torvalds
5 *
6 * This file contains the interface functions for the various
7 * time related system calls: time, stime, gettimeofday, settimeofday,
8 * adjtime
9 */
10 /*
11 * Modification history kernel/time.c
12 *
13 * 1993-09-02 Philip Gladstone
14 * Created file with time related functions from sched.c and adjtimex()
15 * 1993-10-08 Torsten Duwe
16 * adjtime interface update and CMOS clock write code
17 * 1994-07-02 Alan Modra
18 * fixed set_rtc_mmss, fixed time.year for >= 2000, new mktime
19 * 1995-03-26 Markus Kuhn
20 * fixed 500 ms bug at call to set_rtc_mmss, fixed DS12887
21 * precision CMOS clock update
22 *
23 * to do: adjtimex() has to be updated to recent (1994-12-13) revision
24 * of David Mill's kernel clock model. For more information, check
25 * <ftp://louie.udel.edu/pub/ntp/kernel.tar.Z>.
26 */
27
28 #include <linux/errno.h>
29 #include <linux/sched.h>
30 #include <linux/kernel.h>
31 #include <linux/param.h>
32 #include <linux/string.h>
33 #include <linux/mm.h>
34
35 #include <asm/segment.h>
36 #include <asm/io.h>
37
38 #include <linux/mc146818rtc.h>
39 #include <linux/timex.h>
40
41 /* Converts Gregorian date to seconds since 1970-01-01 00:00:00.
42 * Assumes input in normal date format, i.e. 1980-12-31 23:59:59
43 * => year=1980, mon=12, day=31, hour=23, min=59, sec=59.
44 *
45 * [For the Julian calendar (which was used in Russia before 1917,
46 * Britain & colonies before 1752, anywhere else before 1582,
47 * and is still in use by some communities) leave out the
48 * -year/100+year/400 terms, and add 10.]
49 *
50 * This algorithm was first published by Gauss (I think).
51 *
52 * WARNING: this function will overflow on 2106-02-07 06:28:16 on
53 * machines were long is 32-bit! (However, as time_t is signed, we
54 * will already get problems at other places on 2038-01-19 03:14:08)
55 */
56 static inline unsigned long mktime(unsigned int year, unsigned int mon,
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57 unsigned int day, unsigned int hour,
58 unsigned int min, unsigned int sec)
59 {
60 if (0 >= (int) (mon -= 2)) { /* 1..12 -> 11,12,1..10 */
61 mon += 12; /* Puts Feb last since it has leap day */
62 year -= 1;
63 }
64 return (((
65 (unsigned long)(year/4 - year/100 + year/400 + 367*mon/12 + day) +
66 year*365 - 719499
67 )*24 + hour /* now have hours */
68 )*60 + min /* now have minutes */
69 )*60 + sec; /* finally seconds */
70 }
71
72 void time_init(void)
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*/
73 {
74 unsigned int year, mon, day, hour, min, sec;
75 int i;
76
77 /* The Linux interpretation of the CMOS clock register contents:
78 * When the Update-In-Progress (UIP) flag goes from 1 to 0, the
79 * RTC registers show the second which has precisely just started.
80 * Let's hope other operating systems interpret the RTC the same way.
81 */
82 /* read RTC exactly on falling edge of update flag */
83 for (i = 0 ; i < 1000000 ; i++) /* may take up to 1 second... */
84 if (CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP)
85 break;
86 for (i = 0 ; i < 1000000 ; i++) /* must try at least 2.228 ms */
87 if (!(CMOS_READ(RTC_FREQ_SELECT) & RTC_UIP))
88 break;
89 do { /* Isn't this overkill ? UIP above should guarantee consistency */
90 sec = CMOS_READ(RTC_SECONDS);
91 min = CMOS_READ(RTC_MINUTES);
92 hour = CMOS_READ(RTC_HOURS);
93 day = CMOS_READ(RTC_DAY_OF_MONTH);
94 mon = CMOS_READ(RTC_MONTH);
95 year = CMOS_READ(RTC_YEAR);
96 } while (sec != CMOS_READ(RTC_SECONDS));
97 if (!(CMOS_READ(RTC_CONTROL) & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
98 {
99 BCD_TO_BIN(sec);
100 BCD_TO_BIN(min);
101 BCD_TO_BIN(hour);
102 BCD_TO_BIN(day);
103 BCD_TO_BIN(mon);
104 BCD_TO_BIN(year);
105 }
106 #if defined(__alpha__) && defined(CONFIG_PCI)
107 /*
108 * The meaning of life, the universe, and everything. Plus
109 * this makes the year come out right.
110 */
111 year -= 42;
112 #endif
113 if ((year += 1900) < 1970)
114 year += 100;
115 xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
116 xtime.tv_usec = 0;
117 }
118
119 /*
120 * The timezone where the local system is located. Used as a default by some
121 * programs who obtain this value by using gettimeofday.
122 */
123 struct timezone sys_tz = { 0, 0};
124
125 asmlinkage int sys_time(int * tloc)
/* */
126 {
127 int i, error;
128
129 i = CURRENT_TIME;
130 if (tloc) {
131 error = verify_area(VERIFY_WRITE, tloc, sizeof(*tloc));
132 if (error)
133 return error;
134 put_user(i,tloc);
135 }
136 return i;
137 }
138
139 asmlinkage int sys_stime(int * tptr)
/* */
140 {
141 int error, value;
142
143 if (!suser())
144 return -EPERM;
145 error = verify_area(VERIFY_READ, tptr, sizeof(*tptr));
146 if (error)
147 return error;
148 value = get_user(tptr);
149 cli();
150 xtime.tv_sec = value;
151 xtime.tv_usec = 0;
152 time_status = TIME_BAD;
153 time_maxerror = 0x70000000;
154 time_esterror = 0x70000000;
155 sti();
156 return 0;
157 }
158
159 /* This function must be called with interrupts disabled
160 * It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs
161 *
162 * However, the pc-audio speaker driver changes the divisor so that
163 * it gets interrupted rather more often - it loads 64 into the
164 * counter rather than 11932! This has an adverse impact on
165 * do_gettimeoffset() -- it stops working! What is also not
166 * good is that the interval that our timer function gets called
167 * is no longer 10.0002 ms, but 9.9767 ms. To get around this
168 * would require using a different timing source. Maybe someone
169 * could use the RTC - I know that this can interrupt at frequencies
170 * ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix
171 * it so that at startup, the timer code in sched.c would select
172 * using either the RTC or the 8253 timer. The decision would be
173 * based on whether there was any other device around that needed
174 * to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz,
175 * and then do some jiggery to have a version of do_timer that
176 * advanced the clock by 1/1024 s. Every time that reached over 1/100
177 * of a second, then do all the old code. If the time was kept correct
178 * then do_gettimeoffset could just return 0 - there is no low order
179 * divider that can be accessed.
180 *
181 * Ideally, you would be able to use the RTC for the speaker driver,
182 * but it appears that the speaker driver really needs interrupt more
183 * often than every 120 us or so.
184 *
185 * Anyway, this needs more thought.... pjsg (1993-08-28)
186 *
187 * If you are really that interested, you should be reading
188 * comp.protocols.time.ntp!
189 */
190
191 #define TICK_SIZE tick
192
193 static inline unsigned long do_gettimeoffset(void)
/* */
194 {
195 int count;
196 unsigned long offset = 0;
197
198 /* timer count may underflow right here */
199 outb_p(0x00, 0x43); /* latch the count ASAP */
200 count = inb_p(0x40); /* read the latched count */
201 count |= inb(0x40) << 8;
202 /* we know probability of underflow is always MUCH less than 1% */
203 if (count > (LATCH - LATCH/100)) {
204 /* check for pending timer interrupt */
205 outb_p(0x0a, 0x20);
206 if (inb(0x20) & 1)
207 offset = TICK_SIZE;
208 }
209 count = ((LATCH-1) - count) * TICK_SIZE;
210 count = (count + LATCH/2) / LATCH;
211 return offset + count;
212 }
213
214 /*
215 * This version of gettimeofday has near microsecond resolution.
216 */
217 void do_gettimeofday(struct timeval *tv)
/* */
218 {
219 unsigned long flags;
220
221 save_flags(flags);
222 cli();
223 *tv = xtime;
224 #if defined (__i386__) || defined (__mips__)
225 tv->tv_usec += do_gettimeoffset();
226 if (tv->tv_usec >= 1000000) {
227 tv->tv_usec -= 1000000;
228 tv->tv_sec++;
229 }
230 #endif /* !defined (__i386__) && !defined (__mips__) */
231 restore_flags(flags);
232 }
233
234 asmlinkage int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
/* */
235 {
236 int error;
237
238 if (tv) {
239 struct timeval ktv;
240 error = verify_area(VERIFY_WRITE, tv, sizeof *tv);
241 if (error)
242 return error;
243 do_gettimeofday(&ktv);
244 memcpy_tofs(tv, &ktv, sizeof(ktv));
245 }
246 if (tz) {
247 error = verify_area(VERIFY_WRITE, tz, sizeof *tz);
248 if (error)
249 return error;
250 memcpy_tofs(tz, &sys_tz, sizeof(sys_tz));
251 }
252 return 0;
253 }
254
255 /*
256 * Adjust the time obtained from the CMOS to be UTC time instead of
257 * local time.
258 *
259 * This is ugly, but preferable to the alternatives. Otherwise we
260 * would either need to write a program to do it in /etc/rc (and risk
261 * confusion if the program gets run more than once; it would also be
262 * hard to make the program warp the clock precisely n hours) or
263 * compile in the timezone information into the kernel. Bad, bad....
264 *
265 * - TYT, 1992-01-01
266 *
267 * The best thing to do is to keep the CMOS clock in universal time (UTC)
268 * as real UNIX machines always do it. This avoids all headaches about
269 * daylight saving times and warping kernel clocks.
270 */
271 inline static void warp_clock(void)
/* */
272 {
273 cli();
274 xtime.tv_sec += sys_tz.tz_minuteswest * 60;
275 sti();
276 }
277
278 /*
279 * In case for some reason the CMOS clock has not already been running
280 * in UTC, but in some local time: The first time we set the timezone,
281 * we will warp the clock so that it is ticking UTC time instead of
282 * local time. Presumably, if someone is setting the timezone then we
283 * are running in an environment where the programs understand about
284 * timezones. This should be done at boot time in the /etc/rc script,
285 * as soon as possible, so that the clock can be set right. Otherwise,
286 * various programs will get confused when the clock gets warped.
287 */
288 asmlinkage int sys_settimeofday(struct timeval *tv, struct timezone *tz)
/* */
289 {
290 static int firsttime = 1;
291 struct timeval new_tv;
292 struct timezone new_tz;
293
294 if (!suser())
295 return -EPERM;
296 if (tv) {
297 int error = verify_area(VERIFY_READ, tv, sizeof(*tv));
298 if (error)
299 return error;
300 memcpy_fromfs(&new_tv, tv, sizeof(*tv));
301 }
302 if (tz) {
303 int error = verify_area(VERIFY_READ, tz, sizeof(*tz));
304 if (error)
305 return error;
306 memcpy_fromfs(&new_tz, tz, sizeof(*tz));
307 }
308 if (tz) {
309 sys_tz = new_tz;
310 if (firsttime) {
311 firsttime = 0;
312 if (!tv)
313 warp_clock();
314 }
315 }
316 if (tv) {
317 cli();
318 /* This is revolting. We need to set the xtime.tv_usec
319 * correctly. However, the value in this location is
320 * is value at the last tick.
321 * Discover what correction gettimeofday
322 * would have done, and then undo it!
323 */
324 new_tv.tv_usec -= do_gettimeoffset();
325
326 if (new_tv.tv_usec < 0) {
327 new_tv.tv_usec += 1000000;
328 new_tv.tv_sec--;
329 }
330
331 xtime = new_tv;
332 time_status = TIME_BAD;
333 time_maxerror = 0x70000000;
334 time_esterror = 0x70000000;
335 sti();
336 }
337 return 0;
338 }
339
340 /* adjtimex mainly allows reading (and writing, if superuser) of
341 * kernel time-keeping variables. used by xntpd.
342 */
343 asmlinkage int sys_adjtimex(struct timex *txc_p)
/* */
344 {
345 long ltemp, mtemp, save_adjust;
346 int error;
347
348 /* Local copy of parameter */
349 struct timex txc;
350
351 error = verify_area(VERIFY_WRITE, txc_p, sizeof(struct timex));
352 if (error)
353 return error;
354
355 /* Copy the user data space into the kernel copy
356 * structure. But bear in mind that the structures
357 * may change
358 */
359 memcpy_fromfs(&txc, txc_p, sizeof(struct timex));
360
361 /* In order to modify anything, you gotta be super-user! */
362 if (txc.mode && !suser())
363 return -EPERM;
364
365 /* Now we validate the data before disabling interrupts
366 */
367
368 if (txc.mode != ADJ_OFFSET_SINGLESHOT && (txc.mode & ADJ_OFFSET))
369 /* Microsec field limited to -131000 .. 131000 usecs */
370 if (txc.offset <= -(1 << (31 - SHIFT_UPDATE))
371 || txc.offset >= (1 << (31 - SHIFT_UPDATE)))
372 return -EINVAL;
373
374 /* time_status must be in a fairly small range */
375 if (txc.mode & ADJ_STATUS)
376 if (txc.status < TIME_OK || txc.status > TIME_BAD)
377 return -EINVAL;
378
379 /* if the quartz is off by more than 10% something is VERY wrong ! */
380 if (txc.mode & ADJ_TICK)
381 if (txc.tick < 900000/HZ || txc.tick > 1100000/HZ)
382 return -EINVAL;
383
384 cli();
385
386 /* Save for later - semantics of adjtime is to return old value */
387 save_adjust = time_adjust;
388
389 /* If there are input parameters, then process them */
390 if (txc.mode)
391 {
392 if (time_status == TIME_BAD)
393 time_status = TIME_OK;
394
395 if (txc.mode & ADJ_STATUS)
396 time_status = txc.status;
397
398 if (txc.mode & ADJ_FREQUENCY)
399 time_freq = txc.frequency << (SHIFT_KF - 16);
400
401 if (txc.mode & ADJ_MAXERROR)
402 time_maxerror = txc.maxerror;
403
404 if (txc.mode & ADJ_ESTERROR)
405 time_esterror = txc.esterror;
406
407 if (txc.mode & ADJ_TIMECONST)
408 time_constant = txc.time_constant;
409
410 if (txc.mode & ADJ_OFFSET)
411 if (txc.mode == ADJ_OFFSET_SINGLESHOT)
412 {
413 time_adjust = txc.offset;
414 }
415 else /* XXX should give an error if other bits set */
416 {
417 time_offset = txc.offset << SHIFT_UPDATE;
418 mtemp = xtime.tv_sec - time_reftime;
419 time_reftime = xtime.tv_sec;
420 if (mtemp > (MAXSEC+2) || mtemp < 0)
421 mtemp = 0;
422
423 if (txc.offset < 0)
424 time_freq -= (-txc.offset * mtemp) >>
425 (time_constant + time_constant);
426 else
427 time_freq += (txc.offset * mtemp) >>
428 (time_constant + time_constant);
429
430 ltemp = time_tolerance << SHIFT_KF;
431
432 if (time_freq > ltemp)
433 time_freq = ltemp;
434 else if (time_freq < -ltemp)
435 time_freq = -ltemp;
436 }
437 if (txc.mode & ADJ_TICK)
438 tick = txc.tick;
439
440 }
441 txc.offset = save_adjust;
442 txc.frequency = ((time_freq+1) >> (SHIFT_KF - 16));
443 txc.maxerror = time_maxerror;
444 txc.esterror = time_esterror;
445 txc.status = time_status;
446 txc.time_constant = time_constant;
447 txc.precision = time_precision;
448 txc.tolerance = time_tolerance;
449 txc.time = xtime;
450 txc.tick = tick;
451
452 sti();
453
454 memcpy_tofs(txc_p, &txc, sizeof(struct timex));
455 return time_status;
456 }
457
458 /*
459 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
460 * called 500 ms after the second nowtime has started, because when
461 * nowtime is written into the registers of the CMOS clock, it will
462 * jump to the next second precisely 500 ms later. Check the Motorola
463 * MC146818A or Dallas DS12887 data sheet for details.
464 */
465 int set_rtc_mmss(unsigned long nowtime)
/* ![[last]](../icons/n_last.png)
*/
466 {
467 int retval = 0;
468 int real_seconds, real_minutes, cmos_minutes;
469 unsigned char save_control, save_freq_select;
470
471 save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
472 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
473
474 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
475 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
476
477 cmos_minutes = CMOS_READ(RTC_MINUTES);
478 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
479 BCD_TO_BIN(cmos_minutes);
480
481 /* since we're only adjusting minutes and seconds,
482 * don't interfere with hour overflow. This avoids
483 * messing with unknown time zones but requires your
484 * RTC not to be off by more than 15 minutes
485 */
486 real_seconds = nowtime % 60;
487 real_minutes = nowtime / 60;
488 if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
489 real_minutes += 30; /* correct for half hour time zone */
490 real_minutes %= 60;
491
492 if (abs(real_minutes - cmos_minutes) < 30)
493 {
494 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
495 {
496 BIN_TO_BCD(real_seconds);
497 BIN_TO_BCD(real_minutes);
498 }
499 CMOS_WRITE(real_seconds,RTC_SECONDS);
500 CMOS_WRITE(real_minutes,RTC_MINUTES);
501 }
502 else
503 retval = -1;
504
505 /* The following flags have to be released exactly in this order,
506 * otherwise the DS12887 (popular MC146818A clone with integrated
507 * battery and quartz) will not reset the oscillator and will not
508 * update precisely 500 ms later. You won't find this mentioned in
509 * the Dallas Semiconductor data sheets, but who believes data
510 * sheets anyway ... -- Markus Kuhn
511 */
512 CMOS_WRITE(save_control, RTC_CONTROL);
513 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
514
515 return retval;
516 }
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*/