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