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