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