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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)
/* ![[previous]](../icons/left.png)
*/
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 ((year += 1900) < 1970)
107 year += 100;
108 xtime.tv_sec = mktime(year, mon, day, hour, min, sec);
109 xtime.tv_usec = 0;
110 }
111
112 /*
113 * The timezone where the local system is located. Used as a default by some
114 * programs who obtain this value by using gettimeofday.
115 */
116 struct timezone sys_tz = { 0, 0};
117
118 asmlinkage int sys_time(long * tloc)
/* */
119 {
120 int i, error;
121
122 i = CURRENT_TIME;
123 if (tloc) {
124 error = verify_area(VERIFY_WRITE, tloc, 4);
125 if (error)
126 return error;
127 put_fs_long(i,(unsigned long *)tloc);
128 }
129 return i;
130 }
131
132 asmlinkage int sys_stime(unsigned long * tptr)
/* */
133 {
134 int error;
135 unsigned long value;
136
137 if (!suser())
138 return -EPERM;
139 error = verify_area(VERIFY_READ, tptr, sizeof(*tptr));
140 if (error)
141 return error;
142 value = get_fs_long(tptr);
143 cli();
144 xtime.tv_sec = value;
145 xtime.tv_usec = 0;
146 time_status = TIME_BAD;
147 time_maxerror = 0x70000000;
148 time_esterror = 0x70000000;
149 sti();
150 return 0;
151 }
152
153 /* This function must be called with interrupts disabled
154 * It was inspired by Steve McCanne's microtime-i386 for BSD. -- jrs
155 *
156 * However, the pc-audio speaker driver changes the divisor so that
157 * it gets interrupted rather more often - it loads 64 into the
158 * counter rather than 11932! This has an adverse impact on
159 * do_gettimeoffset() -- it stops working! What is also not
160 * good is that the interval that our timer function gets called
161 * is no longer 10.0002 ms, but 9.9767 ms. To get around this
162 * would require using a different timing source. Maybe someone
163 * could use the RTC - I know that this can interrupt at frequencies
164 * ranging from 8192Hz to 2Hz. If I had the energy, I'd somehow fix
165 * it so that at startup, the timer code in sched.c would select
166 * using either the RTC or the 8253 timer. The decision would be
167 * based on whether there was any other device around that needed
168 * to trample on the 8253. I'd set up the RTC to interrupt at 1024 Hz,
169 * and then do some jiggery to have a version of do_timer that
170 * advanced the clock by 1/1024 s. Every time that reached over 1/100
171 * of a second, then do all the old code. If the time was kept correct
172 * then do_gettimeoffset could just return 0 - there is no low order
173 * divider that can be accessed.
174 *
175 * Ideally, you would be able to use the RTC for the speaker driver,
176 * but it appears that the speaker driver really needs interrupt more
177 * often than every 120 us or so.
178 *
179 * Anyway, this needs more thought.... pjsg (1993-08-28)
180 *
181 * If you are really that interested, you should be reading
182 * comp.protocols.time.ntp!
183 */
184
185 #define TICK_SIZE tick
186
187 static inline unsigned long do_gettimeoffset(void)
/* */
188 {
189 int count;
190 unsigned long offset = 0;
191
192 /* timer count may underflow right here */
193 outb_p(0x00, 0x43); /* latch the count ASAP */
194 count = inb_p(0x40); /* read the latched count */
195 count |= inb(0x40) << 8;
196 /* we know probability of underflow is always MUCH less than 1% */
197 if (count > (LATCH - LATCH/100)) {
198 /* check for pending timer interrupt */
199 outb_p(0x0a, 0x20);
200 if (inb(0x20) & 1)
201 offset = TICK_SIZE;
202 }
203 count = ((LATCH-1) - count) * TICK_SIZE;
204 count = (count + LATCH/2) / LATCH;
205 return offset + count;
206 }
207
208 /*
209 * This version of gettimeofday has near microsecond resolution.
210 */
211 void do_gettimeofday(struct timeval *tv)
/* */
212 {
213 unsigned long flags;
214
215 save_flags(flags);
216 cli();
217 *tv = xtime;
218 #if defined (__i386__) || defined (__mips__)
219 tv->tv_usec += do_gettimeoffset();
220 if (tv->tv_usec >= 1000000) {
221 tv->tv_usec -= 1000000;
222 tv->tv_sec++;
223 }
224 #endif /* !defined (__i386__) && !defined (__mips__) */
225 restore_flags(flags);
226 }
227
228 asmlinkage int sys_gettimeofday(struct timeval *tv, struct timezone *tz)
/* */
229 {
230 int error;
231
232 if (tv) {
233 struct timeval ktv;
234 error = verify_area(VERIFY_WRITE, tv, sizeof *tv);
235 if (error)
236 return error;
237 do_gettimeofday(&ktv);
238 memcpy_tofs(tv, &ktv, sizeof(ktv));
239 }
240 if (tz) {
241 error = verify_area(VERIFY_WRITE, tz, sizeof *tz);
242 if (error)
243 return error;
244 memcpy_tofs(tz, &sys_tz, sizeof(sys_tz));
245 }
246 return 0;
247 }
248
249 /*
250 * Adjust the time obtained from the CMOS to be UTC time instead of
251 * local time.
252 *
253 * This is ugly, but preferable to the alternatives. Otherwise we
254 * would either need to write a program to do it in /etc/rc (and risk
255 * confusion if the program gets run more than once; it would also be
256 * hard to make the program warp the clock precisely n hours) or
257 * compile in the timezone information into the kernel. Bad, bad....
258 *
259 * - TYT, 1992-01-01
260 *
261 * The best thing to do is to keep the CMOS clock in universal time (UTC)
262 * as real UNIX machines always do it. This avoids all headaches about
263 * daylight saving times and warping kernel clocks.
264 */
265 inline static void warp_clock(void)
/* */
266 {
267 cli();
268 xtime.tv_sec += sys_tz.tz_minuteswest * 60;
269 sti();
270 }
271
272 /*
273 * In case for some reason the CMOS clock has not already been running
274 * in UTC, but in some local time: The first time we set the timezone,
275 * we will warp the clock so that it is ticking UTC time instead of
276 * local time. Presumably, if someone is setting the timezone then we
277 * are running in an environment where the programs understand about
278 * timezones. This should be done at boot time in the /etc/rc script,
279 * as soon as possible, so that the clock can be set right. Otherwise,
280 * various programs will get confused when the clock gets warped.
281 */
282 asmlinkage int sys_settimeofday(struct timeval *tv, struct timezone *tz)
/* */
283 {
284 static int firsttime = 1;
285 struct timeval new_tv;
286 struct timezone new_tz;
287
288 if (!suser())
289 return -EPERM;
290 if (tv) {
291 int error = verify_area(VERIFY_READ, tv, sizeof(*tv));
292 if (error)
293 return error;
294 memcpy_fromfs(&new_tv, tv, sizeof(*tv));
295 }
296 if (tz) {
297 int error = verify_area(VERIFY_READ, tz, sizeof(*tz));
298 if (error)
299 return error;
300 memcpy_fromfs(&new_tz, tz, sizeof(*tz));
301 }
302 if (tz) {
303 sys_tz = new_tz;
304 if (firsttime) {
305 firsttime = 0;
306 if (!tv)
307 warp_clock();
308 }
309 }
310 if (tv) {
311 cli();
312 /* This is revolting. We need to set the xtime.tv_usec
313 * correctly. However, the value in this location is
314 * is value at the last tick.
315 * Discover what correction gettimeofday
316 * would have done, and then undo it!
317 */
318 new_tv.tv_usec -= do_gettimeoffset();
319
320 if (new_tv.tv_usec < 0) {
321 new_tv.tv_usec += 1000000;
322 new_tv.tv_sec--;
323 }
324
325 xtime = new_tv;
326 time_status = TIME_BAD;
327 time_maxerror = 0x70000000;
328 time_esterror = 0x70000000;
329 sti();
330 }
331 return 0;
332 }
333
334 /* adjtimex mainly allows reading (and writing, if superuser) of
335 * kernel time-keeping variables. used by xntpd.
336 */
337 asmlinkage int sys_adjtimex(struct timex *txc_p)
/* */
338 {
339 long ltemp, mtemp, save_adjust;
340 int error;
341
342 /* Local copy of parameter */
343 struct timex txc;
344
345 error = verify_area(VERIFY_WRITE, txc_p, sizeof(struct timex));
346 if (error)
347 return error;
348
349 /* Copy the user data space into the kernel copy
350 * structure. But bear in mind that the structures
351 * may change
352 */
353 memcpy_fromfs(&txc, txc_p, sizeof(struct timex));
354
355 /* In order to modify anything, you gotta be super-user! */
356 if (txc.mode && !suser())
357 return -EPERM;
358
359 /* Now we validate the data before disabling interrupts
360 */
361
362 if (txc.mode != ADJ_OFFSET_SINGLESHOT && (txc.mode & ADJ_OFFSET))
363 /* Microsec field limited to -131000 .. 131000 usecs */
364 if (txc.offset <= -(1 << (31 - SHIFT_UPDATE))
365 || txc.offset >= (1 << (31 - SHIFT_UPDATE)))
366 return -EINVAL;
367
368 /* time_status must be in a fairly small range */
369 if (txc.mode & ADJ_STATUS)
370 if (txc.status < TIME_OK || txc.status > TIME_BAD)
371 return -EINVAL;
372
373 /* if the quartz is off by more than 10% something is VERY wrong ! */
374 if (txc.mode & ADJ_TICK)
375 if (txc.tick < 900000/HZ || txc.tick > 1100000/HZ)
376 return -EINVAL;
377
378 cli();
379
380 /* Save for later - semantics of adjtime is to return old value */
381 save_adjust = time_adjust;
382
383 /* If there are input parameters, then process them */
384 if (txc.mode)
385 {
386 if (time_status == TIME_BAD)
387 time_status = TIME_OK;
388
389 if (txc.mode & ADJ_STATUS)
390 time_status = txc.status;
391
392 if (txc.mode & ADJ_FREQUENCY)
393 time_freq = txc.frequency << (SHIFT_KF - 16);
394
395 if (txc.mode & ADJ_MAXERROR)
396 time_maxerror = txc.maxerror;
397
398 if (txc.mode & ADJ_ESTERROR)
399 time_esterror = txc.esterror;
400
401 if (txc.mode & ADJ_TIMECONST)
402 time_constant = txc.time_constant;
403
404 if (txc.mode & ADJ_OFFSET)
405 if (txc.mode == ADJ_OFFSET_SINGLESHOT)
406 {
407 time_adjust = txc.offset;
408 }
409 else /* XXX should give an error if other bits set */
410 {
411 time_offset = txc.offset << SHIFT_UPDATE;
412 mtemp = xtime.tv_sec - time_reftime;
413 time_reftime = xtime.tv_sec;
414 if (mtemp > (MAXSEC+2) || mtemp < 0)
415 mtemp = 0;
416
417 if (txc.offset < 0)
418 time_freq -= (-txc.offset * mtemp) >>
419 (time_constant + time_constant);
420 else
421 time_freq += (txc.offset * mtemp) >>
422 (time_constant + time_constant);
423
424 ltemp = time_tolerance << SHIFT_KF;
425
426 if (time_freq > ltemp)
427 time_freq = ltemp;
428 else if (time_freq < -ltemp)
429 time_freq = -ltemp;
430 }
431 if (txc.mode & ADJ_TICK)
432 tick = txc.tick;
433
434 }
435 txc.offset = save_adjust;
436 txc.frequency = ((time_freq+1) >> (SHIFT_KF - 16));
437 txc.maxerror = time_maxerror;
438 txc.esterror = time_esterror;
439 txc.status = time_status;
440 txc.time_constant = time_constant;
441 txc.precision = time_precision;
442 txc.tolerance = time_tolerance;
443 txc.time = xtime;
444 txc.tick = tick;
445
446 sti();
447
448 memcpy_tofs(txc_p, &txc, sizeof(struct timex));
449 return time_status;
450 }
451
452 /*
453 * In order to set the CMOS clock precisely, set_rtc_mmss has to be
454 * called 500 ms after the second nowtime has started, because when
455 * nowtime is written into the registers of the CMOS clock, it will
456 * jump to the next second precisely 500 ms later. Check the Motorola
457 * MC146818A or Dallas DS12887 data sheet for details.
458 */
459 int set_rtc_mmss(unsigned long nowtime)
/* ![[last]](../icons/n_last.png)
*/
460 {
461 int retval = 0;
462 int real_seconds, real_minutes, cmos_minutes;
463 unsigned char save_control, save_freq_select;
464
465 save_control = CMOS_READ(RTC_CONTROL); /* tell the clock it's being set */
466 CMOS_WRITE((save_control|RTC_SET), RTC_CONTROL);
467
468 save_freq_select = CMOS_READ(RTC_FREQ_SELECT); /* stop and reset prescaler */
469 CMOS_WRITE((save_freq_select|RTC_DIV_RESET2), RTC_FREQ_SELECT);
470
471 cmos_minutes = CMOS_READ(RTC_MINUTES);
472 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
473 BCD_TO_BIN(cmos_minutes);
474
475 /* since we're only adjusting minutes and seconds,
476 * don't interfere with hour overflow. This avoids
477 * messing with unknown time zones but requires your
478 * RTC not to be off by more than 15 minutes
479 */
480 real_seconds = nowtime % 60;
481 real_minutes = nowtime / 60;
482 if (((abs(real_minutes - cmos_minutes) + 15)/30) & 1)
483 real_minutes += 30; /* correct for half hour time zone */
484 real_minutes %= 60;
485
486 if (abs(real_minutes - cmos_minutes) < 30)
487 {
488 if (!(save_control & RTC_DM_BINARY) || RTC_ALWAYS_BCD)
489 {
490 BIN_TO_BCD(real_seconds);
491 BIN_TO_BCD(real_minutes);
492 }
493 CMOS_WRITE(real_seconds,RTC_SECONDS);
494 CMOS_WRITE(real_minutes,RTC_MINUTES);
495 }
496 else
497 retval = -1;
498
499 /* The following flags have to be released exactly in this order,
500 * otherwise the DS12887 (popular MC146818A clone with integrated
501 * battery and quartz) will not reset the oscillator and will not
502 * update precisely 500 ms later. You won't find this mentioned in
503 * the Dallas Semiconductor data sheets, but who believes data
504 * sheets anyway ... -- Markus Kuhn
505 */
506 CMOS_WRITE(save_control, RTC_CONTROL);
507 CMOS_WRITE(save_freq_select, RTC_FREQ_SELECT);
508
509 return retval;
510 }
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*/