xref: /netbsd-src/sys/arch/x86/isa/clock.c (revision 7fa608457b817eca6e0977b37f758ae064f3c99c)
1 /*	$NetBSD: clock.c,v 1.12 2007/10/26 13:24:40 joerg Exp $	*/
2 
3 /*-
4  * Copyright (c) 1990 The Regents of the University of California.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to Berkeley by
8  * William Jolitz and Don Ahn.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. Neither the name of the University nor the names of its contributors
19  *    may be used to endorse or promote products derived from this software
20  *    without specific prior written permission.
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32  * SUCH DAMAGE.
33  *
34  *	@(#)clock.c	7.2 (Berkeley) 5/12/91
35  */
36 /*-
37  * Copyright (c) 1993, 1994 Charles M. Hannum.
38  *
39  * This code is derived from software contributed to Berkeley by
40  * William Jolitz and Don Ahn.
41  *
42  * Redistribution and use in source and binary forms, with or without
43  * modification, are permitted provided that the following conditions
44  * are met:
45  * 1. Redistributions of source code must retain the above copyright
46  *    notice, this list of conditions and the following disclaimer.
47  * 2. Redistributions in binary form must reproduce the above copyright
48  *    notice, this list of conditions and the following disclaimer in the
49  *    documentation and/or other materials provided with the distribution.
50  * 3. All advertising materials mentioning features or use of this software
51  *    must display the following acknowledgement:
52  *	This product includes software developed by the University of
53  *	California, Berkeley and its contributors.
54  * 4. Neither the name of the University nor the names of its contributors
55  *    may be used to endorse or promote products derived from this software
56  *    without specific prior written permission.
57  *
58  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
59  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
60  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
61  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
62  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
63  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
64  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
65  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
66  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
67  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
68  * SUCH DAMAGE.
69  *
70  *	@(#)clock.c	7.2 (Berkeley) 5/12/91
71  */
72 /*
73  * Mach Operating System
74  * Copyright (c) 1991,1990,1989 Carnegie Mellon University
75  * All Rights Reserved.
76  *
77  * Permission to use, copy, modify and distribute this software and its
78  * documentation is hereby granted, provided that both the copyright
79  * notice and this permission notice appear in all copies of the
80  * software, derivative works or modified versions, and any portions
81  * thereof, and that both notices appear in supporting documentation.
82  *
83  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
84  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
85  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
86  *
87  * Carnegie Mellon requests users of this software to return to
88  *
89  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
90  *  School of Computer Science
91  *  Carnegie Mellon University
92  *  Pittsburgh PA 15213-3890
93  *
94  * any improvements or extensions that they make and grant Carnegie Mellon
95  * the rights to redistribute these changes.
96  */
97 /*
98   Copyright 1988, 1989 by Intel Corporation, Santa Clara, California.
99 
100 		All Rights Reserved
101 
102 Permission to use, copy, modify, and distribute this software and
103 its documentation for any purpose and without fee is hereby
104 granted, provided that the above copyright notice appears in all
105 copies and that both the copyright notice and this permission notice
106 appear in supporting documentation, and that the name of Intel
107 not be used in advertising or publicity pertaining to distribution
108 of the software without specific, written prior permission.
109 
110 INTEL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE
111 INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS,
112 IN NO EVENT SHALL INTEL BE LIABLE FOR ANY SPECIAL, INDIRECT, OR
113 CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
114 LOSS OF USE, DATA OR PROFITS, WHETHER IN ACTION OF CONTRACT,
115 NEGLIGENCE, OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
116 WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
117 */
118 
119 /*
120  * Primitive clock interrupt routines.
121  */
122 
123 #include <sys/cdefs.h>
124 __KERNEL_RCSID(0, "$NetBSD: clock.c,v 1.12 2007/10/26 13:24:40 joerg Exp $");
125 
126 /* #define CLOCKDEBUG */
127 /* #define CLOCK_PARANOIA */
128 
129 #include "opt_multiprocessor.h"
130 #include "opt_ntp.h"
131 
132 #include <sys/param.h>
133 #include <sys/systm.h>
134 #include <sys/time.h>
135 #include <sys/timetc.h>
136 #include <sys/kernel.h>
137 #include <sys/device.h>
138 #include <sys/mutex.h>
139 
140 #include <machine/cpu.h>
141 #include <machine/intr.h>
142 #include <machine/pio.h>
143 #include <machine/cpufunc.h>
144 
145 #include <dev/isa/isareg.h>
146 #include <dev/isa/isavar.h>
147 #include <dev/ic/mc146818reg.h>
148 #include <dev/ic/i8253reg.h>
149 #include <i386/isa/nvram.h>
150 #include <x86/x86/tsc.h>
151 #include <dev/clock_subr.h>
152 #include <machine/specialreg.h>
153 
154 #include "config_time.h"		/* for CONFIG_TIME */
155 
156 #ifndef __x86_64__
157 #include "mca.h"
158 #endif
159 #if NMCA > 0
160 #include <machine/mca_machdep.h>	/* for MCA_system */
161 #endif
162 
163 #include "pcppi.h"
164 #if (NPCPPI > 0)
165 #include <dev/isa/pcppivar.h>
166 
167 int sysbeepmatch(struct device *, struct cfdata *, void *);
168 void sysbeepattach(struct device *, struct device *, void *);
169 
170 CFATTACH_DECL(sysbeep, sizeof(struct device),
171     sysbeepmatch, sysbeepattach, NULL, NULL);
172 
173 static int ppi_attached;
174 static pcppi_tag_t ppicookie;
175 #endif /* PCPPI */
176 
177 #ifdef CLOCKDEBUG
178 int clock_debug = 0;
179 #define DPRINTF(arg) if (clock_debug) printf arg
180 #else
181 #define DPRINTF(arg)
182 #endif
183 
184 /* Used by lapic.c */
185 unsigned int	gettick(void);
186 void		sysbeep(int, int);
187 static void     tickle_tc(void);
188 
189 static int	clockintr(void *, struct intrframe *);
190 static void	rtcinit(void);
191 static int	rtcget(mc_todregs *);
192 static void	rtcput(mc_todregs *);
193 
194 static int	cmoscheck(void);
195 
196 static int	clock_expandyear(int);
197 
198 static unsigned int	gettick_broken_latch(void);
199 
200 static volatile uint32_t i8254_lastcount;
201 static volatile uint32_t i8254_offset;
202 static volatile int i8254_ticked;
203 
204 /* to protect TC timer variables */
205 static __cpu_simple_lock_t tmr_lock = __SIMPLELOCK_UNLOCKED;
206 
207 inline u_int mc146818_read(void *, u_int);
208 inline void mc146818_write(void *, u_int, u_int);
209 
210 u_int i8254_get_timecount(struct timecounter *);
211 static void rtc_register(void);
212 
213 static struct timecounter i8254_timecounter = {
214 	i8254_get_timecount,	/* get_timecount */
215 	0,			/* no poll_pps */
216 	~0u,			/* counter_mask */
217 	TIMER_FREQ,		/* frequency */
218 	"i8254",		/* name */
219 	100,			/* quality */
220 	NULL,			/* prev */
221 	NULL,			/* next */
222 };
223 
224 /* XXX use sc? */
225 inline u_int
226 mc146818_read(void *sc, u_int reg)
227 {
228 
229 	outb(IO_RTC, reg);
230 	return (inb(IO_RTC+1));
231 }
232 
233 /* XXX use sc? */
234 inline void
235 mc146818_write(void *sc, u_int reg, u_int datum)
236 {
237 
238 	outb(IO_RTC, reg);
239 	outb(IO_RTC+1, datum);
240 }
241 
242 u_long rtclock_tval;		/* i8254 reload value for countdown */
243 int    rtclock_init = 0;
244 
245 int clock_broken_latch = 0;
246 
247 #ifdef CLOCK_PARANOIA
248 static int ticks[6];
249 #endif
250 /*
251  * i8254 latch check routine:
252  *     National Geode (formerly Cyrix MediaGX) has a serious bug in
253  *     its built-in i8254-compatible clock module.
254  *     machdep sets the variable 'clock_broken_latch' to indicate it.
255  */
256 
257 static unsigned int
258 gettick_broken_latch(void)
259 {
260 	u_long flags;
261 	int v1, v2, v3;
262 	int w1, w2, w3;
263 
264 	/* Don't want someone screwing with the counter while we're here. */
265 	flags = x86_read_psl();
266 	x86_disable_intr();
267 
268 	v1 = inb(IO_TIMER1+TIMER_CNTR0);
269 	v1 |= inb(IO_TIMER1+TIMER_CNTR0) << 8;
270 	v2 = inb(IO_TIMER1+TIMER_CNTR0);
271 	v2 |= inb(IO_TIMER1+TIMER_CNTR0) << 8;
272 	v3 = inb(IO_TIMER1+TIMER_CNTR0);
273 	v3 |= inb(IO_TIMER1+TIMER_CNTR0) << 8;
274 
275 	x86_write_psl(flags);
276 
277 #ifdef CLOCK_PARANOIA
278 	if (clock_debug) {
279 		ticks[0] = ticks[3];
280 		ticks[1] = ticks[4];
281 		ticks[2] = ticks[5];
282 		ticks[3] = v1;
283 		ticks[4] = v2;
284 		ticks[5] = v3;
285 	}
286 #endif
287 
288 	if (v1 >= v2 && v2 >= v3 && v1 - v3 < 0x200)
289 		return (v2);
290 
291 #define _swap_val(a, b) do { \
292 	int c = a; \
293 	a = b; \
294 	b = c; \
295 } while (0)
296 
297 	/*
298 	 * sort v1 v2 v3
299 	 */
300 	if (v1 < v2)
301 		_swap_val(v1, v2);
302 	if (v2 < v3)
303 		_swap_val(v2, v3);
304 	if (v1 < v2)
305 		_swap_val(v1, v2);
306 
307 	/*
308 	 * compute the middle value
309 	 */
310 
311 	if (v1 - v3 < 0x200)
312 		return (v2);
313 
314 	w1 = v2 - v3;
315 	w2 = v3 - v1 + rtclock_tval;
316 	w3 = v1 - v2;
317 	if (w1 >= w2) {
318 		if (w1 >= w3)
319 		        return (v1);
320 	} else {
321 		if (w2 >= w3)
322 			return (v2);
323 	}
324 	return (v3);
325 }
326 
327 /* minimal initialization, enough for delay() */
328 void
329 initrtclock(u_long freq)
330 {
331 	u_long tval;
332 
333 	/*
334 	 * Compute timer_count, the count-down count the timer will be
335 	 * set to.  Also, correctly round
336 	 * this by carrying an extra bit through the division.
337 	 */
338 	tval = (freq * 2) / (u_long) hz;
339 	tval = (tval / 2) + (tval & 0x1);
340 
341 	/* initialize 8254 clock */
342 	outb(IO_TIMER1+TIMER_MODE, TIMER_SEL0|TIMER_RATEGEN|TIMER_16BIT);
343 
344 	/* Correct rounding will buy us a better precision in timekeeping */
345 	outb(IO_TIMER1+TIMER_CNTR0, tval % 256);
346 	outb(IO_TIMER1+TIMER_CNTR0, tval / 256);
347 
348 	rtclock_tval = tval ? tval : 0xFFFF;
349 	rtclock_init = 1;
350 }
351 
352 void
353 startrtclock(void)
354 {
355 	int s;
356 
357 	if (!rtclock_init)
358 		initrtclock(TIMER_FREQ);
359 
360 	/* Check diagnostic status */
361 	if ((s = mc146818_read(NULL, NVRAM_DIAG)) != 0) { /* XXX softc */
362 		char bits[128];
363 		printf("RTC BIOS diagnostic error %s\n",
364 		    bitmask_snprintf(s, NVRAM_DIAG_BITS, bits, sizeof(bits)));
365 	}
366 
367 	tc_init(&i8254_timecounter);
368 
369 #if defined(I586_CPU) || defined(I686_CPU) || defined(__x86_64__)
370 	init_TSC();
371 #endif
372 
373 	rtc_register();
374 }
375 
376 /*
377  * Must be called at splclock().
378  */
379 static void
380 tickle_tc(void)
381 {
382 #if defined(MULTIPROCESSOR)
383 	struct cpu_info *ci = curcpu();
384 	/*
385 	 * If we are not the primary CPU, we're not allowed to do
386 	 * any more work.
387 	 */
388 	if (CPU_IS_PRIMARY(ci) == 0)
389 		return;
390 #endif
391 	if (rtclock_tval && timecounter->tc_get_timecount == i8254_get_timecount) {
392 		__cpu_simple_lock(&tmr_lock);
393 		if (i8254_ticked)
394 			i8254_ticked    = 0;
395 		else {
396 			i8254_offset   += rtclock_tval;
397 			i8254_lastcount = 0;
398 		}
399 		__cpu_simple_unlock(&tmr_lock);
400 	}
401 
402 }
403 
404 static int
405 clockintr(void *arg, struct intrframe *frame)
406 {
407 	tickle_tc();
408 
409 	hardclock((struct clockframe *)frame);
410 
411 #if NMCA > 0
412 	if (MCA_system) {
413 		/* Reset PS/2 clock interrupt by asserting bit 7 of port 0x61 */
414 		outb(0x61, inb(0x61) | 0x80);
415 	}
416 #endif
417 	return -1;
418 }
419 
420 u_int
421 i8254_get_timecount(struct timecounter *tc)
422 {
423 	u_int count;
424 	u_char high, low;
425 	u_long flags;
426 
427 	/* Don't want someone screwing with the counter while we're here. */
428 	flags = x86_read_psl();
429 	x86_disable_intr();
430 	__cpu_simple_lock(&tmr_lock);
431 
432 	/* Select timer0 and latch counter value. */
433 	outb(IO_TIMER1 + TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
434 
435 	low = inb(IO_TIMER1 + TIMER_CNTR0);
436 	high = inb(IO_TIMER1 + TIMER_CNTR0);
437 	count = rtclock_tval - ((high << 8) | low);
438 
439 	if (rtclock_tval && (count < i8254_lastcount || !i8254_ticked)) {
440 		i8254_ticked = 1;
441 		i8254_offset += rtclock_tval;
442 	}
443 
444 	i8254_lastcount = count;
445 	count += i8254_offset;
446 
447 	__cpu_simple_unlock(&tmr_lock);
448 	x86_write_psl(flags);
449 
450 	return (count);
451 }
452 
453 unsigned int
454 gettick(void)
455 {
456 	u_long flags;
457 	u_char lo, hi;
458 
459 	if (clock_broken_latch)
460 		return (gettick_broken_latch());
461 
462 	/* Don't want someone screwing with the counter while we're here. */
463 	flags = x86_read_psl();
464 	x86_disable_intr();
465 	/* Select counter 0 and latch it. */
466 	outb(IO_TIMER1+TIMER_MODE, TIMER_SEL0 | TIMER_LATCH);
467 	lo = inb(IO_TIMER1+TIMER_CNTR0);
468 	hi = inb(IO_TIMER1+TIMER_CNTR0);
469 	x86_write_psl(flags);
470 	return ((hi << 8) | lo);
471 }
472 
473 /*
474  * Wait approximately `n' microseconds.
475  * Relies on timer 1 counting down from (TIMER_FREQ / hz) at TIMER_FREQ Hz.
476  * Note: timer had better have been programmed before this is first used!
477  * (Note that we use `rate generator' mode, which counts at 1:1; `square
478  * wave' mode counts at 2:1).
479  * Don't rely on this being particularly accurate.
480  */
481 void
482 i8254_delay(unsigned int n)
483 {
484 	unsigned int cur_tick, initial_tick;
485 	int remaining;
486 	static const int delaytab[26] = {
487 		 0,  2,  3,  4,  5,  6,  7,  9, 10, 11,
488 		12, 13, 15, 16, 17, 18, 19, 21, 22, 23,
489 		24, 25, 27, 28, 29, 30,
490 	};
491 
492 	/* allow DELAY() to be used before startrtclock() */
493 	if (!rtclock_init)
494 		initrtclock(TIMER_FREQ);
495 
496 	/*
497 	 * Read the counter first, so that the rest of the setup overhead is
498 	 * counted.
499 	 */
500 	initial_tick = gettick();
501 
502 	if (n <= 25)
503 		remaining = delaytab[n];
504 	else if (n <= UINT_MAX / TIMER_FREQ) {
505 		/*
506 		 * For unsigned arithmetic, division can be replaced with
507 		 * multiplication with the inverse and a shift.
508 		 */
509 		remaining = n * TIMER_FREQ / 1000000;
510 	} else {
511 		/* This is a very long delay.
512 		 * Being slow here doesn't matter.
513 		 */
514 		remaining = (unsigned long long) n * TIMER_FREQ / 1000000;
515 	}
516 
517 	while (remaining > 0) {
518 #ifdef CLOCK_PARANOIA
519 		int delta;
520 		cur_tick = gettick();
521 		if (cur_tick > initial_tick)
522 			delta = rtclock_tval - (cur_tick - initial_tick);
523 		else
524 			delta = initial_tick - cur_tick;
525 		if (delta < 0 || delta >= rtclock_tval / 2) {
526 			DPRINTF(("delay: ignore ticks %.4x-%.4x",
527 				 initial_tick, cur_tick));
528 			if (clock_broken_latch) {
529 				DPRINTF(("  (%.4x %.4x %.4x %.4x %.4x %.4x)\n",
530 				         ticks[0], ticks[1], ticks[2],
531 				         ticks[3], ticks[4], ticks[5]));
532 			} else {
533 				DPRINTF(("\n"));
534 			}
535 		} else
536 			remaining -= delta;
537 #else
538 		cur_tick = gettick();
539 		if (cur_tick > initial_tick)
540 			remaining -= rtclock_tval - (cur_tick - initial_tick);
541 		else
542 			remaining -= initial_tick - cur_tick;
543 #endif
544 		initial_tick = cur_tick;
545 	}
546 }
547 
548 #if (NPCPPI > 0)
549 int
550 sysbeepmatch(struct device *parent, struct cfdata *match,
551     void *aux)
552 {
553 	return (!ppi_attached);
554 }
555 
556 void
557 sysbeepattach(struct device *parent, struct device *self,
558     void *aux)
559 {
560 	aprint_naive("\n");
561 	aprint_normal("\n");
562 
563 	ppicookie = ((struct pcppi_attach_args *)aux)->pa_cookie;
564 	ppi_attached = 1;
565 }
566 #endif
567 
568 void
569 sysbeep(int pitch, int period)
570 {
571 #if (NPCPPI > 0)
572 	if (ppi_attached)
573 		pcppi_bell(ppicookie, pitch, period, 0);
574 #endif
575 }
576 
577 void
578 i8254_initclocks(void)
579 {
580 
581 	/*
582 	 * XXX If you're doing strange things with multiple clocks, you might
583 	 * want to keep track of clock handlers.
584 	 */
585 	(void)isa_intr_establish(NULL, 0, IST_PULSE, IPL_CLOCK,
586 	    (int (*)(void *))clockintr, 0);
587 }
588 
589 static void
590 rtcinit(void)
591 {
592 	static int first_rtcopen_ever = 1;
593 
594 	if (!first_rtcopen_ever)
595 		return;
596 	first_rtcopen_ever = 0;
597 
598 	mc146818_write(NULL, MC_REGA,			/* XXX softc */
599 	    MC_BASE_32_KHz | MC_RATE_1024_Hz);
600 	mc146818_write(NULL, MC_REGB, MC_REGB_24HR);	/* XXX softc */
601 }
602 
603 static int
604 rtcget(mc_todregs *regs)
605 {
606 
607 	rtcinit();
608 	if ((mc146818_read(NULL, MC_REGD) & MC_REGD_VRT) == 0) /* XXX softc */
609 		return (-1);
610 	MC146818_GETTOD(NULL, regs);			/* XXX softc */
611 	return (0);
612 }
613 
614 static void
615 rtcput(mc_todregs *regs)
616 {
617 
618 	rtcinit();
619 	MC146818_PUTTOD(NULL, regs);			/* XXX softc */
620 }
621 
622 /*
623  * check whether the CMOS layout is "standard"-like (ie, not PS/2-like),
624  * to be called at splclock()
625  */
626 static int
627 cmoscheck(void)
628 {
629 	int i;
630 	unsigned short cksum = 0;
631 
632 	for (i = 0x10; i <= 0x2d; i++)
633 		cksum += mc146818_read(NULL, i); /* XXX softc */
634 
635 	return (cksum == (mc146818_read(NULL, 0x2e) << 8)
636 			  + mc146818_read(NULL, 0x2f));
637 }
638 
639 #if NMCA > 0
640 /*
641  * Check whether the CMOS layout is PS/2 like, to be called at splclock().
642  */
643 static int cmoscheckps2(void);
644 static int
645 cmoscheckps2(void)
646 {
647 #if 0
648 	/* Disabled until I find out the CRC checksum algorithm IBM uses */
649 	int i;
650 	unsigned short cksum = 0;
651 
652 	for (i = 0x10; i <= 0x31; i++)
653 		cksum += mc146818_read(NULL, i); /* XXX softc */
654 
655 	return (cksum == (mc146818_read(NULL, 0x32) << 8)
656 			  + mc146818_read(NULL, 0x33));
657 #else
658 	/* Check 'incorrect checksum' bit of IBM PS/2 Diagnostic Status Byte */
659 	return ((mc146818_read(NULL, NVRAM_DIAG) & (1<<6)) == 0);
660 #endif
661 }
662 #endif /* NMCA > 0 */
663 
664 /*
665  * patchable to control century byte handling:
666  * 1: always update
667  * -1: never touch
668  * 0: try to figure out itself
669  */
670 int rtc_update_century = 0;
671 
672 /*
673  * Expand a two-digit year as read from the clock chip
674  * into full width.
675  * Being here, deal with the CMOS century byte.
676  */
677 static int centb = NVRAM_CENTURY;
678 static int
679 clock_expandyear(int clockyear)
680 {
681 	int s, clockcentury, cmoscentury;
682 
683 	clockcentury = (clockyear < 70) ? 20 : 19;
684 	clockyear += 100 * clockcentury;
685 
686 	if (rtc_update_century < 0)
687 		return (clockyear);
688 
689 	s = splclock();
690 	if (cmoscheck())
691 		cmoscentury = mc146818_read(NULL, NVRAM_CENTURY);
692 #if NMCA > 0
693 	else if (MCA_system && cmoscheckps2())
694 		cmoscentury = mc146818_read(NULL, (centb = 0x37));
695 #endif
696 	else
697 		cmoscentury = 0;
698 	splx(s);
699 	if (!cmoscentury) {
700 #ifdef DIAGNOSTIC
701 		printf("clock: unknown CMOS layout\n");
702 #endif
703 		return (clockyear);
704 	}
705 	cmoscentury = bcdtobin(cmoscentury);
706 
707 	if (cmoscentury != clockcentury) {
708 		/* XXX note: saying "century is 20" might confuse the naive. */
709 		printf("WARNING: NVRAM century is %d but RTC year is %d\n",
710 		       cmoscentury, clockyear);
711 
712 		/* Kludge to roll over century. */
713 		if ((rtc_update_century > 0) ||
714 		    ((cmoscentury == 19) && (clockcentury == 20) &&
715 		     (clockyear == 2000))) {
716 			printf("WARNING: Setting NVRAM century to %d\n",
717 			       clockcentury);
718 			s = splclock();
719 			mc146818_write(NULL, centb, bintobcd(clockcentury));
720 			splx(s);
721 		}
722 	} else if (cmoscentury == 19 && rtc_update_century == 0)
723 		rtc_update_century = 1; /* will update later in resettodr() */
724 
725 	return (clockyear);
726 }
727 
728 static int
729 rtc_get_ymdhms(todr_chip_handle_t tch, struct clock_ymdhms *dt)
730 {
731 	int s;
732 	mc_todregs rtclk;
733 
734 	s = splclock();
735 	if (rtcget(&rtclk)) {
736 		splx(s);
737 		return -1;
738 	}
739 	splx(s);
740 
741 	dt->dt_sec = bcdtobin(rtclk[MC_SEC]);
742 	dt->dt_min = bcdtobin(rtclk[MC_MIN]);
743 	dt->dt_hour = bcdtobin(rtclk[MC_HOUR]);
744 	dt->dt_day = bcdtobin(rtclk[MC_DOM]);
745 	dt->dt_mon = bcdtobin(rtclk[MC_MONTH]);
746 	dt->dt_year = clock_expandyear(bcdtobin(rtclk[MC_YEAR]));
747 
748 	return 0;
749 }
750 
751 static int
752 rtc_set_ymdhms(todr_chip_handle_t tch, struct clock_ymdhms *dt)
753 {
754 	mc_todregs rtclk;
755 	int century;
756 	int s;
757 
758 	s = splclock();
759 	if (rtcget(&rtclk))
760 		memset(&rtclk, 0, sizeof(rtclk));
761 	splx(s);
762 
763 	rtclk[MC_SEC] = bintobcd(dt->dt_sec);
764 	rtclk[MC_MIN] = bintobcd(dt->dt_min);
765 	rtclk[MC_HOUR] = bintobcd(dt->dt_hour);
766 	rtclk[MC_DOW] = dt->dt_wday + 1;
767 	rtclk[MC_YEAR] = bintobcd(dt->dt_year % 100);
768 	rtclk[MC_MONTH] = bintobcd(dt->dt_mon);
769 	rtclk[MC_DOM] = bintobcd(dt->dt_day);
770 
771 #ifdef DEBUG_CLOCK
772 	printf("setclock: %x/%x/%x %x:%x:%x\n", rtclk[MC_YEAR], rtclk[MC_MONTH],
773 	   rtclk[MC_DOM], rtclk[MC_HOUR], rtclk[MC_MIN], rtclk[MC_SEC]);
774 #endif
775 	s = splclock();
776 	rtcput(&rtclk);
777 	if (rtc_update_century > 0) {
778 		century = bintobcd(dt->dt_year / 100);
779 		mc146818_write(NULL, centb, century); /* XXX softc */
780 	}
781 	splx(s);
782 	return 0;
783 
784 }
785 
786 static void
787 rtc_register(void)
788 {
789 	static struct todr_chip_handle	tch;
790 	tch.todr_gettime_ymdhms = rtc_get_ymdhms;
791 	tch.todr_settime_ymdhms = rtc_set_ymdhms;
792 	tch.todr_setwen = NULL;
793 
794 	todr_attach(&tch);
795 }
796 
797 void
798 setstatclockrate(int arg)
799 {
800 }
801