xref: /netbsd-src/sys/dev/i2c/ds1307.c (revision 6a493d6bc668897c91594964a732d38505b70cbb)
1 /*	$NetBSD: ds1307.c,v 1.16 2012/07/25 03:07:37 matt Exp $	*/
2 
3 /*
4  * Copyright (c) 2003 Wasabi Systems, Inc.
5  * All rights reserved.
6  *
7  * Written by Steve C. Woodford and Jason R. Thorpe for Wasabi Systems, Inc.
8  *
9  * Redistribution and use in source and binary forms, with or without
10  * modification, are permitted provided that the following conditions
11  * are met:
12  * 1. Redistributions of source code must retain the above copyright
13  *    notice, this list of conditions and the following disclaimer.
14  * 2. Redistributions in binary form must reproduce the above copyright
15  *    notice, this list of conditions and the following disclaimer in the
16  *    documentation and/or other materials provided with the distribution.
17  * 3. All advertising materials mentioning features or use of this software
18  *    must display the following acknowledgement:
19  *      This product includes software developed for the NetBSD Project by
20  *      Wasabi Systems, Inc.
21  * 4. The name of Wasabi Systems, Inc. may not be used to endorse
22  *    or promote products derived from this software without specific prior
23  *    written permission.
24  *
25  * THIS SOFTWARE IS PROVIDED BY WASABI SYSTEMS, INC. ``AS IS'' AND
26  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
27  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
28  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL WASABI SYSTEMS, INC
29  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
30  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
31  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
32  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
33  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
34  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
35  * POSSIBILITY OF SUCH DAMAGE.
36  */
37 
38 #include <sys/cdefs.h>
39 __KERNEL_RCSID(0, "$NetBSD: ds1307.c,v 1.16 2012/07/25 03:07:37 matt Exp $");
40 
41 #include <sys/param.h>
42 #include <sys/systm.h>
43 #include <sys/device.h>
44 #include <sys/kernel.h>
45 #include <sys/fcntl.h>
46 #include <sys/uio.h>
47 #include <sys/conf.h>
48 #include <sys/event.h>
49 
50 #include <dev/clock_subr.h>
51 
52 #include <dev/i2c/i2cvar.h>
53 #include <dev/i2c/ds1307reg.h>
54 
55 struct dsrtc_model {
56 	uint16_t dm_model;
57 	uint8_t dm_ch_reg;
58 	uint8_t dm_ch_value;
59 	uint8_t dm_rtc_start;
60 	uint8_t dm_rtc_size;
61 	uint8_t dm_nvram_start;
62 	uint8_t dm_nvram_size;
63 	uint8_t dm_flags;
64 #define	DSRTC_FLAG_CLOCK_HOLD	1
65 #define	DSRTC_FLAG_BCD		2
66 };
67 
68 static const struct dsrtc_model dsrtc_models[] = {
69 	{
70 		.dm_model = 1307,
71 		.dm_ch_reg = DSXXXX_SECONDS,
72 		.dm_ch_value = DS1307_SECONDS_CH,
73 		.dm_rtc_start = DS1307_RTC_START,
74 		.dm_rtc_size = DS1307_RTC_SIZE,
75 		.dm_nvram_start = DS1307_NVRAM_START,
76 		.dm_nvram_size = DS1307_NVRAM_SIZE,
77 		.dm_flags = DSRTC_FLAG_BCD | DSRTC_FLAG_CLOCK_HOLD,
78 	}, {
79 		.dm_model = 1339,
80 		.dm_rtc_start = DS1339_RTC_START,
81 		.dm_rtc_size = DS1339_RTC_SIZE,
82 		.dm_flags = DSRTC_FLAG_BCD,
83 	}, {
84 		.dm_model = 1672,
85 		.dm_rtc_start = DS1672_RTC_START,
86 		.dm_rtc_size = DS1672_RTC_SIZE,
87 		.dm_flags = 0,
88 	}, {
89 		.dm_model = 3232,
90 		.dm_rtc_start = DS3232_RTC_START,
91 		.dm_rtc_size = DS3232_RTC_SIZE,
92 		.dm_nvram_start = DS3232_NVRAM_START,
93 		.dm_nvram_size = DS3232_NVRAM_SIZE,
94 		.dm_flags = DSRTC_FLAG_BCD,
95 	},
96 };
97 
98 struct dsrtc_softc {
99 	device_t sc_dev;
100 	i2c_tag_t sc_tag;
101 	uint8_t sc_address;
102 	bool sc_open;
103 	struct dsrtc_model sc_model;
104 	struct todr_chip_handle sc_todr;
105 };
106 
107 static void	dsrtc_attach(device_t, device_t, void *);
108 static int	dsrtc_match(device_t, cfdata_t, void *);
109 
110 CFATTACH_DECL_NEW(dsrtc, sizeof(struct dsrtc_softc),
111     dsrtc_match, dsrtc_attach, NULL, NULL);
112 extern struct cfdriver dsrtc_cd;
113 
114 dev_type_open(dsrtc_open);
115 dev_type_close(dsrtc_close);
116 dev_type_read(dsrtc_read);
117 dev_type_write(dsrtc_write);
118 
119 const struct cdevsw dsrtc_cdevsw = {
120 	dsrtc_open, dsrtc_close, dsrtc_read, dsrtc_write, noioctl,
121 	nostop, notty, nopoll, nommap, nokqfilter, D_OTHER
122 };
123 
124 static int dsrtc_gettime_ymdhms(struct todr_chip_handle *, struct clock_ymdhms *);
125 static int dsrtc_settime_ymdhms(struct todr_chip_handle *, struct clock_ymdhms *);
126 static int dsrtc_clock_read_ymdhms(struct dsrtc_softc *, struct clock_ymdhms *);
127 static int dsrtc_clock_write_ymdhms(struct dsrtc_softc *, struct clock_ymdhms *);
128 
129 static int dsrtc_gettime_timeval(struct todr_chip_handle *, struct timeval *);
130 static int dsrtc_settime_timeval(struct todr_chip_handle *, struct timeval *);
131 static int dsrtc_clock_read_timeval(struct dsrtc_softc *, time_t *);
132 static int dsrtc_clock_write_timeval(struct dsrtc_softc *, time_t);
133 
134 static const struct dsrtc_model *
135 dsrtc_model(u_int model)
136 {
137 	/* no model given, assume it's a DS1307 (the first one) */
138 	if (model == 0)
139 		return &dsrtc_models[0];
140 
141 	for (const struct dsrtc_model *dm = dsrtc_models;
142 	     dm < dsrtc_models + __arraycount(dsrtc_models); dm++) {
143 		if (dm->dm_model == model)
144 			return dm;
145 	}
146 	return NULL;
147 }
148 
149 static int
150 dsrtc_match(device_t parent, cfdata_t cf, void *arg)
151 {
152 	struct i2c_attach_args *ia = arg;
153 
154 	if (ia->ia_name) {
155 		/* direct config - check name */
156 		if (strcmp(ia->ia_name, "dsrtc") == 0)
157 			return 1;
158 	} else {
159 		/* indirect config - check typical address */
160 		if (ia->ia_addr == DS1307_ADDR)
161 			return dsrtc_model(cf->cf_flags & 0xffff) != NULL;
162 	}
163 	return 0;
164 }
165 
166 static void
167 dsrtc_attach(device_t parent, device_t self, void *arg)
168 {
169 	struct dsrtc_softc *sc = device_private(self);
170 	struct i2c_attach_args *ia = arg;
171 	const struct dsrtc_model * const dm =
172 	    dsrtc_model(device_cfdata(self)->cf_flags);
173 
174 	aprint_naive(": Real-time Clock%s\n",
175 	    dm->dm_nvram_size > 0 ? "/NVRAM" : "");
176 	aprint_normal(": DS%u Real-time Clock%s\n", dm->dm_model,
177 	    dm->dm_nvram_size > 0 ? "/NVRAM" : "");
178 
179 	sc->sc_tag = ia->ia_tag;
180 	sc->sc_address = ia->ia_addr;
181 	sc->sc_model = *dm;
182 	sc->sc_dev = self;
183 	sc->sc_open = 0;
184 	sc->sc_todr.cookie = sc;
185 	if (dm->dm_flags & DSRTC_FLAG_BCD) {
186 		sc->sc_todr.todr_gettime_ymdhms = dsrtc_gettime_ymdhms;
187 		sc->sc_todr.todr_settime_ymdhms = dsrtc_settime_ymdhms;
188 	} else {
189 		sc->sc_todr.todr_gettime = dsrtc_gettime_timeval;
190 		sc->sc_todr.todr_settime = dsrtc_settime_timeval;
191 	}
192 	sc->sc_todr.todr_setwen = NULL;
193 
194 	todr_attach(&sc->sc_todr);
195 }
196 
197 /*ARGSUSED*/
198 int
199 dsrtc_open(dev_t dev, int flag, int fmt, struct lwp *l)
200 {
201 	struct dsrtc_softc *sc;
202 
203 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
204 		return ENXIO;
205 
206 	/* XXX: Locking */
207 	if (sc->sc_open)
208 		return EBUSY;
209 
210 	sc->sc_open = true;
211 	return 0;
212 }
213 
214 /*ARGSUSED*/
215 int
216 dsrtc_close(dev_t dev, int flag, int fmt, struct lwp *l)
217 {
218 	struct dsrtc_softc *sc;
219 
220 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
221 		return ENXIO;
222 
223 	sc->sc_open = false;
224 	return 0;
225 }
226 
227 /*ARGSUSED*/
228 int
229 dsrtc_read(dev_t dev, struct uio *uio, int flags)
230 {
231 	struct dsrtc_softc *sc;
232 	int error;
233 
234 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
235 		return ENXIO;
236 
237 	const struct dsrtc_model * const dm = &sc->sc_model;
238 	if (uio->uio_offset >= dm->dm_nvram_size)
239 		return EINVAL;
240 
241 	if ((error = iic_acquire_bus(sc->sc_tag, 0)) != 0)
242 		return error;
243 
244 	KASSERT(uio->uio_offset >= 0);
245 	while (uio->uio_resid && uio->uio_offset < dm->dm_nvram_size) {
246 		uint8_t ch, cmd;
247 		const u_int a = uio->uio_offset;
248 		cmd = a + dm->dm_nvram_start;
249 		if ((error = iic_exec(sc->sc_tag,
250 		    uio->uio_resid > 1 ? I2C_OP_READ : I2C_OP_READ_WITH_STOP,
251 		    sc->sc_address, &cmd, 1, &ch, 1, 0)) != 0) {
252 			iic_release_bus(sc->sc_tag, 0);
253 			aprint_error_dev(sc->sc_dev,
254 			    "%s: read failed at 0x%x: %d\n",
255 			    __func__, a, error);
256 			return error;
257 		}
258 		if ((error = uiomove(&ch, 1, uio)) != 0) {
259 			iic_release_bus(sc->sc_tag, 0);
260 			return error;
261 		}
262 	}
263 
264 	iic_release_bus(sc->sc_tag, 0);
265 
266 	return 0;
267 }
268 
269 /*ARGSUSED*/
270 int
271 dsrtc_write(dev_t dev, struct uio *uio, int flags)
272 {
273 	struct dsrtc_softc *sc;
274 	int error;
275 
276 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
277 		return ENXIO;
278 
279 	const struct dsrtc_model * const dm = &sc->sc_model;
280 	if (uio->uio_offset >= dm->dm_nvram_size)
281 		return EINVAL;
282 
283 	if ((error = iic_acquire_bus(sc->sc_tag, 0)) != 0)
284 		return error;
285 
286 	while (uio->uio_resid && uio->uio_offset < dm->dm_nvram_size) {
287 		uint8_t cmdbuf[2];
288 		const u_int a = (int)uio->uio_offset;
289 		cmdbuf[0] = a + dm->dm_nvram_start;
290 		if ((error = uiomove(&cmdbuf[1], 1, uio)) != 0)
291 			break;
292 
293 		if ((error = iic_exec(sc->sc_tag,
294 		    uio->uio_resid ? I2C_OP_WRITE : I2C_OP_WRITE_WITH_STOP,
295 		    sc->sc_address, cmdbuf, 1, &cmdbuf[1], 1, 0)) != 0) {
296 			aprint_error_dev(sc->sc_dev,
297 			    "%s: write failed at 0x%x: %d\n",
298 			    __func__, a, error);
299 			break;
300 		}
301 	}
302 
303 	iic_release_bus(sc->sc_tag, 0);
304 
305 	return error;
306 }
307 
308 static int
309 dsrtc_gettime_ymdhms(struct todr_chip_handle *ch, struct clock_ymdhms *dt)
310 {
311 	struct dsrtc_softc *sc = ch->cookie;
312 	struct clock_ymdhms check;
313 	int retries;
314 
315 	memset(dt, 0, sizeof(*dt));
316 	memset(&check, 0, sizeof(check));
317 
318 	/*
319 	 * Since we don't support Burst Read, we have to read the clock twice
320 	 * until we get two consecutive identical results.
321 	 */
322 	retries = 5;
323 	do {
324 		dsrtc_clock_read_ymdhms(sc, dt);
325 		dsrtc_clock_read_ymdhms(sc, &check);
326 	} while (memcmp(dt, &check, sizeof(check)) != 0 && --retries);
327 
328 	return 0;
329 }
330 
331 static int
332 dsrtc_settime_ymdhms(struct todr_chip_handle *ch, struct clock_ymdhms *dt)
333 {
334 	struct dsrtc_softc *sc = ch->cookie;
335 
336 	if (dsrtc_clock_write_ymdhms(sc, dt) == 0)
337 		return -1;
338 
339 	return 0;
340 }
341 
342 static int
343 dsrtc_clock_read_ymdhms(struct dsrtc_softc *sc, struct clock_ymdhms *dt)
344 {
345 	struct dsrtc_model * const dm = &sc->sc_model;
346 	uint8_t bcd[DSXXXX_RTC_SIZE], cmdbuf[1];
347 	int error;
348 
349 	KASSERT(DSXXXX_RTC_SIZE >= dm->dm_rtc_size);
350 
351 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
352 		aprint_error_dev(sc->sc_dev,
353 		    "%s: failed to acquire I2C bus: %d\n",
354 		    __func__, error);
355 		return 0;
356 	}
357 
358 	/* Read each RTC register in order. */
359 	for (u_int i = 0; !error && i < dm->dm_rtc_size; i++) {
360 		cmdbuf[0] = dm->dm_rtc_start + i;
361 
362 		error = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP,
363 		    sc->sc_address, cmdbuf, 1, &bcd[i], 1, I2C_F_POLL);
364 	}
365 
366 	/* Done with I2C */
367 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
368 
369 	if (error != 0) {
370 		aprint_error_dev(sc->sc_dev,
371 		    "%s: failed to read rtc at 0x%x: %d\n",
372 		    __func__, cmdbuf[0], error);
373 		return 0;
374 	}
375 
376 	/*
377 	 * Convert the RTC's register values into something useable
378 	 */
379 	dt->dt_sec = FROMBCD(bcd[DSXXXX_SECONDS] & DSXXXX_SECONDS_MASK);
380 	dt->dt_min = FROMBCD(bcd[DSXXXX_MINUTES] & DSXXXX_MINUTES_MASK);
381 
382 	if ((bcd[DSXXXX_HOURS] & DSXXXX_HOURS_12HRS_MODE) != 0) {
383 		dt->dt_hour = FROMBCD(bcd[DSXXXX_HOURS] &
384 		    DSXXXX_HOURS_12MASK) % 12; /* 12AM -> 0, 12PM -> 12 */
385 		if (bcd[DSXXXX_HOURS] & DSXXXX_HOURS_12HRS_PM)
386 			dt->dt_hour += 12;
387 	} else
388 		dt->dt_hour = FROMBCD(bcd[DSXXXX_HOURS] &
389 		    DSXXXX_HOURS_24MASK);
390 
391 	dt->dt_day = FROMBCD(bcd[DSXXXX_DATE] & DSXXXX_DATE_MASK);
392 	dt->dt_mon = FROMBCD(bcd[DSXXXX_MONTH] & DSXXXX_MONTH_MASK);
393 
394 	/* XXX: Should be an MD way to specify EPOCH used by BIOS/Firmware */
395 	dt->dt_year = FROMBCD(bcd[DSXXXX_YEAR]) + POSIX_BASE_YEAR;
396 	if (bcd[DSXXXX_MONTH] & DSXXXX_MONTH_CENTURY)
397 		dt->dt_year += 100;
398 
399 	return 1;
400 }
401 
402 static int
403 dsrtc_clock_write_ymdhms(struct dsrtc_softc *sc, struct clock_ymdhms *dt)
404 {
405 	struct dsrtc_model * const dm = &sc->sc_model;
406 	uint8_t bcd[DSXXXX_RTC_SIZE], cmdbuf[2];
407 	int error;
408 
409 	KASSERT(DSXXXX_RTC_SIZE >= dm->dm_rtc_size);
410 
411 	/*
412 	 * Convert our time representation into something the DSXXXX
413 	 * can understand.
414 	 */
415 	bcd[DSXXXX_SECONDS] = TOBCD(dt->dt_sec);
416 	bcd[DSXXXX_MINUTES] = TOBCD(dt->dt_min);
417 	bcd[DSXXXX_HOURS] = TOBCD(dt->dt_hour); /* DSXXXX_HOURS_12HRS_MODE=0 */
418 	bcd[DSXXXX_DATE] = TOBCD(dt->dt_day);
419 	bcd[DSXXXX_DAY] = TOBCD(dt->dt_wday);
420 	bcd[DSXXXX_MONTH] = TOBCD(dt->dt_mon);
421 	bcd[DSXXXX_YEAR] = TOBCD((dt->dt_year - POSIX_BASE_YEAR) % 100);
422 	if (dt->dt_year - POSIX_BASE_YEAR >= 100)
423 		bcd[DSXXXX_MONTH] |= DSXXXX_MONTH_CENTURY;
424 
425 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
426 		aprint_error_dev(sc->sc_dev,
427 		    "%s: failed to acquire I2C bus: %d\n",
428 		    __func__, error);
429 		return 0;
430 	}
431 
432 	/* Stop the clock */
433 	cmdbuf[0] = dm->dm_ch_reg;
434 
435 	if ((error = iic_exec(sc->sc_tag, I2C_OP_READ, sc->sc_address,
436 	    cmdbuf, 1, &cmdbuf[1], 1, I2C_F_POLL)) != 0) {
437 		iic_release_bus(sc->sc_tag, I2C_F_POLL);
438 		aprint_error_dev(sc->sc_dev,
439 		    "%s: failed to read Hold Clock: %d\n",
440 		    __func__, error);
441 		return 0;
442 	}
443 
444 	cmdbuf[1] |= dm->dm_ch_value;
445 
446 	if ((error = iic_exec(sc->sc_tag, I2C_OP_WRITE, sc->sc_address,
447 	    cmdbuf, 1, &cmdbuf[1], 1, I2C_F_POLL)) != 0) {
448 		iic_release_bus(sc->sc_tag, I2C_F_POLL);
449 		aprint_error_dev(sc->sc_dev,
450 		    "%s: failed to write Hold Clock: %d\n",
451 		    __func__, error);
452 		return 0;
453 	}
454 
455 	/*
456 	 * Write registers in reverse order. The last write (to the Seconds
457 	 * register) will undo the Clock Hold, above.
458 	 */
459 	uint8_t op = I2C_OP_WRITE;
460 	for (signed int i = dm->dm_rtc_size - 1; i >= 0; i--) {
461 		cmdbuf[0] = dm->dm_rtc_start + i;
462 		if (dm->dm_rtc_start + i == dm->dm_ch_reg) {
463 			op = I2C_OP_WRITE_WITH_STOP;
464 		}
465 		if ((error = iic_exec(sc->sc_tag, op, sc->sc_address,
466 		    cmdbuf, 1, &bcd[i], 1, I2C_F_POLL)) != 0) {
467 			iic_release_bus(sc->sc_tag, I2C_F_POLL);
468 			aprint_error_dev(sc->sc_dev,
469 			    "%s: failed to write rtc at 0x%x: %d\n",
470 			    __func__, i, error);
471 			/* XXX: Clock Hold is likely still asserted! */
472 			return 0;
473 		}
474 	}
475 	/*
476 	 * If the clock hold register isn't the same register as seconds,
477 	 * we need to reeanble the clock.
478 	 */
479 	if (op != I2C_OP_WRITE_WITH_STOP) {
480 		cmdbuf[0] = dm->dm_ch_reg;
481 		cmdbuf[1] &= ~dm->dm_ch_value;
482 
483 		if ((error = iic_exec(sc->sc_tag, I2C_OP_WRITE_WITH_STOP,
484 		    sc->sc_address, cmdbuf, 1, &cmdbuf[1], 1,
485 		    I2C_F_POLL)) != 0) {
486 			iic_release_bus(sc->sc_tag, I2C_F_POLL);
487 			aprint_error_dev(sc->sc_dev,
488 			    "%s: failed to Hold Clock: %d\n",
489 			    __func__, error);
490 			return 0;
491 		}
492 	}
493 
494 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
495 
496 	return 1;
497 }
498 
499 static int
500 dsrtc_gettime_timeval(struct todr_chip_handle *ch, struct timeval *tv)
501 {
502 	struct dsrtc_softc *sc = ch->cookie;
503 	struct timeval check;
504 	int retries;
505 
506 	memset(tv, 0, sizeof(*tv));
507 	memset(&check, 0, sizeof(check));
508 
509 	/*
510 	 * Since we don't support Burst Read, we have to read the clock twice
511 	 * until we get two consecutive identical results.
512 	 */
513 	retries = 5;
514 	do {
515 		dsrtc_clock_read_timeval(sc, &tv->tv_sec);
516 		dsrtc_clock_read_timeval(sc, &check.tv_sec);
517 	} while (memcmp(tv, &check, sizeof(check)) != 0 && --retries);
518 
519 	return 0;
520 }
521 
522 static int
523 dsrtc_settime_timeval(struct todr_chip_handle *ch, struct timeval *tv)
524 {
525 	struct dsrtc_softc *sc = ch->cookie;
526 
527 	if (dsrtc_clock_write_timeval(sc, tv->tv_sec) == 0)
528 		return -1;
529 
530 	return 0;
531 }
532 
533 /*
534  * The RTC probably has a nice Clock Burst Read/Write command, but we can't use
535  * it, since some I2C controllers don't support anything other than single-byte
536  * transfers.
537  */
538 static int
539 dsrtc_clock_read_timeval(struct dsrtc_softc *sc, time_t *tp)
540 {
541 	const struct dsrtc_model * const dm = &sc->sc_model;
542 	uint8_t buf[4];
543 	int error;
544 
545 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
546 		aprint_error_dev(sc->sc_dev,
547 		    "%s: failed to acquire I2C bus: %d\n",
548 		    __func__, error);
549 		return 0;
550 	}
551 
552 	/* read all registers: */
553 	uint8_t reg = dm->dm_rtc_start;
554 	error = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP, sc->sc_address,
555 	     &reg, 1, buf, 4, I2C_F_POLL);
556 
557 	/* Done with I2C */
558 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
559 
560 	if (error != 0) {
561 		aprint_error_dev(sc->sc_dev,
562 		    "%s: failed to read rtc at 0x%x: %d\n",
563 		    __func__, reg, error);
564 		return 0;
565 	}
566 
567 	uint32_t v = (buf[3] << 24) | (buf[2] << 16) | (buf[1] << 8) | buf[0];
568 	*tp = v;
569 
570 	aprint_debug_dev(sc->sc_dev, "%s: cntr=0x%08"PRIx32"\n",
571 	    __func__, v);
572 
573 	return 1;
574 }
575 
576 static int
577 dsrtc_clock_write_timeval(struct dsrtc_softc *sc, time_t t)
578 {
579 	const struct dsrtc_model * const dm = &sc->sc_model;
580 	size_t buflen = dm->dm_rtc_size + 2;
581 	uint8_t buf[buflen];
582 	int error;
583 
584 	KASSERT((dm->dm_flags & DSRTC_FLAG_CLOCK_HOLD) == 0);
585 	KASSERT(dm->dm_ch_reg == dm->dm_rtc_start + 4);
586 
587 	buf[0] = dm->dm_rtc_start;
588 	buf[1] = (t >> 0) & 0xff;
589 	buf[2] = (t >> 8) & 0xff;
590 	buf[3] = (t >> 16) & 0xff;
591 	buf[4] = (t >> 24) & 0xff;
592 	buf[5] = 0;
593 
594 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
595 		aprint_error_dev(sc->sc_dev,
596 		    "%s: failed to acquire I2C bus: %d\n",
597 		    __func__, error);
598 		return 0;
599 	}
600 
601 	error = iic_exec(sc->sc_tag, I2C_OP_WRITE_WITH_STOP, sc->sc_address,
602 	    &buf, buflen, NULL, 0, I2C_F_POLL);
603 
604 	/* Done with I2C */
605 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
606 
607 	/* send data */
608 	if (error != 0) {
609 		aprint_error_dev(sc->sc_dev,
610 		    "%s: failed to set time: %d\n",
611 		    __func__, error);
612 		return 0;
613 	}
614 
615 	return 1;
616 }
617