xref: /netbsd-src/sys/dev/i2c/ds1307.c (revision 80d9064ac03cbb6a4174695f0d5b237c8766d3d0)
1 /*	$NetBSD: ds1307.c,v 1.18 2014/07/25 08:10:37 dholland 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 1.18 2014/07/25 08:10:37 dholland 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 	.d_open = dsrtc_open,
121 	.d_close = dsrtc_close,
122 	.d_read = dsrtc_read,
123 	.d_write = dsrtc_write,
124 	.d_ioctl = noioctl,
125 	.d_stop = nostop,
126 	.d_tty = notty,
127 	.d_poll = nopoll,
128 	.d_mmap = nommap,
129 	.d_kqfilter = nokqfilter,
130 	.d_discard = nodiscard,
131 	.d_flag = D_OTHER
132 };
133 
134 static int dsrtc_gettime_ymdhms(struct todr_chip_handle *, struct clock_ymdhms *);
135 static int dsrtc_settime_ymdhms(struct todr_chip_handle *, struct clock_ymdhms *);
136 static int dsrtc_clock_read_ymdhms(struct dsrtc_softc *, struct clock_ymdhms *);
137 static int dsrtc_clock_write_ymdhms(struct dsrtc_softc *, struct clock_ymdhms *);
138 
139 static int dsrtc_gettime_timeval(struct todr_chip_handle *, struct timeval *);
140 static int dsrtc_settime_timeval(struct todr_chip_handle *, struct timeval *);
141 static int dsrtc_clock_read_timeval(struct dsrtc_softc *, time_t *);
142 static int dsrtc_clock_write_timeval(struct dsrtc_softc *, time_t);
143 
144 static const struct dsrtc_model *
145 dsrtc_model(u_int model)
146 {
147 	/* no model given, assume it's a DS1307 (the first one) */
148 	if (model == 0)
149 		return &dsrtc_models[0];
150 
151 	for (const struct dsrtc_model *dm = dsrtc_models;
152 	     dm < dsrtc_models + __arraycount(dsrtc_models); dm++) {
153 		if (dm->dm_model == model)
154 			return dm;
155 	}
156 	return NULL;
157 }
158 
159 static int
160 dsrtc_match(device_t parent, cfdata_t cf, void *arg)
161 {
162 	struct i2c_attach_args *ia = arg;
163 
164 	if (ia->ia_name) {
165 		/* direct config - check name */
166 		if (strcmp(ia->ia_name, "dsrtc") == 0)
167 			return 1;
168 	} else {
169 		/* indirect config - check typical address */
170 		if (ia->ia_addr == DS1307_ADDR)
171 			return dsrtc_model(cf->cf_flags & 0xffff) != NULL;
172 	}
173 	return 0;
174 }
175 
176 static void
177 dsrtc_attach(device_t parent, device_t self, void *arg)
178 {
179 	struct dsrtc_softc *sc = device_private(self);
180 	struct i2c_attach_args *ia = arg;
181 	const struct dsrtc_model * const dm =
182 	    dsrtc_model(device_cfdata(self)->cf_flags);
183 
184 	aprint_naive(": Real-time Clock%s\n",
185 	    dm->dm_nvram_size > 0 ? "/NVRAM" : "");
186 	aprint_normal(": DS%u Real-time Clock%s\n", dm->dm_model,
187 	    dm->dm_nvram_size > 0 ? "/NVRAM" : "");
188 
189 	sc->sc_tag = ia->ia_tag;
190 	sc->sc_address = ia->ia_addr;
191 	sc->sc_model = *dm;
192 	sc->sc_dev = self;
193 	sc->sc_open = 0;
194 	sc->sc_todr.cookie = sc;
195 	if (dm->dm_flags & DSRTC_FLAG_BCD) {
196 		sc->sc_todr.todr_gettime_ymdhms = dsrtc_gettime_ymdhms;
197 		sc->sc_todr.todr_settime_ymdhms = dsrtc_settime_ymdhms;
198 	} else {
199 		sc->sc_todr.todr_gettime = dsrtc_gettime_timeval;
200 		sc->sc_todr.todr_settime = dsrtc_settime_timeval;
201 	}
202 	sc->sc_todr.todr_setwen = NULL;
203 
204 	todr_attach(&sc->sc_todr);
205 }
206 
207 /*ARGSUSED*/
208 int
209 dsrtc_open(dev_t dev, int flag, int fmt, struct lwp *l)
210 {
211 	struct dsrtc_softc *sc;
212 
213 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
214 		return ENXIO;
215 
216 	/* XXX: Locking */
217 	if (sc->sc_open)
218 		return EBUSY;
219 
220 	sc->sc_open = true;
221 	return 0;
222 }
223 
224 /*ARGSUSED*/
225 int
226 dsrtc_close(dev_t dev, int flag, int fmt, struct lwp *l)
227 {
228 	struct dsrtc_softc *sc;
229 
230 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
231 		return ENXIO;
232 
233 	sc->sc_open = false;
234 	return 0;
235 }
236 
237 /*ARGSUSED*/
238 int
239 dsrtc_read(dev_t dev, struct uio *uio, int flags)
240 {
241 	struct dsrtc_softc *sc;
242 	int error;
243 
244 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
245 		return ENXIO;
246 
247 	const struct dsrtc_model * const dm = &sc->sc_model;
248 	if (uio->uio_offset >= dm->dm_nvram_size)
249 		return EINVAL;
250 
251 	if ((error = iic_acquire_bus(sc->sc_tag, 0)) != 0)
252 		return error;
253 
254 	KASSERT(uio->uio_offset >= 0);
255 	while (uio->uio_resid && uio->uio_offset < dm->dm_nvram_size) {
256 		uint8_t ch, cmd;
257 		const u_int a = uio->uio_offset;
258 		cmd = a + dm->dm_nvram_start;
259 		if ((error = iic_exec(sc->sc_tag,
260 		    uio->uio_resid > 1 ? I2C_OP_READ : I2C_OP_READ_WITH_STOP,
261 		    sc->sc_address, &cmd, 1, &ch, 1, 0)) != 0) {
262 			iic_release_bus(sc->sc_tag, 0);
263 			aprint_error_dev(sc->sc_dev,
264 			    "%s: read failed at 0x%x: %d\n",
265 			    __func__, a, error);
266 			return error;
267 		}
268 		if ((error = uiomove(&ch, 1, uio)) != 0) {
269 			iic_release_bus(sc->sc_tag, 0);
270 			return error;
271 		}
272 	}
273 
274 	iic_release_bus(sc->sc_tag, 0);
275 
276 	return 0;
277 }
278 
279 /*ARGSUSED*/
280 int
281 dsrtc_write(dev_t dev, struct uio *uio, int flags)
282 {
283 	struct dsrtc_softc *sc;
284 	int error;
285 
286 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
287 		return ENXIO;
288 
289 	const struct dsrtc_model * const dm = &sc->sc_model;
290 	if (uio->uio_offset >= dm->dm_nvram_size)
291 		return EINVAL;
292 
293 	if ((error = iic_acquire_bus(sc->sc_tag, 0)) != 0)
294 		return error;
295 
296 	while (uio->uio_resid && uio->uio_offset < dm->dm_nvram_size) {
297 		uint8_t cmdbuf[2];
298 		const u_int a = (int)uio->uio_offset;
299 		cmdbuf[0] = a + dm->dm_nvram_start;
300 		if ((error = uiomove(&cmdbuf[1], 1, uio)) != 0)
301 			break;
302 
303 		if ((error = iic_exec(sc->sc_tag,
304 		    uio->uio_resid ? I2C_OP_WRITE : I2C_OP_WRITE_WITH_STOP,
305 		    sc->sc_address, cmdbuf, 1, &cmdbuf[1], 1, 0)) != 0) {
306 			aprint_error_dev(sc->sc_dev,
307 			    "%s: write failed at 0x%x: %d\n",
308 			    __func__, a, error);
309 			break;
310 		}
311 	}
312 
313 	iic_release_bus(sc->sc_tag, 0);
314 
315 	return error;
316 }
317 
318 static int
319 dsrtc_gettime_ymdhms(struct todr_chip_handle *ch, struct clock_ymdhms *dt)
320 {
321 	struct dsrtc_softc *sc = ch->cookie;
322 	struct clock_ymdhms check;
323 	int retries;
324 
325 	memset(dt, 0, sizeof(*dt));
326 	memset(&check, 0, sizeof(check));
327 
328 	/*
329 	 * Since we don't support Burst Read, we have to read the clock twice
330 	 * until we get two consecutive identical results.
331 	 */
332 	retries = 5;
333 	do {
334 		dsrtc_clock_read_ymdhms(sc, dt);
335 		dsrtc_clock_read_ymdhms(sc, &check);
336 	} while (memcmp(dt, &check, sizeof(check)) != 0 && --retries);
337 
338 	return 0;
339 }
340 
341 static int
342 dsrtc_settime_ymdhms(struct todr_chip_handle *ch, struct clock_ymdhms *dt)
343 {
344 	struct dsrtc_softc *sc = ch->cookie;
345 
346 	if (dsrtc_clock_write_ymdhms(sc, dt) == 0)
347 		return -1;
348 
349 	return 0;
350 }
351 
352 static int
353 dsrtc_clock_read_ymdhms(struct dsrtc_softc *sc, struct clock_ymdhms *dt)
354 {
355 	struct dsrtc_model * const dm = &sc->sc_model;
356 	uint8_t bcd[DSXXXX_RTC_SIZE], cmdbuf[1];
357 	int error;
358 
359 	KASSERT(DSXXXX_RTC_SIZE >= dm->dm_rtc_size);
360 
361 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
362 		aprint_error_dev(sc->sc_dev,
363 		    "%s: failed to acquire I2C bus: %d\n",
364 		    __func__, error);
365 		return 0;
366 	}
367 
368 	/* Read each RTC register in order. */
369 	for (u_int i = 0; !error && i < dm->dm_rtc_size; i++) {
370 		cmdbuf[0] = dm->dm_rtc_start + i;
371 
372 		error = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP,
373 		    sc->sc_address, cmdbuf, 1, &bcd[i], 1, I2C_F_POLL);
374 	}
375 
376 	/* Done with I2C */
377 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
378 
379 	if (error != 0) {
380 		aprint_error_dev(sc->sc_dev,
381 		    "%s: failed to read rtc at 0x%x: %d\n",
382 		    __func__, cmdbuf[0], error);
383 		return 0;
384 	}
385 
386 	/*
387 	 * Convert the RTC's register values into something useable
388 	 */
389 	dt->dt_sec = FROMBCD(bcd[DSXXXX_SECONDS] & DSXXXX_SECONDS_MASK);
390 	dt->dt_min = FROMBCD(bcd[DSXXXX_MINUTES] & DSXXXX_MINUTES_MASK);
391 
392 	if ((bcd[DSXXXX_HOURS] & DSXXXX_HOURS_12HRS_MODE) != 0) {
393 		dt->dt_hour = FROMBCD(bcd[DSXXXX_HOURS] &
394 		    DSXXXX_HOURS_12MASK) % 12; /* 12AM -> 0, 12PM -> 12 */
395 		if (bcd[DSXXXX_HOURS] & DSXXXX_HOURS_12HRS_PM)
396 			dt->dt_hour += 12;
397 	} else
398 		dt->dt_hour = FROMBCD(bcd[DSXXXX_HOURS] &
399 		    DSXXXX_HOURS_24MASK);
400 
401 	dt->dt_day = FROMBCD(bcd[DSXXXX_DATE] & DSXXXX_DATE_MASK);
402 	dt->dt_mon = FROMBCD(bcd[DSXXXX_MONTH] & DSXXXX_MONTH_MASK);
403 
404 	/* XXX: Should be an MD way to specify EPOCH used by BIOS/Firmware */
405 	dt->dt_year = FROMBCD(bcd[DSXXXX_YEAR]) + POSIX_BASE_YEAR;
406 	if (bcd[DSXXXX_MONTH] & DSXXXX_MONTH_CENTURY)
407 		dt->dt_year += 100;
408 
409 	return 1;
410 }
411 
412 static int
413 dsrtc_clock_write_ymdhms(struct dsrtc_softc *sc, struct clock_ymdhms *dt)
414 {
415 	struct dsrtc_model * const dm = &sc->sc_model;
416 	uint8_t bcd[DSXXXX_RTC_SIZE], cmdbuf[2];
417 	int error;
418 
419 	KASSERT(DSXXXX_RTC_SIZE >= dm->dm_rtc_size);
420 
421 	/*
422 	 * Convert our time representation into something the DSXXXX
423 	 * can understand.
424 	 */
425 	bcd[DSXXXX_SECONDS] = TOBCD(dt->dt_sec);
426 	bcd[DSXXXX_MINUTES] = TOBCD(dt->dt_min);
427 	bcd[DSXXXX_HOURS] = TOBCD(dt->dt_hour); /* DSXXXX_HOURS_12HRS_MODE=0 */
428 	bcd[DSXXXX_DATE] = TOBCD(dt->dt_day);
429 	bcd[DSXXXX_DAY] = TOBCD(dt->dt_wday);
430 	bcd[DSXXXX_MONTH] = TOBCD(dt->dt_mon);
431 	bcd[DSXXXX_YEAR] = TOBCD((dt->dt_year - POSIX_BASE_YEAR) % 100);
432 	if (dt->dt_year - POSIX_BASE_YEAR >= 100)
433 		bcd[DSXXXX_MONTH] |= DSXXXX_MONTH_CENTURY;
434 
435 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
436 		aprint_error_dev(sc->sc_dev,
437 		    "%s: failed to acquire I2C bus: %d\n",
438 		    __func__, error);
439 		return 0;
440 	}
441 
442 	/* Stop the clock */
443 	cmdbuf[0] = dm->dm_ch_reg;
444 
445 	if ((error = iic_exec(sc->sc_tag, I2C_OP_READ, sc->sc_address,
446 	    cmdbuf, 1, &cmdbuf[1], 1, I2C_F_POLL)) != 0) {
447 		iic_release_bus(sc->sc_tag, I2C_F_POLL);
448 		aprint_error_dev(sc->sc_dev,
449 		    "%s: failed to read Hold Clock: %d\n",
450 		    __func__, error);
451 		return 0;
452 	}
453 
454 	cmdbuf[1] |= dm->dm_ch_value;
455 
456 	if ((error = iic_exec(sc->sc_tag, I2C_OP_WRITE, sc->sc_address,
457 	    cmdbuf, 1, &cmdbuf[1], 1, I2C_F_POLL)) != 0) {
458 		iic_release_bus(sc->sc_tag, I2C_F_POLL);
459 		aprint_error_dev(sc->sc_dev,
460 		    "%s: failed to write Hold Clock: %d\n",
461 		    __func__, error);
462 		return 0;
463 	}
464 
465 	/*
466 	 * Write registers in reverse order. The last write (to the Seconds
467 	 * register) will undo the Clock Hold, above.
468 	 */
469 	uint8_t op = I2C_OP_WRITE;
470 	for (signed int i = dm->dm_rtc_size - 1; i >= 0; i--) {
471 		cmdbuf[0] = dm->dm_rtc_start + i;
472 		if (dm->dm_rtc_start + i == dm->dm_ch_reg) {
473 			op = I2C_OP_WRITE_WITH_STOP;
474 		}
475 		if ((error = iic_exec(sc->sc_tag, op, sc->sc_address,
476 		    cmdbuf, 1, &bcd[i], 1, I2C_F_POLL)) != 0) {
477 			iic_release_bus(sc->sc_tag, I2C_F_POLL);
478 			aprint_error_dev(sc->sc_dev,
479 			    "%s: failed to write rtc at 0x%x: %d\n",
480 			    __func__, i, error);
481 			/* XXX: Clock Hold is likely still asserted! */
482 			return 0;
483 		}
484 	}
485 	/*
486 	 * If the clock hold register isn't the same register as seconds,
487 	 * we need to reeanble the clock.
488 	 */
489 	if (op != I2C_OP_WRITE_WITH_STOP) {
490 		cmdbuf[0] = dm->dm_ch_reg;
491 		cmdbuf[1] &= ~dm->dm_ch_value;
492 
493 		if ((error = iic_exec(sc->sc_tag, I2C_OP_WRITE_WITH_STOP,
494 		    sc->sc_address, cmdbuf, 1, &cmdbuf[1], 1,
495 		    I2C_F_POLL)) != 0) {
496 			iic_release_bus(sc->sc_tag, I2C_F_POLL);
497 			aprint_error_dev(sc->sc_dev,
498 			    "%s: failed to Hold Clock: %d\n",
499 			    __func__, error);
500 			return 0;
501 		}
502 	}
503 
504 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
505 
506 	return 1;
507 }
508 
509 static int
510 dsrtc_gettime_timeval(struct todr_chip_handle *ch, struct timeval *tv)
511 {
512 	struct dsrtc_softc *sc = ch->cookie;
513 	struct timeval check;
514 	int retries;
515 
516 	memset(tv, 0, sizeof(*tv));
517 	memset(&check, 0, sizeof(check));
518 
519 	/*
520 	 * Since we don't support Burst Read, we have to read the clock twice
521 	 * until we get two consecutive identical results.
522 	 */
523 	retries = 5;
524 	do {
525 		dsrtc_clock_read_timeval(sc, &tv->tv_sec);
526 		dsrtc_clock_read_timeval(sc, &check.tv_sec);
527 	} while (memcmp(tv, &check, sizeof(check)) != 0 && --retries);
528 
529 	return 0;
530 }
531 
532 static int
533 dsrtc_settime_timeval(struct todr_chip_handle *ch, struct timeval *tv)
534 {
535 	struct dsrtc_softc *sc = ch->cookie;
536 
537 	if (dsrtc_clock_write_timeval(sc, tv->tv_sec) == 0)
538 		return -1;
539 
540 	return 0;
541 }
542 
543 /*
544  * The RTC probably has a nice Clock Burst Read/Write command, but we can't use
545  * it, since some I2C controllers don't support anything other than single-byte
546  * transfers.
547  */
548 static int
549 dsrtc_clock_read_timeval(struct dsrtc_softc *sc, time_t *tp)
550 {
551 	const struct dsrtc_model * const dm = &sc->sc_model;
552 	uint8_t buf[4];
553 	int error;
554 
555 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
556 		aprint_error_dev(sc->sc_dev,
557 		    "%s: failed to acquire I2C bus: %d\n",
558 		    __func__, error);
559 		return 0;
560 	}
561 
562 	/* read all registers: */
563 	uint8_t reg = dm->dm_rtc_start;
564 	error = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP, sc->sc_address,
565 	     &reg, 1, buf, 4, I2C_F_POLL);
566 
567 	/* Done with I2C */
568 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
569 
570 	if (error != 0) {
571 		aprint_error_dev(sc->sc_dev,
572 		    "%s: failed to read rtc at 0x%x: %d\n",
573 		    __func__, reg, error);
574 		return 0;
575 	}
576 
577 	uint32_t v = (buf[3] << 24) | (buf[2] << 16) | (buf[1] << 8) | buf[0];
578 	*tp = v;
579 
580 	aprint_debug_dev(sc->sc_dev, "%s: cntr=0x%08"PRIx32"\n",
581 	    __func__, v);
582 
583 	return 1;
584 }
585 
586 static int
587 dsrtc_clock_write_timeval(struct dsrtc_softc *sc, time_t t)
588 {
589 	const struct dsrtc_model * const dm = &sc->sc_model;
590 	size_t buflen = dm->dm_rtc_size + 2;
591 	uint8_t buf[buflen];
592 	int error;
593 
594 	KASSERT((dm->dm_flags & DSRTC_FLAG_CLOCK_HOLD) == 0);
595 	KASSERT(dm->dm_ch_reg == dm->dm_rtc_start + 4);
596 
597 	buf[0] = dm->dm_rtc_start;
598 	buf[1] = (t >> 0) & 0xff;
599 	buf[2] = (t >> 8) & 0xff;
600 	buf[3] = (t >> 16) & 0xff;
601 	buf[4] = (t >> 24) & 0xff;
602 	buf[5] = 0;
603 
604 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
605 		aprint_error_dev(sc->sc_dev,
606 		    "%s: failed to acquire I2C bus: %d\n",
607 		    __func__, error);
608 		return 0;
609 	}
610 
611 	error = iic_exec(sc->sc_tag, I2C_OP_WRITE_WITH_STOP, sc->sc_address,
612 	    &buf, buflen, NULL, 0, I2C_F_POLL);
613 
614 	/* Done with I2C */
615 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
616 
617 	/* send data */
618 	if (error != 0) {
619 		aprint_error_dev(sc->sc_dev,
620 		    "%s: failed to set time: %d\n",
621 		    __func__, error);
622 		return 0;
623 	}
624 
625 	return 1;
626 }
627