xref: /netbsd-src/sys/dev/i2c/ds1307.c (revision 796c32c94f6e154afc9de0f63da35c91bb739b45)
1 /*	$NetBSD: ds1307.c,v 1.25 2017/10/28 04:53:55 riastradh 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 1.25 2017/10/28 04:53:55 riastradh 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 #include <dev/sysmon/sysmonvar.h>
55 
56 #include "ioconf.h"
57 
58 struct dsrtc_model {
59 	uint16_t dm_model;
60 	uint8_t dm_ch_reg;
61 	uint8_t dm_ch_value;
62 	uint8_t dm_vbaten_reg;
63 	uint8_t dm_vbaten_value;
64 	uint8_t dm_rtc_start;
65 	uint8_t dm_rtc_size;
66 	uint8_t dm_nvram_start;
67 	uint8_t dm_nvram_size;
68 	uint8_t dm_flags;
69 #define	DSRTC_FLAG_CLOCK_HOLD		0x01
70 #define	DSRTC_FLAG_BCD			0x02
71 #define	DSRTC_FLAG_TEMP			0x04
72 #define DSRTC_FLAG_VBATEN		0x08
73 #define	DSRTC_FLAG_YEAR_START_2K	0x10
74 #define	DSRTC_FLAG_CLOCK_HOLD_REVERSED	0x20
75 };
76 
77 static const struct dsrtc_model dsrtc_models[] = {
78 	{
79 		.dm_model = 1307,
80 		.dm_ch_reg = DSXXXX_SECONDS,
81 		.dm_ch_value = DS1307_SECONDS_CH,
82 		.dm_rtc_start = DS1307_RTC_START,
83 		.dm_rtc_size = DS1307_RTC_SIZE,
84 		.dm_nvram_start = DS1307_NVRAM_START,
85 		.dm_nvram_size = DS1307_NVRAM_SIZE,
86 		.dm_flags = DSRTC_FLAG_BCD | DSRTC_FLAG_CLOCK_HOLD,
87 	}, {
88 		.dm_model = 1339,
89 		.dm_rtc_start = DS1339_RTC_START,
90 		.dm_rtc_size = DS1339_RTC_SIZE,
91 		.dm_flags = DSRTC_FLAG_BCD,
92 	}, {
93 		.dm_model = 1340,
94 		.dm_ch_reg = DSXXXX_SECONDS,
95 		.dm_ch_value = DS1340_SECONDS_EOSC,
96 		.dm_rtc_start = DS1340_RTC_START,
97 		.dm_rtc_size = DS1340_RTC_SIZE,
98 		.dm_flags = DSRTC_FLAG_BCD,
99 	}, {
100 		.dm_model = 1672,
101 		.dm_rtc_start = DS1672_RTC_START,
102 		.dm_rtc_size = DS1672_RTC_SIZE,
103 		.dm_ch_reg = DS1672_CONTROL,
104 		.dm_ch_value = DS1672_CONTROL_CH,
105 		.dm_flags = 0,
106 	}, {
107 		.dm_model = 3231,
108 		.dm_rtc_start = DS3232_RTC_START,
109 		.dm_rtc_size = DS3232_RTC_SIZE,
110 		/*
111 		 * XXX
112 		 * the DS3232 likely has the temperature sensor too but I can't
113 		 * easily verify or test that right now
114 		 */
115 		.dm_flags = DSRTC_FLAG_BCD | DSRTC_FLAG_TEMP,
116 	}, {
117 		.dm_model = 3232,
118 		.dm_rtc_start = DS3232_RTC_START,
119 		.dm_rtc_size = DS3232_RTC_SIZE,
120 		.dm_nvram_start = DS3232_NVRAM_START,
121 		.dm_nvram_size = DS3232_NVRAM_SIZE,
122 		.dm_flags = DSRTC_FLAG_BCD,
123 	}, {
124 		/* MCP7940 */
125 		.dm_model = 7940,
126 		.dm_rtc_start = DS1307_RTC_START,
127 		.dm_rtc_size = DS1307_RTC_SIZE,
128 		.dm_ch_reg = DSXXXX_SECONDS,
129 		.dm_ch_value = DS1307_SECONDS_CH,
130 		.dm_vbaten_reg = DSXXXX_DAY,
131 		.dm_vbaten_value = MCP7940_TOD_DAY_VBATEN,
132 		.dm_nvram_start = MCP7940_NVRAM_START,
133 		.dm_nvram_size = MCP7940_NVRAM_SIZE,
134 		.dm_flags = DSRTC_FLAG_BCD | DSRTC_FLAG_CLOCK_HOLD |
135 			DSRTC_FLAG_VBATEN | DSRTC_FLAG_CLOCK_HOLD_REVERSED,
136 	},
137 };
138 
139 struct dsrtc_softc {
140 	device_t sc_dev;
141 	i2c_tag_t sc_tag;
142 	uint8_t sc_address;
143 	bool sc_open;
144 	struct dsrtc_model sc_model;
145 	struct todr_chip_handle sc_todr;
146 	struct sysmon_envsys *sc_sme;
147 	envsys_data_t sc_sensor;
148 };
149 
150 static void	dsrtc_attach(device_t, device_t, void *);
151 static int	dsrtc_match(device_t, cfdata_t, void *);
152 
153 CFATTACH_DECL_NEW(dsrtc, sizeof(struct dsrtc_softc),
154     dsrtc_match, dsrtc_attach, NULL, NULL);
155 
156 dev_type_open(dsrtc_open);
157 dev_type_close(dsrtc_close);
158 dev_type_read(dsrtc_read);
159 dev_type_write(dsrtc_write);
160 
161 const struct cdevsw dsrtc_cdevsw = {
162 	.d_open = dsrtc_open,
163 	.d_close = dsrtc_close,
164 	.d_read = dsrtc_read,
165 	.d_write = dsrtc_write,
166 	.d_ioctl = noioctl,
167 	.d_stop = nostop,
168 	.d_tty = notty,
169 	.d_poll = nopoll,
170 	.d_mmap = nommap,
171 	.d_kqfilter = nokqfilter,
172 	.d_discard = nodiscard,
173 	.d_flag = D_OTHER
174 };
175 
176 static int dsrtc_gettime_ymdhms(struct todr_chip_handle *, struct clock_ymdhms *);
177 static int dsrtc_settime_ymdhms(struct todr_chip_handle *, struct clock_ymdhms *);
178 static int dsrtc_clock_read_ymdhms(struct dsrtc_softc *, struct clock_ymdhms *);
179 static int dsrtc_clock_write_ymdhms(struct dsrtc_softc *, struct clock_ymdhms *);
180 
181 static int dsrtc_gettime_timeval(struct todr_chip_handle *, struct timeval *);
182 static int dsrtc_settime_timeval(struct todr_chip_handle *, struct timeval *);
183 static int dsrtc_clock_read_timeval(struct dsrtc_softc *, time_t *);
184 static int dsrtc_clock_write_timeval(struct dsrtc_softc *, time_t);
185 
186 static int dsrtc_read_temp(struct dsrtc_softc *, uint32_t *);
187 static void dsrtc_refresh(struct sysmon_envsys *, envsys_data_t *);
188 
189 static const struct dsrtc_model *
190 dsrtc_model(u_int model)
191 {
192 	/* no model given, assume it's a DS1307 (the first one) */
193 	if (model == 0)
194 		return &dsrtc_models[0];
195 
196 	for (const struct dsrtc_model *dm = dsrtc_models;
197 	     dm < dsrtc_models + __arraycount(dsrtc_models); dm++) {
198 		if (dm->dm_model == model)
199 			return dm;
200 	}
201 	return NULL;
202 }
203 
204 static int
205 dsrtc_match(device_t parent, cfdata_t cf, void *arg)
206 {
207 	struct i2c_attach_args *ia = arg;
208 
209 	if (ia->ia_name) {
210 		/* direct config - check name */
211 		if (strcmp(ia->ia_name, "dsrtc") == 0)
212 			return 1;
213 	} else {
214 		/* indirect config - check typical address */
215 		if (ia->ia_addr == DS1307_ADDR || ia->ia_addr == MCP7940_ADDR)
216 			return dsrtc_model(cf->cf_flags & 0xffff) != NULL;
217 	}
218 	return 0;
219 }
220 
221 static void
222 dsrtc_attach(device_t parent, device_t self, void *arg)
223 {
224 	struct dsrtc_softc *sc = device_private(self);
225 	struct i2c_attach_args *ia = arg;
226 	const struct dsrtc_model * const dm =
227 	    dsrtc_model(device_cfdata(self)->cf_flags);
228 
229 	aprint_naive(": Real-time Clock%s\n",
230 	    dm->dm_nvram_size > 0 ? "/NVRAM" : "");
231 	aprint_normal(": DS%u Real-time Clock%s\n", dm->dm_model,
232 	    dm->dm_nvram_size > 0 ? "/NVRAM" : "");
233 
234 	sc->sc_tag = ia->ia_tag;
235 	sc->sc_address = ia->ia_addr;
236 	sc->sc_model = *dm;
237 	sc->sc_dev = self;
238 	sc->sc_open = 0;
239 	sc->sc_todr.cookie = sc;
240 	if (dm->dm_flags & DSRTC_FLAG_BCD) {
241 		sc->sc_todr.todr_gettime_ymdhms = dsrtc_gettime_ymdhms;
242 		sc->sc_todr.todr_settime_ymdhms = dsrtc_settime_ymdhms;
243 	} else {
244 		sc->sc_todr.todr_gettime = dsrtc_gettime_timeval;
245 		sc->sc_todr.todr_settime = dsrtc_settime_timeval;
246 	}
247 	sc->sc_todr.todr_setwen = NULL;
248 
249 	todr_attach(&sc->sc_todr);
250 	if ((sc->sc_model.dm_flags & DSRTC_FLAG_TEMP) != 0) {
251 		int error;
252 
253 		sc->sc_sme = sysmon_envsys_create();
254 		sc->sc_sme->sme_name = device_xname(self);
255 		sc->sc_sme->sme_cookie = sc;
256 		sc->sc_sme->sme_refresh = dsrtc_refresh;
257 
258 		sc->sc_sensor.units =  ENVSYS_STEMP;
259 		sc->sc_sensor.state = ENVSYS_SINVALID;
260 		sc->sc_sensor.flags = 0;
261 		(void)strlcpy(sc->sc_sensor.desc, "temperature",
262 		    sizeof(sc->sc_sensor.desc));
263 
264 		if (sysmon_envsys_sensor_attach(sc->sc_sme, &sc->sc_sensor)) {
265 			aprint_error_dev(self, "unable to attach sensor\n");
266 			goto bad;
267 		}
268 
269 		error = sysmon_envsys_register(sc->sc_sme);
270 		if (error) {
271 			aprint_error_dev(self,
272 			    "error %d registering with sysmon\n", error);
273 			goto bad;
274 		}
275 	}
276 	return;
277 bad:
278 	sysmon_envsys_destroy(sc->sc_sme);
279 }
280 
281 /*ARGSUSED*/
282 int
283 dsrtc_open(dev_t dev, int flag, int fmt, struct lwp *l)
284 {
285 	struct dsrtc_softc *sc;
286 
287 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
288 		return ENXIO;
289 
290 	/* XXX: Locking */
291 	if (sc->sc_open)
292 		return EBUSY;
293 
294 	sc->sc_open = true;
295 	return 0;
296 }
297 
298 /*ARGSUSED*/
299 int
300 dsrtc_close(dev_t dev, int flag, int fmt, struct lwp *l)
301 {
302 	struct dsrtc_softc *sc;
303 
304 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
305 		return ENXIO;
306 
307 	sc->sc_open = false;
308 	return 0;
309 }
310 
311 /*ARGSUSED*/
312 int
313 dsrtc_read(dev_t dev, struct uio *uio, int flags)
314 {
315 	struct dsrtc_softc *sc;
316 	int error;
317 
318 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
319 		return ENXIO;
320 
321 	const struct dsrtc_model * const dm = &sc->sc_model;
322 	if (uio->uio_offset >= dm->dm_nvram_size)
323 		return EINVAL;
324 
325 	if ((error = iic_acquire_bus(sc->sc_tag, 0)) != 0)
326 		return error;
327 
328 	KASSERT(uio->uio_offset >= 0);
329 	while (uio->uio_resid && uio->uio_offset < dm->dm_nvram_size) {
330 		uint8_t ch, cmd;
331 		const u_int a = uio->uio_offset;
332 		cmd = a + dm->dm_nvram_start;
333 		if ((error = iic_exec(sc->sc_tag,
334 		    uio->uio_resid > 1 ? I2C_OP_READ : I2C_OP_READ_WITH_STOP,
335 		    sc->sc_address, &cmd, 1, &ch, 1, 0)) != 0) {
336 			iic_release_bus(sc->sc_tag, 0);
337 			aprint_error_dev(sc->sc_dev,
338 			    "%s: read failed at 0x%x: %d\n",
339 			    __func__, a, error);
340 			return error;
341 		}
342 		if ((error = uiomove(&ch, 1, uio)) != 0) {
343 			iic_release_bus(sc->sc_tag, 0);
344 			return error;
345 		}
346 	}
347 
348 	iic_release_bus(sc->sc_tag, 0);
349 
350 	return 0;
351 }
352 
353 /*ARGSUSED*/
354 int
355 dsrtc_write(dev_t dev, struct uio *uio, int flags)
356 {
357 	struct dsrtc_softc *sc;
358 	int error;
359 
360 	if ((sc = device_lookup_private(&dsrtc_cd, minor(dev))) == NULL)
361 		return ENXIO;
362 
363 	const struct dsrtc_model * const dm = &sc->sc_model;
364 	if (uio->uio_offset >= dm->dm_nvram_size)
365 		return EINVAL;
366 
367 	if ((error = iic_acquire_bus(sc->sc_tag, 0)) != 0)
368 		return error;
369 
370 	while (uio->uio_resid && uio->uio_offset < dm->dm_nvram_size) {
371 		uint8_t cmdbuf[2];
372 		const u_int a = (int)uio->uio_offset;
373 		cmdbuf[0] = a + dm->dm_nvram_start;
374 		if ((error = uiomove(&cmdbuf[1], 1, uio)) != 0)
375 			break;
376 
377 		if ((error = iic_exec(sc->sc_tag,
378 		    uio->uio_resid ? I2C_OP_WRITE : I2C_OP_WRITE_WITH_STOP,
379 		    sc->sc_address, cmdbuf, 1, &cmdbuf[1], 1, 0)) != 0) {
380 			aprint_error_dev(sc->sc_dev,
381 			    "%s: write failed at 0x%x: %d\n",
382 			    __func__, a, error);
383 			break;
384 		}
385 	}
386 
387 	iic_release_bus(sc->sc_tag, 0);
388 
389 	return error;
390 }
391 
392 static int
393 dsrtc_gettime_ymdhms(struct todr_chip_handle *ch, struct clock_ymdhms *dt)
394 {
395 	struct dsrtc_softc *sc = ch->cookie;
396 	struct clock_ymdhms check;
397 	int retries;
398 
399 	memset(dt, 0, sizeof(*dt));
400 	memset(&check, 0, sizeof(check));
401 
402 	/*
403 	 * Since we don't support Burst Read, we have to read the clock twice
404 	 * until we get two consecutive identical results.
405 	 */
406 	retries = 5;
407 	do {
408 		dsrtc_clock_read_ymdhms(sc, dt);
409 		dsrtc_clock_read_ymdhms(sc, &check);
410 	} while (memcmp(dt, &check, sizeof(check)) != 0 && --retries);
411 
412 	return 0;
413 }
414 
415 static int
416 dsrtc_settime_ymdhms(struct todr_chip_handle *ch, struct clock_ymdhms *dt)
417 {
418 	struct dsrtc_softc *sc = ch->cookie;
419 
420 	if (dsrtc_clock_write_ymdhms(sc, dt) == 0)
421 		return -1;
422 
423 	return 0;
424 }
425 
426 static int
427 dsrtc_clock_read_ymdhms(struct dsrtc_softc *sc, struct clock_ymdhms *dt)
428 {
429 	struct dsrtc_model * const dm = &sc->sc_model;
430 	uint8_t bcd[DSXXXX_RTC_SIZE], cmdbuf[1];
431 	int error;
432 
433 	KASSERT(DSXXXX_RTC_SIZE >= dm->dm_rtc_size);
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 	/* Read each RTC register in order. */
443 	for (u_int i = 0; !error && i < dm->dm_rtc_size; i++) {
444 		cmdbuf[0] = dm->dm_rtc_start + i;
445 
446 		error = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP,
447 		    sc->sc_address, cmdbuf, 1, &bcd[i], 1, I2C_F_POLL);
448 	}
449 
450 	/* Done with I2C */
451 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
452 
453 	if (error != 0) {
454 		aprint_error_dev(sc->sc_dev,
455 		    "%s: failed to read rtc at 0x%x: %d\n",
456 		    __func__, cmdbuf[0], error);
457 		return 0;
458 	}
459 
460 	/*
461 	 * Convert the RTC's register values into something useable
462 	 */
463 	dt->dt_sec = bcdtobin(bcd[DSXXXX_SECONDS] & DSXXXX_SECONDS_MASK);
464 	dt->dt_min = bcdtobin(bcd[DSXXXX_MINUTES] & DSXXXX_MINUTES_MASK);
465 
466 	if ((bcd[DSXXXX_HOURS] & DSXXXX_HOURS_12HRS_MODE) != 0) {
467 		dt->dt_hour = bcdtobin(bcd[DSXXXX_HOURS] &
468 		    DSXXXX_HOURS_12MASK) % 12; /* 12AM -> 0, 12PM -> 12 */
469 		if (bcd[DSXXXX_HOURS] & DSXXXX_HOURS_12HRS_PM)
470 			dt->dt_hour += 12;
471 	} else
472 		dt->dt_hour = bcdtobin(bcd[DSXXXX_HOURS] &
473 		    DSXXXX_HOURS_24MASK);
474 
475 	dt->dt_day = bcdtobin(bcd[DSXXXX_DATE] & DSXXXX_DATE_MASK);
476 	dt->dt_mon = bcdtobin(bcd[DSXXXX_MONTH] & DSXXXX_MONTH_MASK);
477 
478 	/* XXX: Should be an MD way to specify EPOCH used by BIOS/Firmware */
479 	if (sc->sc_model.dm_flags & DSRTC_FLAG_YEAR_START_2K)
480 		dt->dt_year = bcdtobin(bcd[DSXXXX_YEAR]) + 2000;
481 	else {
482 		dt->dt_year = bcdtobin(bcd[DSXXXX_YEAR]) + POSIX_BASE_YEAR;
483 		if (bcd[DSXXXX_MONTH] & DSXXXX_MONTH_CENTURY)
484 			dt->dt_year += 100;
485 	}
486 
487 	return 1;
488 }
489 
490 static int
491 dsrtc_clock_write_ymdhms(struct dsrtc_softc *sc, struct clock_ymdhms *dt)
492 {
493 	struct dsrtc_model * const dm = &sc->sc_model;
494 	uint8_t bcd[DSXXXX_RTC_SIZE], cmdbuf[2];
495 	int error;
496 
497 	KASSERT(DSXXXX_RTC_SIZE >= dm->dm_rtc_size);
498 
499 	/*
500 	 * Convert our time representation into something the DSXXXX
501 	 * can understand.
502 	 */
503 	bcd[DSXXXX_SECONDS] = bintobcd(dt->dt_sec);
504 	bcd[DSXXXX_MINUTES] = bintobcd(dt->dt_min);
505 	bcd[DSXXXX_HOURS] = bintobcd(dt->dt_hour); /* DSXXXX_HOURS_12HRS_MODE=0 */
506 	bcd[DSXXXX_DATE] = bintobcd(dt->dt_day);
507 	bcd[DSXXXX_DAY] = bintobcd(dt->dt_wday);
508 	bcd[DSXXXX_MONTH] = bintobcd(dt->dt_mon);
509 	bcd[DSXXXX_YEAR] = bintobcd((dt->dt_year - POSIX_BASE_YEAR) % 100);
510 	if (dt->dt_year - POSIX_BASE_YEAR >= 100)
511 		bcd[DSXXXX_MONTH] |= DSXXXX_MONTH_CENTURY;
512 
513 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
514 		aprint_error_dev(sc->sc_dev,
515 		    "%s: failed to acquire I2C bus: %d\n",
516 		    __func__, error);
517 		return 0;
518 	}
519 
520 	/* Stop the clock */
521 	cmdbuf[0] = dm->dm_ch_reg;
522 
523 	if ((error = iic_exec(sc->sc_tag, I2C_OP_READ, sc->sc_address,
524 	    cmdbuf, 1, &cmdbuf[1], 1, I2C_F_POLL)) != 0) {
525 		iic_release_bus(sc->sc_tag, I2C_F_POLL);
526 		aprint_error_dev(sc->sc_dev,
527 		    "%s: failed to read Hold Clock: %d\n",
528 		    __func__, error);
529 		return 0;
530 	}
531 
532 	if (sc->sc_model.dm_flags & DSRTC_FLAG_CLOCK_HOLD_REVERSED)
533 		cmdbuf[1] &= ~dm->dm_ch_value;
534 	else
535 		cmdbuf[1] |= dm->dm_ch_value;
536 
537 	if ((error = iic_exec(sc->sc_tag, I2C_OP_WRITE, sc->sc_address,
538 	    cmdbuf, 1, &cmdbuf[1], 1, I2C_F_POLL)) != 0) {
539 		iic_release_bus(sc->sc_tag, I2C_F_POLL);
540 		aprint_error_dev(sc->sc_dev,
541 		    "%s: failed to write Hold Clock: %d\n",
542 		    __func__, error);
543 		return 0;
544 	}
545 
546 	/*
547 	 * Write registers in reverse order. The last write (to the Seconds
548 	 * register) will undo the Clock Hold, above.
549 	 */
550 	uint8_t op = I2C_OP_WRITE;
551 	for (signed int i = dm->dm_rtc_size - 1; i >= 0; i--) {
552 		cmdbuf[0] = dm->dm_rtc_start + i;
553 		if ((dm->dm_flags & DSRTC_FLAG_VBATEN) &&
554 				dm->dm_rtc_start + i == dm->dm_vbaten_reg)
555 			bcd[i] |= dm->dm_vbaten_value;
556 		if (dm->dm_rtc_start + i == dm->dm_ch_reg) {
557 			op = I2C_OP_WRITE_WITH_STOP;
558 			if (dm->dm_flags & DSRTC_FLAG_CLOCK_HOLD_REVERSED)
559 				bcd[i] |= dm->dm_ch_value;
560 		}
561 		if ((error = iic_exec(sc->sc_tag, op, sc->sc_address,
562 		    cmdbuf, 1, &bcd[i], 1, I2C_F_POLL)) != 0) {
563 			iic_release_bus(sc->sc_tag, I2C_F_POLL);
564 			aprint_error_dev(sc->sc_dev,
565 			    "%s: failed to write rtc at 0x%x: %d\n",
566 			    __func__, i, error);
567 			/* XXX: Clock Hold is likely still asserted! */
568 			return 0;
569 		}
570 	}
571 	/*
572 	 * If the clock hold register isn't the same register as seconds,
573 	 * we need to reeanble the clock.
574 	 */
575 	if (op != I2C_OP_WRITE_WITH_STOP) {
576 		cmdbuf[0] = dm->dm_ch_reg;
577 		if (dm->dm_flags & DSRTC_FLAG_CLOCK_HOLD_REVERSED)
578 			cmdbuf[1] |= dm->dm_ch_value;
579 		else
580 			cmdbuf[1] &= ~dm->dm_ch_value;
581 
582 		if ((error = iic_exec(sc->sc_tag, I2C_OP_WRITE_WITH_STOP,
583 		    sc->sc_address, cmdbuf, 1, &cmdbuf[1], 1,
584 		    I2C_F_POLL)) != 0) {
585 			iic_release_bus(sc->sc_tag, I2C_F_POLL);
586 			aprint_error_dev(sc->sc_dev,
587 			    "%s: failed to Hold Clock: %d\n",
588 			    __func__, error);
589 			return 0;
590 		}
591 	}
592 
593 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
594 
595 	return 1;
596 }
597 
598 static int
599 dsrtc_gettime_timeval(struct todr_chip_handle *ch, struct timeval *tv)
600 {
601 	struct dsrtc_softc *sc = ch->cookie;
602 	struct timeval check;
603 	int retries;
604 
605 	memset(tv, 0, sizeof(*tv));
606 	memset(&check, 0, sizeof(check));
607 
608 	/*
609 	 * Since we don't support Burst Read, we have to read the clock twice
610 	 * until we get two consecutive identical results.
611 	 */
612 	retries = 5;
613 	do {
614 		dsrtc_clock_read_timeval(sc, &tv->tv_sec);
615 		dsrtc_clock_read_timeval(sc, &check.tv_sec);
616 	} while (memcmp(tv, &check, sizeof(check)) != 0 && --retries);
617 
618 	return 0;
619 }
620 
621 static int
622 dsrtc_settime_timeval(struct todr_chip_handle *ch, struct timeval *tv)
623 {
624 	struct dsrtc_softc *sc = ch->cookie;
625 
626 	if (dsrtc_clock_write_timeval(sc, tv->tv_sec) == 0)
627 		return -1;
628 
629 	return 0;
630 }
631 
632 /*
633  * The RTC probably has a nice Clock Burst Read/Write command, but we can't use
634  * it, since some I2C controllers don't support anything other than single-byte
635  * transfers.
636  */
637 static int
638 dsrtc_clock_read_timeval(struct dsrtc_softc *sc, time_t *tp)
639 {
640 	const struct dsrtc_model * const dm = &sc->sc_model;
641 	uint8_t buf[4];
642 	int error;
643 
644 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
645 		aprint_error_dev(sc->sc_dev,
646 		    "%s: failed to acquire I2C bus: %d\n",
647 		    __func__, error);
648 		return 0;
649 	}
650 
651 	/* read all registers: */
652 	uint8_t reg = dm->dm_rtc_start;
653 	error = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP, sc->sc_address,
654 	     &reg, 1, buf, 4, I2C_F_POLL);
655 
656 	/* Done with I2C */
657 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
658 
659 	if (error != 0) {
660 		aprint_error_dev(sc->sc_dev,
661 		    "%s: failed to read rtc at 0x%x: %d\n",
662 		    __func__, reg, error);
663 		return 0;
664 	}
665 
666 	uint32_t v = (buf[3] << 24) | (buf[2] << 16) | (buf[1] << 8) | buf[0];
667 	*tp = v;
668 
669 	aprint_debug_dev(sc->sc_dev, "%s: cntr=0x%08"PRIx32"\n",
670 	    __func__, v);
671 
672 	return 1;
673 }
674 
675 static int
676 dsrtc_clock_write_timeval(struct dsrtc_softc *sc, time_t t)
677 {
678 	const struct dsrtc_model * const dm = &sc->sc_model;
679 	size_t buflen = dm->dm_rtc_size + 2;
680 	uint8_t buf[buflen];
681 	int error;
682 
683 	KASSERT((dm->dm_flags & DSRTC_FLAG_CLOCK_HOLD) == 0);
684 	KASSERT(dm->dm_ch_reg == dm->dm_rtc_start + 4);
685 
686 	buf[0] = dm->dm_rtc_start;
687 	buf[1] = (t >> 0) & 0xff;
688 	buf[2] = (t >> 8) & 0xff;
689 	buf[3] = (t >> 16) & 0xff;
690 	buf[4] = (t >> 24) & 0xff;
691 	buf[5] = 0;
692 
693 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
694 		aprint_error_dev(sc->sc_dev,
695 		    "%s: failed to acquire I2C bus: %d\n",
696 		    __func__, error);
697 		return 0;
698 	}
699 
700 	error = iic_exec(sc->sc_tag, I2C_OP_WRITE_WITH_STOP, sc->sc_address,
701 	    &buf, buflen, NULL, 0, I2C_F_POLL);
702 
703 	/* Done with I2C */
704 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
705 
706 	/* send data */
707 	if (error != 0) {
708 		aprint_error_dev(sc->sc_dev,
709 		    "%s: failed to set time: %d\n",
710 		    __func__, error);
711 		return 0;
712 	}
713 
714 	return 1;
715 }
716 
717 static int
718 dsrtc_read_temp(struct dsrtc_softc *sc, uint32_t *temp)
719 {
720 	int error, tc;
721 	uint8_t reg = DS3232_TEMP_MSB;
722 	uint8_t buf[2];
723 
724 	if ((sc->sc_model.dm_flags & DSRTC_FLAG_TEMP) == 0)
725 		return ENOTSUP;
726 
727 	if ((error = iic_acquire_bus(sc->sc_tag, I2C_F_POLL)) != 0) {
728 		aprint_error_dev(sc->sc_dev,
729 		    "%s: failed to acquire I2C bus: %d\n",
730 		    __func__, error);
731 		return 0;
732 	}
733 
734 	/* read temperature registers: */
735 	error = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP, sc->sc_address,
736 	     &reg, 1, buf, 2, I2C_F_POLL);
737 
738 	/* Done with I2C */
739 	iic_release_bus(sc->sc_tag, I2C_F_POLL);
740 
741 	if (error != 0) {
742 		aprint_error_dev(sc->sc_dev,
743 		    "%s: failed to read temperature: %d\n",
744 		    __func__, error);
745 		return 0;
746 	}
747 
748 	/* convert to microkelvin */
749 	tc = buf[0] * 1000000 + (buf[1] >> 6) * 250000;
750 	*temp = tc + 273150000;
751 	return 1;
752 }
753 
754 static void
755 dsrtc_refresh(struct sysmon_envsys *sme, envsys_data_t *edata)
756 {
757 	struct dsrtc_softc *sc = sme->sme_cookie;
758 	uint32_t temp = 0;	/* XXX gcc */
759 
760 	if (dsrtc_read_temp(sc, &temp) == 0) {
761 		edata->state = ENVSYS_SINVALID;
762 		return;
763 	}
764 
765 	edata->value_cur = temp;
766 
767 	edata->state = ENVSYS_SVALID;
768 }
769