xref: /netbsd-src/sys/dev/i2c/adm1026.c (revision e6c7e151de239c49d2e38720a061ed9d1fa99309)
1 /*-
2  * Copyright (c) 2015 The NetBSD Foundation, Inc.
3  * All rights reserved.
4  *
5  * This code is derived from software contributed to The NetBSD Foundation
6  * by Julian Coleman.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  *
17  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
18  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
19  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
20  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
21  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
22  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
23  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
24  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
25  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
26  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
27  * POSSIBILITY OF SUCH DAMAGE.
28  */
29 
30 #include <sys/cdefs.h>
31 __KERNEL_RCSID(0, "$NetBSD: adm1026.c,v 1.7 2019/12/23 02:25:28 thorpej Exp $");
32 
33 #include <sys/param.h>
34 #include <sys/systm.h>
35 #include <sys/device.h>
36 #include <sys/kernel.h>
37 #include <sys/sysctl.h>
38 
39 #include <dev/sysmon/sysmonvar.h>
40 
41 #include <dev/i2c/i2cvar.h>
42 #include <dev/i2c/adm1026reg.h>
43 
44 /* Voltage/analog sensors descriptions and registers */
45 struct adm1026_volts_info {
46 	const char* desc;
47 	int incr;
48 	uint8_t reg, check_tdm2;
49 };
50 
51 /* Voltage maximums (in mV) from datasheet table 7 divided by 255 increments */
52 static struct adm1026_volts_info adm1026_volts_table[] = {
53 	{ "Vbatt", 15624, ADM1026_VBAT_VAL, 0 },
54 	{ "V3.3 standby", 17345, ADM1026_33VSTBY_VAL, 0 },
55 	{ "V3.3 main", 17345, ADM1026_33VMAIN_VAL, 0 },
56 	{ "V5.0", 26016, ADM1026_50V_VAL, 0 },
57 	{ "Vccp", 11718, ADM1026_VCCP_VAL, 0 },
58 	{ "V+12", 62502, ADM1026_12V_VAL, 0 },
59 	{ "V-12", -62502, ADM1026_N12V_VAL, 0 },
60 	{ "V3.0 0", 11718, ADM1026_AIN_VAL(0), 0 },
61 	{ "V3.0 1", 11718, ADM1026_AIN_VAL(1), 0 },
62 	{ "V3.0 2", 11718, ADM1026_AIN_VAL(2), 0 },
63 	{ "V3.0 3", 11718, ADM1026_AIN_VAL(3), 0 },
64 	{ "V3.0 4", 11718, ADM1026_AIN_VAL(4), 0 },
65 	{ "V3.0 5", 11718, ADM1026_AIN_VAL(5), 0 },
66 	{ "V2.5 0", 9765, ADM1026_AIN_VAL(6), 0 },
67 	{ "V2.5 1", 9765, ADM1026_AIN_VAL(7), 0 },
68 	{ "V2.5 2", 9765, ADM1026_AIN8_VAL, 1 },
69 	{ "V2.5 3", 9765, ADM1026_TDM2_AIN9_VAL, 1 }
70 };
71 
72 /* Maximum number of each type of sensor */
73 #define ADM1026_MAX_FANS	8
74 #define ADM1026_MAX_TEMPS	3
75 #define ADM1026_MAX_VOLTS	(sizeof(adm1026_volts_table) / \
76 				    sizeof (adm1026_volts_table[0]))
77 
78 /* Map sensor to/from sysmon numbers */
79 #define ADM1026_FAN_NUM(x)	(x)
80 #define ADM1026_TEMP_NUM(x)	(x + sc->sc_nfans)
81 #define ADM1026_VOLT_NUM(x)	(x + sc->sc_nfans + sc->sc_ntemps)
82 #define ADM1026_NUM_FAN(x)	(x)
83 #define ADM1026_NUM_TEMP(x)	(x - sc->sc_nfans)
84 #define ADM1026_NUM_VOLT(x)	(x - sc->sc_nfans - sc->sc_ntemps)
85 
86 struct adm1026_softc {
87 	device_t sc_dev;
88 	i2c_tag_t sc_tag;
89 	int sc_address;
90 	bool sc_multi_read;
91 
92 	uint8_t sc_rev, sc_cfg[2];
93 	int sc_nfans, sc_ntemps;	/* Map sysmon numbers to sensors */
94 	int sc_fandiv[ADM1026_MAX_FANS], sc_temp_off[ADM1026_MAX_TEMPS];
95 	struct sysmon_envsys *sc_sme;
96 	envsys_data_t sc_sensor[ADM1026_MAX_FANS + ADM1026_MAX_TEMPS +
97 	    ADM1026_MAX_VOLTS];
98 };
99 
100 static int adm1026_match(device_t, cfdata_t, void *);
101 static int adm1026_ident(struct adm1026_softc *, int);
102 static void adm1026_attach(device_t, device_t, void *);
103 static int adm1026_detach(device_t, int);
104 bool adm1026_pmf_suspend(device_t, const pmf_qual_t *);
105 bool adm1026_pmf_resume(device_t, const pmf_qual_t *);
106 
107 static void adm1026_setup_fans(struct adm1026_softc *sc, int div2_val);
108 static void adm1026_setup_temps(struct adm1026_softc *sc);
109 static void adm1026_setup_volts(struct adm1026_softc *sc);
110 
111 void adm1026_refresh(struct sysmon_envsys *sme, envsys_data_t *edata);
112 static void adm1026_read_fan(struct adm1026_softc *sc, envsys_data_t *edata);
113 static void adm1026_read_temp(struct adm1026_softc *sc, envsys_data_t *edata);
114 static void adm1026_read_volt(struct adm1026_softc *sc, envsys_data_t *edata);
115 
116 static int adm1026_read_reg(struct adm1026_softc *sc,
117     uint8_t reg, uint8_t *val);
118 static int adm1026_write_reg(struct adm1026_softc *sc,
119     uint8_t reg, uint8_t val);
120 
121 CFATTACH_DECL_NEW(adm1026hm, sizeof(struct adm1026_softc),
122 	adm1026_match, adm1026_attach, adm1026_detach, NULL);
123 
124 static const struct device_compatible_entry compat_data[] = {
125 	{ "i2c-adm1026",		0 },
126 	{ NULL,				0 }
127 };
128 
129 static int
130 adm1026_match(device_t parent, cfdata_t cf, void *aux)
131 {
132 	struct i2c_attach_args *ia = aux;
133 	struct adm1026_softc sc;	/* For chip ident */
134 	int match_result;
135 
136 	sc.sc_tag = ia->ia_tag;
137 	sc.sc_address = ia->ia_addr;
138 
139 	if (iic_use_direct_match(ia, cf, compat_data, &match_result))
140 		return match_result;
141 
142 	if (ia->ia_addr == ADM1026_ADDR1 && adm1026_ident(&sc, 1))
143 		return I2C_MATCH_ADDRESS_AND_PROBE;
144 
145 	return 0;
146 }
147 
148 static int
149 adm1026_ident(struct adm1026_softc *sc, int probe_only)
150 {
151 	uint8_t val;
152 	int err;
153 
154 	/* Manufacturer ID and revision/stepping */
155 	err = adm1026_read_reg(sc, ADM1026_ID, &val);
156 	if (err || val != ADM1026_MANF_ID) {
157 		if (!probe_only)
158 			aprint_verbose("adm1026_ident: "
159 			    "manufacturer ID invalid or missing\n");
160 		return 0;
161 	}
162 	err = adm1026_read_reg(sc, ADM1026_REV, &sc->sc_rev);
163 	if (err || ADM1026_REVISION(sc->sc_rev) != ADM1026_MANF_REV) {
164 		if (!probe_only)
165 			aprint_verbose("adm1026_ident: "
166 			    "manufacturer revision invalid or missing\n");
167 		return 0;
168 	}
169 	return 1;
170 }
171 
172 static void
173 adm1026_attach(device_t parent, device_t self, void *aux)
174 {
175 	struct adm1026_softc *sc = device_private(self);
176 	struct i2c_attach_args *ia = aux;
177 	prop_dictionary_t props = device_properties(self);
178 	uint8_t val, fan_div2;
179 	int err, div2_val;
180 
181 	sc->sc_tag = ia->ia_tag;
182 	sc->sc_address = ia->ia_addr;
183 	sc->sc_dev = self;
184 
185 	sc->sc_multi_read = false;
186 	prop_dictionary_get_bool(props, "multi_read", &sc->sc_multi_read);
187 	if (prop_dictionary_get_uint8(props, "fan_div2", &fan_div2) != 0)
188 		div2_val = fan_div2;
189 	else
190 		div2_val = -1;
191 
192 	(void) adm1026_ident(sc, 0);
193 	aprint_normal(": ADM1026 hardware monitor: rev. 0x%x, step. 0x%x\n",
194 	    ADM1026_REVISION(sc->sc_rev), ADM1026_STEPPING(sc->sc_rev));
195 
196 	/*
197 	 * Start monitoring if not already monitoring.
198 	 * Wait 1.8s for the fan readings to stabilise.
199 	 */
200 	if ((err = adm1026_read_reg(sc, ADM1026_CONF1, &val)) != 0) {
201 		aprint_error_dev(sc->sc_dev, ": unable to read conf1\n");
202 		return;
203 	}
204 	if (!(val & ADM1026_CONF1_MONITOR)) {
205 		aprint_normal_dev(sc->sc_dev,
206 		    ": starting monitoring, waiting 1.8s for readings\n");
207 		val |= ADM1026_CONF1_MONITOR;
208 		if ((err = adm1026_write_reg(sc, ADM1026_CONF1, val)) != 0) {
209 			aprint_error_dev(sc->sc_dev,
210 			    ": unable to write conf1\n");
211 			return;
212 		}
213 		delay(1800000);
214 	}
215 	sc->sc_cfg[0] = val;
216 
217 	sc->sc_sme = sysmon_envsys_create();
218 	sc->sc_nfans = 0;
219 	adm1026_setup_fans(sc, div2_val);
220 	sc->sc_ntemps = 0;
221 	adm1026_setup_temps(sc);
222 	adm1026_setup_volts(sc);
223 	aprint_normal_dev(self, "%d fans, %d temperatures, %d voltages\n",
224 	    sc->sc_nfans, sc->sc_ntemps, sc->sc_ntemps == 3 ? 15 : 17);
225 
226         sc->sc_sme->sme_name = device_xname(self);
227         sc->sc_sme->sme_cookie = sc;
228         sc->sc_sme->sme_refresh = adm1026_refresh;
229 	if (sysmon_envsys_register(sc->sc_sme)) {
230 		aprint_error_dev(self,
231 		    "unable to register with sysmon\n");
232 		sysmon_envsys_destroy(sc->sc_sme);
233 		return;
234 	}
235 
236 	if (!pmf_device_register(self, adm1026_pmf_suspend, adm1026_pmf_resume))
237 		aprint_error_dev(self, "couldn't establish power handler\n");
238 
239 	return;
240 }
241 
242 /*
243  * We could stop (suspend/detach) and restart (resume) monitoring,
244  * but we don't do that because some machines have separate
245  * management hardware which can read the sensors.
246  */
247 bool
248 adm1026_pmf_suspend(device_t dev, const pmf_qual_t *qual)
249 {
250 	return true;
251 }
252 
253 bool
254 adm1026_pmf_resume(device_t dev, const pmf_qual_t *qual)
255 {
256 	return true;
257 }
258 
259 static int
260 adm1026_detach(device_t self, int flags)
261 {
262 	struct adm1026_softc *sc = device_private(self);
263 
264 	pmf_device_deregister(self);
265 
266 	sysmon_envsys_unregister(sc->sc_sme);
267 	sc->sc_sme = NULL;
268 
269 	return 0;
270 }
271 
272 static void
273 adm1026_setup_fans(struct adm1026_softc *sc, int div2_val)
274 {
275 	int i, err = 0;
276 	uint8_t div1, div2;
277 
278 	/* Read fan-related registers (configuration and divisors) */
279 	if ((err = adm1026_read_reg(sc, ADM1026_CONF2, &sc->sc_cfg[1])) != 0) {
280 		aprint_error_dev(sc->sc_dev, "unable to read conf2\n");
281 		return;
282 	}
283 	if ((err = adm1026_read_reg(sc, ADM1026_FAN_DIV1, &div1)) != 0) {
284 		aprint_error_dev(sc->sc_dev, "unable to read fan_div1\n");
285 		return;
286 	}
287 	sc->sc_fandiv[0] = 1 << ADM1026_FAN0_DIV(div1);
288 	sc->sc_fandiv[1] = 1 << ADM1026_FAN1_DIV(div1);
289 	sc->sc_fandiv[2] = 1 << ADM1026_FAN2_DIV(div1);
290 	sc->sc_fandiv[3] = 1 << ADM1026_FAN3_DIV(div1);
291 	if (div2_val < 0) {
292 		if ((err =
293 		    adm1026_read_reg(sc, ADM1026_FAN_DIV2, &div2)) != 0) {
294 			aprint_error_dev(sc->sc_dev,
295 			    "unable to read fan_div2\n");
296 			return;
297 		}
298 	} else
299 		div2 = div2_val;
300 	sc->sc_fandiv[4] = 1 << ADM1026_FAN4_DIV(div2);
301 	sc->sc_fandiv[5] = 1 << ADM1026_FAN5_DIV(div2);
302 	sc->sc_fandiv[6] = 1 << ADM1026_FAN6_DIV(div2);
303 	sc->sc_fandiv[7] = 1 << ADM1026_FAN7_DIV(div2);
304 
305 	for (i = 0; i < ADM1026_MAX_FANS; i++) {
306 		sc->sc_sensor[ADM1026_FAN_NUM(i)].state = ENVSYS_SINVALID;
307 		/* Check configuration2 register to see which pins are fans. */
308 		if (ADM1026_PIN_IS_FAN(sc->sc_cfg[1], i)) {
309 			sc->sc_sensor[ADM1026_FAN_NUM(i)].units =
310 			    ENVSYS_SFANRPM;
311 			snprintf(sc->sc_sensor[ADM1026_FAN_NUM(i)].desc,
312 			    sizeof(sc->sc_sensor[ADM1026_FAN_NUM(i)].desc),
313 			    "fan %d", ADM1026_FAN_NUM(i));
314 			sc->sc_nfans++;
315 			if (sysmon_envsys_sensor_attach(
316 			    sc->sc_sme, &sc->sc_sensor[ADM1026_FAN_NUM(i)])) {
317 				sysmon_envsys_destroy(sc->sc_sme);
318 				aprint_error_dev(sc->sc_dev,
319 				    "unable to attach fan %d at sysmon\n", i);
320 				return;
321 			}
322 		}
323 	}
324 }
325 
326 static void
327 adm1026_setup_temps(struct adm1026_softc *sc)
328 {
329 	int i;
330 	uint8_t val;
331 
332 	/* Temperature offsets */
333 	if (adm1026_read_reg(sc, ADM1026_INT_TEMP_OFF, &val)
334 	    != 0) {
335 		aprint_error_dev(sc->sc_dev, "unable to read int temp. off.\n");
336 		return;
337 	}
338 	if (val & 0x80)
339 		sc->sc_temp_off[0] = 0 - 1000000 * (val & 0x7f);
340 	else
341 		sc->sc_temp_off[0] = 1000000 * (val & 0x7f);
342 	if (adm1026_read_reg(sc, ADM1026_TDM1_OFF, &val) != 0) {
343 		aprint_error_dev(sc->sc_dev, "unable to read tdm1 off.\n");
344 		return;
345 	}
346 	if (val & 0x80)
347 		sc->sc_temp_off[1] = 0 - 1000000 * (val & 0x7f);
348 	else
349 		sc->sc_temp_off[1] = 1000000 * (val & 0x7f);
350 	if (adm1026_read_reg(sc, ADM1026_TDM2_OFF, &val) != 0) {
351 		aprint_error_dev(sc->sc_dev, "unable to read tdm2 off.\n");
352 		return;
353 	}
354 	if (val & 0x80)
355 		sc->sc_temp_off[2] = 0 - 1000000 * (val & 0x7f);
356 	else
357 		sc->sc_temp_off[2] = 1000000 * (val & 0x7f);
358 
359 	strlcpy(sc->sc_sensor[ADM1026_TEMP_NUM(0)].desc, "internal",
360 	    sizeof(sc->sc_sensor[ADM1026_TEMP_NUM(0)].desc));
361 	strlcpy(sc->sc_sensor[ADM1026_TEMP_NUM(1)].desc, "external 1",
362 	    sizeof(sc->sc_sensor[ADM1026_TEMP_NUM(1)].desc));
363 	strlcpy(sc->sc_sensor[ADM1026_TEMP_NUM(2)].desc, "external 2",
364 	    sizeof(sc->sc_sensor[ADM1026_TEMP_NUM(2)].desc));
365 	for (i = 0; i < ADM1026_MAX_TEMPS; i++) {
366 		/* Check configuration1 register to see if TDM2 is configured */
367 		if (i == 2 && !ADM1026_PIN_IS_TDM2(sc->sc_cfg[0]))
368 			continue;
369 		sc->sc_sensor[ADM1026_TEMP_NUM(i)].units = ENVSYS_STEMP;
370 		sc->sc_sensor[ADM1026_TEMP_NUM(i)].state = ENVSYS_SINVALID;
371 		sc->sc_ntemps++;
372 		if (sysmon_envsys_sensor_attach(
373 		    sc->sc_sme, &sc->sc_sensor[ADM1026_TEMP_NUM(i)])) {
374 			sysmon_envsys_destroy(sc->sc_sme);
375 			aprint_error_dev(sc->sc_dev,
376 			    "unable to attach temp %d at sysmon\n", i);
377 			return;
378 		}
379 	}
380 }
381 
382 static void
383 adm1026_setup_volts(struct adm1026_softc *sc)
384 {
385 	int i;
386 
387 	for (i = 0; i < ADM1026_MAX_VOLTS; i++) {
388 		/* Check configuration1 register to see if TDM2 is configured */
389 		if (adm1026_volts_table[i].check_tdm2 &&
390 		    ADM1026_PIN_IS_TDM2(sc->sc_cfg[0]))
391 			continue;
392 		strlcpy(sc->sc_sensor[ADM1026_VOLT_NUM(i)].desc,
393 		    adm1026_volts_table[i].desc,
394 		    sizeof(sc->sc_sensor[ADM1026_VOLT_NUM(i)].desc));
395 		sc->sc_sensor[ADM1026_VOLT_NUM(i)].units = ENVSYS_SVOLTS_DC;
396 		sc->sc_sensor[ADM1026_VOLT_NUM(i)].state = ENVSYS_SINVALID;
397 		if (sysmon_envsys_sensor_attach(
398 		    sc->sc_sme, &sc->sc_sensor[ADM1026_VOLT_NUM(i)])) {
399 			sysmon_envsys_destroy(sc->sc_sme);
400 			aprint_error_dev(sc->sc_dev,
401 			    "unable to attach volts %d at sysmon\n", i);
402 			return;
403 		}
404 	}
405 }
406 
407 void
408 adm1026_refresh(struct sysmon_envsys *sme, envsys_data_t *edata)
409 {
410 	struct adm1026_softc *sc = sme->sme_cookie;
411 
412 	if (edata->sensor < sc->sc_nfans)
413 		adm1026_read_fan(sc, edata);
414 	else if (edata->sensor < sc->sc_nfans + sc->sc_ntemps)
415 		adm1026_read_temp(sc, edata);
416 	else
417 		adm1026_read_volt(sc, edata);
418 }
419 
420 static void
421 adm1026_read_fan(struct adm1026_softc *sc, envsys_data_t *edata)
422 {
423 	int fan = ADM1026_NUM_FAN(edata->sensor);
424 	int err;
425 	uint8_t	val;
426 
427 	if ((err = adm1026_read_reg(sc, ADM1026_FAN_VAL(fan), &val)) != 0) {
428 		edata->state = ENVSYS_SINVALID;
429 		return;
430 	}
431 	if (val == 0xff || val == 0x00)	/* Fan missing or stopped */
432 		edata->value_cur = 0;
433 	else
434 		edata->value_cur = 1350000 / (val * sc->sc_fandiv[fan]);
435 	edata->state = ENVSYS_SVALID;
436 }
437 
438 static void
439 adm1026_read_temp(struct adm1026_softc *sc, envsys_data_t *edata)
440 {
441 	int temp = ADM1026_NUM_TEMP(edata->sensor);
442 	int err;
443 	uint8_t	val;
444 
445 	if (temp == 0)
446 		err = adm1026_read_reg(sc, ADM1026_INT_TEMP_VAL, &val);
447 	else if (temp == 1)
448 		err = adm1026_read_reg(sc, ADM1026_TDM1_VAL, &val);
449 	else
450 		err = adm1026_read_reg(sc, ADM1026_TDM2_AIN9_VAL, &val);
451 	if (err) {
452 		edata->state = ENVSYS_SINVALID;
453 		return;
454 	}
455 
456 	if (val & 0x80)	/* Negative temperature */
457 		edata->value_cur = 273150000 - sc->sc_temp_off[temp] -
458 		    1000000 * (val & 0x7f);
459 	else		/* Positive temperature */
460 		edata->value_cur = 273150000 - sc->sc_temp_off[temp] +
461 		    1000000 * val;
462 	edata->state = ENVSYS_SVALID;
463 }
464 
465 static void
466 adm1026_read_volt(struct adm1026_softc *sc, envsys_data_t *edata)
467 {
468 	int volt = ADM1026_NUM_VOLT(edata->sensor);
469 	int err;
470 	uint8_t	val;
471 
472 	err = adm1026_read_reg(sc, adm1026_volts_table[volt].reg, &val);
473 	if (err) {
474 		edata->state = ENVSYS_SINVALID;
475 		return;
476 	}
477 	/* Vbatt is not valid for < 1.5V */
478 	if (volt == 0 && val < 0x60)
479 		edata->state = ENVSYS_SINVALID;
480 	edata->value_cur = (int) val * adm1026_volts_table[volt].incr;
481 	edata->state = ENVSYS_SVALID;
482 }
483 
484 static int
485 adm1026_read_reg(struct adm1026_softc *sc, uint8_t reg, uint8_t *val)
486 {
487 #define ADM1026_READ_RETRIES	5
488 	int i, j, err = 0;
489 	uint8_t creg, cval, tmp[ADM1026_READ_RETRIES + 1];
490 
491 	if ((err = iic_acquire_bus(sc->sc_tag, 0)) != 0)
492 		return err;
493 	/* Standard ADM1026 */
494 	if (sc->sc_multi_read == false) {
495 		err = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP,
496 		    sc->sc_address, &reg, 1, val, 1, 0);
497 	/*
498 	 * The ADM1026 found in some Sun machines sometimes reads bogus values.
499 	 * We'll read at least twice and check that we get (nearly) the same
500 	 * value.  If not, we'll read another register and then re-read the
501 	 * first.
502 	 */
503 	} else {
504 		if (reg == ADM1026_CONF1)
505 			creg = ADM1026_CONF2;
506 		else
507 			creg = ADM1026_CONF1;
508 		if ((err = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP,
509 		    sc->sc_address, &reg, 1, &tmp[0], 1, 0)) != 0) {
510 			iic_release_bus(sc->sc_tag, 0);
511 			return err;
512 		}
513 		for (i = 1; i <= ADM1026_READ_RETRIES; i++) {
514 			if ((err = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP,
515 			    sc->sc_address, &reg, 1, &tmp[i], 1, 0)) != 0)
516 				break;
517 			for (j = 0; j < i; j++)
518 				if (abs(tmp[j] - tmp[i]) < 3) {
519 					*val = tmp[i];
520 					iic_release_bus(sc->sc_tag, 0);
521 					return 0;
522 				}
523 			if ((err = iic_exec(sc->sc_tag, I2C_OP_READ_WITH_STOP,
524 			    sc->sc_address, &creg, 1, &cval, 1, 0)) != 0)
525 				break;
526 			err = -1;	/* Return error if we don't match. */
527 		}
528 	}
529 	iic_release_bus(sc->sc_tag, 0);
530 	return err;
531 }
532 
533 static int
534 adm1026_write_reg(struct adm1026_softc *sc, uint8_t reg, uint8_t val)
535 {
536 	int err = 0;
537 
538 	if ((err = iic_acquire_bus(sc->sc_tag, 0)) != 0)
539 		return err;
540 	err = iic_exec(sc->sc_tag, I2C_OP_WRITE_WITH_STOP, sc->sc_address,
541 	    &reg, 1, &val, 1, 0);
542 	iic_release_bus(sc->sc_tag, 0);
543 	return err;
544 }
545