xref: /linux/drivers/hwmon/max6650.c (revision e5c86679d5e864947a52fb31e45a425dea3e7fa9)
1 /*
2  * max6650.c - Part of lm_sensors, Linux kernel modules for hardware
3  *             monitoring.
4  *
5  * (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
6  *
7  * based on code written by John Morris <john.morris@spirentcom.com>
8  * Copyright (c) 2003 Spirent Communications
9  * and Claus Gindhart <claus.gindhart@kontron.com>
10  *
11  * This module has only been tested with the MAX6650 chip. It should
12  * also work with the MAX6651. It does not distinguish max6650 and max6651
13  * chips.
14  *
15  * The datasheet was last seen at:
16  *
17  *        http://pdfserv.maxim-ic.com/en/ds/MAX6650-MAX6651.pdf
18  *
19  * This program is free software; you can redistribute it and/or modify
20  * it under the terms of the GNU General Public License as published by
21  * the Free Software Foundation; either version 2 of the License, or
22  * (at your option) any later version.
23  *
24  * This program is distributed in the hope that it will be useful,
25  * but WITHOUT ANY WARRANTY; without even the implied warranty of
26  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
27  * GNU General Public License for more details.
28  *
29  * You should have received a copy of the GNU General Public License
30  * along with this program; if not, write to the Free Software
31  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
32  */
33 
34 #include <linux/module.h>
35 #include <linux/init.h>
36 #include <linux/slab.h>
37 #include <linux/jiffies.h>
38 #include <linux/i2c.h>
39 #include <linux/hwmon.h>
40 #include <linux/hwmon-sysfs.h>
41 #include <linux/err.h>
42 #include <linux/of_device.h>
43 
44 /*
45  * Insmod parameters
46  */
47 
48 /* fan_voltage: 5=5V fan, 12=12V fan, 0=don't change */
49 static int fan_voltage;
50 /* prescaler: Possible values are 1, 2, 4, 8, 16 or 0 for don't change */
51 static int prescaler;
52 /* clock: The clock frequency of the chip (max6651 can be clocked externally) */
53 static int clock = 254000;
54 
55 module_param(fan_voltage, int, S_IRUGO);
56 module_param(prescaler, int, S_IRUGO);
57 module_param(clock, int, S_IRUGO);
58 
59 /*
60  * MAX 6650/6651 registers
61  */
62 
63 #define MAX6650_REG_SPEED	0x00
64 #define MAX6650_REG_CONFIG	0x02
65 #define MAX6650_REG_GPIO_DEF	0x04
66 #define MAX6650_REG_DAC		0x06
67 #define MAX6650_REG_ALARM_EN	0x08
68 #define MAX6650_REG_ALARM	0x0A
69 #define MAX6650_REG_TACH0	0x0C
70 #define MAX6650_REG_TACH1	0x0E
71 #define MAX6650_REG_TACH2	0x10
72 #define MAX6650_REG_TACH3	0x12
73 #define MAX6650_REG_GPIO_STAT	0x14
74 #define MAX6650_REG_COUNT	0x16
75 
76 /*
77  * Config register bits
78  */
79 
80 #define MAX6650_CFG_V12			0x08
81 #define MAX6650_CFG_PRESCALER_MASK	0x07
82 #define MAX6650_CFG_PRESCALER_2		0x01
83 #define MAX6650_CFG_PRESCALER_4		0x02
84 #define MAX6650_CFG_PRESCALER_8		0x03
85 #define MAX6650_CFG_PRESCALER_16	0x04
86 #define MAX6650_CFG_MODE_MASK		0x30
87 #define MAX6650_CFG_MODE_ON		0x00
88 #define MAX6650_CFG_MODE_OFF		0x10
89 #define MAX6650_CFG_MODE_CLOSED_LOOP	0x20
90 #define MAX6650_CFG_MODE_OPEN_LOOP	0x30
91 #define MAX6650_COUNT_MASK		0x03
92 
93 /*
94  * Alarm status register bits
95  */
96 
97 #define MAX6650_ALRM_MAX	0x01
98 #define MAX6650_ALRM_MIN	0x02
99 #define MAX6650_ALRM_TACH	0x04
100 #define MAX6650_ALRM_GPIO1	0x08
101 #define MAX6650_ALRM_GPIO2	0x10
102 
103 /* Minimum and maximum values of the FAN-RPM */
104 #define FAN_RPM_MIN 240
105 #define FAN_RPM_MAX 30000
106 
107 #define DIV_FROM_REG(reg) (1 << (reg & 7))
108 
109 /*
110  * Client data (each client gets its own)
111  */
112 
113 struct max6650_data {
114 	struct i2c_client *client;
115 	const struct attribute_group *groups[3];
116 	struct mutex update_lock;
117 	int nr_fans;
118 	char valid; /* zero until following fields are valid */
119 	unsigned long last_updated; /* in jiffies */
120 
121 	/* register values */
122 	u8 speed;
123 	u8 config;
124 	u8 tach[4];
125 	u8 count;
126 	u8 dac;
127 	u8 alarm;
128 };
129 
130 static const u8 tach_reg[] = {
131 	MAX6650_REG_TACH0,
132 	MAX6650_REG_TACH1,
133 	MAX6650_REG_TACH2,
134 	MAX6650_REG_TACH3,
135 };
136 
137 static const struct of_device_id max6650_dt_match[] = {
138 	{
139 		.compatible = "maxim,max6650",
140 		.data = (void *)1
141 	},
142 	{
143 		.compatible = "maxim,max6651",
144 		.data = (void *)4
145 	},
146 	{ },
147 };
148 MODULE_DEVICE_TABLE(of, max6650_dt_match);
149 
150 static struct max6650_data *max6650_update_device(struct device *dev)
151 {
152 	struct max6650_data *data = dev_get_drvdata(dev);
153 	struct i2c_client *client = data->client;
154 	int i;
155 
156 	mutex_lock(&data->update_lock);
157 
158 	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
159 		data->speed = i2c_smbus_read_byte_data(client,
160 						       MAX6650_REG_SPEED);
161 		data->config = i2c_smbus_read_byte_data(client,
162 							MAX6650_REG_CONFIG);
163 		for (i = 0; i < data->nr_fans; i++) {
164 			data->tach[i] = i2c_smbus_read_byte_data(client,
165 								 tach_reg[i]);
166 		}
167 		data->count = i2c_smbus_read_byte_data(client,
168 							MAX6650_REG_COUNT);
169 		data->dac = i2c_smbus_read_byte_data(client, MAX6650_REG_DAC);
170 
171 		/*
172 		 * Alarms are cleared on read in case the condition that
173 		 * caused the alarm is removed. Keep the value latched here
174 		 * for providing the register through different alarm files.
175 		 */
176 		data->alarm |= i2c_smbus_read_byte_data(client,
177 							MAX6650_REG_ALARM);
178 
179 		data->last_updated = jiffies;
180 		data->valid = 1;
181 	}
182 
183 	mutex_unlock(&data->update_lock);
184 
185 	return data;
186 }
187 
188 /*
189  * Change the operating mode of the chip (if needed).
190  * mode is one of the MAX6650_CFG_MODE_* values.
191  */
192 static int max6650_set_operating_mode(struct max6650_data *data, u8 mode)
193 {
194 	int result;
195 	u8 config = data->config;
196 
197 	if (mode == (config & MAX6650_CFG_MODE_MASK))
198 		return 0;
199 
200 	config = (config & ~MAX6650_CFG_MODE_MASK) | mode;
201 
202 	result = i2c_smbus_write_byte_data(data->client, MAX6650_REG_CONFIG,
203 					   config);
204 	if (result < 0)
205 		return result;
206 
207 	data->config = config;
208 
209 	return 0;
210 }
211 
212 static ssize_t get_fan(struct device *dev, struct device_attribute *devattr,
213 		       char *buf)
214 {
215 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
216 	struct max6650_data *data = max6650_update_device(dev);
217 	int rpm;
218 
219 	/*
220 	 * Calculation details:
221 	 *
222 	 * Each tachometer counts over an interval given by the "count"
223 	 * register (0.25, 0.5, 1 or 2 seconds). This module assumes
224 	 * that the fans produce two pulses per revolution (this seems
225 	 * to be the most common).
226 	 */
227 
228 	rpm = ((data->tach[attr->index] * 120) / DIV_FROM_REG(data->count));
229 	return sprintf(buf, "%d\n", rpm);
230 }
231 
232 /*
233  * Set the fan speed to the specified RPM (or read back the RPM setting).
234  * This works in closed loop mode only. Use pwm1 for open loop speed setting.
235  *
236  * The MAX6650/1 will automatically control fan speed when in closed loop
237  * mode.
238  *
239  * Assumptions:
240  *
241  * 1) The MAX6650/1 internal 254kHz clock frequency is set correctly. Use
242  *    the clock module parameter if you need to fine tune this.
243  *
244  * 2) The prescaler (low three bits of the config register) has already
245  *    been set to an appropriate value. Use the prescaler module parameter
246  *    if your BIOS doesn't initialize the chip properly.
247  *
248  * The relevant equations are given on pages 21 and 22 of the datasheet.
249  *
250  * From the datasheet, the relevant equation when in regulation is:
251  *
252  *    [fCLK / (128 x (KTACH + 1))] = 2 x FanSpeed / KSCALE
253  *
254  * where:
255  *
256  *    fCLK is the oscillator frequency (either the 254kHz internal
257  *         oscillator or the externally applied clock)
258  *
259  *    KTACH is the value in the speed register
260  *
261  *    FanSpeed is the speed of the fan in rps
262  *
263  *    KSCALE is the prescaler value (1, 2, 4, 8, or 16)
264  *
265  * When reading, we need to solve for FanSpeed. When writing, we need to
266  * solve for KTACH.
267  *
268  * Note: this tachometer is completely separate from the tachometers
269  * used to measure the fan speeds. Only one fan's speed (fan1) is
270  * controlled.
271  */
272 
273 static ssize_t fan1_target_show(struct device *dev,
274 				struct device_attribute *devattr, char *buf)
275 {
276 	struct max6650_data *data = max6650_update_device(dev);
277 	int kscale, ktach, rpm;
278 
279 	/*
280 	 * Use the datasheet equation:
281 	 *
282 	 *    FanSpeed = KSCALE x fCLK / [256 x (KTACH + 1)]
283 	 *
284 	 * then multiply by 60 to give rpm.
285 	 */
286 
287 	kscale = DIV_FROM_REG(data->config);
288 	ktach = data->speed;
289 	rpm = 60 * kscale * clock / (256 * (ktach + 1));
290 	return sprintf(buf, "%d\n", rpm);
291 }
292 
293 static int max6650_set_target(struct max6650_data *data, unsigned long rpm)
294 {
295 	int kscale, ktach;
296 
297 	if (rpm == 0)
298 		return max6650_set_operating_mode(data, MAX6650_CFG_MODE_OFF);
299 
300 	rpm = clamp_val(rpm, FAN_RPM_MIN, FAN_RPM_MAX);
301 
302 	/*
303 	 * Divide the required speed by 60 to get from rpm to rps, then
304 	 * use the datasheet equation:
305 	 *
306 	 *     KTACH = [(fCLK x KSCALE) / (256 x FanSpeed)] - 1
307 	 */
308 
309 	kscale = DIV_FROM_REG(data->config);
310 	ktach = ((clock * kscale) / (256 * rpm / 60)) - 1;
311 	if (ktach < 0)
312 		ktach = 0;
313 	if (ktach > 255)
314 		ktach = 255;
315 	data->speed = ktach;
316 
317 	return i2c_smbus_write_byte_data(data->client, MAX6650_REG_SPEED,
318 					 data->speed);
319 }
320 
321 static ssize_t fan1_target_store(struct device *dev,
322 				 struct device_attribute *devattr,
323 				 const char *buf, size_t count)
324 {
325 	struct max6650_data *data = dev_get_drvdata(dev);
326 	unsigned long rpm;
327 	int err;
328 
329 	err = kstrtoul(buf, 10, &rpm);
330 	if (err)
331 		return err;
332 
333 	mutex_lock(&data->update_lock);
334 
335 	err = max6650_set_target(data, rpm);
336 
337 	mutex_unlock(&data->update_lock);
338 
339 	if (err < 0)
340 		return err;
341 
342 	return count;
343 }
344 
345 /*
346  * Get/set the fan speed in open loop mode using pwm1 sysfs file.
347  * Speed is given as a relative value from 0 to 255, where 255 is maximum
348  * speed. Note that this is done by writing directly to the chip's DAC,
349  * it won't change the closed loop speed set by fan1_target.
350  * Also note that due to rounding errors it is possible that you don't read
351  * back exactly the value you have set.
352  */
353 
354 static ssize_t pwm1_show(struct device *dev, struct device_attribute *devattr,
355 			 char *buf)
356 {
357 	int pwm;
358 	struct max6650_data *data = max6650_update_device(dev);
359 
360 	/*
361 	 * Useful range for dac is 0-180 for 12V fans and 0-76 for 5V fans.
362 	 * Lower DAC values mean higher speeds.
363 	 */
364 	if (data->config & MAX6650_CFG_V12)
365 		pwm = 255 - (255 * (int)data->dac)/180;
366 	else
367 		pwm = 255 - (255 * (int)data->dac)/76;
368 
369 	if (pwm < 0)
370 		pwm = 0;
371 
372 	return sprintf(buf, "%d\n", pwm);
373 }
374 
375 static ssize_t pwm1_store(struct device *dev,
376 			  struct device_attribute *devattr, const char *buf,
377 			  size_t count)
378 {
379 	struct max6650_data *data = dev_get_drvdata(dev);
380 	struct i2c_client *client = data->client;
381 	unsigned long pwm;
382 	int err;
383 
384 	err = kstrtoul(buf, 10, &pwm);
385 	if (err)
386 		return err;
387 
388 	pwm = clamp_val(pwm, 0, 255);
389 
390 	mutex_lock(&data->update_lock);
391 
392 	if (data->config & MAX6650_CFG_V12)
393 		data->dac = 180 - (180 * pwm)/255;
394 	else
395 		data->dac = 76 - (76 * pwm)/255;
396 	err = i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);
397 
398 	mutex_unlock(&data->update_lock);
399 
400 	return err < 0 ? err : count;
401 }
402 
403 /*
404  * Get/Set controller mode:
405  * Possible values:
406  * 0 = Fan always on
407  * 1 = Open loop, Voltage is set according to speed, not regulated.
408  * 2 = Closed loop, RPM for all fans regulated by fan1 tachometer
409  * 3 = Fan off
410  */
411 static ssize_t pwm1_enable_show(struct device *dev,
412 				struct device_attribute *devattr, char *buf)
413 {
414 	struct max6650_data *data = max6650_update_device(dev);
415 	int mode = (data->config & MAX6650_CFG_MODE_MASK) >> 4;
416 	int sysfs_modes[4] = {0, 3, 2, 1};
417 
418 	return sprintf(buf, "%d\n", sysfs_modes[mode]);
419 }
420 
421 static ssize_t pwm1_enable_store(struct device *dev,
422 				 struct device_attribute *devattr,
423 				 const char *buf, size_t count)
424 {
425 	struct max6650_data *data = dev_get_drvdata(dev);
426 	unsigned long mode;
427 	int err;
428 	const u8 max6650_modes[] = {
429 		MAX6650_CFG_MODE_ON,
430 		MAX6650_CFG_MODE_OPEN_LOOP,
431 		MAX6650_CFG_MODE_CLOSED_LOOP,
432 		MAX6650_CFG_MODE_OFF,
433 		};
434 
435 	err = kstrtoul(buf, 10, &mode);
436 	if (err)
437 		return err;
438 
439 	if (mode >= ARRAY_SIZE(max6650_modes))
440 		return -EINVAL;
441 
442 	mutex_lock(&data->update_lock);
443 
444 	max6650_set_operating_mode(data, max6650_modes[mode]);
445 
446 	mutex_unlock(&data->update_lock);
447 
448 	return count;
449 }
450 
451 /*
452  * Read/write functions for fan1_div sysfs file. The MAX6650 has no such
453  * divider. We handle this by converting between divider and counttime:
454  *
455  * (counttime == k) <==> (divider == 2^k), k = 0, 1, 2, or 3
456  *
457  * Lower values of k allow to connect a faster fan without the risk of
458  * counter overflow. The price is lower resolution. You can also set counttime
459  * using the module parameter. Note that the module parameter "prescaler" also
460  * influences the behaviour. Unfortunately, there's no sysfs attribute
461  * defined for that. See the data sheet for details.
462  */
463 
464 static ssize_t fan1_div_show(struct device *dev,
465 			     struct device_attribute *devattr, char *buf)
466 {
467 	struct max6650_data *data = max6650_update_device(dev);
468 
469 	return sprintf(buf, "%d\n", DIV_FROM_REG(data->count));
470 }
471 
472 static ssize_t fan1_div_store(struct device *dev,
473 			      struct device_attribute *devattr,
474 			      const char *buf, size_t count)
475 {
476 	struct max6650_data *data = dev_get_drvdata(dev);
477 	struct i2c_client *client = data->client;
478 	unsigned long div;
479 	int err;
480 
481 	err = kstrtoul(buf, 10, &div);
482 	if (err)
483 		return err;
484 
485 	mutex_lock(&data->update_lock);
486 	switch (div) {
487 	case 1:
488 		data->count = 0;
489 		break;
490 	case 2:
491 		data->count = 1;
492 		break;
493 	case 4:
494 		data->count = 2;
495 		break;
496 	case 8:
497 		data->count = 3;
498 		break;
499 	default:
500 		mutex_unlock(&data->update_lock);
501 		return -EINVAL;
502 	}
503 
504 	i2c_smbus_write_byte_data(client, MAX6650_REG_COUNT, data->count);
505 	mutex_unlock(&data->update_lock);
506 
507 	return count;
508 }
509 
510 /*
511  * Get alarm stati:
512  * Possible values:
513  * 0 = no alarm
514  * 1 = alarm
515  */
516 
517 static ssize_t get_alarm(struct device *dev, struct device_attribute *devattr,
518 			 char *buf)
519 {
520 	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
521 	struct max6650_data *data = max6650_update_device(dev);
522 	struct i2c_client *client = data->client;
523 	int alarm = 0;
524 
525 	if (data->alarm & attr->index) {
526 		mutex_lock(&data->update_lock);
527 		alarm = 1;
528 		data->alarm &= ~attr->index;
529 		data->alarm |= i2c_smbus_read_byte_data(client,
530 							MAX6650_REG_ALARM);
531 		mutex_unlock(&data->update_lock);
532 	}
533 
534 	return sprintf(buf, "%d\n", alarm);
535 }
536 
537 static SENSOR_DEVICE_ATTR(fan1_input, S_IRUGO, get_fan, NULL, 0);
538 static SENSOR_DEVICE_ATTR(fan2_input, S_IRUGO, get_fan, NULL, 1);
539 static SENSOR_DEVICE_ATTR(fan3_input, S_IRUGO, get_fan, NULL, 2);
540 static SENSOR_DEVICE_ATTR(fan4_input, S_IRUGO, get_fan, NULL, 3);
541 static DEVICE_ATTR_RW(fan1_target);
542 static DEVICE_ATTR_RW(fan1_div);
543 static DEVICE_ATTR_RW(pwm1_enable);
544 static DEVICE_ATTR_RW(pwm1);
545 static SENSOR_DEVICE_ATTR(fan1_max_alarm, S_IRUGO, get_alarm, NULL,
546 			  MAX6650_ALRM_MAX);
547 static SENSOR_DEVICE_ATTR(fan1_min_alarm, S_IRUGO, get_alarm, NULL,
548 			  MAX6650_ALRM_MIN);
549 static SENSOR_DEVICE_ATTR(fan1_fault, S_IRUGO, get_alarm, NULL,
550 			  MAX6650_ALRM_TACH);
551 static SENSOR_DEVICE_ATTR(gpio1_alarm, S_IRUGO, get_alarm, NULL,
552 			  MAX6650_ALRM_GPIO1);
553 static SENSOR_DEVICE_ATTR(gpio2_alarm, S_IRUGO, get_alarm, NULL,
554 			  MAX6650_ALRM_GPIO2);
555 
556 static umode_t max6650_attrs_visible(struct kobject *kobj, struct attribute *a,
557 				    int n)
558 {
559 	struct device *dev = container_of(kobj, struct device, kobj);
560 	struct max6650_data *data = dev_get_drvdata(dev);
561 	struct i2c_client *client = data->client;
562 	u8 alarm_en = i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM_EN);
563 	struct device_attribute *devattr;
564 
565 	/*
566 	 * Hide the alarms that have not been enabled by the firmware
567 	 */
568 
569 	devattr = container_of(a, struct device_attribute, attr);
570 	if (devattr == &sensor_dev_attr_fan1_max_alarm.dev_attr
571 	 || devattr == &sensor_dev_attr_fan1_min_alarm.dev_attr
572 	 || devattr == &sensor_dev_attr_fan1_fault.dev_attr
573 	 || devattr == &sensor_dev_attr_gpio1_alarm.dev_attr
574 	 || devattr == &sensor_dev_attr_gpio2_alarm.dev_attr) {
575 		if (!(alarm_en & to_sensor_dev_attr(devattr)->index))
576 			return 0;
577 	}
578 
579 	return a->mode;
580 }
581 
582 static struct attribute *max6650_attrs[] = {
583 	&sensor_dev_attr_fan1_input.dev_attr.attr,
584 	&dev_attr_fan1_target.attr,
585 	&dev_attr_fan1_div.attr,
586 	&dev_attr_pwm1_enable.attr,
587 	&dev_attr_pwm1.attr,
588 	&sensor_dev_attr_fan1_max_alarm.dev_attr.attr,
589 	&sensor_dev_attr_fan1_min_alarm.dev_attr.attr,
590 	&sensor_dev_attr_fan1_fault.dev_attr.attr,
591 	&sensor_dev_attr_gpio1_alarm.dev_attr.attr,
592 	&sensor_dev_attr_gpio2_alarm.dev_attr.attr,
593 	NULL
594 };
595 
596 static const struct attribute_group max6650_group = {
597 	.attrs = max6650_attrs,
598 	.is_visible = max6650_attrs_visible,
599 };
600 
601 static struct attribute *max6651_attrs[] = {
602 	&sensor_dev_attr_fan2_input.dev_attr.attr,
603 	&sensor_dev_attr_fan3_input.dev_attr.attr,
604 	&sensor_dev_attr_fan4_input.dev_attr.attr,
605 	NULL
606 };
607 
608 static const struct attribute_group max6651_group = {
609 	.attrs = max6651_attrs,
610 };
611 
612 /*
613  * Real code
614  */
615 
616 static int max6650_init_client(struct max6650_data *data,
617 			       struct i2c_client *client)
618 {
619 	struct device *dev = &client->dev;
620 	int config;
621 	int err = -EIO;
622 	u32 voltage;
623 	u32 prescale;
624 	u32 target_rpm;
625 
626 	if (of_property_read_u32(dev->of_node, "maxim,fan-microvolt",
627 				 &voltage))
628 		voltage = fan_voltage;
629 	else
630 		voltage /= 1000000; /* Microvolts to volts */
631 	if (of_property_read_u32(dev->of_node, "maxim,fan-prescale",
632 				 &prescale))
633 		prescale = prescaler;
634 
635 	config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);
636 
637 	if (config < 0) {
638 		dev_err(dev, "Error reading config, aborting.\n");
639 		return err;
640 	}
641 
642 	switch (voltage) {
643 	case 0:
644 		break;
645 	case 5:
646 		config &= ~MAX6650_CFG_V12;
647 		break;
648 	case 12:
649 		config |= MAX6650_CFG_V12;
650 		break;
651 	default:
652 		dev_err(dev, "illegal value for fan_voltage (%d)\n", voltage);
653 	}
654 
655 	switch (prescale) {
656 	case 0:
657 		break;
658 	case 1:
659 		config &= ~MAX6650_CFG_PRESCALER_MASK;
660 		break;
661 	case 2:
662 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
663 			 | MAX6650_CFG_PRESCALER_2;
664 		break;
665 	case  4:
666 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
667 			 | MAX6650_CFG_PRESCALER_4;
668 		break;
669 	case  8:
670 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
671 			 | MAX6650_CFG_PRESCALER_8;
672 		break;
673 	case 16:
674 		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
675 			 | MAX6650_CFG_PRESCALER_16;
676 		break;
677 	default:
678 		dev_err(dev, "illegal value for prescaler (%d)\n", prescale);
679 	}
680 
681 	dev_info(dev, "Fan voltage: %dV, prescaler: %d.\n",
682 		 (config & MAX6650_CFG_V12) ? 12 : 5,
683 		 1 << (config & MAX6650_CFG_PRESCALER_MASK));
684 
685 	if (i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, config)) {
686 		dev_err(dev, "Config write error, aborting.\n");
687 		return err;
688 	}
689 
690 	data->config = config;
691 	data->count = i2c_smbus_read_byte_data(client, MAX6650_REG_COUNT);
692 
693 	if (!of_property_read_u32(client->dev.of_node, "maxim,fan-target-rpm",
694 				  &target_rpm)) {
695 		max6650_set_target(data, target_rpm);
696 		max6650_set_operating_mode(data, MAX6650_CFG_MODE_CLOSED_LOOP);
697 	}
698 
699 	return 0;
700 }
701 
702 static int max6650_probe(struct i2c_client *client,
703 			 const struct i2c_device_id *id)
704 {
705 	struct device *dev = &client->dev;
706 	const struct of_device_id *of_id =
707 		of_match_device(of_match_ptr(max6650_dt_match), dev);
708 	struct max6650_data *data;
709 	struct device *hwmon_dev;
710 	int err;
711 
712 	data = devm_kzalloc(dev, sizeof(struct max6650_data), GFP_KERNEL);
713 	if (!data)
714 		return -ENOMEM;
715 
716 	data->client = client;
717 	mutex_init(&data->update_lock);
718 	data->nr_fans = of_id ? (int)(uintptr_t)of_id->data : id->driver_data;
719 
720 	/*
721 	 * Initialize the max6650 chip
722 	 */
723 	err = max6650_init_client(data, client);
724 	if (err)
725 		return err;
726 
727 	data->groups[0] = &max6650_group;
728 	/* 3 additional fan inputs for the MAX6651 */
729 	if (data->nr_fans == 4)
730 		data->groups[1] = &max6651_group;
731 
732 	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
733 							   client->name, data,
734 							   data->groups);
735 	return PTR_ERR_OR_ZERO(hwmon_dev);
736 }
737 
738 static const struct i2c_device_id max6650_id[] = {
739 	{ "max6650", 1 },
740 	{ "max6651", 4 },
741 	{ }
742 };
743 MODULE_DEVICE_TABLE(i2c, max6650_id);
744 
745 static struct i2c_driver max6650_driver = {
746 	.driver = {
747 		.name	= "max6650",
748 		.of_match_table = of_match_ptr(max6650_dt_match),
749 	},
750 	.probe		= max6650_probe,
751 	.id_table	= max6650_id,
752 };
753 
754 module_i2c_driver(max6650_driver);
755 
756 MODULE_AUTHOR("Hans J. Koch");
757 MODULE_DESCRIPTION("MAX6650 sensor driver");
758 MODULE_LICENSE("GPL");
759