summaryrefslogtreecommitdiffstats
path: root/drivers/hwmon/max6650.c
blob: 4752a9ee96456eb032f12009b5ce633fad9a6287 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
/*
 * max6650.c - Part of lm_sensors, Linux kernel modules for hardware
 *             monitoring.
 *
 * (C) 2007 by Hans J. Koch <hjk@hansjkoch.de>
 *
 * based on code written by John Morris <john.morris@spirentcom.com>
 * Copyright (c) 2003 Spirent Communications
 * and Claus Gindhart <claus.gindhart@kontron.com>
 *
 * This module has only been tested with the MAX6650 chip. It should
 * also work with the MAX6651. It does not distinguish max6650 and max6651
 * chips.
 *
 * The datasheet was last seen at:
 *
 *        http://pdfserv.maxim-ic.com/en/ds/MAX6650-MAX6651.pdf
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/jiffies.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/err.h>
#include <linux/of_device.h>

/*
 * Insmod parameters
 */

/* fan_voltage: 5=5V fan, 12=12V fan, 0=don't change */
static int fan_voltage;
/* prescaler: Possible values are 1, 2, 4, 8, 16 or 0 for don't change */
static int prescaler;
/* clock: The clock frequency of the chip (max6651 can be clocked externally) */
static int clock = 254000;

module_param(fan_voltage, int, S_IRUGO);
module_param(prescaler, int, S_IRUGO);
module_param(clock, int, S_IRUGO);

/*
 * MAX 6650/6651 registers
 */

#define MAX6650_REG_SPEED	0x00
#define MAX6650_REG_CONFIG	0x02
#define MAX6650_REG_GPIO_DEF	0x04
#define MAX6650_REG_DAC		0x06
#define MAX6650_REG_ALARM_EN	0x08
#define MAX6650_REG_ALARM	0x0A
#define MAX6650_REG_TACH0	0x0C
#define MAX6650_REG_TACH1	0x0E
#define MAX6650_REG_TACH2	0x10
#define MAX6650_REG_TACH3	0x12
#define MAX6650_REG_GPIO_STAT	0x14
#define MAX6650_REG_COUNT	0x16

/*
 * Config register bits
 */

#define MAX6650_CFG_V12			0x08
#define MAX6650_CFG_PRESCALER_MASK	0x07
#define MAX6650_CFG_PRESCALER_2		0x01
#define MAX6650_CFG_PRESCALER_4		0x02
#define MAX6650_CFG_PRESCALER_8		0x03
#define MAX6650_CFG_PRESCALER_16	0x04
#define MAX6650_CFG_MODE_MASK		0x30
#define MAX6650_CFG_MODE_ON		0x00
#define MAX6650_CFG_MODE_OFF		0x10
#define MAX6650_CFG_MODE_CLOSED_LOOP	0x20
#define MAX6650_CFG_MODE_OPEN_LOOP	0x30
#define MAX6650_COUNT_MASK		0x03

/*
 * Alarm status register bits
 */

#define MAX6650_ALRM_MAX	0x01
#define MAX6650_ALRM_MIN	0x02
#define MAX6650_ALRM_TACH	0x04
#define MAX6650_ALRM_GPIO1	0x08
#define MAX6650_ALRM_GPIO2	0x10

/* Minimum and maximum values of the FAN-RPM */
#define FAN_RPM_MIN 240
#define FAN_RPM_MAX 30000

#define DIV_FROM_REG(reg) (1 << (reg & 7))

/*
 * Client data (each client gets its own)
 */

struct max6650_data {
	struct i2c_client *client;
	const struct attribute_group *groups[3];
	struct mutex update_lock;
	int nr_fans;
	char valid; /* zero until following fields are valid */
	unsigned long last_updated; /* in jiffies */

	/* register values */
	u8 speed;
	u8 config;
	u8 tach[4];
	u8 count;
	u8 dac;
	u8 alarm;
};

static const u8 tach_reg[] = {
	MAX6650_REG_TACH0,
	MAX6650_REG_TACH1,
	MAX6650_REG_TACH2,
	MAX6650_REG_TACH3,
};

static const struct of_device_id max6650_dt_match[] = {
	{
		.compatible = "maxim,max6650",
		.data = (void *)1
	},
	{
		.compatible = "maxim,max6651",
		.data = (void *)4
	},
	{ },
};
MODULE_DEVICE_TABLE(of, max6650_dt_match);

static struct max6650_data *max6650_update_device(struct device *dev)
{
	struct max6650_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	int i;

	mutex_lock(&data->update_lock);

	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
		data->speed = i2c_smbus_read_byte_data(client,
						       MAX6650_REG_SPEED);
		data->config = i2c_smbus_read_byte_data(client,
							MAX6650_REG_CONFIG);
		for (i = 0; i < data->nr_fans; i++) {
			data->tach[i] = i2c_smbus_read_byte_data(client,
								 tach_reg[i]);
		}
		data->count = i2c_smbus_read_byte_data(client,
							MAX6650_REG_COUNT);
		data->dac = i2c_smbus_read_byte_data(client, MAX6650_REG_DAC);

		/*
		 * Alarms are cleared on read in case the condition that
		 * caused the alarm is removed. Keep the value latched here
		 * for providing the register through different alarm files.
		 */
		data->alarm |= i2c_smbus_read_byte_data(client,
							MAX6650_REG_ALARM);

		data->last_updated = jiffies;
		data->valid = 1;
	}

	mutex_unlock(&data->update_lock);

	return data;
}

/*
 * Change the operating mode of the chip (if needed).
 * mode is one of the MAX6650_CFG_MODE_* values.
 */
static int max6650_set_operating_mode(struct max6650_data *data, u8 mode)
{
	int result;
	u8 config = data->config;

	if (mode == (config & MAX6650_CFG_MODE_MASK))
		return 0;

	config = (config & ~MAX6650_CFG_MODE_MASK) | mode;

	result = i2c_smbus_write_byte_data(data->client, MAX6650_REG_CONFIG,
					   config);
	if (result < 0)
		return result;

	data->config = config;

	return 0;
}

static ssize_t fan_show(struct device *dev, struct device_attribute *devattr,
			char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
	struct max6650_data *data = max6650_update_device(dev);
	int rpm;

	/*
	 * Calculation details:
	 *
	 * Each tachometer counts over an interval given by the "count"
	 * register (0.25, 0.5, 1 or 2 seconds). This module assumes
	 * that the fans produce two pulses per revolution (this seems
	 * to be the most common).
	 */

	rpm = ((data->tach[attr->index] * 120) / DIV_FROM_REG(data->count));
	return sprintf(buf, "%d\n", rpm);
}

/*
 * Set the fan speed to the specified RPM (or read back the RPM setting).
 * This works in closed loop mode only. Use pwm1 for open loop speed setting.
 *
 * The MAX6650/1 will automatically control fan speed when in closed loop
 * mode.
 *
 * Assumptions:
 *
 * 1) The MAX6650/1 internal 254kHz clock frequency is set correctly. Use
 *    the clock module parameter if you need to fine tune this.
 *
 * 2) The prescaler (low three bits of the config register) has already
 *    been set to an appropriate value. Use the prescaler module parameter
 *    if your BIOS doesn't initialize the chip properly.
 *
 * The relevant equations are given on pages 21 and 22 of the datasheet.
 *
 * From the datasheet, the relevant equation when in regulation is:
 *
 *    [fCLK / (128 x (KTACH + 1))] = 2 x FanSpeed / KSCALE
 *
 * where:
 *
 *    fCLK is the oscillator frequency (either the 254kHz internal
 *         oscillator or the externally applied clock)
 *
 *    KTACH is the value in the speed register
 *
 *    FanSpeed is the speed of the fan in rps
 *
 *    KSCALE is the prescaler value (1, 2, 4, 8, or 16)
 *
 * When reading, we need to solve for FanSpeed. When writing, we need to
 * solve for KTACH.
 *
 * Note: this tachometer is completely separate from the tachometers
 * used to measure the fan speeds. Only one fan's speed (fan1) is
 * controlled.
 */

static ssize_t fan1_target_show(struct device *dev,
				struct device_attribute *devattr, char *buf)
{
	struct max6650_data *data = max6650_update_device(dev);
	int kscale, ktach, rpm;

	/*
	 * Use the datasheet equation:
	 *
	 *    FanSpeed = KSCALE x fCLK / [256 x (KTACH + 1)]
	 *
	 * then multiply by 60 to give rpm.
	 */

	kscale = DIV_FROM_REG(data->config);
	ktach = data->speed;
	rpm = 60 * kscale * clock / (256 * (ktach + 1));
	return sprintf(buf, "%d\n", rpm);
}

static int max6650_set_target(struct max6650_data *data, unsigned long rpm)
{
	int kscale, ktach;

	if (rpm == 0)
		return max6650_set_operating_mode(data, MAX6650_CFG_MODE_OFF);

	rpm = clamp_val(rpm, FAN_RPM_MIN, FAN_RPM_MAX);

	/*
	 * Divide the required speed by 60 to get from rpm to rps, then
	 * use the datasheet equation:
	 *
	 *     KTACH = [(fCLK x KSCALE) / (256 x FanSpeed)] - 1
	 */

	kscale = DIV_FROM_REG(data->config);
	ktach = ((clock * kscale) / (256 * rpm / 60)) - 1;
	if (ktach < 0)
		ktach = 0;
	if (ktach > 255)
		ktach = 255;
	data->speed = ktach;

	return i2c_smbus_write_byte_data(data->client, MAX6650_REG_SPEED,
					 data->speed);
}

static ssize_t fan1_target_store(struct device *dev,
				 struct device_attribute *devattr,
				 const char *buf, size_t count)
{
	struct max6650_data *data = dev_get_drvdata(dev);
	unsigned long rpm;
	int err;

	err = kstrtoul(buf, 10, &rpm);
	if (err)
		return err;

	mutex_lock(&data->update_lock);

	err = max6650_set_target(data, rpm);

	mutex_unlock(&data->update_lock);

	if (err < 0)
		return err;

	return count;
}

/*
 * Get/set the fan speed in open loop mode using pwm1 sysfs file.
 * Speed is given as a relative value from 0 to 255, where 255 is maximum
 * speed. Note that this is done by writing directly to the chip's DAC,
 * it won't change the closed loop speed set by fan1_target.
 * Also note that due to rounding errors it is possible that you don't read
 * back exactly the value you have set.
 */

static ssize_t pwm1_show(struct device *dev, struct device_attribute *devattr,
			 char *buf)
{
	int pwm;
	struct max6650_data *data = max6650_update_device(dev);

	/*
	 * Useful range for dac is 0-180 for 12V fans and 0-76 for 5V fans.
	 * Lower DAC values mean higher speeds.
	 */
	if (data->config & MAX6650_CFG_V12)
		pwm = 255 - (255 * (int)data->dac)/180;
	else
		pwm = 255 - (255 * (int)data->dac)/76;

	if (pwm < 0)
		pwm = 0;

	return sprintf(buf, "%d\n", pwm);
}

static ssize_t pwm1_store(struct device *dev,
			  struct device_attribute *devattr, const char *buf,
			  size_t count)
{
	struct max6650_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	unsigned long pwm;
	int err;

	err = kstrtoul(buf, 10, &pwm);
	if (err)
		return err;

	pwm = clamp_val(pwm, 0, 255);

	mutex_lock(&data->update_lock);

	if (data->config & MAX6650_CFG_V12)
		data->dac = 180 - (180 * pwm)/255;
	else
		data->dac = 76 - (76 * pwm)/255;
	err = i2c_smbus_write_byte_data(client, MAX6650_REG_DAC, data->dac);

	mutex_unlock(&data->update_lock);

	return err < 0 ? err : count;
}

/*
 * Get/Set controller mode:
 * Possible values:
 * 0 = Fan always on
 * 1 = Open loop, Voltage is set according to speed, not regulated.
 * 2 = Closed loop, RPM for all fans regulated by fan1 tachometer
 * 3 = Fan off
 */
static ssize_t pwm1_enable_show(struct device *dev,
				struct device_attribute *devattr, char *buf)
{
	struct max6650_data *data = max6650_update_device(dev);
	int mode = (data->config & MAX6650_CFG_MODE_MASK) >> 4;
	int sysfs_modes[4] = {0, 3, 2, 1};

	return sprintf(buf, "%d\n", sysfs_modes[mode]);
}

static ssize_t pwm1_enable_store(struct device *dev,
				 struct device_attribute *devattr,
				 const char *buf, size_t count)
{
	struct max6650_data *data = dev_get_drvdata(dev);
	unsigned long mode;
	int err;
	const u8 max6650_modes[] = {
		MAX6650_CFG_MODE_ON,
		MAX6650_CFG_MODE_OPEN_LOOP,
		MAX6650_CFG_MODE_CLOSED_LOOP,
		MAX6650_CFG_MODE_OFF,
		};

	err = kstrtoul(buf, 10, &mode);
	if (err)
		return err;

	if (mode >= ARRAY_SIZE(max6650_modes))
		return -EINVAL;

	mutex_lock(&data->update_lock);

	max6650_set_operating_mode(data, max6650_modes[mode]);

	mutex_unlock(&data->update_lock);

	return count;
}

/*
 * Read/write functions for fan1_div sysfs file. The MAX6650 has no such
 * divider. We handle this by converting between divider and counttime:
 *
 * (counttime == k) <==> (divider == 2^k), k = 0, 1, 2, or 3
 *
 * Lower values of k allow to connect a faster fan without the risk of
 * counter overflow. The price is lower resolution. You can also set counttime
 * using the module parameter. Note that the module parameter "prescaler" also
 * influences the behaviour. Unfortunately, there's no sysfs attribute
 * defined for that. See the data sheet for details.
 */

static ssize_t fan1_div_show(struct device *dev,
			     struct device_attribute *devattr, char *buf)
{
	struct max6650_data *data = max6650_update_device(dev);

	return sprintf(buf, "%d\n", DIV_FROM_REG(data->count));
}

static ssize_t fan1_div_store(struct device *dev,
			      struct device_attribute *devattr,
			      const char *buf, size_t count)
{
	struct max6650_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	unsigned long div;
	int err;

	err = kstrtoul(buf, 10, &div);
	if (err)
		return err;

	mutex_lock(&data->update_lock);
	switch (div) {
	case 1:
		data->count = 0;
		break;
	case 2:
		data->count = 1;
		break;
	case 4:
		data->count = 2;
		break;
	case 8:
		data->count = 3;
		break;
	default:
		mutex_unlock(&data->update_lock);
		return -EINVAL;
	}

	i2c_smbus_write_byte_data(client, MAX6650_REG_COUNT, data->count);
	mutex_unlock(&data->update_lock);

	return count;
}

/*
 * Get alarm stati:
 * Possible values:
 * 0 = no alarm
 * 1 = alarm
 */

static ssize_t alarm_show(struct device *dev,
			  struct device_attribute *devattr, char *buf)
{
	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
	struct max6650_data *data = max6650_update_device(dev);
	struct i2c_client *client = data->client;
	int alarm = 0;

	if (data->alarm & attr->index) {
		mutex_lock(&data->update_lock);
		alarm = 1;
		data->alarm &= ~attr->index;
		data->alarm |= i2c_smbus_read_byte_data(client,
							MAX6650_REG_ALARM);
		mutex_unlock(&data->update_lock);
	}

	return sprintf(buf, "%d\n", alarm);
}

static SENSOR_DEVICE_ATTR_RO(fan1_input, fan, 0);
static SENSOR_DEVICE_ATTR_RO(fan2_input, fan, 1);
static SENSOR_DEVICE_ATTR_RO(fan3_input, fan, 2);
static SENSOR_DEVICE_ATTR_RO(fan4_input, fan, 3);
static DEVICE_ATTR_RW(fan1_target);
static DEVICE_ATTR_RW(fan1_div);
static DEVICE_ATTR_RW(pwm1_enable);
static DEVICE_ATTR_RW(pwm1);
static SENSOR_DEVICE_ATTR_RO(fan1_max_alarm, alarm, MAX6650_ALRM_MAX);
static SENSOR_DEVICE_ATTR_RO(fan1_min_alarm, alarm, MAX6650_ALRM_MIN);
static SENSOR_DEVICE_ATTR_RO(fan1_fault, alarm, MAX6650_ALRM_TACH);
static SENSOR_DEVICE_ATTR_RO(gpio1_alarm, alarm, MAX6650_ALRM_GPIO1);
static SENSOR_DEVICE_ATTR_RO(gpio2_alarm, alarm, MAX6650_ALRM_GPIO2);

static umode_t max6650_attrs_visible(struct kobject *kobj, struct attribute *a,
				    int n)
{
	struct device *dev = container_of(kobj, struct device, kobj);
	struct max6650_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	u8 alarm_en = i2c_smbus_read_byte_data(client, MAX6650_REG_ALARM_EN);
	struct device_attribute *devattr;

	/*
	 * Hide the alarms that have not been enabled by the firmware
	 */

	devattr = container_of(a, struct device_attribute, attr);
	if (devattr == &sensor_dev_attr_fan1_max_alarm.dev_attr
	 || devattr == &sensor_dev_attr_fan1_min_alarm.dev_attr
	 || devattr == &sensor_dev_attr_fan1_fault.dev_attr
	 || devattr == &sensor_dev_attr_gpio1_alarm.dev_attr
	 || devattr == &sensor_dev_attr_gpio2_alarm.dev_attr) {
		if (!(alarm_en & to_sensor_dev_attr(devattr)->index))
			return 0;
	}

	return a->mode;
}

static struct attribute *max6650_attrs[] = {
	&sensor_dev_attr_fan1_input.dev_attr.attr,
	&dev_attr_fan1_target.attr,
	&dev_attr_fan1_div.attr,
	&dev_attr_pwm1_enable.attr,
	&dev_attr_pwm1.attr,
	&sensor_dev_attr_fan1_max_alarm.dev_attr.attr,
	&sensor_dev_attr_fan1_min_alarm.dev_attr.attr,
	&sensor_dev_attr_fan1_fault.dev_attr.attr,
	&sensor_dev_attr_gpio1_alarm.dev_attr.attr,
	&sensor_dev_attr_gpio2_alarm.dev_attr.attr,
	NULL
};

static const struct attribute_group max6650_group = {
	.attrs = max6650_attrs,
	.is_visible = max6650_attrs_visible,
};

static struct attribute *max6651_attrs[] = {
	&sensor_dev_attr_fan2_input.dev_attr.attr,
	&sensor_dev_attr_fan3_input.dev_attr.attr,
	&sensor_dev_attr_fan4_input.dev_attr.attr,
	NULL
};

static const struct attribute_group max6651_group = {
	.attrs = max6651_attrs,
};

/*
 * Real code
 */

static int max6650_init_client(struct max6650_data *data,
			       struct i2c_client *client)
{
	struct device *dev = &client->dev;
	int config;
	int err = -EIO;
	u32 voltage;
	u32 prescale;
	u32 target_rpm;

	if (of_property_read_u32(dev->of_node, "maxim,fan-microvolt",
				 &voltage))
		voltage = fan_voltage;
	else
		voltage /= 1000000; /* Microvolts to volts */
	if (of_property_read_u32(dev->of_node, "maxim,fan-prescale",
				 &prescale))
		prescale = prescaler;

	config = i2c_smbus_read_byte_data(client, MAX6650_REG_CONFIG);

	if (config < 0) {
		dev_err(dev, "Error reading config, aborting.\n");
		return err;
	}

	switch (voltage) {
	case 0:
		break;
	case 5:
		config &= ~MAX6650_CFG_V12;
		break;
	case 12:
		config |= MAX6650_CFG_V12;
		break;
	default:
		dev_err(dev, "illegal value for fan_voltage (%d)\n", voltage);
	}

	switch (prescale) {
	case 0:
		break;
	case 1:
		config &= ~MAX6650_CFG_PRESCALER_MASK;
		break;
	case 2:
		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
			 | MAX6650_CFG_PRESCALER_2;
		break;
	case  4:
		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
			 | MAX6650_CFG_PRESCALER_4;
		break;
	case  8:
		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
			 | MAX6650_CFG_PRESCALER_8;
		break;
	case 16:
		config = (config & ~MAX6650_CFG_PRESCALER_MASK)
			 | MAX6650_CFG_PRESCALER_16;
		break;
	default:
		dev_err(dev, "illegal value for prescaler (%d)\n", prescale);
	}

	dev_info(dev, "Fan voltage: %dV, prescaler: %d.\n",
		 (config & MAX6650_CFG_V12) ? 12 : 5,
		 1 << (config & MAX6650_CFG_PRESCALER_MASK));

	if (i2c_smbus_write_byte_data(client, MAX6650_REG_CONFIG, config)) {
		dev_err(dev, "Config write error, aborting.\n");
		return err;
	}

	data->config = config;
	data->count = i2c_smbus_read_byte_data(client, MAX6650_REG_COUNT);

	if (!of_property_read_u32(client->dev.of_node, "maxim,fan-target-rpm",
				  &target_rpm)) {
		max6650_set_target(data, target_rpm);
		max6650_set_operating_mode(data, MAX6650_CFG_MODE_CLOSED_LOOP);
	}

	return 0;
}

static int max6650_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	struct device *dev = &client->dev;
	const struct of_device_id *of_id =
		of_match_device(of_match_ptr(max6650_dt_match), dev);
	struct max6650_data *data;
	struct device *hwmon_dev;
	int err;

	data = devm_kzalloc(dev, sizeof(struct max6650_data), GFP_KERNEL);
	if (!data)
		return -ENOMEM;

	data->client = client;
	mutex_init(&data->update_lock);
	data->nr_fans = of_id ? (int)(uintptr_t)of_id->data : id->driver_data;

	/*
	 * Initialize the max6650 chip
	 */
	err = max6650_init_client(data, client);
	if (err)
		return err;

	data->groups[0] = &max6650_group;
	/* 3 additional fan inputs for the MAX6651 */
	if (data->nr_fans == 4)
		data->groups[1] = &max6651_group;

	hwmon_dev = devm_hwmon_device_register_with_groups(dev,
							   client->name, data,
							   data->groups);
	return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id max6650_id[] = {
	{ "max6650", 1 },
	{ "max6651", 4 },
	{ }
};
MODULE_DEVICE_TABLE(i2c, max6650_id);

static struct i2c_driver max6650_driver = {
	.driver = {
		.name	= "max6650",
		.of_match_table = of_match_ptr(max6650_dt_match),
	},
	.probe		= max6650_probe,
	.id_table	= max6650_id,
};

module_i2c_driver(max6650_driver);

MODULE_AUTHOR("Hans J. Koch");
MODULE_DESCRIPTION("MAX6650 sensor driver");
MODULE_LICENSE("GPL");