drivers/hwmon/max6620.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * Hardware monitoring driver for Maxim MAX6620
  *
  * Originally from L. Grunenberg.
  * (C) 2012 by L. Grunenberg <contact@lgrunenberg.de>
  *
  * Copyright (c) 2021 Dell Inc. or its subsidiaries. All Rights Reserved.
  *
  * based on code written by :
  * 2007 by Hans J. Koch <hjk@hansjkoch.de>
  * 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 MAX6620 chip.
  *
  * The datasheet was last seen at:
  *
  *        http://pdfserv.maxim-ic.com/en/ds/MAX6620.pdf
  *
  */

 #include <linux/bits.h>
 #include <linux/err.h>
 #include <linux/hwmon.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/jiffies.h>
 #include <linux/module.h>
 #include <linux/slab.h>

 /*
  * MAX 6620 registers
  */

 #define MAX6620_REG_CONFIG	0x00
 #define MAX6620_REG_FAULT	0x01
 #define MAX6620_REG_CONF_FAN0	0x02
 #define MAX6620_REG_CONF_FAN1	0x03
 #define MAX6620_REG_CONF_FAN2	0x04
 #define MAX6620_REG_CONF_FAN3	0x05
 #define MAX6620_REG_DYN_FAN0	0x06
 #define MAX6620_REG_DYN_FAN1	0x07
 #define MAX6620_REG_DYN_FAN2	0x08
 #define MAX6620_REG_DYN_FAN3	0x09
 #define MAX6620_REG_TACH0	0x10
 #define MAX6620_REG_TACH1	0x12
 #define MAX6620_REG_TACH2	0x14
 #define MAX6620_REG_TACH3	0x16
 #define MAX6620_REG_VOLT0	0x18
 #define MAX6620_REG_VOLT1	0x1A
 #define MAX6620_REG_VOLT2	0x1C
 #define MAX6620_REG_VOLT3	0x1E
 #define MAX6620_REG_TAR0	0x20
 #define MAX6620_REG_TAR1	0x22
 #define MAX6620_REG_TAR2	0x24
 #define MAX6620_REG_TAR3	0x26
 #define MAX6620_REG_DAC0	0x28
 #define MAX6620_REG_DAC1	0x2A
 #define MAX6620_REG_DAC2	0x2C
 #define MAX6620_REG_DAC3	0x2E

 /*
  * Config register bits
  */

 #define MAX6620_CFG_RUN		BIT(7)
 #define MAX6620_CFG_POR		BIT(6)
 #define MAX6620_CFG_TIMEOUT	BIT(5)
 #define MAX6620_CFG_FULLFAN	BIT(4)
 #define MAX6620_CFG_OSC		BIT(3)
 #define MAX6620_CFG_WD_MASK	(BIT(2) | BIT(1))
 #define MAX6620_CFG_WD_2	BIT(1)
 #define MAX6620_CFG_WD_6	BIT(2)
 #define MAX6620_CFG_WD10	(BIT(2) | BIT(1))
 #define MAX6620_CFG_WD		BIT(0)

 /*
  * Failure status register bits
  */

 #define MAX6620_FAIL_TACH0	BIT(4)
 #define MAX6620_FAIL_TACH1	BIT(5)
 #define MAX6620_FAIL_TACH2	BIT(6)
 #define MAX6620_FAIL_TACH3	BIT(7)
 #define MAX6620_FAIL_MASK0	BIT(0)
 #define MAX6620_FAIL_MASK1	BIT(1)
 #define MAX6620_FAIL_MASK2	BIT(2)
 #define MAX6620_FAIL_MASK3	BIT(3)

 #define MAX6620_CLOCK_FREQ	8192 /* Clock frequency in Hz */
 #define MAX6620_PULSE_PER_REV	2 /* Tachometer pulses per revolution */

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

 static const u8 config_reg[] = {
 	MAX6620_REG_CONF_FAN0,
 	MAX6620_REG_CONF_FAN1,
 	MAX6620_REG_CONF_FAN2,
 	MAX6620_REG_CONF_FAN3,
 };

 static const u8 dyn_reg[] = {
 	MAX6620_REG_DYN_FAN0,
 	MAX6620_REG_DYN_FAN1,
 	MAX6620_REG_DYN_FAN2,
 	MAX6620_REG_DYN_FAN3,
 };

 static const u8 tach_reg[] = {
 	MAX6620_REG_TACH0,
 	MAX6620_REG_TACH1,
 	MAX6620_REG_TACH2,
 	MAX6620_REG_TACH3,
 };

 static const u8 target_reg[] = {
 	MAX6620_REG_TAR0,
 	MAX6620_REG_TAR1,
 	MAX6620_REG_TAR2,
 	MAX6620_REG_TAR3,
 };

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

 struct max6620_data {
 	struct i2c_client *client;
 	struct mutex update_lock;
 	bool valid; /* false until following fields are valid */
 	unsigned long last_updated; /* in jiffies */

 	/* register values */
 	u8 fancfg[4];
 	u8 fandyn[4];
 	u8 fault;
 	u16 tach[4];
 	u16 target[4];
 };

 static u8 max6620_fan_div_from_reg(u8 val)
 {
 	return BIT((val & 0xE0) >> 5);
 }

 static u16 max6620_fan_rpm_to_tach(u8 div, int rpm)
 {
 	return (60 * div * MAX6620_CLOCK_FREQ) / (rpm * MAX6620_PULSE_PER_REV);
 }

 static int max6620_fan_tach_to_rpm(u8 div, u16 tach)
 {
 	return (60 * div * MAX6620_CLOCK_FREQ) / (tach * MAX6620_PULSE_PER_REV);
 }

 static int max6620_update_device(struct device *dev)
 {
 	struct max6620_data *data = dev_get_drvdata(dev);
 	struct i2c_client *client = data->client;
 	int i;
 	int ret = 0;

 	mutex_lock(&data->update_lock);

 	if (time_after(jiffies, data->last_updated + HZ) || !data->valid) {
 		for (i = 0; i < 4; i++) {
 			ret = i2c_smbus_read_byte_data(client, config_reg[i]);
 			if (ret < 0)
 				goto error;
 			data->fancfg[i] = ret;

 			ret = i2c_smbus_read_byte_data(client, dyn_reg[i]);
 			if (ret < 0)
 				goto error;
 			data->fandyn[i] = ret;

 			ret = i2c_smbus_read_byte_data(client, tach_reg[i]);
 			if (ret < 0)
 				goto error;
 			data->tach[i] = (ret << 3) & 0x7f8;
 			ret = i2c_smbus_read_byte_data(client, tach_reg[i] + 1);
 			if (ret < 0)
 				goto error;
 			data->tach[i] |= (ret >> 5) & 0x7;

 			ret = i2c_smbus_read_byte_data(client, target_reg[i]);
 			if (ret < 0)
 				goto error;
 			data->target[i] = (ret << 3) & 0x7f8;
 			ret = i2c_smbus_read_byte_data(client, target_reg[i] + 1);
 			if (ret < 0)
 				goto error;
 			data->target[i] |= (ret >> 5) & 0x7;
 		}

 		/*
 		 * 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.
 		 */
 		ret = i2c_smbus_read_byte_data(client, MAX6620_REG_FAULT);
 		if (ret < 0)
 			goto error;
 		data->fault |= (ret >> 4) & (ret & 0x0F);

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

 error:
 	mutex_unlock(&data->update_lock);
 	return ret;
 }

 static umode_t
 max6620_is_visible(const void *data, enum hwmon_sensor_types type, u32 attr,
 		   int channel)
 {
 	switch (type) {
 	case hwmon_fan:
 		switch (attr) {
 		case hwmon_fan_alarm:
 		case hwmon_fan_input:
 			return 0444;
 		case hwmon_fan_div:
 		case hwmon_fan_target:
 			return 0644;
 		default:
 			break;
 		}
 		break;
 	default:
 		break;
 	}

 	return 0;
 }

 static int
 max6620_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
 	     int channel, long *val)
 {
 	struct max6620_data *data;
 	struct i2c_client *client;
 	int ret;
 	u8 div;
 	u8 val1;
 	u8 val2;

 	ret = max6620_update_device(dev);
 	if (ret < 0)
 		return ret;
 	data = dev_get_drvdata(dev);
 	client = data->client;

 	switch (type) {
 	case hwmon_fan:
 		switch (attr) {
 		case hwmon_fan_alarm:
 			mutex_lock(&data->update_lock);
 			*val = !!(data->fault & BIT(channel));

 			/* Setting TACH count to re-enable fan fault detection */
 			if (*val == 1) {
 				val1 = (data->target[channel] >> 3) & 0xff;
 				val2 = (data->target[channel] << 5) & 0xe0;
 				ret = i2c_smbus_write_byte_data(client,
 								target_reg[channel], val1);
 				if (ret < 0) {
 					mutex_unlock(&data->update_lock);
 					return ret;
 				}
 				ret = i2c_smbus_write_byte_data(client,
 								target_reg[channel] + 1, val2);
 				if (ret < 0) {
 					mutex_unlock(&data->update_lock);
 					return ret;
 				}

 				data->fault &= ~BIT(channel);
 			}
 			mutex_unlock(&data->update_lock);

 			break;
 		case hwmon_fan_div:
 			*val = max6620_fan_div_from_reg(data->fandyn[channel]);
 			break;
 		case hwmon_fan_input:
 			if (data->tach[channel] == 0) {
 				*val = 0;
 			} else {
 				div = max6620_fan_div_from_reg(data->fandyn[channel]);
 				*val = max6620_fan_tach_to_rpm(div, data->tach[channel]);
 			}
 			break;
 		case hwmon_fan_target:
 			if (data->target[channel] == 0) {
 				*val = 0;
 			} else {
 				div = max6620_fan_div_from_reg(data->fandyn[channel]);
 				*val = max6620_fan_tach_to_rpm(div, data->target[channel]);
 			}
 			break;
 		default:
 			return -EOPNOTSUPP;
 		}
 		break;

 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static int
 max6620_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
 	      int channel, long val)
 {
 	struct max6620_data *data;
 	struct i2c_client *client;
 	int ret;
 	u8 div;
 	u16 tach;
 	u8 val1;
 	u8 val2;

 	ret = max6620_update_device(dev);
 	if (ret < 0)
 		return ret;
 	data = dev_get_drvdata(dev);
 	client = data->client;
 	mutex_lock(&data->update_lock);

 	switch (type) {
 	case hwmon_fan:
 		switch (attr) {
 		case hwmon_fan_div:
 			switch (val) {
 			case 1:
 				div = 0;
 				break;
 			case 2:
 				div = 1;
 				break;
 			case 4:
 				div = 2;
 				break;
 			case 8:
 				div = 3;
 				break;
 			case 16:
 				div = 4;
 				break;
 			case 32:
 				div = 5;
 				break;
 			default:
 				ret = -EINVAL;
 				goto error;
 			}
 			data->fandyn[channel] &= 0x1F;
 			data->fandyn[channel] |= div << 5;
 			ret = i2c_smbus_write_byte_data(client, dyn_reg[channel],
 							data->fandyn[channel]);
 			break;
 		case hwmon_fan_target:
 			val = clamp_val(val, FAN_RPM_MIN, FAN_RPM_MAX);
 			div = max6620_fan_div_from_reg(data->fandyn[channel]);
 			tach = max6620_fan_rpm_to_tach(div, val);
 			val1 = (tach >> 3) & 0xff;
 			val2 = (tach << 5) & 0xe0;
 			ret = i2c_smbus_write_byte_data(client, target_reg[channel], val1);
 			if (ret < 0)
 				break;
 			ret = i2c_smbus_write_byte_data(client, target_reg[channel] + 1, val2);
 			if (ret < 0)
 				break;

 			/* Setting TACH count re-enables fan fault detection */
 			data->fault &= ~BIT(channel);

 			break;
 		default:
 			ret = -EOPNOTSUPP;
 			break;
 		}
 		break;

 	default:
 		ret = -EOPNOTSUPP;
 		break;
 	}

 error:
 	mutex_unlock(&data->update_lock);
 	return ret;
 }

 static const struct hwmon_channel_info * const max6620_info[] = {
 	HWMON_CHANNEL_INFO(fan,
 			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_TARGET | HWMON_F_ALARM,
 			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_TARGET | HWMON_F_ALARM,
 			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_TARGET | HWMON_F_ALARM,
 			   HWMON_F_INPUT | HWMON_F_DIV | HWMON_F_TARGET | HWMON_F_ALARM),
 	NULL
 };

 static const struct hwmon_ops max6620_hwmon_ops = {
 	.read = max6620_read,
 	.write = max6620_write,
 	.is_visible = max6620_is_visible,
 };

 static const struct hwmon_chip_info max6620_chip_info = {
 	.ops = &max6620_hwmon_ops,
 	.info = max6620_info,
 };

 static int max6620_init_client(struct max6620_data *data)
 {
 	struct i2c_client *client = data->client;
 	int config;
 	int err;
 	int i;
 	int reg;

 	config = i2c_smbus_read_byte_data(client, MAX6620_REG_CONFIG);
 	if (config < 0) {
 		dev_err(&client->dev, "Error reading config, aborting.\n");
 		return config;
 	}

 	/*
 	 * Set bit 4, disable other fans from going full speed on a fail
 	 * failure.
 	 */
 	err = i2c_smbus_write_byte_data(client, MAX6620_REG_CONFIG, config | 0x10);
 	if (err < 0) {
 		dev_err(&client->dev, "Config write error, aborting.\n");
 		return err;
 	}

 	for (i = 0; i < 4; i++) {
 		reg = i2c_smbus_read_byte_data(client, config_reg[i]);
 		if (reg < 0)
 			return reg;
 		data->fancfg[i] = reg;

 		/* Enable RPM mode */
 		data->fancfg[i] |= 0xa8;
 		err = i2c_smbus_write_byte_data(client, config_reg[i], data->fancfg[i]);
 		if (err < 0)
 			return err;

 		/* 2 counts (001) and Rate change 100 (0.125 secs) */
 		data->fandyn[i] = 0x30;
 		err = i2c_smbus_write_byte_data(client, dyn_reg[i], data->fandyn[i]);
 		if (err < 0)
 			return err;
 	}
 	return 0;
 }

 static int max6620_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
 	struct max6620_data *data;
 	struct device *hwmon_dev;
 	int err;

 	data = devm_kzalloc(dev, sizeof(struct max6620_data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;

 	data->client = client;
 	mutex_init(&data->update_lock);

 	err = max6620_init_client(data);
 	if (err)
 		return err;

 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
 							 data,
 							 &max6620_chip_info,
 							 NULL);

 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }

 static const struct i2c_device_id max6620_id[] = {
 	{ "max6620" },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, max6620_id);

 static struct i2c_driver max6620_driver = {
 	.class		= I2C_CLASS_HWMON,
 	.driver = {
 		.name	= "max6620",
 	},
 	.probe		= max6620_probe,
 	.id_table	= max6620_id,
 };

 module_i2c_driver(max6620_driver);

 MODULE_AUTHOR("Lucas Grunenberg");
 MODULE_DESCRIPTION("MAX6620 sensor driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* Hardware monitoring driver for Maxim MAX6620
	*
	* Originally from L. Grunenberg.
	* (C) 2012 by L. Grunenberg <contact@lgrunenberg.de>
	*
	* Copyright (c) 2021 Dell Inc. or its subsidiaries. All Rights Reserved.
	*
	* based on code written by :
	* 2007 by Hans J. Koch <hjk@hansjkoch.de>
	* 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 MAX6620 chip.
	*
	* The datasheet was last seen at:
	*
	* http://pdfserv.maxim-ic.com/en/ds/MAX6620.pdf
	*
	*/

	#include <linux/bits.h>
	#include <linux/err.h>
	#include <linux/hwmon.h>
	#include <linux/i2c.h>
	#include <linux/init.h>
	#include <linux/jiffies.h>
	#include <linux/module.h>
	#include <linux/slab.h>

	/*
	* MAX 6620 registers
	*/

	#define MAX6620_REG_CONFIG 0x00
	#define MAX6620_REG_FAULT 0x01
	#define MAX6620_REG_CONF_FAN0 0x02
	#define MAX6620_REG_CONF_FAN1 0x03
	#define MAX6620_REG_CONF_FAN2 0x04
	#define MAX6620_REG_CONF_FAN3 0x05
	#define MAX6620_REG_DYN_FAN0 0x06
	#define MAX6620_REG_DYN_FAN1 0x07
	#define MAX6620_REG_DYN_FAN2 0x08
	#define MAX6620_REG_DYN_FAN3 0x09
	#define MAX6620_REG_TACH0 0x10
	#define MAX6620_REG_TACH1 0x12
	#define MAX6620_REG_TACH2 0x14
	#define MAX6620_REG_TACH3 0x16
	#define MAX6620_REG_VOLT0 0x18
	#define MAX6620_REG_VOLT1 0x1A
	#define MAX6620_REG_VOLT2 0x1C
	#define MAX6620_REG_VOLT3 0x1E
	#define MAX6620_REG_TAR0 0x20
	#define MAX6620_REG_TAR1 0x22
	#define MAX6620_REG_TAR2 0x24
	#define MAX6620_REG_TAR3 0x26
	#define MAX6620_REG_DAC0 0x28
	#define MAX6620_REG_DAC1 0x2A
	#define MAX6620_REG_DAC2 0x2C
	#define MAX6620_REG_DAC3 0x2E

	/*
	* Config register bits
	*/

	#define MAX6620_CFG_RUN BIT(7)
	#define MAX6620_CFG_POR BIT(6)
	#define MAX6620_CFG_TIMEOUT BIT(5)
	#define MAX6620_CFG_FULLFAN BIT(4)
	#define MAX6620_CFG_OSC BIT(3)
	#define MAX6620_CFG_WD_MASK (BIT(2) \| BIT(1))
	#define MAX6620_CFG_WD_2 BIT(1)
	#define MAX6620_CFG_WD_6 BIT(2)
	#define MAX6620_CFG_WD10 (BIT(2) \| BIT(1))
	#define MAX6620_CFG_WD BIT(0)

	/*
	* Failure status register bits
	*/

	#define MAX6620_FAIL_TACH0 BIT(4)
	#define MAX6620_FAIL_TACH1 BIT(5)
	#define MAX6620_FAIL_TACH2 BIT(6)
	#define MAX6620_FAIL_TACH3 BIT(7)
	#define MAX6620_FAIL_MASK0 BIT(0)
	#define MAX6620_FAIL_MASK1 BIT(1)
	#define MAX6620_FAIL_MASK2 BIT(2)
	#define MAX6620_FAIL_MASK3 BIT(3)

	#define MAX6620_CLOCK_FREQ 8192 /* Clock frequency in Hz */
	#define MAX6620_PULSE_PER_REV 2 /* Tachometer pulses per revolution */

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

	static const u8 config_reg[] = {
	MAX6620_REG_CONF_FAN0,
	MAX6620_REG_CONF_FAN1,
	MAX6620_REG_CONF_FAN2,
	MAX6620_REG_CONF_FAN3,
	};

	static const u8 dyn_reg[] = {
	MAX6620_REG_DYN_FAN0,
	MAX6620_REG_DYN_FAN1,
	MAX6620_REG_DYN_FAN2,
	MAX6620_REG_DYN_FAN3,
	};

	static const u8 tach_reg[] = {
	MAX6620_REG_TACH0,
	MAX6620_REG_TACH1,
	MAX6620_REG_TACH2,
	MAX6620_REG_TACH3,
	};

	static const u8 target_reg[] = {
	MAX6620_REG_TAR0,
	MAX6620_REG_TAR1,
	MAX6620_REG_TAR2,
	MAX6620_REG_TAR3,
	};

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

	struct max6620_data {
	struct i2c_client *client;
	struct mutex update_lock;
	bool valid; /* false until following fields are valid */
	unsigned long last_updated; /* in jiffies */

	/* register values */
	u8 fancfg[4];
	u8 fandyn[4];
	u8 fault;
	u16 tach[4];
	u16 target[4];
	};

	static u8 max6620_fan_div_from_reg(u8 val)
	{
	return BIT((val & 0xE0) >> 5);
	}

	static u16 max6620_fan_rpm_to_tach(u8 div, int rpm)
	{
	return (60 * div * MAX6620_CLOCK_FREQ) / (rpm * MAX6620_PULSE_PER_REV);
	}

	static int max6620_fan_tach_to_rpm(u8 div, u16 tach)
	{
	return (60 * div * MAX6620_CLOCK_FREQ) / (tach * MAX6620_PULSE_PER_REV);
	}

	static int max6620_update_device(struct device *dev)
	{
	struct max6620_data *data = dev_get_drvdata(dev);
	struct i2c_client *client = data->client;
	int i;
	int ret = 0;

	mutex_lock(&data->update_lock);

	if (time_after(jiffies, data->last_updated + HZ) \|\| !data->valid) {
	for (i = 0; i < 4; i++) {
	ret = i2c_smbus_read_byte_data(client, config_reg[i]);
	if (ret < 0)
	goto error;
	data->fancfg[i] = ret;

	ret = i2c_smbus_read_byte_data(client, dyn_reg[i]);
	if (ret < 0)
	goto error;
	data->fandyn[i] = ret;

	ret = i2c_smbus_read_byte_data(client, tach_reg[i]);
	if (ret < 0)
	goto error;
	data->tach[i] = (ret << 3) & 0x7f8;
	ret = i2c_smbus_read_byte_data(client, tach_reg[i] + 1);
	if (ret < 0)
	goto error;
	data->tach[i] \|= (ret >> 5) & 0x7;

	ret = i2c_smbus_read_byte_data(client, target_reg[i]);
	if (ret < 0)
	goto error;
	data->target[i] = (ret << 3) & 0x7f8;
	ret = i2c_smbus_read_byte_data(client, target_reg[i] + 1);
	if (ret < 0)
	goto error;
	data->target[i] \|= (ret >> 5) & 0x7;
	}

	/*
	* 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.
	*/
	ret = i2c_smbus_read_byte_data(client, MAX6620_REG_FAULT);
	if (ret < 0)
	goto error;
	data->fault \|= (ret >> 4) & (ret & 0x0F);

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

	error:
	mutex_unlock(&data->update_lock);
	return ret;
	}

	static umode_t
	max6620_is_visible(const void *data, enum hwmon_sensor_types type, u32 attr,
	int channel)
	{
	switch (type) {
	case hwmon_fan:
	switch (attr) {
	case hwmon_fan_alarm:
	case hwmon_fan_input:
	return 0444;
	case hwmon_fan_div:
	case hwmon_fan_target:
	return 0644;
	default:
	break;
	}
	break;
	default:
	break;
	}

	return 0;
	}

	static int
	max6620_read(struct device *dev, enum hwmon_sensor_types type, u32 attr,
	int channel, long *val)
	{
	struct max6620_data *data;
	struct i2c_client *client;
	int ret;
	u8 div;
	u8 val1;
	u8 val2;

	ret = max6620_update_device(dev);
	if (ret < 0)
	return ret;
	data = dev_get_drvdata(dev);
	client = data->client;

	switch (type) {
	case hwmon_fan:
	switch (attr) {
	case hwmon_fan_alarm:
	mutex_lock(&data->update_lock);
	*val = !!(data->fault & BIT(channel));

	/* Setting TACH count to re-enable fan fault detection */
	if (*val == 1) {
	val1 = (data->target[channel] >> 3) & 0xff;
	val2 = (data->target[channel] << 5) & 0xe0;
	ret = i2c_smbus_write_byte_data(client,
	target_reg[channel], val1);
	if (ret < 0) {
	mutex_unlock(&data->update_lock);
	return ret;
	}
	ret = i2c_smbus_write_byte_data(client,
	target_reg[channel] + 1, val2);
	if (ret < 0) {
	mutex_unlock(&data->update_lock);
	return ret;
	}

	data->fault &= ~BIT(channel);
	}
	mutex_unlock(&data->update_lock);

	break;
	case hwmon_fan_div:
	*val = max6620_fan_div_from_reg(data->fandyn[channel]);
	break;
	case hwmon_fan_input:
	if (data->tach[channel] == 0) {
	*val = 0;
	} else {
	div = max6620_fan_div_from_reg(data->fandyn[channel]);
	*val = max6620_fan_tach_to_rpm(div, data->tach[channel]);
	}
	break;
	case hwmon_fan_target:
	if (data->target[channel] == 0) {
	*val = 0;
	} else {
	div = max6620_fan_div_from_reg(data->fandyn[channel]);
	*val = max6620_fan_tach_to_rpm(div, data->target[channel]);
	}
	break;
	default:
	return -EOPNOTSUPP;
	}
	break;

	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static int
	max6620_write(struct device *dev, enum hwmon_sensor_types type, u32 attr,
	int channel, long val)
	{
	struct max6620_data *data;
	struct i2c_client *client;
	int ret;
	u8 div;
	u16 tach;
	u8 val1;
	u8 val2;

	ret = max6620_update_device(dev);
	if (ret < 0)
	return ret;
	data = dev_get_drvdata(dev);
	client = data->client;
	mutex_lock(&data->update_lock);

	switch (type) {
	case hwmon_fan:
	switch (attr) {
	case hwmon_fan_div:
	switch (val) {
	case 1:
	div = 0;
	break;
	case 2:
	div = 1;
	break;
	case 4:
	div = 2;
	break;
	case 8:
	div = 3;
	break;
	case 16:
	div = 4;
	break;
	case 32:
	div = 5;
	break;
	default:
	ret = -EINVAL;
	goto error;
	}
	data->fandyn[channel] &= 0x1F;
	data->fandyn[channel] \|= div << 5;
	ret = i2c_smbus_write_byte_data(client, dyn_reg[channel],
	data->fandyn[channel]);
	break;
	case hwmon_fan_target:
	val = clamp_val(val, FAN_RPM_MIN, FAN_RPM_MAX);
	div = max6620_fan_div_from_reg(data->fandyn[channel]);
	tach = max6620_fan_rpm_to_tach(div, val);
	val1 = (tach >> 3) & 0xff;
	val2 = (tach << 5) & 0xe0;
	ret = i2c_smbus_write_byte_data(client, target_reg[channel], val1);
	if (ret < 0)
	break;
	ret = i2c_smbus_write_byte_data(client, target_reg[channel] + 1, val2);
	if (ret < 0)
	break;

	/* Setting TACH count re-enables fan fault detection */
	data->fault &= ~BIT(channel);

	break;
	default:
	ret = -EOPNOTSUPP;
	break;
	}
	break;

	default:
	ret = -EOPNOTSUPP;
	break;
	}

	error:
	mutex_unlock(&data->update_lock);
	return ret;
	}

	static const struct hwmon_channel_info * const max6620_info[] = {
	HWMON_CHANNEL_INFO(fan,
	HWMON_F_INPUT \| HWMON_F_DIV \| HWMON_F_TARGET \| HWMON_F_ALARM,
	HWMON_F_INPUT \| HWMON_F_DIV \| HWMON_F_TARGET \| HWMON_F_ALARM,
	HWMON_F_INPUT \| HWMON_F_DIV \| HWMON_F_TARGET \| HWMON_F_ALARM,
	HWMON_F_INPUT \| HWMON_F_DIV \| HWMON_F_TARGET \| HWMON_F_ALARM),
	NULL
	};

	static const struct hwmon_ops max6620_hwmon_ops = {
	.read = max6620_read,
	.write = max6620_write,
	.is_visible = max6620_is_visible,
	};

	static const struct hwmon_chip_info max6620_chip_info = {
	.ops = &max6620_hwmon_ops,
	.info = max6620_info,
	};

	static int max6620_init_client(struct max6620_data *data)
	{
	struct i2c_client *client = data->client;
	int config;
	int err;
	int i;
	int reg;

	config = i2c_smbus_read_byte_data(client, MAX6620_REG_CONFIG);
	if (config < 0) {
	dev_err(&client->dev, "Error reading config, aborting.\n");
	return config;
	}

	/*
	* Set bit 4, disable other fans from going full speed on a fail
	* failure.
	*/
	err = i2c_smbus_write_byte_data(client, MAX6620_REG_CONFIG, config \| 0x10);
	if (err < 0) {
	dev_err(&client->dev, "Config write error, aborting.\n");
	return err;
	}

	for (i = 0; i < 4; i++) {
	reg = i2c_smbus_read_byte_data(client, config_reg[i]);
	if (reg < 0)
	return reg;
	data->fancfg[i] = reg;

	/* Enable RPM mode */
	data->fancfg[i] \|= 0xa8;
	err = i2c_smbus_write_byte_data(client, config_reg[i], data->fancfg[i]);
	if (err < 0)
	return err;

	/* 2 counts (001) and Rate change 100 (0.125 secs) */
	data->fandyn[i] = 0x30;
	err = i2c_smbus_write_byte_data(client, dyn_reg[i], data->fandyn[i]);
	if (err < 0)
	return err;
	}
	return 0;
	}

	static int max6620_probe(struct i2c_client *client)
	{
	struct device *dev = &client->dev;
	struct max6620_data *data;
	struct device *hwmon_dev;
	int err;

	data = devm_kzalloc(dev, sizeof(struct max6620_data), GFP_KERNEL);
	if (!data)
	return -ENOMEM;

	data->client = client;
	mutex_init(&data->update_lock);

	err = max6620_init_client(data);
	if (err)
	return err;

	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name,
	data,
	&max6620_chip_info,
	NULL);

	return PTR_ERR_OR_ZERO(hwmon_dev);
	}

	static const struct i2c_device_id max6620_id[] = {
	{ "max6620" },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, max6620_id);

	static struct i2c_driver max6620_driver = {
	.class = I2C_CLASS_HWMON,
	.driver = {
	.name = "max6620",
	},
	.probe = max6620_probe,
	.id_table = max6620_id,
	};

	module_i2c_driver(max6620_driver);

	MODULE_AUTHOR("Lucas Grunenberg");
	MODULE_DESCRIPTION("MAX6620 sensor driver");
	MODULE_LICENSE("GPL");