drivers/hwmon/max31827.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  * max31827.c - Support for Maxim Low-Power Switch
  *
  * Copyright (c) 2023 Daniel Matyas <daniel.matyas@analog.com>
  */

 #include <linux/bitfield.h>
 #include <linux/bitops.h>
 #include <linux/delay.h>
 #include <linux/hwmon.h>
 #include <linux/i2c.h>
 #include <linux/mutex.h>
 #include <linux/of_device.h>
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>

 #define MAX31827_T_REG			0x0
 #define MAX31827_CONFIGURATION_REG	0x2
 #define MAX31827_TH_REG			0x4
 #define MAX31827_TL_REG			0x6
 #define MAX31827_TH_HYST_REG		0x8
 #define MAX31827_TL_HYST_REG		0xA

 #define MAX31827_CONFIGURATION_1SHOT_MASK	BIT(0)
 #define MAX31827_CONFIGURATION_CNV_RATE_MASK	GENMASK(3, 1)
 #define MAX31827_CONFIGURATION_TIMEOUT_MASK	BIT(5)
 #define MAX31827_CONFIGURATION_RESOLUTION_MASK	GENMASK(7, 6)
 #define MAX31827_CONFIGURATION_ALRM_POL_MASK	BIT(8)
 #define MAX31827_CONFIGURATION_COMP_INT_MASK	BIT(9)
 #define MAX31827_CONFIGURATION_FLT_Q_MASK	GENMASK(11, 10)
 #define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK	BIT(14)
 #define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK	BIT(15)

 #define MAX31827_ALRM_POL_LOW	0x0
 #define MAX31827_ALRM_POL_HIGH	0x1
 #define MAX31827_FLT_Q_1	0x0
 #define MAX31827_FLT_Q_4	0x2

 #define MAX31827_8_BIT_CNV_TIME		9
 #define MAX31827_9_BIT_CNV_TIME		18
 #define MAX31827_10_BIT_CNV_TIME	35
 #define MAX31827_12_BIT_CNV_TIME	140

 #define MAX31827_16_BIT_TO_M_DGR(x)	(sign_extend32(x, 15) * 1000 / 16)
 #define MAX31827_M_DGR_TO_16_BIT(x)	(((x) << 4) / 1000)
 #define MAX31827_DEVICE_ENABLE(x)	((x) ? 0xA : 0x0)

 enum chips { max31827 = 1, max31828, max31829 };

 enum max31827_cnv {
 	MAX31827_CNV_1_DIV_64_HZ = 1,
 	MAX31827_CNV_1_DIV_32_HZ,
 	MAX31827_CNV_1_DIV_16_HZ,
 	MAX31827_CNV_1_DIV_4_HZ,
 	MAX31827_CNV_1_HZ,
 	MAX31827_CNV_4_HZ,
 	MAX31827_CNV_8_HZ,
 };

 static const u16 max31827_conversions[] = {
 	[MAX31827_CNV_1_DIV_64_HZ] = 64000,
 	[MAX31827_CNV_1_DIV_32_HZ] = 32000,
 	[MAX31827_CNV_1_DIV_16_HZ] = 16000,
 	[MAX31827_CNV_1_DIV_4_HZ] = 4000,
 	[MAX31827_CNV_1_HZ] = 1000,
 	[MAX31827_CNV_4_HZ] = 250,
 	[MAX31827_CNV_8_HZ] = 125,
 };

 enum max31827_resolution {
 	MAX31827_RES_8_BIT = 0,
 	MAX31827_RES_9_BIT,
 	MAX31827_RES_10_BIT,
 	MAX31827_RES_12_BIT,
 };

 static const u16 max31827_resolutions[] = {
 	[MAX31827_RES_8_BIT] = 1000,
 	[MAX31827_RES_9_BIT] = 500,
 	[MAX31827_RES_10_BIT] = 250,
 	[MAX31827_RES_12_BIT] = 62,
 };

 static const u16 max31827_conv_times[] = {
 	[MAX31827_RES_8_BIT] = MAX31827_8_BIT_CNV_TIME,
 	[MAX31827_RES_9_BIT] = MAX31827_9_BIT_CNV_TIME,
 	[MAX31827_RES_10_BIT] = MAX31827_10_BIT_CNV_TIME,
 	[MAX31827_RES_12_BIT] = MAX31827_12_BIT_CNV_TIME,
 };

 struct max31827_state {
 	/*
 	 * Prevent simultaneous access to the i2c client.
 	 */
 	struct mutex lock;
 	struct regmap *regmap;
 	bool enable;
 	unsigned int resolution;
 	unsigned int update_interval;
 };

 static const struct regmap_config max31827_regmap = {
 	.reg_bits = 8,
 	.val_bits = 16,
 	.max_register = 0xA,
 };

 static int shutdown_write(struct max31827_state *st, unsigned int reg,
 			  unsigned int mask, unsigned int val)
 {
 	unsigned int cfg;
 	unsigned int cnv_rate;
 	int ret;

 	/*
 	 * Before the Temperature Threshold Alarm, Alarm Hysteresis Threshold
 	 * and Resolution bits from Configuration register are changed over I2C,
 	 * the part must be in shutdown mode.
 	 *
 	 * Mutex is used to ensure, that some other process doesn't change the
 	 * configuration register.
 	 */
 	mutex_lock(&st->lock);

 	if (!st->enable) {
 		if (!mask)
 			ret = regmap_write(st->regmap, reg, val);
 		else
 			ret = regmap_update_bits(st->regmap, reg, mask, val);
 		goto unlock;
 	}

 	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
 	if (ret)
 		goto unlock;

 	cnv_rate = MAX31827_CONFIGURATION_CNV_RATE_MASK & cfg;
 	cfg = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK |
 		      MAX31827_CONFIGURATION_CNV_RATE_MASK);
 	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg);
 	if (ret)
 		goto unlock;

 	if (!mask)
 		ret = regmap_write(st->regmap, reg, val);
 	else
 		ret = regmap_update_bits(st->regmap, reg, mask, val);

 	if (ret)
 		goto unlock;

 	ret = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
 				 MAX31827_CONFIGURATION_CNV_RATE_MASK,
 				 cnv_rate);

 unlock:
 	mutex_unlock(&st->lock);
 	return ret;
 }

 static int write_alarm_val(struct max31827_state *st, unsigned int reg,
 			   long val)
 {
 	val = MAX31827_M_DGR_TO_16_BIT(val);

 	return shutdown_write(st, reg, 0, val);
 }

 static umode_t max31827_is_visible(const void *state,
 				   enum hwmon_sensor_types type, u32 attr,
 				   int channel)
 {
 	if (type == hwmon_temp) {
 		switch (attr) {
 		case hwmon_temp_enable:
 		case hwmon_temp_max:
 		case hwmon_temp_min:
 		case hwmon_temp_max_hyst:
 		case hwmon_temp_min_hyst:
 			return 0644;
 		case hwmon_temp_input:
 		case hwmon_temp_min_alarm:
 		case hwmon_temp_max_alarm:
 			return 0444;
 		default:
 			return 0;
 		}
 	} else if (type == hwmon_chip) {
 		if (attr == hwmon_chip_update_interval)
 			return 0644;
 	}

 	return 0;
 }

 static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
 			 u32 attr, int channel, long *val)
 {
 	struct max31827_state *st = dev_get_drvdata(dev);
 	unsigned int uval;
 	int ret = 0;

 	switch (type) {
 	case hwmon_temp:
 		switch (attr) {
 		case hwmon_temp_enable:
 			ret = regmap_read(st->regmap,
 					  MAX31827_CONFIGURATION_REG, &uval);
 			if (ret)
 				break;

 			uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK |
 					 MAX31827_CONFIGURATION_CNV_RATE_MASK,
 					 uval);
 			*val = !!uval;

 			break;
 		case hwmon_temp_input:
 			mutex_lock(&st->lock);

 			if (!st->enable) {
 				/*
 				 * This operation requires mutex protection,
 				 * because the chip configuration should not
 				 * be changed during the conversion process.
 				 */

 				ret = regmap_update_bits(st->regmap,
 							 MAX31827_CONFIGURATION_REG,
 							 MAX31827_CONFIGURATION_1SHOT_MASK,
 							 1);
 				if (ret) {
 					mutex_unlock(&st->lock);
 					return ret;
 				}
 				msleep(max31827_conv_times[st->resolution]);
 			}

 			/*
 			 * For 12-bit resolution the conversion time is 140 ms,
 			 * thus an additional 15 ms is needed to complete the
 			 * conversion: 125 ms + 15 ms = 140 ms
 			 */
 			if (max31827_resolutions[st->resolution] == 12 &&
 			    st->update_interval == 125)
 				usleep_range(15000, 20000);

 			ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);

 			mutex_unlock(&st->lock);

 			if (ret)
 				break;

 			*val = MAX31827_16_BIT_TO_M_DGR(uval);

 			break;
 		case hwmon_temp_max:
 			ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
 			if (ret)
 				break;

 			*val = MAX31827_16_BIT_TO_M_DGR(uval);
 			break;
 		case hwmon_temp_max_hyst:
 			ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
 					  &uval);
 			if (ret)
 				break;

 			*val = MAX31827_16_BIT_TO_M_DGR(uval);
 			break;
 		case hwmon_temp_max_alarm:
 			ret = regmap_read(st->regmap,
 					  MAX31827_CONFIGURATION_REG, &uval);
 			if (ret)
 				break;

 			*val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
 					 uval);
 			break;
 		case hwmon_temp_min:
 			ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
 			if (ret)
 				break;

 			*val = MAX31827_16_BIT_TO_M_DGR(uval);
 			break;
 		case hwmon_temp_min_hyst:
 			ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
 					  &uval);
 			if (ret)
 				break;

 			*val = MAX31827_16_BIT_TO_M_DGR(uval);
 			break;
 		case hwmon_temp_min_alarm:
 			ret = regmap_read(st->regmap,
 					  MAX31827_CONFIGURATION_REG, &uval);
 			if (ret)
 				break;

 			*val = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK,
 					 uval);
 			break;
 		default:
 			ret = -EOPNOTSUPP;
 			break;
 		}

 		break;

 	case hwmon_chip:
 		if (attr == hwmon_chip_update_interval) {
 			ret = regmap_read(st->regmap,
 					  MAX31827_CONFIGURATION_REG, &uval);
 			if (ret)
 				break;

 			uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK,
 					 uval);
 			*val = max31827_conversions[uval];
 		}
 		break;

 	default:
 		ret = -EOPNOTSUPP;
 		break;
 	}

 	return ret;
 }

 static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
 			  u32 attr, int channel, long val)
 {
 	struct max31827_state *st = dev_get_drvdata(dev);
 	int res = 1;
 	int ret;

 	switch (type) {
 	case hwmon_temp:
 		switch (attr) {
 		case hwmon_temp_enable:
 			if (val >> 1)
 				return -EINVAL;

 			mutex_lock(&st->lock);
 			/**
 			 * The chip should not be enabled while a conversion is
 			 * performed. Neither should the chip be enabled when
 			 * the alarm values are changed.
 			 */

 			st->enable = val;

 			ret = regmap_update_bits(st->regmap,
 						 MAX31827_CONFIGURATION_REG,
 						 MAX31827_CONFIGURATION_1SHOT_MASK |
 						 MAX31827_CONFIGURATION_CNV_RATE_MASK,
 						 MAX31827_DEVICE_ENABLE(val));

 			mutex_unlock(&st->lock);

 			return ret;

 		case hwmon_temp_max:
 			return write_alarm_val(st, MAX31827_TH_REG, val);

 		case hwmon_temp_max_hyst:
 			return write_alarm_val(st, MAX31827_TH_HYST_REG, val);

 		case hwmon_temp_min:
 			return write_alarm_val(st, MAX31827_TL_REG, val);

 		case hwmon_temp_min_hyst:
 			return write_alarm_val(st, MAX31827_TL_HYST_REG, val);

 		default:
 			return -EOPNOTSUPP;
 		}

 	case hwmon_chip:
 		if (attr == hwmon_chip_update_interval) {
 			if (!st->enable)
 				return -EINVAL;

 			/*
 			 * Convert the desired conversion rate into register
 			 * bits. res is already initialized with 1.
 			 *
 			 * This was inspired by lm73 driver.
 			 */
 			while (res < ARRAY_SIZE(max31827_conversions) &&
 			       val < max31827_conversions[res])
 				res++;

 			if (res == ARRAY_SIZE(max31827_conversions))
 				res = ARRAY_SIZE(max31827_conversions) - 1;

 			res = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
 					 res);

 			ret = regmap_update_bits(st->regmap,
 						 MAX31827_CONFIGURATION_REG,
 						 MAX31827_CONFIGURATION_CNV_RATE_MASK,
 						 res);
 			if (ret)
 				return ret;

 			st->update_interval = val;
 		}
 		break;

 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static ssize_t temp1_resolution_show(struct device *dev,
 				     struct device_attribute *devattr,
 				     char *buf)
 {
 	struct max31827_state *st = dev_get_drvdata(dev);
 	unsigned int val;
 	int ret;

 	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &val);
 	if (ret)
 		return ret;

 	val = FIELD_GET(MAX31827_CONFIGURATION_RESOLUTION_MASK, val);

 	return scnprintf(buf, PAGE_SIZE, "%u\n", max31827_resolutions[val]);
 }

 static ssize_t temp1_resolution_store(struct device *dev,
 				      struct device_attribute *devattr,
 				      const char *buf, size_t count)
 {
 	struct max31827_state *st = dev_get_drvdata(dev);
 	unsigned int idx = 0;
 	unsigned int val;
 	int ret;

 	ret = kstrtouint(buf, 10, &val);
 	if (ret)
 		return ret;

 	/*
 	 * Convert the desired resolution into register
 	 * bits. idx is already initialized with 0.
 	 *
 	 * This was inspired by lm73 driver.
 	 */
 	while (idx < ARRAY_SIZE(max31827_resolutions) &&
 	       val < max31827_resolutions[idx])
 		idx++;

 	if (idx == ARRAY_SIZE(max31827_resolutions))
 		idx = ARRAY_SIZE(max31827_resolutions) - 1;

 	st->resolution = idx;

 	ret = shutdown_write(st, MAX31827_CONFIGURATION_REG,
 			     MAX31827_CONFIGURATION_RESOLUTION_MASK,
 			     FIELD_PREP(MAX31827_CONFIGURATION_RESOLUTION_MASK,
 					idx));

 	return ret ? ret : count;
 }

 static DEVICE_ATTR_RW(temp1_resolution);

 static struct attribute *max31827_attrs[] = {
 	&dev_attr_temp1_resolution.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(max31827);

 static const struct i2c_device_id max31827_i2c_ids[] = {
 	{ "max31827", max31827 },
 	{ "max31828", max31828 },
 	{ "max31829", max31829 },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);

 static int max31827_init_client(struct max31827_state *st,
 				struct device *dev)
 {
 	struct fwnode_handle *fwnode;
 	unsigned int res = 0;
 	u32 data, lsb_idx;
 	enum chips type;
 	bool prop;
 	int ret;

 	fwnode = dev_fwnode(dev);

 	st->enable = true;
 	res |= MAX31827_DEVICE_ENABLE(1);

 	res |= MAX31827_CONFIGURATION_RESOLUTION_MASK;

 	prop = fwnode_property_read_bool(fwnode, "adi,comp-int");
 	res |= FIELD_PREP(MAX31827_CONFIGURATION_COMP_INT_MASK, prop);

 	prop = fwnode_property_read_bool(fwnode, "adi,timeout-enable");
 	res |= FIELD_PREP(MAX31827_CONFIGURATION_TIMEOUT_MASK, !prop);

 	type = (enum chips)(uintptr_t)device_get_match_data(dev);

 	if (fwnode_property_present(fwnode, "adi,alarm-pol")) {
 		ret = fwnode_property_read_u32(fwnode, "adi,alarm-pol", &data);
 		if (ret)
 			return ret;

 		res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK, !!data);
 	} else {
 		/*
 		 * Set default value.
 		 */
 		switch (type) {
 		case max31827:
 		case max31828:
 			res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
 					  MAX31827_ALRM_POL_LOW);
 			break;
 		case max31829:
 			res |= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
 					  MAX31827_ALRM_POL_HIGH);
 			break;
 		default:
 			return -EOPNOTSUPP;
 		}
 	}

 	if (fwnode_property_present(fwnode, "adi,fault-q")) {
 		ret = fwnode_property_read_u32(fwnode, "adi,fault-q", &data);
 		if (ret)
 			return ret;

 		/*
 		 * Convert the desired fault queue into register bits.
 		 */
 		if (data != 0)
 			lsb_idx = __ffs(data);

 		if (hweight32(data) != 1 || lsb_idx > 4) {
 			dev_err(dev, "Invalid data in adi,fault-q\n");
 			return -EINVAL;
 		}

 		res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK, lsb_idx);
 	} else {
 		/*
 		 * Set default value.
 		 */
 		switch (type) {
 		case max31827:
 			res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
 					  MAX31827_FLT_Q_1);
 			break;
 		case max31828:
 		case max31829:
 			res |= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
 					  MAX31827_FLT_Q_4);
 			break;
 		default:
 			return -EOPNOTSUPP;
 		}
 	}

 	return regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, res);
 }

 static const struct hwmon_channel_info *max31827_info[] = {
 	HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE | HWMON_T_INPUT | HWMON_T_MIN |
 					 HWMON_T_MIN_HYST | HWMON_T_MIN_ALARM |
 					 HWMON_T_MAX | HWMON_T_MAX_HYST |
 					 HWMON_T_MAX_ALARM),
 	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
 	NULL,
 };

 static const struct hwmon_ops max31827_hwmon_ops = {
 	.is_visible = max31827_is_visible,
 	.read = max31827_read,
 	.write = max31827_write,
 };

 static const struct hwmon_chip_info max31827_chip_info = {
 	.ops = &max31827_hwmon_ops,
 	.info = max31827_info,
 };

 static int max31827_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
 	struct device *hwmon_dev;
 	struct max31827_state *st;
 	int err;

 	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
 		return -EOPNOTSUPP;

 	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
 	if (!st)
 		return -ENOMEM;

 	mutex_init(&st->lock);

 	st->regmap = devm_regmap_init_i2c(client, &max31827_regmap);
 	if (IS_ERR(st->regmap))
 		return dev_err_probe(dev, PTR_ERR(st->regmap),
 				     "Failed to allocate regmap.\n");

 	err = devm_regulator_get_enable(dev, "vref");
 	if (err)
 		return dev_err_probe(dev, err, "failed to enable regulator\n");

 	err = max31827_init_client(st, dev);
 	if (err)
 		return err;

 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
 							 &max31827_chip_info,
 							 max31827_groups);

 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }

 static const struct of_device_id max31827_of_match[] = {
 	{
 		.compatible = "adi,max31827",
 		.data = (void *)max31827
 	},
 	{
 		.compatible = "adi,max31828",
 		.data = (void *)max31828
 	},
 	{
 		.compatible = "adi,max31829",
 		.data = (void *)max31829
 	},
 	{ }
 };
 MODULE_DEVICE_TABLE(of, max31827_of_match);

 static struct i2c_driver max31827_driver = {
 	.class = I2C_CLASS_HWMON,
 	.driver = {
 		.name = "max31827",
 		.of_match_table = max31827_of_match,
 	},
 	.probe = max31827_probe,
 	.id_table = max31827_i2c_ids,
 };
 module_i2c_driver(max31827_driver);

 MODULE_AUTHOR("Daniel Matyas <daniel.matyas@analog.com>");
 MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0
	/*
	* max31827.c - Support for Maxim Low-Power Switch
	*
	* Copyright (c) 2023 Daniel Matyas <daniel.matyas@analog.com>
	*/

	#include <linux/bitfield.h>
	#include <linux/bitops.h>
	#include <linux/delay.h>
	#include <linux/hwmon.h>
	#include <linux/i2c.h>
	#include <linux/mutex.h>
	#include <linux/of_device.h>
	#include <linux/regmap.h>
	#include <linux/regulator/consumer.h>

	#define MAX31827_T_REG 0x0
	#define MAX31827_CONFIGURATION_REG 0x2
	#define MAX31827_TH_REG 0x4
	#define MAX31827_TL_REG 0x6
	#define MAX31827_TH_HYST_REG 0x8
	#define MAX31827_TL_HYST_REG 0xA

	#define MAX31827_CONFIGURATION_1SHOT_MASK BIT(0)
	#define MAX31827_CONFIGURATION_CNV_RATE_MASK GENMASK(3, 1)
	#define MAX31827_CONFIGURATION_TIMEOUT_MASK BIT(5)
	#define MAX31827_CONFIGURATION_RESOLUTION_MASK GENMASK(7, 6)
	#define MAX31827_CONFIGURATION_ALRM_POL_MASK BIT(8)
	#define MAX31827_CONFIGURATION_COMP_INT_MASK BIT(9)
	#define MAX31827_CONFIGURATION_FLT_Q_MASK GENMASK(11, 10)
	#define MAX31827_CONFIGURATION_U_TEMP_STAT_MASK BIT(14)
	#define MAX31827_CONFIGURATION_O_TEMP_STAT_MASK BIT(15)

	#define MAX31827_ALRM_POL_LOW 0x0
	#define MAX31827_ALRM_POL_HIGH 0x1
	#define MAX31827_FLT_Q_1 0x0
	#define MAX31827_FLT_Q_4 0x2

	#define MAX31827_8_BIT_CNV_TIME 9
	#define MAX31827_9_BIT_CNV_TIME 18
	#define MAX31827_10_BIT_CNV_TIME 35
	#define MAX31827_12_BIT_CNV_TIME 140

	#define MAX31827_16_BIT_TO_M_DGR(x) (sign_extend32(x, 15) * 1000 / 16)
	#define MAX31827_M_DGR_TO_16_BIT(x) (((x) << 4) / 1000)
	#define MAX31827_DEVICE_ENABLE(x) ((x) ? 0xA : 0x0)

	enum chips { max31827 = 1, max31828, max31829 };

	enum max31827_cnv {
	MAX31827_CNV_1_DIV_64_HZ = 1,
	MAX31827_CNV_1_DIV_32_HZ,
	MAX31827_CNV_1_DIV_16_HZ,
	MAX31827_CNV_1_DIV_4_HZ,
	MAX31827_CNV_1_HZ,
	MAX31827_CNV_4_HZ,
	MAX31827_CNV_8_HZ,
	};

	static const u16 max31827_conversions[] = {
	[MAX31827_CNV_1_DIV_64_HZ] = 64000,
	[MAX31827_CNV_1_DIV_32_HZ] = 32000,
	[MAX31827_CNV_1_DIV_16_HZ] = 16000,
	[MAX31827_CNV_1_DIV_4_HZ] = 4000,
	[MAX31827_CNV_1_HZ] = 1000,
	[MAX31827_CNV_4_HZ] = 250,
	[MAX31827_CNV_8_HZ] = 125,
	};

	enum max31827_resolution {
	MAX31827_RES_8_BIT = 0,
	MAX31827_RES_9_BIT,
	MAX31827_RES_10_BIT,
	MAX31827_RES_12_BIT,
	};

	static const u16 max31827_resolutions[] = {
	[MAX31827_RES_8_BIT] = 1000,
	[MAX31827_RES_9_BIT] = 500,
	[MAX31827_RES_10_BIT] = 250,
	[MAX31827_RES_12_BIT] = 62,
	};

	static const u16 max31827_conv_times[] = {
	[MAX31827_RES_8_BIT] = MAX31827_8_BIT_CNV_TIME,
	[MAX31827_RES_9_BIT] = MAX31827_9_BIT_CNV_TIME,
	[MAX31827_RES_10_BIT] = MAX31827_10_BIT_CNV_TIME,
	[MAX31827_RES_12_BIT] = MAX31827_12_BIT_CNV_TIME,
	};

	struct max31827_state {
	/*
	* Prevent simultaneous access to the i2c client.
	*/
	struct mutex lock;
	struct regmap *regmap;
	bool enable;
	unsigned int resolution;
	unsigned int update_interval;
	};

	static const struct regmap_config max31827_regmap = {
	.reg_bits = 8,
	.val_bits = 16,
	.max_register = 0xA,
	};

	static int shutdown_write(struct max31827_state *st, unsigned int reg,
	unsigned int mask, unsigned int val)
	{
	unsigned int cfg;
	unsigned int cnv_rate;
	int ret;

	/*
	* Before the Temperature Threshold Alarm, Alarm Hysteresis Threshold
	* and Resolution bits from Configuration register are changed over I2C,
	* the part must be in shutdown mode.
	*
	* Mutex is used to ensure, that some other process doesn't change the
	* configuration register.
	*/
	mutex_lock(&st->lock);

	if (!st->enable) {
	if (!mask)
	ret = regmap_write(st->regmap, reg, val);
	else
	ret = regmap_update_bits(st->regmap, reg, mask, val);
	goto unlock;
	}

	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &cfg);
	if (ret)
	goto unlock;

	cnv_rate = MAX31827_CONFIGURATION_CNV_RATE_MASK & cfg;
	cfg = cfg & ~(MAX31827_CONFIGURATION_1SHOT_MASK \|
	MAX31827_CONFIGURATION_CNV_RATE_MASK);
	ret = regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, cfg);
	if (ret)
	goto unlock;

	if (!mask)
	ret = regmap_write(st->regmap, reg, val);
	else
	ret = regmap_update_bits(st->regmap, reg, mask, val);

	if (ret)
	goto unlock;

	ret = regmap_update_bits(st->regmap, MAX31827_CONFIGURATION_REG,
	MAX31827_CONFIGURATION_CNV_RATE_MASK,
	cnv_rate);

	unlock:
	mutex_unlock(&st->lock);
	return ret;
	}

	static int write_alarm_val(struct max31827_state *st, unsigned int reg,
	long val)
	{
	val = MAX31827_M_DGR_TO_16_BIT(val);

	return shutdown_write(st, reg, 0, val);
	}

	static umode_t max31827_is_visible(const void *state,
	enum hwmon_sensor_types type, u32 attr,
	int channel)
	{
	if (type == hwmon_temp) {
	switch (attr) {
	case hwmon_temp_enable:
	case hwmon_temp_max:
	case hwmon_temp_min:
	case hwmon_temp_max_hyst:
	case hwmon_temp_min_hyst:
	return 0644;
	case hwmon_temp_input:
	case hwmon_temp_min_alarm:
	case hwmon_temp_max_alarm:
	return 0444;
	default:
	return 0;
	}
	} else if (type == hwmon_chip) {
	if (attr == hwmon_chip_update_interval)
	return 0644;
	}

	return 0;
	}

	static int max31827_read(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long *val)
	{
	struct max31827_state *st = dev_get_drvdata(dev);
	unsigned int uval;
	int ret = 0;

	switch (type) {
	case hwmon_temp:
	switch (attr) {
	case hwmon_temp_enable:
	ret = regmap_read(st->regmap,
	MAX31827_CONFIGURATION_REG, &uval);
	if (ret)
	break;

	uval = FIELD_GET(MAX31827_CONFIGURATION_1SHOT_MASK \|
	MAX31827_CONFIGURATION_CNV_RATE_MASK,
	uval);
	*val = !!uval;

	break;
	case hwmon_temp_input:
	mutex_lock(&st->lock);

	if (!st->enable) {
	/*
	* This operation requires mutex protection,
	* because the chip configuration should not
	* be changed during the conversion process.
	*/

	ret = regmap_update_bits(st->regmap,
	MAX31827_CONFIGURATION_REG,
	MAX31827_CONFIGURATION_1SHOT_MASK,
	1);
	if (ret) {
	mutex_unlock(&st->lock);
	return ret;
	}
	msleep(max31827_conv_times[st->resolution]);
	}

	/*
	* For 12-bit resolution the conversion time is 140 ms,
	* thus an additional 15 ms is needed to complete the
	* conversion: 125 ms + 15 ms = 140 ms
	*/
	if (max31827_resolutions[st->resolution] == 12 &&
	st->update_interval == 125)
	usleep_range(15000, 20000);

	ret = regmap_read(st->regmap, MAX31827_T_REG, &uval);

	mutex_unlock(&st->lock);

	if (ret)
	break;

	*val = MAX31827_16_BIT_TO_M_DGR(uval);

	break;
	case hwmon_temp_max:
	ret = regmap_read(st->regmap, MAX31827_TH_REG, &uval);
	if (ret)
	break;

	*val = MAX31827_16_BIT_TO_M_DGR(uval);
	break;
	case hwmon_temp_max_hyst:
	ret = regmap_read(st->regmap, MAX31827_TH_HYST_REG,
	&uval);
	if (ret)
	break;

	*val = MAX31827_16_BIT_TO_M_DGR(uval);
	break;
	case hwmon_temp_max_alarm:
	ret = regmap_read(st->regmap,
	MAX31827_CONFIGURATION_REG, &uval);
	if (ret)
	break;

	*val = FIELD_GET(MAX31827_CONFIGURATION_O_TEMP_STAT_MASK,
	uval);
	break;
	case hwmon_temp_min:
	ret = regmap_read(st->regmap, MAX31827_TL_REG, &uval);
	if (ret)
	break;

	*val = MAX31827_16_BIT_TO_M_DGR(uval);
	break;
	case hwmon_temp_min_hyst:
	ret = regmap_read(st->regmap, MAX31827_TL_HYST_REG,
	&uval);
	if (ret)
	break;

	*val = MAX31827_16_BIT_TO_M_DGR(uval);
	break;
	case hwmon_temp_min_alarm:
	ret = regmap_read(st->regmap,
	MAX31827_CONFIGURATION_REG, &uval);
	if (ret)
	break;

	*val = FIELD_GET(MAX31827_CONFIGURATION_U_TEMP_STAT_MASK,
	uval);
	break;
	default:
	ret = -EOPNOTSUPP;
	break;
	}

	break;

	case hwmon_chip:
	if (attr == hwmon_chip_update_interval) {
	ret = regmap_read(st->regmap,
	MAX31827_CONFIGURATION_REG, &uval);
	if (ret)
	break;

	uval = FIELD_GET(MAX31827_CONFIGURATION_CNV_RATE_MASK,
	uval);
	*val = max31827_conversions[uval];
	}
	break;

	default:
	ret = -EOPNOTSUPP;
	break;
	}

	return ret;
	}

	static int max31827_write(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long val)
	{
	struct max31827_state *st = dev_get_drvdata(dev);
	int res = 1;
	int ret;

	switch (type) {
	case hwmon_temp:
	switch (attr) {
	case hwmon_temp_enable:
	if (val >> 1)
	return -EINVAL;

	mutex_lock(&st->lock);
	/**
	* The chip should not be enabled while a conversion is
	* performed. Neither should the chip be enabled when
	* the alarm values are changed.
	*/

	st->enable = val;

	ret = regmap_update_bits(st->regmap,
	MAX31827_CONFIGURATION_REG,
	MAX31827_CONFIGURATION_1SHOT_MASK \|
	MAX31827_CONFIGURATION_CNV_RATE_MASK,
	MAX31827_DEVICE_ENABLE(val));

	mutex_unlock(&st->lock);

	return ret;

	case hwmon_temp_max:
	return write_alarm_val(st, MAX31827_TH_REG, val);

	case hwmon_temp_max_hyst:
	return write_alarm_val(st, MAX31827_TH_HYST_REG, val);

	case hwmon_temp_min:
	return write_alarm_val(st, MAX31827_TL_REG, val);

	case hwmon_temp_min_hyst:
	return write_alarm_val(st, MAX31827_TL_HYST_REG, val);

	default:
	return -EOPNOTSUPP;
	}

	case hwmon_chip:
	if (attr == hwmon_chip_update_interval) {
	if (!st->enable)
	return -EINVAL;

	/*
	* Convert the desired conversion rate into register
	* bits. res is already initialized with 1.
	*
	* This was inspired by lm73 driver.
	*/
	while (res < ARRAY_SIZE(max31827_conversions) &&
	val < max31827_conversions[res])
	res++;

	if (res == ARRAY_SIZE(max31827_conversions))
	res = ARRAY_SIZE(max31827_conversions) - 1;

	res = FIELD_PREP(MAX31827_CONFIGURATION_CNV_RATE_MASK,
	res);

	ret = regmap_update_bits(st->regmap,
	MAX31827_CONFIGURATION_REG,
	MAX31827_CONFIGURATION_CNV_RATE_MASK,
	res);
	if (ret)
	return ret;

	st->update_interval = val;
	}
	break;

	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static ssize_t temp1_resolution_show(struct device *dev,
	struct device_attribute *devattr,
	char *buf)
	{
	struct max31827_state *st = dev_get_drvdata(dev);
	unsigned int val;
	int ret;

	ret = regmap_read(st->regmap, MAX31827_CONFIGURATION_REG, &val);
	if (ret)
	return ret;

	val = FIELD_GET(MAX31827_CONFIGURATION_RESOLUTION_MASK, val);

	return scnprintf(buf, PAGE_SIZE, "%u\n", max31827_resolutions[val]);
	}

	static ssize_t temp1_resolution_store(struct device *dev,
	struct device_attribute *devattr,
	const char *buf, size_t count)
	{
	struct max31827_state *st = dev_get_drvdata(dev);
	unsigned int idx = 0;
	unsigned int val;
	int ret;

	ret = kstrtouint(buf, 10, &val);
	if (ret)
	return ret;

	/*
	* Convert the desired resolution into register
	* bits. idx is already initialized with 0.
	*
	* This was inspired by lm73 driver.
	*/
	while (idx < ARRAY_SIZE(max31827_resolutions) &&
	val < max31827_resolutions[idx])
	idx++;

	if (idx == ARRAY_SIZE(max31827_resolutions))
	idx = ARRAY_SIZE(max31827_resolutions) - 1;

	st->resolution = idx;

	ret = shutdown_write(st, MAX31827_CONFIGURATION_REG,
	MAX31827_CONFIGURATION_RESOLUTION_MASK,
	FIELD_PREP(MAX31827_CONFIGURATION_RESOLUTION_MASK,
	idx));

	return ret ? ret : count;
	}

	static DEVICE_ATTR_RW(temp1_resolution);

	static struct attribute *max31827_attrs[] = {
	&dev_attr_temp1_resolution.attr,
	NULL
	};
	ATTRIBUTE_GROUPS(max31827);

	static const struct i2c_device_id max31827_i2c_ids[] = {
	{ "max31827", max31827 },
	{ "max31828", max31828 },
	{ "max31829", max31829 },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, max31827_i2c_ids);

	static int max31827_init_client(struct max31827_state *st,
	struct device *dev)
	{
	struct fwnode_handle *fwnode;
	unsigned int res = 0;
	u32 data, lsb_idx;
	enum chips type;
	bool prop;
	int ret;

	fwnode = dev_fwnode(dev);

	st->enable = true;
	res \|= MAX31827_DEVICE_ENABLE(1);

	res \|= MAX31827_CONFIGURATION_RESOLUTION_MASK;

	prop = fwnode_property_read_bool(fwnode, "adi,comp-int");
	res \|= FIELD_PREP(MAX31827_CONFIGURATION_COMP_INT_MASK, prop);

	prop = fwnode_property_read_bool(fwnode, "adi,timeout-enable");
	res \|= FIELD_PREP(MAX31827_CONFIGURATION_TIMEOUT_MASK, !prop);

	type = (enum chips)(uintptr_t)device_get_match_data(dev);

	if (fwnode_property_present(fwnode, "adi,alarm-pol")) {
	ret = fwnode_property_read_u32(fwnode, "adi,alarm-pol", &data);
	if (ret)
	return ret;

	res \|= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK, !!data);
	} else {
	/*
	* Set default value.
	*/
	switch (type) {
	case max31827:
	case max31828:
	res \|= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
	MAX31827_ALRM_POL_LOW);
	break;
	case max31829:
	res \|= FIELD_PREP(MAX31827_CONFIGURATION_ALRM_POL_MASK,
	MAX31827_ALRM_POL_HIGH);
	break;
	default:
	return -EOPNOTSUPP;
	}
	}

	if (fwnode_property_present(fwnode, "adi,fault-q")) {
	ret = fwnode_property_read_u32(fwnode, "adi,fault-q", &data);
	if (ret)
	return ret;

	/*
	* Convert the desired fault queue into register bits.
	*/
	if (data != 0)
	lsb_idx = __ffs(data);

	if (hweight32(data) != 1 \|\| lsb_idx > 4) {
	dev_err(dev, "Invalid data in adi,fault-q\n");
	return -EINVAL;
	}

	res \|= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK, lsb_idx);
	} else {
	/*
	* Set default value.
	*/
	switch (type) {
	case max31827:
	res \|= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
	MAX31827_FLT_Q_1);
	break;
	case max31828:
	case max31829:
	res \|= FIELD_PREP(MAX31827_CONFIGURATION_FLT_Q_MASK,
	MAX31827_FLT_Q_4);
	break;
	default:
	return -EOPNOTSUPP;
	}
	}

	return regmap_write(st->regmap, MAX31827_CONFIGURATION_REG, res);
	}

	static const struct hwmon_channel_info *max31827_info[] = {
	HWMON_CHANNEL_INFO(temp, HWMON_T_ENABLE \| HWMON_T_INPUT \| HWMON_T_MIN \|
	HWMON_T_MIN_HYST \| HWMON_T_MIN_ALARM \|
	HWMON_T_MAX \| HWMON_T_MAX_HYST \|
	HWMON_T_MAX_ALARM),
	HWMON_CHANNEL_INFO(chip, HWMON_C_UPDATE_INTERVAL),
	NULL,
	};

	static const struct hwmon_ops max31827_hwmon_ops = {
	.is_visible = max31827_is_visible,
	.read = max31827_read,
	.write = max31827_write,
	};

	static const struct hwmon_chip_info max31827_chip_info = {
	.ops = &max31827_hwmon_ops,
	.info = max31827_info,
	};

	static int max31827_probe(struct i2c_client *client)
	{
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	struct max31827_state *st;
	int err;

	if (!i2c_check_functionality(client->adapter, I2C_FUNC_SMBUS_WORD_DATA))
	return -EOPNOTSUPP;

	st = devm_kzalloc(dev, sizeof(*st), GFP_KERNEL);
	if (!st)
	return -ENOMEM;

	mutex_init(&st->lock);

	st->regmap = devm_regmap_init_i2c(client, &max31827_regmap);
	if (IS_ERR(st->regmap))
	return dev_err_probe(dev, PTR_ERR(st->regmap),
	"Failed to allocate regmap.\n");

	err = devm_regulator_get_enable(dev, "vref");
	if (err)
	return dev_err_probe(dev, err, "failed to enable regulator\n");

	err = max31827_init_client(st, dev);
	if (err)
	return err;

	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, st,
	&max31827_chip_info,
	max31827_groups);

	return PTR_ERR_OR_ZERO(hwmon_dev);
	}

	static const struct of_device_id max31827_of_match[] = {
	{
	.compatible = "adi,max31827",
	.data = (void *)max31827
	},
	{
	.compatible = "adi,max31828",
	.data = (void *)max31828
	},
	{
	.compatible = "adi,max31829",
	.data = (void *)max31829
	},
	{ }
	};
	MODULE_DEVICE_TABLE(of, max31827_of_match);

	static struct i2c_driver max31827_driver = {
	.class = I2C_CLASS_HWMON,
	.driver = {
	.name = "max31827",
	.of_match_table = max31827_of_match,
	},
	.probe = max31827_probe,
	.id_table = max31827_i2c_ids,
	};
	module_i2c_driver(max31827_driver);

	MODULE_AUTHOR("Daniel Matyas <daniel.matyas@analog.com>");
	MODULE_DESCRIPTION("Maxim MAX31827 low-power temperature switch driver");
	MODULE_LICENSE("GPL");