drivers/hwmon/jc42.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-or-later
 /*
  * jc42.c - driver for Jedec JC42.4 compliant temperature sensors
  *
  * Copyright (c) 2010  Ericsson AB.
  *
  * Derived from lm77.c by Andras BALI <drewie@freemail.hu>.
  *
  * JC42.4 compliant temperature sensors are typically used on memory modules.
  */

 #include <linux/bitops.h>
 #include <linux/bitfield.h>
 #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/err.h>
 #include <linux/mutex.h>
 #include <linux/of.h>
 #include <linux/regmap.h>

 /* Addresses to scan */
 static const unsigned short normal_i2c[] = {
 	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, I2C_CLIENT_END };

 /* JC42 registers. All registers are 16 bit. */
 #define JC42_REG_CAP		0x00
 #define JC42_REG_CONFIG		0x01
 #define JC42_REG_TEMP_UPPER	0x02
 #define JC42_REG_TEMP_LOWER	0x03
 #define JC42_REG_TEMP_CRITICAL	0x04
 #define JC42_REG_TEMP		0x05
 #define JC42_REG_MANID		0x06
 #define JC42_REG_DEVICEID	0x07
 #define JC42_REG_SMBUS		0x22 /* NXP and Atmel, possibly others? */

 /* Status bits in temperature register */
 #define JC42_ALARM_CRIT		BIT(15)
 #define JC42_ALARM_MAX		BIT(14)
 #define JC42_ALARM_MIN		BIT(13)

 /* Configuration register defines */
 #define JC42_CFG_CRIT_ONLY	BIT(2)
 #define JC42_CFG_TCRIT_LOCK	BIT(6)
 #define JC42_CFG_EVENT_LOCK	BIT(7)
 #define JC42_CFG_SHUTDOWN	BIT(8)
 #define JC42_CFG_HYST_MASK	GENMASK(10, 9)

 /* Capabilities */
 #define JC42_CAP_RANGE		BIT(2)

 /* Manufacturer IDs */
 #define ADT_MANID		0x11d4  /* Analog Devices */
 #define ATMEL_MANID		0x001f  /* Atmel */
 #define ATMEL_MANID2		0x1114	/* Atmel */
 #define MAX_MANID		0x004d  /* Maxim */
 #define IDT_MANID		0x00b3  /* IDT */
 #define MCP_MANID		0x0054  /* Microchip */
 #define NXP_MANID		0x1131  /* NXP Semiconductors */
 #define ONS_MANID		0x1b09  /* ON Semiconductor */
 #define STM_MANID		0x104a  /* ST Microelectronics */
 #define GT_MANID		0x1c68	/* Giantec */
 #define GT_MANID2		0x132d	/* Giantec, 2nd mfg ID */
 #define SI_MANID		0x1c85	/* Seiko Instruments */

 /* SMBUS register */
 #define SMBUS_STMOUT		BIT(7)  /* SMBus time-out, active low */

 /* Supported chips */

 /* Analog Devices */
 #define ADT7408_DEVID		0x0801
 #define ADT7408_DEVID_MASK	0xffff

 /* Atmel */
 #define AT30TS00_DEVID		0x8201
 #define AT30TS00_DEVID_MASK	0xffff

 #define GT34TS02_DEVID		0x3300
 #define GT34TS02_DEVID_MASK	0xff00

 #define TS3000_DEVID		0x2900  /* Also matches TSE2002 */
 #define TS3000_DEVID_MASK	0xff00

 #define TS3001_DEVID		0x3000
 #define TS3001_DEVID_MASK	0xff00

 /* Maxim */
 #define MAX6604_DEVID		0x3e00
 #define MAX6604_DEVID_MASK	0xffff

 /* Microchip */
 #define MCP9804_DEVID		0x0200
 #define MCP9804_DEVID_MASK	0xfffc

 #define MCP9808_DEVID		0x0400
 #define MCP9808_DEVID_MASK	0xfffc

 #define MCP98242_DEVID		0x2000
 #define MCP98242_DEVID_MASK	0xfffc

 #define MCP98243_DEVID		0x2100
 #define MCP98243_DEVID_MASK	0xfffc

 #define MCP9843_DEVID		0x0000	/* Also matches mcp9805 */
 #define MCP9843_DEVID_MASK	0xfffe

 /* NXP */
 #define SE97_DEVID		0xa200
 #define SE97_DEVID_MASK		0xfffc

 #define SE98_DEVID		0xa100
 #define SE98_DEVID_MASK		0xfffc

 /* ON Semiconductor */
 #define CAT6095_DEVID		0x0800	/* Also matches CAT34TS02 */
 #define CAT6095_DEVID_MASK	0xffe0

 #define CAT34TS02C_DEVID	0x0a00
 #define CAT34TS02C_DEVID_MASK	0xfff0

 /* ST Microelectronics */
 #define STTS424_DEVID		0x0101
 #define STTS424_DEVID_MASK	0xffff

 #define STTS424E_DEVID		0x0000
 #define STTS424E_DEVID_MASK	0xfffe

 #define STTS2002_DEVID		0x0300
 #define STTS2002_DEVID_MASK	0xffff

 #define STTS3000_DEVID		0x0200
 #define STTS3000_DEVID_MASK	0xffff

 /* TSE2004 compliant sensors */
 #define TSE2004_DEVID		0x2200
 #define TSE2004_DEVID_MASK	0xff00

 static u16 jc42_hysteresis[] = { 0, 1500, 3000, 6000 };

 struct jc42_chips {
 	u16 manid;
 	u16 devid;
 	u16 devid_mask;
 };

 static struct jc42_chips jc42_chips[] = {
 	{ ADT_MANID, ADT7408_DEVID, ADT7408_DEVID_MASK },
 	{ ATMEL_MANID, AT30TS00_DEVID, AT30TS00_DEVID_MASK },
 	{ ATMEL_MANID2, TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ GT_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ GT_MANID2, GT34TS02_DEVID, GT34TS02_DEVID_MASK },
 	{ IDT_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ IDT_MANID, TS3000_DEVID, TS3000_DEVID_MASK },
 	{ IDT_MANID, TS3001_DEVID, TS3001_DEVID_MASK },
 	{ MAX_MANID, MAX6604_DEVID, MAX6604_DEVID_MASK },
 	{ MCP_MANID, MCP9804_DEVID, MCP9804_DEVID_MASK },
 	{ MCP_MANID, MCP9808_DEVID, MCP9808_DEVID_MASK },
 	{ MCP_MANID, MCP98242_DEVID, MCP98242_DEVID_MASK },
 	{ MCP_MANID, MCP98243_DEVID, MCP98243_DEVID_MASK },
 	{ MCP_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ MCP_MANID, MCP9843_DEVID, MCP9843_DEVID_MASK },
 	{ NXP_MANID, SE97_DEVID, SE97_DEVID_MASK },
 	{ ONS_MANID, CAT6095_DEVID, CAT6095_DEVID_MASK },
 	{ ONS_MANID, CAT34TS02C_DEVID, CAT34TS02C_DEVID_MASK },
 	{ ONS_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ ONS_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ NXP_MANID, SE98_DEVID, SE98_DEVID_MASK },
 	{ SI_MANID,  TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ STM_MANID, STTS424_DEVID, STTS424_DEVID_MASK },
 	{ STM_MANID, STTS424E_DEVID, STTS424E_DEVID_MASK },
 	{ STM_MANID, STTS2002_DEVID, STTS2002_DEVID_MASK },
 	{ STM_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
 	{ STM_MANID, STTS3000_DEVID, STTS3000_DEVID_MASK },
 };

 /* Each client has this additional data */
 struct jc42_data {
 	struct mutex	update_lock;	/* protect register access */
 	struct regmap	*regmap;
 	bool		extended;	/* true if extended range supported */
 	bool		valid;
 	u16		orig_config;	/* original configuration */
 	u16		config;		/* current configuration */
 };

 #define JC42_TEMP_MIN_EXTENDED	(-40000)
 #define JC42_TEMP_MIN		0
 #define JC42_TEMP_MAX		125000

 static u16 jc42_temp_to_reg(long temp, bool extended)
 {
 	int ntemp = clamp_val(temp,
 			      extended ? JC42_TEMP_MIN_EXTENDED :
 			      JC42_TEMP_MIN, JC42_TEMP_MAX);

 	/* convert from 0.001 to 0.0625 resolution */
 	return (ntemp * 2 / 125) & 0x1fff;
 }

 static int jc42_temp_from_reg(s16 reg)
 {
 	reg = sign_extend32(reg, 12);

 	/* convert from 0.0625 to 0.001 resolution */
 	return reg * 125 / 2;
 }

 static int jc42_read(struct device *dev, enum hwmon_sensor_types type,
 		     u32 attr, int channel, long *val)
 {
 	struct jc42_data *data = dev_get_drvdata(dev);
 	unsigned int regval;
 	int ret, temp, hyst;

 	mutex_lock(&data->update_lock);

 	switch (attr) {
 	case hwmon_temp_input:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
 		if (ret)
 			break;

 		*val = jc42_temp_from_reg(regval);
 		break;
 	case hwmon_temp_min:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP_LOWER, &regval);
 		if (ret)
 			break;

 		*val = jc42_temp_from_reg(regval);
 		break;
 	case hwmon_temp_max:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP_UPPER, &regval);
 		if (ret)
 			break;

 		*val = jc42_temp_from_reg(regval);
 		break;
 	case hwmon_temp_crit:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP_CRITICAL,
 				  &regval);
 		if (ret)
 			break;

 		*val = jc42_temp_from_reg(regval);
 		break;
 	case hwmon_temp_max_hyst:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP_UPPER, &regval);
 		if (ret)
 			break;

 		temp = jc42_temp_from_reg(regval);
 		hyst = jc42_hysteresis[FIELD_GET(JC42_CFG_HYST_MASK,
 						 data->config)];
 		*val = temp - hyst;
 		break;
 	case hwmon_temp_crit_hyst:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP_CRITICAL,
 				  &regval);
 		if (ret)
 			break;

 		temp = jc42_temp_from_reg(regval);
 		hyst = jc42_hysteresis[FIELD_GET(JC42_CFG_HYST_MASK,
 						 data->config)];
 		*val = temp - hyst;
 		break;
 	case hwmon_temp_min_alarm:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
 		if (ret)
 			break;

 		*val = FIELD_GET(JC42_ALARM_MIN, regval);
 		break;
 	case hwmon_temp_max_alarm:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
 		if (ret)
 			break;

 		*val = FIELD_GET(JC42_ALARM_MAX, regval);
 		break;
 	case hwmon_temp_crit_alarm:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
 		if (ret)
 			break;

 		*val = FIELD_GET(JC42_ALARM_CRIT, regval);
 		break;
 	default:
 		ret = -EOPNOTSUPP;
 		break;
 	}

 	mutex_unlock(&data->update_lock);

 	return ret;
 }

 static int jc42_write(struct device *dev, enum hwmon_sensor_types type,
 		      u32 attr, int channel, long val)
 {
 	struct jc42_data *data = dev_get_drvdata(dev);
 	unsigned int regval;
 	int diff, hyst;
 	int ret;

 	mutex_lock(&data->update_lock);

 	switch (attr) {
 	case hwmon_temp_min:
 		ret = regmap_write(data->regmap, JC42_REG_TEMP_LOWER,
 				   jc42_temp_to_reg(val, data->extended));
 		break;
 	case hwmon_temp_max:
 		ret = regmap_write(data->regmap, JC42_REG_TEMP_UPPER,
 				   jc42_temp_to_reg(val, data->extended));
 		break;
 	case hwmon_temp_crit:
 		ret = regmap_write(data->regmap, JC42_REG_TEMP_CRITICAL,
 				   jc42_temp_to_reg(val, data->extended));
 		break;
 	case hwmon_temp_crit_hyst:
 		ret = regmap_read(data->regmap, JC42_REG_TEMP_CRITICAL,
 				  &regval);
 		if (ret)
 			break;

 		/*
 		 * JC42.4 compliant chips only support four hysteresis values.
 		 * Pick best choice and go from there.
 		 */
 		val = clamp_val(val, (data->extended ? JC42_TEMP_MIN_EXTENDED
 						     : JC42_TEMP_MIN) - 6000,
 				JC42_TEMP_MAX);
 		diff = jc42_temp_from_reg(regval) - val;
 		hyst = 0;
 		if (diff > 0) {
 			if (diff < 2250)
 				hyst = 1;	/* 1.5 degrees C */
 			else if (diff < 4500)
 				hyst = 2;	/* 3.0 degrees C */
 			else
 				hyst = 3;	/* 6.0 degrees C */
 		}
 		data->config = (data->config & ~JC42_CFG_HYST_MASK) |
 				FIELD_PREP(JC42_CFG_HYST_MASK, hyst);
 		ret = regmap_write(data->regmap, JC42_REG_CONFIG,
 				   data->config);
 		break;
 	default:
 		ret = -EOPNOTSUPP;
 		break;
 	}

 	mutex_unlock(&data->update_lock);

 	return ret;
 }

 static umode_t jc42_is_visible(const void *_data, enum hwmon_sensor_types type,
 			       u32 attr, int channel)
 {
 	const struct jc42_data *data = _data;
 	unsigned int config = data->config;
 	umode_t mode = 0444;

 	switch (attr) {
 	case hwmon_temp_min:
 	case hwmon_temp_max:
 		if (!(config & JC42_CFG_EVENT_LOCK))
 			mode |= 0200;
 		break;
 	case hwmon_temp_crit:
 		if (!(config & JC42_CFG_TCRIT_LOCK))
 			mode |= 0200;
 		break;
 	case hwmon_temp_crit_hyst:
 		if (!(config & (JC42_CFG_EVENT_LOCK | JC42_CFG_TCRIT_LOCK)))
 			mode |= 0200;
 		break;
 	case hwmon_temp_input:
 	case hwmon_temp_max_hyst:
 	case hwmon_temp_min_alarm:
 	case hwmon_temp_max_alarm:
 	case hwmon_temp_crit_alarm:
 		break;
 	default:
 		mode = 0;
 		break;
 	}
 	return mode;
 }

 /* Return 0 if detection is successful, -ENODEV otherwise */
 static int jc42_detect(struct i2c_client *client, struct i2c_board_info *info)
 {
 	struct i2c_adapter *adapter = client->adapter;
 	int i, config, cap, manid, devid;

 	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
 				     I2C_FUNC_SMBUS_WORD_DATA))
 		return -ENODEV;

 	cap = i2c_smbus_read_word_swapped(client, JC42_REG_CAP);
 	config = i2c_smbus_read_word_swapped(client, JC42_REG_CONFIG);
 	manid = i2c_smbus_read_word_swapped(client, JC42_REG_MANID);
 	devid = i2c_smbus_read_word_swapped(client, JC42_REG_DEVICEID);

 	if (cap < 0 || config < 0 || manid < 0 || devid < 0)
 		return -ENODEV;

 	if ((cap & 0xff00) || (config & 0xf820))
 		return -ENODEV;

 	if ((devid & TSE2004_DEVID_MASK) == TSE2004_DEVID &&
 	    (cap & 0x0062) != 0x0062)
 		return -ENODEV;

 	for (i = 0; i < ARRAY_SIZE(jc42_chips); i++) {
 		struct jc42_chips *chip = &jc42_chips[i];
 		if (manid == chip->manid &&
 		    (devid & chip->devid_mask) == chip->devid) {
 			strscpy(info->type, "jc42", I2C_NAME_SIZE);
 			return 0;
 		}
 	}
 	return -ENODEV;
 }

 static const struct hwmon_channel_info * const jc42_info[] = {
 	HWMON_CHANNEL_INFO(chip,
 			   HWMON_C_REGISTER_TZ | HWMON_C_UPDATE_INTERVAL),
 	HWMON_CHANNEL_INFO(temp,
 			   HWMON_T_INPUT | HWMON_T_MIN | HWMON_T_MAX |
 			   HWMON_T_CRIT | HWMON_T_MAX_HYST |
 			   HWMON_T_CRIT_HYST | HWMON_T_MIN_ALARM |
 			   HWMON_T_MAX_ALARM | HWMON_T_CRIT_ALARM),
 	NULL
 };

 static const struct hwmon_ops jc42_hwmon_ops = {
 	.is_visible = jc42_is_visible,
 	.read = jc42_read,
 	.write = jc42_write,
 };

 static const struct hwmon_chip_info jc42_chip_info = {
 	.ops = &jc42_hwmon_ops,
 	.info = jc42_info,
 };

 static bool jc42_readable_reg(struct device *dev, unsigned int reg)
 {
 	return (reg >= JC42_REG_CAP && reg <= JC42_REG_DEVICEID) ||
 		reg == JC42_REG_SMBUS;
 }

 static bool jc42_writable_reg(struct device *dev, unsigned int reg)
 {
 	return (reg >= JC42_REG_CONFIG && reg <= JC42_REG_TEMP_CRITICAL) ||
 		reg == JC42_REG_SMBUS;
 }

 static bool jc42_volatile_reg(struct device *dev, unsigned int reg)
 {
 	return reg == JC42_REG_CONFIG || reg == JC42_REG_TEMP;
 }

 static const struct regmap_config jc42_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 16,
 	.val_format_endian = REGMAP_ENDIAN_BIG,
 	.max_register = JC42_REG_SMBUS,
 	.writeable_reg = jc42_writable_reg,
 	.readable_reg = jc42_readable_reg,
 	.volatile_reg = jc42_volatile_reg,
 	.cache_type = REGCACHE_MAPLE,
 };

 static int jc42_probe(struct i2c_client *client)
 {
 	struct device *dev = &client->dev;
 	struct device *hwmon_dev;
 	unsigned int config, cap;
 	struct jc42_data *data;
 	int ret;

 	data = devm_kzalloc(dev, sizeof(struct jc42_data), GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;

 	data->regmap = devm_regmap_init_i2c(client, &jc42_regmap_config);
 	if (IS_ERR(data->regmap))
 		return PTR_ERR(data->regmap);

 	i2c_set_clientdata(client, data);
 	mutex_init(&data->update_lock);

 	ret = regmap_read(data->regmap, JC42_REG_CAP, &cap);
 	if (ret)
 		return ret;

 	data->extended = !!(cap & JC42_CAP_RANGE);

 	if (device_property_read_bool(dev, "smbus-timeout-disable")) {
 		/*
 		 * Not all chips support this register, but from a
 		 * quick read of various datasheets no chip appears
 		 * incompatible with the below attempt to disable
 		 * the timeout. And the whole thing is opt-in...
 		 */
 		ret = regmap_set_bits(data->regmap, JC42_REG_SMBUS,
 				      SMBUS_STMOUT);
 		if (ret)
 			return ret;
 	}

 	ret = regmap_read(data->regmap, JC42_REG_CONFIG, &config);
 	if (ret)
 		return ret;

 	data->orig_config = config;
 	if (config & JC42_CFG_SHUTDOWN) {
 		config &= ~JC42_CFG_SHUTDOWN;
 		regmap_write(data->regmap, JC42_REG_CONFIG, config);
 	}
 	data->config = config;

 	hwmon_dev = devm_hwmon_device_register_with_info(dev, "jc42",
 							 data, &jc42_chip_info,
 							 NULL);
 	return PTR_ERR_OR_ZERO(hwmon_dev);
 }

 static void jc42_remove(struct i2c_client *client)
 {
 	struct jc42_data *data = i2c_get_clientdata(client);

 	/* Restore original configuration except hysteresis */
 	if ((data->config & ~JC42_CFG_HYST_MASK) !=
 	    (data->orig_config & ~JC42_CFG_HYST_MASK)) {
 		int config;

 		config = (data->orig_config & ~JC42_CFG_HYST_MASK)
 		  | (data->config & JC42_CFG_HYST_MASK);
 		regmap_write(data->regmap, JC42_REG_CONFIG, config);
 	}
 }

 #ifdef CONFIG_PM

 static int jc42_suspend(struct device *dev)
 {
 	struct jc42_data *data = dev_get_drvdata(dev);

 	data->config |= JC42_CFG_SHUTDOWN;
 	regmap_write(data->regmap, JC42_REG_CONFIG, data->config);

 	regcache_cache_only(data->regmap, true);
 	regcache_mark_dirty(data->regmap);

 	return 0;
 }

 static int jc42_resume(struct device *dev)
 {
 	struct jc42_data *data = dev_get_drvdata(dev);

 	regcache_cache_only(data->regmap, false);

 	data->config &= ~JC42_CFG_SHUTDOWN;
 	regmap_write(data->regmap, JC42_REG_CONFIG, data->config);

 	/* Restore cached register values to hardware */
 	return regcache_sync(data->regmap);
 }

 static const struct dev_pm_ops jc42_dev_pm_ops = {
 	.suspend = jc42_suspend,
 	.resume = jc42_resume,
 };

 #define JC42_DEV_PM_OPS (&jc42_dev_pm_ops)
 #else
 #define JC42_DEV_PM_OPS NULL
 #endif /* CONFIG_PM */

 static const struct i2c_device_id jc42_id[] = {
 	{ "jc42" },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, jc42_id);

 #ifdef CONFIG_OF
 static const struct of_device_id jc42_of_ids[] = {
 	{ .compatible = "jedec,jc-42.4-temp", },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, jc42_of_ids);
 #endif

 static struct i2c_driver jc42_driver = {
 	.class		= I2C_CLASS_HWMON,
 	.driver = {
 		.name	= "jc42",
 		.pm = JC42_DEV_PM_OPS,
 		.of_match_table = of_match_ptr(jc42_of_ids),
 	},
 	.probe		= jc42_probe,
 	.remove		= jc42_remove,
 	.id_table	= jc42_id,
 	.detect		= jc42_detect,
 	.address_list	= normal_i2c,
 };

 module_i2c_driver(jc42_driver);

 MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
 MODULE_DESCRIPTION("JC42 driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-or-later
	/*
	* jc42.c - driver for Jedec JC42.4 compliant temperature sensors
	*
	* Copyright (c) 2010 Ericsson AB.
	*
	* Derived from lm77.c by Andras BALI <drewie@freemail.hu>.
	*
	* JC42.4 compliant temperature sensors are typically used on memory modules.
	*/

	#include <linux/bitops.h>
	#include <linux/bitfield.h>
	#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/err.h>
	#include <linux/mutex.h>
	#include <linux/of.h>
	#include <linux/regmap.h>

	/* Addresses to scan */
	static const unsigned short normal_i2c[] = {
	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, I2C_CLIENT_END };

	/* JC42 registers. All registers are 16 bit. */
	#define JC42_REG_CAP 0x00
	#define JC42_REG_CONFIG 0x01
	#define JC42_REG_TEMP_UPPER 0x02
	#define JC42_REG_TEMP_LOWER 0x03
	#define JC42_REG_TEMP_CRITICAL 0x04
	#define JC42_REG_TEMP 0x05
	#define JC42_REG_MANID 0x06
	#define JC42_REG_DEVICEID 0x07
	#define JC42_REG_SMBUS 0x22 /* NXP and Atmel, possibly others? */

	/* Status bits in temperature register */
	#define JC42_ALARM_CRIT BIT(15)
	#define JC42_ALARM_MAX BIT(14)
	#define JC42_ALARM_MIN BIT(13)

	/* Configuration register defines */
	#define JC42_CFG_CRIT_ONLY BIT(2)
	#define JC42_CFG_TCRIT_LOCK BIT(6)
	#define JC42_CFG_EVENT_LOCK BIT(7)
	#define JC42_CFG_SHUTDOWN BIT(8)
	#define JC42_CFG_HYST_MASK GENMASK(10, 9)

	/* Capabilities */
	#define JC42_CAP_RANGE BIT(2)

	/* Manufacturer IDs */
	#define ADT_MANID 0x11d4 /* Analog Devices */
	#define ATMEL_MANID 0x001f /* Atmel */
	#define ATMEL_MANID2 0x1114 /* Atmel */
	#define MAX_MANID 0x004d /* Maxim */
	#define IDT_MANID 0x00b3 /* IDT */
	#define MCP_MANID 0x0054 /* Microchip */
	#define NXP_MANID 0x1131 /* NXP Semiconductors */
	#define ONS_MANID 0x1b09 /* ON Semiconductor */
	#define STM_MANID 0x104a /* ST Microelectronics */
	#define GT_MANID 0x1c68 /* Giantec */
	#define GT_MANID2 0x132d /* Giantec, 2nd mfg ID */
	#define SI_MANID 0x1c85 /* Seiko Instruments */

	/* SMBUS register */
	#define SMBUS_STMOUT BIT(7) /* SMBus time-out, active low */

	/* Supported chips */

	/* Analog Devices */
	#define ADT7408_DEVID 0x0801
	#define ADT7408_DEVID_MASK 0xffff

	/* Atmel */
	#define AT30TS00_DEVID 0x8201
	#define AT30TS00_DEVID_MASK 0xffff

	#define GT34TS02_DEVID 0x3300
	#define GT34TS02_DEVID_MASK 0xff00

	#define TS3000_DEVID 0x2900 /* Also matches TSE2002 */
	#define TS3000_DEVID_MASK 0xff00

	#define TS3001_DEVID 0x3000
	#define TS3001_DEVID_MASK 0xff00

	/* Maxim */
	#define MAX6604_DEVID 0x3e00
	#define MAX6604_DEVID_MASK 0xffff

	/* Microchip */
	#define MCP9804_DEVID 0x0200
	#define MCP9804_DEVID_MASK 0xfffc

	#define MCP9808_DEVID 0x0400
	#define MCP9808_DEVID_MASK 0xfffc

	#define MCP98242_DEVID 0x2000
	#define MCP98242_DEVID_MASK 0xfffc

	#define MCP98243_DEVID 0x2100
	#define MCP98243_DEVID_MASK 0xfffc

	#define MCP9843_DEVID 0x0000 /* Also matches mcp9805 */
	#define MCP9843_DEVID_MASK 0xfffe

	/* NXP */
	#define SE97_DEVID 0xa200
	#define SE97_DEVID_MASK 0xfffc

	#define SE98_DEVID 0xa100
	#define SE98_DEVID_MASK 0xfffc

	/* ON Semiconductor */
	#define CAT6095_DEVID 0x0800 /* Also matches CAT34TS02 */
	#define CAT6095_DEVID_MASK 0xffe0

	#define CAT34TS02C_DEVID 0x0a00
	#define CAT34TS02C_DEVID_MASK 0xfff0

	/* ST Microelectronics */
	#define STTS424_DEVID 0x0101
	#define STTS424_DEVID_MASK 0xffff

	#define STTS424E_DEVID 0x0000
	#define STTS424E_DEVID_MASK 0xfffe

	#define STTS2002_DEVID 0x0300
	#define STTS2002_DEVID_MASK 0xffff

	#define STTS3000_DEVID 0x0200
	#define STTS3000_DEVID_MASK 0xffff

	/* TSE2004 compliant sensors */
	#define TSE2004_DEVID 0x2200
	#define TSE2004_DEVID_MASK 0xff00

	static u16 jc42_hysteresis[] = { 0, 1500, 3000, 6000 };

	struct jc42_chips {
	u16 manid;
	u16 devid;
	u16 devid_mask;
	};

	static struct jc42_chips jc42_chips[] = {
	{ ADT_MANID, ADT7408_DEVID, ADT7408_DEVID_MASK },
	{ ATMEL_MANID, AT30TS00_DEVID, AT30TS00_DEVID_MASK },
	{ ATMEL_MANID2, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ GT_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ GT_MANID2, GT34TS02_DEVID, GT34TS02_DEVID_MASK },
	{ IDT_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ IDT_MANID, TS3000_DEVID, TS3000_DEVID_MASK },
	{ IDT_MANID, TS3001_DEVID, TS3001_DEVID_MASK },
	{ MAX_MANID, MAX6604_DEVID, MAX6604_DEVID_MASK },
	{ MCP_MANID, MCP9804_DEVID, MCP9804_DEVID_MASK },
	{ MCP_MANID, MCP9808_DEVID, MCP9808_DEVID_MASK },
	{ MCP_MANID, MCP98242_DEVID, MCP98242_DEVID_MASK },
	{ MCP_MANID, MCP98243_DEVID, MCP98243_DEVID_MASK },
	{ MCP_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ MCP_MANID, MCP9843_DEVID, MCP9843_DEVID_MASK },
	{ NXP_MANID, SE97_DEVID, SE97_DEVID_MASK },
	{ ONS_MANID, CAT6095_DEVID, CAT6095_DEVID_MASK },
	{ ONS_MANID, CAT34TS02C_DEVID, CAT34TS02C_DEVID_MASK },
	{ ONS_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ ONS_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ NXP_MANID, SE98_DEVID, SE98_DEVID_MASK },
	{ SI_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ STM_MANID, STTS424_DEVID, STTS424_DEVID_MASK },
	{ STM_MANID, STTS424E_DEVID, STTS424E_DEVID_MASK },
	{ STM_MANID, STTS2002_DEVID, STTS2002_DEVID_MASK },
	{ STM_MANID, TSE2004_DEVID, TSE2004_DEVID_MASK },
	{ STM_MANID, STTS3000_DEVID, STTS3000_DEVID_MASK },
	};

	/* Each client has this additional data */
	struct jc42_data {
	struct mutex update_lock; /* protect register access */
	struct regmap *regmap;
	bool extended; /* true if extended range supported */
	bool valid;
	u16 orig_config; /* original configuration */
	u16 config; /* current configuration */
	};

	#define JC42_TEMP_MIN_EXTENDED (-40000)
	#define JC42_TEMP_MIN 0
	#define JC42_TEMP_MAX 125000

	static u16 jc42_temp_to_reg(long temp, bool extended)
	{
	int ntemp = clamp_val(temp,
	extended ? JC42_TEMP_MIN_EXTENDED :
	JC42_TEMP_MIN, JC42_TEMP_MAX);

	/* convert from 0.001 to 0.0625 resolution */
	return (ntemp * 2 / 125) & 0x1fff;
	}

	static int jc42_temp_from_reg(s16 reg)
	{
	reg = sign_extend32(reg, 12);

	/* convert from 0.0625 to 0.001 resolution */
	return reg * 125 / 2;
	}

	static int jc42_read(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long *val)
	{
	struct jc42_data *data = dev_get_drvdata(dev);
	unsigned int regval;
	int ret, temp, hyst;

	mutex_lock(&data->update_lock);

	switch (attr) {
	case hwmon_temp_input:
	ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
	if (ret)
	break;

	*val = jc42_temp_from_reg(regval);
	break;
	case hwmon_temp_min:
	ret = regmap_read(data->regmap, JC42_REG_TEMP_LOWER, &regval);
	if (ret)
	break;

	*val = jc42_temp_from_reg(regval);
	break;
	case hwmon_temp_max:
	ret = regmap_read(data->regmap, JC42_REG_TEMP_UPPER, &regval);
	if (ret)
	break;

	*val = jc42_temp_from_reg(regval);
	break;
	case hwmon_temp_crit:
	ret = regmap_read(data->regmap, JC42_REG_TEMP_CRITICAL,
	&regval);
	if (ret)
	break;

	*val = jc42_temp_from_reg(regval);
	break;
	case hwmon_temp_max_hyst:
	ret = regmap_read(data->regmap, JC42_REG_TEMP_UPPER, &regval);
	if (ret)
	break;

	temp = jc42_temp_from_reg(regval);
	hyst = jc42_hysteresis[FIELD_GET(JC42_CFG_HYST_MASK,
	data->config)];
	*val = temp - hyst;
	break;
	case hwmon_temp_crit_hyst:
	ret = regmap_read(data->regmap, JC42_REG_TEMP_CRITICAL,
	&regval);
	if (ret)
	break;

	temp = jc42_temp_from_reg(regval);
	hyst = jc42_hysteresis[FIELD_GET(JC42_CFG_HYST_MASK,
	data->config)];
	*val = temp - hyst;
	break;
	case hwmon_temp_min_alarm:
	ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
	if (ret)
	break;

	*val = FIELD_GET(JC42_ALARM_MIN, regval);
	break;
	case hwmon_temp_max_alarm:
	ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
	if (ret)
	break;

	*val = FIELD_GET(JC42_ALARM_MAX, regval);
	break;
	case hwmon_temp_crit_alarm:
	ret = regmap_read(data->regmap, JC42_REG_TEMP, &regval);
	if (ret)
	break;

	*val = FIELD_GET(JC42_ALARM_CRIT, regval);
	break;
	default:
	ret = -EOPNOTSUPP;
	break;
	}

	mutex_unlock(&data->update_lock);

	return ret;
	}

	static int jc42_write(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long val)
	{
	struct jc42_data *data = dev_get_drvdata(dev);
	unsigned int regval;
	int diff, hyst;
	int ret;

	mutex_lock(&data->update_lock);

	switch (attr) {
	case hwmon_temp_min:
	ret = regmap_write(data->regmap, JC42_REG_TEMP_LOWER,
	jc42_temp_to_reg(val, data->extended));
	break;
	case hwmon_temp_max:
	ret = regmap_write(data->regmap, JC42_REG_TEMP_UPPER,
	jc42_temp_to_reg(val, data->extended));
	break;
	case hwmon_temp_crit:
	ret = regmap_write(data->regmap, JC42_REG_TEMP_CRITICAL,
	jc42_temp_to_reg(val, data->extended));
	break;
	case hwmon_temp_crit_hyst:
	ret = regmap_read(data->regmap, JC42_REG_TEMP_CRITICAL,
	&regval);
	if (ret)
	break;

	/*
	* JC42.4 compliant chips only support four hysteresis values.
	* Pick best choice and go from there.
	*/
	val = clamp_val(val, (data->extended ? JC42_TEMP_MIN_EXTENDED
	: JC42_TEMP_MIN) - 6000,
	JC42_TEMP_MAX);
	diff = jc42_temp_from_reg(regval) - val;
	hyst = 0;
	if (diff > 0) {
	if (diff < 2250)
	hyst = 1; /* 1.5 degrees C */
	else if (diff < 4500)
	hyst = 2; /* 3.0 degrees C */
	else
	hyst = 3; /* 6.0 degrees C */
	}
	data->config = (data->config & ~JC42_CFG_HYST_MASK) \|
	FIELD_PREP(JC42_CFG_HYST_MASK, hyst);
	ret = regmap_write(data->regmap, JC42_REG_CONFIG,
	data->config);
	break;
	default:
	ret = -EOPNOTSUPP;
	break;
	}

	mutex_unlock(&data->update_lock);

	return ret;
	}

	static umode_t jc42_is_visible(const void *_data, enum hwmon_sensor_types type,
	u32 attr, int channel)
	{
	const struct jc42_data *data = _data;
	unsigned int config = data->config;
	umode_t mode = 0444;

	switch (attr) {
	case hwmon_temp_min:
	case hwmon_temp_max:
	if (!(config & JC42_CFG_EVENT_LOCK))
	mode \|= 0200;
	break;
	case hwmon_temp_crit:
	if (!(config & JC42_CFG_TCRIT_LOCK))
	mode \|= 0200;
	break;
	case hwmon_temp_crit_hyst:
	if (!(config & (JC42_CFG_EVENT_LOCK \| JC42_CFG_TCRIT_LOCK)))
	mode \|= 0200;
	break;
	case hwmon_temp_input:
	case hwmon_temp_max_hyst:
	case hwmon_temp_min_alarm:
	case hwmon_temp_max_alarm:
	case hwmon_temp_crit_alarm:
	break;
	default:
	mode = 0;
	break;
	}
	return mode;
	}

	/* Return 0 if detection is successful, -ENODEV otherwise */
	static int jc42_detect(struct i2c_client client, struct i2c_board_info info)
	{
	struct i2c_adapter *adapter = client->adapter;
	int i, config, cap, manid, devid;

	if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA \|
	I2C_FUNC_SMBUS_WORD_DATA))
	return -ENODEV;

	cap = i2c_smbus_read_word_swapped(client, JC42_REG_CAP);
	config = i2c_smbus_read_word_swapped(client, JC42_REG_CONFIG);
	manid = i2c_smbus_read_word_swapped(client, JC42_REG_MANID);
	devid = i2c_smbus_read_word_swapped(client, JC42_REG_DEVICEID);

	if (cap < 0 \|\| config < 0 \|\| manid < 0 \|\| devid < 0)
	return -ENODEV;

	if ((cap & 0xff00) \|\| (config & 0xf820))
	return -ENODEV;

	if ((devid & TSE2004_DEVID_MASK) == TSE2004_DEVID &&
	(cap & 0x0062) != 0x0062)
	return -ENODEV;

	for (i = 0; i < ARRAY_SIZE(jc42_chips); i++) {
	struct jc42_chips *chip = &jc42_chips[i];
	if (manid == chip->manid &&
	(devid & chip->devid_mask) == chip->devid) {
	strscpy(info->type, "jc42", I2C_NAME_SIZE);
	return 0;
	}
	}
	return -ENODEV;
	}

	static const struct hwmon_channel_info * const jc42_info[] = {
	HWMON_CHANNEL_INFO(chip,
	HWMON_C_REGISTER_TZ \| HWMON_C_UPDATE_INTERVAL),
	HWMON_CHANNEL_INFO(temp,
	HWMON_T_INPUT \| HWMON_T_MIN \| HWMON_T_MAX \|
	HWMON_T_CRIT \| HWMON_T_MAX_HYST \|
	HWMON_T_CRIT_HYST \| HWMON_T_MIN_ALARM \|
	HWMON_T_MAX_ALARM \| HWMON_T_CRIT_ALARM),
	NULL
	};

	static const struct hwmon_ops jc42_hwmon_ops = {
	.is_visible = jc42_is_visible,
	.read = jc42_read,
	.write = jc42_write,
	};

	static const struct hwmon_chip_info jc42_chip_info = {
	.ops = &jc42_hwmon_ops,
	.info = jc42_info,
	};

	static bool jc42_readable_reg(struct device *dev, unsigned int reg)
	{
	return (reg >= JC42_REG_CAP && reg <= JC42_REG_DEVICEID) \|\|
	reg == JC42_REG_SMBUS;
	}

	static bool jc42_writable_reg(struct device *dev, unsigned int reg)
	{
	return (reg >= JC42_REG_CONFIG && reg <= JC42_REG_TEMP_CRITICAL) \|\|
	reg == JC42_REG_SMBUS;
	}

	static bool jc42_volatile_reg(struct device *dev, unsigned int reg)
	{
	return reg == JC42_REG_CONFIG \|\| reg == JC42_REG_TEMP;
	}

	static const struct regmap_config jc42_regmap_config = {
	.reg_bits = 8,
	.val_bits = 16,
	.val_format_endian = REGMAP_ENDIAN_BIG,
	.max_register = JC42_REG_SMBUS,
	.writeable_reg = jc42_writable_reg,
	.readable_reg = jc42_readable_reg,
	.volatile_reg = jc42_volatile_reg,
	.cache_type = REGCACHE_MAPLE,
	};

	static int jc42_probe(struct i2c_client *client)
	{
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	unsigned int config, cap;
	struct jc42_data *data;
	int ret;

	data = devm_kzalloc(dev, sizeof(struct jc42_data), GFP_KERNEL);
	if (!data)
	return -ENOMEM;

	data->regmap = devm_regmap_init_i2c(client, &jc42_regmap_config);
	if (IS_ERR(data->regmap))
	return PTR_ERR(data->regmap);

	i2c_set_clientdata(client, data);
	mutex_init(&data->update_lock);

	ret = regmap_read(data->regmap, JC42_REG_CAP, &cap);
	if (ret)
	return ret;

	data->extended = !!(cap & JC42_CAP_RANGE);

	if (device_property_read_bool(dev, "smbus-timeout-disable")) {
	/*
	* Not all chips support this register, but from a
	* quick read of various datasheets no chip appears
	* incompatible with the below attempt to disable
	* the timeout. And the whole thing is opt-in...
	*/
	ret = regmap_set_bits(data->regmap, JC42_REG_SMBUS,
	SMBUS_STMOUT);
	if (ret)
	return ret;
	}

	ret = regmap_read(data->regmap, JC42_REG_CONFIG, &config);
	if (ret)
	return ret;

	data->orig_config = config;
	if (config & JC42_CFG_SHUTDOWN) {
	config &= ~JC42_CFG_SHUTDOWN;
	regmap_write(data->regmap, JC42_REG_CONFIG, config);
	}
	data->config = config;

	hwmon_dev = devm_hwmon_device_register_with_info(dev, "jc42",
	data, &jc42_chip_info,
	NULL);
	return PTR_ERR_OR_ZERO(hwmon_dev);
	}

	static void jc42_remove(struct i2c_client *client)
	{
	struct jc42_data *data = i2c_get_clientdata(client);

	/* Restore original configuration except hysteresis */
	if ((data->config & ~JC42_CFG_HYST_MASK) !=
	(data->orig_config & ~JC42_CFG_HYST_MASK)) {
	int config;

	config = (data->orig_config & ~JC42_CFG_HYST_MASK)
	\| (data->config & JC42_CFG_HYST_MASK);
	regmap_write(data->regmap, JC42_REG_CONFIG, config);
	}
	}

	#ifdef CONFIG_PM

	static int jc42_suspend(struct device *dev)
	{
	struct jc42_data *data = dev_get_drvdata(dev);

	data->config \|= JC42_CFG_SHUTDOWN;
	regmap_write(data->regmap, JC42_REG_CONFIG, data->config);

	regcache_cache_only(data->regmap, true);
	regcache_mark_dirty(data->regmap);

	return 0;
	}

	static int jc42_resume(struct device *dev)
	{
	struct jc42_data *data = dev_get_drvdata(dev);

	regcache_cache_only(data->regmap, false);

	data->config &= ~JC42_CFG_SHUTDOWN;
	regmap_write(data->regmap, JC42_REG_CONFIG, data->config);

	/* Restore cached register values to hardware */
	return regcache_sync(data->regmap);
	}

	static const struct dev_pm_ops jc42_dev_pm_ops = {
	.suspend = jc42_suspend,
	.resume = jc42_resume,
	};

	#define JC42_DEV_PM_OPS (&jc42_dev_pm_ops)
	#else
	#define JC42_DEV_PM_OPS NULL
	#endif /* CONFIG_PM */

	static const struct i2c_device_id jc42_id[] = {
	{ "jc42" },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, jc42_id);

	#ifdef CONFIG_OF
	static const struct of_device_id jc42_of_ids[] = {
	{ .compatible = "jedec,jc-42.4-temp", },
	{ }
	};
	MODULE_DEVICE_TABLE(of, jc42_of_ids);
	#endif

	static struct i2c_driver jc42_driver = {
	.class = I2C_CLASS_HWMON,
	.driver = {
	.name = "jc42",
	.pm = JC42_DEV_PM_OPS,
	.of_match_table = of_match_ptr(jc42_of_ids),
	},
	.probe = jc42_probe,
	.remove = jc42_remove,
	.id_table = jc42_id,
	.detect = jc42_detect,
	.address_list = normal_i2c,
	};

	module_i2c_driver(jc42_driver);

	MODULE_AUTHOR("Guenter Roeck <linux@roeck-us.net>");
	MODULE_DESCRIPTION("JC42 driver");
	MODULE_LICENSE("GPL");