drivers/hwmon/ina238.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Driver for Texas Instruments INA238 power monitor chip
  * Datasheet: https://www.ti.com/product/ina238
  *
  * Copyright (C) 2021 Nathan Rossi <nathan.rossi@digi.com>
  */

 #include <linux/err.h>
 #include <linux/hwmon.h>
 #include <linux/i2c.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
 #include <linux/regmap.h>

 #include <linux/platform_data/ina2xx.h>

 /* INA238 register definitions */
 #define INA238_CONFIG			0x0
 #define INA238_ADC_CONFIG		0x1
 #define INA238_SHUNT_CALIBRATION	0x2
 #define INA238_SHUNT_VOLTAGE		0x4
 #define INA238_BUS_VOLTAGE		0x5
 #define INA238_DIE_TEMP			0x6
 #define INA238_CURRENT			0x7
 #define INA238_POWER			0x8
 #define INA238_DIAG_ALERT		0xb
 #define INA238_SHUNT_OVER_VOLTAGE	0xc
 #define INA238_SHUNT_UNDER_VOLTAGE	0xd
 #define INA238_BUS_OVER_VOLTAGE		0xe
 #define INA238_BUS_UNDER_VOLTAGE	0xf
 #define INA238_TEMP_LIMIT		0x10
 #define INA238_POWER_LIMIT		0x11
 #define INA238_DEVICE_ID		0x3f /* not available on INA237 */

 #define INA238_CONFIG_ADCRANGE		BIT(4)

 #define INA238_DIAG_ALERT_TMPOL		BIT(7)
 #define INA238_DIAG_ALERT_SHNTOL	BIT(6)
 #define INA238_DIAG_ALERT_SHNTUL	BIT(5)
 #define INA238_DIAG_ALERT_BUSOL		BIT(4)
 #define INA238_DIAG_ALERT_BUSUL		BIT(3)
 #define INA238_DIAG_ALERT_POL		BIT(2)

 #define INA238_REGISTERS		0x11

 #define INA238_RSHUNT_DEFAULT		10000 /* uOhm */

 /* Default configuration of device on reset. */
 #define INA238_CONFIG_DEFAULT		0
 /* 16 sample averaging, 1052us conversion time, continuous mode */
 #define INA238_ADC_CONFIG_DEFAULT	0xfb6a
 /* Configure alerts to be based on averaged value (SLOWALERT) */
 #define INA238_DIAG_ALERT_DEFAULT	0x2000
 /*
  * This driver uses a fixed calibration value in order to scale current/power
  * based on a fixed shunt resistor value. This allows for conversion within the
  * device to avoid integer limits whilst current/power accuracy is scaled
  * relative to the shunt resistor value within the driver. This is similar to
  * how the ina2xx driver handles current/power scaling.
  *
  * The end result of this is that increasing shunt values (from a fixed 20 mOhm
  * shunt) increase the effective current/power accuracy whilst limiting the
  * range and decreasing shunt values decrease the effective accuracy but
  * increase the range.
  *
  * The value of the Current register is calculated given the following:
  *   Current (A) = (shunt voltage register * 5) * calibration / 81920
  *
  * The maximum shunt voltage is 163.835 mV (0x7fff, ADC_RANGE = 0, gain = 4).
  * With the maximum current value of 0x7fff and a fixed shunt value results in
  * a calibration value of 16384 (0x4000).
  *
  *   0x7fff = (0x7fff * 5) * calibration / 81920
  *   calibration = 0x4000
  *
  * Equivalent calibration is applied for the Power register (maximum value for
  * bus voltage is 102396.875 mV, 0x7fff), where the maximum power that can
  * occur is ~16776192 uW (register value 0x147a8):
  *
  * This scaling means the resulting values for Current and Power registers need
  * to be scaled by the difference between the fixed shunt resistor and the
  * actual shunt resistor:
  *
  *  shunt = 0x4000 / (819.2 * 10^6) / 0.001 = 20000 uOhms (with 1mA/lsb)
  *
  *  Current (mA) = register value * 20000 / rshunt / 4 * gain
  *  Power (W) = 0.2 * register value * 20000 / rshunt / 4 * gain
  */
 #define INA238_CALIBRATION_VALUE	16384
 #define INA238_FIXED_SHUNT		20000

 #define INA238_SHUNT_VOLTAGE_LSB	5 /* 5 uV/lsb */
 #define INA238_BUS_VOLTAGE_LSB		3125 /* 3.125 mV/lsb */
 #define INA238_DIE_TEMP_LSB		125 /* 125 mC/lsb */

 static const struct regmap_config ina238_regmap_config = {
 	.max_register = INA238_REGISTERS,
 	.reg_bits = 8,
 	.val_bits = 16,
 };

 struct ina238_data {
 	struct i2c_client *client;
 	struct mutex config_lock;
 	struct regmap *regmap;
 	u32 rshunt;
 	int gain;
 };

 static int ina238_read_reg24(const struct i2c_client *client, u8 reg, u32 *val)
 {
 	u8 data[3];
 	int err;

 	/* 24-bit register read */
 	err = i2c_smbus_read_i2c_block_data(client, reg, 3, data);
 	if (err < 0)
 		return err;
 	if (err != 3)
 		return -EIO;
 	*val = (data[0] << 16) | (data[1] << 8) | data[2];

 	return 0;
 }

 static int ina238_read_in(struct device *dev, u32 attr, int channel,
 			  long *val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	int reg, mask;
 	int regval;
 	int err;

 	switch (channel) {
 	case 0:
 		switch (attr) {
 		case hwmon_in_input:
 			reg = INA238_SHUNT_VOLTAGE;
 			break;
 		case hwmon_in_max:
 			reg = INA238_SHUNT_OVER_VOLTAGE;
 			break;
 		case hwmon_in_min:
 			reg = INA238_SHUNT_UNDER_VOLTAGE;
 			break;
 		case hwmon_in_max_alarm:
 			reg = INA238_DIAG_ALERT;
 			mask = INA238_DIAG_ALERT_SHNTOL;
 			break;
 		case hwmon_in_min_alarm:
 			reg = INA238_DIAG_ALERT;
 			mask = INA238_DIAG_ALERT_SHNTUL;
 			break;
 		default:
 			return -EOPNOTSUPP;
 		}
 		break;
 	case 1:
 		switch (attr) {
 		case hwmon_in_input:
 			reg = INA238_BUS_VOLTAGE;
 			break;
 		case hwmon_in_max:
 			reg = INA238_BUS_OVER_VOLTAGE;
 			break;
 		case hwmon_in_min:
 			reg = INA238_BUS_UNDER_VOLTAGE;
 			break;
 		case hwmon_in_max_alarm:
 			reg = INA238_DIAG_ALERT;
 			mask = INA238_DIAG_ALERT_BUSOL;
 			break;
 		case hwmon_in_min_alarm:
 			reg = INA238_DIAG_ALERT;
 			mask = INA238_DIAG_ALERT_BUSUL;
 			break;
 		default:
 			return -EOPNOTSUPP;
 		}
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	err = regmap_read(data->regmap, reg, &regval);
 	if (err < 0)
 		return err;

 	switch (attr) {
 	case hwmon_in_input:
 	case hwmon_in_max:
 	case hwmon_in_min:
 		/* signed register, value in mV */
 		regval = (s16)regval;
 		if (channel == 0)
 			/* gain of 1 -> LSB / 4 */
 			*val = (regval * INA238_SHUNT_VOLTAGE_LSB) /
 			       (1000 * (4 - data->gain + 1));
 		else
 			*val = (regval * INA238_BUS_VOLTAGE_LSB) / 1000;
 		break;
 	case hwmon_in_max_alarm:
 	case hwmon_in_min_alarm:
 		*val = !!(regval & mask);
 		break;
 	}

 	return 0;
 }

 static int ina238_write_in(struct device *dev, u32 attr, int channel,
 			   long val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	int regval;

 	if (attr != hwmon_in_max && attr != hwmon_in_min)
 		return -EOPNOTSUPP;

 	/* convert decimal to register value */
 	switch (channel) {
 	case 0:
 		/* signed value, clamp to max range +/-163 mV */
 		regval = clamp_val(val, -163, 163);
 		regval = (regval * 1000 * (4 - data->gain + 1)) /
 			 INA238_SHUNT_VOLTAGE_LSB;
 		regval = clamp_val(regval, S16_MIN, S16_MAX);

 		switch (attr) {
 		case hwmon_in_max:
 			return regmap_write(data->regmap,
 					    INA238_SHUNT_OVER_VOLTAGE, regval);
 		case hwmon_in_min:
 			return regmap_write(data->regmap,
 					    INA238_SHUNT_UNDER_VOLTAGE, regval);
 		default:
 			return -EOPNOTSUPP;
 		}
 	case 1:
 		/* signed value, positive values only. Clamp to max 102.396 V */
 		regval = clamp_val(val, 0, 102396);
 		regval = (regval * 1000) / INA238_BUS_VOLTAGE_LSB;
 		regval = clamp_val(regval, 0, S16_MAX);

 		switch (attr) {
 		case hwmon_in_max:
 			return regmap_write(data->regmap,
 					    INA238_BUS_OVER_VOLTAGE, regval);
 		case hwmon_in_min:
 			return regmap_write(data->regmap,
 					    INA238_BUS_UNDER_VOLTAGE, regval);
 		default:
 			return -EOPNOTSUPP;
 		}
 	default:
 		return -EOPNOTSUPP;
 	}
 }

 static int ina238_read_current(struct device *dev, u32 attr, long *val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	int regval;
 	int err;

 	switch (attr) {
 	case hwmon_curr_input:
 		err = regmap_read(data->regmap, INA238_CURRENT, &regval);
 		if (err < 0)
 			return err;

 		/* Signed register, fixed 1mA current lsb. result in mA */
 		*val = div_s64((s16)regval * INA238_FIXED_SHUNT * data->gain,
 			       data->rshunt * 4);
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static int ina238_read_power(struct device *dev, u32 attr, long *val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	long long power;
 	int regval;
 	int err;

 	switch (attr) {
 	case hwmon_power_input:
 		err = ina238_read_reg24(data->client, INA238_POWER, &regval);
 		if (err)
 			return err;

 		/* Fixed 1mA lsb, scaled by 1000000 to have result in uW */
 		power = div_u64(regval * 1000ULL * INA238_FIXED_SHUNT *
 				data->gain, 20 * data->rshunt);
 		/* Clamp value to maximum value of long */
 		*val = clamp_val(power, 0, LONG_MAX);
 		break;
 	case hwmon_power_max:
 		err = regmap_read(data->regmap, INA238_POWER_LIMIT, &regval);
 		if (err)
 			return err;

 		/*
 		 * Truncated 24-bit compare register, lower 8-bits are
 		 * truncated. Same conversion to/from uW as POWER register.
 		 */
 		power = div_u64((regval << 8) * 1000ULL * INA238_FIXED_SHUNT *
 			       data->gain, 20 * data->rshunt);
 		/* Clamp value to maximum value of long */
 		*val = clamp_val(power, 0, LONG_MAX);
 		break;
 	case hwmon_power_max_alarm:
 		err = regmap_read(data->regmap, INA238_DIAG_ALERT, &regval);
 		if (err)
 			return err;

 		*val = !!(regval & INA238_DIAG_ALERT_POL);
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static int ina238_write_power(struct device *dev, u32 attr, long val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	long regval;

 	if (attr != hwmon_power_max)
 		return -EOPNOTSUPP;

 	/*
 	 * Unsigned postive values. Compared against the 24-bit power register,
 	 * lower 8-bits are truncated. Same conversion to/from uW as POWER
 	 * register.
 	 */
 	regval = clamp_val(val, 0, LONG_MAX);
 	regval = div_u64(val * 20ULL * data->rshunt,
 			 1000ULL * INA238_FIXED_SHUNT * data->gain);
 	regval = clamp_val(regval >> 8, 0, U16_MAX);

 	return regmap_write(data->regmap, INA238_POWER_LIMIT, regval);
 }

 static int ina238_read_temp(struct device *dev, u32 attr, long *val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	int regval;
 	int err;

 	switch (attr) {
 	case hwmon_temp_input:
 		err = regmap_read(data->regmap, INA238_DIE_TEMP, &regval);
 		if (err)
 			return err;

 		/* Signed, bits 15-4 of register, result in mC */
 		*val = ((s16)regval >> 4) * INA238_DIE_TEMP_LSB;
 		break;
 	case hwmon_temp_max:
 		err = regmap_read(data->regmap, INA238_TEMP_LIMIT, &regval);
 		if (err)
 			return err;

 		/* Signed, bits 15-4 of register, result in mC */
 		*val = ((s16)regval >> 4) * INA238_DIE_TEMP_LSB;
 		break;
 	case hwmon_temp_max_alarm:
 		err = regmap_read(data->regmap, INA238_DIAG_ALERT, &regval);
 		if (err)
 			return err;

 		*val = !!(regval & INA238_DIAG_ALERT_TMPOL);
 		break;
 	default:
 		return -EOPNOTSUPP;
 	}

 	return 0;
 }

 static int ina238_write_temp(struct device *dev, u32 attr, long val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	int regval;

 	if (attr != hwmon_temp_max)
 		return -EOPNOTSUPP;

 	/* Signed, bits 15-4 of register */
 	regval = (val / INA238_DIE_TEMP_LSB) << 4;
 	regval = clamp_val(regval, S16_MIN, S16_MAX) & 0xfff0;

 	return regmap_write(data->regmap, INA238_TEMP_LIMIT, regval);
 }

 static int ina238_read(struct device *dev, enum hwmon_sensor_types type,
 		       u32 attr, int channel, long *val)
 {
 	switch (type) {
 	case hwmon_in:
 		return ina238_read_in(dev, attr, channel, val);
 	case hwmon_curr:
 		return ina238_read_current(dev, attr, val);
 	case hwmon_power:
 		return ina238_read_power(dev, attr, val);
 	case hwmon_temp:
 		return ina238_read_temp(dev, attr, val);
 	default:
 		return -EOPNOTSUPP;
 	}
 	return 0;
 }

 static int ina238_write(struct device *dev, enum hwmon_sensor_types type,
 		       u32 attr, int channel, long val)
 {
 	struct ina238_data *data = dev_get_drvdata(dev);
 	int err;

 	mutex_lock(&data->config_lock);

 	switch (type) {
 	case hwmon_in:
 		err = ina238_write_in(dev, attr, channel, val);
 		break;
 	case hwmon_power:
 		err = ina238_write_power(dev, attr, val);
 		break;
 	case hwmon_temp:
 		err = ina238_write_temp(dev, attr, val);
 		break;
 	default:
 		err = -EOPNOTSUPP;
 		break;
 	}

 	mutex_unlock(&data->config_lock);
 	return err;
 }

 static umode_t ina238_is_visible(const void *drvdata,
 				 enum hwmon_sensor_types type,
 				 u32 attr, int channel)
 {
 	switch (type) {
 	case hwmon_in:
 		switch (attr) {
 		case hwmon_in_input:
 		case hwmon_in_max_alarm:
 		case hwmon_in_min_alarm:
 			return 0444;
 		case hwmon_in_max:
 		case hwmon_in_min:
 			return 0644;
 		default:
 			return 0;
 		}
 	case hwmon_curr:
 		switch (attr) {
 		case hwmon_curr_input:
 			return 0444;
 		default:
 			return 0;
 		}
 	case hwmon_power:
 		switch (attr) {
 		case hwmon_power_input:
 		case hwmon_power_max_alarm:
 			return 0444;
 		case hwmon_power_max:
 			return 0644;
 		default:
 			return 0;
 		}
 	case hwmon_temp:
 		switch (attr) {
 		case hwmon_temp_input:
 		case hwmon_temp_max_alarm:
 			return 0444;
 		case hwmon_temp_max:
 			return 0644;
 		default:
 			return 0;
 		}
 	default:
 		return 0;
 	}
 }

 #define INA238_HWMON_IN_CONFIG (HWMON_I_INPUT | \
 				HWMON_I_MAX | HWMON_I_MAX_ALARM | \
 				HWMON_I_MIN | HWMON_I_MIN_ALARM)

 static const struct hwmon_channel_info * const ina238_info[] = {
 	HWMON_CHANNEL_INFO(in,
 			   /* 0: shunt voltage */
 			   INA238_HWMON_IN_CONFIG,
 			   /* 1: bus voltage */
 			   INA238_HWMON_IN_CONFIG),
 	HWMON_CHANNEL_INFO(curr,
 			   /* 0: current through shunt */
 			   HWMON_C_INPUT),
 	HWMON_CHANNEL_INFO(power,
 			   /* 0: power */
 			   HWMON_P_INPUT | HWMON_P_MAX | HWMON_P_MAX_ALARM),
 	HWMON_CHANNEL_INFO(temp,
 			   /* 0: die temperature */
 			   HWMON_T_INPUT | HWMON_T_MAX | HWMON_T_MAX_ALARM),
 	NULL
 };

 static const struct hwmon_ops ina238_hwmon_ops = {
 	.is_visible = ina238_is_visible,
 	.read = ina238_read,
 	.write = ina238_write,
 };

 static const struct hwmon_chip_info ina238_chip_info = {
 	.ops = &ina238_hwmon_ops,
 	.info = ina238_info,
 };

 static int ina238_probe(struct i2c_client *client)
 {
 	struct ina2xx_platform_data *pdata = dev_get_platdata(&client->dev);
 	struct device *dev = &client->dev;
 	struct device *hwmon_dev;
 	struct ina238_data *data;
 	int config;
 	int ret;

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

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

 	data->regmap = devm_regmap_init_i2c(client, &ina238_regmap_config);
 	if (IS_ERR(data->regmap)) {
 		dev_err(dev, "failed to allocate register map\n");
 		return PTR_ERR(data->regmap);
 	}

 	/* load shunt value */
 	data->rshunt = INA238_RSHUNT_DEFAULT;
 	if (device_property_read_u32(dev, "shunt-resistor", &data->rshunt) < 0 && pdata)
 		data->rshunt = pdata->shunt_uohms;
 	if (data->rshunt == 0) {
 		dev_err(dev, "invalid shunt resister value %u\n", data->rshunt);
 		return -EINVAL;
 	}

 	/* load shunt gain value */
 	if (device_property_read_u32(dev, "ti,shunt-gain", &data->gain) < 0)
 		data->gain = 4; /* Default of ADCRANGE = 0 */
 	if (data->gain != 1 && data->gain != 4) {
 		dev_err(dev, "invalid shunt gain value %u\n", data->gain);
 		return -EINVAL;
 	}

 	/* Setup CONFIG register */
 	config = INA238_CONFIG_DEFAULT;
 	if (data->gain == 1)
 		config |= INA238_CONFIG_ADCRANGE; /* ADCRANGE = 1 is /1 */
 	ret = regmap_write(data->regmap, INA238_CONFIG, config);
 	if (ret < 0) {
 		dev_err(dev, "error configuring the device: %d\n", ret);
 		return -ENODEV;
 	}

 	/* Setup ADC_CONFIG register */
 	ret = regmap_write(data->regmap, INA238_ADC_CONFIG,
 			   INA238_ADC_CONFIG_DEFAULT);
 	if (ret < 0) {
 		dev_err(dev, "error configuring the device: %d\n", ret);
 		return -ENODEV;
 	}

 	/* Setup SHUNT_CALIBRATION register with fixed value */
 	ret = regmap_write(data->regmap, INA238_SHUNT_CALIBRATION,
 			   INA238_CALIBRATION_VALUE);
 	if (ret < 0) {
 		dev_err(dev, "error configuring the device: %d\n", ret);
 		return -ENODEV;
 	}

 	/* Setup alert/alarm configuration */
 	ret = regmap_write(data->regmap, INA238_DIAG_ALERT,
 			   INA238_DIAG_ALERT_DEFAULT);
 	if (ret < 0) {
 		dev_err(dev, "error configuring the device: %d\n", ret);
 		return -ENODEV;
 	}

 	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data,
 							 &ina238_chip_info,
 							 NULL);
 	if (IS_ERR(hwmon_dev))
 		return PTR_ERR(hwmon_dev);

 	dev_info(dev, "power monitor %s (Rshunt = %u uOhm, gain = %u)\n",
 		 client->name, data->rshunt, data->gain);

 	return 0;
 }

 static const struct i2c_device_id ina238_id[] = {
 	{ "ina238" },
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, ina238_id);

 static const struct of_device_id __maybe_unused ina238_of_match[] = {
 	{ .compatible = "ti,ina237" },
 	{ .compatible = "ti,ina238" },
 	{ },
 };
 MODULE_DEVICE_TABLE(of, ina238_of_match);

 static struct i2c_driver ina238_driver = {
 	.driver = {
 		.name	= "ina238",
 		.of_match_table = of_match_ptr(ina238_of_match),
 	},
 	.probe		= ina238_probe,
 	.id_table	= ina238_id,
 };

 module_i2c_driver(ina238_driver);

 MODULE_AUTHOR("Nathan Rossi <nathan.rossi@digi.com>");
 MODULE_DESCRIPTION("ina238 driver");
 MODULE_LICENSE("GPL");
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Driver for Texas Instruments INA238 power monitor chip
	* Datasheet: https://www.ti.com/product/ina238
	*
	* Copyright (C) 2021 Nathan Rossi <nathan.rossi@digi.com>
	*/

	#include <linux/err.h>
	#include <linux/hwmon.h>
	#include <linux/i2c.h>
	#include <linux/init.h>
	#include <linux/kernel.h>
	#include <linux/module.h>
	#include <linux/of.h>
	#include <linux/regmap.h>

	#include <linux/platform_data/ina2xx.h>

	/* INA238 register definitions */
	#define INA238_CONFIG 0x0
	#define INA238_ADC_CONFIG 0x1
	#define INA238_SHUNT_CALIBRATION 0x2
	#define INA238_SHUNT_VOLTAGE 0x4
	#define INA238_BUS_VOLTAGE 0x5
	#define INA238_DIE_TEMP 0x6
	#define INA238_CURRENT 0x7
	#define INA238_POWER 0x8
	#define INA238_DIAG_ALERT 0xb
	#define INA238_SHUNT_OVER_VOLTAGE 0xc
	#define INA238_SHUNT_UNDER_VOLTAGE 0xd
	#define INA238_BUS_OVER_VOLTAGE 0xe
	#define INA238_BUS_UNDER_VOLTAGE 0xf
	#define INA238_TEMP_LIMIT 0x10
	#define INA238_POWER_LIMIT 0x11
	#define INA238_DEVICE_ID 0x3f /* not available on INA237 */

	#define INA238_CONFIG_ADCRANGE BIT(4)

	#define INA238_DIAG_ALERT_TMPOL BIT(7)
	#define INA238_DIAG_ALERT_SHNTOL BIT(6)
	#define INA238_DIAG_ALERT_SHNTUL BIT(5)
	#define INA238_DIAG_ALERT_BUSOL BIT(4)
	#define INA238_DIAG_ALERT_BUSUL BIT(3)
	#define INA238_DIAG_ALERT_POL BIT(2)

	#define INA238_REGISTERS 0x11

	#define INA238_RSHUNT_DEFAULT 10000 /* uOhm */

	/* Default configuration of device on reset. */
	#define INA238_CONFIG_DEFAULT 0
	/* 16 sample averaging, 1052us conversion time, continuous mode */
	#define INA238_ADC_CONFIG_DEFAULT 0xfb6a
	/* Configure alerts to be based on averaged value (SLOWALERT) */
	#define INA238_DIAG_ALERT_DEFAULT 0x2000
	/*
	* This driver uses a fixed calibration value in order to scale current/power
	* based on a fixed shunt resistor value. This allows for conversion within the
	* device to avoid integer limits whilst current/power accuracy is scaled
	* relative to the shunt resistor value within the driver. This is similar to
	* how the ina2xx driver handles current/power scaling.
	*
	* The end result of this is that increasing shunt values (from a fixed 20 mOhm
	* shunt) increase the effective current/power accuracy whilst limiting the
	* range and decreasing shunt values decrease the effective accuracy but
	* increase the range.
	*
	* The value of the Current register is calculated given the following:
	* Current (A) = (shunt voltage register * 5) * calibration / 81920
	*
	* The maximum shunt voltage is 163.835 mV (0x7fff, ADC_RANGE = 0, gain = 4).
	* With the maximum current value of 0x7fff and a fixed shunt value results in
	* a calibration value of 16384 (0x4000).
	*
	* 0x7fff = (0x7fff * 5) * calibration / 81920
	* calibration = 0x4000
	*
	* Equivalent calibration is applied for the Power register (maximum value for
	* bus voltage is 102396.875 mV, 0x7fff), where the maximum power that can
	* occur is ~16776192 uW (register value 0x147a8):
	*
	* This scaling means the resulting values for Current and Power registers need
	* to be scaled by the difference between the fixed shunt resistor and the
	* actual shunt resistor:
	*
	* shunt = 0x4000 / (819.2 * 10^6) / 0.001 = 20000 uOhms (with 1mA/lsb)
	*
	* Current (mA) = register value * 20000 / rshunt / 4 * gain
	* Power (W) = 0.2 * register value * 20000 / rshunt / 4 * gain
	*/
	#define INA238_CALIBRATION_VALUE 16384
	#define INA238_FIXED_SHUNT 20000

	#define INA238_SHUNT_VOLTAGE_LSB 5 /* 5 uV/lsb */
	#define INA238_BUS_VOLTAGE_LSB 3125 /* 3.125 mV/lsb */
	#define INA238_DIE_TEMP_LSB 125 /* 125 mC/lsb */

	static const struct regmap_config ina238_regmap_config = {
	.max_register = INA238_REGISTERS,
	.reg_bits = 8,
	.val_bits = 16,
	};

	struct ina238_data {
	struct i2c_client *client;
	struct mutex config_lock;
	struct regmap *regmap;
	u32 rshunt;
	int gain;
	};

	static int ina238_read_reg24(const struct i2c_client client, u8 reg, u32 val)
	{
	u8 data[3];
	int err;

	/* 24-bit register read */
	err = i2c_smbus_read_i2c_block_data(client, reg, 3, data);
	if (err < 0)
	return err;
	if (err != 3)
	return -EIO;
	*val = (data[0] << 16) \| (data[1] << 8) \| data[2];

	return 0;
	}

	static int ina238_read_in(struct device *dev, u32 attr, int channel,
	long *val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	int reg, mask;
	int regval;
	int err;

	switch (channel) {
	case 0:
	switch (attr) {
	case hwmon_in_input:
	reg = INA238_SHUNT_VOLTAGE;
	break;
	case hwmon_in_max:
	reg = INA238_SHUNT_OVER_VOLTAGE;
	break;
	case hwmon_in_min:
	reg = INA238_SHUNT_UNDER_VOLTAGE;
	break;
	case hwmon_in_max_alarm:
	reg = INA238_DIAG_ALERT;
	mask = INA238_DIAG_ALERT_SHNTOL;
	break;
	case hwmon_in_min_alarm:
	reg = INA238_DIAG_ALERT;
	mask = INA238_DIAG_ALERT_SHNTUL;
	break;
	default:
	return -EOPNOTSUPP;
	}
	break;
	case 1:
	switch (attr) {
	case hwmon_in_input:
	reg = INA238_BUS_VOLTAGE;
	break;
	case hwmon_in_max:
	reg = INA238_BUS_OVER_VOLTAGE;
	break;
	case hwmon_in_min:
	reg = INA238_BUS_UNDER_VOLTAGE;
	break;
	case hwmon_in_max_alarm:
	reg = INA238_DIAG_ALERT;
	mask = INA238_DIAG_ALERT_BUSOL;
	break;
	case hwmon_in_min_alarm:
	reg = INA238_DIAG_ALERT;
	mask = INA238_DIAG_ALERT_BUSUL;
	break;
	default:
	return -EOPNOTSUPP;
	}
	break;
	default:
	return -EOPNOTSUPP;
	}

	err = regmap_read(data->regmap, reg, &regval);
	if (err < 0)
	return err;

	switch (attr) {
	case hwmon_in_input:
	case hwmon_in_max:
	case hwmon_in_min:
	/* signed register, value in mV */
	regval = (s16)regval;
	if (channel == 0)
	/* gain of 1 -> LSB / 4 */
	val = (regval INA238_SHUNT_VOLTAGE_LSB) /
	(1000 * (4 - data->gain + 1));
	else
	val = (regval INA238_BUS_VOLTAGE_LSB) / 1000;
	break;
	case hwmon_in_max_alarm:
	case hwmon_in_min_alarm:
	*val = !!(regval & mask);
	break;
	}

	return 0;
	}

	static int ina238_write_in(struct device *dev, u32 attr, int channel,
	long val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	int regval;

	if (attr != hwmon_in_max && attr != hwmon_in_min)
	return -EOPNOTSUPP;

	/* convert decimal to register value */
	switch (channel) {
	case 0:
	/* signed value, clamp to max range +/-163 mV */
	regval = clamp_val(val, -163, 163);
	regval = (regval * 1000 * (4 - data->gain + 1)) /
	INA238_SHUNT_VOLTAGE_LSB;
	regval = clamp_val(regval, S16_MIN, S16_MAX);

	switch (attr) {
	case hwmon_in_max:
	return regmap_write(data->regmap,
	INA238_SHUNT_OVER_VOLTAGE, regval);
	case hwmon_in_min:
	return regmap_write(data->regmap,
	INA238_SHUNT_UNDER_VOLTAGE, regval);
	default:
	return -EOPNOTSUPP;
	}
	case 1:
	/* signed value, positive values only. Clamp to max 102.396 V */
	regval = clamp_val(val, 0, 102396);
	regval = (regval * 1000) / INA238_BUS_VOLTAGE_LSB;
	regval = clamp_val(regval, 0, S16_MAX);

	switch (attr) {
	case hwmon_in_max:
	return regmap_write(data->regmap,
	INA238_BUS_OVER_VOLTAGE, regval);
	case hwmon_in_min:
	return regmap_write(data->regmap,
	INA238_BUS_UNDER_VOLTAGE, regval);
	default:
	return -EOPNOTSUPP;
	}
	default:
	return -EOPNOTSUPP;
	}
	}

	static int ina238_read_current(struct device dev, u32 attr, long val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	int regval;
	int err;

	switch (attr) {
	case hwmon_curr_input:
	err = regmap_read(data->regmap, INA238_CURRENT, &regval);
	if (err < 0)
	return err;

	/* Signed register, fixed 1mA current lsb. result in mA */
	val = div_s64((s16)regval INA238_FIXED_SHUNT * data->gain,
	data->rshunt * 4);
	break;
	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static int ina238_read_power(struct device dev, u32 attr, long val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	long long power;
	int regval;
	int err;

	switch (attr) {
	case hwmon_power_input:
	err = ina238_read_reg24(data->client, INA238_POWER, &regval);
	if (err)
	return err;

	/* Fixed 1mA lsb, scaled by 1000000 to have result in uW */
	power = div_u64(regval * 1000ULL * INA238_FIXED_SHUNT *
	data->gain, 20 * data->rshunt);
	/* Clamp value to maximum value of long */
	*val = clamp_val(power, 0, LONG_MAX);
	break;
	case hwmon_power_max:
	err = regmap_read(data->regmap, INA238_POWER_LIMIT, &regval);
	if (err)
	return err;

	/*
	* Truncated 24-bit compare register, lower 8-bits are
	* truncated. Same conversion to/from uW as POWER register.
	*/
	power = div_u64((regval << 8) * 1000ULL * INA238_FIXED_SHUNT *
	data->gain, 20 * data->rshunt);
	/* Clamp value to maximum value of long */
	*val = clamp_val(power, 0, LONG_MAX);
	break;
	case hwmon_power_max_alarm:
	err = regmap_read(data->regmap, INA238_DIAG_ALERT, &regval);
	if (err)
	return err;

	*val = !!(regval & INA238_DIAG_ALERT_POL);
	break;
	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static int ina238_write_power(struct device *dev, u32 attr, long val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	long regval;

	if (attr != hwmon_power_max)
	return -EOPNOTSUPP;

	/*
	* Unsigned postive values. Compared against the 24-bit power register,
	* lower 8-bits are truncated. Same conversion to/from uW as POWER
	* register.
	*/
	regval = clamp_val(val, 0, LONG_MAX);
	regval = div_u64(val * 20ULL * data->rshunt,
	1000ULL * INA238_FIXED_SHUNT * data->gain);
	regval = clamp_val(regval >> 8, 0, U16_MAX);

	return regmap_write(data->regmap, INA238_POWER_LIMIT, regval);
	}

	static int ina238_read_temp(struct device dev, u32 attr, long val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	int regval;
	int err;

	switch (attr) {
	case hwmon_temp_input:
	err = regmap_read(data->regmap, INA238_DIE_TEMP, &regval);
	if (err)
	return err;

	/* Signed, bits 15-4 of register, result in mC */
	val = ((s16)regval >> 4) INA238_DIE_TEMP_LSB;
	break;
	case hwmon_temp_max:
	err = regmap_read(data->regmap, INA238_TEMP_LIMIT, &regval);
	if (err)
	return err;

	/* Signed, bits 15-4 of register, result in mC */
	val = ((s16)regval >> 4) INA238_DIE_TEMP_LSB;
	break;
	case hwmon_temp_max_alarm:
	err = regmap_read(data->regmap, INA238_DIAG_ALERT, &regval);
	if (err)
	return err;

	*val = !!(regval & INA238_DIAG_ALERT_TMPOL);
	break;
	default:
	return -EOPNOTSUPP;
	}

	return 0;
	}

	static int ina238_write_temp(struct device *dev, u32 attr, long val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	int regval;

	if (attr != hwmon_temp_max)
	return -EOPNOTSUPP;

	/* Signed, bits 15-4 of register */
	regval = (val / INA238_DIE_TEMP_LSB) << 4;
	regval = clamp_val(regval, S16_MIN, S16_MAX) & 0xfff0;

	return regmap_write(data->regmap, INA238_TEMP_LIMIT, regval);
	}

	static int ina238_read(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long *val)
	{
	switch (type) {
	case hwmon_in:
	return ina238_read_in(dev, attr, channel, val);
	case hwmon_curr:
	return ina238_read_current(dev, attr, val);
	case hwmon_power:
	return ina238_read_power(dev, attr, val);
	case hwmon_temp:
	return ina238_read_temp(dev, attr, val);
	default:
	return -EOPNOTSUPP;
	}
	return 0;
	}

	static int ina238_write(struct device *dev, enum hwmon_sensor_types type,
	u32 attr, int channel, long val)
	{
	struct ina238_data *data = dev_get_drvdata(dev);
	int err;

	mutex_lock(&data->config_lock);

	switch (type) {
	case hwmon_in:
	err = ina238_write_in(dev, attr, channel, val);
	break;
	case hwmon_power:
	err = ina238_write_power(dev, attr, val);
	break;
	case hwmon_temp:
	err = ina238_write_temp(dev, attr, val);
	break;
	default:
	err = -EOPNOTSUPP;
	break;
	}

	mutex_unlock(&data->config_lock);
	return err;
	}

	static umode_t ina238_is_visible(const void *drvdata,
	enum hwmon_sensor_types type,
	u32 attr, int channel)
	{
	switch (type) {
	case hwmon_in:
	switch (attr) {
	case hwmon_in_input:
	case hwmon_in_max_alarm:
	case hwmon_in_min_alarm:
	return 0444;
	case hwmon_in_max:
	case hwmon_in_min:
	return 0644;
	default:
	return 0;
	}
	case hwmon_curr:
	switch (attr) {
	case hwmon_curr_input:
	return 0444;
	default:
	return 0;
	}
	case hwmon_power:
	switch (attr) {
	case hwmon_power_input:
	case hwmon_power_max_alarm:
	return 0444;
	case hwmon_power_max:
	return 0644;
	default:
	return 0;
	}
	case hwmon_temp:
	switch (attr) {
	case hwmon_temp_input:
	case hwmon_temp_max_alarm:
	return 0444;
	case hwmon_temp_max:
	return 0644;
	default:
	return 0;
	}
	default:
	return 0;
	}
	}

	#define INA238_HWMON_IN_CONFIG (HWMON_I_INPUT \| \
	HWMON_I_MAX \| HWMON_I_MAX_ALARM \| \
	HWMON_I_MIN \| HWMON_I_MIN_ALARM)

	static const struct hwmon_channel_info * const ina238_info[] = {
	HWMON_CHANNEL_INFO(in,
	/* 0: shunt voltage */
	INA238_HWMON_IN_CONFIG,
	/* 1: bus voltage */
	INA238_HWMON_IN_CONFIG),
	HWMON_CHANNEL_INFO(curr,
	/* 0: current through shunt */
	HWMON_C_INPUT),
	HWMON_CHANNEL_INFO(power,
	/* 0: power */
	HWMON_P_INPUT \| HWMON_P_MAX \| HWMON_P_MAX_ALARM),
	HWMON_CHANNEL_INFO(temp,
	/* 0: die temperature */
	HWMON_T_INPUT \| HWMON_T_MAX \| HWMON_T_MAX_ALARM),
	NULL
	};

	static const struct hwmon_ops ina238_hwmon_ops = {
	.is_visible = ina238_is_visible,
	.read = ina238_read,
	.write = ina238_write,
	};

	static const struct hwmon_chip_info ina238_chip_info = {
	.ops = &ina238_hwmon_ops,
	.info = ina238_info,
	};

	static int ina238_probe(struct i2c_client *client)
	{
	struct ina2xx_platform_data *pdata = dev_get_platdata(&client->dev);
	struct device *dev = &client->dev;
	struct device *hwmon_dev;
	struct ina238_data *data;
	int config;
	int ret;

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

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

	data->regmap = devm_regmap_init_i2c(client, &ina238_regmap_config);
	if (IS_ERR(data->regmap)) {
	dev_err(dev, "failed to allocate register map\n");
	return PTR_ERR(data->regmap);
	}

	/* load shunt value */
	data->rshunt = INA238_RSHUNT_DEFAULT;
	if (device_property_read_u32(dev, "shunt-resistor", &data->rshunt) < 0 && pdata)
	data->rshunt = pdata->shunt_uohms;
	if (data->rshunt == 0) {
	dev_err(dev, "invalid shunt resister value %u\n", data->rshunt);
	return -EINVAL;
	}

	/* load shunt gain value */
	if (device_property_read_u32(dev, "ti,shunt-gain", &data->gain) < 0)
	data->gain = 4; /* Default of ADCRANGE = 0 */
	if (data->gain != 1 && data->gain != 4) {
	dev_err(dev, "invalid shunt gain value %u\n", data->gain);
	return -EINVAL;
	}

	/* Setup CONFIG register */
	config = INA238_CONFIG_DEFAULT;
	if (data->gain == 1)
	config \|= INA238_CONFIG_ADCRANGE; /* ADCRANGE = 1 is /1 */
	ret = regmap_write(data->regmap, INA238_CONFIG, config);
	if (ret < 0) {
	dev_err(dev, "error configuring the device: %d\n", ret);
	return -ENODEV;
	}

	/* Setup ADC_CONFIG register */
	ret = regmap_write(data->regmap, INA238_ADC_CONFIG,
	INA238_ADC_CONFIG_DEFAULT);
	if (ret < 0) {
	dev_err(dev, "error configuring the device: %d\n", ret);
	return -ENODEV;
	}

	/* Setup SHUNT_CALIBRATION register with fixed value */
	ret = regmap_write(data->regmap, INA238_SHUNT_CALIBRATION,
	INA238_CALIBRATION_VALUE);
	if (ret < 0) {
	dev_err(dev, "error configuring the device: %d\n", ret);
	return -ENODEV;
	}

	/* Setup alert/alarm configuration */
	ret = regmap_write(data->regmap, INA238_DIAG_ALERT,
	INA238_DIAG_ALERT_DEFAULT);
	if (ret < 0) {
	dev_err(dev, "error configuring the device: %d\n", ret);
	return -ENODEV;
	}

	hwmon_dev = devm_hwmon_device_register_with_info(dev, client->name, data,
	&ina238_chip_info,
	NULL);
	if (IS_ERR(hwmon_dev))
	return PTR_ERR(hwmon_dev);

	dev_info(dev, "power monitor %s (Rshunt = %u uOhm, gain = %u)\n",
	client->name, data->rshunt, data->gain);

	return 0;
	}

	static const struct i2c_device_id ina238_id[] = {
	{ "ina238" },
	{ }
	};
	MODULE_DEVICE_TABLE(i2c, ina238_id);

	static const struct of_device_id __maybe_unused ina238_of_match[] = {
	{ .compatible = "ti,ina237" },
	{ .compatible = "ti,ina238" },
	{ },
	};
	MODULE_DEVICE_TABLE(of, ina238_of_match);

	static struct i2c_driver ina238_driver = {
	.driver = {
	.name = "ina238",
	.of_match_table = of_match_ptr(ina238_of_match),
	},
	.probe = ina238_probe,
	.id_table = ina238_id,
	};

	module_i2c_driver(ina238_driver);

	MODULE_AUTHOR("Nathan Rossi <nathan.rossi@digi.com>");
	MODULE_DESCRIPTION("ina238 driver");
	MODULE_LICENSE("GPL");