[PATCH v4 3/3] hwmon: Driver for Texas Instruments INA238

[Nathan Rossi]

From: Nathan Rossi <nathan.rossi@xxxxxxxx>

The INA238 is a I2C power monitor similar to other INA2xx devices,
providing shunt voltage, bus voltage, current, power and temperature
measurements.

Signed-off-by: Nathan Rossi <nathan.rossi@xxxxxxxx>
---
Changes in v2:
- Add ina238 documentation to hwmon/index
- Remove unused header includes and sort
- Set regmap_config max_register in struct initialization
- Remove shunt-resistor attribute and associated functions
- Rename crit/lcrit attributes to max/min
- Rework to use the hwmon_chip_info API
- Add max_alarm and min_alarm channels and associated alert/alarm config
- Add device tree ti,shunt-gain property use and ADCRANGE setup

Changes in v3:
- Remove unnecessary header include
- Change ina238_read_reg24 to return EIO when invalid byte count is read
  from device
- Replace '? 1 : 0' with '!!'
- Clamp the input value of attributes before calculating the associated
  register value, this avoids issues with negative values and avoids
  some of the need to perform 64-bit calculations
- Check the use of 64-bit divides and replace where possible
  - The current and power calculations still use 64-bit calculations due
    to maintaining precision while correcting for difference between
    calibrated and actual shunt values (micro ohm value multiplication
    causes overflow of long)
- Remove channel index checks and passing channel value to read/write
  functions

Changes in v4:
- Change ina238_data.gain from u32 to int to avoid type casts and issues
  with mixed signed/unsigned operations
---
 Documentation/hwmon/ina238.rst |  56 ++++
 Documentation/hwmon/index.rst  |   1 +
 drivers/hwmon/Kconfig          |  12 +
 drivers/hwmon/Makefile         |   1 +
 drivers/hwmon/ina238.c         | 644 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 714 insertions(+)
 create mode 100644 Documentation/hwmon/ina238.rst
 create mode 100644 drivers/hwmon/ina238.c

diff --git a/Documentation/hwmon/ina238.rst b/Documentation/hwmon/ina238.rst
new file mode 100644
index 0000000000..d9f4799844
--- /dev/null
+++ b/Documentation/hwmon/ina238.rst
@@ -0,0 +1,56 @@
+.. SPDX-License-Identifier: GPL-2.0-only
+
+Kernel driver ina238
+====================
+
+Supported chips:
+
+  * Texas Instruments INA238
+
+    Prefix: 'ina238'
+
+    Addresses: I2C 0x40 - 0x4f
+
+    Datasheet:
+	https://www.ti.com/lit/gpn/ina238
+
+Author: Nathan Rossi <nathan.rossi@xxxxxxxx>
+
+Description
+-----------
+
+The INA238 is a current shunt, power and temperature monitor with an I2C
+interface. It includes a number of programmable functions including alerts,
+conversion rate, sample averaging and selectable shunt voltage accuracy.
+
+The shunt value in micro-ohms can be set via platform data or device tree at
+compile-time or via the shunt_resistor attribute in sysfs at run-time. Please
+refer to the Documentation/devicetree/bindings/hwmon/ti,ina2xx.yaml for bindings
+if the device tree is used.
+
+Sysfs entries
+-------------
+
+======================= =======================================================
+in0_input		Shunt voltage (mV)
+in0_min			Minimum shunt voltage threshold (mV)
+in0_min_alarm		Minimum shunt voltage alarm
+in0_max			Maximum shunt voltage threshold (mV)
+in0_max_alarm		Maximum shunt voltage alarm
+
+in1_input		Bus voltage (mV)
+in1_min			Minimum bus voltage threshold (mV)
+in1_min_alarm		Minimum shunt voltage alarm
+in1_max			Maximum bus voltage threshold (mV)
+in1_max_alarm		Maximum shunt voltage alarm
+
+power1_input		Power measurement (uW)
+power1_max		Maximum power threshold (uW)
+power1_max_alarm	Maximum power alarm
+
+curr1_input		Current measurement (mA)
+
+temp1_input		Die temperature measurement (mC)
+temp1_max		Maximum die temperature threshold (mC)
+temp1_max_alarm		Maximum die temperature alarm
+======================= =======================================================
diff --git a/Documentation/hwmon/index.rst b/Documentation/hwmon/index.rst
index 7046bf1870..6f30c8c9c7 100644
--- a/Documentation/hwmon/index.rst
+++ b/Documentation/hwmon/index.rst
@@ -76,6 +76,7 @@ Hardware Monitoring Kernel Drivers
    ibmpowernv
    ina209
    ina2xx
+   ina238
    ina3221
    intel-m10-bmc-hwmon
    ir35221
diff --git a/drivers/hwmon/Kconfig b/drivers/hwmon/Kconfig
index 64bd3dfba2..8815e96911 100644
--- a/drivers/hwmon/Kconfig
+++ b/drivers/hwmon/Kconfig
@@ -1872,6 +1872,18 @@ config SENSORS_INA2XX
 	  This driver can also be built as a module. If so, the module
 	  will be called ina2xx.
 
+config SENSORS_INA238
+	tristate "Texas Instruments INA238"
+	depends on I2C
+	select REGMAP_I2C
+	help
+	  If you say yes here you get support for the INA238 power monitor
+	  chip. This driver supports voltage, current, power and temperature
+	  measurements as well as alarm configuration.
+
+	  This driver can also be built as a module. If so, the module
+	  will be called ina238.
+
 config SENSORS_INA3221
 	tristate "Texas Instruments INA3221 Triple Power Monitor"
 	depends on I2C
diff --git a/drivers/hwmon/Makefile b/drivers/hwmon/Makefile
index baee6a8d4d..1ddb26f57a 100644
--- a/drivers/hwmon/Makefile
+++ b/drivers/hwmon/Makefile
@@ -90,6 +90,7 @@ obj-$(CONFIG_SENSORS_IBMPOWERNV)+= ibmpowernv.o
 obj-$(CONFIG_SENSORS_IIO_HWMON) += iio_hwmon.o
 obj-$(CONFIG_SENSORS_INA209)	+= ina209.o
 obj-$(CONFIG_SENSORS_INA2XX)	+= ina2xx.o
+obj-$(CONFIG_SENSORS_INA238)	+= ina238.o
 obj-$(CONFIG_SENSORS_INA3221)	+= ina3221.o
 obj-$(CONFIG_SENSORS_INTEL_M10_BMC_HWMON) += intel-m10-bmc-hwmon.o
 obj-$(CONFIG_SENSORS_IT87)	+= it87.o
diff --git a/drivers/hwmon/ina238.c b/drivers/hwmon/ina238.c
new file mode 100644
index 0000000000..50eb9c5e13
--- /dev/null
+++ b/drivers/hwmon/ina238.c
@@ -0,0 +1,644 @@
+// 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@xxxxxxxx>
+ */
+
+#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
+
+#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 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 *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", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(i2c, ina238_id);
+
+static const struct of_device_id __maybe_unused ina238_of_match[] = {
+	{ .compatible = "ti,ina238" },
+	{ },
+};
+MODULE_DEVICE_TABLE(of, ina238_of_match);
+
+static struct i2c_driver ina238_driver = {
+	.class		= I2C_CLASS_HWMON,
+	.driver = {
+		.name	= "ina238",
+		.of_match_table = of_match_ptr(ina238_of_match),
+	},
+	.probe_new	= ina238_probe,
+	.id_table	= ina238_id,
+};
+
+module_i2c_driver(ina238_driver);
+
+MODULE_AUTHOR("Nathan Rossi <nathan.rossi@xxxxxxxx>");
+MODULE_DESCRIPTION("ina238 driver");
+MODULE_LICENSE("GPL");
---
2.33.0