Re: [PATCH v2 3/3] hwmon: Driver for Texas Instruments INA238

Guenter Roeck
2021-10-27T15:57:03Z

On 10/27/21 12:42 AM, Nathan Rossi wrote:
> From: Nathan Rossi <nathan.rossi@digi.com>
>
> 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@digi.com>
> ---
> 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
> ---
> Documentation/hwmon/ina238.rst | 56 ++++
> Documentation/hwmon/index.rst | 1 +
> drivers/hwmon/Kconfig | 12 +
> drivers/hwmon/Makefile | 1 +
> drivers/hwmon/ina238.c | 672 +++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 742 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@digi.com>
> +
> +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 7fde4c6e1e..21aff4cef7 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..f9d031bdfe
> --- /dev/null
> +++ b/drivers/hwmon/ina238.c
> @@ -0,0 +1,672 @@
> +// 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-sysfs.h>

Unnecessary.

> +#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;
> + u32 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 != 3)
> + return err;

i2c_smbus_read_i2c_block_data() can return 1 or 2, which should be reported as error.
You need something like

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 */
> + if (channel == 0)
> + /* gain of 1 -> LSB / 4 */
> + *val = div_s64((s16)regval * INA238_SHUNT_VOLTAGE_LSB,
> + 1000 * (4 - data->gain + 1));
> + else
> + *val = div_s64((s16)regval * INA238_BUS_VOLTAGE_LSB,
> + 1000);

Pleae check the use of 64-bit divide operations. The above operations
never overflow a long, not even a 32-bit long, and div_s64() is therefore
unencessary. I am quite sure the same applies to current read operations,
though I didn't check.

> + break;
> + case hwmon_in_max_alarm:
> + case hwmon_in_min_alarm:
> + *val = regval & mask ? 1 : 0;

*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 */
> + regval = div_s64((s64)val * 1000LL * (4 - data->gain + 1),
> + INA238_SHUNT_VOLTAGE_LSB);

I am quite sure the typecast is unnecessary here. Also, if you'd use clamp_val()
prior to the multiply/divide operation, I am quite sure you would not need
to use 64-bit divide operations.

> + if (regval > S16_MAX || regval < S16_MIN)
> + return -EINVAL;

We usually handle limit writes out of range with clamp_val() and
do not expect users to find the valid range for a given chip.

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:
> + regval = div_u64((u64)val * 1000ULL, INA238_BUS_VOLTAGE_LSB);

This converts -1 to a really large value, which then overflows before being divided.
The result is more or less random. I think you'll need to use clamp_val first here.

> + if (regval > U16_MAX || regval < 0)
> + return -EINVAL;

regval = clamp_val(regval, 0, U16_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, int channel,
> + long *val)
> +{
> + struct ina238_data *data = dev_get_drvdata(dev);
> + int regval;
> + int err;
> +
> + if (channel != 0)
> + return -EOPNOTSUPP;
> +
> + 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, int channel,
> + long *val)
> +{
> + struct ina238_data *data = dev_get_drvdata(dev);
> + long long power;
> + int regval;
> + int err;
> +
> + if (channel != 0)
> + return -EOPNOTSUPP;
> +
> + 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 ? 1 : 0;

*val = !!(regval & INA238_DIAG_ALERT_POL);

> + break;
> + default:
> + return -EOPNOTSUPP;
> + }
> +
> + return 0;
> +}
> +
> +static int ina238_write_power(struct device *dev, u32 attr, int channel,
> + long val)
> +{
> + struct ina238_data *data = dev_get_drvdata(dev);
> + int regval;
> +
> + if (channel != 0 || attr != hwmon_power_max)
> + return -EOPNOTSUPP;
> +
> + /*
> + * Compared against the 24-bit power register, lower 8-bits are
> + * truncated. Same conversion to/from uW as POWER register.
> + */
> + regval = div_u64((u64)val * 20ULL * data->rshunt,
> + 1000ULL * INA238_FIXED_SHUNT * (u64)data->gain);

Same problem as above - negative values of val will have in unpredictable results.
The last typecat should be unnecessary.

> + regval = regval >> 8;
> + if (regval > U16_MAX || regval < 0)
> + return -EINVAL;

regval = clamp_val(...);

> +
> + return regmap_write(data->regmap, INA238_POWER_LIMIT, regval);
> +}
> +
> +static int ina238_read_temp(struct device *dev, u32 attr, int channel,
> + long *val)
> +{
> + struct ina238_data *data = dev_get_drvdata(dev);
> + int regval;
> + int err;
> +
> + if (channel != 0)
> + return -EOPNOTSUPP;
> +
> + 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 ? 1 : 0;

*val = !!(regval & INA238_DIAG_ALERT_TMPOL);

> + break;
> + default:
> + return -EOPNOTSUPP;
> + }
> +
> + return 0;
> +}
> +
> +static int ina238_write_temp(struct device *dev, u32 attr, int channel,
> + long val)
> +{
> + struct ina238_data *data = dev_get_drvdata(dev);
> + int regval;
> +
> + if (channel != 0 || attr != hwmon_temp_max)
> + return -EOPNOTSUPP;
> +
> + /* Signed, bits 15-4 of register */
> + regval = (div_s64(val, INA238_DIE_TEMP_LSB) << 4);
> + if (regval > S16_MAX || regval < S16_MIN)
> + return -EINVAL;

regval = clamp_val(regval, S16_MIN, S16_MAX) & 0xfff0;

> + regval = regval & 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, channel, val);
> + case hwmon_power:
> + return ina238_read_power(dev, attr, channel, val);
> + case hwmon_temp:
> + return ina238_read_temp(dev, attr, channel, 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, channel, val);
> + break;
> + case hwmon_temp:
> + err = ina238_write_temp(dev, attr, channel, 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:
> + if (channel != 0 && channel != 1)
> + return 0;

FWIW, channel checks are not really needed.

> +
> + 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:
> + if (channel != 0)
> + return 0;
> +
> + switch (attr) {
> + case hwmon_curr_input:
> + return 0444;
> + default:
> + return 0;
> + }
> + case hwmon_power:
> + if (channel != 0)
> + return 0;
> +
> + 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:
> + if (channel != 0)
> + return 0;
> +
> + 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;
> + /* set the device type */

Pointless comment. I don't even understand what it is supposed to mean.

> + 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)

Drop the continuation line. Lines longer than 80 columns are fine when
improving readability, and that is definitely the case here.

> + 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;
> + }

I think ti,shunt-gain needs a better explanation in the .yaml file, for
people writing devicetree files to understand how the gain value converts
to a register value.

> +
> + /* 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@digi.com>");
> +MODULE_DESCRIPTION("ina238 driver");
> +MODULE_LICENSE("GPL");
> ---
> 2.33.0
>