ina238.c

// 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

#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 * 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", 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		= 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");