drivers/iio/adc/max9611.c

/*
 * iio/adc/max9611.c
 *
 * Maxim max9611/max9612 high side current sense amplifier with
 * 12-bit ADC interface.
 *
 * Copyright (C) 2017 Jacopo Mondi
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

/*
 * This driver supports input common-mode voltage, current-sense
 * amplifier with programmable gains and die temperature reading from
 * Maxim max9611/max9612.
 *
 * Op-amp, analog comparator, and watchdog functionalities are not
 * supported by this driver.
 */

#include <linux/delay.h>
#include <linux/i2c.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/module.h>
#include <linux/of_device.h>

#define DRIVER_NAME			"max9611"

/* max9611 register addresses */
#define MAX9611_REG_CSA_DATA		0x00
#define MAX9611_REG_RS_DATA		0x02
#define MAX9611_REG_TEMP_DATA		0x08
#define MAX9611_REG_CTRL1		0x0a
#define MAX9611_REG_CTRL2		0x0b

/* max9611 REG1 mux configuration options */
#define MAX9611_MUX_MASK		GENMASK(3, 0)
#define MAX9611_MUX_SENSE_1x		0x00
#define MAX9611_MUX_SENSE_4x		0x01
#define MAX9611_MUX_SENSE_8x		0x02
#define MAX9611_INPUT_VOLT		0x03
#define MAX9611_MUX_TEMP		0x06

/* max9611 voltage (both csa and input) helper macros */
#define MAX9611_VOLTAGE_SHIFT		0x04
#define MAX9611_VOLTAGE_RAW(_r)		((_r) >> MAX9611_VOLTAGE_SHIFT)

/*
 * max9611 current sense amplifier voltage output:
 * LSB and offset values depends on selected gain (1x, 4x, 8x)
 *
 * GAIN		LSB (nV)	OFFSET (LSB steps)
 * 1x		107500		1
 * 4x		26880		1
 * 8x		13440		3
 *
 * The complete formula to calculate current sense voltage is:
 *     (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
 */
#define MAX9611_CSA_1X_LSB_nV		107500
#define MAX9611_CSA_4X_LSB_nV		26880
#define MAX9611_CSA_8X_LSB_nV		13440

#define MAX9611_CSA_1X_OFFS_RAW		1
#define MAX9611_CSA_4X_OFFS_RAW		1
#define MAX9611_CSA_8X_OFFS_RAW		3

/*
 * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
 *
 * The complete formula to calculate input common voltage is:
 *     (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
 */
#define MAX9611_CIM_LSB_mV		14
#define MAX9611_CIM_OFFSET_RAW		1

/*
 * max9611 temperature reading: LSB is 480 milli degrees Celsius
 *
 * The complete formula to calculate temperature is:
 *     ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
 */
#define MAX9611_TEMP_MAX_POS		0x7f80
#define MAX9611_TEMP_MAX_NEG		0xff80
#define MAX9611_TEMP_MIN_NEG		0xd980
#define MAX9611_TEMP_MASK		GENMASK(7, 15)
#define MAX9611_TEMP_SHIFT		0x07
#define MAX9611_TEMP_RAW(_r)		((_r) >> MAX9611_TEMP_SHIFT)
#define MAX9611_TEMP_SCALE_NUM		1000000
#define MAX9611_TEMP_SCALE_DIV		2083

struct max9611_dev {
	struct device *dev;
	struct i2c_client *i2c_client;
	struct mutex lock;
	unsigned int shunt_resistor_uohm;
};

enum max9611_conf_ids {
	CONF_SENSE_1x,
	CONF_SENSE_4x,
	CONF_SENSE_8x,
	CONF_IN_VOLT,
	CONF_TEMP,
};

/**
 * max9611_mux_conf - associate ADC mux configuration with register address
 *		      where data shall be read from
 */
static const unsigned int max9611_mux_conf[][2] = {
	/* CONF_SENSE_1x */
	{ MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
	/* CONF_SENSE_4x */
	{ MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
	/* CONF_SENSE_8x */
	{ MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
	/* CONF_IN_VOLT */
	{ MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
	/* CONF_TEMP */
	{ MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
};

enum max9611_csa_gain {
	CSA_GAIN_1x,
	CSA_GAIN_4x,
	CSA_GAIN_8x,
};

enum max9611_csa_gain_params {
	CSA_GAIN_LSB_nV,
	CSA_GAIN_OFFS_RAW,
};

/**
 * max9611_csa_gain_conf - associate gain multiplier with LSB and
 *			   offset values.
 *
 * Group together parameters associated with configurable gain
 * on current sense amplifier path to ADC interface.
 * Current sense read routine adjusts gain until it gets a meaningful
 * value; use this structure to retrieve the correct LSB and offset values.
 */
static const unsigned int max9611_gain_conf[][2] = {
	{ /* [0] CSA_GAIN_1x */
		MAX9611_CSA_1X_LSB_nV,
		MAX9611_CSA_1X_OFFS_RAW,
	},
	{ /* [1] CSA_GAIN_4x */
		MAX9611_CSA_4X_LSB_nV,
		MAX9611_CSA_4X_OFFS_RAW,
	},
	{ /* [2] CSA_GAIN_8x */
		MAX9611_CSA_8X_LSB_nV,
		MAX9611_CSA_8X_OFFS_RAW,
	},
};

enum max9611_chan_addrs {
	MAX9611_CHAN_VOLTAGE_INPUT,
	MAX9611_CHAN_VOLTAGE_SENSE,
	MAX9611_CHAN_TEMPERATURE,
	MAX9611_CHAN_CURRENT_LOAD,
	MAX9611_CHAN_POWER_LOAD,
};

static const struct iio_chan_spec max9611_channels[] = {
	{
	  .type			= IIO_TEMP,
	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW) |
				  BIT(IIO_CHAN_INFO_SCALE),
	  .address		= MAX9611_CHAN_TEMPERATURE,
	},
	{
	  .type			= IIO_VOLTAGE,
	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
	  .address		= MAX9611_CHAN_VOLTAGE_SENSE,
	  .indexed		= 1,
	  .channel		= 0,
	},
	{
	  .type			= IIO_VOLTAGE,
	  .info_mask_separate	= BIT(IIO_CHAN_INFO_RAW)   |
				  BIT(IIO_CHAN_INFO_SCALE) |
				  BIT(IIO_CHAN_INFO_OFFSET),
	  .address		= MAX9611_CHAN_VOLTAGE_INPUT,
	  .indexed		= 1,
	  .channel		= 1,
	},
	{
	  .type			= IIO_CURRENT,
	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
	  .address		= MAX9611_CHAN_CURRENT_LOAD,
	},
	{
	  .type			= IIO_POWER,
	  .info_mask_separate	= BIT(IIO_CHAN_INFO_PROCESSED),
	  .address		= MAX9611_CHAN_POWER_LOAD
	},
};

/**
 * max9611_read_single() - read a single value from ADC interface
 *
 * Data registers are 16 bit long, spread between two 8 bit registers
 * with consecutive addresses.
 * Configure ADC mux first, then read register at address "reg_addr".
 * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
 * to return values from "reg_addr" and "reg_addr + 1" consecutively.
 * Data are transmitted with big-endian ordering: MSB arrives first.
 *
 * @max9611: max9611 device
 * @selector: index for mux and register configuration
 * @raw_val: the value returned from ADC
 */
static int max9611_read_single(struct max9611_dev *max9611,
			       enum max9611_conf_ids selector,
			       u16 *raw_val)
{
	int ret;

	u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
	u8 reg_addr = max9611_mux_conf[selector][1];

	/*
	 * Keep mutex lock held during read-write to avoid mux register
	 * (CTRL1) re-configuration.
	 */
	mutex_lock(&max9611->lock);
	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
					MAX9611_REG_CTRL1, mux_conf);
	if (ret) {
		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
			MAX9611_REG_CTRL1, mux_conf);
		mutex_unlock(&max9611->lock);
		return ret;
	}

	/*
	 * need a delay here to make register configuration
	 * stabilize. 1 msec at least, from empirical testing.
	 */
	usleep_range(1000, 2000);

	ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
	if (ret < 0) {
		dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
			reg_addr);
		mutex_unlock(&max9611->lock);
		return ret;
	}

	*raw_val = ret;
	mutex_unlock(&max9611->lock);

	return 0;
}

/**
 * max9611_read_csa_voltage() - read current sense amplifier output voltage
 *
 * Current sense amplifier output voltage is read through a configurable
 * 1x, 4x or 8x gain.
 * Start with plain 1x gain, and adjust gain control properly until a
 * meaningful value is read from ADC output.
 *
 * @max9611: max9611 device
 * @adc_raw: raw value read from ADC output
 * @csa_gain: gain configuration option selector
 */
static int max9611_read_csa_voltage(struct max9611_dev *max9611,
				    u16 *adc_raw,
				    enum max9611_csa_gain *csa_gain)
{
	enum max9611_conf_ids gain_selectors[] = {
		CONF_SENSE_1x,
		CONF_SENSE_4x,
		CONF_SENSE_8x
	};
	unsigned int i;
	int ret;

	for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
		ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
		if (ret)
			return ret;

		if (*adc_raw > 0) {
			*csa_gain = gain_selectors[i];
			return 0;
		}
	}

	return -EIO;
}

static int max9611_read_raw(struct iio_dev *indio_dev,
			    struct iio_chan_spec const *chan,
			    int *val, int *val2, long mask)
{
	struct max9611_dev *dev = iio_priv(indio_dev);
	enum max9611_csa_gain gain_selector;
	const unsigned int *csa_gain;
	u16 adc_data;
	int ret;

	switch (mask) {
	case IIO_CHAN_INFO_RAW:

		switch (chan->address) {
		case MAX9611_CHAN_TEMPERATURE:
			ret = max9611_read_single(dev, CONF_TEMP,
						  &adc_data);
			if (ret)
				return -EINVAL;

			*val = MAX9611_TEMP_RAW(adc_data);
			return IIO_VAL_INT;

		case MAX9611_CHAN_VOLTAGE_INPUT:
			ret = max9611_read_single(dev, CONF_IN_VOLT,
						  &adc_data);
			if (ret)
				return -EINVAL;

			*val = MAX9611_VOLTAGE_RAW(adc_data);
			return IIO_VAL_INT;
		}

		break;

	case IIO_CHAN_INFO_OFFSET:
		/* MAX9611_CHAN_VOLTAGE_INPUT */
		*val = MAX9611_CIM_OFFSET_RAW;

		return IIO_VAL_INT;

	case IIO_CHAN_INFO_SCALE:

		switch (chan->address) {
		case MAX9611_CHAN_TEMPERATURE:
			*val = MAX9611_TEMP_SCALE_NUM;
			*val2 = MAX9611_TEMP_SCALE_DIV;

			return IIO_VAL_FRACTIONAL;

		case MAX9611_CHAN_VOLTAGE_INPUT:
			*val = MAX9611_CIM_LSB_mV;

			return IIO_VAL_INT;
		}

		break;

	case IIO_CHAN_INFO_PROCESSED:

		switch (chan->address) {
		case MAX9611_CHAN_VOLTAGE_SENSE:
			/*
			 * processed (mV): (raw - offset) * LSB (nV) / 10^6
			 *
			 * Even if max9611 can output raw csa voltage readings,
			 * use a produced value as scale depends on gain.
			 */
			ret = max9611_read_csa_voltage(dev, &adc_data,
						       &gain_selector);
			if (ret)
				return -EINVAL;

			csa_gain = max9611_gain_conf[gain_selector];

			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
			*val = MAX9611_VOLTAGE_RAW(adc_data) *
			       csa_gain[CSA_GAIN_LSB_nV];
			*val2 = 1000000;

			return IIO_VAL_FRACTIONAL;

		case MAX9611_CHAN_CURRENT_LOAD:
			/* processed (mA): Vcsa (nV) / Rshunt (uOhm)  */
			ret = max9611_read_csa_voltage(dev, &adc_data,
						       &gain_selector);
			if (ret)
				return -EINVAL;

			csa_gain = max9611_gain_conf[gain_selector];

			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
			*val = MAX9611_VOLTAGE_RAW(adc_data) *
			       csa_gain[CSA_GAIN_LSB_nV];
			*val2 = dev->shunt_resistor_uohm;

			return IIO_VAL_FRACTIONAL;

		case MAX9611_CHAN_POWER_LOAD:
			/*
			 * processed (mW): Vin (mV) * Vcsa (uV) /
			 *		   Rshunt (uOhm)
			 */
			ret = max9611_read_single(dev, CONF_IN_VOLT,
						  &adc_data);
			if (ret)
				return -EINVAL;

			adc_data -= MAX9611_CIM_OFFSET_RAW;
			*val = MAX9611_VOLTAGE_RAW(adc_data) *
			       MAX9611_CIM_LSB_mV;

			ret = max9611_read_csa_voltage(dev, &adc_data,
						       &gain_selector);
			if (ret)
				return -EINVAL;

			csa_gain = max9611_gain_conf[gain_selector];

			/* divide by 10^3 here to avoid 32bit overflow */
			adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
			*val *= MAX9611_VOLTAGE_RAW(adc_data) *
				csa_gain[CSA_GAIN_LSB_nV] / 1000;
			*val2 = dev->shunt_resistor_uohm;

			return IIO_VAL_FRACTIONAL;
		}

		break;
	}

	return -EINVAL;
}

static ssize_t max9611_shunt_resistor_show(struct device *dev,
					   struct device_attribute *attr,
					   char *buf)
{
	struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
	unsigned int i, r;

	i = max9611->shunt_resistor_uohm / 1000000;
	r = max9611->shunt_resistor_uohm % 1000000;

	return sprintf(buf, "%u.%06u\n", i, r);
}

static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
		       max9611_shunt_resistor_show, NULL, 0);
static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
		       max9611_shunt_resistor_show, NULL, 0);

static struct attribute *max9611_attributes[] = {
	&iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
	&iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
	NULL,
};

static const struct attribute_group max9611_attribute_group = {
	.attrs = max9611_attributes,
};

static const struct iio_info indio_info = {
	.driver_module	= THIS_MODULE,
	.read_raw	= max9611_read_raw,
	.attrs		= &max9611_attribute_group,
};

static int max9611_init(struct max9611_dev *max9611)
{
	struct i2c_client *client = max9611->i2c_client;
	u16 regval;
	int ret;

	if (!i2c_check_functionality(client->adapter,
				     I2C_FUNC_SMBUS_WRITE_BYTE	|
				     I2C_FUNC_SMBUS_READ_WORD_DATA)) {
		dev_err(max9611->dev,
			"I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
		return -EINVAL;
	}

	/* Make sure die temperature is in range to test communications. */
	ret = max9611_read_single(max9611, CONF_TEMP, &regval);
	if (ret)
		return ret;

	regval = ret & MAX9611_TEMP_MASK;

	if ((regval > MAX9611_TEMP_MAX_POS &&
	     regval < MAX9611_TEMP_MIN_NEG) ||
	     regval > MAX9611_TEMP_MAX_NEG) {
		dev_err(max9611->dev,
			"Invalid value received from ADC 0x%4x: aborting\n",
			regval);
		return -EIO;
	}

	/* Mux shall be zeroed back before applying other configurations */
	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
					MAX9611_REG_CTRL1, 0);
	if (ret) {
		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
			MAX9611_REG_CTRL1, 0);
		return ret;
	}

	ret = i2c_smbus_write_byte_data(max9611->i2c_client,
					MAX9611_REG_CTRL2, 0);
	if (ret) {
		dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
			MAX9611_REG_CTRL2, 0);
		return ret;
	}
	usleep_range(1000, 2000);

	return 0;
}

static const struct of_device_id max9611_of_table[] = {
	{.compatible = "maxim,max9611", .data = "max9611"},
	{.compatible = "maxim,max9612", .data = "max9612"},
	{ },
};

MODULE_DEVICE_TABLE(of, max9611_of_table);
static int max9611_probe(struct i2c_client *client,
			 const struct i2c_device_id *id)
{
	const char * const shunt_res_prop = "shunt-resistor-micro-ohms";
	const struct device_node *of_node = client->dev.of_node;
	const struct of_device_id *of_id =
		of_match_device(max9611_of_table, &client->dev);
	struct max9611_dev *max9611;
	struct iio_dev *indio_dev;
	unsigned int of_shunt;
	int ret;

	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
	if (!indio_dev)
		return -ENOMEM;

	i2c_set_clientdata(client, indio_dev);

	max9611			= iio_priv(indio_dev);
	max9611->dev		= &client->dev;
	max9611->i2c_client	= client;
	mutex_init(&max9611->lock);

	ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
	if (ret) {
		dev_err(&client->dev,
			"Missing %s property for %s node\n",
			shunt_res_prop, of_node->full_name);
		return ret;
	}
	max9611->shunt_resistor_uohm = of_shunt;

	ret = max9611_init(max9611);
	if (ret)
		return ret;

	indio_dev->dev.parent	= &client->dev;
	indio_dev->dev.of_node	= client->dev.of_node;
	indio_dev->name		= of_id->data;
	indio_dev->modes	= INDIO_DIRECT_MODE;
	indio_dev->info		= &indio_info;
	indio_dev->channels	= max9611_channels;
	indio_dev->num_channels	= ARRAY_SIZE(max9611_channels);

	return devm_iio_device_register(&client->dev, indio_dev);
}

static struct i2c_driver max9611_driver = {
	.driver = {
		   .name = DRIVER_NAME,
		   .owner = THIS_MODULE,
		   .of_match_table = max9611_of_table,
	},
	.probe = max9611_probe,
};
module_i2c_driver(max9611_driver);

MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
MODULE_LICENSE("GPL v2");