// SPDX-License-Identifier: GPL-2.0
/*
 * iio/adc/max9611.c
 *
 * Maxim max9611/max9612 high side current sense amplifier with
 * 12-bit ADC interface.
 *
 * Copyright (C) 2017 Jacopo Mondi
 */

/*
 * 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/mod_devicetable.h>
#include <linux/property.h>

/* 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(15, 7)
#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

/*
 * Conversion time is 2 ms (typically) at Ta=25 degreeC
 * No maximum value is known, so play it safe.
 */
#define MAX9611_CONV_TIME_US_RANGE      3000, 3300

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 = CONF_SENSE_1x,
        CSA_GAIN_4x = CONF_SENSE_4x,
        CSA_GAIN_8x = CONF_SENSE_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] = {
        [CSA_GAIN_1x] = { MAX9611_CSA_1X_LSB_nV, MAX9611_CSA_1X_OFFS_RAW, },
        [CSA_GAIN_4x] = { MAX9611_CSA_4X_LSB_nV, MAX9611_CSA_4X_OFFS_RAW, },
        [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. */

        usleep_range(MAX9611_CONV_TIME_US_RANGE);

        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 = (enum max9611_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 sysfs_emit(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 = {
        .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 &= 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(MAX9611_CONV_TIME_US_RANGE);

        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 char * const shunt_res_prop = "shunt-resistor-micro-ohms";
        struct max9611_dev *max9611;
        struct iio_dev *indio_dev;
        struct device *dev = &client->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            = dev;
        max9611->i2c_client     = client;
        mutex_init(&max9611->lock);

        ret = device_property_read_u32(dev, shunt_res_prop, &of_shunt);
        if (ret) {
                dev_err(dev, "Missing %s property for %pfw node\n",
                        shunt_res_prop, dev_fwnode(dev));
                return ret;
        }
        max9611->shunt_resistor_uohm = of_shunt;

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

        indio_dev->name         = device_get_match_data(dev);
        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(dev, indio_dev);
}

static struct i2c_driver max9611_driver = {
        .driver = {
                   .name = "max9611",
                   .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");