// SPDX-License-Identifier: GPL-2.0
/*
 * max44009.c - Support for MAX44009 Ambient Light Sensor
 *
 * Copyright (c) 2019 Robert Eshleman <bobbyeshleman@gmail.com>
 *
 * Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX44009.pdf
 *
 * TODO: Support continuous mode and configuring from manual mode to
 *       automatic mode.
 *
 * Default I2C address: 0x4a
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/bits.h>
#include <linux/i2c.h>
#include <linux/iio/events.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/util_macros.h>

#define MAX44009_DRV_NAME "max44009"

/* Registers in datasheet order */
#define MAX44009_REG_INT_STATUS 0x0
#define MAX44009_REG_INT_EN 0x1
#define MAX44009_REG_CFG 0x2
#define MAX44009_REG_LUX_HI 0x3
#define MAX44009_REG_LUX_LO 0x4
#define MAX44009_REG_UPPER_THR 0x5
#define MAX44009_REG_LOWER_THR 0x6
#define MAX44009_REG_THR_TIMER 0x7

#define MAX44009_CFG_TIM_MASK GENMASK(2, 0)
#define MAX44009_CFG_MAN_MODE_MASK BIT(6)

/* The maximum rising threshold for the max44009 */
#define MAX44009_MAXIMUM_THRESHOLD 7520256

#define MAX44009_THRESH_EXP_MASK (0xf << 4)
#define MAX44009_THRESH_EXP_RSHIFT 4
#define MAX44009_THRESH_MANT_LSHIFT 4
#define MAX44009_THRESH_MANT_MASK 0xf

#define MAX44009_UPPER_THR_MINIMUM 15

/* The max44009 always scales raw readings by 0.045 and is non-configurable */
#define MAX44009_SCALE_NUMERATOR 45
#define MAX44009_SCALE_DENOMINATOR 1000

/* The fixed-point fractional multiplier for de-scaling threshold values */
#define MAX44009_FRACT_MULT 1000000

static const u32 max44009_int_time_ns_array[] = {
        800000000,
        400000000,
        200000000,
        100000000,
        50000000, /* Manual mode only */
        25000000, /* Manual mode only */
        12500000, /* Manual mode only */
        6250000,  /* Manual mode only */
};

static const char max44009_int_time_str[] =
        "0.8 "
        "0.4 "
        "0.2 "
        "0.1 "
        "0.05 "
        "0.025 "
        "0.0125 "
        "0.00625";

struct max44009_data {
        struct i2c_client *client;
        struct mutex lock;
};

static const struct iio_event_spec max44009_event_spec[] = {
        {
                .type = IIO_EV_TYPE_THRESH,
                .dir = IIO_EV_DIR_RISING,
                .mask_separate = BIT(IIO_EV_INFO_VALUE) |
                                 BIT(IIO_EV_INFO_ENABLE),
        },
        {
                .type = IIO_EV_TYPE_THRESH,
                .dir = IIO_EV_DIR_FALLING,
                .mask_separate = BIT(IIO_EV_INFO_VALUE) |
                                 BIT(IIO_EV_INFO_ENABLE),
        },
};

static const struct iio_chan_spec max44009_channels[] = {
        {
                .type = IIO_LIGHT,
                .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
                                      BIT(IIO_CHAN_INFO_INT_TIME),
                .event_spec = max44009_event_spec,
                .num_event_specs = ARRAY_SIZE(max44009_event_spec),
        },
};

static int max44009_read_int_time(struct max44009_data *data)
{

        int ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_CFG);

        if (ret < 0)
                return ret;

        return max44009_int_time_ns_array[ret & MAX44009_CFG_TIM_MASK];
}

static int max44009_write_int_time(struct max44009_data *data,
                                   int val, int val2)
{
        struct i2c_client *client = data->client;
        int ret, int_time, config;
        s64 ns;

        ns = val * NSEC_PER_SEC + val2;
        int_time = find_closest_descending(
                        ns,
                        max44009_int_time_ns_array,
                        ARRAY_SIZE(max44009_int_time_ns_array));

        ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
        if (ret < 0)
                return ret;

        config = ret;
        config &= int_time;

        /*
         * To set the integration time, the device must also be in manual
         * mode.
         */
        config |= MAX44009_CFG_MAN_MODE_MASK;

        return i2c_smbus_write_byte_data(client, MAX44009_REG_CFG, config);
}

static int max44009_write_raw(struct iio_dev *indio_dev,
                              struct iio_chan_spec const *chan, int val,
                              int val2, long mask)
{
        struct max44009_data *data = iio_priv(indio_dev);
        int ret;

        if (mask == IIO_CHAN_INFO_INT_TIME && chan->type == IIO_LIGHT) {
                mutex_lock(&data->lock);
                ret = max44009_write_int_time(data, val, val2);
                mutex_unlock(&data->lock);
                return ret;
        }
        return -EINVAL;
}

static int max44009_write_raw_get_fmt(struct iio_dev *indio_dev,
                                      struct iio_chan_spec const *chan,
                                      long mask)
{
        return IIO_VAL_INT_PLUS_NANO;
}

static int max44009_lux_raw(u8 hi, u8 lo)
{
        int mantissa;
        int exponent;

        /*
         * The mantissa consists of the low nibble of the Lux High Byte
         * and the low nibble of the Lux Low Byte.
         */
        mantissa = ((hi & 0xf) << 4) | (lo & 0xf);

        /* The exponent byte is just the upper nibble of the Lux High Byte */
        exponent = (hi >> 4) & 0xf;

        /*
         * The exponent value is base 2 to the power of the raw exponent byte.
         */
        exponent = 1 << exponent;

        return exponent * mantissa;
}

#define MAX44009_READ_LUX_XFER_LEN (4)

static int max44009_read_lux_raw(struct max44009_data *data)
{
        int ret;
        u8 hireg = MAX44009_REG_LUX_HI;
        u8 loreg = MAX44009_REG_LUX_LO;
        u8 lo = 0;
        u8 hi = 0;

        struct i2c_msg msgs[] = {
                {
                        .addr = data->client->addr,
                        .flags = 0,
                        .len = sizeof(hireg),
                        .buf = &hireg,
                },
                {
                        .addr = data->client->addr,
                        .flags = I2C_M_RD,
                        .len = sizeof(hi),
                        .buf = &hi,
                },
                {
                        .addr = data->client->addr,
                        .flags = 0,
                        .len = sizeof(loreg),
                        .buf = &loreg,
                },
                {
                        .addr = data->client->addr,
                        .flags = I2C_M_RD,
                        .len = sizeof(lo),
                        .buf = &lo,
                }
        };

        /*
         * Use i2c_transfer instead of smbus read because i2c_transfer
         * does NOT use a stop bit between address write and data read.
         * Using a stop bit causes disjoint upper/lower byte reads and
         * reduces accuracy.
         */
        ret = i2c_transfer(data->client->adapter,
                           msgs, MAX44009_READ_LUX_XFER_LEN);

        if (ret != MAX44009_READ_LUX_XFER_LEN)
                return -EIO;

        return max44009_lux_raw(hi, lo);
}

static int max44009_read_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan, int *val,
                             int *val2, long mask)
{
        struct max44009_data *data = iio_priv(indio_dev);
        int lux_raw;
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_PROCESSED:
                switch (chan->type) {
                case IIO_LIGHT:
                        ret = max44009_read_lux_raw(data);
                        if (ret < 0)
                                return ret;
                        lux_raw = ret;

                        *val = lux_raw * MAX44009_SCALE_NUMERATOR;
                        *val2 = MAX44009_SCALE_DENOMINATOR;
                        return IIO_VAL_FRACTIONAL;
                default:
                        return -EINVAL;
                }
        case IIO_CHAN_INFO_INT_TIME:
                switch (chan->type) {
                case IIO_LIGHT:
                        ret = max44009_read_int_time(data);
                        if (ret < 0)
                                return ret;

                        *val2 = ret;
                        *val = 0;
                        return IIO_VAL_INT_PLUS_NANO;
                default:
                        return -EINVAL;
                }
        default:
                return -EINVAL;
        }
}

static IIO_CONST_ATTR(illuminance_integration_time_available,
                      max44009_int_time_str);

static struct attribute *max44009_attributes[] = {
        &iio_const_attr_illuminance_integration_time_available.dev_attr.attr,
        NULL,
};

static const struct attribute_group max44009_attribute_group = {
        .attrs = max44009_attributes,
};

static int max44009_threshold_byte_from_fraction(int integral, int fractional)
{
        int mantissa, exp;

        if ((integral <= 0 && fractional <= 0) ||
             integral > MAX44009_MAXIMUM_THRESHOLD ||
             (integral == MAX44009_MAXIMUM_THRESHOLD && fractional != 0))
                return -EINVAL;

        /* Reverse scaling of fixed-point integral */
        mantissa = integral * MAX44009_SCALE_DENOMINATOR;
        mantissa /= MAX44009_SCALE_NUMERATOR;

        /* Reverse scaling of fixed-point fractional */
        mantissa += fractional / MAX44009_FRACT_MULT *
                    (MAX44009_SCALE_DENOMINATOR / MAX44009_SCALE_NUMERATOR);

        for (exp = 0; mantissa > 0xff; exp++)
                mantissa >>= 1;

        mantissa >>= 4;
        mantissa &= 0xf;
        exp <<= 4;

        return exp | mantissa;
}

static int max44009_get_thr_reg(enum iio_event_direction dir)
{
        switch (dir) {
        case IIO_EV_DIR_RISING:
                return MAX44009_REG_UPPER_THR;
        case IIO_EV_DIR_FALLING:
                return MAX44009_REG_LOWER_THR;
        default:
                return -EINVAL;
        }
}

static int max44009_write_event_value(struct iio_dev *indio_dev,
                                      const struct iio_chan_spec *chan,
                                      enum iio_event_type type,
                                      enum iio_event_direction dir,
                                      enum iio_event_info info,
                                      int val, int val2)
{
        struct max44009_data *data = iio_priv(indio_dev);
        int reg, threshold;

        if (info != IIO_EV_INFO_VALUE || chan->type != IIO_LIGHT)
                return -EINVAL;

        threshold = max44009_threshold_byte_from_fraction(val, val2);
        if (threshold < 0)
                return threshold;

        reg = max44009_get_thr_reg(dir);
        if (reg < 0)
                return reg;

        return i2c_smbus_write_byte_data(data->client, reg, threshold);
}

static int max44009_read_threshold(struct iio_dev *indio_dev,
                                   enum iio_event_direction dir)
{
        struct max44009_data *data = iio_priv(indio_dev);
        int byte, reg;
        int mantissa, exponent;

        reg = max44009_get_thr_reg(dir);
        if (reg < 0)
                return reg;

        byte = i2c_smbus_read_byte_data(data->client, reg);
        if (byte < 0)
                return byte;

        mantissa = byte & MAX44009_THRESH_MANT_MASK;
        mantissa <<= MAX44009_THRESH_MANT_LSHIFT;

        /*
         * To get the upper threshold, always adds the minimum upper threshold
         * value to the shifted byte value (see datasheet).
         */
        if (dir == IIO_EV_DIR_RISING)
                mantissa += MAX44009_UPPER_THR_MINIMUM;

        /*
         * Exponent is base 2 to the power of the threshold exponent byte
         * value
         */
        exponent = byte & MAX44009_THRESH_EXP_MASK;
        exponent >>= MAX44009_THRESH_EXP_RSHIFT;

        return (1 << exponent) * mantissa;
}

static int max44009_read_event_value(struct iio_dev *indio_dev,
                                     const struct iio_chan_spec *chan,
                                     enum iio_event_type type,
                                     enum iio_event_direction dir,
                                     enum iio_event_info info,
                                     int *val, int *val2)
{
        int ret;
        int threshold;

        if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
                return -EINVAL;

        ret = max44009_read_threshold(indio_dev, dir);
        if (ret < 0)
                return ret;
        threshold = ret;

        *val = threshold * MAX44009_SCALE_NUMERATOR;
        *val2 = MAX44009_SCALE_DENOMINATOR;

        return IIO_VAL_FRACTIONAL;
}

static int max44009_write_event_config(struct iio_dev *indio_dev,
                                       const struct iio_chan_spec *chan,
                                       enum iio_event_type type,
                                       enum iio_event_direction dir,
                                       bool state)
{
        struct max44009_data *data = iio_priv(indio_dev);
        int ret;

        if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
                return -EINVAL;

        ret = i2c_smbus_write_byte_data(data->client,
                                        MAX44009_REG_INT_EN, state);
        if (ret < 0)
                return ret;

        /*
         * Set device to trigger interrupt immediately upon exceeding
         * the threshold limit.
         */
        return i2c_smbus_write_byte_data(data->client,
                                         MAX44009_REG_THR_TIMER, 0);
}

static int max44009_read_event_config(struct iio_dev *indio_dev,
                                      const struct iio_chan_spec *chan,
                                      enum iio_event_type type,
                                      enum iio_event_direction dir)
{
        struct max44009_data *data = iio_priv(indio_dev);

        if (chan->type != IIO_LIGHT || type != IIO_EV_TYPE_THRESH)
                return -EINVAL;

        return i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_EN);
}

static const struct iio_info max44009_info = {
        .read_raw = max44009_read_raw,
        .write_raw = max44009_write_raw,
        .write_raw_get_fmt = max44009_write_raw_get_fmt,
        .read_event_value = max44009_read_event_value,
        .read_event_config = max44009_read_event_config,
        .write_event_value = max44009_write_event_value,
        .write_event_config = max44009_write_event_config,
        .attrs = &max44009_attribute_group,
};

static irqreturn_t max44009_threaded_irq_handler(int irq, void *p)
{
        struct iio_dev *indio_dev = p;
        struct max44009_data *data = iio_priv(indio_dev);
        int ret;

        ret = i2c_smbus_read_byte_data(data->client, MAX44009_REG_INT_STATUS);
        if (ret) {
                iio_push_event(indio_dev,
                               IIO_UNMOD_EVENT_CODE(IIO_LIGHT, 0,
                                                    IIO_EV_TYPE_THRESH,
                                                    IIO_EV_DIR_EITHER),
                               iio_get_time_ns(indio_dev));

                return IRQ_HANDLED;
        }

        return IRQ_NONE;
}

static int max44009_probe(struct i2c_client *client)
{
        struct max44009_data *data;
        struct iio_dev *indio_dev;
        int ret;

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

        data = iio_priv(indio_dev);
        i2c_set_clientdata(client, indio_dev);
        data->client = client;
        indio_dev->info = &max44009_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->name = MAX44009_DRV_NAME;
        indio_dev->channels = max44009_channels;
        indio_dev->num_channels = ARRAY_SIZE(max44009_channels);
        mutex_init(&data->lock);

        /* Clear any stale interrupt bit */
        ret = i2c_smbus_read_byte_data(client, MAX44009_REG_CFG);
        if (ret < 0)
                return ret;

        if (client->irq > 0) {
                ret = devm_request_threaded_irq(&client->dev, client->irq,
                                                NULL,
                                                max44009_threaded_irq_handler,
                                                IRQF_TRIGGER_FALLING |
                                                IRQF_ONESHOT | IRQF_SHARED,
                                                "max44009_event",
                                                indio_dev);
                if (ret < 0)
                        return ret;
        }

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

static const struct of_device_id max44009_of_match[] = {
        { .compatible = "maxim,max44009" },
        { }
};
MODULE_DEVICE_TABLE(of, max44009_of_match);

static const struct i2c_device_id max44009_id[] = {
        { "max44009" },
        { }
};
MODULE_DEVICE_TABLE(i2c, max44009_id);

static struct i2c_driver max44009_driver = {
        .driver = {
                .name = MAX44009_DRV_NAME,
                .of_match_table = max44009_of_match,
        },
        .probe = max44009_probe,
        .id_table = max44009_id,
};
module_i2c_driver(max44009_driver);

MODULE_AUTHOR("Robert Eshleman <bobbyeshleman@gmail.com>");
MODULE_LICENSE("GPL v2");
MODULE_DESCRIPTION("MAX44009 ambient light sensor driver");