/*
 * vl6180.c - Support for STMicroelectronics VL6180 ALS, range and proximity
 * sensor
 *
 * Copyright 2017 Peter Meerwald-Stadler <pmeerw@pmeerw.net>
 * Copyright 2017 Manivannan Sadhasivam <manivannanece23@gmail.com>
 *
 * This file is subject to the terms and conditions of version 2 of
 * the GNU General Public License.  See the file COPYING in the main
 * directory of this archive for more details.
 *
 * IIO driver for VL6180 (7-bit I2C slave address 0x29)
 *
 * Range: 0 to 100mm
 * ALS: < 1 Lux up to 100 kLux
 * IR: 850nm
 *
 * TODO: irq, threshold events, continuous mode, hardware buffer
 */

#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/mutex.h>
#include <linux/err.h>
#include <linux/of.h>
#include <linux/delay.h>
#include <linux/util_macros.h>

#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>

#define VL6180_DRV_NAME "vl6180"

/* Device identification register and value */
#define VL6180_MODEL_ID 0x000
#define VL6180_MODEL_ID_VAL 0xb4

/* Configuration registers */
#define VL6180_INTR_CONFIG 0x014
#define VL6180_INTR_CLEAR 0x015
#define VL6180_OUT_OF_RESET 0x016
#define VL6180_HOLD 0x017
#define VL6180_RANGE_START 0x018
#define VL6180_ALS_START 0x038
#define VL6180_ALS_GAIN 0x03f
#define VL6180_ALS_IT 0x040

/* Status registers */
#define VL6180_RANGE_STATUS 0x04d
#define VL6180_ALS_STATUS 0x04e
#define VL6180_INTR_STATUS 0x04f

/* Result value registers */
#define VL6180_ALS_VALUE 0x050
#define VL6180_RANGE_VALUE 0x062
#define VL6180_RANGE_RATE 0x066

/* bits of the RANGE_START and ALS_START register */
#define VL6180_MODE_CONT BIT(1) /* continuous mode */
#define VL6180_STARTSTOP BIT(0) /* start measurement, auto-reset */

/* bits of the INTR_STATUS and INTR_CONFIG register */
#define VL6180_ALS_READY BIT(5)
#define VL6180_RANGE_READY BIT(2)

/* bits of the INTR_CLEAR register */
#define VL6180_CLEAR_ERROR BIT(2)
#define VL6180_CLEAR_ALS BIT(1)
#define VL6180_CLEAR_RANGE BIT(0)

/* bits of the HOLD register */
#define VL6180_HOLD_ON BIT(0)

/* default value for the ALS_IT register */
#define VL6180_ALS_IT_100 0x63 /* 100 ms */

/* values for the ALS_GAIN register */
#define VL6180_ALS_GAIN_1 0x46
#define VL6180_ALS_GAIN_1_25 0x45
#define VL6180_ALS_GAIN_1_67 0x44
#define VL6180_ALS_GAIN_2_5 0x43
#define VL6180_ALS_GAIN_5 0x42
#define VL6180_ALS_GAIN_10 0x41
#define VL6180_ALS_GAIN_20 0x40
#define VL6180_ALS_GAIN_40 0x47

struct vl6180_data {
        struct i2c_client *client;
        struct mutex lock;
        unsigned int als_gain_milli;
        unsigned int als_it_ms;
};

enum { VL6180_ALS, VL6180_RANGE, VL6180_PROX };

/**
 * struct vl6180_chan_regs - Registers for accessing channels
 * @drdy_mask:                  Data ready bit in status register
 * @start_reg:                  Conversion start register
 * @value_reg:                  Result value register
 * @word:                       Register word length
 */
struct vl6180_chan_regs {
        u8 drdy_mask;
        u16 start_reg, value_reg;
        bool word;
};

static const struct vl6180_chan_regs vl6180_chan_regs_table[] = {
        [VL6180_ALS] = {
                .drdy_mask = VL6180_ALS_READY,
                .start_reg = VL6180_ALS_START,
                .value_reg = VL6180_ALS_VALUE,
                .word = true,
        },
        [VL6180_RANGE] = {
                .drdy_mask = VL6180_RANGE_READY,
                .start_reg = VL6180_RANGE_START,
                .value_reg = VL6180_RANGE_VALUE,
                .word = false,
        },
        [VL6180_PROX] = {
                .drdy_mask = VL6180_RANGE_READY,
                .start_reg = VL6180_RANGE_START,
                .value_reg = VL6180_RANGE_RATE,
                .word = true,
        },
};

static int vl6180_read(struct i2c_client *client, u16 cmd, void *databuf,
                       u8 len)
{
        __be16 cmdbuf = cpu_to_be16(cmd);
        struct i2c_msg msgs[2] = {
                { .addr = client->addr, .len = sizeof(cmdbuf), .buf = (u8 *) &cmdbuf },
                { .addr = client->addr, .len = len, .buf = databuf,
                  .flags = I2C_M_RD } };
        int ret;

        ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
        if (ret < 0)
                dev_err(&client->dev, "failed reading register 0x%04x\n", cmd);

        return ret;
}

static int vl6180_read_byte(struct i2c_client *client, u16 cmd)
{
        u8 data;
        int ret;

        ret = vl6180_read(client, cmd, &data, sizeof(data));
        if (ret < 0)
                return ret;

        return data;
}

static int vl6180_read_word(struct i2c_client *client, u16 cmd)
{
        __be16 data;
        int ret;

        ret = vl6180_read(client, cmd, &data, sizeof(data));
        if (ret < 0)
                return ret;

        return be16_to_cpu(data);
}

static int vl6180_write_byte(struct i2c_client *client, u16 cmd, u8 val)
{
        u8 buf[3];
        struct i2c_msg msgs[1] = {
                { .addr = client->addr, .len = sizeof(buf), .buf = (u8 *) &buf } };
        int ret;

        buf[0] = cmd >> 8;
        buf[1] = cmd & 0xff;
        buf[2] = val;

        ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
        if (ret < 0) {
                dev_err(&client->dev, "failed writing register 0x%04x\n", cmd);
                return ret;
        }

        return 0;
}

static int vl6180_write_word(struct i2c_client *client, u16 cmd, u16 val)
{
        __be16 buf[2];
        struct i2c_msg msgs[1] = {
                { .addr = client->addr, .len = sizeof(buf), .buf = (u8 *) &buf } };
        int ret;

        buf[0] = cpu_to_be16(cmd);
        buf[1] = cpu_to_be16(val);

        ret = i2c_transfer(client->adapter, msgs, ARRAY_SIZE(msgs));
        if (ret < 0) {
                dev_err(&client->dev, "failed writing register 0x%04x\n", cmd);
                return ret;
        }

        return 0;
}

static int vl6180_measure(struct vl6180_data *data, int addr)
{
        struct i2c_client *client = data->client;
        int tries = 20, ret;
        u16 value;

        mutex_lock(&data->lock);
        /* Start single shot measurement */
        ret = vl6180_write_byte(client,
                vl6180_chan_regs_table[addr].start_reg, VL6180_STARTSTOP);
        if (ret < 0)
                goto fail;

        while (tries--) {
                ret = vl6180_read_byte(client, VL6180_INTR_STATUS);
                if (ret < 0)
                        goto fail;

                if (ret & vl6180_chan_regs_table[addr].drdy_mask)
                        break;
                msleep(20);
        }

        if (tries < 0) {
                ret = -EIO;
                goto fail;
        }

        /* Read result value from appropriate registers */
        ret = vl6180_chan_regs_table[addr].word ?
                vl6180_read_word(client, vl6180_chan_regs_table[addr].value_reg) :
                vl6180_read_byte(client, vl6180_chan_regs_table[addr].value_reg);
        if (ret < 0)
                goto fail;
        value = ret;

        /* Clear the interrupt flag after data read */
        ret = vl6180_write_byte(client, VL6180_INTR_CLEAR,
                VL6180_CLEAR_ERROR | VL6180_CLEAR_ALS | VL6180_CLEAR_RANGE);
        if (ret < 0)
                goto fail;

        ret = value;

fail:
        mutex_unlock(&data->lock);

        return ret;
}

static const struct iio_chan_spec vl6180_channels[] = {
        {
                .type = IIO_LIGHT,
                .address = VL6180_ALS,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                        BIT(IIO_CHAN_INFO_INT_TIME) |
                        BIT(IIO_CHAN_INFO_SCALE) |
                        BIT(IIO_CHAN_INFO_HARDWAREGAIN),
        }, {
                .type = IIO_DISTANCE,
                .address = VL6180_RANGE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
                        BIT(IIO_CHAN_INFO_SCALE),
        }, {
                .type = IIO_PROXIMITY,
                .address = VL6180_PROX,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
        }
};

/*
 * Available Ambient Light Sensor gain settings, 1/1000th, and
 * corresponding setting for the VL6180_ALS_GAIN register
 */
static const int vl6180_als_gain_tab[8] = {
        1000, 1250, 1670, 2500, 5000, 10000, 20000, 40000
};
static const u8 vl6180_als_gain_tab_bits[8] = {
        VL6180_ALS_GAIN_1,    VL6180_ALS_GAIN_1_25,
        VL6180_ALS_GAIN_1_67, VL6180_ALS_GAIN_2_5,
        VL6180_ALS_GAIN_5,    VL6180_ALS_GAIN_10,
        VL6180_ALS_GAIN_20,   VL6180_ALS_GAIN_40
};

static int vl6180_read_raw(struct iio_dev *indio_dev,
                                struct iio_chan_spec const *chan,
                                int *val, int *val2, long mask)
{
        struct vl6180_data *data = iio_priv(indio_dev);
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                ret = vl6180_measure(data, chan->address);
                if (ret < 0)
                        return ret;
                *val = ret;

                return IIO_VAL_INT;
        case IIO_CHAN_INFO_INT_TIME:
                *val = data->als_it_ms;
                *val2 = 1000;

                return IIO_VAL_FRACTIONAL;

        case IIO_CHAN_INFO_SCALE:
                switch (chan->type) {
                case IIO_LIGHT:
                        /* one ALS count is 0.32 Lux @ gain 1, IT 100 ms */
                        *val = 32000; /* 0.32 * 1000 * 100 */
                        *val2 = data->als_gain_milli * data->als_it_ms;

                        return IIO_VAL_FRACTIONAL;

                case IIO_DISTANCE:
                        *val = 0; /* sensor reports mm, scale to meter */
                        *val2 = 1000;
                        break;
                default:
                        return -EINVAL;
                }

                return IIO_VAL_INT_PLUS_MICRO;
        case IIO_CHAN_INFO_HARDWAREGAIN:
                *val = data->als_gain_milli;
                *val2 = 1000;

                return IIO_VAL_FRACTIONAL;

        default:
                return -EINVAL;
        }
}

static IIO_CONST_ATTR(als_gain_available, "1 1.25 1.67 2.5 5 10 20 40");

static struct attribute *vl6180_attributes[] = {
        &iio_const_attr_als_gain_available.dev_attr.attr,
        NULL
};

static const struct attribute_group vl6180_attribute_group = {
        .attrs = vl6180_attributes,
};

/* HOLD is needed before updating any config registers */
static int vl6180_hold(struct vl6180_data *data, bool hold)
{
        return vl6180_write_byte(data->client, VL6180_HOLD,
                hold ? VL6180_HOLD_ON : 0);
}

static int vl6180_set_als_gain(struct vl6180_data *data, int val, int val2)
{
        int i, ret, gain;

        if (val < 1 || val > 40)
                return -EINVAL;

        gain = (val * 1000000 + val2) / 1000;
        if (gain < 1 || gain > 40000)
                return -EINVAL;

        i = find_closest(gain, vl6180_als_gain_tab,
                         ARRAY_SIZE(vl6180_als_gain_tab));

        mutex_lock(&data->lock);
        ret = vl6180_hold(data, true);
        if (ret < 0)
                goto fail;

        ret = vl6180_write_byte(data->client, VL6180_ALS_GAIN,
                                vl6180_als_gain_tab_bits[i]);

        if (ret >= 0)
                data->als_gain_milli = vl6180_als_gain_tab[i];

fail:
        vl6180_hold(data, false);
        mutex_unlock(&data->lock);
        return ret;
}

static int vl6180_set_it(struct vl6180_data *data, int val, int val2)
{
        int ret, it_ms;

        it_ms = (val2 + 500) / 1000; /* round to ms */
        if (val != 0 || it_ms < 1 || it_ms > 512)
                return -EINVAL;

        mutex_lock(&data->lock);
        ret = vl6180_hold(data, true);
        if (ret < 0)
                goto fail;

        ret = vl6180_write_word(data->client, VL6180_ALS_IT, it_ms - 1);

        if (ret >= 0)
                data->als_it_ms = it_ms;

fail:
        vl6180_hold(data, false);
        mutex_unlock(&data->lock);

        return ret;
}

static int vl6180_write_raw(struct iio_dev *indio_dev,
                             struct iio_chan_spec const *chan,
                             int val, int val2, long mask)
{
        struct vl6180_data *data = iio_priv(indio_dev);

        switch (mask) {
        case IIO_CHAN_INFO_INT_TIME:
                return vl6180_set_it(data, val, val2);

        case IIO_CHAN_INFO_HARDWAREGAIN:
                if (chan->type != IIO_LIGHT)
                        return -EINVAL;

                return vl6180_set_als_gain(data, val, val2);
        default:
                return -EINVAL;
        }
}

static const struct iio_info vl6180_info = {
        .read_raw = vl6180_read_raw,
        .write_raw = vl6180_write_raw,
        .attrs = &vl6180_attribute_group,
};

static int vl6180_init(struct vl6180_data *data)
{
        struct i2c_client *client = data->client;
        int ret;

        ret = vl6180_read_byte(client, VL6180_MODEL_ID);
        if (ret < 0)
                return ret;

        if (ret != VL6180_MODEL_ID_VAL) {
                dev_err(&client->dev, "invalid model ID %02x\n", ret);
                return -ENODEV;
        }

        ret = vl6180_hold(data, true);
        if (ret < 0)
                return ret;

        ret = vl6180_read_byte(client, VL6180_OUT_OF_RESET);
        if (ret < 0)
                return ret;

        /*
         * Detect false reset condition here. This bit is always set when the
         * system comes out of reset.
         */
        if (ret != 0x01)
                dev_info(&client->dev, "device is not fresh out of reset\n");

        /* Enable ALS and Range ready interrupts */
        ret = vl6180_write_byte(client, VL6180_INTR_CONFIG,
                                VL6180_ALS_READY | VL6180_RANGE_READY);
        if (ret < 0)
                return ret;

        /* ALS integration time: 100ms */
        data->als_it_ms = 100;
        ret = vl6180_write_word(client, VL6180_ALS_IT, VL6180_ALS_IT_100);
        if (ret < 0)
                return ret;

        /* ALS gain: 1 */
        data->als_gain_milli = 1000;
        ret = vl6180_write_byte(client, VL6180_ALS_GAIN, VL6180_ALS_GAIN_1);
        if (ret < 0)
                return ret;

        ret = vl6180_write_byte(client, VL6180_OUT_OF_RESET, 0x00);
        if (ret < 0)
                return ret;

        return vl6180_hold(data, false);
}

static int vl6180_probe(struct i2c_client *client,
                          const struct i2c_device_id *id)
{
        struct vl6180_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;
        mutex_init(&data->lock);

        indio_dev->dev.parent = &client->dev;
        indio_dev->info = &vl6180_info;
        indio_dev->channels = vl6180_channels;
        indio_dev->num_channels = ARRAY_SIZE(vl6180_channels);
        indio_dev->name = VL6180_DRV_NAME;
        indio_dev->modes = INDIO_DIRECT_MODE;

        ret = vl6180_init(data);
        if (ret < 0)
                return ret;

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

static const struct of_device_id vl6180_of_match[] = {
        { .compatible = "st,vl6180", },
        { },
};
MODULE_DEVICE_TABLE(of, vl6180_of_match);

static const struct i2c_device_id vl6180_id[] = {
        { "vl6180", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, vl6180_id);

static struct i2c_driver vl6180_driver = {
        .driver = {
                .name   = VL6180_DRV_NAME,
                .of_match_table = of_match_ptr(vl6180_of_match),
        },
        .probe  = vl6180_probe,
        .id_table = vl6180_id,
};

module_i2c_driver(vl6180_driver);

MODULE_AUTHOR("Peter Meerwald-Stadler <pmeerw@pmeerw.net>");
MODULE_AUTHOR("Manivannan Sadhasivam <manivannanece23@gmail.com>");
MODULE_DESCRIPTION("STMicro VL6180 ALS, range and proximity sensor driver");
MODULE_LICENSE("GPL");