// SPDX-License-Identifier: GPL-2.0+
/*
 * Analog Devices AD5110 digital potentiometer driver
 *
 * Copyright (C) 2021 Mugilraj Dhavachelvan <dmugil2000@gmail.com>
 *
 * Datasheet: https://www.analog.com/media/en/technical-documentation/data-sheets/AD5110_5112_5114.pdf
 */

#include <linux/bitfield.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/i2c.h>
#include <linux/module.h>

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

/* AD5110 commands */
#define AD5110_EEPROM_WR        1
#define AD5110_RDAC_WR          2
#define AD5110_SHUTDOWN 3
#define AD5110_RESET            4
#define AD5110_RDAC_RD          5
#define AD5110_EEPROM_RD        6

/* AD5110_EEPROM_RD data */
#define AD5110_WIPER_POS        0
#define AD5110_RESISTOR_TOL     1

#define AD5110_WIPER_RESISTANCE 70

struct ad5110_cfg {
        int max_pos;
        int kohms;
        int shift;
};

enum ad5110_type {
        AD5110_10,
        AD5110_80,
        AD5112_05,
        AD5112_10,
        AD5112_80,
        AD5114_10,
        AD5114_80,
};

static const struct ad5110_cfg ad5110_cfg[] = {
        [AD5110_10] = { .max_pos = 128, .kohms = 10 },
        [AD5110_80] = { .max_pos = 128, .kohms = 80 },
        [AD5112_05] = { .max_pos = 64, .kohms = 5, .shift = 1 },
        [AD5112_10] = { .max_pos = 64, .kohms = 10, .shift = 1 },
        [AD5112_80] = { .max_pos = 64, .kohms = 80, .shift = 1 },
        [AD5114_10] = { .max_pos = 32, .kohms = 10, .shift = 2 },
        [AD5114_80] = { .max_pos = 32, .kohms = 80, .shift = 2 },
};

struct ad5110_data {
        struct i2c_client       *client;
        s16                     tol;            /* resistor tolerance */
        bool                    enable;
        struct mutex            lock;
        const struct ad5110_cfg *cfg;
        /*
         * DMA (thus cache coherency maintenance) may require the
         * transfer buffers to live in their own cache lines.
         */
        u8                      buf[2] __aligned(IIO_DMA_MINALIGN);
};

static const struct iio_chan_spec ad5110_channels[] = {
        {
                .type = IIO_RESISTANCE,
                .output = 1,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_OFFSET) |
                                        BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_ENABLE),
        },
};

static int ad5110_read(struct ad5110_data *data, u8 cmd, int *val)
{
        int ret;

        mutex_lock(&data->lock);
        data->buf[0] = cmd;
        data->buf[1] = *val;

        ret = i2c_master_send_dmasafe(data->client, data->buf, sizeof(data->buf));
        if (ret < 0) {
                goto error;
        } else if (ret != sizeof(data->buf)) {
                ret = -EIO;
                goto error;
        }

        ret = i2c_master_recv_dmasafe(data->client, data->buf, 1);
        if (ret < 0) {
                goto error;
        } else if (ret != 1) {
                ret = -EIO;
                goto error;
        }

        *val = data->buf[0];
        ret = 0;

error:
        mutex_unlock(&data->lock);
        return ret;
}

static int ad5110_write(struct ad5110_data *data, u8 cmd, u8 val)
{
        int ret;

        mutex_lock(&data->lock);
        data->buf[0] = cmd;
        data->buf[1] = val;

        ret = i2c_master_send_dmasafe(data->client, data->buf, sizeof(data->buf));
        if (ret < 0) {
                goto error;
        } else if (ret != sizeof(data->buf)) {
                ret = -EIO;
                goto error;
        }

        ret = 0;

error:
        mutex_unlock(&data->lock);
        return ret;
}

static int ad5110_resistor_tol(struct ad5110_data *data, u8 cmd, int val)
{
        int ret;

        ret = ad5110_read(data, cmd, &val);
        if (ret)
                return ret;

        data->tol = data->cfg->kohms * (val & GENMASK(6, 0)) * 10 / 8;
        if (!(val & BIT(7)))
                data->tol *= -1;

        return 0;
}

static ssize_t store_eeprom_show(struct device *dev,
                                  struct device_attribute *attr,
                                  char *buf)
{
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct ad5110_data *data = iio_priv(indio_dev);
        int val = AD5110_WIPER_POS;
        int ret;

        ret = ad5110_read(data, AD5110_EEPROM_RD, &val);
        if (ret)
                return ret;

        val = val >> data->cfg->shift;
        return iio_format_value(buf, IIO_VAL_INT, 1, &val);
}

static ssize_t store_eeprom_store(struct device *dev,
                                   struct device_attribute *attr,
                                   const char *buf, size_t len)
{
        struct iio_dev *indio_dev = dev_to_iio_dev(dev);
        struct ad5110_data *data = iio_priv(indio_dev);
        int ret;

        ret = ad5110_write(data, AD5110_EEPROM_WR, 0);
        if (ret) {
                dev_err(&data->client->dev, "RDAC to EEPROM write failed\n");
                return ret;
        }

        /* The storing of EEPROM data takes approximately 18 ms. */
        msleep(20);

        return len;
}

static IIO_DEVICE_ATTR_RW(store_eeprom, 0);

static struct attribute *ad5110_attributes[] = {
        &iio_dev_attr_store_eeprom.dev_attr.attr,
        NULL
};

static const struct attribute_group ad5110_attribute_group = {
        .attrs = ad5110_attributes,
};

static int ad5110_read_raw(struct iio_dev *indio_dev,
                           struct iio_chan_spec const *chan,
                           int *val, int *val2, long mask)
{
        struct ad5110_data *data = iio_priv(indio_dev);
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                ret = ad5110_read(data, AD5110_RDAC_RD, val);
                if (ret)
                        return ret;

                *val = *val >> data->cfg->shift;
                return IIO_VAL_INT;
        case IIO_CHAN_INFO_OFFSET:
                *val = AD5110_WIPER_RESISTANCE * data->cfg->max_pos;
                *val2 = 1000 * data->cfg->kohms + data->tol;
                return IIO_VAL_FRACTIONAL;
        case IIO_CHAN_INFO_SCALE:
                *val = 1000 * data->cfg->kohms + data->tol;
                *val2 = data->cfg->max_pos;
                return IIO_VAL_FRACTIONAL;
        case IIO_CHAN_INFO_ENABLE:
                *val = data->enable;
                return IIO_VAL_INT;
        default:
                return -EINVAL;
        }
}

static int ad5110_write_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *chan,
                            int val, int val2, long mask)
{
        struct ad5110_data *data = iio_priv(indio_dev);
        int ret;

        switch (mask) {
        case IIO_CHAN_INFO_RAW:
                if (val > data->cfg->max_pos || val < 0)
                        return -EINVAL;

                return ad5110_write(data, AD5110_RDAC_WR, val << data->cfg->shift);
        case IIO_CHAN_INFO_ENABLE:
                if (val < 0 || val > 1)
                        return -EINVAL;
                if (data->enable == val)
                        return 0;
                ret = ad5110_write(data, AD5110_SHUTDOWN, val ? 0 : 1);
                if (ret)
                        return ret;
                data->enable = val;
                return 0;
        default:
                return -EINVAL;
        }
}

static const struct iio_info ad5110_info = {
        .read_raw = ad5110_read_raw,
        .write_raw = ad5110_write_raw,
        .attrs = &ad5110_attribute_group,
};

#define AD5110_COMPATIBLE(of_compatible, cfg) { \
                        .compatible = of_compatible,    \
                        .data = &ad5110_cfg[cfg],       \
}

static const struct of_device_id ad5110_of_match[] = {
        AD5110_COMPATIBLE("adi,ad5110-10", AD5110_10),
        AD5110_COMPATIBLE("adi,ad5110-80", AD5110_80),
        AD5110_COMPATIBLE("adi,ad5112-05", AD5112_05),
        AD5110_COMPATIBLE("adi,ad5112-10", AD5112_10),
        AD5110_COMPATIBLE("adi,ad5112-80", AD5112_80),
        AD5110_COMPATIBLE("adi,ad5114-10", AD5114_10),
        AD5110_COMPATIBLE("adi,ad5114-80", AD5114_80),
        { }
};
MODULE_DEVICE_TABLE(of, ad5110_of_match);

#define AD5110_ID_TABLE(_name, cfg) {                           \
        .name = _name,                                          \
        .driver_data = (kernel_ulong_t)&ad5110_cfg[cfg],        \
}

static const struct i2c_device_id ad5110_id[] = {
        AD5110_ID_TABLE("ad5110-10", AD5110_10),
        AD5110_ID_TABLE("ad5110-80", AD5110_80),
        AD5110_ID_TABLE("ad5112-05", AD5112_05),
        AD5110_ID_TABLE("ad5112-10", AD5112_10),
        AD5110_ID_TABLE("ad5112-80", AD5112_80),
        AD5110_ID_TABLE("ad5114-10", AD5114_10),
        AD5110_ID_TABLE("ad5114-80", AD5114_80),
        { }
};
MODULE_DEVICE_TABLE(i2c, ad5110_id);

static int ad5110_probe(struct i2c_client *client)
{
        struct device *dev = &client->dev;
        struct iio_dev *indio_dev;
        struct ad5110_data *data;
        int ret;

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

        data = iio_priv(indio_dev);
        data->client = client;
        mutex_init(&data->lock);
        data->enable = 1;
        data->cfg = i2c_get_match_data(client);

        /* refresh RDAC register with EEPROM */
        ret = ad5110_write(data, AD5110_RESET, 0);
        if (ret) {
                dev_err(dev, "Refresh RDAC with EEPROM failed\n");
                return ret;
        }

        ret = ad5110_resistor_tol(data, AD5110_EEPROM_RD, AD5110_RESISTOR_TOL);
        if (ret) {
                dev_err(dev, "Read resistor tolerance failed\n");
                return ret;
        }

        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->info = &ad5110_info;
        indio_dev->channels = ad5110_channels;
        indio_dev->num_channels = ARRAY_SIZE(ad5110_channels);
        indio_dev->name = client->name;

        return devm_iio_device_register(dev, indio_dev);
}

static struct i2c_driver ad5110_driver = {
        .driver = {
                .name   = "ad5110",
                .of_match_table = ad5110_of_match,
        },
        .probe          = ad5110_probe,
        .id_table       = ad5110_id,
};
module_i2c_driver(ad5110_driver);

MODULE_AUTHOR("Mugilraj Dhavachelvan <dmugil2000@gmail.com>");
MODULE_DESCRIPTION("AD5110 digital potentiometer");
MODULE_LICENSE("GPL v2");