// SPDX-License-Identifier: GPL-2.0-only
/*
 * ltc2485.c - Driver for Linear Technology LTC2485 ADC
 *
 * Copyright (C) 2016 Alison Schofield <amsfield22@gmail.com>
 *
 * Datasheet: http://cds.linear.com/docs/en/datasheet/2485fd.pdf
 */

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

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

/* Power-on configuration: rejects both 50/60Hz, operates at 1x speed */
#define LTC2485_CONFIG_DEFAULT          0

struct ltc2485_data {
        struct i2c_client       *client;
        ktime_t                 time_prev;      /* last conversion */
};

static void ltc2485_wait_conv(struct ltc2485_data *data)
{
        const unsigned int conv_time = 147;     /* conversion time ms */
        unsigned int time_elapsed;

        /* delay if conversion time not passed since last read or write */
        time_elapsed = ktime_ms_delta(ktime_get(), data->time_prev);

        if (time_elapsed < conv_time)
                msleep(conv_time - time_elapsed);
}

static int ltc2485_read(struct ltc2485_data *data, int *val)
{
        struct i2c_client *client = data->client;
        __be32 buf = 0;
        int ret;

        ltc2485_wait_conv(data);

        ret = i2c_master_recv(client, (char *)&buf, 4);
        if (ret < 0)  {
                dev_err(&client->dev, "i2c_master_recv failed\n");
                return ret;
        }
        data->time_prev = ktime_get();
        *val = sign_extend32(be32_to_cpu(buf) >> 6, 24);

        return ret;
}

static int ltc2485_read_raw(struct iio_dev *indio_dev,
                            struct iio_chan_spec const *chan,
                            int *val, int *val2, long mask)
{
        struct ltc2485_data *data = iio_priv(indio_dev);
        int ret;

        if (mask == IIO_CHAN_INFO_RAW) {
                ret = ltc2485_read(data, val);
                if (ret < 0)
                        return ret;

                return IIO_VAL_INT;

        } else if (mask == IIO_CHAN_INFO_SCALE) {
                *val = 5000;                    /* on board vref millivolts */
                *val2 = 25;                     /* 25 (24 + sign) data bits */
                return IIO_VAL_FRACTIONAL_LOG2;

        } else {
                return -EINVAL;
        }
}

static const struct iio_chan_spec ltc2485_channel[] = {
        {
                .type = IIO_VOLTAGE,
                .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
                .info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE)
        },
};

static const struct iio_info ltc2485_info = {
        .read_raw = ltc2485_read_raw,
};

static int ltc2485_probe(struct i2c_client *client)
{
        const struct i2c_device_id *id = i2c_client_get_device_id(client);
        struct iio_dev *indio_dev;
        struct ltc2485_data *data;
        int ret;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C |
                                     I2C_FUNC_SMBUS_WRITE_BYTE))
                return -EOPNOTSUPP;

        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->name = id->name;
        indio_dev->info = &ltc2485_info;
        indio_dev->modes = INDIO_DIRECT_MODE;
        indio_dev->channels = ltc2485_channel;
        indio_dev->num_channels = ARRAY_SIZE(ltc2485_channel);

        ret = i2c_smbus_write_byte(data->client, LTC2485_CONFIG_DEFAULT);
        if (ret < 0)
                return ret;

        data->time_prev = ktime_get();

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

static const struct i2c_device_id ltc2485_id[] = {
        { .name = "ltc2485" },
        { }
};
MODULE_DEVICE_TABLE(i2c, ltc2485_id);

static struct i2c_driver ltc2485_driver = {
        .driver = {
                .name = "ltc2485",
        },
        .probe = ltc2485_probe,
        .id_table = ltc2485_id,
};
module_i2c_driver(ltc2485_driver);

MODULE_AUTHOR("Alison Schofield <amsfield22@gmail.com>");
MODULE_DESCRIPTION("Linear Technology LTC2485 ADC driver");
MODULE_LICENSE("GPL v2");