/*
 * mcp3021.c - driver for Microchip MCP3021 and MCP3221
 *
 * Copyright (C) 2008-2009, 2012 Freescale Semiconductor, Inc.
 * Author: Mingkai Hu <Mingkai.hu@freescale.com>
 * Reworked by Sven Schuchmann <schuchmann@schleissheimer.de>
 * DT support added by Clemens Gruber <clemens.gruber@pqgruber.com>
 *
 * This driver export the value of analog input voltage to sysfs, the
 * voltage unit is mV. Through the sysfs interface, lm-sensors tool
 * can also display the input voltage.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/hwmon.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/err.h>
#include <linux/device.h>
#include <linux/of.h>
#include <linux/of_device.h>

/* Vdd / reference voltage in millivolt */
#define MCP3021_VDD_REF_MAX     5500
#define MCP3021_VDD_REF_MIN     2700
#define MCP3021_VDD_REF_DEFAULT 3300

/* output format */
#define MCP3021_SAR_SHIFT       2
#define MCP3021_SAR_MASK        0x3ff
#define MCP3021_OUTPUT_RES      10      /* 10-bit resolution */

#define MCP3221_SAR_SHIFT       0
#define MCP3221_SAR_MASK        0xfff
#define MCP3221_OUTPUT_RES      12      /* 12-bit resolution */

enum chips {
        mcp3021,
        mcp3221
};

/*
 * Client data (each client gets its own)
 */
struct mcp3021_data {
        struct device *hwmon_dev;
        u32 vdd;        /* supply and reference voltage in millivolt */
        u16 sar_shift;
        u16 sar_mask;
        u8 output_res;
};

static int mcp3021_read16(struct i2c_client *client)
{
        struct mcp3021_data *data = i2c_get_clientdata(client);
        int ret;
        u16 reg;
        __be16 buf;

        ret = i2c_master_recv(client, (char *)&buf, 2);
        if (ret < 0)
                return ret;
        if (ret != 2)
                return -EIO;

        /* The output code of the MCP3021 is transmitted with MSB first. */
        reg = be16_to_cpu(buf);

        /*
         * The ten-bit output code is composed of the lower 4-bit of the
         * first byte and the upper 6-bit of the second byte.
         */
        reg = (reg >> data->sar_shift) & data->sar_mask;

        return reg;
}

static inline u16 volts_from_reg(struct mcp3021_data *data, u16 val)
{
        return DIV_ROUND_CLOSEST(data->vdd * val, 1 << data->output_res);
}

static ssize_t in0_input_show(struct device *dev,
                              struct device_attribute *attr, char *buf)
{
        struct i2c_client *client = to_i2c_client(dev);
        struct mcp3021_data *data = i2c_get_clientdata(client);
        int reg, in_input;

        reg = mcp3021_read16(client);
        if (reg < 0)
                return reg;

        in_input = volts_from_reg(data, reg);

        return sprintf(buf, "%d\n", in_input);
}

static DEVICE_ATTR_RO(in0_input);

static int mcp3021_probe(struct i2c_client *client,
                                const struct i2c_device_id *id)
{
        int err;
        struct mcp3021_data *data = NULL;
        struct device_node *np = client->dev.of_node;

        if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C))
                return -ENODEV;

        data = devm_kzalloc(&client->dev, sizeof(struct mcp3021_data),
                            GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        i2c_set_clientdata(client, data);

        if (np) {
                if (!of_property_read_u32(np, "reference-voltage-microvolt",
                                          &data->vdd))
                        data->vdd /= 1000;
                else
                        data->vdd = MCP3021_VDD_REF_DEFAULT;
        } else {
                u32 *pdata = dev_get_platdata(&client->dev);

                if (pdata)
                        data->vdd = *pdata;
                else
                        data->vdd = MCP3021_VDD_REF_DEFAULT;
        }

        switch (id->driver_data) {
        case mcp3021:
                data->sar_shift = MCP3021_SAR_SHIFT;
                data->sar_mask = MCP3021_SAR_MASK;
                data->output_res = MCP3021_OUTPUT_RES;
                break;

        case mcp3221:
                data->sar_shift = MCP3221_SAR_SHIFT;
                data->sar_mask = MCP3221_SAR_MASK;
                data->output_res = MCP3221_OUTPUT_RES;
                break;
        }

        if (data->vdd > MCP3021_VDD_REF_MAX || data->vdd < MCP3021_VDD_REF_MIN)
                return -EINVAL;

        err = sysfs_create_file(&client->dev.kobj, &dev_attr_in0_input.attr);
        if (err)
                return err;

        data->hwmon_dev = hwmon_device_register(&client->dev);
        if (IS_ERR(data->hwmon_dev)) {
                err = PTR_ERR(data->hwmon_dev);
                goto exit_remove;
        }

        return 0;

exit_remove:
        sysfs_remove_file(&client->dev.kobj, &dev_attr_in0_input.attr);
        return err;
}

static int mcp3021_remove(struct i2c_client *client)
{
        struct mcp3021_data *data = i2c_get_clientdata(client);

        hwmon_device_unregister(data->hwmon_dev);
        sysfs_remove_file(&client->dev.kobj, &dev_attr_in0_input.attr);

        return 0;
}

static const struct i2c_device_id mcp3021_id[] = {
        { "mcp3021", mcp3021 },
        { "mcp3221", mcp3221 },
        { }
};
MODULE_DEVICE_TABLE(i2c, mcp3021_id);

#ifdef CONFIG_OF
static const struct of_device_id of_mcp3021_match[] = {
        { .compatible = "microchip,mcp3021", .data = (void *)mcp3021 },
        { .compatible = "microchip,mcp3221", .data = (void *)mcp3221 },
        { }
};
MODULE_DEVICE_TABLE(of, of_mcp3021_match);
#endif

static struct i2c_driver mcp3021_driver = {
        .driver = {
                .name = "mcp3021",
                .of_match_table = of_match_ptr(of_mcp3021_match),
        },
        .probe = mcp3021_probe,
        .remove = mcp3021_remove,
        .id_table = mcp3021_id,
};

module_i2c_driver(mcp3021_driver);

MODULE_AUTHOR("Mingkai Hu <Mingkai.hu@freescale.com>");
MODULE_DESCRIPTION("Microchip MCP3021/MCP3221 driver");
MODULE_LICENSE("GPL");