/*
 * Voltage and current regulation for AD5398 and AD5821
 *
 * Copyright 2010 Analog Devices Inc.
 *
 * Enter bugs at http://blackfin.uclinux.org/
 *
 * Licensed under the GPL-2 or later.
 */

#include <linux/module.h>
#include <linux/err.h>
#include <linux/i2c.h>
#include <linux/slab.h>
#include <linux/platform_device.h>
#include <linux/regulator/driver.h>
#include <linux/regulator/machine.h>

#define AD5398_CURRENT_EN_MASK  0x8000

struct ad5398_chip_info {
        struct i2c_client *client;
        int min_uA;
        int max_uA;
        unsigned int current_level;
        unsigned int current_mask;
        unsigned int current_offset;
        struct regulator_dev *rdev;
};

static int ad5398_calc_current(struct ad5398_chip_info *chip,
        unsigned selector)
{
        unsigned range_uA = chip->max_uA - chip->min_uA;

        return chip->min_uA + (selector * range_uA / chip->current_level);
}

static int ad5398_read_reg(struct i2c_client *client, unsigned short *data)
{
        unsigned short val;
        int ret;

        ret = i2c_master_recv(client, (char *)&val, 2);
        if (ret < 0) {
                dev_err(&client->dev, "I2C read error\n");
                return ret;
        }
        *data = be16_to_cpu(val);

        return ret;
}

static int ad5398_write_reg(struct i2c_client *client, const unsigned short data)
{
        unsigned short val;
        int ret;

        val = cpu_to_be16(data);
        ret = i2c_master_send(client, (char *)&val, 2);
        if (ret != 2) {
                dev_err(&client->dev, "I2C write error\n");
                return ret < 0 ? ret : -EIO;
        }

        return 0;
}

static int ad5398_get_current_limit(struct regulator_dev *rdev)
{
        struct ad5398_chip_info *chip = rdev_get_drvdata(rdev);
        struct i2c_client *client = chip->client;
        unsigned short data;
        int ret;

        ret = ad5398_read_reg(client, &data);
        if (ret < 0)
                return ret;

        ret = (data & chip->current_mask) >> chip->current_offset;

        return ad5398_calc_current(chip, ret);
}

static int ad5398_set_current_limit(struct regulator_dev *rdev, int min_uA, int max_uA)
{
        struct ad5398_chip_info *chip = rdev_get_drvdata(rdev);
        struct i2c_client *client = chip->client;
        unsigned range_uA = chip->max_uA - chip->min_uA;
        unsigned selector;
        unsigned short data;
        int ret;

        if (min_uA < chip->min_uA)
                min_uA = chip->min_uA;
        if (max_uA > chip->max_uA)
                max_uA = chip->max_uA;

        if (min_uA > chip->max_uA || max_uA < chip->min_uA)
                return -EINVAL;

        selector = DIV_ROUND_UP((min_uA - chip->min_uA) * chip->current_level,
                                range_uA);
        if (ad5398_calc_current(chip, selector) > max_uA)
                return -EINVAL;

        dev_dbg(&client->dev, "changing current %duA\n",
                ad5398_calc_current(chip, selector));

        /* read chip enable bit */
        ret = ad5398_read_reg(client, &data);
        if (ret < 0)
                return ret;

        /* prepare register data */
        selector = (selector << chip->current_offset) & chip->current_mask;
        data = (unsigned short)selector | (data & AD5398_CURRENT_EN_MASK);

        /* write the new current value back as well as enable bit */
        ret = ad5398_write_reg(client, data);

        return ret;
}

static int ad5398_is_enabled(struct regulator_dev *rdev)
{
        struct ad5398_chip_info *chip = rdev_get_drvdata(rdev);
        struct i2c_client *client = chip->client;
        unsigned short data;
        int ret;

        ret = ad5398_read_reg(client, &data);
        if (ret < 0)
                return ret;

        if (data & AD5398_CURRENT_EN_MASK)
                return 1;
        else
                return 0;
}

static int ad5398_enable(struct regulator_dev *rdev)
{
        struct ad5398_chip_info *chip = rdev_get_drvdata(rdev);
        struct i2c_client *client = chip->client;
        unsigned short data;
        int ret;

        ret = ad5398_read_reg(client, &data);
        if (ret < 0)
                return ret;

        if (data & AD5398_CURRENT_EN_MASK)
                return 0;

        data |= AD5398_CURRENT_EN_MASK;

        ret = ad5398_write_reg(client, data);

        return ret;
}

static int ad5398_disable(struct regulator_dev *rdev)
{
        struct ad5398_chip_info *chip = rdev_get_drvdata(rdev);
        struct i2c_client *client = chip->client;
        unsigned short data;
        int ret;

        ret = ad5398_read_reg(client, &data);
        if (ret < 0)
                return ret;

        if (!(data & AD5398_CURRENT_EN_MASK))
                return 0;

        data &= ~AD5398_CURRENT_EN_MASK;

        ret = ad5398_write_reg(client, data);

        return ret;
}

static struct regulator_ops ad5398_ops = {
        .get_current_limit = ad5398_get_current_limit,
        .set_current_limit = ad5398_set_current_limit,
        .enable = ad5398_enable,
        .disable = ad5398_disable,
        .is_enabled = ad5398_is_enabled,
};

static const struct regulator_desc ad5398_reg = {
        .name = "isink",
        .id = 0,
        .ops = &ad5398_ops,
        .type = REGULATOR_CURRENT,
        .owner = THIS_MODULE,
};

struct ad5398_current_data_format {
        int current_bits;
        int current_offset;
        int min_uA;
        int max_uA;
};

static const struct ad5398_current_data_format df_10_4_120 = {10, 4, 0, 120000};

static const struct i2c_device_id ad5398_id[] = {
        { "ad5398", (kernel_ulong_t)&df_10_4_120 },
        { "ad5821", (kernel_ulong_t)&df_10_4_120 },
        { }
};
MODULE_DEVICE_TABLE(i2c, ad5398_id);

static int ad5398_probe(struct i2c_client *client,
                                const struct i2c_device_id *id)
{
        struct regulator_init_data *init_data = dev_get_platdata(&client->dev);
        struct regulator_config config = { };
        struct ad5398_chip_info *chip;
        const struct ad5398_current_data_format *df =
                        (struct ad5398_current_data_format *)id->driver_data;

        if (!init_data)
                return -EINVAL;

        chip = devm_kzalloc(&client->dev, sizeof(*chip), GFP_KERNEL);
        if (!chip)
                return -ENOMEM;

        config.dev = &client->dev;
        config.init_data = init_data;
        config.driver_data = chip;

        chip->client = client;

        chip->min_uA = df->min_uA;
        chip->max_uA = df->max_uA;
        chip->current_level = 1 << df->current_bits;
        chip->current_offset = df->current_offset;
        chip->current_mask = (chip->current_level - 1) << chip->current_offset;

        chip->rdev = devm_regulator_register(&client->dev, &ad5398_reg,
                                             &config);
        if (IS_ERR(chip->rdev)) {
                dev_err(&client->dev, "failed to register %s %s\n",
                        id->name, ad5398_reg.name);
                return PTR_ERR(chip->rdev);
        }

        i2c_set_clientdata(client, chip);
        dev_dbg(&client->dev, "%s regulator driver is registered.\n", id->name);
        return 0;
}

static struct i2c_driver ad5398_driver = {
        .probe = ad5398_probe,
        .driver         = {
                .name   = "ad5398",
        },
        .id_table       = ad5398_id,
};

static int __init ad5398_init(void)
{
        return i2c_add_driver(&ad5398_driver);
}
subsys_initcall(ad5398_init);

static void __exit ad5398_exit(void)
{
        i2c_del_driver(&ad5398_driver);
}
module_exit(ad5398_exit);

MODULE_DESCRIPTION("AD5398 and AD5821 current regulator driver");
MODULE_AUTHOR("Sonic Zhang");
MODULE_LICENSE("GPL");