/*
 * Driver for Linear Technology LTC4151 High Voltage I2C Current
 * and Voltage Monitor
 *
 * Copyright (C) 2011 AppearTV AS
 *
 * Derived from:
 *
 *  Driver for Linear Technology LTC4261 I2C Negative Voltage Hot
 *  Swap Controller
 *  Copyright (C) 2010 Ericsson AB.
 *
 * Datasheet: http://www.linear.com/docs/Datasheet/4151fc.pdf
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/slab.h>
#include <linux/i2c.h>
#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>
#include <linux/jiffies.h>

/* chip registers */
#define LTC4151_SENSE_H 0x00
#define LTC4151_SENSE_L 0x01
#define LTC4151_VIN_H   0x02
#define LTC4151_VIN_L   0x03
#define LTC4151_ADIN_H  0x04
#define LTC4151_ADIN_L  0x05

struct ltc4151_data {
        struct i2c_client *client;

        struct mutex update_lock;
        bool valid;
        unsigned long last_updated; /* in jiffies */
        unsigned int shunt; /* in micro ohms */

        /* Registers */
        u8 regs[6];
};

static struct ltc4151_data *ltc4151_update_device(struct device *dev)
{
        struct ltc4151_data *data = dev_get_drvdata(dev);
        struct i2c_client *client = data->client;
        struct ltc4151_data *ret = data;

        mutex_lock(&data->update_lock);

        /*
         * The chip's A/D updates 6 times per second
         * (Conversion Rate 6 - 9 Hz)
         */
        if (time_after(jiffies, data->last_updated + HZ / 6) || !data->valid) {
                int i;

                dev_dbg(&client->dev, "Starting ltc4151 update\n");

                /* Read all registers */
                for (i = 0; i < ARRAY_SIZE(data->regs); i++) {
                        int val;

                        val = i2c_smbus_read_byte_data(client, i);
                        if (unlikely(val < 0)) {
                                dev_dbg(dev,
                                        "Failed to read ADC value: error %d\n",
                                        val);
                                ret = ERR_PTR(val);
                                goto abort;
                        }
                        data->regs[i] = val;
                }
                data->last_updated = jiffies;
                data->valid = 1;
        }
abort:
        mutex_unlock(&data->update_lock);
        return ret;
}

/* Return the voltage from the given register in mV */
static int ltc4151_get_value(struct ltc4151_data *data, u8 reg)
{
        u32 val;

        val = (data->regs[reg] << 4) + (data->regs[reg + 1] >> 4);

        switch (reg) {
        case LTC4151_ADIN_H:
                /* 500uV resolution. Convert to mV. */
                val = val * 500 / 1000;
                break;
        case LTC4151_SENSE_H:
                /*
                 * 20uV resolution. Convert to current as measured with
                 * a given sense resistor, in mA.
                 */
                val = val * 20 * 1000 / data->shunt;
                break;
        case LTC4151_VIN_H:
                /* 25 mV per increment */
                val = val * 25;
                break;
        default:
                /* If we get here, the developer messed up */
                WARN_ON_ONCE(1);
                val = 0;
                break;
        }

        return val;
}

static ssize_t ltc4151_show_value(struct device *dev,
                                  struct device_attribute *da, char *buf)
{
        struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
        struct ltc4151_data *data = ltc4151_update_device(dev);
        int value;

        if (IS_ERR(data))
                return PTR_ERR(data);

        value = ltc4151_get_value(data, attr->index);
        return snprintf(buf, PAGE_SIZE, "%d\n", value);
}

/*
 * Input voltages.
 */
static SENSOR_DEVICE_ATTR(in1_input, S_IRUGO, ltc4151_show_value, NULL,
                          LTC4151_VIN_H);
static SENSOR_DEVICE_ATTR(in2_input, S_IRUGO, ltc4151_show_value, NULL,
                          LTC4151_ADIN_H);

/* Currents (via sense resistor) */
static SENSOR_DEVICE_ATTR(curr1_input, S_IRUGO, ltc4151_show_value, NULL,
                          LTC4151_SENSE_H);

/*
 * Finally, construct an array of pointers to members of the above objects,
 * as required for sysfs_create_group()
 */
static struct attribute *ltc4151_attrs[] = {
        &sensor_dev_attr_in1_input.dev_attr.attr,
        &sensor_dev_attr_in2_input.dev_attr.attr,

        &sensor_dev_attr_curr1_input.dev_attr.attr,

        NULL,
};
ATTRIBUTE_GROUPS(ltc4151);

static int ltc4151_probe(struct i2c_client *client,
                         const struct i2c_device_id *id)
{
        struct i2c_adapter *adapter = client->adapter;
        struct device *dev = &client->dev;
        struct ltc4151_data *data;
        struct device *hwmon_dev;
        u32 shunt;

        if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA))
                return -ENODEV;

        data = devm_kzalloc(dev, sizeof(*data), GFP_KERNEL);
        if (!data)
                return -ENOMEM;

        if (of_property_read_u32(client->dev.of_node,
                                 "shunt-resistor-micro-ohms", &shunt))
                shunt = 1000; /* 1 mOhm if not set via DT */

        if (shunt == 0)
                return -EINVAL;

        data->shunt = shunt;

        data->client = client;
        mutex_init(&data->update_lock);

        hwmon_dev = devm_hwmon_device_register_with_groups(dev, client->name,
                                                           data,
                                                           ltc4151_groups);
        return PTR_ERR_OR_ZERO(hwmon_dev);
}

static const struct i2c_device_id ltc4151_id[] = {
        { "ltc4151", 0 },
        { }
};
MODULE_DEVICE_TABLE(i2c, ltc4151_id);

static const struct of_device_id ltc4151_match[] = {
        { .compatible = "lltc,ltc4151" },
        {},
};
MODULE_DEVICE_TABLE(of, ltc4151_match);

/* This is the driver that will be inserted */
static struct i2c_driver ltc4151_driver = {
        .driver = {
                .name   = "ltc4151",
                .of_match_table = of_match_ptr(ltc4151_match),
        },
        .probe          = ltc4151_probe,
        .id_table       = ltc4151_id,
};

module_i2c_driver(ltc4151_driver);

MODULE_AUTHOR("Per Dalen <per.dalen@appeartv.com>");
MODULE_DESCRIPTION("LTC4151 driver");
MODULE_LICENSE("GPL");