ltc4151.c

Go to the documentation of this file.

/*
 * 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/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 device *hwmon_dev;

    struct mutex update_lock;
    bool valid;
    unsigned long last_updated; /* in jiffies */

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

static struct ltc4151_data *ltc4151_update_device(struct device *dev)
{
    struct i2c_client *client = to_i2c_client(dev);
    struct ltc4151_data *data = i2c_get_clientdata(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
         * an 1 mOhm sense resistor, in mA.
         */
        val = val * 20;
        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_attributes[] = {
    &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,
};

static const struct attribute_group ltc4151_group = {
    .attrs = ltc4151_attributes,
};

static int ltc4151_probe(struct i2c_client *client,
             const struct i2c_device_id *id)
{
    struct i2c_adapter *adapter = client->adapter;
    struct ltc4151_data *data;
    int ret;

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

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

    i2c_set_clientdata(client, data);
    mutex_init(&data->update_lock);

    /* Register sysfs hooks */
    ret = sysfs_create_group(&client->dev.kobj, &ltc4151_group);
    if (ret)
        return ret;

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

    return 0;

out_hwmon_device_register:
    sysfs_remove_group(&client->dev.kobj, &ltc4151_group);
    return ret;
}

static int ltc4151_remove(struct i2c_client *client)
{
    struct ltc4151_data *data = i2c_get_clientdata(client);

    hwmon_device_unregister(data->hwmon_dev);
    sysfs_remove_group(&client->dev.kobj, &ltc4151_group);

    return 0;
}

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

/* This is the driver that will be inserted */
static struct i2c_driver ltc4151_driver = {
    .driver = {
        .name   = "ltc4151",
    },
    .probe      = ltc4151_probe,
    .remove     = ltc4151_remove,
    .id_table   = ltc4151_id,
};

module_i2c_driver(ltc4151_driver);

MODULE_AUTHOR("Per Dalen <[email protected]>");
MODULE_DESCRIPTION("LTC4151 driver");
MODULE_LICENSE("GPL");