ntc_thermistor.c

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/*
 * ntc_thermistor.c - NTC Thermistors
 *
 *  Copyright (C) 2010 Samsung Electronics
 *  MyungJoo Ham <[email protected]>
 *
 * 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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 */

#include <linux/slab.h>
#include <linux/module.h>
#include <linux/pm_runtime.h>
#include <linux/math64.h>
#include <linux/platform_device.h>
#include <linux/err.h>

#include <linux/platform_data/ntc_thermistor.h>

#include <linux/hwmon.h>
#include <linux/hwmon-sysfs.h>

struct ntc_compensation {
    int     temp_C;
    unsigned int    ohm;
};

/*
 * A compensation table should be sorted by the values of .ohm
 * in descending order.
 * The following compensation tables are from the specification of Murata NTC
 * Thermistors Datasheet
 */
const struct ntc_compensation ncpXXwb473[] = {
    { .temp_C   = -40, .ohm = 1747920 },
    { .temp_C   = -35, .ohm = 1245428 },
    { .temp_C   = -30, .ohm = 898485 },
    { .temp_C   = -25, .ohm = 655802 },
    { .temp_C   = -20, .ohm = 483954 },
    { .temp_C   = -15, .ohm = 360850 },
    { .temp_C   = -10, .ohm = 271697 },
    { .temp_C   = -5, .ohm  = 206463 },
    { .temp_C   = 0, .ohm   = 158214 },
    { .temp_C   = 5, .ohm   = 122259 },
    { .temp_C   = 10, .ohm  = 95227 },
    { .temp_C   = 15, .ohm  = 74730 },
    { .temp_C   = 20, .ohm  = 59065 },
    { .temp_C   = 25, .ohm  = 47000 },
    { .temp_C   = 30, .ohm  = 37643 },
    { .temp_C   = 35, .ohm  = 30334 },
    { .temp_C   = 40, .ohm  = 24591 },
    { .temp_C   = 45, .ohm  = 20048 },
    { .temp_C   = 50, .ohm  = 16433 },
    { .temp_C   = 55, .ohm  = 13539 },
    { .temp_C   = 60, .ohm  = 11209 },
    { .temp_C   = 65, .ohm  = 9328 },
    { .temp_C   = 70, .ohm  = 7798 },
    { .temp_C   = 75, .ohm  = 6544 },
    { .temp_C   = 80, .ohm  = 5518 },
    { .temp_C   = 85, .ohm  = 4674 },
    { .temp_C   = 90, .ohm  = 3972 },
    { .temp_C   = 95, .ohm  = 3388 },
    { .temp_C   = 100, .ohm = 2902 },
    { .temp_C   = 105, .ohm = 2494 },
    { .temp_C   = 110, .ohm = 2150 },
    { .temp_C   = 115, .ohm = 1860 },
    { .temp_C   = 120, .ohm = 1615 },
    { .temp_C   = 125, .ohm = 1406 },
};
const struct ntc_compensation ncpXXwl333[] = {
    { .temp_C   = -40, .ohm = 1610154 },
    { .temp_C   = -35, .ohm = 1130850 },
    { .temp_C   = -30, .ohm = 802609 },
    { .temp_C   = -25, .ohm = 575385 },
    { .temp_C   = -20, .ohm = 416464 },
    { .temp_C   = -15, .ohm = 304219 },
    { .temp_C   = -10, .ohm = 224193 },
    { .temp_C   = -5, .ohm  = 166623 },
    { .temp_C   = 0, .ohm   = 124850 },
    { .temp_C   = 5, .ohm   = 94287 },
    { .temp_C   = 10, .ohm  = 71747 },
    { .temp_C   = 15, .ohm  = 54996 },
    { .temp_C   = 20, .ohm  = 42455 },
    { .temp_C   = 25, .ohm  = 33000 },
    { .temp_C   = 30, .ohm  = 25822 },
    { .temp_C   = 35, .ohm  = 20335 },
    { .temp_C   = 40, .ohm  = 16115 },
    { .temp_C   = 45, .ohm  = 12849 },
    { .temp_C   = 50, .ohm  = 10306 },
    { .temp_C   = 55, .ohm  = 8314 },
    { .temp_C   = 60, .ohm  = 6746 },
    { .temp_C   = 65, .ohm  = 5503 },
    { .temp_C   = 70, .ohm  = 4513 },
    { .temp_C   = 75, .ohm  = 3721 },
    { .temp_C   = 80, .ohm  = 3084 },
    { .temp_C   = 85, .ohm  = 2569 },
    { .temp_C   = 90, .ohm  = 2151 },
    { .temp_C   = 95, .ohm  = 1809 },
    { .temp_C   = 100, .ohm = 1529 },
    { .temp_C   = 105, .ohm = 1299 },
    { .temp_C   = 110, .ohm = 1108 },
    { .temp_C   = 115, .ohm = 949 },
    { .temp_C   = 120, .ohm = 817 },
    { .temp_C   = 125, .ohm = 707 },
};

struct ntc_data {
    struct device *hwmon_dev;
    struct ntc_thermistor_platform_data *pdata;
    const struct ntc_compensation *comp;
    struct device *dev;
    int n_comp;
    char name[PLATFORM_NAME_SIZE];
};

static inline u64 div64_u64_safe(u64 dividend, u64 divisor)
{
    if (divisor == 0 && dividend == 0)
        return 0;
    if (divisor == 0)
        return UINT_MAX;
    return div64_u64(dividend, divisor);
}

static int get_ohm_of_thermistor(struct ntc_data *data, unsigned int uV)
{
    struct ntc_thermistor_platform_data *pdata = data->pdata;
    u64 mV = uV / 1000;
    u64 pmV = pdata->pullup_uV / 1000;
    u64 N, puO, pdO;
    puO = pdata->pullup_ohm;
    pdO = pdata->pulldown_ohm;

    if (mV == 0) {
        if (pdata->connect == NTC_CONNECTED_POSITIVE)
            return INT_MAX;
        return 0;
    }
    if (mV >= pmV)
        return (pdata->connect == NTC_CONNECTED_POSITIVE) ?
            0 : INT_MAX;

    if (pdata->connect == NTC_CONNECTED_POSITIVE && puO == 0)
        N = div64_u64_safe(pdO * (pmV - mV), mV);
    else if (pdata->connect == NTC_CONNECTED_GROUND && pdO == 0)
        N = div64_u64_safe(puO * mV, pmV - mV);
    else if (pdata->connect == NTC_CONNECTED_POSITIVE)
        N = div64_u64_safe(pdO * puO * (pmV - mV),
                puO * mV - pdO * (pmV - mV));
    else
        N = div64_u64_safe(pdO * puO * mV, pdO * (pmV - mV) - puO * mV);

    if (N > INT_MAX)
        N = INT_MAX;
    return N;
}

static void lookup_comp(struct ntc_data *data, unsigned int ohm,
            int *i_low, int *i_high)
{
    int start, end, mid;

    /*
     * Handle special cases: Resistance is higher than or equal to
     * resistance in first table entry, or resistance is lower or equal
     * to resistance in last table entry.
     * In these cases, return i_low == i_high, either pointing to the
     * beginning or to the end of the table depending on the condition.
     */
    if (ohm >= data->comp[0].ohm) {
        *i_low = 0;
        *i_high = 0;
        return;
    }
    if (ohm <= data->comp[data->n_comp - 1].ohm) {
        *i_low = data->n_comp - 1;
        *i_high = data->n_comp - 1;
        return;
    }

    /* Do a binary search on compensation table */
    start = 0;
    end = data->n_comp;
    while (start < end) {
        mid = start + (end - start) / 2;
        /*
         * start <= mid < end
         * data->comp[start].ohm > ohm >= data->comp[end].ohm
         *
         * We could check for "ohm == data->comp[mid].ohm" here, but
         * that is a quite unlikely condition, and we would have to
         * check again after updating start. Check it at the end instead
         * for simplicity.
         */
        if (ohm >= data->comp[mid].ohm) {
            end = mid;
        } else {
            start = mid + 1;
            /*
             * ohm >= data->comp[start].ohm might be true here,
             * since we set start to mid + 1. In that case, we are
             * done. We could keep going, but the condition is quite
             * likely to occur, so it is worth checking for it.
             */
            if (ohm >= data->comp[start].ohm)
                end = start;
        }
        /*
         * start <= end
         * data->comp[start].ohm >= ohm >= data->comp[end].ohm
         */
    }
    /*
     * start == end
     * ohm >= data->comp[end].ohm
     */
    *i_low = end;
    if (ohm == data->comp[end].ohm)
        *i_high = end;
    else
        *i_high = end - 1;
}

static int get_temp_mC(struct ntc_data *data, unsigned int ohm)
{
    int low, high;
    int temp;

    lookup_comp(data, ohm, &low, &high);
    if (low == high) {
        /* Unable to use linear approximation */
        temp = data->comp[low].temp_C * 1000;
    } else {
        temp = data->comp[low].temp_C * 1000 +
            ((data->comp[high].temp_C - data->comp[low].temp_C) *
             1000 * ((int)ohm - (int)data->comp[low].ohm)) /
            ((int)data->comp[high].ohm - (int)data->comp[low].ohm);
    }
    return temp;
}

static int ntc_thermistor_get_ohm(struct ntc_data *data)
{
    int read_uV;

    if (data->pdata->read_ohm)
        return data->pdata->read_ohm();

    if (data->pdata->read_uV) {
        read_uV = data->pdata->read_uV();
        if (read_uV < 0)
            return read_uV;
        return get_ohm_of_thermistor(data, read_uV);
    }
    return -EINVAL;
}

static ssize_t ntc_show_name(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct ntc_data *data = dev_get_drvdata(dev);

    return sprintf(buf, "%s\n", data->name);
}

static ssize_t ntc_show_type(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    return sprintf(buf, "4\n");
}

static ssize_t ntc_show_temp(struct device *dev,
        struct device_attribute *attr, char *buf)
{
    struct ntc_data *data = dev_get_drvdata(dev);
    int ohm;

    ohm = ntc_thermistor_get_ohm(data);
    if (ohm < 0)
        return ohm;

    return sprintf(buf, "%d\n", get_temp_mC(data, ohm));
}

static SENSOR_DEVICE_ATTR(temp1_type, S_IRUGO, ntc_show_type, NULL, 0);
static SENSOR_DEVICE_ATTR(temp1_input, S_IRUGO, ntc_show_temp, NULL, 0);
static DEVICE_ATTR(name, S_IRUGO, ntc_show_name, NULL);

static struct attribute *ntc_attributes[] = {
    &dev_attr_name.attr,
    &sensor_dev_attr_temp1_type.dev_attr.attr,
    &sensor_dev_attr_temp1_input.dev_attr.attr,
    NULL,
};

static const struct attribute_group ntc_attr_group = {
    .attrs = ntc_attributes,
};

static int __devinit ntc_thermistor_probe(struct platform_device *pdev)
{
    struct ntc_data *data;
    struct ntc_thermistor_platform_data *pdata = pdev->dev.platform_data;
    int ret = 0;

    if (!pdata) {
        dev_err(&pdev->dev, "No platform init data supplied.\n");
        return -ENODEV;
    }

    /* Either one of the two is required. */
    if (!pdata->read_uV && !pdata->read_ohm) {
        dev_err(&pdev->dev,
            "Both read_uV and read_ohm missing. Need either one of the two.\n");
        return -EINVAL;
    }

    if (pdata->read_uV && pdata->read_ohm) {
        dev_warn(&pdev->dev,
             "Only one of read_uV and read_ohm is needed; ignoring read_uV.\n");
        pdata->read_uV = NULL;
    }

    if (pdata->read_uV && (pdata->pullup_uV == 0 ||
                (pdata->pullup_ohm == 0 && pdata->connect ==
                 NTC_CONNECTED_GROUND) ||
                (pdata->pulldown_ohm == 0 && pdata->connect ==
                 NTC_CONNECTED_POSITIVE) ||
                (pdata->connect != NTC_CONNECTED_POSITIVE &&
                 pdata->connect != NTC_CONNECTED_GROUND))) {
        dev_err(&pdev->dev,
            "Required data to use read_uV not supplied.\n");
        return -EINVAL;
    }

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

    data->dev = &pdev->dev;
    data->pdata = pdata;
    strlcpy(data->name, pdev->id_entry->name, sizeof(data->name));

    switch (pdev->id_entry->driver_data) {
    case TYPE_NCPXXWB473:
        data->comp = ncpXXwb473;
        data->n_comp = ARRAY_SIZE(ncpXXwb473);
        break;
    case TYPE_NCPXXWL333:
        data->comp = ncpXXwl333;
        data->n_comp = ARRAY_SIZE(ncpXXwl333);
        break;
    default:
        dev_err(&pdev->dev, "Unknown device type: %lu(%s)\n",
                pdev->id_entry->driver_data,
                pdev->id_entry->name);
        return -EINVAL;
    }

    platform_set_drvdata(pdev, data);

    ret = sysfs_create_group(&data->dev->kobj, &ntc_attr_group);
    if (ret) {
        dev_err(data->dev, "unable to create sysfs files\n");
        return ret;
    }

    data->hwmon_dev = hwmon_device_register(data->dev);
    if (IS_ERR(data->hwmon_dev)) {
        dev_err(data->dev, "unable to register as hwmon device.\n");
        ret = PTR_ERR(data->hwmon_dev);
        goto err_after_sysfs;
    }

    dev_info(&pdev->dev, "Thermistor %s:%d (type: %s/%lu) successfully probed.\n",
            pdev->name, pdev->id, pdev->id_entry->name,
            pdev->id_entry->driver_data);
    return 0;
err_after_sysfs:
    sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
    return ret;
}

static int __devexit ntc_thermistor_remove(struct platform_device *pdev)
{
    struct ntc_data *data = platform_get_drvdata(pdev);

    hwmon_device_unregister(data->hwmon_dev);
    sysfs_remove_group(&data->dev->kobj, &ntc_attr_group);
    platform_set_drvdata(pdev, NULL);

    return 0;
}

static const struct platform_device_id ntc_thermistor_id[] = {
    { "ncp15wb473", TYPE_NCPXXWB473 },
    { "ncp18wb473", TYPE_NCPXXWB473 },
    { "ncp21wb473", TYPE_NCPXXWB473 },
    { "ncp03wb473", TYPE_NCPXXWB473 },
    { "ncp15wl333", TYPE_NCPXXWL333 },
    { },
};

static struct platform_driver ntc_thermistor_driver = {
    .driver = {
        .name = "ntc-thermistor",
        .owner = THIS_MODULE,
    },
    .probe = ntc_thermistor_probe,
    .remove = __devexit_p(ntc_thermistor_remove),
    .id_table = ntc_thermistor_id,
};

module_platform_driver(ntc_thermistor_driver);

MODULE_DESCRIPTION("NTC Thermistor Driver");
MODULE_AUTHOR("MyungJoo Ham <[email protected]>");
MODULE_LICENSE("GPL");
MODULE_ALIAS("platform:ntc-thermistor");