/*  Copyright (c) 2010  Christoph Mair <christoph.mair@gmail.com>
 *  Copyright (c) 2012  Bosch Sensortec GmbH
 *  Copyright (c) 2012  Unixphere AB
 *
 *  This driver supports the bmp085 and bmp18x digital barometric pressure
 *  and temperature sensors from Bosch Sensortec. The datasheets
 *  are available from their website:
 *  http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP085-DS000-05.pdf
 *  http://www.bosch-sensortec.com/content/language1/downloads/BST-BMP180-DS000-07.pdf
 *
 *  A pressure measurement is issued by reading from pressure0_input.
 *  The return value ranges from 30000 to 110000 pascal with a resulution
 *  of 1 pascal (0.01 millibar) which enables measurements from 9000m above
 *  to 500m below sea level.
 *
 *  The temperature can be read from temp0_input. Values range from
 *  -400 to 850 representing the ambient temperature in degree celsius
 *  multiplied by 10.The resolution is 0.1 celsius.
 *
 *  Because ambient pressure is temperature dependent, a temperature
 *  measurement will be executed automatically even if the user is reading
 *  from pressure0_input. This happens if the last temperature measurement
 *  has been executed more then one second ago.
 *
 *  To decrease RMS noise from pressure measurements, the bmp085 can
 *  autonomously calculate the average of up to eight samples. This is
 *  set up by writing to the oversampling sysfs file. Accepted values
 *  are 0, 1, 2 and 3. 2^x when x is the value written to this file
 *  specifies the number of samples used to calculate the ambient pressure.
 *  RMS noise is specified with six pascal (without averaging) and decreases
 *  down to 3 pascal when using an oversampling setting of 3.
 *
 *  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/module.h>
#include <linux/device.h>
#include <linux/slab.h>
#include <linux/of.h>
#include "bmp085.h"
#include <linux/interrupt.h>
#include <linux/completion.h>
#include <linux/gpio.h>

#define BMP085_CHIP_ID                  0x55
#define BMP085_CALIBRATION_DATA_START   0xAA
#define BMP085_CALIBRATION_DATA_LENGTH  11      /* 16 bit values */
#define BMP085_CHIP_ID_REG              0xD0
#define BMP085_CTRL_REG                 0xF4
#define BMP085_TEMP_MEASUREMENT         0x2E
#define BMP085_PRESSURE_MEASUREMENT     0x34
#define BMP085_CONVERSION_REGISTER_MSB  0xF6
#define BMP085_CONVERSION_REGISTER_LSB  0xF7
#define BMP085_CONVERSION_REGISTER_XLSB 0xF8
#define BMP085_TEMP_CONVERSION_TIME     5

struct bmp085_calibration_data {
        s16 AC1, AC2, AC3;
        u16 AC4, AC5, AC6;
        s16 B1, B2;
        s16 MB, MC, MD;
};

struct bmp085_data {
        struct  device *dev;
        struct  regmap *regmap;
        struct  mutex lock;
        struct  bmp085_calibration_data calibration;
        u8      oversampling_setting;
        u32     raw_temperature;
        u32     raw_pressure;
        u32     temp_measurement_period;
        unsigned long last_temp_measurement;
        u8      chip_id;
        s32     b6; /* calculated temperature correction coefficient */
        int     irq;
        struct  completion done;
};

static irqreturn_t bmp085_eoc_isr(int irq, void *devid)
{
        struct bmp085_data *data = devid;

        complete(&data->done);

        return IRQ_HANDLED;
}

static s32 bmp085_read_calibration_data(struct bmp085_data *data)
{
        u16 tmp[BMP085_CALIBRATION_DATA_LENGTH];
        struct bmp085_calibration_data *cali = &(data->calibration);
        s32 status = regmap_bulk_read(data->regmap,
                                BMP085_CALIBRATION_DATA_START, (u8 *)tmp,
                                (BMP085_CALIBRATION_DATA_LENGTH << 1));
        if (status < 0)
                return status;

        cali->AC1 =  be16_to_cpu(tmp[0]);
        cali->AC2 =  be16_to_cpu(tmp[1]);
        cali->AC3 =  be16_to_cpu(tmp[2]);
        cali->AC4 =  be16_to_cpu(tmp[3]);
        cali->AC5 =  be16_to_cpu(tmp[4]);
        cali->AC6 = be16_to_cpu(tmp[5]);
        cali->B1 = be16_to_cpu(tmp[6]);
        cali->B2 = be16_to_cpu(tmp[7]);
        cali->MB = be16_to_cpu(tmp[8]);
        cali->MC = be16_to_cpu(tmp[9]);
        cali->MD = be16_to_cpu(tmp[10]);
        return 0;
}

static s32 bmp085_update_raw_temperature(struct bmp085_data *data)
{
        u16 tmp;
        s32 status;

        mutex_lock(&data->lock);

        init_completion(&data->done);

        status = regmap_write(data->regmap, BMP085_CTRL_REG,
                              BMP085_TEMP_MEASUREMENT);
        if (status < 0) {
                dev_err(data->dev,
                        "Error while requesting temperature measurement.\n");
                goto exit;
        }
        wait_for_completion_timeout(&data->done, 1 + msecs_to_jiffies(
                                            BMP085_TEMP_CONVERSION_TIME));

        status = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB,
                                 &tmp, sizeof(tmp));
        if (status < 0) {
                dev_err(data->dev,
                        "Error while reading temperature measurement result\n");
                goto exit;
        }
        data->raw_temperature = be16_to_cpu(tmp);
        data->last_temp_measurement = jiffies;
        status = 0;     /* everything ok, return 0 */

exit:
        mutex_unlock(&data->lock);
        return status;
}

static s32 bmp085_update_raw_pressure(struct bmp085_data *data)
{
        u32 tmp = 0;
        s32 status;

        mutex_lock(&data->lock);

        init_completion(&data->done);

        status = regmap_write(data->regmap, BMP085_CTRL_REG,
                        BMP085_PRESSURE_MEASUREMENT +
                        (data->oversampling_setting << 6));
        if (status < 0) {
                dev_err(data->dev,
                        "Error while requesting pressure measurement.\n");
                goto exit;
        }

        /* wait for the end of conversion */
        wait_for_completion_timeout(&data->done, 1 + msecs_to_jiffies(
                                        2+(3 << data->oversampling_setting)));
        /* copy data into a u32 (4 bytes), but skip the first byte. */
        status = regmap_bulk_read(data->regmap, BMP085_CONVERSION_REGISTER_MSB,
                                 ((u8 *)&tmp)+1, 3);
        if (status < 0) {
                dev_err(data->dev,
                        "Error while reading pressure measurement results\n");
                goto exit;
        }
        data->raw_pressure = be32_to_cpu((tmp));
        data->raw_pressure >>= (8-data->oversampling_setting);
        status = 0;     /* everything ok, return 0 */

exit:
        mutex_unlock(&data->lock);
        return status;
}

/*
 * This function starts the temperature measurement and returns the value
 * in tenth of a degree celsius.
 */
static s32 bmp085_get_temperature(struct bmp085_data *data, int *temperature)
{
        struct bmp085_calibration_data *cali = &data->calibration;
        long x1, x2;
        int status;

        status = bmp085_update_raw_temperature(data);
        if (status < 0)
                goto exit;

        x1 = ((data->raw_temperature - cali->AC6) * cali->AC5) >> 15;
        x2 = (cali->MC << 11) / (x1 + cali->MD);
        data->b6 = x1 + x2 - 4000;
        /* if NULL just update b6. Used for pressure only measurements */
        if (temperature != NULL)
                *temperature = (x1+x2+8) >> 4;

exit:
        return status;
}

/*
 * This function starts the pressure measurement and returns the value
 * in millibar. Since the pressure depends on the ambient temperature,
 * a temperature measurement is executed according to the given temperature
 * measurement period (default is 1 sec boundary). This period could vary
 * and needs to be adjusted according to the sensor environment, i.e. if big
 * temperature variations then the temperature needs to be read out often.
 */
static s32 bmp085_get_pressure(struct bmp085_data *data, int *pressure)
{
        struct bmp085_calibration_data *cali = &data->calibration;
        s32 x1, x2, x3, b3;
        u32 b4, b7;
        s32 p;
        int status;

        /* alt least every second force an update of the ambient temperature */
        if ((data->last_temp_measurement == 0) ||
            time_is_before_jiffies(data->last_temp_measurement + 1*HZ)) {
                status = bmp085_get_temperature(data, NULL);
                if (status < 0)
                        return status;
        }

        status = bmp085_update_raw_pressure(data);
        if (status < 0)
                return status;

        x1 = (data->b6 * data->b6) >> 12;
        x1 *= cali->B2;
        x1 >>= 11;

        x2 = cali->AC2 * data->b6;
        x2 >>= 11;

        x3 = x1 + x2;

        b3 = (((((s32)cali->AC1) * 4 + x3) << data->oversampling_setting) + 2);
        b3 >>= 2;

        x1 = (cali->AC3 * data->b6) >> 13;
        x2 = (cali->B1 * ((data->b6 * data->b6) >> 12)) >> 16;
        x3 = (x1 + x2 + 2) >> 2;
        b4 = (cali->AC4 * (u32)(x3 + 32768)) >> 15;

        b7 = ((u32)data->raw_pressure - b3) *
                                        (50000 >> data->oversampling_setting);
        p = ((b7 < 0x80000000) ? ((b7 << 1) / b4) : ((b7 / b4) * 2));

        x1 = p >> 8;
        x1 *= x1;
        x1 = (x1 * 3038) >> 16;
        x2 = (-7357 * p) >> 16;
        p += (x1 + x2 + 3791) >> 4;

        *pressure = p;

        return 0;
}

/*
 * This function sets the chip-internal oversampling. Valid values are 0..3.
 * The chip will use 2^oversampling samples for internal averaging.
 * This influences the measurement time and the accuracy; larger values
 * increase both. The datasheet gives an overview on how measurement time,
 * accuracy and noise correlate.
 */
static void bmp085_set_oversampling(struct bmp085_data *data,
                                                unsigned char oversampling)
{
        if (oversampling > 3)
                oversampling = 3;
        data->oversampling_setting = oversampling;
}

/*
 * Returns the currently selected oversampling. Range: 0..3
 */
static unsigned char bmp085_get_oversampling(struct bmp085_data *data)
{
        return data->oversampling_setting;
}

/* sysfs callbacks */
static ssize_t set_oversampling(struct device *dev,
                                struct device_attribute *attr,
                                const char *buf, size_t count)
{
        struct bmp085_data *data = dev_get_drvdata(dev);
        unsigned long oversampling;
        int err = kstrtoul(buf, 10, &oversampling);

        if (err == 0) {
                mutex_lock(&data->lock);
                bmp085_set_oversampling(data, oversampling);
                mutex_unlock(&data->lock);
                return count;
        }

        return err;
}

static ssize_t show_oversampling(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        struct bmp085_data *data = dev_get_drvdata(dev);

        return sprintf(buf, "%u\n", bmp085_get_oversampling(data));
}
static DEVICE_ATTR(oversampling, S_IWUSR | S_IRUGO,
                                        show_oversampling, set_oversampling);


static ssize_t show_temperature(struct device *dev,
                                struct device_attribute *attr, char *buf)
{
        int temperature;
        int status;
        struct bmp085_data *data = dev_get_drvdata(dev);

        status = bmp085_get_temperature(data, &temperature);
        if (status < 0)
                return status;
        else
                return sprintf(buf, "%d\n", temperature);
}
static DEVICE_ATTR(temp0_input, S_IRUGO, show_temperature, NULL);


static ssize_t show_pressure(struct device *dev,
                             struct device_attribute *attr, char *buf)
{
        int pressure;
        int status;
        struct bmp085_data *data = dev_get_drvdata(dev);

        status = bmp085_get_pressure(data, &pressure);
        if (status < 0)
                return status;
        else
                return sprintf(buf, "%d\n", pressure);
}
static DEVICE_ATTR(pressure0_input, S_IRUGO, show_pressure, NULL);


static struct attribute *bmp085_attributes[] = {
        &dev_attr_temp0_input.attr,
        &dev_attr_pressure0_input.attr,
        &dev_attr_oversampling.attr,
        NULL
};

static const struct attribute_group bmp085_attr_group = {
        .attrs = bmp085_attributes,
};

int bmp085_detect(struct device *dev)
{
        struct bmp085_data *data = dev_get_drvdata(dev);
        unsigned int id;
        int ret;

        ret = regmap_read(data->regmap, BMP085_CHIP_ID_REG, &id);
        if (ret < 0)
                return ret;

        if (id != data->chip_id)
                return -ENODEV;

        return 0;
}
EXPORT_SYMBOL_GPL(bmp085_detect);

static void bmp085_get_of_properties(struct bmp085_data *data)
{
#ifdef CONFIG_OF
        struct device_node *np = data->dev->of_node;
        u32 prop;

        if (!np)
                return;

        if (!of_property_read_u32(np, "chip-id", &prop))
                data->chip_id = prop & 0xff;

        if (!of_property_read_u32(np, "temp-measurement-period", &prop))
                data->temp_measurement_period = (prop/100)*HZ;

        if (!of_property_read_u32(np, "default-oversampling", &prop))
                data->oversampling_setting = prop & 0xff;
#endif
}

static int bmp085_init_client(struct bmp085_data *data)
{
        int status = bmp085_read_calibration_data(data);

        if (status < 0)
                return status;

        /* default settings */
        data->chip_id = BMP085_CHIP_ID;
        data->last_temp_measurement = 0;
        data->temp_measurement_period = 1*HZ;
        data->oversampling_setting = 3;

        bmp085_get_of_properties(data);

        mutex_init(&data->lock);

        return 0;
}

struct regmap_config bmp085_regmap_config = {
        .reg_bits = 8,
        .val_bits = 8
};
EXPORT_SYMBOL_GPL(bmp085_regmap_config);

int bmp085_probe(struct device *dev, struct regmap *regmap, int irq)
{
        struct bmp085_data *data;
        int err = 0;

        data = kzalloc(sizeof(struct bmp085_data), GFP_KERNEL);
        if (!data) {
                err = -ENOMEM;
                goto exit;
        }

        dev_set_drvdata(dev, data);
        data->dev = dev;
        data->regmap = regmap;
        data->irq = irq;

        if (data->irq > 0) {
                err = devm_request_irq(dev, data->irq, bmp085_eoc_isr,
                                              IRQF_TRIGGER_RISING, "bmp085",
                                              data);
                if (err < 0)
                        goto exit_free;
        }

        /* Initialize the BMP085 chip */
        err = bmp085_init_client(data);
        if (err < 0)
                goto exit_free;

        err = bmp085_detect(dev);
        if (err < 0) {
                dev_err(dev, "%s: chip_id failed!\n", BMP085_NAME);
                goto exit_free;
        }

        /* Register sysfs hooks */
        err = sysfs_create_group(&dev->kobj, &bmp085_attr_group);
        if (err)
                goto exit_free;

        dev_info(dev, "Successfully initialized %s!\n", BMP085_NAME);

        return 0;

exit_free:
        kfree(data);
exit:
        return err;
}
EXPORT_SYMBOL_GPL(bmp085_probe);

int bmp085_remove(struct device *dev)
{
        struct bmp085_data *data = dev_get_drvdata(dev);

        sysfs_remove_group(&data->dev->kobj, &bmp085_attr_group);
        kfree(data);

        return 0;
}
EXPORT_SYMBOL_GPL(bmp085_remove);

MODULE_AUTHOR("Christoph Mair <christoph.mair@gmail.com>");
MODULE_DESCRIPTION("BMP085 driver");
MODULE_LICENSE("GPL");