linux/drivers/misc/bmp085.c
Eric Andersson 985087dbcb misc: add support for bmp18x chips to the bmp085 driver
The bmp18x chip family comes in an I2C respectively SPI variant.
Hence, the bmp085 driver was split to support both buses.

Tested-by: Zhengguang Guo <zhengguang.guo@bosch-sensortec.com>
Reviewed-by: Stefan Nilsson <stefan.nilsson@unixphere.com>
Signed-off-by: Eric Andersson <eric.andersson@unixphere.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-04-18 14:57:14 -07:00

478 lines
13 KiB
C

/* 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/init.h>
#include <linux/slab.h>
#include <linux/delay.h>
#include <linux/of.h>
#include "bmp085.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 */
};
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);
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;
}
msleep(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);
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 */
msleep(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 __init 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);
__devinit int bmp085_probe(struct device *dev, struct regmap *regmap)
{
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;
/* 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");