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linux-next/drivers/iio/pressure/bmp280.c
Irina Tirdea abad398337 iio: pressure: bmp280: fix temp compensation 
Temperature reads on bmp280 device always return 0,
due to a missing step in the compensation formula
(data->tfine is never initialized).

Initialize data->tfine value so we get correct
temperature and pressure values.

Signed-off-by: Irina Tirdea <irina.tirdea@intel.com>
Reviewed-by: Vlad Dogaru <vlad.dogaru@intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
2015-04-09 12:54:10 +01:00

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/*
* Copyright (c) 2014 Intel Corporation
*
* Driver for Bosch Sensortec BMP280 digital pressure sensor.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
*/
#define pr_fmt(fmt) "bmp280: " fmt
#include <linux/module.h>
#include <linux/i2c.h>
#include <linux/acpi.h>
#include <linux/regmap.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#define BMP280_REG_TEMP_XLSB 0xFC
#define BMP280_REG_TEMP_LSB 0xFB
#define BMP280_REG_TEMP_MSB 0xFA
#define BMP280_REG_PRESS_XLSB 0xF9
#define BMP280_REG_PRESS_LSB 0xF8
#define BMP280_REG_PRESS_MSB 0xF7
#define BMP280_REG_CONFIG 0xF5
#define BMP280_REG_CTRL_MEAS 0xF4
#define BMP280_REG_STATUS 0xF3
#define BMP280_REG_RESET 0xE0
#define BMP280_REG_ID 0xD0
#define BMP280_REG_COMP_TEMP_START 0x88
#define BMP280_COMP_TEMP_REG_COUNT 6
#define BMP280_REG_COMP_PRESS_START 0x8E
#define BMP280_COMP_PRESS_REG_COUNT 18
#define BMP280_FILTER_MASK (BIT(4) | BIT(3) | BIT(2))
#define BMP280_FILTER_OFF 0
#define BMP280_FILTER_2X BIT(2)
#define BMP280_FILTER_4X BIT(3)
#define BMP280_FILTER_8X (BIT(3) | BIT(2))
#define BMP280_FILTER_16X BIT(4)
#define BMP280_OSRS_TEMP_MASK (BIT(7) | BIT(6) | BIT(5))
#define BMP280_OSRS_TEMP_SKIP 0
#define BMP280_OSRS_TEMP_1X BIT(5)
#define BMP280_OSRS_TEMP_2X BIT(6)
#define BMP280_OSRS_TEMP_4X (BIT(6) | BIT(5))
#define BMP280_OSRS_TEMP_8X BIT(7)
#define BMP280_OSRS_TEMP_16X (BIT(7) | BIT(5))
#define BMP280_OSRS_PRESS_MASK (BIT(4) | BIT(3) | BIT(2))
#define BMP280_OSRS_PRESS_SKIP 0
#define BMP280_OSRS_PRESS_1X BIT(2)
#define BMP280_OSRS_PRESS_2X BIT(3)
#define BMP280_OSRS_PRESS_4X (BIT(3) | BIT(2))
#define BMP280_OSRS_PRESS_8X BIT(4)
#define BMP280_OSRS_PRESS_16X (BIT(4) | BIT(2))
#define BMP280_MODE_MASK (BIT(1) | BIT(0))
#define BMP280_MODE_SLEEP 0
#define BMP280_MODE_FORCED BIT(0)
#define BMP280_MODE_NORMAL (BIT(1) | BIT(0))
#define BMP280_CHIP_ID 0x58
#define BMP280_SOFT_RESET_VAL 0xB6
struct bmp280_data {
struct i2c_client *client;
struct mutex lock;
struct regmap *regmap;
/*
* Carryover value from temperature conversion, used in pressure
* calculation.
*/
s32 t_fine;
};
/*
* These enums are used for indexing into the array of compensation
* parameters.
*/
enum { T1, T2, T3 };
enum { P1, P2, P3, P4, P5, P6, P7, P8, P9 };
static const struct iio_chan_spec bmp280_channels[] = {
{
.type = IIO_PRESSURE,
.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
},
{
.type = IIO_TEMP,
.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED),
},
};
static bool bmp280_is_writeable_reg(struct device *dev, unsigned int reg)
{
switch (reg) {
case BMP280_REG_CONFIG:
case BMP280_REG_CTRL_MEAS:
case BMP280_REG_RESET:
return true;
default:
return false;
};
}
static bool bmp280_is_volatile_reg(struct device *dev, unsigned int reg)
{
switch (reg) {
case BMP280_REG_TEMP_XLSB:
case BMP280_REG_TEMP_LSB:
case BMP280_REG_TEMP_MSB:
case BMP280_REG_PRESS_XLSB:
case BMP280_REG_PRESS_LSB:
case BMP280_REG_PRESS_MSB:
case BMP280_REG_STATUS:
return true;
default:
return false;
}
}
static const struct regmap_config bmp280_regmap_config = {
.reg_bits = 8,
.val_bits = 8,
.max_register = BMP280_REG_TEMP_XLSB,
.cache_type = REGCACHE_RBTREE,
.writeable_reg = bmp280_is_writeable_reg,
.volatile_reg = bmp280_is_volatile_reg,
};
/*
* Returns temperature in DegC, resolution is 0.01 DegC. Output value of
* "5123" equals 51.23 DegC. t_fine carries fine temperature as global
* value.
*
* Taken from datasheet, Section 3.11.3, "Compensation formula".
*/
static s32 bmp280_compensate_temp(struct bmp280_data *data,
s32 adc_temp)
{
int ret;
s32 var1, var2;
__le16 buf[BMP280_COMP_TEMP_REG_COUNT / 2];
ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_TEMP_START,
buf, BMP280_COMP_TEMP_REG_COUNT);
if (ret < 0) {
dev_err(&data->client->dev,
"failed to read temperature calibration parameters\n");
return ret;
}
/*
* The double casts are necessary because le16_to_cpu returns an
* unsigned 16-bit value. Casting that value directly to a
* signed 32-bit will not do proper sign extension.
*
* Conversely, T1 and P1 are unsigned values, so they can be
* cast straight to the larger type.
*/
var1 = (((adc_temp >> 3) - ((s32)le16_to_cpu(buf[T1]) << 1)) *
((s32)(s16)le16_to_cpu(buf[T2]))) >> 11;
var2 = (((((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1]))) *
((adc_temp >> 4) - ((s32)le16_to_cpu(buf[T1])))) >> 12) *
((s32)(s16)le16_to_cpu(buf[T3]))) >> 14;
data->t_fine = var1 + var2;
return (data->t_fine * 5 + 128) >> 8;
}
/*
* Returns pressure in Pa as unsigned 32 bit integer in Q24.8 format (24
* integer bits and 8 fractional bits). Output value of "24674867"
* represents 24674867/256 = 96386.2 Pa = 963.862 hPa
*
* Taken from datasheet, Section 3.11.3, "Compensation formula".
*/
static u32 bmp280_compensate_press(struct bmp280_data *data,
s32 adc_press)
{
int ret;
s64 var1, var2, p;
__le16 buf[BMP280_COMP_PRESS_REG_COUNT / 2];
ret = regmap_bulk_read(data->regmap, BMP280_REG_COMP_PRESS_START,
buf, BMP280_COMP_PRESS_REG_COUNT);
if (ret < 0) {
dev_err(&data->client->dev,
"failed to read pressure calibration parameters\n");
return ret;
}
var1 = ((s64)data->t_fine) - 128000;
var2 = var1 * var1 * (s64)(s16)le16_to_cpu(buf[P6]);
var2 += (var1 * (s64)(s16)le16_to_cpu(buf[P5])) << 17;
var2 += ((s64)(s16)le16_to_cpu(buf[P4])) << 35;
var1 = ((var1 * var1 * (s64)(s16)le16_to_cpu(buf[P3])) >> 8) +
((var1 * (s64)(s16)le16_to_cpu(buf[P2])) << 12);
var1 = ((((s64)1) << 47) + var1) * ((s64)le16_to_cpu(buf[P1])) >> 33;
if (var1 == 0)
return 0;
p = ((((s64)1048576 - adc_press) << 31) - var2) * 3125;
p = div64_s64(p, var1);
var1 = (((s64)(s16)le16_to_cpu(buf[P9])) * (p >> 13) * (p >> 13)) >> 25;
var2 = (((s64)(s16)le16_to_cpu(buf[P8])) * p) >> 19;
p = ((p + var1 + var2) >> 8) + (((s64)(s16)le16_to_cpu(buf[P7])) << 4);
return (u32)p;
}
static int bmp280_read_temp(struct bmp280_data *data,
int *val)
{
int ret;
__be32 tmp = 0;
s32 adc_temp, comp_temp;
ret = regmap_bulk_read(data->regmap, BMP280_REG_TEMP_MSB,
(u8 *) &tmp, 3);
if (ret < 0) {
dev_err(&data->client->dev, "failed to read temperature\n");
return ret;
}
adc_temp = be32_to_cpu(tmp) >> 12;
comp_temp = bmp280_compensate_temp(data, adc_temp);
/*
* val might be NULL if we're called by the read_press routine,
* who only cares about the carry over t_fine value.
*/
if (val) {
*val = comp_temp * 10;
return IIO_VAL_INT;
}
return 0;
}
static int bmp280_read_press(struct bmp280_data *data,
int *val, int *val2)
{
int ret;
__be32 tmp = 0;
s32 adc_press;
u32 comp_press;
/* Read and compensate temperature so we get a reading of t_fine. */
ret = bmp280_read_temp(data, NULL);
if (ret < 0)
return ret;
ret = regmap_bulk_read(data->regmap, BMP280_REG_PRESS_MSB,
(u8 *) &tmp, 3);
if (ret < 0) {
dev_err(&data->client->dev, "failed to read pressure\n");
return ret;
}
adc_press = be32_to_cpu(tmp) >> 12;
comp_press = bmp280_compensate_press(data, adc_press);
*val = comp_press;
*val2 = 256000;
return IIO_VAL_FRACTIONAL;
}
static int bmp280_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
int ret;
struct bmp280_data *data = iio_priv(indio_dev);
mutex_lock(&data->lock);
switch (mask) {
case IIO_CHAN_INFO_PROCESSED:
switch (chan->type) {
case IIO_PRESSURE:
ret = bmp280_read_press(data, val, val2);
break;
case IIO_TEMP:
ret = bmp280_read_temp(data, val);
break;
default:
ret = -EINVAL;
break;
}
break;
default:
ret = -EINVAL;
break;
}
mutex_unlock(&data->lock);
return ret;
}
static const struct iio_info bmp280_info = {
.driver_module = THIS_MODULE,
.read_raw = &bmp280_read_raw,
};
static int bmp280_chip_init(struct bmp280_data *data)
{
int ret;
ret = regmap_update_bits(data->regmap, BMP280_REG_CTRL_MEAS,
BMP280_OSRS_TEMP_MASK |
BMP280_OSRS_PRESS_MASK |
BMP280_MODE_MASK,
BMP280_OSRS_TEMP_2X |
BMP280_OSRS_PRESS_16X |
BMP280_MODE_NORMAL);
if (ret < 0) {
dev_err(&data->client->dev,
"failed to write ctrl_meas register\n");
return ret;
}
ret = regmap_update_bits(data->regmap, BMP280_REG_CONFIG,
BMP280_FILTER_MASK,
BMP280_FILTER_4X);
if (ret < 0) {
dev_err(&data->client->dev,
"failed to write config register\n");
return ret;
}
return ret;
}
static int bmp280_probe(struct i2c_client *client,
const struct i2c_device_id *id)
{
int ret;
struct iio_dev *indio_dev;
struct bmp280_data *data;
unsigned int chip_id;
indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
data = iio_priv(indio_dev);
mutex_init(&data->lock);
data->client = client;
indio_dev->dev.parent = &client->dev;
indio_dev->name = id->name;
indio_dev->channels = bmp280_channels;
indio_dev->num_channels = ARRAY_SIZE(bmp280_channels);
indio_dev->info = &bmp280_info;
indio_dev->modes = INDIO_DIRECT_MODE;
data->regmap = devm_regmap_init_i2c(client, &bmp280_regmap_config);
if (IS_ERR(data->regmap)) {
dev_err(&client->dev, "failed to allocate register map\n");
return PTR_ERR(data->regmap);
}
ret = regmap_read(data->regmap, BMP280_REG_ID, &chip_id);
if (ret < 0)
return ret;
if (chip_id != BMP280_CHIP_ID) {
dev_err(&client->dev, "bad chip id. expected %x got %x\n",
BMP280_CHIP_ID, chip_id);
return -EINVAL;
}
ret = bmp280_chip_init(data);
if (ret < 0)
return ret;
return devm_iio_device_register(&client->dev, indio_dev);
}
static const struct acpi_device_id bmp280_acpi_match[] = {
{"BMP0280", 0},
{ },
};
MODULE_DEVICE_TABLE(acpi, bmp280_acpi_match);
static const struct i2c_device_id bmp280_id[] = {
{"bmp280", 0},
{ },
};
MODULE_DEVICE_TABLE(i2c, bmp280_id);
static struct i2c_driver bmp280_driver = {
.driver = {
.name = "bmp280",
.acpi_match_table = ACPI_PTR(bmp280_acpi_match),
},
.probe = bmp280_probe,
.id_table = bmp280_id,
};
module_i2c_driver(bmp280_driver);
MODULE_AUTHOR("Vlad Dogaru <vlad.dogaru@intel.com>");
MODULE_DESCRIPTION("Driver for Bosch Sensortec BMP280 pressure and temperature sensor");
MODULE_LICENSE("GPL v2");
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