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alistair23-linux/drivers/iio/temperature/max31856.c
Andrea Merello ea4103070f iio: max31856: add support for runtime-configuring the thermocouple type 
The sensor support various thermocouple types (e.g. J, K, N, ...). The
driver allows to configure this parameter using a DT property.

This is useful when i.e. the thermocouple is physically tied to the sensor
and it is usually not removed, or when it is at least known in advance
which sensor will be connected to the circuit.

However, if the user can randomly connect any kind of thermocouples (i.e.
the device exposes a connector, and the user is free to connect its own
sensors), it would be more appropriate to provide a mechanism to
dynamically switch from one thermocouple type to another. This can be i.e.
handled in userspace by a GUI, a configuration file or a program that
detects the thermocouple type by reading a GPIO, or a eeprom on the probe,
or whatever.

This patch adds a IIO attribute that can be used to override, at run-time,
the DT-provided setting (which serves as default).

Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Patrick Havelange <patrick.havelange@essensium.com>
Cc: Matt Weber <matthew.weber@rockwellcollins.com>
Cc: Matt Ranostay <matt.ranostay@konsulko.com>
Cc: Chuhong Yuan <hslester96@gmail.com>
Cc: Daniel Gomez <dagmcr@gmail.com>
Cc: linux-iio@vger.kernel.org
Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
2019-11-23 12:42:16 +00:00

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// SPDX-License-Identifier: GPL-2.0
/* max31856.c
*
* Maxim MAX31856 thermocouple sensor driver
*
* Copyright (C) 2018-2019 Rockwell Collins
*/
#include <linux/ctype.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/err.h>
#include <linux/spi/spi.h>
#include <linux/iio/iio.h>
#include <linux/iio/sysfs.h>
#include <linux/util_macros.h>
#include <dt-bindings/iio/temperature/thermocouple.h>
/*
* The MSB of the register value determines whether the following byte will
* be written or read. If it is 0, one or more byte reads will follow.
*/
#define MAX31856_RD_WR_BIT BIT(7)
#define MAX31856_CR0_AUTOCONVERT BIT(7)
#define MAX31856_CR0_1SHOT BIT(6)
#define MAX31856_CR0_OCFAULT BIT(4)
#define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)
#define MAX31856_CR0_FILTER_50HZ BIT(0)
#define MAX31856_AVERAGING_MASK GENMASK(6, 4)
#define MAX31856_AVERAGING_SHIFT 4
#define MAX31856_TC_TYPE_MASK GENMASK(3, 0)
#define MAX31856_FAULT_OVUV BIT(1)
#define MAX31856_FAULT_OPEN BIT(0)
/* The MAX31856 registers */
#define MAX31856_CR0_REG 0x00
#define MAX31856_CR1_REG 0x01
#define MAX31856_MASK_REG 0x02
#define MAX31856_CJHF_REG 0x03
#define MAX31856_CJLF_REG 0x04
#define MAX31856_LTHFTH_REG 0x05
#define MAX31856_LTHFTL_REG 0x06
#define MAX31856_LTLFTH_REG 0x07
#define MAX31856_LTLFTL_REG 0x08
#define MAX31856_CJTO_REG 0x09
#define MAX31856_CJTH_REG 0x0A
#define MAX31856_CJTL_REG 0x0B
#define MAX31856_LTCBH_REG 0x0C
#define MAX31856_LTCBM_REG 0x0D
#define MAX31856_LTCBL_REG 0x0E
#define MAX31856_SR_REG 0x0F
static const struct iio_chan_spec max31856_channels[] = {
{ /* Thermocouple Temperature */
.type = IIO_TEMP,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |
BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),
.info_mask_shared_by_type =
BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
},
{ /* Cold Junction Temperature */
.type = IIO_TEMP,
.channel2 = IIO_MOD_TEMP_AMBIENT,
.modified = 1,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
.info_mask_shared_by_type =
BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)
},
};
struct max31856_data {
struct spi_device *spi;
u32 thermocouple_type;
bool filter_50hz;
int averaging;
};
static const char max31856_tc_types[] = {
'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'
};
static int max31856_read(struct max31856_data *data, u8 reg,
u8 val[], unsigned int read_size)
{
return spi_write_then_read(data->spi, &reg, 1, val, read_size);
}
static int max31856_write(struct max31856_data *data, u8 reg,
unsigned int val)
{
u8 buf[2];
buf[0] = reg | (MAX31856_RD_WR_BIT);
buf[1] = val;
return spi_write(data->spi, buf, 2);
}
static int max31856_init(struct max31856_data *data)
{
int ret;
u8 reg_cr0_val, reg_cr1_val;
/* Start by changing to Off mode before making changes as
* some settings are recommended to be set only when the device
* is off
*/
ret = max31856_read(data, MAX31856_CR0_REG, &reg_cr0_val, 1);
if (ret)
return ret;
reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT;
ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
if (ret)
return ret;
/* Set thermocouple type based on dts property */
ret = max31856_read(data, MAX31856_CR1_REG, &reg_cr1_val, 1);
if (ret)
return ret;
reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;
reg_cr1_val |= data->thermocouple_type;
reg_cr1_val &= ~MAX31856_AVERAGING_MASK;
reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT;
ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);
if (ret)
return ret;
/*
* Enable Open circuit fault detection
* Read datasheet for more information: Table 4.
* Value 01 means : Enabled (Once every 16 conversions)
*/
reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK;
reg_cr0_val |= MAX31856_CR0_OCFAULT;
/* Set Auto Conversion Mode */
reg_cr0_val &= ~MAX31856_CR0_1SHOT;
reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;
if (data->filter_50hz)
reg_cr0_val |= MAX31856_CR0_FILTER_50HZ;
else
reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ;
return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);
}
static int max31856_thermocouple_read(struct max31856_data *data,
struct iio_chan_spec const *chan,
int *val)
{
int ret, offset_cjto;
u8 reg_val[3];
switch (chan->channel2) {
case IIO_NO_MOD:
/*
* Multibyte Read
* MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG
*/
ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3);
if (ret)
return ret;
/* Skip last 5 dead bits of LTCBL */
*val = (reg_val[0] << 16 | reg_val[1] << 8 | reg_val[2]) >> 5;
/* Check 7th bit of LTCBH reg. value for sign*/
if (reg_val[0] & 0x80)
*val -= 0x80000;
break;
case IIO_MOD_TEMP_AMBIENT:
/*
* Multibyte Read
* MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG
*/
ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3);
if (ret)
return ret;
/* Get Cold Junction Temp. offset register value */
offset_cjto = reg_val[0];
/* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */
*val = (reg_val[1] << 8 | reg_val[2]) >> 2;
/* As per datasheet add offset into CJTH and CJTL */
*val += offset_cjto;
/* Check 7th bit of CJTH reg. value for sign */
if (reg_val[1] & 0x80)
*val -= 0x4000;
break;
default:
return -EINVAL;
}
ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1);
if (ret)
return ret;
/* Check for over/under voltage or open circuit fault */
if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN))
return -EIO;
return ret;
}
static int max31856_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
struct max31856_data *data = iio_priv(indio_dev);
int ret;
switch (mask) {
case IIO_CHAN_INFO_RAW:
ret = max31856_thermocouple_read(data, chan, val);
if (ret)
return ret;
return IIO_VAL_INT;
case IIO_CHAN_INFO_SCALE:
switch (chan->channel2) {
case IIO_MOD_TEMP_AMBIENT:
/* Cold junction Temp. Data resolution is 0.015625 */
*val = 15;
*val2 = 625000; /* 1000 * 0.015625 */
ret = IIO_VAL_INT_PLUS_MICRO;
break;
default:
/* Thermocouple Temp. Data resolution is 0.0078125 */
*val = 7;
*val2 = 812500; /* 1000 * 0.0078125) */
return IIO_VAL_INT_PLUS_MICRO;
}
break;
case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
*val = 1 << data->averaging;
return IIO_VAL_INT;
case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
*val = max31856_tc_types[data->thermocouple_type];
return IIO_VAL_CHAR;
default:
ret = -EINVAL;
break;
}
return ret;
}
static int max31856_write_raw_get_fmt(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
long mask)
{
switch (mask) {
case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
return IIO_VAL_CHAR;
default:
return IIO_VAL_INT;
}
}
static int max31856_write_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int val, int val2, long mask)
{
struct max31856_data *data = iio_priv(indio_dev);
int msb;
switch (mask) {
case IIO_CHAN_INFO_OVERSAMPLING_RATIO:
if (val > 16 || val < 1)
return -EINVAL;
msb = fls(val) - 1;
/* Round up to next 2pow if needed */
if (BIT(msb) < val)
msb++;
data->averaging = msb;
max31856_init(data);
break;
case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:
{
int tc_type = -1;
int i;
for (i = 0; i < ARRAY_SIZE(max31856_tc_types); i++) {
if (max31856_tc_types[i] == toupper(val)) {
tc_type = i;
break;
}
}
if (tc_type < 0)
return -EINVAL;
data->thermocouple_type = tc_type;
max31856_init(data);
break;
}
default:
return -EINVAL;
}
return 0;
}
static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct max31856_data *data = iio_priv(indio_dev);
u8 reg_val;
int ret;
bool fault;
ret = max31856_read(data, MAX31856_SR_REG, &reg_val, 1);
if (ret)
return ret;
fault = reg_val & faultbit;
return sprintf(buf, "%d\n", fault);
}
static ssize_t show_fault_ovuv(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return show_fault(dev, MAX31856_FAULT_OVUV, buf);
}
static ssize_t show_fault_oc(struct device *dev,
struct device_attribute *attr,
char *buf)
{
return show_fault(dev, MAX31856_FAULT_OPEN, buf);
}
static ssize_t show_filter(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct max31856_data *data = iio_priv(indio_dev);
return sprintf(buf, "%d\n", data->filter_50hz ? 50 : 60);
}
static ssize_t set_filter(struct device *dev,
struct device_attribute *attr,
const char *buf,
size_t len)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct max31856_data *data = iio_priv(indio_dev);
unsigned int freq;
int ret;
ret = kstrtouint(buf, 10, &freq);
if (ret)
return ret;
switch (freq) {
case 50:
data->filter_50hz = true;
break;
case 60:
data->filter_50hz = false;
break;
default:
return -EINVAL;
}
max31856_init(data);
return len;
}
static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);
static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644,
show_filter, set_filter, 0);
static struct attribute *max31856_attributes[] = {
&iio_dev_attr_fault_ovuv.dev_attr.attr,
&iio_dev_attr_fault_oc.dev_attr.attr,
&iio_dev_attr_in_temp_filter_notch_center_frequency.dev_attr.attr,
NULL,
};
static const struct attribute_group max31856_group = {
.attrs = max31856_attributes,
};
static const struct iio_info max31856_info = {
.read_raw = max31856_read_raw,
.write_raw = max31856_write_raw,
.write_raw_get_fmt = max31856_write_raw_get_fmt,
.attrs = &max31856_group,
};
static int max31856_probe(struct spi_device *spi)
{
const struct spi_device_id *id = spi_get_device_id(spi);
struct iio_dev *indio_dev;
struct max31856_data *data;
int ret;
indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
data = iio_priv(indio_dev);
data->spi = spi;
data->filter_50hz = false;
spi_set_drvdata(spi, indio_dev);
indio_dev->info = &max31856_info;
indio_dev->dev.parent = &spi->dev;
indio_dev->dev.of_node = spi->dev.of_node;
indio_dev->name = id->name;
indio_dev->modes = INDIO_DIRECT_MODE;
indio_dev->channels = max31856_channels;
indio_dev->num_channels = ARRAY_SIZE(max31856_channels);
ret = of_property_read_u32(spi->dev.of_node, "thermocouple-type",
&data->thermocouple_type);
if (ret) {
dev_info(&spi->dev,
"Could not read thermocouple type DT property, configuring as a K-Type\n");
data->thermocouple_type = THERMOCOUPLE_TYPE_K;
}
/*
* no need to translate values as the supported types
* have the same value as the #defines
*/
switch (data->thermocouple_type) {
case THERMOCOUPLE_TYPE_B:
case THERMOCOUPLE_TYPE_E:
case THERMOCOUPLE_TYPE_J:
case THERMOCOUPLE_TYPE_K:
case THERMOCOUPLE_TYPE_N:
case THERMOCOUPLE_TYPE_R:
case THERMOCOUPLE_TYPE_S:
case THERMOCOUPLE_TYPE_T:
break;
default:
dev_err(&spi->dev,
"error: thermocouple-type %u not supported by max31856\n"
, data->thermocouple_type);
return -EINVAL;
}
ret = max31856_init(data);
if (ret) {
dev_err(&spi->dev, "error: Failed to configure max31856\n");
return ret;
}
return devm_iio_device_register(&spi->dev, indio_dev);
}
static const struct spi_device_id max31856_id[] = {
{ "max31856", 0 },
{ }
};
MODULE_DEVICE_TABLE(spi, max31856_id);
static const struct of_device_id max31856_of_match[] = {
{ .compatible = "maxim,max31856" },
{ }
};
MODULE_DEVICE_TABLE(of, max31856_of_match);
static struct spi_driver max31856_driver = {
.driver = {
.name = "max31856",
.of_match_table = max31856_of_match,
},
.probe = max31856_probe,
.id_table = max31856_id,
};
module_spi_driver(max31856_driver);
MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>");
MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");
MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver");
MODULE_LICENSE("GPL");
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