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iio: temperature: add support for Maxim thermocouple chips 

Add initial driver support for MAX6675, and MAX31855 thermocouple chips.

Cc: Marek Vasut <marex@denx.de>
Cc: Matt Porter <mporter@konsulko.com>
Signed-off-by: Matt Ranostay <mranostay@gmail.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>
This commit is contained in:
Matt Ranostay 2016-07-04 18:54:04 -07:00 committed by Jonathan Cameron
parent 0ddfd85713
commit 1f25ca11d8
4 changed files with 317 additions and 0 deletions
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21
Documentation/devicetree/bindings/iio/temperature/maxim_thermocouple.txt Normal file
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Maxim thermocouple support
* https://datasheets.maximintegrated.com/en/ds/MAX6675.pdf
* https://datasheets.maximintegrated.com/en/ds/MAX31855.pdf
Required properties:
- compatible: must be "maxim,max31855" or "maxim,max6675"
- reg: SPI chip select number for the device
- spi-max-frequency: must be 4300000
- spi-cpha: must be defined for max6675 to enable SPI mode 1
Refer to spi/spi-bus.txt for generic SPI slave bindings.
Example:
max31855@0 {
compatible = "maxim,max31855";
reg = <0>;
spi-max-frequency = <4300000>;
};

14
drivers/iio/temperature/Kconfig
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@ -3,6 +3,20 @@
#
menu "Temperature sensors"
config MAXIM_THERMOCOUPLE
tristate "Maxim thermocouple sensors"
depends on SPI
help
If you say yes here you get support for the Maxim series of
thermocouple sensors connected via SPI.
Supported sensors:
* MAX6675
* MAX31855
This driver can also be built as a module. If so, the module will
be called maxim_thermocouple.
config MLX90614
tristate "MLX90614 contact-less infrared sensor"
depends on I2C

1
drivers/iio/temperature/Makefile
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@ -2,6 +2,7 @@
# Makefile for industrial I/O temperature drivers
#
obj-$(CONFIG_MAXIM_THERMOCOUPLE) += maxim_thermocouple.o
obj-$(CONFIG_MLX90614) += mlx90614.o
obj-$(CONFIG_TMP006) += tmp006.o
obj-$(CONFIG_TSYS01) += tsys01.o

281
drivers/iio/temperature/maxim_thermocouple.c Normal file
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/*
* maxim_thermocouple.c - Support for Maxim thermocouple chips
*
* Copyright (C) 2016 Matt Ranostay <mranostay@gmail.com>
*
* 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.
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/mutex.h>
#include <linux/err.h>
#include <linux/spi/spi.h>
#include <linux/iio/iio.h>
#include <linux/iio/trigger.h>
#include <linux/iio/buffer.h>
#include <linux/iio/triggered_buffer.h>
#include <linux/iio/trigger_consumer.h>
#define MAXIM_THERMOCOUPLE_DRV_NAME "maxim_thermocouple"
enum {
MAX6675,
MAX31855,
};
const struct iio_chan_spec max6675_channels[] = {
{ /* thermocouple temperature */
.type = IIO_TEMP,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
.scan_index = 0,
.scan_type = {
.sign = 's',
.realbits = 13,
.storagebits = 16,
.shift = 3,
.endianness = IIO_BE,
},
},
IIO_CHAN_SOFT_TIMESTAMP(1),
};
const struct iio_chan_spec max31855_channels[] = {
{ /* thermocouple temperature */
.type = IIO_TEMP,
.address = 2,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
.scan_index = 0,
.scan_type = {
.sign = 's',
.realbits = 14,
.storagebits = 16,
.shift = 2,
.endianness = IIO_BE,
},
},
{ /* cold junction temperature */
.type = IIO_TEMP,
.address = 0,
.channel2 = IIO_MOD_TEMP_AMBIENT,
.modified = 1,
.info_mask_separate =
BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
.scan_index = 1,
.scan_type = {
.sign = 's',
.realbits = 12,
.storagebits = 16,
.shift = 4,
.endianness = IIO_BE,
},
},
IIO_CHAN_SOFT_TIMESTAMP(2),
};
static const unsigned long max31855_scan_masks[] = {0x3, 0};
struct maxim_thermocouple_chip {
const struct iio_chan_spec *channels;
const unsigned long *scan_masks;
u8 num_channels;
u8 read_size;
/* bit-check for valid input */
u32 status_bit;
};
const struct maxim_thermocouple_chip maxim_thermocouple_chips[] = {
[MAX6675] = {
.channels = max6675_channels,
.num_channels = ARRAY_SIZE(max6675_channels),
.read_size = 2,
.status_bit = BIT(2),
},
[MAX31855] = {
.channels = max31855_channels,
.num_channels = ARRAY_SIZE(max31855_channels),
.read_size = 4,
.scan_masks = max31855_scan_masks,
.status_bit = BIT(16),
},
};
struct maxim_thermocouple_data {
struct spi_device *spi;
const struct maxim_thermocouple_chip *chip;
u8 buffer[16] ____cacheline_aligned;
};
static int maxim_thermocouple_read(struct maxim_thermocouple_data *data,
struct iio_chan_spec const *chan, int *val)
{
unsigned int storage_bytes = data->chip->read_size;
unsigned int shift = chan->scan_type.shift + (chan->address * 8);
unsigned int buf;
int ret;
ret = spi_read(data->spi, (void *) &buf, storage_bytes);
if (ret)
return ret;
switch (storage_bytes) {
case 2:
*val = be16_to_cpu(buf);
break;
case 4:
*val = be32_to_cpu(buf);
break;
}
/* check to be sure this is a valid reading */
if (*val & data->chip->status_bit)
return -EINVAL;
*val = sign_extend32(*val >> shift, chan->scan_type.realbits - 1);
return 0;
}
static irqreturn_t maxim_thermocouple_trigger_handler(int irq, void *private)
{
struct iio_poll_func *pf = private;
struct iio_dev *indio_dev = pf->indio_dev;
struct maxim_thermocouple_data *data = iio_priv(indio_dev);
int ret;
ret = spi_read(data->spi, data->buffer, data->chip->read_size);
if (!ret) {
iio_push_to_buffers_with_timestamp(indio_dev, data->buffer,
iio_get_time_ns(indio_dev));
}
iio_trigger_notify_done(indio_dev->trig);
return IRQ_HANDLED;
}
static int maxim_thermocouple_read_raw(struct iio_dev *indio_dev,
struct iio_chan_spec const *chan,
int *val, int *val2, long mask)
{
struct maxim_thermocouple_data *data = iio_priv(indio_dev);
int ret = -EINVAL;
switch (mask) {
case IIO_CHAN_INFO_RAW:
ret = iio_device_claim_direct_mode(indio_dev);
if (ret)
return ret;
ret = maxim_thermocouple_read(data, chan, val);
iio_device_release_direct_mode(indio_dev);
if (!ret)
return IIO_VAL_INT;
break;
case IIO_CHAN_INFO_SCALE:
switch (chan->channel2) {
case IIO_MOD_TEMP_AMBIENT:
*val = 62;
*val2 = 500000; /* 1000 * 0.0625 */
ret = IIO_VAL_INT_PLUS_MICRO;
break;
default:
*val = 250; /* 1000 * 0.25 */
ret = IIO_VAL_INT;
};
break;
}
return ret;
}
static const struct iio_info maxim_thermocouple_info = {
.driver_module = THIS_MODULE,
.read_raw = maxim_thermocouple_read_raw,
};
static int maxim_thermocouple_probe(struct spi_device *spi)
{
const struct spi_device_id *id = spi_get_device_id(spi);
struct iio_dev *indio_dev;
struct maxim_thermocouple_data *data;
const struct maxim_thermocouple_chip *chip =
&maxim_thermocouple_chips[id->driver_data];
int ret;
indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));
if (!indio_dev)
return -ENOMEM;
indio_dev->info = &maxim_thermocouple_info;
indio_dev->name = MAXIM_THERMOCOUPLE_DRV_NAME;
indio_dev->channels = chip->channels;
indio_dev->available_scan_masks = chip->scan_masks;
indio_dev->num_channels = chip->num_channels;
indio_dev->modes = INDIO_DIRECT_MODE;
data = iio_priv(indio_dev);
data->spi = spi;
data->chip = chip;
ret = iio_triggered_buffer_setup(indio_dev, NULL,
maxim_thermocouple_trigger_handler, NULL);
if (ret)
return ret;
ret = iio_device_register(indio_dev);
if (ret)
goto error_unreg_buffer;
return 0;
error_unreg_buffer:
iio_triggered_buffer_cleanup(indio_dev);
return ret;
}
static int maxim_thermocouple_remove(struct spi_device *spi)
{
struct iio_dev *indio_dev = spi_get_drvdata(spi);
iio_device_unregister(indio_dev);
iio_triggered_buffer_cleanup(indio_dev);
return 0;
}
static const struct spi_device_id maxim_thermocouple_id[] = {
{"max6675", MAX6675},
{"max31855", MAX31855},
{},
};
MODULE_DEVICE_TABLE(spi, maxim_thermocouple_id);
static struct spi_driver maxim_thermocouple_driver = {
.driver = {
.name = MAXIM_THERMOCOUPLE_DRV_NAME,
},
.probe = maxim_thermocouple_probe,
.remove = maxim_thermocouple_remove,
.id_table = maxim_thermocouple_id,
};
module_spi_driver(maxim_thermocouple_driver);
MODULE_AUTHOR("Matt Ranostay <mranostay@gmail.com>");
MODULE_DESCRIPTION("Maxim thermocouple sensors");
MODULE_LICENSE("GPL");