iio:temperature: Add MAX31856 thermocouple support (fb55a513) · Commits · 戴 / test

Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856

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		What: /sys/bus/iio/devices/iio:deviceX/fault_oc
		KernelVersion: 5.1
		Contact: linux-iio@vger.kernel.org
		Description:
		Open-circuit fault. The detection of open-circuit faults,
		such as those caused by broken thermocouple wires.
		Reading returns either '1' or '0'.
		'1' = An open circuit such as broken thermocouple wires
		has been detected.
		'0' = No open circuit or broken thermocouple wires are detected

		What: /sys/bus/iio/devices/iio:deviceX/fault_ovuv
		KernelVersion: 5.1
		Contact: linux-iio@vger.kernel.org
		Description:
		Overvoltage or Undervoltage Input Fault. The internal circuitry
		is protected from excessive voltages applied to the thermocouple
		cables by integrated MOSFETs at the T+ and T- inputs, and the
		BIAS output. These MOSFETs turn off when the input voltage is
		negative or greater than VDD.
		Reading returns either '1' or '0'.
		'1' = The input voltage is negative or greater than VDD.
		'0' = The input voltage is positive and less than VDD (normal
		state).

drivers/iio/temperature/Kconfig

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		@@ -97,4 +97,14 @@ config TSYS02D
		This driver can also be built as a module. If so, the module will
		be called tsys02d.

		config MAX31856
		tristate "MAX31856 thermocouple sensor"
		depends on SPI
		help
		If you say yes here you get support for MAX31856
		thermocouple sensor chip connected via SPI.

		This driver can also be built as a module. If so, the module
		will be called max31856.

		endmenu

drivers/iio/temperature/Makefile

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		@@ -5,6 +5,7 @@

		obj-$(CONFIG_HID_SENSOR_TEMP) += hid-sensor-temperature.o
		obj-$(CONFIG_MAXIM_THERMOCOUPLE) += maxim_thermocouple.o
		obj-$(CONFIG_MAX31856) += max31856.o
		obj-$(CONFIG_MLX90614) += mlx90614.o
		obj-$(CONFIG_MLX90632) += mlx90632.o
		obj-$(CONFIG_TMP006) += tmp006.o

drivers/iio/temperature/max31856.c

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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/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 <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_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),
		},
		{ /* 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),
		},
		};

		struct max31856_data {
		struct spi_device *spi;
		u32 thermocouple_type;
		};

		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;
		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;

		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;
		}

		return ret;
		}

		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 IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);
		static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);

		static struct attribute *max31856_attributes[] = {
		&iio_dev_attr_fault_ovuv.dev_attr.attr,
		&iio_dev_attr_fault_oc.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,
		.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;

		spi_set_drvdata(spi, indio_dev);

		indio_dev->info = &max31856_info;
		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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