| Message ID | 20190226150214.19467-2-patrick.havelange@essensium.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v5,1/2] iio:temperature:max31856:Add device tree bind info | expand |
On Tue, 26 Feb 2019 16:02:14 +0100 Patrick Havelange <patrick.havelange@essensium.com> wrote: > From: Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com> > > This patch adds support for Maxim MAX31856 thermocouple > temperature sensor support. > > More information can be found in: > https://www.maximintegrated.com/en/ds/MAX31856.pdf > > NOTE: Driver support only Comparator Mode. > > Signed-off-by: Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com> > Signed-off-by: Matt Weber <matthew.weber@rockwellcollins.com> > Signed-off-by: Patrick Havelange <patrick.havelange@essensium.com> One totally trivial comment inline. I wish we had a more general error reporting mechanism, but until that comes about (it's debated every few years but I haven't heard anything recently) the sysfs ABI will have to do. Anyhow, just holding this to let us sort out the DT binding for the thermocouple probe type. Thanks, Jonathan > --- > Changes > v1 -> v2 > [Peter > 1. Fixed all space & 'return' related comments > 2. Removed 'sysfs_create_group' api because > iio_device_register function is handling sysfs entry > 3. Return -EIO if there is any fault > 4. Added check for 'read_size' before spi read call > 5. Removed license text from the source file > 6. Added .o file in alphabetic order > 7. Used #defines instead of magic bits > > v2 -> v3 > [Jonathan > 1. Used bool for fault_oc and fault_ovuv > 2. Changed 'max31856_read' function and use byte array to > store registers value. > 3. Used 'GENMASK' where required > 4. Changed logic 'max31856_thermocouple_read' function. Used > array to read registers value. > 5. Used 'devm_iio_device_register' and removed 'max31856_remove'. > 6. Fixed other cosmetic changes. > 7. Added 'sysfs-bus-iio-temperature-max31856' file and updated > 'MAINTAINERS' file. > > v3 -> v4 > [Jonathan > 1. Removed unwanted logic > 2. Updated code to handle return value of max31856_read call > 3. Added devicetree id table > 4. Removed one-shot support from driver as this support was not > implemented with correct design. > > v4 -> v5 > [Patrick > 1. Rename thermocouple type to maxim,thermocouple-type for DT entry > 2. Don't cache values from the Fault Status Register > 3. Simplify a bit max31856_init() > 4. Use IIO_NO_MOD in switch case + default error case > 5. Use dev_*() instead of pr_*() > 6. Fix missing space in comments > 7. Removed iio_info.driver_module assignment as no longer present > 8. Don't keep read/write buffer into the internal driver struct > 9. Updated kernel version, add missing space in documentation > 10. Updated (c) year > 11. Removed linux/init.h #include > 12. More use of BIT() macro > 13. Removed iio_chan_spec.address assignment as not used > 14. In max31856_thermocouple_read(), same switch case order as > channels definition > 15. Refactor show_fault_*() functions > 16. Use u8 as register type in max31856_{read,write}() > --- > .../sysfs-bus-iio-temperature-max31856 | 23 ++ > drivers/iio/temperature/Kconfig | 10 + > drivers/iio/temperature/Makefile | 1 + > drivers/iio/temperature/max31856.c | 332 ++++++++++++++++++ > 4 files changed, 366 insertions(+) > create mode 100644 Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 > create mode 100644 drivers/iio/temperature/max31856.c > > diff --git a/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 b/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 > new file mode 100644 > index 000000000000..22659c91262c > --- /dev/null > +++ b/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 > @@ -0,0 +1,23 @@ > +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 (default). It's not really the default. It's the good state. > diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig > index 82e4a62745e2..c66eeb23615b 100644 > --- a/drivers/iio/temperature/Kconfig > +++ b/drivers/iio/temperature/Kconfig > @@ -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 > diff --git a/drivers/iio/temperature/Makefile b/drivers/iio/temperature/Makefile > index 34a31db0bb63..baca4776ca0d 100644 > --- a/drivers/iio/temperature/Makefile > +++ b/drivers/iio/temperature/Makefile > @@ -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 > diff --git a/drivers/iio/temperature/max31856.c b/drivers/iio/temperature/max31856.c > new file mode 100644 > index 000000000000..d0e206ff10ba > --- /dev/null > +++ b/drivers/iio/temperature/max31856.c > @@ -0,0 +1,332 @@ > +// 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> > + > +/* > + * 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, ®, 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, ®_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, ®_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, ®_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, "maxim,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 = 0x03; /* K-Type */ > + } > + > + 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");
diff --git a/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 b/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 new file mode 100644 index 000000000000..22659c91262c --- /dev/null +++ b/Documentation/ABI/testing/sysfs-bus-iio-temperature-max31856 @@ -0,0 +1,23 @@ +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 (default). diff --git a/drivers/iio/temperature/Kconfig b/drivers/iio/temperature/Kconfig index 82e4a62745e2..c66eeb23615b 100644 --- a/drivers/iio/temperature/Kconfig +++ b/drivers/iio/temperature/Kconfig @@ -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 diff --git a/drivers/iio/temperature/Makefile b/drivers/iio/temperature/Makefile index 34a31db0bb63..baca4776ca0d 100644 --- a/drivers/iio/temperature/Makefile +++ b/drivers/iio/temperature/Makefile @@ -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 diff --git a/drivers/iio/temperature/max31856.c b/drivers/iio/temperature/max31856.c new file mode 100644 index 000000000000..d0e206ff10ba --- /dev/null +++ b/drivers/iio/temperature/max31856.c @@ -0,0 +1,332 @@ +// 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> + +/* + * 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, ®, 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, ®_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, ®_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, ®_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, "maxim,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 = 0x03; /* K-Type */ + } + + 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");