| // 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, ®, 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; |
| default: |
| ret = -EINVAL; |
| 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, "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"); |