// SPDX-License-Identifier: GPL-2.0 /* max31856.c * * Maxim MAX31856 thermocouple sensor driver * * Copyright (C) 2018-2019 Rockwell Collins */ #include #include #include #include #include #include #include /* * 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 "); MODULE_AUTHOR("Patrick Havelange "); MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver"); MODULE_LICENSE("GPL");