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1// SPDX-License-Identifier: GPL-2.02/* max31856.c3 *4 * Maxim MAX31856 thermocouple sensor driver5 *6 * Copyright (C) 2018-2019 Rockwell Collins7 */8 9#include <linux/ctype.h>10#include <linux/mod_devicetable.h>11#include <linux/module.h>12#include <linux/init.h>13#include <linux/err.h>14#include <linux/property.h>15#include <linux/spi/spi.h>16#include <linux/iio/iio.h>17#include <linux/iio/sysfs.h>18#include <linux/util_macros.h>19#include <linux/unaligned.h>20#include <dt-bindings/iio/temperature/thermocouple.h>21/*22 * The MSB of the register value determines whether the following byte will23 * be written or read. If it is 0, one or more byte reads will follow.24 */25#define MAX31856_RD_WR_BIT BIT(7)26 27#define MAX31856_CR0_AUTOCONVERT BIT(7)28#define MAX31856_CR0_1SHOT BIT(6)29#define MAX31856_CR0_OCFAULT BIT(4)30#define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4)31#define MAX31856_CR0_FILTER_50HZ BIT(0)32#define MAX31856_AVERAGING_MASK GENMASK(6, 4)33#define MAX31856_AVERAGING_SHIFT 434#define MAX31856_TC_TYPE_MASK GENMASK(3, 0)35#define MAX31856_FAULT_OVUV BIT(1)36#define MAX31856_FAULT_OPEN BIT(0)37 38/* The MAX31856 registers */39#define MAX31856_CR0_REG 0x0040#define MAX31856_CR1_REG 0x0141#define MAX31856_MASK_REG 0x0242#define MAX31856_CJHF_REG 0x0343#define MAX31856_CJLF_REG 0x0444#define MAX31856_LTHFTH_REG 0x0545#define MAX31856_LTHFTL_REG 0x0646#define MAX31856_LTLFTH_REG 0x0747#define MAX31856_LTLFTL_REG 0x0848#define MAX31856_CJTO_REG 0x0949#define MAX31856_CJTH_REG 0x0A50#define MAX31856_CJTL_REG 0x0B51#define MAX31856_LTCBH_REG 0x0C52#define MAX31856_LTCBM_REG 0x0D53#define MAX31856_LTCBL_REG 0x0E54#define MAX31856_SR_REG 0x0F55 56static const struct iio_chan_spec max31856_channels[] = {57 { /* Thermocouple Temperature */58 .type = IIO_TEMP,59 .info_mask_separate =60 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) |61 BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE),62 .info_mask_shared_by_type =63 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)64 },65 { /* Cold Junction Temperature */66 .type = IIO_TEMP,67 .channel2 = IIO_MOD_TEMP_AMBIENT,68 .modified = 1,69 .info_mask_separate =70 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),71 .info_mask_shared_by_type =72 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO)73 },74};75 76struct max31856_data {77 struct spi_device *spi;78 u32 thermocouple_type;79 bool filter_50hz;80 int averaging;81};82 83static const char max31856_tc_types[] = {84 'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T'85};86 87static int max31856_read(struct max31856_data *data, u8 reg,88 u8 val[], unsigned int read_size)89{90 return spi_write_then_read(data->spi, ®, 1, val, read_size);91}92 93static int max31856_write(struct max31856_data *data, u8 reg,94 unsigned int val)95{96 u8 buf[2];97 98 buf[0] = reg | (MAX31856_RD_WR_BIT);99 buf[1] = val;100 101 return spi_write(data->spi, buf, 2);102}103 104static int max31856_init(struct max31856_data *data)105{106 int ret;107 u8 reg_cr0_val, reg_cr1_val;108 109 /* Start by changing to Off mode before making changes as110 * some settings are recommended to be set only when the device111 * is off112 */113 ret = max31856_read(data, MAX31856_CR0_REG, ®_cr0_val, 1);114 if (ret)115 return ret;116 117 reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT;118 ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);119 if (ret)120 return ret;121 122 /* Set thermocouple type based on dts property */123 ret = max31856_read(data, MAX31856_CR1_REG, ®_cr1_val, 1);124 if (ret)125 return ret;126 127 reg_cr1_val &= ~MAX31856_TC_TYPE_MASK;128 reg_cr1_val |= data->thermocouple_type;129 130 reg_cr1_val &= ~MAX31856_AVERAGING_MASK;131 reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT;132 133 ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val);134 if (ret)135 return ret;136 137 /*138 * Enable Open circuit fault detection139 * Read datasheet for more information: Table 4.140 * Value 01 means : Enabled (Once every 16 conversions)141 */142 reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK;143 reg_cr0_val |= MAX31856_CR0_OCFAULT;144 145 /* Set Auto Conversion Mode */146 reg_cr0_val &= ~MAX31856_CR0_1SHOT;147 reg_cr0_val |= MAX31856_CR0_AUTOCONVERT;148 149 if (data->filter_50hz)150 reg_cr0_val |= MAX31856_CR0_FILTER_50HZ;151 else152 reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ;153 154 return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val);155}156 157static int max31856_thermocouple_read(struct max31856_data *data,158 struct iio_chan_spec const *chan,159 int *val)160{161 int ret, offset_cjto;162 u8 reg_val[3];163 164 switch (chan->channel2) {165 case IIO_NO_MOD:166 /*167 * Multibyte Read168 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG169 */170 ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3);171 if (ret)172 return ret;173 /* Skip last 5 dead bits of LTCBL */174 *val = get_unaligned_be24(®_val[0]) >> 5;175 /* Check 7th bit of LTCBH reg. value for sign*/176 if (reg_val[0] & 0x80)177 *val -= 0x80000;178 break;179 180 case IIO_MOD_TEMP_AMBIENT:181 /*182 * Multibyte Read183 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG184 */185 ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3);186 if (ret)187 return ret;188 /* Get Cold Junction Temp. offset register value */189 offset_cjto = reg_val[0];190 /* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */191 *val = get_unaligned_be16(®_val[1]) >> 2;192 /* As per datasheet add offset into CJTH and CJTL */193 *val += offset_cjto;194 /* Check 7th bit of CJTH reg. value for sign */195 if (reg_val[1] & 0x80)196 *val -= 0x4000;197 break;198 199 default:200 return -EINVAL;201 }202 203 ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1);204 if (ret)205 return ret;206 /* Check for over/under voltage or open circuit fault */207 if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN))208 return -EIO;209 210 return ret;211}212 213static int max31856_read_raw(struct iio_dev *indio_dev,214 struct iio_chan_spec const *chan,215 int *val, int *val2, long mask)216{217 struct max31856_data *data = iio_priv(indio_dev);218 int ret;219 220 switch (mask) {221 case IIO_CHAN_INFO_RAW:222 ret = max31856_thermocouple_read(data, chan, val);223 if (ret)224 return ret;225 return IIO_VAL_INT;226 case IIO_CHAN_INFO_SCALE:227 switch (chan->channel2) {228 case IIO_MOD_TEMP_AMBIENT:229 /* Cold junction Temp. Data resolution is 0.015625 */230 *val = 15;231 *val2 = 625000; /* 1000 * 0.015625 */232 ret = IIO_VAL_INT_PLUS_MICRO;233 break;234 default:235 /* Thermocouple Temp. Data resolution is 0.0078125 */236 *val = 7;237 *val2 = 812500; /* 1000 * 0.0078125) */238 return IIO_VAL_INT_PLUS_MICRO;239 }240 break;241 case IIO_CHAN_INFO_OVERSAMPLING_RATIO:242 *val = 1 << data->averaging;243 return IIO_VAL_INT;244 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:245 *val = max31856_tc_types[data->thermocouple_type];246 return IIO_VAL_CHAR;247 default:248 ret = -EINVAL;249 break;250 }251 252 return ret;253}254 255static int max31856_write_raw_get_fmt(struct iio_dev *indio_dev,256 struct iio_chan_spec const *chan,257 long mask)258{259 switch (mask) {260 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:261 return IIO_VAL_CHAR;262 default:263 return IIO_VAL_INT;264 }265}266 267static int max31856_write_raw(struct iio_dev *indio_dev,268 struct iio_chan_spec const *chan,269 int val, int val2, long mask)270{271 struct max31856_data *data = iio_priv(indio_dev);272 int msb;273 274 switch (mask) {275 case IIO_CHAN_INFO_OVERSAMPLING_RATIO:276 if (val > 16 || val < 1)277 return -EINVAL;278 msb = fls(val) - 1;279 /* Round up to next 2pow if needed */280 if (BIT(msb) < val)281 msb++;282 283 data->averaging = msb;284 max31856_init(data);285 break;286 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE:287 {288 int tc_type = -1;289 int i;290 291 for (i = 0; i < ARRAY_SIZE(max31856_tc_types); i++) {292 if (max31856_tc_types[i] == toupper(val)) {293 tc_type = i;294 break;295 }296 }297 if (tc_type < 0)298 return -EINVAL;299 300 data->thermocouple_type = tc_type;301 max31856_init(data);302 break;303 }304 default:305 return -EINVAL;306 }307 308 return 0;309}310 311static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf)312{313 struct iio_dev *indio_dev = dev_to_iio_dev(dev);314 struct max31856_data *data = iio_priv(indio_dev);315 u8 reg_val;316 int ret;317 bool fault;318 319 ret = max31856_read(data, MAX31856_SR_REG, ®_val, 1);320 if (ret)321 return ret;322 323 fault = reg_val & faultbit;324 325 return sysfs_emit(buf, "%d\n", fault);326}327 328static ssize_t show_fault_ovuv(struct device *dev,329 struct device_attribute *attr,330 char *buf)331{332 return show_fault(dev, MAX31856_FAULT_OVUV, buf);333}334 335static ssize_t show_fault_oc(struct device *dev,336 struct device_attribute *attr,337 char *buf)338{339 return show_fault(dev, MAX31856_FAULT_OPEN, buf);340}341 342static ssize_t show_filter(struct device *dev,343 struct device_attribute *attr,344 char *buf)345{346 struct iio_dev *indio_dev = dev_to_iio_dev(dev);347 struct max31856_data *data = iio_priv(indio_dev);348 349 return sysfs_emit(buf, "%d\n", data->filter_50hz ? 50 : 60);350}351 352static ssize_t set_filter(struct device *dev,353 struct device_attribute *attr,354 const char *buf,355 size_t len)356{357 struct iio_dev *indio_dev = dev_to_iio_dev(dev);358 struct max31856_data *data = iio_priv(indio_dev);359 unsigned int freq;360 int ret;361 362 ret = kstrtouint(buf, 10, &freq);363 if (ret)364 return ret;365 366 switch (freq) {367 case 50:368 data->filter_50hz = true;369 break;370 case 60:371 data->filter_50hz = false;372 break;373 default:374 return -EINVAL;375 }376 377 max31856_init(data);378 return len;379}380 381static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0);382static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0);383static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644,384 show_filter, set_filter, 0);385 386static struct attribute *max31856_attributes[] = {387 &iio_dev_attr_fault_ovuv.dev_attr.attr,388 &iio_dev_attr_fault_oc.dev_attr.attr,389 &iio_dev_attr_in_temp_filter_notch_center_frequency.dev_attr.attr,390 NULL,391};392 393static const struct attribute_group max31856_group = {394 .attrs = max31856_attributes,395};396 397static const struct iio_info max31856_info = {398 .read_raw = max31856_read_raw,399 .write_raw = max31856_write_raw,400 .write_raw_get_fmt = max31856_write_raw_get_fmt,401 .attrs = &max31856_group,402};403 404static int max31856_probe(struct spi_device *spi)405{406 const struct spi_device_id *id = spi_get_device_id(spi);407 struct iio_dev *indio_dev;408 struct max31856_data *data;409 int ret;410 411 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data));412 if (!indio_dev)413 return -ENOMEM;414 415 data = iio_priv(indio_dev);416 data->spi = spi;417 data->filter_50hz = false;418 419 spi_set_drvdata(spi, indio_dev);420 421 indio_dev->info = &max31856_info;422 indio_dev->name = id->name;423 indio_dev->modes = INDIO_DIRECT_MODE;424 indio_dev->channels = max31856_channels;425 indio_dev->num_channels = ARRAY_SIZE(max31856_channels);426 427 ret = device_property_read_u32(&spi->dev, "thermocouple-type", &data->thermocouple_type);428 if (ret) {429 dev_info(&spi->dev,430 "Could not read thermocouple type DT property, configuring as a K-Type\n");431 data->thermocouple_type = THERMOCOUPLE_TYPE_K;432 }433 434 /*435 * no need to translate values as the supported types436 * have the same value as the #defines437 */438 switch (data->thermocouple_type) {439 case THERMOCOUPLE_TYPE_B:440 case THERMOCOUPLE_TYPE_E:441 case THERMOCOUPLE_TYPE_J:442 case THERMOCOUPLE_TYPE_K:443 case THERMOCOUPLE_TYPE_N:444 case THERMOCOUPLE_TYPE_R:445 case THERMOCOUPLE_TYPE_S:446 case THERMOCOUPLE_TYPE_T:447 break;448 default:449 dev_err(&spi->dev,450 "error: thermocouple-type %u not supported by max31856\n"451 , data->thermocouple_type);452 return -EINVAL;453 }454 455 ret = max31856_init(data);456 if (ret) {457 dev_err(&spi->dev, "error: Failed to configure max31856\n");458 return ret;459 }460 461 return devm_iio_device_register(&spi->dev, indio_dev);462}463 464static const struct spi_device_id max31856_id[] = {465 { "max31856", 0 },466 { }467};468MODULE_DEVICE_TABLE(spi, max31856_id);469 470static const struct of_device_id max31856_of_match[] = {471 { .compatible = "maxim,max31856" },472 { }473};474MODULE_DEVICE_TABLE(of, max31856_of_match);475 476static struct spi_driver max31856_driver = {477 .driver = {478 .name = "max31856",479 .of_match_table = max31856_of_match,480 },481 .probe = max31856_probe,482 .id_table = max31856_id,483};484module_spi_driver(max31856_driver);485 486MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>");487MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>");488MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver");489MODULE_LICENSE("GPL");490