1 // SPDX-License-Identifier: GPL-2.0 2 /* max31856.c 3 * 4 * Maxim MAX31856 thermocouple sensor driver 5 * 6 * Copyright (C) 2018-2019 Rockwell Collins 7 */ 8 9 #include <linux/module.h> 10 #include <linux/init.h> 11 #include <linux/err.h> 12 #include <linux/spi/spi.h> 13 #include <linux/iio/iio.h> 14 #include <linux/iio/sysfs.h> 15 #include <linux/util_macros.h> 16 #include <dt-bindings/iio/temperature/thermocouple.h> 17 /* 18 * The MSB of the register value determines whether the following byte will 19 * be written or read. If it is 0, one or more byte reads will follow. 20 */ 21 #define MAX31856_RD_WR_BIT BIT(7) 22 23 #define MAX31856_CR0_AUTOCONVERT BIT(7) 24 #define MAX31856_CR0_1SHOT BIT(6) 25 #define MAX31856_CR0_OCFAULT BIT(4) 26 #define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4) 27 #define MAX31856_CR0_FILTER_50HZ BIT(0) 28 #define MAX31856_AVERAGING_MASK GENMASK(6, 4) 29 #define MAX31856_AVERAGING_SHIFT 4 30 #define MAX31856_TC_TYPE_MASK GENMASK(3, 0) 31 #define MAX31856_FAULT_OVUV BIT(1) 32 #define MAX31856_FAULT_OPEN BIT(0) 33 34 /* The MAX31856 registers */ 35 #define MAX31856_CR0_REG 0x00 36 #define MAX31856_CR1_REG 0x01 37 #define MAX31856_MASK_REG 0x02 38 #define MAX31856_CJHF_REG 0x03 39 #define MAX31856_CJLF_REG 0x04 40 #define MAX31856_LTHFTH_REG 0x05 41 #define MAX31856_LTHFTL_REG 0x06 42 #define MAX31856_LTLFTH_REG 0x07 43 #define MAX31856_LTLFTL_REG 0x08 44 #define MAX31856_CJTO_REG 0x09 45 #define MAX31856_CJTH_REG 0x0A 46 #define MAX31856_CJTL_REG 0x0B 47 #define MAX31856_LTCBH_REG 0x0C 48 #define MAX31856_LTCBM_REG 0x0D 49 #define MAX31856_LTCBL_REG 0x0E 50 #define MAX31856_SR_REG 0x0F 51 52 static const struct iio_chan_spec max31856_channels[] = { 53 { /* Thermocouple Temperature */ 54 .type = IIO_TEMP, 55 .info_mask_separate = 56 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE), 57 .info_mask_shared_by_type = 58 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) 59 }, 60 { /* Cold Junction Temperature */ 61 .type = IIO_TEMP, 62 .channel2 = IIO_MOD_TEMP_AMBIENT, 63 .modified = 1, 64 .info_mask_separate = 65 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE), 66 .info_mask_shared_by_type = 67 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) 68 }, 69 }; 70 71 struct max31856_data { 72 struct spi_device *spi; 73 u32 thermocouple_type; 74 bool filter_50hz; 75 int averaging; 76 }; 77 78 static int max31856_read(struct max31856_data *data, u8 reg, 79 u8 val[], unsigned int read_size) 80 { 81 return spi_write_then_read(data->spi, ®, 1, val, read_size); 82 } 83 84 static int max31856_write(struct max31856_data *data, u8 reg, 85 unsigned int val) 86 { 87 u8 buf[2]; 88 89 buf[0] = reg | (MAX31856_RD_WR_BIT); 90 buf[1] = val; 91 92 return spi_write(data->spi, buf, 2); 93 } 94 95 static int max31856_init(struct max31856_data *data) 96 { 97 int ret; 98 u8 reg_cr0_val, reg_cr1_val; 99 100 /* Start by changing to Off mode before making changes as 101 * some settings are recommended to be set only when the device 102 * is off 103 */ 104 ret = max31856_read(data, MAX31856_CR0_REG, ®_cr0_val, 1); 105 if (ret) 106 return ret; 107 108 reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT; 109 ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val); 110 if (ret) 111 return ret; 112 113 /* Set thermocouple type based on dts property */ 114 ret = max31856_read(data, MAX31856_CR1_REG, ®_cr1_val, 1); 115 if (ret) 116 return ret; 117 118 reg_cr1_val &= ~MAX31856_TC_TYPE_MASK; 119 reg_cr1_val |= data->thermocouple_type; 120 121 reg_cr1_val &= ~MAX31856_AVERAGING_MASK; 122 reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT; 123 124 ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val); 125 if (ret) 126 return ret; 127 128 /* 129 * Enable Open circuit fault detection 130 * Read datasheet for more information: Table 4. 131 * Value 01 means : Enabled (Once every 16 conversions) 132 */ 133 reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK; 134 reg_cr0_val |= MAX31856_CR0_OCFAULT; 135 136 /* Set Auto Conversion Mode */ 137 reg_cr0_val &= ~MAX31856_CR0_1SHOT; 138 reg_cr0_val |= MAX31856_CR0_AUTOCONVERT; 139 140 if (data->filter_50hz) 141 reg_cr0_val |= MAX31856_CR0_FILTER_50HZ; 142 else 143 reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ; 144 145 return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val); 146 } 147 148 static int max31856_thermocouple_read(struct max31856_data *data, 149 struct iio_chan_spec const *chan, 150 int *val) 151 { 152 int ret, offset_cjto; 153 u8 reg_val[3]; 154 155 switch (chan->channel2) { 156 case IIO_NO_MOD: 157 /* 158 * Multibyte Read 159 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG 160 */ 161 ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3); 162 if (ret) 163 return ret; 164 /* Skip last 5 dead bits of LTCBL */ 165 *val = (reg_val[0] << 16 | reg_val[1] << 8 | reg_val[2]) >> 5; 166 /* Check 7th bit of LTCBH reg. value for sign*/ 167 if (reg_val[0] & 0x80) 168 *val -= 0x80000; 169 break; 170 171 case IIO_MOD_TEMP_AMBIENT: 172 /* 173 * Multibyte Read 174 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG 175 */ 176 ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3); 177 if (ret) 178 return ret; 179 /* Get Cold Junction Temp. offset register value */ 180 offset_cjto = reg_val[0]; 181 /* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */ 182 *val = (reg_val[1] << 8 | reg_val[2]) >> 2; 183 /* As per datasheet add offset into CJTH and CJTL */ 184 *val += offset_cjto; 185 /* Check 7th bit of CJTH reg. value for sign */ 186 if (reg_val[1] & 0x80) 187 *val -= 0x4000; 188 break; 189 190 default: 191 return -EINVAL; 192 } 193 194 ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1); 195 if (ret) 196 return ret; 197 /* Check for over/under voltage or open circuit fault */ 198 if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN)) 199 return -EIO; 200 201 return ret; 202 } 203 204 static int max31856_read_raw(struct iio_dev *indio_dev, 205 struct iio_chan_spec const *chan, 206 int *val, int *val2, long mask) 207 { 208 struct max31856_data *data = iio_priv(indio_dev); 209 int ret; 210 211 switch (mask) { 212 case IIO_CHAN_INFO_RAW: 213 ret = max31856_thermocouple_read(data, chan, val); 214 if (ret) 215 return ret; 216 return IIO_VAL_INT; 217 case IIO_CHAN_INFO_SCALE: 218 switch (chan->channel2) { 219 case IIO_MOD_TEMP_AMBIENT: 220 /* Cold junction Temp. Data resolution is 0.015625 */ 221 *val = 15; 222 *val2 = 625000; /* 1000 * 0.015625 */ 223 ret = IIO_VAL_INT_PLUS_MICRO; 224 break; 225 default: 226 /* Thermocouple Temp. Data resolution is 0.0078125 */ 227 *val = 7; 228 *val2 = 812500; /* 1000 * 0.0078125) */ 229 return IIO_VAL_INT_PLUS_MICRO; 230 } 231 break; 232 case IIO_CHAN_INFO_OVERSAMPLING_RATIO: 233 *val = 1 << data->averaging; 234 return IIO_VAL_INT; 235 default: 236 ret = -EINVAL; 237 break; 238 } 239 240 return ret; 241 } 242 243 static int max31856_write_raw(struct iio_dev *indio_dev, 244 struct iio_chan_spec const *chan, 245 int val, int val2, long mask) 246 { 247 struct max31856_data *data = iio_priv(indio_dev); 248 int msb; 249 250 switch (mask) { 251 case IIO_CHAN_INFO_OVERSAMPLING_RATIO: 252 if (val > 16 || val < 1) 253 return -EINVAL; 254 msb = fls(val) - 1; 255 /* Round up to next 2pow if needed */ 256 if (BIT(msb) < val) 257 msb++; 258 259 data->averaging = msb; 260 max31856_init(data); 261 break; 262 263 default: 264 return -EINVAL; 265 } 266 267 return 0; 268 } 269 270 static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf) 271 { 272 struct iio_dev *indio_dev = dev_to_iio_dev(dev); 273 struct max31856_data *data = iio_priv(indio_dev); 274 u8 reg_val; 275 int ret; 276 bool fault; 277 278 ret = max31856_read(data, MAX31856_SR_REG, ®_val, 1); 279 if (ret) 280 return ret; 281 282 fault = reg_val & faultbit; 283 284 return sprintf(buf, "%d\n", fault); 285 } 286 287 static ssize_t show_fault_ovuv(struct device *dev, 288 struct device_attribute *attr, 289 char *buf) 290 { 291 return show_fault(dev, MAX31856_FAULT_OVUV, buf); 292 } 293 294 static ssize_t show_fault_oc(struct device *dev, 295 struct device_attribute *attr, 296 char *buf) 297 { 298 return show_fault(dev, MAX31856_FAULT_OPEN, buf); 299 } 300 301 static ssize_t show_filter(struct device *dev, 302 struct device_attribute *attr, 303 char *buf) 304 { 305 struct iio_dev *indio_dev = dev_to_iio_dev(dev); 306 struct max31856_data *data = iio_priv(indio_dev); 307 308 return sprintf(buf, "%d\n", data->filter_50hz ? 50 : 60); 309 } 310 311 static ssize_t set_filter(struct device *dev, 312 struct device_attribute *attr, 313 const char *buf, 314 size_t len) 315 { 316 struct iio_dev *indio_dev = dev_to_iio_dev(dev); 317 struct max31856_data *data = iio_priv(indio_dev); 318 unsigned int freq; 319 int ret; 320 321 ret = kstrtouint(buf, 10, &freq); 322 if (ret) 323 return ret; 324 325 switch (freq) { 326 case 50: 327 data->filter_50hz = true; 328 break; 329 case 60: 330 data->filter_50hz = false; 331 break; 332 default: 333 return -EINVAL; 334 } 335 336 max31856_init(data); 337 return len; 338 } 339 340 static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0); 341 static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0); 342 static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644, 343 show_filter, set_filter, 0); 344 345 static struct attribute *max31856_attributes[] = { 346 &iio_dev_attr_fault_ovuv.dev_attr.attr, 347 &iio_dev_attr_fault_oc.dev_attr.attr, 348 &iio_dev_attr_in_temp_filter_notch_center_frequency.dev_attr.attr, 349 NULL, 350 }; 351 352 static const struct attribute_group max31856_group = { 353 .attrs = max31856_attributes, 354 }; 355 356 static const struct iio_info max31856_info = { 357 .read_raw = max31856_read_raw, 358 .write_raw = max31856_write_raw, 359 .attrs = &max31856_group, 360 }; 361 362 static int max31856_probe(struct spi_device *spi) 363 { 364 const struct spi_device_id *id = spi_get_device_id(spi); 365 struct iio_dev *indio_dev; 366 struct max31856_data *data; 367 int ret; 368 369 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data)); 370 if (!indio_dev) 371 return -ENOMEM; 372 373 data = iio_priv(indio_dev); 374 data->spi = spi; 375 data->filter_50hz = false; 376 377 spi_set_drvdata(spi, indio_dev); 378 379 indio_dev->info = &max31856_info; 380 indio_dev->dev.parent = &spi->dev; 381 indio_dev->dev.of_node = spi->dev.of_node; 382 indio_dev->name = id->name; 383 indio_dev->modes = INDIO_DIRECT_MODE; 384 indio_dev->channels = max31856_channels; 385 indio_dev->num_channels = ARRAY_SIZE(max31856_channels); 386 387 ret = of_property_read_u32(spi->dev.of_node, "thermocouple-type", 388 &data->thermocouple_type); 389 390 if (ret) { 391 dev_info(&spi->dev, 392 "Could not read thermocouple type DT property, configuring as a K-Type\n"); 393 data->thermocouple_type = THERMOCOUPLE_TYPE_K; 394 } 395 396 /* 397 * no need to translate values as the supported types 398 * have the same value as the #defines 399 */ 400 switch (data->thermocouple_type) { 401 case THERMOCOUPLE_TYPE_B: 402 case THERMOCOUPLE_TYPE_E: 403 case THERMOCOUPLE_TYPE_J: 404 case THERMOCOUPLE_TYPE_K: 405 case THERMOCOUPLE_TYPE_N: 406 case THERMOCOUPLE_TYPE_R: 407 case THERMOCOUPLE_TYPE_S: 408 case THERMOCOUPLE_TYPE_T: 409 break; 410 default: 411 dev_err(&spi->dev, 412 "error: thermocouple-type %u not supported by max31856\n" 413 , data->thermocouple_type); 414 return -EINVAL; 415 } 416 417 ret = max31856_init(data); 418 if (ret) { 419 dev_err(&spi->dev, "error: Failed to configure max31856\n"); 420 return ret; 421 } 422 423 return devm_iio_device_register(&spi->dev, indio_dev); 424 } 425 426 static const struct spi_device_id max31856_id[] = { 427 { "max31856", 0 }, 428 { } 429 }; 430 MODULE_DEVICE_TABLE(spi, max31856_id); 431 432 static const struct of_device_id max31856_of_match[] = { 433 { .compatible = "maxim,max31856" }, 434 { } 435 }; 436 MODULE_DEVICE_TABLE(of, max31856_of_match); 437 438 static struct spi_driver max31856_driver = { 439 .driver = { 440 .name = "max31856", 441 .of_match_table = max31856_of_match, 442 }, 443 .probe = max31856_probe, 444 .id_table = max31856_id, 445 }; 446 module_spi_driver(max31856_driver); 447 448 MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>"); 449 MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>"); 450 MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver"); 451 MODULE_LICENSE("GPL"); 452