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/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 will 23 * 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 4 34 #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 0x00 40 #define MAX31856_CR1_REG 0x01 41 #define MAX31856_MASK_REG 0x02 42 #define MAX31856_CJHF_REG 0x03 43 #define MAX31856_CJLF_REG 0x04 44 #define MAX31856_LTHFTH_REG 0x05 45 #define MAX31856_LTHFTL_REG 0x06 46 #define MAX31856_LTLFTH_REG 0x07 47 #define MAX31856_LTLFTL_REG 0x08 48 #define MAX31856_CJTO_REG 0x09 49 #define MAX31856_CJTH_REG 0x0A 50 #define MAX31856_CJTL_REG 0x0B 51 #define MAX31856_LTCBH_REG 0x0C 52 #define MAX31856_LTCBM_REG 0x0D 53 #define MAX31856_LTCBL_REG 0x0E 54 #define MAX31856_SR_REG 0x0F 55 56 static 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 76 struct max31856_data { 77 struct spi_device *spi; 78 u32 thermocouple_type; 79 bool filter_50hz; 80 int averaging; 81 }; 82 83 static const char max31856_tc_types[] = { 84 'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T' 85 }; 86 87 static 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 93 static 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 } 103 104 static 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 as 110 * some settings are recommended to be set only when the device 111 * is off 112 */ 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 detection 139 * 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 else 152 reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ; 153 154 return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val); 155 } 156 157 static 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 Read 168 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG 169 */ 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 Read 183 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG 184 */ 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 } 212 213 static 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 } 254 255 static 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 } 266 267 static 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 } 310 311 static 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 } 327 328 static 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 } 334 335 static 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 } 341 342 static 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 } 351 352 static 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 } 380 381 static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0); 382 static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0); 383 static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644, 384 show_filter, set_filter, 0); 385 386 static 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 }; 392 393 static const struct attribute_group max31856_group = { 394 .attrs = max31856_attributes, 395 }; 396 397 static 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 }; 403 404 static 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 types 436 * have the same value as the #defines 437 */ 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 } 463 464 static const struct spi_device_id max31856_id[] = { 465 { "max31856", 0 }, 466 { } 467 }; 468 MODULE_DEVICE_TABLE(spi, max31856_id); 469 470 static const struct of_device_id max31856_of_match[] = { 471 { .compatible = "maxim,max31856" }, 472 { } 473 }; 474 MODULE_DEVICE_TABLE(of, max31856_of_match); 475 476 static 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 }; 484 module_spi_driver(max31856_driver); 485 486 MODULE_AUTHOR("Paresh Chaudhary <paresh.chaudhary@rockwellcollins.com>"); 487 MODULE_AUTHOR("Patrick Havelange <patrick.havelange@essensium.com>"); 488 MODULE_DESCRIPTION("Maxim MAX31856 thermocouple sensor driver"); 489 MODULE_LICENSE("GPL"); 490