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/module.h> 11 #include <linux/init.h> 12 #include <linux/err.h> 13 #include <linux/spi/spi.h> 14 #include <linux/iio/iio.h> 15 #include <linux/iio/sysfs.h> 16 #include <linux/util_macros.h> 17 #include <asm/unaligned.h> 18 #include <dt-bindings/iio/temperature/thermocouple.h> 19 /* 20 * The MSB of the register value determines whether the following byte will 21 * be written or read. If it is 0, one or more byte reads will follow. 22 */ 23 #define MAX31856_RD_WR_BIT BIT(7) 24 25 #define MAX31856_CR0_AUTOCONVERT BIT(7) 26 #define MAX31856_CR0_1SHOT BIT(6) 27 #define MAX31856_CR0_OCFAULT BIT(4) 28 #define MAX31856_CR0_OCFAULT_MASK GENMASK(5, 4) 29 #define MAX31856_CR0_FILTER_50HZ BIT(0) 30 #define MAX31856_AVERAGING_MASK GENMASK(6, 4) 31 #define MAX31856_AVERAGING_SHIFT 4 32 #define MAX31856_TC_TYPE_MASK GENMASK(3, 0) 33 #define MAX31856_FAULT_OVUV BIT(1) 34 #define MAX31856_FAULT_OPEN BIT(0) 35 36 /* The MAX31856 registers */ 37 #define MAX31856_CR0_REG 0x00 38 #define MAX31856_CR1_REG 0x01 39 #define MAX31856_MASK_REG 0x02 40 #define MAX31856_CJHF_REG 0x03 41 #define MAX31856_CJLF_REG 0x04 42 #define MAX31856_LTHFTH_REG 0x05 43 #define MAX31856_LTHFTL_REG 0x06 44 #define MAX31856_LTLFTH_REG 0x07 45 #define MAX31856_LTLFTL_REG 0x08 46 #define MAX31856_CJTO_REG 0x09 47 #define MAX31856_CJTH_REG 0x0A 48 #define MAX31856_CJTL_REG 0x0B 49 #define MAX31856_LTCBH_REG 0x0C 50 #define MAX31856_LTCBM_REG 0x0D 51 #define MAX31856_LTCBL_REG 0x0E 52 #define MAX31856_SR_REG 0x0F 53 54 static const struct iio_chan_spec max31856_channels[] = { 55 { /* Thermocouple Temperature */ 56 .type = IIO_TEMP, 57 .info_mask_separate = 58 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE) | 59 BIT(IIO_CHAN_INFO_THERMOCOUPLE_TYPE), 60 .info_mask_shared_by_type = 61 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) 62 }, 63 { /* Cold Junction Temperature */ 64 .type = IIO_TEMP, 65 .channel2 = IIO_MOD_TEMP_AMBIENT, 66 .modified = 1, 67 .info_mask_separate = 68 BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE), 69 .info_mask_shared_by_type = 70 BIT(IIO_CHAN_INFO_OVERSAMPLING_RATIO) 71 }, 72 }; 73 74 struct max31856_data { 75 struct spi_device *spi; 76 u32 thermocouple_type; 77 bool filter_50hz; 78 int averaging; 79 }; 80 81 static const char max31856_tc_types[] = { 82 'B', 'E', 'J', 'K', 'N', 'R', 'S', 'T' 83 }; 84 85 static int max31856_read(struct max31856_data *data, u8 reg, 86 u8 val[], unsigned int read_size) 87 { 88 return spi_write_then_read(data->spi, ®, 1, val, read_size); 89 } 90 91 static int max31856_write(struct max31856_data *data, u8 reg, 92 unsigned int val) 93 { 94 u8 buf[2]; 95 96 buf[0] = reg | (MAX31856_RD_WR_BIT); 97 buf[1] = val; 98 99 return spi_write(data->spi, buf, 2); 100 } 101 102 static int max31856_init(struct max31856_data *data) 103 { 104 int ret; 105 u8 reg_cr0_val, reg_cr1_val; 106 107 /* Start by changing to Off mode before making changes as 108 * some settings are recommended to be set only when the device 109 * is off 110 */ 111 ret = max31856_read(data, MAX31856_CR0_REG, ®_cr0_val, 1); 112 if (ret) 113 return ret; 114 115 reg_cr0_val &= ~MAX31856_CR0_AUTOCONVERT; 116 ret = max31856_write(data, MAX31856_CR0_REG, reg_cr0_val); 117 if (ret) 118 return ret; 119 120 /* Set thermocouple type based on dts property */ 121 ret = max31856_read(data, MAX31856_CR1_REG, ®_cr1_val, 1); 122 if (ret) 123 return ret; 124 125 reg_cr1_val &= ~MAX31856_TC_TYPE_MASK; 126 reg_cr1_val |= data->thermocouple_type; 127 128 reg_cr1_val &= ~MAX31856_AVERAGING_MASK; 129 reg_cr1_val |= data->averaging << MAX31856_AVERAGING_SHIFT; 130 131 ret = max31856_write(data, MAX31856_CR1_REG, reg_cr1_val); 132 if (ret) 133 return ret; 134 135 /* 136 * Enable Open circuit fault detection 137 * Read datasheet for more information: Table 4. 138 * Value 01 means : Enabled (Once every 16 conversions) 139 */ 140 reg_cr0_val &= ~MAX31856_CR0_OCFAULT_MASK; 141 reg_cr0_val |= MAX31856_CR0_OCFAULT; 142 143 /* Set Auto Conversion Mode */ 144 reg_cr0_val &= ~MAX31856_CR0_1SHOT; 145 reg_cr0_val |= MAX31856_CR0_AUTOCONVERT; 146 147 if (data->filter_50hz) 148 reg_cr0_val |= MAX31856_CR0_FILTER_50HZ; 149 else 150 reg_cr0_val &= ~MAX31856_CR0_FILTER_50HZ; 151 152 return max31856_write(data, MAX31856_CR0_REG, reg_cr0_val); 153 } 154 155 static int max31856_thermocouple_read(struct max31856_data *data, 156 struct iio_chan_spec const *chan, 157 int *val) 158 { 159 int ret, offset_cjto; 160 u8 reg_val[3]; 161 162 switch (chan->channel2) { 163 case IIO_NO_MOD: 164 /* 165 * Multibyte Read 166 * MAX31856_LTCBH_REG, MAX31856_LTCBM_REG, MAX31856_LTCBL_REG 167 */ 168 ret = max31856_read(data, MAX31856_LTCBH_REG, reg_val, 3); 169 if (ret) 170 return ret; 171 /* Skip last 5 dead bits of LTCBL */ 172 *val = get_unaligned_be24(®_val[0]) >> 5; 173 /* Check 7th bit of LTCBH reg. value for sign*/ 174 if (reg_val[0] & 0x80) 175 *val -= 0x80000; 176 break; 177 178 case IIO_MOD_TEMP_AMBIENT: 179 /* 180 * Multibyte Read 181 * MAX31856_CJTO_REG, MAX31856_CJTH_REG, MAX31856_CJTL_REG 182 */ 183 ret = max31856_read(data, MAX31856_CJTO_REG, reg_val, 3); 184 if (ret) 185 return ret; 186 /* Get Cold Junction Temp. offset register value */ 187 offset_cjto = reg_val[0]; 188 /* Get CJTH and CJTL value and skip last 2 dead bits of CJTL */ 189 *val = get_unaligned_be16(®_val[1]) >> 2; 190 /* As per datasheet add offset into CJTH and CJTL */ 191 *val += offset_cjto; 192 /* Check 7th bit of CJTH reg. value for sign */ 193 if (reg_val[1] & 0x80) 194 *val -= 0x4000; 195 break; 196 197 default: 198 return -EINVAL; 199 } 200 201 ret = max31856_read(data, MAX31856_SR_REG, reg_val, 1); 202 if (ret) 203 return ret; 204 /* Check for over/under voltage or open circuit fault */ 205 if (reg_val[0] & (MAX31856_FAULT_OVUV | MAX31856_FAULT_OPEN)) 206 return -EIO; 207 208 return ret; 209 } 210 211 static int max31856_read_raw(struct iio_dev *indio_dev, 212 struct iio_chan_spec const *chan, 213 int *val, int *val2, long mask) 214 { 215 struct max31856_data *data = iio_priv(indio_dev); 216 int ret; 217 218 switch (mask) { 219 case IIO_CHAN_INFO_RAW: 220 ret = max31856_thermocouple_read(data, chan, val); 221 if (ret) 222 return ret; 223 return IIO_VAL_INT; 224 case IIO_CHAN_INFO_SCALE: 225 switch (chan->channel2) { 226 case IIO_MOD_TEMP_AMBIENT: 227 /* Cold junction Temp. Data resolution is 0.015625 */ 228 *val = 15; 229 *val2 = 625000; /* 1000 * 0.015625 */ 230 ret = IIO_VAL_INT_PLUS_MICRO; 231 break; 232 default: 233 /* Thermocouple Temp. Data resolution is 0.0078125 */ 234 *val = 7; 235 *val2 = 812500; /* 1000 * 0.0078125) */ 236 return IIO_VAL_INT_PLUS_MICRO; 237 } 238 break; 239 case IIO_CHAN_INFO_OVERSAMPLING_RATIO: 240 *val = 1 << data->averaging; 241 return IIO_VAL_INT; 242 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE: 243 *val = max31856_tc_types[data->thermocouple_type]; 244 return IIO_VAL_CHAR; 245 default: 246 ret = -EINVAL; 247 break; 248 } 249 250 return ret; 251 } 252 253 static int max31856_write_raw_get_fmt(struct iio_dev *indio_dev, 254 struct iio_chan_spec const *chan, 255 long mask) 256 { 257 switch (mask) { 258 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE: 259 return IIO_VAL_CHAR; 260 default: 261 return IIO_VAL_INT; 262 } 263 } 264 265 static int max31856_write_raw(struct iio_dev *indio_dev, 266 struct iio_chan_spec const *chan, 267 int val, int val2, long mask) 268 { 269 struct max31856_data *data = iio_priv(indio_dev); 270 int msb; 271 272 switch (mask) { 273 case IIO_CHAN_INFO_OVERSAMPLING_RATIO: 274 if (val > 16 || val < 1) 275 return -EINVAL; 276 msb = fls(val) - 1; 277 /* Round up to next 2pow if needed */ 278 if (BIT(msb) < val) 279 msb++; 280 281 data->averaging = msb; 282 max31856_init(data); 283 break; 284 case IIO_CHAN_INFO_THERMOCOUPLE_TYPE: 285 { 286 int tc_type = -1; 287 int i; 288 289 for (i = 0; i < ARRAY_SIZE(max31856_tc_types); i++) { 290 if (max31856_tc_types[i] == toupper(val)) { 291 tc_type = i; 292 break; 293 } 294 } 295 if (tc_type < 0) 296 return -EINVAL; 297 298 data->thermocouple_type = tc_type; 299 max31856_init(data); 300 break; 301 } 302 default: 303 return -EINVAL; 304 } 305 306 return 0; 307 } 308 309 static ssize_t show_fault(struct device *dev, u8 faultbit, char *buf) 310 { 311 struct iio_dev *indio_dev = dev_to_iio_dev(dev); 312 struct max31856_data *data = iio_priv(indio_dev); 313 u8 reg_val; 314 int ret; 315 bool fault; 316 317 ret = max31856_read(data, MAX31856_SR_REG, ®_val, 1); 318 if (ret) 319 return ret; 320 321 fault = reg_val & faultbit; 322 323 return sprintf(buf, "%d\n", fault); 324 } 325 326 static ssize_t show_fault_ovuv(struct device *dev, 327 struct device_attribute *attr, 328 char *buf) 329 { 330 return show_fault(dev, MAX31856_FAULT_OVUV, buf); 331 } 332 333 static ssize_t show_fault_oc(struct device *dev, 334 struct device_attribute *attr, 335 char *buf) 336 { 337 return show_fault(dev, MAX31856_FAULT_OPEN, buf); 338 } 339 340 static ssize_t show_filter(struct device *dev, 341 struct device_attribute *attr, 342 char *buf) 343 { 344 struct iio_dev *indio_dev = dev_to_iio_dev(dev); 345 struct max31856_data *data = iio_priv(indio_dev); 346 347 return sprintf(buf, "%d\n", data->filter_50hz ? 50 : 60); 348 } 349 350 static ssize_t set_filter(struct device *dev, 351 struct device_attribute *attr, 352 const char *buf, 353 size_t len) 354 { 355 struct iio_dev *indio_dev = dev_to_iio_dev(dev); 356 struct max31856_data *data = iio_priv(indio_dev); 357 unsigned int freq; 358 int ret; 359 360 ret = kstrtouint(buf, 10, &freq); 361 if (ret) 362 return ret; 363 364 switch (freq) { 365 case 50: 366 data->filter_50hz = true; 367 break; 368 case 60: 369 data->filter_50hz = false; 370 break; 371 default: 372 return -EINVAL; 373 } 374 375 max31856_init(data); 376 return len; 377 } 378 379 static IIO_DEVICE_ATTR(fault_ovuv, 0444, show_fault_ovuv, NULL, 0); 380 static IIO_DEVICE_ATTR(fault_oc, 0444, show_fault_oc, NULL, 0); 381 static IIO_DEVICE_ATTR(in_temp_filter_notch_center_frequency, 0644, 382 show_filter, set_filter, 0); 383 384 static struct attribute *max31856_attributes[] = { 385 &iio_dev_attr_fault_ovuv.dev_attr.attr, 386 &iio_dev_attr_fault_oc.dev_attr.attr, 387 &iio_dev_attr_in_temp_filter_notch_center_frequency.dev_attr.attr, 388 NULL, 389 }; 390 391 static const struct attribute_group max31856_group = { 392 .attrs = max31856_attributes, 393 }; 394 395 static const struct iio_info max31856_info = { 396 .read_raw = max31856_read_raw, 397 .write_raw = max31856_write_raw, 398 .write_raw_get_fmt = max31856_write_raw_get_fmt, 399 .attrs = &max31856_group, 400 }; 401 402 static int max31856_probe(struct spi_device *spi) 403 { 404 const struct spi_device_id *id = spi_get_device_id(spi); 405 struct iio_dev *indio_dev; 406 struct max31856_data *data; 407 int ret; 408 409 indio_dev = devm_iio_device_alloc(&spi->dev, sizeof(*data)); 410 if (!indio_dev) 411 return -ENOMEM; 412 413 data = iio_priv(indio_dev); 414 data->spi = spi; 415 data->filter_50hz = false; 416 417 spi_set_drvdata(spi, indio_dev); 418 419 indio_dev->info = &max31856_info; 420 indio_dev->name = id->name; 421 indio_dev->modes = INDIO_DIRECT_MODE; 422 indio_dev->channels = max31856_channels; 423 indio_dev->num_channels = ARRAY_SIZE(max31856_channels); 424 425 ret = of_property_read_u32(spi->dev.of_node, "thermocouple-type", 426 &data->thermocouple_type); 427 428 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