drivers/iio/temperature/max31856.c

   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, &reg, 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, &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, &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(&reg_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(&reg_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, &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");