drivers/iio/adc/max9611.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * iio/adc/max9611.c
   4  *
   5  * Maxim max9611/max9612 high side current sense amplifier with
   6  * 12-bit ADC interface.
   7  *
   8  * Copyright (C) 2017 Jacopo Mondi
   9  */
  10
  11 /*
  12  * This driver supports input common-mode voltage, current-sense
  13  * amplifier with programmable gains and die temperature reading from
  14  * Maxim max9611/max9612.
  15  *
  16  * Op-amp, analog comparator, and watchdog functionalities are not
  17  * supported by this driver.
  18  */
  19
  20 #include <linux/delay.h>
  21 #include <linux/i2c.h>
  22 #include <linux/iio/iio.h>
  23 #include <linux/iio/sysfs.h>
  24 #include <linux/module.h>
  25 #include <linux/of_device.h>
  26
  27 #define DRIVER_NAME                     "max9611"
  28
  29 /* max9611 register addresses */
  30 #define MAX9611_REG_CSA_DATA            0x00
  31 #define MAX9611_REG_RS_DATA             0x02
  32 #define MAX9611_REG_TEMP_DATA           0x08
  33 #define MAX9611_REG_CTRL1               0x0a
  34 #define MAX9611_REG_CTRL2               0x0b
  35
  36 /* max9611 REG1 mux configuration options */
  37 #define MAX9611_MUX_MASK                GENMASK(3, 0)
  38 #define MAX9611_MUX_SENSE_1x            0x00
  39 #define MAX9611_MUX_SENSE_4x            0x01
  40 #define MAX9611_MUX_SENSE_8x            0x02
  41 #define MAX9611_INPUT_VOLT              0x03
  42 #define MAX9611_MUX_TEMP                0x06
  43
  44 /* max9611 voltage (both csa and input) helper macros */
  45 #define MAX9611_VOLTAGE_SHIFT           0x04
  46 #define MAX9611_VOLTAGE_RAW(_r)         ((_r) >> MAX9611_VOLTAGE_SHIFT)
  47
  48 /*
  49  * max9611 current sense amplifier voltage output:
  50  * LSB and offset values depends on selected gain (1x, 4x, 8x)
  51  *
  52  * GAIN         LSB (nV)        OFFSET (LSB steps)
  53  * 1x           107500          1
  54  * 4x           26880           1
  55  * 8x           13440           3
  56  *
  57  * The complete formula to calculate current sense voltage is:
  58  *     (((adc_read >> 4) - offset) / ((1 / LSB) * 10^-3)
  59  */
  60 #define MAX9611_CSA_1X_LSB_nV           107500
  61 #define MAX9611_CSA_4X_LSB_nV           26880
  62 #define MAX9611_CSA_8X_LSB_nV           13440
  63
  64 #define MAX9611_CSA_1X_OFFS_RAW         1
  65 #define MAX9611_CSA_4X_OFFS_RAW         1
  66 #define MAX9611_CSA_8X_OFFS_RAW         3
  67
  68 /*
  69  * max9611 common input mode (CIM): LSB is 14mV, with 14mV offset at 25 C
  70  *
  71  * The complete formula to calculate input common voltage is:
  72  *     (((adc_read >> 4) * 1000) - offset) / (1 / 14 * 1000)
  73  */
  74 #define MAX9611_CIM_LSB_mV              14
  75 #define MAX9611_CIM_OFFSET_RAW          1
  76
  77 /*
  78  * max9611 temperature reading: LSB is 480 milli degrees Celsius
  79  *
  80  * The complete formula to calculate temperature is:
  81  *     ((adc_read >> 7) * 1000) / (1 / 480 * 1000)
  82  */
  83 #define MAX9611_TEMP_MAX_POS            0x7f80
  84 #define MAX9611_TEMP_MAX_NEG            0xff80
  85 #define MAX9611_TEMP_MIN_NEG            0xd980
  86 #define MAX9611_TEMP_MASK               GENMASK(7, 15)
  87 #define MAX9611_TEMP_SHIFT              0x07
  88 #define MAX9611_TEMP_RAW(_r)            ((_r) >> MAX9611_TEMP_SHIFT)
  89 #define MAX9611_TEMP_SCALE_NUM          1000000
  90 #define MAX9611_TEMP_SCALE_DIV          2083
  91
  92 struct max9611_dev {
  93         struct device *dev;
  94         struct i2c_client *i2c_client;
  95         struct mutex lock;
  96         unsigned int shunt_resistor_uohm;
  97 };
  98
  99 enum max9611_conf_ids {
 100         CONF_SENSE_1x,
 101         CONF_SENSE_4x,
 102         CONF_SENSE_8x,
 103         CONF_IN_VOLT,
 104         CONF_TEMP,
 105 };
 106
 107 /**
 108  * max9611_mux_conf - associate ADC mux configuration with register address
 109  *                    where data shall be read from
 110  */
 111 static const unsigned int max9611_mux_conf[][2] = {
 112         /* CONF_SENSE_1x */
 113         { MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
 114         /* CONF_SENSE_4x */
 115         { MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
 116         /* CONF_SENSE_8x */
 117         { MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
 118         /* CONF_IN_VOLT */
 119         { MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
 120         /* CONF_TEMP */
 121         { MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
 122 };
 123
 124 enum max9611_csa_gain {
 125         CSA_GAIN_1x,
 126         CSA_GAIN_4x,
 127         CSA_GAIN_8x,
 128 };
 129
 130 enum max9611_csa_gain_params {
 131         CSA_GAIN_LSB_nV,
 132         CSA_GAIN_OFFS_RAW,
 133 };
 134
 135 /**
 136  * max9611_csa_gain_conf - associate gain multiplier with LSB and
 137  *                         offset values.
 138  *
 139  * Group together parameters associated with configurable gain
 140  * on current sense amplifier path to ADC interface.
 141  * Current sense read routine adjusts gain until it gets a meaningful
 142  * value; use this structure to retrieve the correct LSB and offset values.
 143  */
 144 static const unsigned int max9611_gain_conf[][2] = {
 145         { /* [0] CSA_GAIN_1x */
 146                 MAX9611_CSA_1X_LSB_nV,
 147                 MAX9611_CSA_1X_OFFS_RAW,
 148         },
 149         { /* [1] CSA_GAIN_4x */
 150                 MAX9611_CSA_4X_LSB_nV,
 151                 MAX9611_CSA_4X_OFFS_RAW,
 152         },
 153         { /* [2] CSA_GAIN_8x */
 154                 MAX9611_CSA_8X_LSB_nV,
 155                 MAX9611_CSA_8X_OFFS_RAW,
 156         },
 157 };
 158
 159 enum max9611_chan_addrs {
 160         MAX9611_CHAN_VOLTAGE_INPUT,
 161         MAX9611_CHAN_VOLTAGE_SENSE,
 162         MAX9611_CHAN_TEMPERATURE,
 163         MAX9611_CHAN_CURRENT_LOAD,
 164         MAX9611_CHAN_POWER_LOAD,
 165 };
 166
 167 static const struct iio_chan_spec max9611_channels[] = {
 168         {
 169           .type                 = IIO_TEMP,
 170           .info_mask_separate   = BIT(IIO_CHAN_INFO_RAW) |
 171                                   BIT(IIO_CHAN_INFO_SCALE),
 172           .address              = MAX9611_CHAN_TEMPERATURE,
 173         },
 174         {
 175           .type                 = IIO_VOLTAGE,
 176           .info_mask_separate   = BIT(IIO_CHAN_INFO_PROCESSED),
 177           .address              = MAX9611_CHAN_VOLTAGE_SENSE,
 178           .indexed              = 1,
 179           .channel              = 0,
 180         },
 181         {
 182           .type                 = IIO_VOLTAGE,
 183           .info_mask_separate   = BIT(IIO_CHAN_INFO_RAW)   |
 184                                   BIT(IIO_CHAN_INFO_SCALE) |
 185                                   BIT(IIO_CHAN_INFO_OFFSET),
 186           .address              = MAX9611_CHAN_VOLTAGE_INPUT,
 187           .indexed              = 1,
 188           .channel              = 1,
 189         },
 190         {
 191           .type                 = IIO_CURRENT,
 192           .info_mask_separate   = BIT(IIO_CHAN_INFO_PROCESSED),
 193           .address              = MAX9611_CHAN_CURRENT_LOAD,
 194         },
 195         {
 196           .type                 = IIO_POWER,
 197           .info_mask_separate   = BIT(IIO_CHAN_INFO_PROCESSED),
 198           .address              = MAX9611_CHAN_POWER_LOAD
 199         },
 200 };
 201
 202 /**
 203  * max9611_read_single() - read a single value from ADC interface
 204  *
 205  * Data registers are 16 bit long, spread between two 8 bit registers
 206  * with consecutive addresses.
 207  * Configure ADC mux first, then read register at address "reg_addr".
 208  * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
 209  * to return values from "reg_addr" and "reg_addr + 1" consecutively.
 210  * Data are transmitted with big-endian ordering: MSB arrives first.
 211  *
 212  * @max9611: max9611 device
 213  * @selector: index for mux and register configuration
 214  * @raw_val: the value returned from ADC
 215  */
 216 static int max9611_read_single(struct max9611_dev *max9611,
 217                                enum max9611_conf_ids selector,
 218                                u16 *raw_val)
 219 {
 220         int ret;
 221
 222         u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
 223         u8 reg_addr = max9611_mux_conf[selector][1];
 224
 225         /*
 226          * Keep mutex lock held during read-write to avoid mux register
 227          * (CTRL1) re-configuration.
 228          */
 229         mutex_lock(&max9611->lock);
 230         ret = i2c_smbus_write_byte_data(max9611->i2c_client,
 231                                         MAX9611_REG_CTRL1, mux_conf);
 232         if (ret) {
 233                 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
 234                         MAX9611_REG_CTRL1, mux_conf);
 235                 mutex_unlock(&max9611->lock);
 236                 return ret;
 237         }
 238
 239         /*
 240          * need a delay here to make register configuration
 241          * stabilize. 1 msec at least, from empirical testing.
 242          */
 243         usleep_range(1000, 2000);
 244
 245         ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
 246         if (ret < 0) {
 247                 dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
 248                         reg_addr);
 249                 mutex_unlock(&max9611->lock);
 250                 return ret;
 251         }
 252
 253         *raw_val = ret;
 254         mutex_unlock(&max9611->lock);
 255
 256         return 0;
 257 }
 258
 259 /**
 260  * max9611_read_csa_voltage() - read current sense amplifier output voltage
 261  *
 262  * Current sense amplifier output voltage is read through a configurable
 263  * 1x, 4x or 8x gain.
 264  * Start with plain 1x gain, and adjust gain control properly until a
 265  * meaningful value is read from ADC output.
 266  *
 267  * @max9611: max9611 device
 268  * @adc_raw: raw value read from ADC output
 269  * @csa_gain: gain configuration option selector
 270  */
 271 static int max9611_read_csa_voltage(struct max9611_dev *max9611,
 272                                     u16 *adc_raw,
 273                                     enum max9611_csa_gain *csa_gain)
 274 {
 275         enum max9611_conf_ids gain_selectors[] = {
 276                 CONF_SENSE_1x,
 277                 CONF_SENSE_4x,
 278                 CONF_SENSE_8x
 279         };
 280         unsigned int i;
 281         int ret;
 282
 283         for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
 284                 ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
 285                 if (ret)
 286                         return ret;
 287
 288                 if (*adc_raw > 0) {
 289                         *csa_gain = (enum max9611_csa_gain)gain_selectors[i];
 290                         return 0;
 291                 }
 292         }
 293
 294         return -EIO;
 295 }
 296
 297 static int max9611_read_raw(struct iio_dev *indio_dev,
 298                             struct iio_chan_spec const *chan,
 299                             int *val, int *val2, long mask)
 300 {
 301         struct max9611_dev *dev = iio_priv(indio_dev);
 302         enum max9611_csa_gain gain_selector;
 303         const unsigned int *csa_gain;
 304         u16 adc_data;
 305         int ret;
 306
 307         switch (mask) {
 308         case IIO_CHAN_INFO_RAW:
 309
 310                 switch (chan->address) {
 311                 case MAX9611_CHAN_TEMPERATURE:
 312                         ret = max9611_read_single(dev, CONF_TEMP,
 313                                                   &adc_data);
 314                         if (ret)
 315                                 return -EINVAL;
 316
 317                         *val = MAX9611_TEMP_RAW(adc_data);
 318                         return IIO_VAL_INT;
 319
 320                 case MAX9611_CHAN_VOLTAGE_INPUT:
 321                         ret = max9611_read_single(dev, CONF_IN_VOLT,
 322                                                   &adc_data);
 323                         if (ret)
 324                                 return -EINVAL;
 325
 326                         *val = MAX9611_VOLTAGE_RAW(adc_data);
 327                         return IIO_VAL_INT;
 328                 }
 329
 330                 break;
 331
 332         case IIO_CHAN_INFO_OFFSET:
 333                 /* MAX9611_CHAN_VOLTAGE_INPUT */
 334                 *val = MAX9611_CIM_OFFSET_RAW;
 335
 336                 return IIO_VAL_INT;
 337
 338         case IIO_CHAN_INFO_SCALE:
 339
 340                 switch (chan->address) {
 341                 case MAX9611_CHAN_TEMPERATURE:
 342                         *val = MAX9611_TEMP_SCALE_NUM;
 343                         *val2 = MAX9611_TEMP_SCALE_DIV;
 344
 345                         return IIO_VAL_FRACTIONAL;
 346
 347                 case MAX9611_CHAN_VOLTAGE_INPUT:
 348                         *val = MAX9611_CIM_LSB_mV;
 349
 350                         return IIO_VAL_INT;
 351                 }
 352
 353                 break;
 354
 355         case IIO_CHAN_INFO_PROCESSED:
 356
 357                 switch (chan->address) {
 358                 case MAX9611_CHAN_VOLTAGE_SENSE:
 359                         /*
 360                          * processed (mV): (raw - offset) * LSB (nV) / 10^6
 361                          *
 362                          * Even if max9611 can output raw csa voltage readings,
 363                          * use a produced value as scale depends on gain.
 364                          */
 365                         ret = max9611_read_csa_voltage(dev, &adc_data,
 366                                                        &gain_selector);
 367                         if (ret)
 368                                 return -EINVAL;
 369
 370                         csa_gain = max9611_gain_conf[gain_selector];
 371
 372                         adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
 373                         *val = MAX9611_VOLTAGE_RAW(adc_data) *
 374                                csa_gain[CSA_GAIN_LSB_nV];
 375                         *val2 = 1000000;
 376
 377                         return IIO_VAL_FRACTIONAL;
 378
 379                 case MAX9611_CHAN_CURRENT_LOAD:
 380                         /* processed (mA): Vcsa (nV) / Rshunt (uOhm)  */
 381                         ret = max9611_read_csa_voltage(dev, &adc_data,
 382                                                        &gain_selector);
 383                         if (ret)
 384                                 return -EINVAL;
 385
 386                         csa_gain = max9611_gain_conf[gain_selector];
 387
 388                         adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
 389                         *val = MAX9611_VOLTAGE_RAW(adc_data) *
 390                                csa_gain[CSA_GAIN_LSB_nV];
 391                         *val2 = dev->shunt_resistor_uohm;
 392
 393                         return IIO_VAL_FRACTIONAL;
 394
 395                 case MAX9611_CHAN_POWER_LOAD:
 396                         /*
 397                          * processed (mW): Vin (mV) * Vcsa (uV) /
 398                          *                 Rshunt (uOhm)
 399                          */
 400                         ret = max9611_read_single(dev, CONF_IN_VOLT,
 401                                                   &adc_data);
 402                         if (ret)
 403                                 return -EINVAL;
 404
 405                         adc_data -= MAX9611_CIM_OFFSET_RAW;
 406                         *val = MAX9611_VOLTAGE_RAW(adc_data) *
 407                                MAX9611_CIM_LSB_mV;
 408
 409                         ret = max9611_read_csa_voltage(dev, &adc_data,
 410                                                        &gain_selector);
 411                         if (ret)
 412                                 return -EINVAL;
 413
 414                         csa_gain = max9611_gain_conf[gain_selector];
 415
 416                         /* divide by 10^3 here to avoid 32bit overflow */
 417                         adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
 418                         *val *= MAX9611_VOLTAGE_RAW(adc_data) *
 419                                 csa_gain[CSA_GAIN_LSB_nV] / 1000;
 420                         *val2 = dev->shunt_resistor_uohm;
 421
 422                         return IIO_VAL_FRACTIONAL;
 423                 }
 424
 425                 break;
 426         }
 427
 428         return -EINVAL;
 429 }
 430
 431 static ssize_t max9611_shunt_resistor_show(struct device *dev,
 432                                            struct device_attribute *attr,
 433                                            char *buf)
 434 {
 435         struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
 436         unsigned int i, r;
 437
 438         i = max9611->shunt_resistor_uohm / 1000000;
 439         r = max9611->shunt_resistor_uohm % 1000000;
 440
 441         return sprintf(buf, "%u.%06u\n", i, r);
 442 }
 443
 444 static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
 445                        max9611_shunt_resistor_show, NULL, 0);
 446 static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
 447                        max9611_shunt_resistor_show, NULL, 0);
 448
 449 static struct attribute *max9611_attributes[] = {
 450         &iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
 451         &iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
 452         NULL,
 453 };
 454
 455 static const struct attribute_group max9611_attribute_group = {
 456         .attrs = max9611_attributes,
 457 };
 458
 459 static const struct iio_info indio_info = {
 460         .read_raw       = max9611_read_raw,
 461         .attrs          = &max9611_attribute_group,
 462 };
 463
 464 static int max9611_init(struct max9611_dev *max9611)
 465 {
 466         struct i2c_client *client = max9611->i2c_client;
 467         u16 regval;
 468         int ret;
 469
 470         if (!i2c_check_functionality(client->adapter,
 471                                      I2C_FUNC_SMBUS_WRITE_BYTE  |
 472                                      I2C_FUNC_SMBUS_READ_WORD_DATA)) {
 473                 dev_err(max9611->dev,
 474                         "I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
 475                 return -EINVAL;
 476         }
 477
 478         /* Make sure die temperature is in range to test communications. */
 479         ret = max9611_read_single(max9611, CONF_TEMP, &regval);
 480         if (ret)
 481                 return ret;
 482
 483         regval = ret & MAX9611_TEMP_MASK;
 484
 485         if ((regval > MAX9611_TEMP_MAX_POS &&
 486              regval < MAX9611_TEMP_MIN_NEG) ||
 487              regval > MAX9611_TEMP_MAX_NEG) {
 488                 dev_err(max9611->dev,
 489                         "Invalid value received from ADC 0x%4x: aborting\n",
 490                         regval);
 491                 return -EIO;
 492         }
 493
 494         /* Mux shall be zeroed back before applying other configurations */
 495         ret = i2c_smbus_write_byte_data(max9611->i2c_client,
 496                                         MAX9611_REG_CTRL1, 0);
 497         if (ret) {
 498                 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
 499                         MAX9611_REG_CTRL1, 0);
 500                 return ret;
 501         }
 502
 503         ret = i2c_smbus_write_byte_data(max9611->i2c_client,
 504                                         MAX9611_REG_CTRL2, 0);
 505         if (ret) {
 506                 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
 507                         MAX9611_REG_CTRL2, 0);
 508                 return ret;
 509         }
 510         usleep_range(1000, 2000);
 511
 512         return 0;
 513 }
 514
 515 static const struct of_device_id max9611_of_table[] = {
 516         {.compatible = "maxim,max9611", .data = "max9611"},
 517         {.compatible = "maxim,max9612", .data = "max9612"},
 518         { },
 519 };
 520
 521 MODULE_DEVICE_TABLE(of, max9611_of_table);
 522 static int max9611_probe(struct i2c_client *client,
 523                          const struct i2c_device_id *id)
 524 {
 525         const char * const shunt_res_prop = "shunt-resistor-micro-ohms";
 526         const struct device_node *of_node = client->dev.of_node;
 527         const struct of_device_id *of_id =
 528                 of_match_device(max9611_of_table, &client->dev);
 529         struct max9611_dev *max9611;
 530         struct iio_dev *indio_dev;
 531         unsigned int of_shunt;
 532         int ret;
 533
 534         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
 535         if (!indio_dev)
 536                 return -ENOMEM;
 537
 538         i2c_set_clientdata(client, indio_dev);
 539
 540         max9611                 = iio_priv(indio_dev);
 541         max9611->dev            = &client->dev;
 542         max9611->i2c_client     = client;
 543         mutex_init(&max9611->lock);
 544
 545         ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
 546         if (ret) {
 547                 dev_err(&client->dev,
 548                         "Missing %s property for %pOF node\n",
 549                         shunt_res_prop, of_node);
 550                 return ret;
 551         }
 552         max9611->shunt_resistor_uohm = of_shunt;
 553
 554         ret = max9611_init(max9611);
 555         if (ret)
 556                 return ret;
 557
 558         indio_dev->dev.parent   = &client->dev;
 559         indio_dev->dev.of_node  = client->dev.of_node;
 560         indio_dev->name         = of_id->data;
 561         indio_dev->modes        = INDIO_DIRECT_MODE;
 562         indio_dev->info         = &indio_info;
 563         indio_dev->channels     = max9611_channels;
 564         indio_dev->num_channels = ARRAY_SIZE(max9611_channels);
 565
 566         return devm_iio_device_register(&client->dev, indio_dev);
 567 }
 568
 569 static struct i2c_driver max9611_driver = {
 570         .driver = {
 571                    .name = DRIVER_NAME,
 572                    .of_match_table = max9611_of_table,
 573         },
 574         .probe = max9611_probe,
 575 };
 576 module_i2c_driver(max9611_driver);
 577
 578 MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
 579 MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
 580 MODULE_LICENSE("GPL v2");