drivers/iio/adc/max9611.c

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