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(15, 7)
  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 /*
  93  * Conversion time is 2 ms (typically) at Ta=25 degreeC
  94  * No maximum value is known, so play it safe.
  95  */
  96 #define MAX9611_CONV_TIME_US_RANGE      3000, 3300
  97
  98 struct max9611_dev {
  99         struct device *dev;
 100         struct i2c_client *i2c_client;
 101         struct mutex lock;
 102         unsigned int shunt_resistor_uohm;
 103 };
 104
 105 enum max9611_conf_ids {
 106         CONF_SENSE_1x,
 107         CONF_SENSE_4x,
 108         CONF_SENSE_8x,
 109         CONF_IN_VOLT,
 110         CONF_TEMP,
 111 };
 112
 113 /*
 114  * max9611_mux_conf - associate ADC mux configuration with register address
 115  *                    where data shall be read from
 116  */
 117 static const unsigned int max9611_mux_conf[][2] = {
 118         [CONF_SENSE_1x] = { MAX9611_MUX_SENSE_1x, MAX9611_REG_CSA_DATA },
 119         [CONF_SENSE_4x] = { MAX9611_MUX_SENSE_4x, MAX9611_REG_CSA_DATA },
 120         [CONF_SENSE_8x] = { MAX9611_MUX_SENSE_8x, MAX9611_REG_CSA_DATA },
 121         [CONF_IN_VOLT]  = { MAX9611_INPUT_VOLT, MAX9611_REG_RS_DATA },
 122         [CONF_TEMP]     = { MAX9611_MUX_TEMP, MAX9611_REG_TEMP_DATA },
 123 };
 124
 125 enum max9611_csa_gain {
 126         CSA_GAIN_1x = CONF_SENSE_1x,
 127         CSA_GAIN_4x = CONF_SENSE_4x,
 128         CSA_GAIN_8x = CONF_SENSE_8x,
 129 };
 130
 131 enum max9611_csa_gain_params {
 132         CSA_GAIN_LSB_nV,
 133         CSA_GAIN_OFFS_RAW,
 134 };
 135
 136 /*
 137  * max9611_csa_gain_conf - associate gain multiplier with LSB and
 138  *                         offset values.
 139  *
 140  * Group together parameters associated with configurable gain
 141  * on current sense amplifier path to ADC interface.
 142  * Current sense read routine adjusts gain until it gets a meaningful
 143  * value; use this structure to retrieve the correct LSB and offset values.
 144  */
 145 static const unsigned int max9611_gain_conf[][2] = {
 146         [CSA_GAIN_1x] = { MAX9611_CSA_1X_LSB_nV, MAX9611_CSA_1X_OFFS_RAW, },
 147         [CSA_GAIN_4x] = { MAX9611_CSA_4X_LSB_nV, MAX9611_CSA_4X_OFFS_RAW, },
 148         [CSA_GAIN_8x] = { MAX9611_CSA_8X_LSB_nV, MAX9611_CSA_8X_OFFS_RAW, },
 149 };
 150
 151 enum max9611_chan_addrs {
 152         MAX9611_CHAN_VOLTAGE_INPUT,
 153         MAX9611_CHAN_VOLTAGE_SENSE,
 154         MAX9611_CHAN_TEMPERATURE,
 155         MAX9611_CHAN_CURRENT_LOAD,
 156         MAX9611_CHAN_POWER_LOAD,
 157 };
 158
 159 static const struct iio_chan_spec max9611_channels[] = {
 160         {
 161           .type                 = IIO_TEMP,
 162           .info_mask_separate   = BIT(IIO_CHAN_INFO_RAW) |
 163                                   BIT(IIO_CHAN_INFO_SCALE),
 164           .address              = MAX9611_CHAN_TEMPERATURE,
 165         },
 166         {
 167           .type                 = IIO_VOLTAGE,
 168           .info_mask_separate   = BIT(IIO_CHAN_INFO_PROCESSED),
 169           .address              = MAX9611_CHAN_VOLTAGE_SENSE,
 170           .indexed              = 1,
 171           .channel              = 0,
 172         },
 173         {
 174           .type                 = IIO_VOLTAGE,
 175           .info_mask_separate   = BIT(IIO_CHAN_INFO_RAW)   |
 176                                   BIT(IIO_CHAN_INFO_SCALE) |
 177                                   BIT(IIO_CHAN_INFO_OFFSET),
 178           .address              = MAX9611_CHAN_VOLTAGE_INPUT,
 179           .indexed              = 1,
 180           .channel              = 1,
 181         },
 182         {
 183           .type                 = IIO_CURRENT,
 184           .info_mask_separate   = BIT(IIO_CHAN_INFO_PROCESSED),
 185           .address              = MAX9611_CHAN_CURRENT_LOAD,
 186         },
 187         {
 188           .type                 = IIO_POWER,
 189           .info_mask_separate   = BIT(IIO_CHAN_INFO_PROCESSED),
 190           .address              = MAX9611_CHAN_POWER_LOAD
 191         },
 192 };
 193
 194 /**
 195  * max9611_read_single() - read a single value from ADC interface
 196  *
 197  * Data registers are 16 bit long, spread between two 8 bit registers
 198  * with consecutive addresses.
 199  * Configure ADC mux first, then read register at address "reg_addr".
 200  * The smbus_read_word routine asks for 16 bits and the ADC is kind enough
 201  * to return values from "reg_addr" and "reg_addr + 1" consecutively.
 202  * Data are transmitted with big-endian ordering: MSB arrives first.
 203  *
 204  * @max9611: max9611 device
 205  * @selector: index for mux and register configuration
 206  * @raw_val: the value returned from ADC
 207  */
 208 static int max9611_read_single(struct max9611_dev *max9611,
 209                                enum max9611_conf_ids selector,
 210                                u16 *raw_val)
 211 {
 212         int ret;
 213
 214         u8 mux_conf = max9611_mux_conf[selector][0] & MAX9611_MUX_MASK;
 215         u8 reg_addr = max9611_mux_conf[selector][1];
 216
 217         /*
 218          * Keep mutex lock held during read-write to avoid mux register
 219          * (CTRL1) re-configuration.
 220          */
 221         mutex_lock(&max9611->lock);
 222         ret = i2c_smbus_write_byte_data(max9611->i2c_client,
 223                                         MAX9611_REG_CTRL1, mux_conf);
 224         if (ret) {
 225                 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
 226                         MAX9611_REG_CTRL1, mux_conf);
 227                 mutex_unlock(&max9611->lock);
 228                 return ret;
 229         }
 230
 231         /* need a delay here to make register configuration stabilize. */
 232
 233         usleep_range(MAX9611_CONV_TIME_US_RANGE);
 234
 235         ret = i2c_smbus_read_word_swapped(max9611->i2c_client, reg_addr);
 236         if (ret < 0) {
 237                 dev_err(max9611->dev, "i2c read word from 0x%2x failed\n",
 238                         reg_addr);
 239                 mutex_unlock(&max9611->lock);
 240                 return ret;
 241         }
 242
 243         *raw_val = ret;
 244         mutex_unlock(&max9611->lock);
 245
 246         return 0;
 247 }
 248
 249 /**
 250  * max9611_read_csa_voltage() - read current sense amplifier output voltage
 251  *
 252  * Current sense amplifier output voltage is read through a configurable
 253  * 1x, 4x or 8x gain.
 254  * Start with plain 1x gain, and adjust gain control properly until a
 255  * meaningful value is read from ADC output.
 256  *
 257  * @max9611: max9611 device
 258  * @adc_raw: raw value read from ADC output
 259  * @csa_gain: gain configuration option selector
 260  */
 261 static int max9611_read_csa_voltage(struct max9611_dev *max9611,
 262                                     u16 *adc_raw,
 263                                     enum max9611_csa_gain *csa_gain)
 264 {
 265         enum max9611_conf_ids gain_selectors[] = {
 266                 CONF_SENSE_1x,
 267                 CONF_SENSE_4x,
 268                 CONF_SENSE_8x
 269         };
 270         unsigned int i;
 271         int ret;
 272
 273         for (i = 0; i < ARRAY_SIZE(gain_selectors); ++i) {
 274                 ret = max9611_read_single(max9611, gain_selectors[i], adc_raw);
 275                 if (ret)
 276                         return ret;
 277
 278                 if (*adc_raw > 0) {
 279                         *csa_gain = (enum max9611_csa_gain)gain_selectors[i];
 280                         return 0;
 281                 }
 282         }
 283
 284         return -EIO;
 285 }
 286
 287 static int max9611_read_raw(struct iio_dev *indio_dev,
 288                             struct iio_chan_spec const *chan,
 289                             int *val, int *val2, long mask)
 290 {
 291         struct max9611_dev *dev = iio_priv(indio_dev);
 292         enum max9611_csa_gain gain_selector;
 293         const unsigned int *csa_gain;
 294         u16 adc_data;
 295         int ret;
 296
 297         switch (mask) {
 298         case IIO_CHAN_INFO_RAW:
 299
 300                 switch (chan->address) {
 301                 case MAX9611_CHAN_TEMPERATURE:
 302                         ret = max9611_read_single(dev, CONF_TEMP,
 303                                                   &adc_data);
 304                         if (ret)
 305                                 return -EINVAL;
 306
 307                         *val = MAX9611_TEMP_RAW(adc_data);
 308                         return IIO_VAL_INT;
 309
 310                 case MAX9611_CHAN_VOLTAGE_INPUT:
 311                         ret = max9611_read_single(dev, CONF_IN_VOLT,
 312                                                   &adc_data);
 313                         if (ret)
 314                                 return -EINVAL;
 315
 316                         *val = MAX9611_VOLTAGE_RAW(adc_data);
 317                         return IIO_VAL_INT;
 318                 }
 319
 320                 break;
 321
 322         case IIO_CHAN_INFO_OFFSET:
 323                 /* MAX9611_CHAN_VOLTAGE_INPUT */
 324                 *val = MAX9611_CIM_OFFSET_RAW;
 325
 326                 return IIO_VAL_INT;
 327
 328         case IIO_CHAN_INFO_SCALE:
 329
 330                 switch (chan->address) {
 331                 case MAX9611_CHAN_TEMPERATURE:
 332                         *val = MAX9611_TEMP_SCALE_NUM;
 333                         *val2 = MAX9611_TEMP_SCALE_DIV;
 334
 335                         return IIO_VAL_FRACTIONAL;
 336
 337                 case MAX9611_CHAN_VOLTAGE_INPUT:
 338                         *val = MAX9611_CIM_LSB_mV;
 339
 340                         return IIO_VAL_INT;
 341                 }
 342
 343                 break;
 344
 345         case IIO_CHAN_INFO_PROCESSED:
 346
 347                 switch (chan->address) {
 348                 case MAX9611_CHAN_VOLTAGE_SENSE:
 349                         /*
 350                          * processed (mV): (raw - offset) * LSB (nV) / 10^6
 351                          *
 352                          * Even if max9611 can output raw csa voltage readings,
 353                          * use a produced value as scale depends on gain.
 354                          */
 355                         ret = max9611_read_csa_voltage(dev, &adc_data,
 356                                                        &gain_selector);
 357                         if (ret)
 358                                 return -EINVAL;
 359
 360                         csa_gain = max9611_gain_conf[gain_selector];
 361
 362                         adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
 363                         *val = MAX9611_VOLTAGE_RAW(adc_data) *
 364                                csa_gain[CSA_GAIN_LSB_nV];
 365                         *val2 = 1000000;
 366
 367                         return IIO_VAL_FRACTIONAL;
 368
 369                 case MAX9611_CHAN_CURRENT_LOAD:
 370                         /* processed (mA): Vcsa (nV) / Rshunt (uOhm)  */
 371                         ret = max9611_read_csa_voltage(dev, &adc_data,
 372                                                        &gain_selector);
 373                         if (ret)
 374                                 return -EINVAL;
 375
 376                         csa_gain = max9611_gain_conf[gain_selector];
 377
 378                         adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
 379                         *val = MAX9611_VOLTAGE_RAW(adc_data) *
 380                                csa_gain[CSA_GAIN_LSB_nV];
 381                         *val2 = dev->shunt_resistor_uohm;
 382
 383                         return IIO_VAL_FRACTIONAL;
 384
 385                 case MAX9611_CHAN_POWER_LOAD:
 386                         /*
 387                          * processed (mW): Vin (mV) * Vcsa (uV) /
 388                          *                 Rshunt (uOhm)
 389                          */
 390                         ret = max9611_read_single(dev, CONF_IN_VOLT,
 391                                                   &adc_data);
 392                         if (ret)
 393                                 return -EINVAL;
 394
 395                         adc_data -= MAX9611_CIM_OFFSET_RAW;
 396                         *val = MAX9611_VOLTAGE_RAW(adc_data) *
 397                                MAX9611_CIM_LSB_mV;
 398
 399                         ret = max9611_read_csa_voltage(dev, &adc_data,
 400                                                        &gain_selector);
 401                         if (ret)
 402                                 return -EINVAL;
 403
 404                         csa_gain = max9611_gain_conf[gain_selector];
 405
 406                         /* divide by 10^3 here to avoid 32bit overflow */
 407                         adc_data -= csa_gain[CSA_GAIN_OFFS_RAW];
 408                         *val *= MAX9611_VOLTAGE_RAW(adc_data) *
 409                                 csa_gain[CSA_GAIN_LSB_nV] / 1000;
 410                         *val2 = dev->shunt_resistor_uohm;
 411
 412                         return IIO_VAL_FRACTIONAL;
 413                 }
 414
 415                 break;
 416         }
 417
 418         return -EINVAL;
 419 }
 420
 421 static ssize_t max9611_shunt_resistor_show(struct device *dev,
 422                                            struct device_attribute *attr,
 423                                            char *buf)
 424 {
 425         struct max9611_dev *max9611 = iio_priv(dev_to_iio_dev(dev));
 426         unsigned int i, r;
 427
 428         i = max9611->shunt_resistor_uohm / 1000000;
 429         r = max9611->shunt_resistor_uohm % 1000000;
 430
 431         return sprintf(buf, "%u.%06u\n", i, r);
 432 }
 433
 434 static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
 435                        max9611_shunt_resistor_show, NULL, 0);
 436 static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
 437                        max9611_shunt_resistor_show, NULL, 0);
 438
 439 static struct attribute *max9611_attributes[] = {
 440         &iio_dev_attr_in_power_shunt_resistor.dev_attr.attr,
 441         &iio_dev_attr_in_current_shunt_resistor.dev_attr.attr,
 442         NULL,
 443 };
 444
 445 static const struct attribute_group max9611_attribute_group = {
 446         .attrs = max9611_attributes,
 447 };
 448
 449 static const struct iio_info indio_info = {
 450         .read_raw       = max9611_read_raw,
 451         .attrs          = &max9611_attribute_group,
 452 };
 453
 454 static int max9611_init(struct max9611_dev *max9611)
 455 {
 456         struct i2c_client *client = max9611->i2c_client;
 457         u16 regval;
 458         int ret;
 459
 460         if (!i2c_check_functionality(client->adapter,
 461                                      I2C_FUNC_SMBUS_WRITE_BYTE  |
 462                                      I2C_FUNC_SMBUS_READ_WORD_DATA)) {
 463                 dev_err(max9611->dev,
 464                         "I2c adapter does not support smbus write_byte or read_word functionalities: aborting probe.\n");
 465                 return -EINVAL;
 466         }
 467
 468         /* Make sure die temperature is in range to test communications. */
 469         ret = max9611_read_single(max9611, CONF_TEMP, &regval);
 470         if (ret)
 471                 return ret;
 472
 473         regval &= MAX9611_TEMP_MASK;
 474
 475         if ((regval > MAX9611_TEMP_MAX_POS &&
 476              regval < MAX9611_TEMP_MIN_NEG) ||
 477              regval > MAX9611_TEMP_MAX_NEG) {
 478                 dev_err(max9611->dev,
 479                         "Invalid value received from ADC 0x%4x: aborting\n",
 480                         regval);
 481                 return -EIO;
 482         }
 483
 484         /* Mux shall be zeroed back before applying other configurations */
 485         ret = i2c_smbus_write_byte_data(max9611->i2c_client,
 486                                         MAX9611_REG_CTRL1, 0);
 487         if (ret) {
 488                 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
 489                         MAX9611_REG_CTRL1, 0);
 490                 return ret;
 491         }
 492
 493         ret = i2c_smbus_write_byte_data(max9611->i2c_client,
 494                                         MAX9611_REG_CTRL2, 0);
 495         if (ret) {
 496                 dev_err(max9611->dev, "i2c write byte failed: 0x%2x - 0x%2x\n",
 497                         MAX9611_REG_CTRL2, 0);
 498                 return ret;
 499         }
 500         usleep_range(MAX9611_CONV_TIME_US_RANGE);
 501
 502         return 0;
 503 }
 504
 505 static const struct of_device_id max9611_of_table[] = {
 506         {.compatible = "maxim,max9611", .data = "max9611"},
 507         {.compatible = "maxim,max9612", .data = "max9612"},
 508         { },
 509 };
 510
 511 MODULE_DEVICE_TABLE(of, max9611_of_table);
 512 static int max9611_probe(struct i2c_client *client,
 513                          const struct i2c_device_id *id)
 514 {
 515         const char * const shunt_res_prop = "shunt-resistor-micro-ohms";
 516         const struct device_node *of_node = client->dev.of_node;
 517         const struct of_device_id *of_id =
 518                 of_match_device(max9611_of_table, &client->dev);
 519         struct max9611_dev *max9611;
 520         struct iio_dev *indio_dev;
 521         unsigned int of_shunt;
 522         int ret;
 523
 524         indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
 525         if (!indio_dev)
 526                 return -ENOMEM;
 527
 528         i2c_set_clientdata(client, indio_dev);
 529
 530         max9611                 = iio_priv(indio_dev);
 531         max9611->dev            = &client->dev;
 532         max9611->i2c_client     = client;
 533         mutex_init(&max9611->lock);
 534
 535         ret = of_property_read_u32(of_node, shunt_res_prop, &of_shunt);
 536         if (ret) {
 537                 dev_err(&client->dev,
 538                         "Missing %s property for %pOF node\n",
 539                         shunt_res_prop, of_node);
 540                 return ret;
 541         }
 542         max9611->shunt_resistor_uohm = of_shunt;
 543
 544         ret = max9611_init(max9611);
 545         if (ret)
 546                 return ret;
 547
 548         indio_dev->name         = of_id->data;
 549         indio_dev->modes        = INDIO_DIRECT_MODE;
 550         indio_dev->info         = &indio_info;
 551         indio_dev->channels     = max9611_channels;
 552         indio_dev->num_channels = ARRAY_SIZE(max9611_channels);
 553
 554         return devm_iio_device_register(&client->dev, indio_dev);
 555 }
 556
 557 static struct i2c_driver max9611_driver = {
 558         .driver = {
 559                    .name = DRIVER_NAME,
 560                    .of_match_table = max9611_of_table,
 561         },
 562         .probe = max9611_probe,
 563 };
 564 module_i2c_driver(max9611_driver);
 565
 566 MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
 567 MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
 568 MODULE_LICENSE("GPL v2");