LXR linux/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
  98struct max9611_dev {
  99        struct device *dev;
 100        struct i2c_client *i2c_client;
 101        struct mutex lock;
 102        unsigned int shunt_resistor_uohm;
 103};
 104
 105enum 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 */
 117static 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
 125enum 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
 131enum 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 */
 145static 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
 151enum 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
 159static 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 */
 208static 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 */
 261static 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
 287static 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
 421static 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
 434static IIO_DEVICE_ATTR(in_power_shunt_resistor, 0444,
 435                       max9611_shunt_resistor_show, NULL, 0);
 436static IIO_DEVICE_ATTR(in_current_shunt_resistor, 0444,
 437                       max9611_shunt_resistor_show, NULL, 0);
 438
 439static 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
 445static const struct attribute_group max9611_attribute_group = {
 446        .attrs = max9611_attributes,
 447};
 448
 449static const struct iio_info indio_info = {
 450        .read_raw       = max9611_read_raw,
 451        .attrs          = &max9611_attribute_group,
 452};
 453
 454static 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
 505static const struct of_device_id max9611_of_table[] = {
 506        {.compatible = "maxim,max9611", .data = "max9611"},
 507        {.compatible = "maxim,max9612", .data = "max9612"},
 508        { },
 509};
 510
 511MODULE_DEVICE_TABLE(of, max9611_of_table);
 512static 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
 557static struct i2c_driver max9611_driver = {
 558        .driver = {
 559                   .name = DRIVER_NAME,
 560                   .of_match_table = max9611_of_table,
 561        },
 562        .probe = max9611_probe,
 563};
 564module_i2c_driver(max9611_driver);
 565
 566MODULE_AUTHOR("Jacopo Mondi <jacopo+renesas@jmondi.org>");
 567MODULE_DESCRIPTION("Maxim max9611/12 current sense amplifier with 12bit ADC");
 568MODULE_LICENSE("GPL v2");
 569