linux/drivers/hwmon/ntc_thermistor.c
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   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * ntc_thermistor.c - NTC Thermistors
   4 *
   5 *  Copyright (C) 2010 Samsung Electronics
   6 *  MyungJoo Ham <myungjoo.ham@samsung.com>
   7 */
   8
   9#include <linux/slab.h>
  10#include <linux/module.h>
  11#include <linux/math64.h>
  12#include <linux/platform_device.h>
  13#include <linux/err.h>
  14#include <linux/of.h>
  15#include <linux/of_device.h>
  16
  17#include <linux/platform_data/ntc_thermistor.h>
  18
  19#include <linux/iio/consumer.h>
  20
  21#include <linux/hwmon.h>
  22
  23struct ntc_compensation {
  24        int             temp_c;
  25        unsigned int    ohm;
  26};
  27
  28/*
  29 * Used as index in a zero-terminated array, holes not allowed so
  30 * that NTC_LAST is the first empty array entry.
  31 */
  32enum {
  33        NTC_B57330V2103,
  34        NTC_B57891S0103,
  35        NTC_NCP03WB473,
  36        NTC_NCP03WF104,
  37        NTC_NCP15WB473,
  38        NTC_NCP15WL333,
  39        NTC_NCP15XH103,
  40        NTC_NCP18WB473,
  41        NTC_NCP21WB473,
  42        NTC_LAST,
  43};
  44
  45static const struct platform_device_id ntc_thermistor_id[] = {
  46        [NTC_B57330V2103]     = { "b57330v2103",     TYPE_B57330V2103 },
  47        [NTC_B57891S0103]     = { "b57891s0103",     TYPE_B57891S0103 },
  48        [NTC_NCP03WB473]      = { "ncp03wb473",      TYPE_NCPXXWB473 },
  49        [NTC_NCP03WF104]      = { "ncp03wf104",      TYPE_NCPXXWF104 },
  50        [NTC_NCP15WB473]      = { "ncp15wb473",      TYPE_NCPXXWB473 },
  51        [NTC_NCP15WL333]      = { "ncp15wl333",      TYPE_NCPXXWL333 },
  52        [NTC_NCP15XH103]      = { "ncp15xh103",      TYPE_NCPXXXH103 },
  53        [NTC_NCP18WB473]      = { "ncp18wb473",      TYPE_NCPXXWB473 },
  54        [NTC_NCP21WB473]      = { "ncp21wb473",      TYPE_NCPXXWB473 },
  55        [NTC_LAST]            = { },
  56};
  57
  58/*
  59 * A compensation table should be sorted by the values of .ohm
  60 * in descending order.
  61 * The following compensation tables are from the specification of Murata NTC
  62 * Thermistors Datasheet
  63 */
  64static const struct ntc_compensation ncpXXwb473[] = {
  65        { .temp_c       = -40, .ohm     = 1747920 },
  66        { .temp_c       = -35, .ohm     = 1245428 },
  67        { .temp_c       = -30, .ohm     = 898485 },
  68        { .temp_c       = -25, .ohm     = 655802 },
  69        { .temp_c       = -20, .ohm     = 483954 },
  70        { .temp_c       = -15, .ohm     = 360850 },
  71        { .temp_c       = -10, .ohm     = 271697 },
  72        { .temp_c       = -5, .ohm      = 206463 },
  73        { .temp_c       = 0, .ohm       = 158214 },
  74        { .temp_c       = 5, .ohm       = 122259 },
  75        { .temp_c       = 10, .ohm      = 95227 },
  76        { .temp_c       = 15, .ohm      = 74730 },
  77        { .temp_c       = 20, .ohm      = 59065 },
  78        { .temp_c       = 25, .ohm      = 47000 },
  79        { .temp_c       = 30, .ohm      = 37643 },
  80        { .temp_c       = 35, .ohm      = 30334 },
  81        { .temp_c       = 40, .ohm      = 24591 },
  82        { .temp_c       = 45, .ohm      = 20048 },
  83        { .temp_c       = 50, .ohm      = 16433 },
  84        { .temp_c       = 55, .ohm      = 13539 },
  85        { .temp_c       = 60, .ohm      = 11209 },
  86        { .temp_c       = 65, .ohm      = 9328 },
  87        { .temp_c       = 70, .ohm      = 7798 },
  88        { .temp_c       = 75, .ohm      = 6544 },
  89        { .temp_c       = 80, .ohm      = 5518 },
  90        { .temp_c       = 85, .ohm      = 4674 },
  91        { .temp_c       = 90, .ohm      = 3972 },
  92        { .temp_c       = 95, .ohm      = 3388 },
  93        { .temp_c       = 100, .ohm     = 2902 },
  94        { .temp_c       = 105, .ohm     = 2494 },
  95        { .temp_c       = 110, .ohm     = 2150 },
  96        { .temp_c       = 115, .ohm     = 1860 },
  97        { .temp_c       = 120, .ohm     = 1615 },
  98        { .temp_c       = 125, .ohm     = 1406 },
  99};
 100static const struct ntc_compensation ncpXXwl333[] = {
 101        { .temp_c       = -40, .ohm     = 1610154 },
 102        { .temp_c       = -35, .ohm     = 1130850 },
 103        { .temp_c       = -30, .ohm     = 802609 },
 104        { .temp_c       = -25, .ohm     = 575385 },
 105        { .temp_c       = -20, .ohm     = 416464 },
 106        { .temp_c       = -15, .ohm     = 304219 },
 107        { .temp_c       = -10, .ohm     = 224193 },
 108        { .temp_c       = -5, .ohm      = 166623 },
 109        { .temp_c       = 0, .ohm       = 124850 },
 110        { .temp_c       = 5, .ohm       = 94287 },
 111        { .temp_c       = 10, .ohm      = 71747 },
 112        { .temp_c       = 15, .ohm      = 54996 },
 113        { .temp_c       = 20, .ohm      = 42455 },
 114        { .temp_c       = 25, .ohm      = 33000 },
 115        { .temp_c       = 30, .ohm      = 25822 },
 116        { .temp_c       = 35, .ohm      = 20335 },
 117        { .temp_c       = 40, .ohm      = 16115 },
 118        { .temp_c       = 45, .ohm      = 12849 },
 119        { .temp_c       = 50, .ohm      = 10306 },
 120        { .temp_c       = 55, .ohm      = 8314 },
 121        { .temp_c       = 60, .ohm      = 6746 },
 122        { .temp_c       = 65, .ohm      = 5503 },
 123        { .temp_c       = 70, .ohm      = 4513 },
 124        { .temp_c       = 75, .ohm      = 3721 },
 125        { .temp_c       = 80, .ohm      = 3084 },
 126        { .temp_c       = 85, .ohm      = 2569 },
 127        { .temp_c       = 90, .ohm      = 2151 },
 128        { .temp_c       = 95, .ohm      = 1809 },
 129        { .temp_c       = 100, .ohm     = 1529 },
 130        { .temp_c       = 105, .ohm     = 1299 },
 131        { .temp_c       = 110, .ohm     = 1108 },
 132        { .temp_c       = 115, .ohm     = 949 },
 133        { .temp_c       = 120, .ohm     = 817 },
 134        { .temp_c       = 125, .ohm     = 707 },
 135};
 136
 137static const struct ntc_compensation ncpXXwf104[] = {
 138        { .temp_c       = -40, .ohm     = 4397119 },
 139        { .temp_c       = -35, .ohm     = 3088599 },
 140        { .temp_c       = -30, .ohm     = 2197225 },
 141        { .temp_c       = -25, .ohm     = 1581881 },
 142        { .temp_c       = -20, .ohm     = 1151037 },
 143        { .temp_c       = -15, .ohm     = 846579 },
 144        { .temp_c       = -10, .ohm     = 628988 },
 145        { .temp_c       = -5, .ohm      = 471632 },
 146        { .temp_c       = 0, .ohm       = 357012 },
 147        { .temp_c       = 5, .ohm       = 272500 },
 148        { .temp_c       = 10, .ohm      = 209710 },
 149        { .temp_c       = 15, .ohm      = 162651 },
 150        { .temp_c       = 20, .ohm      = 127080 },
 151        { .temp_c       = 25, .ohm      = 100000 },
 152        { .temp_c       = 30, .ohm      = 79222 },
 153        { .temp_c       = 35, .ohm      = 63167 },
 154        { .temp_c       = 40, .ohm      = 50677 },
 155        { .temp_c       = 45, .ohm      = 40904 },
 156        { .temp_c       = 50, .ohm      = 33195 },
 157        { .temp_c       = 55, .ohm      = 27091 },
 158        { .temp_c       = 60, .ohm      = 22224 },
 159        { .temp_c       = 65, .ohm      = 18323 },
 160        { .temp_c       = 70, .ohm      = 15184 },
 161        { .temp_c       = 75, .ohm      = 12635 },
 162        { .temp_c       = 80, .ohm      = 10566 },
 163        { .temp_c       = 85, .ohm      = 8873 },
 164        { .temp_c       = 90, .ohm      = 7481 },
 165        { .temp_c       = 95, .ohm      = 6337 },
 166        { .temp_c       = 100, .ohm     = 5384 },
 167        { .temp_c       = 105, .ohm     = 4594 },
 168        { .temp_c       = 110, .ohm     = 3934 },
 169        { .temp_c       = 115, .ohm     = 3380 },
 170        { .temp_c       = 120, .ohm     = 2916 },
 171        { .temp_c       = 125, .ohm     = 2522 },
 172};
 173
 174static const struct ntc_compensation ncpXXxh103[] = {
 175        { .temp_c       = -40, .ohm     = 247565 },
 176        { .temp_c       = -35, .ohm     = 181742 },
 177        { .temp_c       = -30, .ohm     = 135128 },
 178        { .temp_c       = -25, .ohm     = 101678 },
 179        { .temp_c       = -20, .ohm     = 77373 },
 180        { .temp_c       = -15, .ohm     = 59504 },
 181        { .temp_c       = -10, .ohm     = 46222 },
 182        { .temp_c       = -5, .ohm      = 36244 },
 183        { .temp_c       = 0, .ohm       = 28674 },
 184        { .temp_c       = 5, .ohm       = 22878 },
 185        { .temp_c       = 10, .ohm      = 18399 },
 186        { .temp_c       = 15, .ohm      = 14910 },
 187        { .temp_c       = 20, .ohm      = 12169 },
 188        { .temp_c       = 25, .ohm      = 10000 },
 189        { .temp_c       = 30, .ohm      = 8271 },
 190        { .temp_c       = 35, .ohm      = 6883 },
 191        { .temp_c       = 40, .ohm      = 5762 },
 192        { .temp_c       = 45, .ohm      = 4851 },
 193        { .temp_c       = 50, .ohm      = 4105 },
 194        { .temp_c       = 55, .ohm      = 3492 },
 195        { .temp_c       = 60, .ohm      = 2985 },
 196        { .temp_c       = 65, .ohm      = 2563 },
 197        { .temp_c       = 70, .ohm      = 2211 },
 198        { .temp_c       = 75, .ohm      = 1915 },
 199        { .temp_c       = 80, .ohm      = 1666 },
 200        { .temp_c       = 85, .ohm      = 1454 },
 201        { .temp_c       = 90, .ohm      = 1275 },
 202        { .temp_c       = 95, .ohm      = 1121 },
 203        { .temp_c       = 100, .ohm     = 990 },
 204        { .temp_c       = 105, .ohm     = 876 },
 205        { .temp_c       = 110, .ohm     = 779 },
 206        { .temp_c       = 115, .ohm     = 694 },
 207        { .temp_c       = 120, .ohm     = 620 },
 208        { .temp_c       = 125, .ohm     = 556 },
 209};
 210
 211/*
 212 * The following compensation tables are from the specifications in EPCOS NTC
 213 * Thermistors Datasheets
 214 */
 215static const struct ntc_compensation b57330v2103[] = {
 216        { .temp_c       = -40, .ohm     = 190030 },
 217        { .temp_c       = -35, .ohm     = 145360 },
 218        { .temp_c       = -30, .ohm     = 112060 },
 219        { .temp_c       = -25, .ohm     = 87041 },
 220        { .temp_c       = -20, .ohm     = 68104 },
 221        { .temp_c       = -15, .ohm     = 53665 },
 222        { .temp_c       = -10, .ohm     = 42576 },
 223        { .temp_c       = -5, .ohm      = 34001 },
 224        { .temp_c       = 0, .ohm       = 27326 },
 225        { .temp_c       = 5, .ohm       = 22096 },
 226        { .temp_c       = 10, .ohm      = 17973 },
 227        { .temp_c       = 15, .ohm      = 14703 },
 228        { .temp_c       = 20, .ohm      = 12090 },
 229        { .temp_c       = 25, .ohm      = 10000 },
 230        { .temp_c       = 30, .ohm      = 8311 },
 231        { .temp_c       = 35, .ohm      = 6941 },
 232        { .temp_c       = 40, .ohm      = 5825 },
 233        { .temp_c       = 45, .ohm      = 4911 },
 234        { .temp_c       = 50, .ohm      = 4158 },
 235        { .temp_c       = 55, .ohm      = 3536 },
 236        { .temp_c       = 60, .ohm      = 3019 },
 237        { .temp_c       = 65, .ohm      = 2588 },
 238        { .temp_c       = 70, .ohm      = 2227 },
 239        { .temp_c       = 75, .ohm      = 1924 },
 240        { .temp_c       = 80, .ohm      = 1668 },
 241        { .temp_c       = 85, .ohm      = 1451 },
 242        { .temp_c       = 90, .ohm      = 1266 },
 243        { .temp_c       = 95, .ohm      = 1108 },
 244        { .temp_c       = 100, .ohm     = 973 },
 245        { .temp_c       = 105, .ohm     = 857 },
 246        { .temp_c       = 110, .ohm     = 757 },
 247        { .temp_c       = 115, .ohm     = 671 },
 248        { .temp_c       = 120, .ohm     = 596 },
 249        { .temp_c       = 125, .ohm     = 531 },
 250};
 251
 252static const struct ntc_compensation b57891s0103[] = {
 253        { .temp_c       = -55.0, .ohm   = 878900 },
 254        { .temp_c       = -50.0, .ohm   = 617590 },
 255        { .temp_c       = -45.0, .ohm   = 439340 },
 256        { .temp_c       = -40.0, .ohm   = 316180 },
 257        { .temp_c       = -35.0, .ohm   = 230060 },
 258        { .temp_c       = -30.0, .ohm   = 169150 },
 259        { .temp_c       = -25.0, .ohm   = 125550 },
 260        { .temp_c       = -20.0, .ohm   = 94143 },
 261        { .temp_c       = -15.0, .ohm   = 71172 },
 262        { .temp_c       = -10.0, .ohm   = 54308 },
 263        { .temp_c       = -5.0, .ohm    = 41505 },
 264        { .temp_c       = 0.0, .ohm     = 32014 },
 265        { .temp_c       = 5.0, .ohm     = 25011 },
 266        { .temp_c       = 10.0, .ohm    = 19691 },
 267        { .temp_c       = 15.0, .ohm    = 15618 },
 268        { .temp_c       = 20.0, .ohm    = 12474 },
 269        { .temp_c       = 25.0, .ohm    = 10000 },
 270        { .temp_c       = 30.0, .ohm    = 8080 },
 271        { .temp_c       = 35.0, .ohm    = 6569 },
 272        { .temp_c       = 40.0, .ohm    = 5372 },
 273        { .temp_c       = 45.0, .ohm    = 4424 },
 274        { .temp_c       = 50.0, .ohm    = 3661 },
 275        { .temp_c       = 55.0, .ohm    = 3039 },
 276        { .temp_c       = 60.0, .ohm    = 2536 },
 277        { .temp_c       = 65.0, .ohm    = 2128 },
 278        { .temp_c       = 70.0, .ohm    = 1794 },
 279        { .temp_c       = 75.0, .ohm    = 1518 },
 280        { .temp_c       = 80.0, .ohm    = 1290 },
 281        { .temp_c       = 85.0, .ohm    = 1100 },
 282        { .temp_c       = 90.0, .ohm    = 942 },
 283        { .temp_c       = 95.0, .ohm    = 809 },
 284        { .temp_c       = 100.0, .ohm   = 697 },
 285        { .temp_c       = 105.0, .ohm   = 604 },
 286        { .temp_c       = 110.0, .ohm   = 525 },
 287        { .temp_c       = 115.0, .ohm   = 457 },
 288        { .temp_c       = 120.0, .ohm   = 400 },
 289        { .temp_c       = 125.0, .ohm   = 351 },
 290        { .temp_c       = 130.0, .ohm   = 308 },
 291        { .temp_c       = 135.0, .ohm   = 272 },
 292        { .temp_c       = 140.0, .ohm   = 240 },
 293        { .temp_c       = 145.0, .ohm   = 213 },
 294        { .temp_c       = 150.0, .ohm   = 189 },
 295        { .temp_c       = 155.0, .ohm   = 168 },
 296};
 297
 298struct ntc_type {
 299        const struct ntc_compensation *comp;
 300        int n_comp;
 301};
 302
 303#define NTC_TYPE(ntc, compensation) \
 304[(ntc)] = { .comp = (compensation), .n_comp = ARRAY_SIZE(compensation) }
 305
 306static const struct ntc_type ntc_type[] = {
 307        NTC_TYPE(TYPE_B57330V2103, b57330v2103),
 308        NTC_TYPE(TYPE_B57891S0103, b57891s0103),
 309        NTC_TYPE(TYPE_NCPXXWB473,  ncpXXwb473),
 310        NTC_TYPE(TYPE_NCPXXWF104,  ncpXXwf104),
 311        NTC_TYPE(TYPE_NCPXXWL333,  ncpXXwl333),
 312        NTC_TYPE(TYPE_NCPXXXH103,  ncpXXxh103),
 313};
 314
 315struct ntc_data {
 316        struct ntc_thermistor_platform_data *pdata;
 317        const struct ntc_compensation *comp;
 318        int n_comp;
 319};
 320
 321#if defined(CONFIG_OF) && IS_ENABLED(CONFIG_IIO)
 322static int ntc_adc_iio_read(struct ntc_thermistor_platform_data *pdata)
 323{
 324        struct iio_channel *channel = pdata->chan;
 325        int uv, ret;
 326
 327        ret = iio_read_channel_processed_scale(channel, &uv, 1000);
 328        if (ret < 0) {
 329                int raw;
 330
 331                /*
 332                 * This fallback uses a raw read and then
 333                 * assumes the ADC is 12 bits, scaling with
 334                 * a factor 1000 to get to microvolts.
 335                 */
 336                ret = iio_read_channel_raw(channel, &raw);
 337                if (ret < 0) {
 338                        pr_err("read channel() error: %d\n", ret);
 339                        return ret;
 340                }
 341                ret = iio_convert_raw_to_processed(channel, raw, &uv, 1000);
 342                if (ret < 0) {
 343                        /* Assume 12 bit ADC with vref at pullup_uv */
 344                        uv = (pdata->pullup_uv * (s64)raw) >> 12;
 345                }
 346        }
 347
 348        return uv;
 349}
 350
 351static const struct of_device_id ntc_match[] = {
 352        { .compatible = "epcos,b57330v2103",
 353                .data = &ntc_thermistor_id[NTC_B57330V2103]},
 354        { .compatible = "epcos,b57891s0103",
 355                .data = &ntc_thermistor_id[NTC_B57891S0103] },
 356        { .compatible = "murata,ncp03wb473",
 357                .data = &ntc_thermistor_id[NTC_NCP03WB473] },
 358        { .compatible = "murata,ncp03wf104",
 359                .data = &ntc_thermistor_id[NTC_NCP03WF104] },
 360        { .compatible = "murata,ncp15wb473",
 361                .data = &ntc_thermistor_id[NTC_NCP15WB473] },
 362        { .compatible = "murata,ncp15wl333",
 363                .data = &ntc_thermistor_id[NTC_NCP15WL333] },
 364        { .compatible = "murata,ncp15xh103",
 365                .data = &ntc_thermistor_id[NTC_NCP15XH103] },
 366        { .compatible = "murata,ncp18wb473",
 367                .data = &ntc_thermistor_id[NTC_NCP18WB473] },
 368        { .compatible = "murata,ncp21wb473",
 369                .data = &ntc_thermistor_id[NTC_NCP21WB473] },
 370
 371        /* Usage of vendor name "ntc" is deprecated */
 372        { .compatible = "ntc,ncp03wb473",
 373                .data = &ntc_thermistor_id[NTC_NCP03WB473] },
 374        { .compatible = "ntc,ncp15wb473",
 375                .data = &ntc_thermistor_id[NTC_NCP15WB473] },
 376        { .compatible = "ntc,ncp15wl333",
 377                .data = &ntc_thermistor_id[NTC_NCP15WL333] },
 378        { .compatible = "ntc,ncp18wb473",
 379                .data = &ntc_thermistor_id[NTC_NCP18WB473] },
 380        { .compatible = "ntc,ncp21wb473",
 381                .data = &ntc_thermistor_id[NTC_NCP21WB473] },
 382        { },
 383};
 384MODULE_DEVICE_TABLE(of, ntc_match);
 385
 386static struct ntc_thermistor_platform_data *
 387ntc_thermistor_parse_dt(struct device *dev)
 388{
 389        struct iio_channel *chan;
 390        enum iio_chan_type type;
 391        struct device_node *np = dev->of_node;
 392        struct ntc_thermistor_platform_data *pdata;
 393        int ret;
 394
 395        if (!np)
 396                return NULL;
 397
 398        pdata = devm_kzalloc(dev, sizeof(*pdata), GFP_KERNEL);
 399        if (!pdata)
 400                return ERR_PTR(-ENOMEM);
 401
 402        chan = devm_iio_channel_get(dev, NULL);
 403        if (IS_ERR(chan))
 404                return ERR_CAST(chan);
 405
 406        ret = iio_get_channel_type(chan, &type);
 407        if (ret < 0)
 408                return ERR_PTR(ret);
 409
 410        if (type != IIO_VOLTAGE)
 411                return ERR_PTR(-EINVAL);
 412
 413        if (of_property_read_u32(np, "pullup-uv", &pdata->pullup_uv))
 414                return ERR_PTR(-ENODEV);
 415        if (of_property_read_u32(np, "pullup-ohm", &pdata->pullup_ohm))
 416                return ERR_PTR(-ENODEV);
 417        if (of_property_read_u32(np, "pulldown-ohm", &pdata->pulldown_ohm))
 418                return ERR_PTR(-ENODEV);
 419
 420        if (of_find_property(np, "connected-positive", NULL))
 421                pdata->connect = NTC_CONNECTED_POSITIVE;
 422        else /* status change should be possible if not always on. */
 423                pdata->connect = NTC_CONNECTED_GROUND;
 424
 425        pdata->chan = chan;
 426        pdata->read_uv = ntc_adc_iio_read;
 427
 428        return pdata;
 429}
 430#else
 431static struct ntc_thermistor_platform_data *
 432ntc_thermistor_parse_dt(struct device *dev)
 433{
 434        return NULL;
 435}
 436
 437#define ntc_match       NULL
 438
 439#endif
 440
 441static inline u64 div64_u64_safe(u64 dividend, u64 divisor)
 442{
 443        if (divisor == 0 && dividend == 0)
 444                return 0;
 445        if (divisor == 0)
 446                return UINT_MAX;
 447        return div64_u64(dividend, divisor);
 448}
 449
 450static int get_ohm_of_thermistor(struct ntc_data *data, unsigned int uv)
 451{
 452        struct ntc_thermistor_platform_data *pdata = data->pdata;
 453        u32 puv = pdata->pullup_uv;
 454        u64 n, puo, pdo;
 455        puo = pdata->pullup_ohm;
 456        pdo = pdata->pulldown_ohm;
 457
 458        if (uv == 0)
 459                return (pdata->connect == NTC_CONNECTED_POSITIVE) ?
 460                        INT_MAX : 0;
 461        if (uv >= puv)
 462                return (pdata->connect == NTC_CONNECTED_POSITIVE) ?
 463                        0 : INT_MAX;
 464
 465        if (pdata->connect == NTC_CONNECTED_POSITIVE && puo == 0)
 466                n = div_u64(pdo * (puv - uv), uv);
 467        else if (pdata->connect == NTC_CONNECTED_GROUND && pdo == 0)
 468                n = div_u64(puo * uv, puv - uv);
 469        else if (pdata->connect == NTC_CONNECTED_POSITIVE)
 470                n = div64_u64_safe(pdo * puo * (puv - uv),
 471                                puo * uv - pdo * (puv - uv));
 472        else
 473                n = div64_u64_safe(pdo * puo * uv, pdo * (puv - uv) - puo * uv);
 474
 475        if (n > INT_MAX)
 476                n = INT_MAX;
 477        return n;
 478}
 479
 480static void lookup_comp(struct ntc_data *data, unsigned int ohm,
 481                        int *i_low, int *i_high)
 482{
 483        int start, end, mid;
 484
 485        /*
 486         * Handle special cases: Resistance is higher than or equal to
 487         * resistance in first table entry, or resistance is lower or equal
 488         * to resistance in last table entry.
 489         * In these cases, return i_low == i_high, either pointing to the
 490         * beginning or to the end of the table depending on the condition.
 491         */
 492        if (ohm >= data->comp[0].ohm) {
 493                *i_low = 0;
 494                *i_high = 0;
 495                return;
 496        }
 497        if (ohm <= data->comp[data->n_comp - 1].ohm) {
 498                *i_low = data->n_comp - 1;
 499                *i_high = data->n_comp - 1;
 500                return;
 501        }
 502
 503        /* Do a binary search on compensation table */
 504        start = 0;
 505        end = data->n_comp;
 506        while (start < end) {
 507                mid = start + (end - start) / 2;
 508                /*
 509                 * start <= mid < end
 510                 * data->comp[start].ohm > ohm >= data->comp[end].ohm
 511                 *
 512                 * We could check for "ohm == data->comp[mid].ohm" here, but
 513                 * that is a quite unlikely condition, and we would have to
 514                 * check again after updating start. Check it at the end instead
 515                 * for simplicity.
 516                 */
 517                if (ohm >= data->comp[mid].ohm) {
 518                        end = mid;
 519                } else {
 520                        start = mid + 1;
 521                        /*
 522                         * ohm >= data->comp[start].ohm might be true here,
 523                         * since we set start to mid + 1. In that case, we are
 524                         * done. We could keep going, but the condition is quite
 525                         * likely to occur, so it is worth checking for it.
 526                         */
 527                        if (ohm >= data->comp[start].ohm)
 528                                end = start;
 529                }
 530                /*
 531                 * start <= end
 532                 * data->comp[start].ohm >= ohm >= data->comp[end].ohm
 533                 */
 534        }
 535        /*
 536         * start == end
 537         * ohm >= data->comp[end].ohm
 538         */
 539        *i_low = end;
 540        if (ohm == data->comp[end].ohm)
 541                *i_high = end;
 542        else
 543                *i_high = end - 1;
 544}
 545
 546static int get_temp_mc(struct ntc_data *data, unsigned int ohm)
 547{
 548        int low, high;
 549        int temp;
 550
 551        lookup_comp(data, ohm, &low, &high);
 552        if (low == high) {
 553                /* Unable to use linear approximation */
 554                temp = data->comp[low].temp_c * 1000;
 555        } else {
 556                temp = data->comp[low].temp_c * 1000 +
 557                        ((data->comp[high].temp_c - data->comp[low].temp_c) *
 558                         1000 * ((int)ohm - (int)data->comp[low].ohm)) /
 559                        ((int)data->comp[high].ohm - (int)data->comp[low].ohm);
 560        }
 561        return temp;
 562}
 563
 564static int ntc_thermistor_get_ohm(struct ntc_data *data)
 565{
 566        int read_uv;
 567
 568        if (data->pdata->read_ohm)
 569                return data->pdata->read_ohm();
 570
 571        if (data->pdata->read_uv) {
 572                read_uv = data->pdata->read_uv(data->pdata);
 573                if (read_uv < 0)
 574                        return read_uv;
 575                return get_ohm_of_thermistor(data, read_uv);
 576        }
 577        return -EINVAL;
 578}
 579
 580static int ntc_read(struct device *dev, enum hwmon_sensor_types type,
 581                    u32 attr, int channel, long *val)
 582{
 583        struct ntc_data *data = dev_get_drvdata(dev);
 584        int ohm;
 585
 586        switch (type) {
 587        case hwmon_temp:
 588                switch (attr) {
 589                case hwmon_temp_input:
 590                        ohm = ntc_thermistor_get_ohm(data);
 591                        if (ohm < 0)
 592                                return ohm;
 593                        *val = get_temp_mc(data, ohm);
 594                        return 0;
 595                case hwmon_temp_type:
 596                        *val = 4;
 597                        return 0;
 598                default:
 599                        break;
 600                }
 601                break;
 602        default:
 603                break;
 604        }
 605        return -EINVAL;
 606}
 607
 608static umode_t ntc_is_visible(const void *data, enum hwmon_sensor_types type,
 609                              u32 attr, int channel)
 610{
 611        if (type == hwmon_temp) {
 612                switch (attr) {
 613                case hwmon_temp_input:
 614                case hwmon_temp_type:
 615                        return 0444;
 616                default:
 617                        break;
 618                }
 619        }
 620        return 0;
 621}
 622
 623static const struct hwmon_channel_info *ntc_info[] = {
 624        HWMON_CHANNEL_INFO(chip, HWMON_C_REGISTER_TZ),
 625        HWMON_CHANNEL_INFO(temp, HWMON_T_INPUT | HWMON_T_TYPE),
 626        NULL
 627};
 628
 629static const struct hwmon_ops ntc_hwmon_ops = {
 630        .is_visible = ntc_is_visible,
 631        .read = ntc_read,
 632};
 633
 634static const struct hwmon_chip_info ntc_chip_info = {
 635        .ops = &ntc_hwmon_ops,
 636        .info = ntc_info,
 637};
 638
 639static int ntc_thermistor_probe(struct platform_device *pdev)
 640{
 641        struct device *dev = &pdev->dev;
 642        const struct of_device_id *of_id =
 643                        of_match_device(of_match_ptr(ntc_match), dev);
 644        const struct platform_device_id *pdev_id;
 645        struct ntc_thermistor_platform_data *pdata;
 646        struct device *hwmon_dev;
 647        struct ntc_data *data;
 648
 649        pdata = ntc_thermistor_parse_dt(dev);
 650        if (IS_ERR(pdata))
 651                return PTR_ERR(pdata);
 652        else if (pdata == NULL)
 653                pdata = dev_get_platdata(dev);
 654
 655        if (!pdata) {
 656                dev_err(dev, "No platform init data supplied.\n");
 657                return -ENODEV;
 658        }
 659
 660        /* Either one of the two is required. */
 661        if (!pdata->read_uv && !pdata->read_ohm) {
 662                dev_err(dev,
 663                        "Both read_uv and read_ohm missing. Need either one of the two.\n");
 664                return -EINVAL;
 665        }
 666
 667        if (pdata->read_uv && pdata->read_ohm) {
 668                dev_warn(dev,
 669                         "Only one of read_uv and read_ohm is needed; ignoring read_uv.\n");
 670                pdata->read_uv = NULL;
 671        }
 672
 673        if (pdata->read_uv && (pdata->pullup_uv == 0 ||
 674                                (pdata->pullup_ohm == 0 && pdata->connect ==
 675                                 NTC_CONNECTED_GROUND) ||
 676                                (pdata->pulldown_ohm == 0 && pdata->connect ==
 677                                 NTC_CONNECTED_POSITIVE) ||
 678                                (pdata->connect != NTC_CONNECTED_POSITIVE &&
 679                                 pdata->connect != NTC_CONNECTED_GROUND))) {
 680                dev_err(dev, "Required data to use read_uv not supplied.\n");
 681                return -EINVAL;
 682        }
 683
 684        data = devm_kzalloc(dev, sizeof(struct ntc_data), GFP_KERNEL);
 685        if (!data)
 686                return -ENOMEM;
 687
 688        pdev_id = of_id ? of_id->data : platform_get_device_id(pdev);
 689
 690        data->pdata = pdata;
 691
 692        if (pdev_id->driver_data >= ARRAY_SIZE(ntc_type)) {
 693                dev_err(dev, "Unknown device type: %lu(%s)\n",
 694                                pdev_id->driver_data, pdev_id->name);
 695                return -EINVAL;
 696        }
 697
 698        data->comp   = ntc_type[pdev_id->driver_data].comp;
 699        data->n_comp = ntc_type[pdev_id->driver_data].n_comp;
 700
 701        hwmon_dev = devm_hwmon_device_register_with_info(dev, pdev_id->name,
 702                                                         data, &ntc_chip_info,
 703                                                         NULL);
 704        if (IS_ERR(hwmon_dev)) {
 705                dev_err(dev, "unable to register as hwmon device.\n");
 706                return PTR_ERR(hwmon_dev);
 707        }
 708
 709        dev_info(dev, "Thermistor type: %s successfully probed.\n",
 710                 pdev_id->name);
 711
 712        return 0;
 713}
 714
 715static struct platform_driver ntc_thermistor_driver = {
 716        .driver = {
 717                .name = "ntc-thermistor",
 718                .of_match_table = of_match_ptr(ntc_match),
 719        },
 720        .probe = ntc_thermistor_probe,
 721        .id_table = ntc_thermistor_id,
 722};
 723
 724module_platform_driver(ntc_thermistor_driver);
 725
 726MODULE_DESCRIPTION("NTC Thermistor Driver");
 727MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
 728MODULE_LICENSE("GPL");
 729MODULE_ALIAS("platform:ntc-thermistor");
 730