drivers/hwmon/pwm-fan.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * pwm-fan.c - Hwmon driver for fans connected to PWM lines.
   4  *
   5  * Copyright (c) 2014 Samsung Electronics Co., Ltd.
   6  *
   7  * Author: Kamil Debski <[email protected]>
   8  */
   9
  10 #include <linux/hwmon.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/mod_devicetable.h>
  13 #include <linux/module.h>
  14 #include <linux/mutex.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/property.h>
  17 #include <linux/pwm.h>
  18 #include <linux/regulator/consumer.h>
  19 #include <linux/sysfs.h>
  20 #include <linux/thermal.h>
  21 #include <linux/timer.h>
  22
  23 #define MAX_PWM 255
  24
  25 struct pwm_fan_tach {
  26         int irq;
  27         atomic_t pulses;
  28         unsigned int rpm;
  29 };
  30
  31 enum pwm_fan_enable_mode {
  32         pwm_off_reg_off,
  33         pwm_disable_reg_enable,
  34         pwm_enable_reg_enable,
  35         pwm_disable_reg_disable,
  36 };
  37
  38 struct pwm_fan_ctx {
  39         struct device *dev;
  40
  41         struct mutex lock;
  42         struct pwm_device *pwm;
  43         struct pwm_state pwm_state;
  44         struct regulator *reg_en;
  45         enum pwm_fan_enable_mode enable_mode;
  46         bool regulator_enabled;
  47         bool enabled;
  48
  49         int tach_count;
  50         struct pwm_fan_tach *tachs;
  51         u32 *pulses_per_revolution;
  52         ktime_t sample_start;
  53         struct timer_list rpm_timer;
  54
  55         unsigned int pwm_value;
  56         unsigned int pwm_fan_state;
  57         unsigned int pwm_fan_max_state;
  58         unsigned int *pwm_fan_cooling_levels;
  59         struct thermal_cooling_device *cdev;
  60
  61         struct hwmon_chip_info info;
  62         struct hwmon_channel_info fan_channel;
  63 };
  64
  65 /* This handler assumes self resetting edge triggered interrupt. */
  66 static irqreturn_t pulse_handler(int irq, void *dev_id)
  67 {
  68         struct pwm_fan_tach *tach = dev_id;
  69
  70         atomic_inc(&tach->pulses);
  71
  72         return IRQ_HANDLED;
  73 }
  74
  75 static void sample_timer(struct timer_list *t)
  76 {
  77         struct pwm_fan_ctx *ctx = from_timer(ctx, t, rpm_timer);
  78         unsigned int delta = ktime_ms_delta(ktime_get(), ctx->sample_start);
  79         int i;
  80
  81         if (delta) {
  82                 for (i = 0; i < ctx->tach_count; i++) {
  83                         struct pwm_fan_tach *tach = &ctx->tachs[i];
  84                         int pulses;
  85
  86                         pulses = atomic_read(&tach->pulses);
  87                         atomic_sub(pulses, &tach->pulses);
  88                         tach->rpm = (unsigned int)(pulses * 1000 * 60) /
  89                                 (ctx->pulses_per_revolution[i] * delta);
  90                 }
  91
  92                 ctx->sample_start = ktime_get();
  93         }
  94
  95         mod_timer(&ctx->rpm_timer, jiffies + HZ);
  96 }
  97
  98 static void pwm_fan_enable_mode_2_state(int enable_mode,
  99                                         struct pwm_state *state,
 100                                         bool *enable_regulator)
 101 {
 102         switch (enable_mode) {
 103         case pwm_disable_reg_enable:
 104                 /* disable pwm, keep regulator enabled */
 105                 state->enabled = false;
 106                 *enable_regulator = true;
 107                 break;
 108         case pwm_enable_reg_enable:
 109                 /* keep pwm and regulator enabled */
 110                 state->enabled = true;
 111                 *enable_regulator = true;
 112                 break;
 113         case pwm_off_reg_off:
 114         case pwm_disable_reg_disable:
 115                 /* disable pwm and regulator */
 116                 state->enabled = false;
 117                 *enable_regulator = false;
 118         }
 119 }
 120
 121 static int pwm_fan_switch_power(struct pwm_fan_ctx *ctx, bool on)
 122 {
 123         int ret = 0;
 124
 125         if (!ctx->reg_en)
 126                 return ret;
 127
 128         if (!ctx->regulator_enabled && on) {
 129                 ret = regulator_enable(ctx->reg_en);
 130                 if (ret == 0)
 131                         ctx->regulator_enabled = true;
 132         } else if (ctx->regulator_enabled && !on) {
 133                 ret = regulator_disable(ctx->reg_en);
 134                 if (ret == 0)
 135                         ctx->regulator_enabled = false;
 136         }
 137         return ret;
 138 }
 139
 140 static int pwm_fan_power_on(struct pwm_fan_ctx *ctx)
 141 {
 142         struct pwm_state *state = &ctx->pwm_state;
 143         int ret;
 144
 145         if (ctx->enabled)
 146                 return 0;
 147
 148         ret = pwm_fan_switch_power(ctx, true);
 149         if (ret < 0) {
 150                 dev_err(ctx->dev, "failed to enable power supply\n");
 151                 return ret;
 152         }
 153
 154         state->enabled = true;
 155         ret = pwm_apply_might_sleep(ctx->pwm, state);
 156         if (ret) {
 157                 dev_err(ctx->dev, "failed to enable PWM\n");
 158                 goto disable_regulator;
 159         }
 160
 161         ctx->enabled = true;
 162
 163         return 0;
 164
 165 disable_regulator:
 166         pwm_fan_switch_power(ctx, false);
 167         return ret;
 168 }
 169
 170 static int pwm_fan_power_off(struct pwm_fan_ctx *ctx)
 171 {
 172         struct pwm_state *state = &ctx->pwm_state;
 173         bool enable_regulator = false;
 174         int ret;
 175
 176         if (!ctx->enabled)
 177                 return 0;
 178
 179         pwm_fan_enable_mode_2_state(ctx->enable_mode,
 180                                     state,
 181                                     &enable_regulator);
 182
 183         state->enabled = false;
 184         state->duty_cycle = 0;
 185         ret = pwm_apply_might_sleep(ctx->pwm, state);
 186         if (ret) {
 187                 dev_err(ctx->dev, "failed to disable PWM\n");
 188                 return ret;
 189         }
 190
 191         pwm_fan_switch_power(ctx, enable_regulator);
 192
 193         ctx->enabled = false;
 194
 195         return 0;
 196 }
 197
 198 static int  __set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
 199 {
 200         struct pwm_state *state = &ctx->pwm_state;
 201         unsigned long period;
 202         int ret = 0;
 203
 204         if (pwm > 0) {
 205                 if (ctx->enable_mode == pwm_off_reg_off)
 206                         /* pwm-fan hard disabled */
 207                         return 0;
 208
 209                 period = state->period;
 210                 state->duty_cycle = DIV_ROUND_UP(pwm * (period - 1), MAX_PWM);
 211                 ret = pwm_apply_might_sleep(ctx->pwm, state);
 212                 if (ret)
 213                         return ret;
 214                 ret = pwm_fan_power_on(ctx);
 215         } else {
 216                 ret = pwm_fan_power_off(ctx);
 217         }
 218         if (!ret)
 219                 ctx->pwm_value = pwm;
 220
 221         return ret;
 222 }
 223
 224 static int set_pwm(struct pwm_fan_ctx *ctx, unsigned long pwm)
 225 {
 226         int ret;
 227
 228         mutex_lock(&ctx->lock);
 229         ret = __set_pwm(ctx, pwm);
 230         mutex_unlock(&ctx->lock);
 231
 232         return ret;
 233 }
 234
 235 static void pwm_fan_update_state(struct pwm_fan_ctx *ctx, unsigned long pwm)
 236 {
 237         int i;
 238
 239         for (i = 0; i < ctx->pwm_fan_max_state; ++i)
 240                 if (pwm < ctx->pwm_fan_cooling_levels[i + 1])
 241                         break;
 242
 243         ctx->pwm_fan_state = i;
 244 }
 245
 246 static int pwm_fan_update_enable(struct pwm_fan_ctx *ctx, long val)
 247 {
 248         int ret = 0;
 249         int old_val;
 250
 251         mutex_lock(&ctx->lock);
 252
 253         if (ctx->enable_mode == val)
 254                 goto out;
 255
 256         old_val = ctx->enable_mode;
 257         ctx->enable_mode = val;
 258
 259         if (val == 0) {
 260                 /* Disable pwm-fan unconditionally */
 261                 if (ctx->enabled)
 262                         ret = __set_pwm(ctx, 0);
 263                 else
 264                         ret = pwm_fan_switch_power(ctx, false);
 265                 if (ret)
 266                         ctx->enable_mode = old_val;
 267                 pwm_fan_update_state(ctx, 0);
 268         } else {
 269                 /*
 270                  * Change PWM and/or regulator state if currently disabled
 271                  * Nothing to do if currently enabled
 272                  */
 273                 if (!ctx->enabled) {
 274                         struct pwm_state *state = &ctx->pwm_state;
 275                         bool enable_regulator = false;
 276
 277                         state->duty_cycle = 0;
 278                         pwm_fan_enable_mode_2_state(val,
 279                                                     state,
 280                                                     &enable_regulator);
 281
 282                         pwm_apply_might_sleep(ctx->pwm, state);
 283                         pwm_fan_switch_power(ctx, enable_regulator);
 284                         pwm_fan_update_state(ctx, 0);
 285                 }
 286         }
 287 out:
 288         mutex_unlock(&ctx->lock);
 289
 290         return ret;
 291 }
 292
 293 static int pwm_fan_write(struct device *dev, enum hwmon_sensor_types type,
 294                          u32 attr, int channel, long val)
 295 {
 296         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
 297         int ret;
 298
 299         switch (attr) {
 300         case hwmon_pwm_input:
 301                 if (val < 0 || val > MAX_PWM)
 302                         return -EINVAL;
 303                 ret = set_pwm(ctx, val);
 304                 if (ret)
 305                         return ret;
 306                 pwm_fan_update_state(ctx, val);
 307                 break;
 308         case hwmon_pwm_enable:
 309                 if (val < 0 || val > 3)
 310                         ret = -EINVAL;
 311                 else
 312                         ret = pwm_fan_update_enable(ctx, val);
 313
 314                 return ret;
 315         default:
 316                 return -EOPNOTSUPP;
 317         }
 318
 319         return 0;
 320 }
 321
 322 static int pwm_fan_read(struct device *dev, enum hwmon_sensor_types type,
 323                         u32 attr, int channel, long *val)
 324 {
 325         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
 326
 327         switch (type) {
 328         case hwmon_pwm:
 329                 switch (attr) {
 330                 case hwmon_pwm_input:
 331                         *val = ctx->pwm_value;
 332                         return 0;
 333                 case hwmon_pwm_enable:
 334                         *val = ctx->enable_mode;
 335                         return 0;
 336                 }
 337                 return -EOPNOTSUPP;
 338         case hwmon_fan:
 339                 *val = ctx->tachs[channel].rpm;
 340                 return 0;
 341
 342         default:
 343                 return -ENOTSUPP;
 344         }
 345 }
 346
 347 static umode_t pwm_fan_is_visible(const void *data,
 348                                   enum hwmon_sensor_types type,
 349                                   u32 attr, int channel)
 350 {
 351         switch (type) {
 352         case hwmon_pwm:
 353                 return 0644;
 354
 355         case hwmon_fan:
 356                 return 0444;
 357
 358         default:
 359                 return 0;
 360         }
 361 }
 362
 363 static const struct hwmon_ops pwm_fan_hwmon_ops = {
 364         .is_visible = pwm_fan_is_visible,
 365         .read = pwm_fan_read,
 366         .write = pwm_fan_write,
 367 };
 368
 369 /* thermal cooling device callbacks */
 370 static int pwm_fan_get_max_state(struct thermal_cooling_device *cdev,
 371                                  unsigned long *state)
 372 {
 373         struct pwm_fan_ctx *ctx = cdev->devdata;
 374
 375         if (!ctx)
 376                 return -EINVAL;
 377
 378         *state = ctx->pwm_fan_max_state;
 379
 380         return 0;
 381 }
 382
 383 static int pwm_fan_get_cur_state(struct thermal_cooling_device *cdev,
 384                                  unsigned long *state)
 385 {
 386         struct pwm_fan_ctx *ctx = cdev->devdata;
 387
 388         if (!ctx)
 389                 return -EINVAL;
 390
 391         *state = ctx->pwm_fan_state;
 392
 393         return 0;
 394 }
 395
 396 static int
 397 pwm_fan_set_cur_state(struct thermal_cooling_device *cdev, unsigned long state)
 398 {
 399         struct pwm_fan_ctx *ctx = cdev->devdata;
 400         int ret;
 401
 402         if (!ctx || (state > ctx->pwm_fan_max_state))
 403                 return -EINVAL;
 404
 405         if (state == ctx->pwm_fan_state)
 406                 return 0;
 407
 408         ret = set_pwm(ctx, ctx->pwm_fan_cooling_levels[state]);
 409         if (ret) {
 410                 dev_err(&cdev->device, "Cannot set pwm!\n");
 411                 return ret;
 412         }
 413
 414         ctx->pwm_fan_state = state;
 415
 416         return ret;
 417 }
 418
 419 static const struct thermal_cooling_device_ops pwm_fan_cooling_ops = {
 420         .get_max_state = pwm_fan_get_max_state,
 421         .get_cur_state = pwm_fan_get_cur_state,
 422         .set_cur_state = pwm_fan_set_cur_state,
 423 };
 424
 425 static int pwm_fan_get_cooling_data(struct device *dev, struct pwm_fan_ctx *ctx)
 426 {
 427         int num, i, ret;
 428
 429         if (!device_property_present(dev, "cooling-levels"))
 430                 return 0;
 431
 432         ret = device_property_count_u32(dev, "cooling-levels");
 433         if (ret <= 0) {
 434                 dev_err(dev, "Wrong data!\n");
 435                 return ret ? : -EINVAL;
 436         }
 437
 438         num = ret;
 439         ctx->pwm_fan_cooling_levels = devm_kcalloc(dev, num, sizeof(u32),
 440                                                    GFP_KERNEL);
 441         if (!ctx->pwm_fan_cooling_levels)
 442                 return -ENOMEM;
 443
 444         ret = device_property_read_u32_array(dev, "cooling-levels",
 445                                              ctx->pwm_fan_cooling_levels, num);
 446         if (ret) {
 447                 dev_err(dev, "Property 'cooling-levels' cannot be read!\n");
 448                 return ret;
 449         }
 450
 451         for (i = 0; i < num; i++) {
 452                 if (ctx->pwm_fan_cooling_levels[i] > MAX_PWM) {
 453                         dev_err(dev, "PWM fan state[%d]:%d > %d\n", i,
 454                                 ctx->pwm_fan_cooling_levels[i], MAX_PWM);
 455                         return -EINVAL;
 456                 }
 457         }
 458
 459         ctx->pwm_fan_max_state = num - 1;
 460
 461         return 0;
 462 }
 463
 464 static void pwm_fan_cleanup(void *__ctx)
 465 {
 466         struct pwm_fan_ctx *ctx = __ctx;
 467
 468         del_timer_sync(&ctx->rpm_timer);
 469         /* Switch off everything */
 470         ctx->enable_mode = pwm_disable_reg_disable;
 471         pwm_fan_power_off(ctx);
 472 }
 473
 474 static int pwm_fan_probe(struct platform_device *pdev)
 475 {
 476         struct thermal_cooling_device *cdev;
 477         struct device *dev = &pdev->dev;
 478         struct pwm_fan_ctx *ctx;
 479         struct device *hwmon;
 480         int ret;
 481         const struct hwmon_channel_info **channels;
 482         u32 *fan_channel_config;
 483         int channel_count = 1;  /* We always have a PWM channel. */
 484         int i;
 485
 486         ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
 487         if (!ctx)
 488                 return -ENOMEM;
 489
 490         mutex_init(&ctx->lock);
 491
 492         ctx->dev = &pdev->dev;
 493         ctx->pwm = devm_pwm_get(dev, NULL);
 494         if (IS_ERR(ctx->pwm))
 495                 return dev_err_probe(dev, PTR_ERR(ctx->pwm), "Could not get PWM\n");
 496
 497         platform_set_drvdata(pdev, ctx);
 498
 499         ctx->reg_en = devm_regulator_get_optional(dev, "fan");
 500         if (IS_ERR(ctx->reg_en)) {
 501                 if (PTR_ERR(ctx->reg_en) != -ENODEV)
 502                         return PTR_ERR(ctx->reg_en);
 503
 504                 ctx->reg_en = NULL;
 505         }
 506
 507         pwm_init_state(ctx->pwm, &ctx->pwm_state);
 508
 509         /*
 510          * PWM fans are controlled solely by the duty cycle of the PWM signal,
 511          * they do not care about the exact timing. Thus set usage_power to true
 512          * to allow less flexible hardware to work as a PWM source for fan
 513          * control.
 514          */
 515         ctx->pwm_state.usage_power = true;
 516
 517         /*
 518          * set_pwm assumes that MAX_PWM * (period - 1) fits into an unsigned
 519          * long. Check this here to prevent the fan running at a too low
 520          * frequency.
 521          */
 522         if (ctx->pwm_state.period > ULONG_MAX / MAX_PWM + 1) {
 523                 dev_err(dev, "Configured period too big\n");
 524                 return -EINVAL;
 525         }
 526
 527         ctx->enable_mode = pwm_disable_reg_enable;
 528
 529         /*
 530          * Set duty cycle to maximum allowed and enable PWM output as well as
 531          * the regulator. In case of error nothing is changed
 532          */
 533         ret = set_pwm(ctx, MAX_PWM);
 534         if (ret) {
 535                 dev_err(dev, "Failed to configure PWM: %d\n", ret);
 536                 return ret;
 537         }
 538         timer_setup(&ctx->rpm_timer, sample_timer, 0);
 539         ret = devm_add_action_or_reset(dev, pwm_fan_cleanup, ctx);
 540         if (ret)
 541                 return ret;
 542
 543         ctx->tach_count = platform_irq_count(pdev);
 544         if (ctx->tach_count < 0)
 545                 return dev_err_probe(dev, ctx->tach_count,
 546                                      "Could not get number of fan tachometer inputs\n");
 547         dev_dbg(dev, "%d fan tachometer inputs\n", ctx->tach_count);
 548
 549         if (ctx->tach_count) {
 550                 channel_count++;        /* We also have a FAN channel. */
 551
 552                 ctx->tachs = devm_kcalloc(dev, ctx->tach_count,
 553                                           sizeof(struct pwm_fan_tach),
 554                                           GFP_KERNEL);
 555                 if (!ctx->tachs)
 556                         return -ENOMEM;
 557
 558                 ctx->fan_channel.type = hwmon_fan;
 559                 fan_channel_config = devm_kcalloc(dev, ctx->tach_count + 1,
 560                                                   sizeof(u32), GFP_KERNEL);
 561                 if (!fan_channel_config)
 562                         return -ENOMEM;
 563                 ctx->fan_channel.config = fan_channel_config;
 564
 565                 ctx->pulses_per_revolution = devm_kmalloc_array(dev,
 566                                                                 ctx->tach_count,
 567                                                                 sizeof(*ctx->pulses_per_revolution),
 568                                                                 GFP_KERNEL);
 569                 if (!ctx->pulses_per_revolution)
 570                         return -ENOMEM;
 571
 572                 /* Setup default pulses per revolution */
 573                 for (i = 0; i < ctx->tach_count; i++)
 574                         ctx->pulses_per_revolution[i] = 2;
 575
 576                 device_property_read_u32_array(dev, "pulses-per-revolution",
 577                                                ctx->pulses_per_revolution, ctx->tach_count);
 578         }
 579
 580         channels = devm_kcalloc(dev, channel_count + 1,
 581                                 sizeof(struct hwmon_channel_info *), GFP_KERNEL);
 582         if (!channels)
 583                 return -ENOMEM;
 584
 585         channels[0] = HWMON_CHANNEL_INFO(pwm, HWMON_PWM_INPUT | HWMON_PWM_ENABLE);
 586
 587         for (i = 0; i < ctx->tach_count; i++) {
 588                 struct pwm_fan_tach *tach = &ctx->tachs[i];
 589
 590                 tach->irq = platform_get_irq(pdev, i);
 591                 if (tach->irq == -EPROBE_DEFER)
 592                         return tach->irq;
 593                 if (tach->irq > 0) {
 594                         ret = devm_request_irq(dev, tach->irq, pulse_handler, 0,
 595                                                pdev->name, tach);
 596                         if (ret) {
 597                                 dev_err(dev,
 598                                         "Failed to request interrupt: %d\n",
 599                                         ret);
 600                                 return ret;
 601                         }
 602                 }
 603
 604                 if (!ctx->pulses_per_revolution[i]) {
 605                         dev_err(dev, "pulses-per-revolution can't be zero.\n");
 606                         return -EINVAL;
 607                 }
 608
 609                 fan_channel_config[i] = HWMON_F_INPUT;
 610
 611                 dev_dbg(dev, "tach%d: irq=%d, pulses_per_revolution=%d\n",
 612                         i, tach->irq, ctx->pulses_per_revolution[i]);
 613         }
 614
 615         if (ctx->tach_count > 0) {
 616                 ctx->sample_start = ktime_get();
 617                 mod_timer(&ctx->rpm_timer, jiffies + HZ);
 618
 619                 channels[1] = &ctx->fan_channel;
 620         }
 621
 622         ctx->info.ops = &pwm_fan_hwmon_ops;
 623         ctx->info.info = channels;
 624
 625         hwmon = devm_hwmon_device_register_with_info(dev, "pwmfan",
 626                                                      ctx, &ctx->info, NULL);
 627         if (IS_ERR(hwmon)) {
 628                 dev_err(dev, "Failed to register hwmon device\n");
 629                 return PTR_ERR(hwmon);
 630         }
 631
 632         ret = pwm_fan_get_cooling_data(dev, ctx);
 633         if (ret)
 634                 return ret;
 635
 636         ctx->pwm_fan_state = ctx->pwm_fan_max_state;
 637         if (IS_ENABLED(CONFIG_THERMAL)) {
 638                 cdev = devm_thermal_of_cooling_device_register(dev,
 639                         dev->of_node, "pwm-fan", ctx, &pwm_fan_cooling_ops);
 640                 if (IS_ERR(cdev)) {
 641                         ret = PTR_ERR(cdev);
 642                         dev_err(dev,
 643                                 "Failed to register pwm-fan as cooling device: %d\n",
 644                                 ret);
 645                         return ret;
 646                 }
 647                 ctx->cdev = cdev;
 648         }
 649
 650         return 0;
 651 }
 652
 653 static void pwm_fan_shutdown(struct platform_device *pdev)
 654 {
 655         struct pwm_fan_ctx *ctx = platform_get_drvdata(pdev);
 656
 657         pwm_fan_cleanup(ctx);
 658 }
 659
 660 static int pwm_fan_suspend(struct device *dev)
 661 {
 662         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
 663
 664         return pwm_fan_power_off(ctx);
 665 }
 666
 667 static int pwm_fan_resume(struct device *dev)
 668 {
 669         struct pwm_fan_ctx *ctx = dev_get_drvdata(dev);
 670
 671         return set_pwm(ctx, ctx->pwm_value);
 672 }
 673
 674 static DEFINE_SIMPLE_DEV_PM_OPS(pwm_fan_pm, pwm_fan_suspend, pwm_fan_resume);
 675
 676 static const struct of_device_id of_pwm_fan_match[] = {
 677         { .compatible = "pwm-fan", },
 678         {},
 679 };
 680 MODULE_DEVICE_TABLE(of, of_pwm_fan_match);
 681
 682 static struct platform_driver pwm_fan_driver = {
 683         .probe          = pwm_fan_probe,
 684         .shutdown       = pwm_fan_shutdown,
 685         .driver = {
 686                 .name           = "pwm-fan",
 687                 .pm             = pm_sleep_ptr(&pwm_fan_pm),
 688                 .of_match_table = of_pwm_fan_match,
 689         },
 690 };
 691
 692 module_platform_driver(pwm_fan_driver);
 693
 694 MODULE_AUTHOR("Kamil Debski <[email protected]>");
 695 MODULE_ALIAS("platform:pwm-fan");
 696 MODULE_DESCRIPTION("PWM FAN driver");
 697 MODULE_LICENSE("GPL");