drivers/devfreq/devfreq.c

   1 /*
   2  * devfreq: Generic Dynamic Voltage and Frequency Scaling (DVFS) Framework
   3  *          for Non-CPU Devices.
   4  *
   5  * Copyright (C) 2011 Samsung Electronics
   6  *      MyungJoo Ham <myungjoo.ham@samsung.com>
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 2 as
  10  * published by the Free Software Foundation.
  11  */
  12
  13 #include <linux/kernel.h>
  14 #include <linux/sched.h>
  15 #include <linux/errno.h>
  16 #include <linux/err.h>
  17 #include <linux/init.h>
  18 #include <linux/module.h>
  19 #include <linux/slab.h>
  20 #include <linux/stat.h>
  21 #include <linux/opp.h>
  22 #include <linux/devfreq.h>
  23 #include <linux/workqueue.h>
  24 #include <linux/platform_device.h>
  25 #include <linux/list.h>
  26 #include <linux/printk.h>
  27 #include <linux/hrtimer.h>
  28 #include "governor.h"
  29
  30 struct class *devfreq_class;
  31
  32 /*
  33  * devfreq_work periodically monitors every registered device.
  34  * The minimum polling interval is one jiffy. The polling interval is
  35  * determined by the minimum polling period among all polling devfreq
  36  * devices. The resolution of polling interval is one jiffy.
  37  */
  38 static bool polling;
  39 static struct workqueue_struct *devfreq_wq;
  40 static struct delayed_work devfreq_work;
  41
  42 /* wait removing if this is to be removed */
  43 static struct devfreq *wait_remove_device;
  44
  45 /* The list of all device-devfreq */
  46 static LIST_HEAD(devfreq_list);
  47 static DEFINE_MUTEX(devfreq_list_lock);
  48
  49 /**
  50  * find_device_devfreq() - find devfreq struct using device pointer
  51  * @dev:        device pointer used to lookup device devfreq.
  52  *
  53  * Search the list of device devfreqs and return the matched device's
  54  * devfreq info. devfreq_list_lock should be held by the caller.
  55  */
  56 static struct devfreq *find_device_devfreq(struct device *dev)
  57 {
  58         struct devfreq *tmp_devfreq;
  59
  60         if (unlikely(IS_ERR_OR_NULL(dev))) {
  61                 pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
  62                 return ERR_PTR(-EINVAL);
  63         }
  64         WARN(!mutex_is_locked(&devfreq_list_lock),
  65              "devfreq_list_lock must be locked.");
  66
  67         list_for_each_entry(tmp_devfreq, &devfreq_list, node) {
  68                 if (tmp_devfreq->dev.parent == dev)
  69                         return tmp_devfreq;
  70         }
  71
  72         return ERR_PTR(-ENODEV);
  73 }
  74
  75 /**
  76  * update_devfreq() - Reevaluate the device and configure frequency.
  77  * @devfreq:    the devfreq instance.
  78  *
  79  * Note: Lock devfreq->lock before calling update_devfreq
  80  *       This function is exported for governors.
  81  */
  82 int update_devfreq(struct devfreq *devfreq)
  83 {
  84         unsigned long freq;
  85         int err = 0;
  86
  87         if (!mutex_is_locked(&devfreq->lock)) {
  88                 WARN(true, "devfreq->lock must be locked by the caller.\n");
  89                 return -EINVAL;
  90         }
  91
  92         /* Reevaluate the proper frequency */
  93         err = devfreq->governor->get_target_freq(devfreq, &freq);
  94         if (err)
  95                 return err;
  96
  97         err = devfreq->profile->target(devfreq->dev.parent, &freq);
  98         if (err)
  99                 return err;
 100
 101         devfreq->previous_freq = freq;
 102         return err;
 103 }
 104
 105 /**
 106  * devfreq_notifier_call() - Notify that the device frequency requirements
 107  *                         has been changed out of devfreq framework.
 108  * @nb          the notifier_block (supposed to be devfreq->nb)
 109  * @type        not used
 110  * @devp        not used
 111  *
 112  * Called by a notifier that uses devfreq->nb.
 113  */
 114 static int devfreq_notifier_call(struct notifier_block *nb, unsigned long type,
 115                                  void *devp)
 116 {
 117         struct devfreq *devfreq = container_of(nb, struct devfreq, nb);
 118         int ret;
 119
 120         mutex_lock(&devfreq->lock);
 121         ret = update_devfreq(devfreq);
 122         mutex_unlock(&devfreq->lock);
 123
 124         return ret;
 125 }
 126
 127 /**
 128  * _remove_devfreq() - Remove devfreq from the device.
 129  * @devfreq:    the devfreq struct
 130  * @skip:       skip calling device_unregister().
 131  *
 132  * Note that the caller should lock devfreq->lock before calling
 133  * this. _remove_devfreq() will unlock it and free devfreq
 134  * internally. devfreq_list_lock should be locked by the caller
 135  * as well (not relased at return)
 136  *
 137  * Lock usage:
 138  * devfreq->lock: locked before call.
 139  *                unlocked at return (and freed)
 140  * devfreq_list_lock: locked before call.
 141  *                    kept locked at return.
 142  *                    if devfreq is centrally polled.
 143  *
 144  * Freed memory:
 145  * devfreq
 146  */
 147 static void _remove_devfreq(struct devfreq *devfreq, bool skip)
 148 {
 149         if (!mutex_is_locked(&devfreq->lock)) {
 150                 WARN(true, "devfreq->lock must be locked by the caller.\n");
 151                 return;
 152         }
 153         if (!devfreq->governor->no_central_polling &&
 154             !mutex_is_locked(&devfreq_list_lock)) {
 155                 WARN(true, "devfreq_list_lock must be locked by the caller.\n");
 156                 return;
 157         }
 158
 159         if (devfreq->being_removed)
 160                 return;
 161
 162         devfreq->being_removed = true;
 163
 164         if (devfreq->profile->exit)
 165                 devfreq->profile->exit(devfreq->dev.parent);
 166
 167         if (devfreq->governor->exit)
 168                 devfreq->governor->exit(devfreq);
 169
 170         if (!skip && get_device(&devfreq->dev)) {
 171                 device_unregister(&devfreq->dev);
 172                 put_device(&devfreq->dev);
 173         }
 174
 175         if (!devfreq->governor->no_central_polling)
 176                 list_del(&devfreq->node);
 177
 178         mutex_unlock(&devfreq->lock);
 179         mutex_destroy(&devfreq->lock);
 180
 181         kfree(devfreq);
 182 }
 183
 184 /**
 185  * devfreq_dev_release() - Callback for struct device to release the device.
 186  * @dev:        the devfreq device
 187  *
 188  * This calls _remove_devfreq() if _remove_devfreq() is not called.
 189  * Note that devfreq_dev_release() could be called by _remove_devfreq() as
 190  * well as by others unregistering the device.
 191  */
 192 static void devfreq_dev_release(struct device *dev)
 193 {
 194         struct devfreq *devfreq = to_devfreq(dev);
 195         bool central_polling = !devfreq->governor->no_central_polling;
 196
 197         /*
 198          * If devfreq_dev_release() was called by device_unregister() of
 199          * _remove_devfreq(), we cannot mutex_lock(&devfreq->lock) and
 200          * being_removed is already set. This also partially checks the case
 201          * where devfreq_dev_release() is called from a thread other than
 202          * the one called _remove_devfreq(); however, this case is
 203          * dealt completely with another following being_removed check.
 204          *
 205          * Because being_removed is never being
 206          * unset, we do not need to worry about race conditions on
 207          * being_removed.
 208          */
 209         if (devfreq->being_removed)
 210                 return;
 211
 212         if (central_polling)
 213                 mutex_lock(&devfreq_list_lock);
 214
 215         mutex_lock(&devfreq->lock);
 216
 217         /*
 218          * Check being_removed flag again for the case where
 219          * devfreq_dev_release() was called in a thread other than the one
 220          * possibly called _remove_devfreq().
 221          */
 222         if (devfreq->being_removed) {
 223                 mutex_unlock(&devfreq->lock);
 224                 goto out;
 225         }
 226
 227         /* devfreq->lock is unlocked and removed in _removed_devfreq() */
 228         _remove_devfreq(devfreq, true);
 229
 230 out:
 231         if (central_polling)
 232                 mutex_unlock(&devfreq_list_lock);
 233 }
 234
 235 /**
 236  * devfreq_monitor() - Periodically poll devfreq objects.
 237  * @work: the work struct used to run devfreq_monitor periodically.
 238  *
 239  */
 240 static void devfreq_monitor(struct work_struct *work)
 241 {
 242         static unsigned long last_polled_at;
 243         struct devfreq *devfreq, *tmp;
 244         int error;
 245         unsigned long jiffies_passed;
 246         unsigned long next_jiffies = ULONG_MAX, now = jiffies;
 247         struct device *dev;
 248
 249         /* Initially last_polled_at = 0, polling every device at bootup */
 250         jiffies_passed = now - last_polled_at;
 251         last_polled_at = now;
 252         if (jiffies_passed == 0)
 253                 jiffies_passed = 1;
 254
 255         mutex_lock(&devfreq_list_lock);
 256         list_for_each_entry_safe(devfreq, tmp, &devfreq_list, node) {
 257                 mutex_lock(&devfreq->lock);
 258                 dev = devfreq->dev.parent;
 259
 260                 /* Do not remove tmp for a while */
 261                 wait_remove_device = tmp;
 262
 263                 if (devfreq->governor->no_central_polling ||
 264                     devfreq->next_polling == 0) {
 265                         mutex_unlock(&devfreq->lock);
 266                         continue;
 267                 }
 268                 mutex_unlock(&devfreq_list_lock);
 269
 270                 /*
 271                  * Reduce more next_polling if devfreq_wq took an extra
 272                  * delay. (i.e., CPU has been idled.)
 273                  */
 274                 if (devfreq->next_polling <= jiffies_passed) {
 275                         error = update_devfreq(devfreq);
 276
 277                         /* Remove a devfreq with an error. */
 278                         if (error && error != -EAGAIN) {
 279
 280                                 dev_err(dev, "Due to update_devfreq error(%d), devfreq(%s) is removed from the device\n",
 281                                         error, devfreq->governor->name);
 282
 283                                 /*
 284                                  * Unlock devfreq before locking the list
 285                                  * in order to avoid deadlock with
 286                                  * find_device_devfreq or others
 287                                  */
 288                                 mutex_unlock(&devfreq->lock);
 289                                 mutex_lock(&devfreq_list_lock);
 290                                 /* Check if devfreq is already removed */
 291                                 if (IS_ERR(find_device_devfreq(dev)))
 292                                         continue;
 293                                 mutex_lock(&devfreq->lock);
 294                                 /* This unlocks devfreq->lock and free it */
 295                                 _remove_devfreq(devfreq, false);
 296                                 continue;
 297                         }
 298                         devfreq->next_polling = devfreq->polling_jiffies;
 299                 } else {
 300                         devfreq->next_polling -= jiffies_passed;
 301                 }
 302
 303                 if (devfreq->next_polling)
 304                         next_jiffies = (next_jiffies > devfreq->next_polling) ?
 305                                         devfreq->next_polling : next_jiffies;
 306
 307                 mutex_unlock(&devfreq->lock);
 308                 mutex_lock(&devfreq_list_lock);
 309         }
 310         wait_remove_device = NULL;
 311         mutex_unlock(&devfreq_list_lock);
 312
 313         if (next_jiffies > 0 && next_jiffies < ULONG_MAX) {
 314                 polling = true;
 315                 queue_delayed_work(devfreq_wq, &devfreq_work, next_jiffies);
 316         } else {
 317                 polling = false;
 318         }
 319 }
 320
 321 /**
 322  * devfreq_add_device() - Add devfreq feature to the device
 323  * @dev:        the device to add devfreq feature.
 324  * @profile:    device-specific profile to run devfreq.
 325  * @governor:   the policy to choose frequency.
 326  * @data:       private data for the governor. The devfreq framework does not
 327  *              touch this value.
 328  */
 329 struct devfreq *devfreq_add_device(struct device *dev,
 330                                    struct devfreq_dev_profile *profile,
 331                                    const struct devfreq_governor *governor,
 332                                    void *data)
 333 {
 334         struct devfreq *devfreq;
 335         int err = 0;
 336
 337         if (!dev || !profile || !governor) {
 338                 dev_err(dev, "%s: Invalid parameters.\n", __func__);
 339                 return ERR_PTR(-EINVAL);
 340         }
 341
 342
 343         if (!governor->no_central_polling) {
 344                 mutex_lock(&devfreq_list_lock);
 345                 devfreq = find_device_devfreq(dev);
 346                 mutex_unlock(&devfreq_list_lock);
 347                 if (!IS_ERR(devfreq)) {
 348                         dev_err(dev, "%s: Unable to create devfreq for the device. It already has one.\n", __func__);
 349                         err = -EINVAL;
 350                         goto err_out;
 351                 }
 352         }
 353
 354         devfreq = kzalloc(sizeof(struct devfreq), GFP_KERNEL);
 355         if (!devfreq) {
 356                 dev_err(dev, "%s: Unable to create devfreq for the device\n",
 357                         __func__);
 358                 err = -ENOMEM;
 359                 goto err_out;
 360         }
 361
 362         mutex_init(&devfreq->lock);
 363         mutex_lock(&devfreq->lock);
 364         devfreq->dev.parent = dev;
 365         devfreq->dev.class = devfreq_class;
 366         devfreq->dev.release = devfreq_dev_release;
 367         devfreq->profile = profile;
 368         devfreq->governor = governor;
 369         devfreq->previous_freq = profile->initial_freq;
 370         devfreq->data = data;
 371         devfreq->next_polling = devfreq->polling_jiffies
 372                               = msecs_to_jiffies(devfreq->profile->polling_ms);
 373         devfreq->nb.notifier_call = devfreq_notifier_call;
 374
 375         dev_set_name(&devfreq->dev, dev_name(dev));
 376         err = device_register(&devfreq->dev);
 377         if (err) {
 378                 put_device(&devfreq->dev);
 379                 goto err_dev;
 380         }
 381
 382         if (governor->init)
 383                 err = governor->init(devfreq);
 384         if (err)
 385                 goto err_init;
 386
 387         mutex_unlock(&devfreq->lock);
 388
 389         if (governor->no_central_polling)
 390                 goto out;
 391
 392         mutex_lock(&devfreq_list_lock);
 393
 394         list_add(&devfreq->node, &devfreq_list);
 395
 396         if (devfreq_wq && devfreq->next_polling && !polling) {
 397                 polling = true;
 398                 queue_delayed_work(devfreq_wq, &devfreq_work,
 399                                    devfreq->next_polling);
 400         }
 401         mutex_unlock(&devfreq_list_lock);
 402 out:
 403         return devfreq;
 404
 405 err_init:
 406         device_unregister(&devfreq->dev);
 407 err_dev:
 408         mutex_unlock(&devfreq->lock);
 409         kfree(devfreq);
 410 err_out:
 411         return ERR_PTR(err);
 412 }
 413
 414 /**
 415  * devfreq_remove_device() - Remove devfreq feature from a device.
 416  * @devfreq     the devfreq instance to be removed
 417  */
 418 int devfreq_remove_device(struct devfreq *devfreq)
 419 {
 420         bool central_polling;
 421
 422         if (!devfreq)
 423                 return -EINVAL;
 424
 425         central_polling = !devfreq->governor->no_central_polling;
 426
 427         if (central_polling) {
 428                 mutex_lock(&devfreq_list_lock);
 429                 while (wait_remove_device == devfreq) {
 430                         mutex_unlock(&devfreq_list_lock);
 431                         schedule();
 432                         mutex_lock(&devfreq_list_lock);
 433                 }
 434         }
 435
 436         mutex_lock(&devfreq->lock);
 437         _remove_devfreq(devfreq, false); /* it unlocks devfreq->lock */
 438
 439         if (central_polling)
 440                 mutex_unlock(&devfreq_list_lock);
 441
 442         return 0;
 443 }
 444
 445 static ssize_t show_governor(struct device *dev,
 446                              struct device_attribute *attr, char *buf)
 447 {
 448         return sprintf(buf, "%s\n", to_devfreq(dev)->governor->name);
 449 }
 450
 451 static ssize_t show_freq(struct device *dev,
 452                          struct device_attribute *attr, char *buf)
 453 {
 454         return sprintf(buf, "%lu\n", to_devfreq(dev)->previous_freq);
 455 }
 456
 457 static ssize_t show_polling_interval(struct device *dev,
 458                                      struct device_attribute *attr, char *buf)
 459 {
 460         return sprintf(buf, "%d\n", to_devfreq(dev)->profile->polling_ms);
 461 }
 462
 463 static ssize_t store_polling_interval(struct device *dev,
 464                                       struct device_attribute *attr,
 465                                       const char *buf, size_t count)
 466 {
 467         struct devfreq *df = to_devfreq(dev);
 468         unsigned int value;
 469         int ret;
 470
 471         ret = sscanf(buf, "%u", &value);
 472         if (ret != 1)
 473                 goto out;
 474
 475         mutex_lock(&df->lock);
 476         df->profile->polling_ms = value;
 477         df->next_polling = df->polling_jiffies
 478                          = msecs_to_jiffies(value);
 479         mutex_unlock(&df->lock);
 480
 481         ret = count;
 482
 483         if (df->governor->no_central_polling)
 484                 goto out;
 485
 486         mutex_lock(&devfreq_list_lock);
 487         if (df->next_polling > 0 && !polling) {
 488                 polling = true;
 489                 queue_delayed_work(devfreq_wq, &devfreq_work,
 490                                    df->next_polling);
 491         }
 492         mutex_unlock(&devfreq_list_lock);
 493 out:
 494         return ret;
 495 }
 496
 497 static ssize_t show_central_polling(struct device *dev,
 498                                     struct device_attribute *attr, char *buf)
 499 {
 500         return sprintf(buf, "%d\n",
 501                        !to_devfreq(dev)->governor->no_central_polling);
 502 }
 503
 504 static struct device_attribute devfreq_attrs[] = {
 505         __ATTR(governor, S_IRUGO, show_governor, NULL),
 506         __ATTR(cur_freq, S_IRUGO, show_freq, NULL),
 507         __ATTR(central_polling, S_IRUGO, show_central_polling, NULL),
 508         __ATTR(polling_interval, S_IRUGO | S_IWUSR, show_polling_interval,
 509                store_polling_interval),
 510         { },
 511 };
 512
 513 /**
 514  * devfreq_start_polling() - Initialize data structure for devfreq framework and
 515  *                         start polling registered devfreq devices.
 516  */
 517 static int __init devfreq_start_polling(void)
 518 {
 519         mutex_lock(&devfreq_list_lock);
 520         polling = false;
 521         devfreq_wq = create_freezable_workqueue("devfreq_wq");
 522         INIT_DELAYED_WORK_DEFERRABLE(&devfreq_work, devfreq_monitor);
 523         mutex_unlock(&devfreq_list_lock);
 524
 525         devfreq_monitor(&devfreq_work.work);
 526         return 0;
 527 }
 528 late_initcall(devfreq_start_polling);
 529
 530 static int __init devfreq_init(void)
 531 {
 532         devfreq_class = class_create(THIS_MODULE, "devfreq");
 533         if (IS_ERR(devfreq_class)) {
 534                 pr_err("%s: couldn't create class\n", __FILE__);
 535                 return PTR_ERR(devfreq_class);
 536         }
 537         devfreq_class->dev_attrs = devfreq_attrs;
 538         return 0;
 539 }
 540 subsys_initcall(devfreq_init);
 541
 542 static void __exit devfreq_exit(void)
 543 {
 544         class_destroy(devfreq_class);
 545 }
 546 module_exit(devfreq_exit);
 547
 548 /*
 549  * The followings are helper functions for devfreq user device drivers with
 550  * OPP framework.
 551  */
 552
 553 /**
 554  * devfreq_recommended_opp() - Helper function to get proper OPP for the
 555  *                           freq value given to target callback.
 556  * @dev         The devfreq user device. (parent of devfreq)
 557  * @freq        The frequency given to target function
 558  *
 559  */
 560 struct opp *devfreq_recommended_opp(struct device *dev, unsigned long *freq)
 561 {
 562         struct opp *opp = opp_find_freq_ceil(dev, freq);
 563
 564         if (opp == ERR_PTR(-ENODEV))
 565                 opp = opp_find_freq_floor(dev, freq);
 566         return opp;
 567 }
 568
 569 /**
 570  * devfreq_register_opp_notifier() - Helper function to get devfreq notified
 571  *                                 for any changes in the OPP availability
 572  *                                 changes
 573  * @dev         The devfreq user device. (parent of devfreq)
 574  * @devfreq     The devfreq object.
 575  */
 576 int devfreq_register_opp_notifier(struct device *dev, struct devfreq *devfreq)
 577 {
 578         struct srcu_notifier_head *nh = opp_get_notifier(dev);
 579
 580         if (IS_ERR(nh))
 581                 return PTR_ERR(nh);
 582         return srcu_notifier_chain_register(nh, &devfreq->nb);
 583 }
 584
 585 /**
 586  * devfreq_unregister_opp_notifier() - Helper function to stop getting devfreq
 587  *                                   notified for any changes in the OPP
 588  *                                   availability changes anymore.
 589  * @dev         The devfreq user device. (parent of devfreq)
 590  * @devfreq     The devfreq object.
 591  *
 592  * At exit() callback of devfreq_dev_profile, this must be included if
 593  * devfreq_recommended_opp is used.
 594  */
 595 int devfreq_unregister_opp_notifier(struct device *dev, struct devfreq *devfreq)
 596 {
 597         struct srcu_notifier_head *nh = opp_get_notifier(dev);
 598
 599         if (IS_ERR(nh))
 600                 return PTR_ERR(nh);
 601         return srcu_notifier_chain_unregister(nh, &devfreq->nb);
 602 }
 603
 604 MODULE_AUTHOR("MyungJoo Ham <myungjoo.ham@samsung.com>");
 605 MODULE_DESCRIPTION("devfreq class support");
 606 MODULE_LICENSE("GPL");