linux/kernel/power/qos.c
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   1/*
   2 * This module exposes the interface to kernel space for specifying
   3 * QoS dependencies.  It provides infrastructure for registration of:
   4 *
   5 * Dependents on a QoS value : register requests
   6 * Watchers of QoS value : get notified when target QoS value changes
   7 *
   8 * This QoS design is best effort based.  Dependents register their QoS needs.
   9 * Watchers register to keep track of the current QoS needs of the system.
  10 *
  11 * There are 3 basic classes of QoS parameter: latency, timeout, throughput
  12 * each have defined units:
  13 * latency: usec
  14 * timeout: usec <-- currently not used.
  15 * throughput: kbs (kilo byte / sec)
  16 *
  17 * There are lists of pm_qos_objects each one wrapping requests, notifiers
  18 *
  19 * User mode requests on a QOS parameter register themselves to the
  20 * subsystem by opening the device node /dev/... and writing there request to
  21 * the node.  As long as the process holds a file handle open to the node the
  22 * client continues to be accounted for.  Upon file release the usermode
  23 * request is removed and a new qos target is computed.  This way when the
  24 * request that the application has is cleaned up when closes the file
  25 * pointer or exits the pm_qos_object will get an opportunity to clean up.
  26 *
  27 * Mark Gross <mgross@linux.intel.com>
  28 */
  29
  30/*#define DEBUG*/
  31
  32#include <linux/pm_qos.h>
  33#include <linux/sched.h>
  34#include <linux/spinlock.h>
  35#include <linux/slab.h>
  36#include <linux/time.h>
  37#include <linux/fs.h>
  38#include <linux/device.h>
  39#include <linux/miscdevice.h>
  40#include <linux/string.h>
  41#include <linux/platform_device.h>
  42#include <linux/init.h>
  43#include <linux/kernel.h>
  44
  45#include <linux/uaccess.h>
  46#include <linux/export.h>
  47
  48/*
  49 * locking rule: all changes to constraints or notifiers lists
  50 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
  51 * held, taken with _irqsave.  One lock to rule them all
  52 */
  53struct pm_qos_object {
  54        struct pm_qos_constraints *constraints;
  55        struct miscdevice pm_qos_power_miscdev;
  56        char *name;
  57};
  58
  59static DEFINE_SPINLOCK(pm_qos_lock);
  60
  61static struct pm_qos_object null_pm_qos;
  62
  63static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  64static struct pm_qos_constraints cpu_dma_constraints = {
  65        .list = PLIST_HEAD_INIT(cpu_dma_constraints.list),
  66        .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  67        .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  68        .type = PM_QOS_MIN,
  69        .notifiers = &cpu_dma_lat_notifier,
  70};
  71static struct pm_qos_object cpu_dma_pm_qos = {
  72        .constraints = &cpu_dma_constraints,
  73        .name = "cpu_dma_latency",
  74};
  75
  76static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  77static struct pm_qos_constraints network_lat_constraints = {
  78        .list = PLIST_HEAD_INIT(network_lat_constraints.list),
  79        .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  80        .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  81        .type = PM_QOS_MIN,
  82        .notifiers = &network_lat_notifier,
  83};
  84static struct pm_qos_object network_lat_pm_qos = {
  85        .constraints = &network_lat_constraints,
  86        .name = "network_latency",
  87};
  88
  89
  90static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  91static struct pm_qos_constraints network_tput_constraints = {
  92        .list = PLIST_HEAD_INIT(network_tput_constraints.list),
  93        .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
  94        .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
  95        .type = PM_QOS_MAX,
  96        .notifiers = &network_throughput_notifier,
  97};
  98static struct pm_qos_object network_throughput_pm_qos = {
  99        .constraints = &network_tput_constraints,
 100        .name = "network_throughput",
 101};
 102
 103
 104static struct pm_qos_object *pm_qos_array[] = {
 105        &null_pm_qos,
 106        &cpu_dma_pm_qos,
 107        &network_lat_pm_qos,
 108        &network_throughput_pm_qos
 109};
 110
 111static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 112                size_t count, loff_t *f_pos);
 113static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 114                size_t count, loff_t *f_pos);
 115static int pm_qos_power_open(struct inode *inode, struct file *filp);
 116static int pm_qos_power_release(struct inode *inode, struct file *filp);
 117
 118static const struct file_operations pm_qos_power_fops = {
 119        .write = pm_qos_power_write,
 120        .read = pm_qos_power_read,
 121        .open = pm_qos_power_open,
 122        .release = pm_qos_power_release,
 123        .llseek = noop_llseek,
 124};
 125
 126/* unlocked internal variant */
 127static inline int pm_qos_get_value(struct pm_qos_constraints *c)
 128{
 129        if (plist_head_empty(&c->list))
 130                return c->default_value;
 131
 132        switch (c->type) {
 133        case PM_QOS_MIN:
 134                return plist_first(&c->list)->prio;
 135
 136        case PM_QOS_MAX:
 137                return plist_last(&c->list)->prio;
 138
 139        default:
 140                /* runtime check for not using enum */
 141                BUG();
 142                return PM_QOS_DEFAULT_VALUE;
 143        }
 144}
 145
 146s32 pm_qos_read_value(struct pm_qos_constraints *c)
 147{
 148        return c->target_value;
 149}
 150
 151static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
 152{
 153        c->target_value = value;
 154}
 155
 156/**
 157 * pm_qos_update_target - manages the constraints list and calls the notifiers
 158 *  if needed
 159 * @c: constraints data struct
 160 * @node: request to add to the list, to update or to remove
 161 * @action: action to take on the constraints list
 162 * @value: value of the request to add or update
 163 *
 164 * This function returns 1 if the aggregated constraint value has changed, 0
 165 *  otherwise.
 166 */
 167int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
 168                         enum pm_qos_req_action action, int value)
 169{
 170        unsigned long flags;
 171        int prev_value, curr_value, new_value;
 172
 173        spin_lock_irqsave(&pm_qos_lock, flags);
 174        prev_value = pm_qos_get_value(c);
 175        if (value == PM_QOS_DEFAULT_VALUE)
 176                new_value = c->default_value;
 177        else
 178                new_value = value;
 179
 180        switch (action) {
 181        case PM_QOS_REMOVE_REQ:
 182                plist_del(node, &c->list);
 183                break;
 184        case PM_QOS_UPDATE_REQ:
 185                /*
 186                 * to change the list, we atomically remove, reinit
 187                 * with new value and add, then see if the extremal
 188                 * changed
 189                 */
 190                plist_del(node, &c->list);
 191        case PM_QOS_ADD_REQ:
 192                plist_node_init(node, new_value);
 193                plist_add(node, &c->list);
 194                break;
 195        default:
 196                /* no action */
 197                ;
 198        }
 199
 200        curr_value = pm_qos_get_value(c);
 201        pm_qos_set_value(c, curr_value);
 202
 203        spin_unlock_irqrestore(&pm_qos_lock, flags);
 204
 205        if (prev_value != curr_value) {
 206                blocking_notifier_call_chain(c->notifiers,
 207                                             (unsigned long)curr_value,
 208                                             NULL);
 209                return 1;
 210        } else {
 211                return 0;
 212        }
 213}
 214
 215/**
 216 * pm_qos_request - returns current system wide qos expectation
 217 * @pm_qos_class: identification of which qos value is requested
 218 *
 219 * This function returns the current target value.
 220 */
 221int pm_qos_request(int pm_qos_class)
 222{
 223        return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
 224}
 225EXPORT_SYMBOL_GPL(pm_qos_request);
 226
 227int pm_qos_request_active(struct pm_qos_request *req)
 228{
 229        return req->pm_qos_class != 0;
 230}
 231EXPORT_SYMBOL_GPL(pm_qos_request_active);
 232
 233/**
 234 * pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
 235 * @work: work struct for the delayed work (timeout)
 236 *
 237 * This cancels the timeout request by falling back to the default at timeout.
 238 */
 239static void pm_qos_work_fn(struct work_struct *work)
 240{
 241        struct pm_qos_request *req = container_of(to_delayed_work(work),
 242                                                  struct pm_qos_request,
 243                                                  work);
 244
 245        pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
 246}
 247
 248/**
 249 * pm_qos_add_request - inserts new qos request into the list
 250 * @req: pointer to a preallocated handle
 251 * @pm_qos_class: identifies which list of qos request to use
 252 * @value: defines the qos request
 253 *
 254 * This function inserts a new entry in the pm_qos_class list of requested qos
 255 * performance characteristics.  It recomputes the aggregate QoS expectations
 256 * for the pm_qos_class of parameters and initializes the pm_qos_request
 257 * handle.  Caller needs to save this handle for later use in updates and
 258 * removal.
 259 */
 260
 261void pm_qos_add_request(struct pm_qos_request *req,
 262                        int pm_qos_class, s32 value)
 263{
 264        if (!req) /*guard against callers passing in null */
 265                return;
 266
 267        if (pm_qos_request_active(req)) {
 268                WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 269                return;
 270        }
 271        req->pm_qos_class = pm_qos_class;
 272        INIT_DELAYED_WORK(&req->work, pm_qos_work_fn);
 273        pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
 274                             &req->node, PM_QOS_ADD_REQ, value);
 275}
 276EXPORT_SYMBOL_GPL(pm_qos_add_request);
 277
 278/**
 279 * pm_qos_update_request - modifies an existing qos request
 280 * @req : handle to list element holding a pm_qos request to use
 281 * @value: defines the qos request
 282 *
 283 * Updates an existing qos request for the pm_qos_class of parameters along
 284 * with updating the target pm_qos_class value.
 285 *
 286 * Attempts are made to make this code callable on hot code paths.
 287 */
 288void pm_qos_update_request(struct pm_qos_request *req,
 289                           s32 new_value)
 290{
 291        if (!req) /*guard against callers passing in null */
 292                return;
 293
 294        if (!pm_qos_request_active(req)) {
 295                WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 296                return;
 297        }
 298
 299        if (delayed_work_pending(&req->work))
 300                cancel_delayed_work_sync(&req->work);
 301
 302        if (new_value != req->node.prio)
 303                pm_qos_update_target(
 304                        pm_qos_array[req->pm_qos_class]->constraints,
 305                        &req->node, PM_QOS_UPDATE_REQ, new_value);
 306}
 307EXPORT_SYMBOL_GPL(pm_qos_update_request);
 308
 309/**
 310 * pm_qos_update_request_timeout - modifies an existing qos request temporarily.
 311 * @req : handle to list element holding a pm_qos request to use
 312 * @new_value: defines the temporal qos request
 313 * @timeout_us: the effective duration of this qos request in usecs.
 314 *
 315 * After timeout_us, this qos request is cancelled automatically.
 316 */
 317void pm_qos_update_request_timeout(struct pm_qos_request *req, s32 new_value,
 318                                   unsigned long timeout_us)
 319{
 320        if (!req)
 321                return;
 322        if (WARN(!pm_qos_request_active(req),
 323                 "%s called for unknown object.", __func__))
 324                return;
 325
 326        if (delayed_work_pending(&req->work))
 327                cancel_delayed_work_sync(&req->work);
 328
 329        if (new_value != req->node.prio)
 330                pm_qos_update_target(
 331                        pm_qos_array[req->pm_qos_class]->constraints,
 332                        &req->node, PM_QOS_UPDATE_REQ, new_value);
 333
 334        schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
 335}
 336
 337/**
 338 * pm_qos_remove_request - modifies an existing qos request
 339 * @req: handle to request list element
 340 *
 341 * Will remove pm qos request from the list of constraints and
 342 * recompute the current target value for the pm_qos_class.  Call this
 343 * on slow code paths.
 344 */
 345void pm_qos_remove_request(struct pm_qos_request *req)
 346{
 347        if (!req) /*guard against callers passing in null */
 348                return;
 349                /* silent return to keep pcm code cleaner */
 350
 351        if (!pm_qos_request_active(req)) {
 352                WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 353                return;
 354        }
 355
 356        if (delayed_work_pending(&req->work))
 357                cancel_delayed_work_sync(&req->work);
 358
 359        pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
 360                             &req->node, PM_QOS_REMOVE_REQ,
 361                             PM_QOS_DEFAULT_VALUE);
 362        memset(req, 0, sizeof(*req));
 363}
 364EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 365
 366/**
 367 * pm_qos_add_notifier - sets notification entry for changes to target value
 368 * @pm_qos_class: identifies which qos target changes should be notified.
 369 * @notifier: notifier block managed by caller.
 370 *
 371 * will register the notifier into a notification chain that gets called
 372 * upon changes to the pm_qos_class target value.
 373 */
 374int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 375{
 376        int retval;
 377
 378        retval = blocking_notifier_chain_register(
 379                        pm_qos_array[pm_qos_class]->constraints->notifiers,
 380                        notifier);
 381
 382        return retval;
 383}
 384EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 385
 386/**
 387 * pm_qos_remove_notifier - deletes notification entry from chain.
 388 * @pm_qos_class: identifies which qos target changes are notified.
 389 * @notifier: notifier block to be removed.
 390 *
 391 * will remove the notifier from the notification chain that gets called
 392 * upon changes to the pm_qos_class target value.
 393 */
 394int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 395{
 396        int retval;
 397
 398        retval = blocking_notifier_chain_unregister(
 399                        pm_qos_array[pm_qos_class]->constraints->notifiers,
 400                        notifier);
 401
 402        return retval;
 403}
 404EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 405
 406/* User space interface to PM QoS classes via misc devices */
 407static int register_pm_qos_misc(struct pm_qos_object *qos)
 408{
 409        qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 410        qos->pm_qos_power_miscdev.name = qos->name;
 411        qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 412
 413        return misc_register(&qos->pm_qos_power_miscdev);
 414}
 415
 416static int find_pm_qos_object_by_minor(int minor)
 417{
 418        int pm_qos_class;
 419
 420        for (pm_qos_class = 0;
 421                pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 422                if (minor ==
 423                        pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 424                        return pm_qos_class;
 425        }
 426        return -1;
 427}
 428
 429static int pm_qos_power_open(struct inode *inode, struct file *filp)
 430{
 431        long pm_qos_class;
 432
 433        pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 434        if (pm_qos_class >= 0) {
 435                struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
 436                if (!req)
 437                        return -ENOMEM;
 438
 439                pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 440                filp->private_data = req;
 441
 442                return 0;
 443        }
 444        return -EPERM;
 445}
 446
 447static int pm_qos_power_release(struct inode *inode, struct file *filp)
 448{
 449        struct pm_qos_request *req;
 450
 451        req = filp->private_data;
 452        pm_qos_remove_request(req);
 453        kfree(req);
 454
 455        return 0;
 456}
 457
 458
 459static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 460                size_t count, loff_t *f_pos)
 461{
 462        s32 value;
 463        unsigned long flags;
 464        struct pm_qos_request *req = filp->private_data;
 465
 466        if (!req)
 467                return -EINVAL;
 468        if (!pm_qos_request_active(req))
 469                return -EINVAL;
 470
 471        spin_lock_irqsave(&pm_qos_lock, flags);
 472        value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
 473        spin_unlock_irqrestore(&pm_qos_lock, flags);
 474
 475        return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 476}
 477
 478static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 479                size_t count, loff_t *f_pos)
 480{
 481        s32 value;
 482        struct pm_qos_request *req;
 483
 484        if (count == sizeof(s32)) {
 485                if (copy_from_user(&value, buf, sizeof(s32)))
 486                        return -EFAULT;
 487        } else if (count <= 11) { /* ASCII perhaps? */
 488                char ascii_value[11];
 489                unsigned long int ulval;
 490                int ret;
 491
 492                if (copy_from_user(ascii_value, buf, count))
 493                        return -EFAULT;
 494
 495                if (count > 10) {
 496                        if (ascii_value[10] == '\n')
 497                                ascii_value[10] = '\0';
 498                        else
 499                                return -EINVAL;
 500                } else {
 501                        ascii_value[count] = '\0';
 502                }
 503                ret = strict_strtoul(ascii_value, 16, &ulval);
 504                if (ret) {
 505                        pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 506                        return -EINVAL;
 507                }
 508                value = (s32)lower_32_bits(ulval);
 509        } else {
 510                return -EINVAL;
 511        }
 512
 513        req = filp->private_data;
 514        pm_qos_update_request(req, value);
 515
 516        return count;
 517}
 518
 519
 520static int __init pm_qos_power_init(void)
 521{
 522        int ret = 0;
 523        int i;
 524
 525        BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES);
 526
 527        for (i = 1; i < PM_QOS_NUM_CLASSES; i++) {
 528                ret = register_pm_qos_misc(pm_qos_array[i]);
 529                if (ret < 0) {
 530                        printk(KERN_ERR "pm_qos_param: %s setup failed\n",
 531                               pm_qos_array[i]->name);
 532                        return ret;
 533                }
 534        }
 535
 536        return ret;
 537}
 538
 539late_initcall(pm_qos_power_init);
 540
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