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        }
 143}
 144
 145s32 pm_qos_read_value(struct pm_qos_constraints *c)
 146{
 147        return c->target_value;
 148}
 149
 150static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
 151{
 152        c->target_value = value;
 153}
 154
 155/**
 156 * pm_qos_update_target - manages the constraints list and calls the notifiers
 157 *  if needed
 158 * @c: constraints data struct
 159 * @node: request to add to the list, to update or to remove
 160 * @action: action to take on the constraints list
 161 * @value: value of the request to add or update
 162 *
 163 * This function returns 1 if the aggregated constraint value has changed, 0
 164 *  otherwise.
 165 */
 166int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
 167                         enum pm_qos_req_action action, int value)
 168{
 169        unsigned long flags;
 170        int prev_value, curr_value, new_value;
 171
 172        spin_lock_irqsave(&pm_qos_lock, flags);
 173        prev_value = pm_qos_get_value(c);
 174        if (value == PM_QOS_DEFAULT_VALUE)
 175                new_value = c->default_value;
 176        else
 177                new_value = value;
 178
 179        switch (action) {
 180        case PM_QOS_REMOVE_REQ:
 181                plist_del(node, &c->list);
 182                break;
 183        case PM_QOS_UPDATE_REQ:
 184                /*
 185                 * to change the list, we atomically remove, reinit
 186                 * with new value and add, then see if the extremal
 187                 * changed
 188                 */
 189                plist_del(node, &c->list);
 190        case PM_QOS_ADD_REQ:
 191                plist_node_init(node, new_value);
 192                plist_add(node, &c->list);
 193                break;
 194        default:
 195                /* no action */
 196                ;
 197        }
 198
 199        curr_value = pm_qos_get_value(c);
 200        pm_qos_set_value(c, curr_value);
 201
 202        spin_unlock_irqrestore(&pm_qos_lock, flags);
 203
 204        if (prev_value != curr_value) {
 205                blocking_notifier_call_chain(c->notifiers,
 206                                             (unsigned long)curr_value,
 207                                             NULL);
 208                return 1;
 209        } else {
 210                return 0;
 211        }
 212}
 213
 214/**
 215 * pm_qos_request - returns current system wide qos expectation
 216 * @pm_qos_class: identification of which qos value is requested
 217 *
 218 * This function returns the current target value.
 219 */
 220int pm_qos_request(int pm_qos_class)
 221{
 222        return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
 223}
 224EXPORT_SYMBOL_GPL(pm_qos_request);
 225
 226int pm_qos_request_active(struct pm_qos_request *req)
 227{
 228        return req->pm_qos_class != 0;
 229}
 230EXPORT_SYMBOL_GPL(pm_qos_request_active);
 231
 232/**
 233 * pm_qos_work_fn - the timeout handler of pm_qos_update_request_timeout
 234 * @work: work struct for the delayed work (timeout)
 235 *
 236 * This cancels the timeout request by falling back to the default at timeout.
 237 */
 238static void pm_qos_work_fn(struct work_struct *work)
 239{
 240        struct pm_qos_request *req = container_of(to_delayed_work(work),
 241                                                  struct pm_qos_request,
 242                                                  work);
 243
 244        pm_qos_update_request(req, PM_QOS_DEFAULT_VALUE);
 245}
 246
 247/**
 248 * pm_qos_add_request - inserts new qos request into the list
 249 * @req: pointer to a preallocated handle
 250 * @pm_qos_class: identifies which list of qos request to use
 251 * @value: defines the qos request
 252 *
 253 * This function inserts a new entry in the pm_qos_class list of requested qos
 254 * performance characteristics.  It recomputes the aggregate QoS expectations
 255 * for the pm_qos_class of parameters and initializes the pm_qos_request
 256 * handle.  Caller needs to save this handle for later use in updates and
 257 * removal.
 258 */
 259
 260void pm_qos_add_request(struct pm_qos_request *req,
 261                        int pm_qos_class, s32 value)
 262{
 263        if (!req) /*guard against callers passing in null */
 264                return;
 265
 266        if (pm_qos_request_active(req)) {
 267                WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 268                return;
 269        }
 270        req->pm_qos_class = pm_qos_class;
 271        INIT_DELAYED_WORK(&req->work, pm_qos_work_fn);
 272        pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
 273                             &req->node, PM_QOS_ADD_REQ, value);
 274}
 275EXPORT_SYMBOL_GPL(pm_qos_add_request);
 276
 277/**
 278 * pm_qos_update_request - modifies an existing qos request
 279 * @req : handle to list element holding a pm_qos request to use
 280 * @value: defines the qos request
 281 *
 282 * Updates an existing qos request for the pm_qos_class of parameters along
 283 * with updating the target pm_qos_class value.
 284 *
 285 * Attempts are made to make this code callable on hot code paths.
 286 */
 287void pm_qos_update_request(struct pm_qos_request *req,
 288                           s32 new_value)
 289{
 290        if (!req) /*guard against callers passing in null */
 291                return;
 292
 293        if (!pm_qos_request_active(req)) {
 294                WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 295                return;
 296        }
 297
 298        if (delayed_work_pending(&req->work))
 299                cancel_delayed_work_sync(&req->work);
 300
 301        if (new_value != req->node.prio)
 302                pm_qos_update_target(
 303                        pm_qos_array[req->pm_qos_class]->constraints,
 304                        &req->node, PM_QOS_UPDATE_REQ, new_value);
 305}
 306EXPORT_SYMBOL_GPL(pm_qos_update_request);
 307
 308/**
 309 * pm_qos_update_request_timeout - modifies an existing qos request temporarily.
 310 * @req : handle to list element holding a pm_qos request to use
 311 * @new_value: defines the temporal qos request
 312 * @timeout_us: the effective duration of this qos request in usecs.
 313 *
 314 * After timeout_us, this qos request is cancelled automatically.
 315 */
 316void pm_qos_update_request_timeout(struct pm_qos_request *req, s32 new_value,
 317                                   unsigned long timeout_us)
 318{
 319        if (!req)
 320                return;
 321        if (WARN(!pm_qos_request_active(req),
 322                 "%s called for unknown object.", __func__))
 323                return;
 324
 325        if (delayed_work_pending(&req->work))
 326                cancel_delayed_work_sync(&req->work);
 327
 328        if (new_value != req->node.prio)
 329                pm_qos_update_target(
 330                        pm_qos_array[req->pm_qos_class]->constraints,
 331                        &req->node, PM_QOS_UPDATE_REQ, new_value);
 332
 333        schedule_delayed_work(&req->work, usecs_to_jiffies(timeout_us));
 334}
 335
 336/**
 337 * pm_qos_remove_request - modifies an existing qos request
 338 * @req: handle to request list element
 339 *
 340 * Will remove pm qos request from the list of constraints and
 341 * recompute the current target value for the pm_qos_class.  Call this
 342 * on slow code paths.
 343 */
 344void pm_qos_remove_request(struct pm_qos_request *req)
 345{
 346        if (!req) /*guard against callers passing in null */
 347                return;
 348                /* silent return to keep pcm code cleaner */
 349
 350        if (!pm_qos_request_active(req)) {
 351                WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 352                return;
 353        }
 354
 355        if (delayed_work_pending(&req->work))
 356                cancel_delayed_work_sync(&req->work);
 357
 358        pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
 359                             &req->node, PM_QOS_REMOVE_REQ,
 360                             PM_QOS_DEFAULT_VALUE);
 361        memset(req, 0, sizeof(*req));
 362}
 363EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 364
 365/**
 366 * pm_qos_add_notifier - sets notification entry for changes to target value
 367 * @pm_qos_class: identifies which qos target changes should be notified.
 368 * @notifier: notifier block managed by caller.
 369 *
 370 * will register the notifier into a notification chain that gets called
 371 * upon changes to the pm_qos_class target value.
 372 */
 373int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 374{
 375        int retval;
 376
 377        retval = blocking_notifier_chain_register(
 378                        pm_qos_array[pm_qos_class]->constraints->notifiers,
 379                        notifier);
 380
 381        return retval;
 382}
 383EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 384
 385/**
 386 * pm_qos_remove_notifier - deletes notification entry from chain.
 387 * @pm_qos_class: identifies which qos target changes are notified.
 388 * @notifier: notifier block to be removed.
 389 *
 390 * will remove the notifier from the notification chain that gets called
 391 * upon changes to the pm_qos_class target value.
 392 */
 393int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 394{
 395        int retval;
 396
 397        retval = blocking_notifier_chain_unregister(
 398                        pm_qos_array[pm_qos_class]->constraints->notifiers,
 399                        notifier);
 400
 401        return retval;
 402}
 403EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 404
 405/* User space interface to PM QoS classes via misc devices */
 406static int register_pm_qos_misc(struct pm_qos_object *qos)
 407{
 408        qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 409        qos->pm_qos_power_miscdev.name = qos->name;
 410        qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 411
 412        return misc_register(&qos->pm_qos_power_miscdev);
 413}
 414
 415static int find_pm_qos_object_by_minor(int minor)
 416{
 417        int pm_qos_class;
 418
 419        for (pm_qos_class = 0;
 420                pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 421                if (minor ==
 422                        pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 423                        return pm_qos_class;
 424        }
 425        return -1;
 426}
 427
 428static int pm_qos_power_open(struct inode *inode, struct file *filp)
 429{
 430        long pm_qos_class;
 431
 432        pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 433        if (pm_qos_class >= 0) {
 434                struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
 435                if (!req)
 436                        return -ENOMEM;
 437
 438                pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 439                filp->private_data = req;
 440
 441                return 0;
 442        }
 443        return -EPERM;
 444}
 445
 446static int pm_qos_power_release(struct inode *inode, struct file *filp)
 447{
 448        struct pm_qos_request *req;
 449
 450        req = filp->private_data;
 451        pm_qos_remove_request(req);
 452        kfree(req);
 453
 454        return 0;
 455}
 456
 457
 458static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 459                size_t count, loff_t *f_pos)
 460{
 461        s32 value;
 462        unsigned long flags;
 463        struct pm_qos_request *req = filp->private_data;
 464
 465        if (!req)
 466                return -EINVAL;
 467        if (!pm_qos_request_active(req))
 468                return -EINVAL;
 469
 470        spin_lock_irqsave(&pm_qos_lock, flags);
 471        value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
 472        spin_unlock_irqrestore(&pm_qos_lock, flags);
 473
 474        return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 475}
 476
 477static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 478                size_t count, loff_t *f_pos)
 479{
 480        s32 value;
 481        struct pm_qos_request *req;
 482
 483        if (count == sizeof(s32)) {
 484                if (copy_from_user(&value, buf, sizeof(s32)))
 485                        return -EFAULT;
 486        } else if (count <= 11) { /* ASCII perhaps? */
 487                char ascii_value[11];
 488                unsigned long int ulval;
 489                int ret;
 490
 491                if (copy_from_user(ascii_value, buf, count))
 492                        return -EFAULT;
 493
 494                if (count > 10) {
 495                        if (ascii_value[10] == '\n')
 496                                ascii_value[10] = '\0';
 497                        else
 498                                return -EINVAL;
 499                } else {
 500                        ascii_value[count] = '\0';
 501                }
 502                ret = strict_strtoul(ascii_value, 16, &ulval);
 503                if (ret) {
 504                        pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 505                        return -EINVAL;
 506                }
 507                value = (s32)lower_32_bits(ulval);
 508        } else {
 509                return -EINVAL;
 510        }
 511
 512        req = filp->private_data;
 513        pm_qos_update_request(req, value);
 514
 515        return count;
 516}
 517
 518
 519static int __init pm_qos_power_init(void)
 520{
 521        int ret = 0;
 522        int i;
 523
 524        BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES);
 525
 526        for (i = 1; i < PM_QOS_NUM_CLASSES; i++) {
 527                ret = register_pm_qos_misc(pm_qos_array[i]);
 528                if (ret < 0) {
 529                        printk(KERN_ERR "pm_qos_param: %s setup failed\n",
 530                               pm_qos_array[i]->name);
 531                        return ret;
 532                }
 533        }
 534
 535        return ret;
 536}
 537
 538late_initcall(pm_qos_power_init);
 539
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