drivers/base/power/qos.c

   1 /*
   2  * Devices PM QoS constraints management
   3  *
   4  * Copyright (C) 2011 Texas Instruments, Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *
  11  * This module exposes the interface to kernel space for specifying
  12  * per-device PM QoS dependencies. It provides infrastructure for registration
  13  * of:
  14  *
  15  * Dependents on a QoS value : register requests
  16  * Watchers of QoS value : get notified when target QoS value changes
  17  *
  18  * This QoS design is best effort based. Dependents register their QoS needs.
  19  * Watchers register to keep track of the current QoS needs of the system.
  20  * Watchers can register different types of notification callbacks:
  21  *  . a per-device notification callback using the dev_pm_qos_*_notifier API.
  22  *    The notification chain data is stored in the per-device constraint
  23  *    data struct.
  24  *  . a system-wide notification callback using the dev_pm_qos_*_global_notifier
  25  *    API. The notification chain data is stored in a static variable.
  26  *
  27  * Note about the per-device constraint data struct allocation:
  28  * . The per-device constraints data struct ptr is tored into the device
  29  *    dev_pm_info.
  30  * . To minimize the data usage by the per-device constraints, the data struct
  31  *   is only allocated at the first call to dev_pm_qos_add_request.
  32  * . The data is later free'd when the device is removed from the system.
  33  *  . A global mutex protects the constraints users from the data being
  34  *     allocated and free'd.
  35  */
  36
  37 #include <linux/pm_qos.h>
  38 #include <linux/spinlock.h>
  39 #include <linux/slab.h>
  40 #include <linux/device.h>
  41 #include <linux/mutex.h>
  42 #include <linux/export.h>
  43
  44
  45 static DEFINE_MUTEX(dev_pm_qos_mtx);
  46
  47 static BLOCKING_NOTIFIER_HEAD(dev_pm_notifiers);
  48
  49 /**
  50  * dev_pm_qos_read_value - Get PM QoS constraint for a given device.
  51  * @dev: Device to get the PM QoS constraint value for.
  52  */
  53 s32 dev_pm_qos_read_value(struct device *dev)
  54 {
  55         struct pm_qos_constraints *c;
  56         unsigned long flags;
  57         s32 ret = 0;
  58
  59         spin_lock_irqsave(&dev->power.lock, flags);
  60
  61         c = dev->power.constraints;
  62         if (c)
  63                 ret = pm_qos_read_value(c);
  64
  65         spin_unlock_irqrestore(&dev->power.lock, flags);
  66
  67         return ret;
  68 }
  69
  70 /*
  71  * apply_constraint
  72  * @req: constraint request to apply
  73  * @action: action to perform add/update/remove, of type enum pm_qos_req_action
  74  * @value: defines the qos request
  75  *
  76  * Internal function to update the constraints list using the PM QoS core
  77  * code and if needed call the per-device and the global notification
  78  * callbacks
  79  */
  80 static int apply_constraint(struct dev_pm_qos_request *req,
  81                             enum pm_qos_req_action action, int value)
  82 {
  83         int ret, curr_value;
  84
  85         ret = pm_qos_update_target(req->dev->power.constraints,
  86                                    &req->node, action, value);
  87
  88         if (ret) {
  89                 /* Call the global callbacks if needed */
  90                 curr_value = pm_qos_read_value(req->dev->power.constraints);
  91                 blocking_notifier_call_chain(&dev_pm_notifiers,
  92                                              (unsigned long)curr_value,
  93                                              req);
  94         }
  95
  96         return ret;
  97 }
  98
  99 /*
 100  * dev_pm_qos_constraints_allocate
 101  * @dev: device to allocate data for
 102  *
 103  * Called at the first call to add_request, for constraint data allocation
 104  * Must be called with the dev_pm_qos_mtx mutex held
 105  */
 106 static int dev_pm_qos_constraints_allocate(struct device *dev)
 107 {
 108         struct pm_qos_constraints *c;
 109         struct blocking_notifier_head *n;
 110
 111         c = kzalloc(sizeof(*c), GFP_KERNEL);
 112         if (!c)
 113                 return -ENOMEM;
 114
 115         n = kzalloc(sizeof(*n), GFP_KERNEL);
 116         if (!n) {
 117                 kfree(c);
 118                 return -ENOMEM;
 119         }
 120         BLOCKING_INIT_NOTIFIER_HEAD(n);
 121
 122         plist_head_init(&c->list);
 123         c->target_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
 124         c->default_value = PM_QOS_DEV_LAT_DEFAULT_VALUE;
 125         c->type = PM_QOS_MIN;
 126         c->notifiers = n;
 127
 128         spin_lock_irq(&dev->power.lock);
 129         dev->power.constraints = c;
 130         spin_unlock_irq(&dev->power.lock);
 131
 132         return 0;
 133 }
 134
 135 /**
 136  * dev_pm_qos_constraints_init - Initalize device's PM QoS constraints pointer.
 137  * @dev: target device
 138  *
 139  * Called from the device PM subsystem during device insertion under
 140  * device_pm_lock().
 141  */
 142 void dev_pm_qos_constraints_init(struct device *dev)
 143 {
 144         mutex_lock(&dev_pm_qos_mtx);
 145         dev->power.constraints = NULL;
 146         dev->power.power_state = PMSG_ON;
 147         mutex_unlock(&dev_pm_qos_mtx);
 148 }
 149
 150 /**
 151  * dev_pm_qos_constraints_destroy
 152  * @dev: target device
 153  *
 154  * Called from the device PM subsystem on device removal under device_pm_lock().
 155  */
 156 void dev_pm_qos_constraints_destroy(struct device *dev)
 157 {
 158         struct dev_pm_qos_request *req, *tmp;
 159         struct pm_qos_constraints *c;
 160
 161         mutex_lock(&dev_pm_qos_mtx);
 162
 163         dev->power.power_state = PMSG_INVALID;
 164         c = dev->power.constraints;
 165         if (!c)
 166                 goto out;
 167
 168         /* Flush the constraints list for the device */
 169         plist_for_each_entry_safe(req, tmp, &c->list, node) {
 170                 /*
 171                  * Update constraints list and call the notification
 172                  * callbacks if needed
 173                  */
 174                 apply_constraint(req, PM_QOS_REMOVE_REQ, PM_QOS_DEFAULT_VALUE);
 175                 memset(req, 0, sizeof(*req));
 176         }
 177
 178         spin_lock_irq(&dev->power.lock);
 179         dev->power.constraints = NULL;
 180         spin_unlock_irq(&dev->power.lock);
 181
 182         kfree(c->notifiers);
 183         kfree(c);
 184
 185  out:
 186         mutex_unlock(&dev_pm_qos_mtx);
 187 }
 188
 189 /**
 190  * dev_pm_qos_add_request - inserts new qos request into the list
 191  * @dev: target device for the constraint
 192  * @req: pointer to a preallocated handle
 193  * @value: defines the qos request
 194  *
 195  * This function inserts a new entry in the device constraints list of
 196  * requested qos performance characteristics. It recomputes the aggregate
 197  * QoS expectations of parameters and initializes the dev_pm_qos_request
 198  * handle.  Caller needs to save this handle for later use in updates and
 199  * removal.
 200  *
 201  * Returns 1 if the aggregated constraint value has changed,
 202  * 0 if the aggregated constraint value has not changed,
 203  * -EINVAL in case of wrong parameters, -ENOMEM if there's not enough memory
 204  * to allocate for data structures, -ENODEV if the device has just been removed
 205  * from the system.
 206  */
 207 int dev_pm_qos_add_request(struct device *dev, struct dev_pm_qos_request *req,
 208                            s32 value)
 209 {
 210         int ret = 0;
 211
 212         if (!dev || !req) /*guard against callers passing in null */
 213                 return -EINVAL;
 214
 215         if (WARN(dev_pm_qos_request_active(req),
 216                  "%s() called for already added request\n", __func__))
 217                 return -EINVAL;
 218
 219         req->dev = dev;
 220
 221         mutex_lock(&dev_pm_qos_mtx);
 222
 223         if (!dev->power.constraints) {
 224                 if (dev->power.power_state.event == PM_EVENT_INVALID) {
 225                         /* The device has been removed from the system. */
 226                         req->dev = NULL;
 227                         ret = -ENODEV;
 228                         goto out;
 229                 } else {
 230                         /*
 231                          * Allocate the constraints data on the first call to
 232                          * add_request, i.e. only if the data is not already
 233                          * allocated and if the device has not been removed.
 234                          */
 235                         ret = dev_pm_qos_constraints_allocate(dev);
 236                 }
 237         }
 238
 239         if (!ret)
 240                 ret = apply_constraint(req, PM_QOS_ADD_REQ, value);
 241
 242  out:
 243         mutex_unlock(&dev_pm_qos_mtx);
 244
 245         return ret;
 246 }
 247 EXPORT_SYMBOL_GPL(dev_pm_qos_add_request);
 248
 249 /**
 250  * dev_pm_qos_update_request - modifies an existing qos request
 251  * @req : handle to list element holding a dev_pm_qos request to use
 252  * @new_value: defines the qos request
 253  *
 254  * Updates an existing dev PM qos request along with updating the
 255  * target value.
 256  *
 257  * Attempts are made to make this code callable on hot code paths.
 258  *
 259  * Returns 1 if the aggregated constraint value has changed,
 260  * 0 if the aggregated constraint value has not changed,
 261  * -EINVAL in case of wrong parameters, -ENODEV if the device has been
 262  * removed from the system
 263  */
 264 int dev_pm_qos_update_request(struct dev_pm_qos_request *req,
 265                               s32 new_value)
 266 {
 267         int ret = 0;
 268
 269         if (!req) /*guard against callers passing in null */
 270                 return -EINVAL;
 271
 272         if (WARN(!dev_pm_qos_request_active(req),
 273                  "%s() called for unknown object\n", __func__))
 274                 return -EINVAL;
 275
 276         mutex_lock(&dev_pm_qos_mtx);
 277
 278         if (req->dev->power.constraints) {
 279                 if (new_value != req->node.prio)
 280                         ret = apply_constraint(req, PM_QOS_UPDATE_REQ,
 281                                                new_value);
 282         } else {
 283                 /* Return if the device has been removed */
 284                 ret = -ENODEV;
 285         }
 286
 287         mutex_unlock(&dev_pm_qos_mtx);
 288         return ret;
 289 }
 290 EXPORT_SYMBOL_GPL(dev_pm_qos_update_request);
 291
 292 /**
 293  * dev_pm_qos_remove_request - modifies an existing qos request
 294  * @req: handle to request list element
 295  *
 296  * Will remove pm qos request from the list of constraints and
 297  * recompute the current target value. Call this on slow code paths.
 298  *
 299  * Returns 1 if the aggregated constraint value has changed,
 300  * 0 if the aggregated constraint value has not changed,
 301  * -EINVAL in case of wrong parameters, -ENODEV if the device has been
 302  * removed from the system
 303  */
 304 int dev_pm_qos_remove_request(struct dev_pm_qos_request *req)
 305 {
 306         int ret = 0;
 307
 308         if (!req) /*guard against callers passing in null */
 309                 return -EINVAL;
 310
 311         if (WARN(!dev_pm_qos_request_active(req),
 312                  "%s() called for unknown object\n", __func__))
 313                 return -EINVAL;
 314
 315         mutex_lock(&dev_pm_qos_mtx);
 316
 317         if (req->dev->power.constraints) {
 318                 ret = apply_constraint(req, PM_QOS_REMOVE_REQ,
 319                                        PM_QOS_DEFAULT_VALUE);
 320                 memset(req, 0, sizeof(*req));
 321         } else {
 322                 /* Return if the device has been removed */
 323                 ret = -ENODEV;
 324         }
 325
 326         mutex_unlock(&dev_pm_qos_mtx);
 327         return ret;
 328 }
 329 EXPORT_SYMBOL_GPL(dev_pm_qos_remove_request);
 330
 331 /**
 332  * dev_pm_qos_add_notifier - sets notification entry for changes to target value
 333  * of per-device PM QoS constraints
 334  *
 335  * @dev: target device for the constraint
 336  * @notifier: notifier block managed by caller.
 337  *
 338  * Will register the notifier into a notification chain that gets called
 339  * upon changes to the target value for the device.
 340  */
 341 int dev_pm_qos_add_notifier(struct device *dev, struct notifier_block *notifier)
 342 {
 343         int retval = 0;
 344
 345         mutex_lock(&dev_pm_qos_mtx);
 346
 347         /* Silently return if the constraints object is not present. */
 348         if (dev->power.constraints)
 349                 retval = blocking_notifier_chain_register(
 350                                 dev->power.constraints->notifiers,
 351                                 notifier);
 352
 353         mutex_unlock(&dev_pm_qos_mtx);
 354         return retval;
 355 }
 356 EXPORT_SYMBOL_GPL(dev_pm_qos_add_notifier);
 357
 358 /**
 359  * dev_pm_qos_remove_notifier - deletes notification for changes to target value
 360  * of per-device PM QoS constraints
 361  *
 362  * @dev: target device for the constraint
 363  * @notifier: notifier block to be removed.
 364  *
 365  * Will remove the notifier from the notification chain that gets called
 366  * upon changes to the target value.
 367  */
 368 int dev_pm_qos_remove_notifier(struct device *dev,
 369                                struct notifier_block *notifier)
 370 {
 371         int retval = 0;
 372
 373         mutex_lock(&dev_pm_qos_mtx);
 374
 375         /* Silently return if the constraints object is not present. */
 376         if (dev->power.constraints)
 377                 retval = blocking_notifier_chain_unregister(
 378                                 dev->power.constraints->notifiers,
 379                                 notifier);
 380
 381         mutex_unlock(&dev_pm_qos_mtx);
 382         return retval;
 383 }
 384 EXPORT_SYMBOL_GPL(dev_pm_qos_remove_notifier);
 385
 386 /**
 387  * dev_pm_qos_add_global_notifier - sets notification entry for changes to
 388  * target value of the PM QoS constraints for any device
 389  *
 390  * @notifier: notifier block managed by caller.
 391  *
 392  * Will register the notifier into a notification chain that gets called
 393  * upon changes to the target value for any device.
 394  */
 395 int dev_pm_qos_add_global_notifier(struct notifier_block *notifier)
 396 {
 397         return blocking_notifier_chain_register(&dev_pm_notifiers, notifier);
 398 }
 399 EXPORT_SYMBOL_GPL(dev_pm_qos_add_global_notifier);
 400
 401 /**
 402  * dev_pm_qos_remove_global_notifier - deletes notification for changes to
 403  * target value of PM QoS constraints for any device
 404  *
 405  * @notifier: notifier block to be removed.
 406  *
 407  * Will remove the notifier from the notification chain that gets called
 408  * upon changes to the target value for any device.
 409  */
 410 int dev_pm_qos_remove_global_notifier(struct notifier_block *notifier)
 411 {
 412         return blocking_notifier_chain_unregister(&dev_pm_notifiers, notifier);
 413 }
 414 EXPORT_SYMBOL_GPL(dev_pm_qos_remove_global_notifier);