kernel/power/qos.c

   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  */
  53 struct pm_qos_object {
  54         struct pm_qos_constraints *constraints;
  55         struct miscdevice pm_qos_power_miscdev;
  56         char *name;
  57 };
  58
  59 static DEFINE_SPINLOCK(pm_qos_lock);
  60
  61 static struct pm_qos_object null_pm_qos;
  62
  63 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  64 static 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 };
  71 static struct pm_qos_object cpu_dma_pm_qos = {
  72         .constraints = &cpu_dma_constraints,
  73 };
  74
  75 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  76 static struct pm_qos_constraints network_lat_constraints = {
  77         .list = PLIST_HEAD_INIT(network_lat_constraints.list),
  78         .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  79         .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  80         .type = PM_QOS_MIN,
  81         .notifiers = &network_lat_notifier,
  82 };
  83 static struct pm_qos_object network_lat_pm_qos = {
  84         .constraints = &network_lat_constraints,
  85         .name = "network_latency",
  86 };
  87
  88
  89 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  90 static struct pm_qos_constraints network_tput_constraints = {
  91         .list = PLIST_HEAD_INIT(network_tput_constraints.list),
  92         .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
  93         .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
  94         .type = PM_QOS_MAX,
  95         .notifiers = &network_throughput_notifier,
  96 };
  97 static struct pm_qos_object network_throughput_pm_qos = {
  98         .constraints = &network_tput_constraints,
  99         .name = "network_throughput",
 100 };
 101
 102
 103 static struct pm_qos_object *pm_qos_array[] = {
 104         &null_pm_qos,
 105         &cpu_dma_pm_qos,
 106         &network_lat_pm_qos,
 107         &network_throughput_pm_qos
 108 };
 109
 110 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 111                 size_t count, loff_t *f_pos);
 112 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 113                 size_t count, loff_t *f_pos);
 114 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 115 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 116
 117 static const struct file_operations pm_qos_power_fops = {
 118         .write = pm_qos_power_write,
 119         .read = pm_qos_power_read,
 120         .open = pm_qos_power_open,
 121         .release = pm_qos_power_release,
 122         .llseek = noop_llseek,
 123 };
 124
 125 /* unlocked internal variant */
 126 static inline int pm_qos_get_value(struct pm_qos_constraints *c)
 127 {
 128         if (plist_head_empty(&c->list))
 129                 return c->default_value;
 130
 131         switch (c->type) {
 132         case PM_QOS_MIN:
 133                 return plist_first(&c->list)->prio;
 134
 135         case PM_QOS_MAX:
 136                 return plist_last(&c->list)->prio;
 137
 138         default:
 139                 /* runtime check for not using enum */
 140                 BUG();
 141         }
 142 }
 143
 144 s32 pm_qos_read_value(struct pm_qos_constraints *c)
 145 {
 146         return c->target_value;
 147 }
 148
 149 static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
 150 {
 151         c->target_value = value;
 152 }
 153
 154 /**
 155  * pm_qos_update_target - manages the constraints list and calls the notifiers
 156  *  if needed
 157  * @c: constraints data struct
 158  * @node: request to add to the list, to update or to remove
 159  * @action: action to take on the constraints list
 160  * @value: value of the request to add or update
 161  *
 162  * This function returns 1 if the aggregated constraint value has changed, 0
 163  *  otherwise.
 164  */
 165 int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
 166                          enum pm_qos_req_action action, int value)
 167 {
 168         unsigned long flags;
 169         int prev_value, curr_value, new_value;
 170
 171         spin_lock_irqsave(&pm_qos_lock, flags);
 172         prev_value = pm_qos_get_value(c);
 173         if (value == PM_QOS_DEFAULT_VALUE)
 174                 new_value = c->default_value;
 175         else
 176                 new_value = value;
 177
 178         switch (action) {
 179         case PM_QOS_REMOVE_REQ:
 180                 plist_del(node, &c->list);
 181                 break;
 182         case PM_QOS_UPDATE_REQ:
 183                 /*
 184                  * to change the list, we atomically remove, reinit
 185                  * with new value and add, then see if the extremal
 186                  * changed
 187                  */
 188                 plist_del(node, &c->list);
 189         case PM_QOS_ADD_REQ:
 190                 plist_node_init(node, new_value);
 191                 plist_add(node, &c->list);
 192                 break;
 193         default:
 194                 /* no action */
 195                 ;
 196         }
 197
 198         curr_value = pm_qos_get_value(c);
 199         pm_qos_set_value(c, curr_value);
 200
 201         spin_unlock_irqrestore(&pm_qos_lock, flags);
 202
 203         if (prev_value != curr_value) {
 204                 blocking_notifier_call_chain(c->notifiers,
 205                                              (unsigned long)curr_value,
 206                                              NULL);
 207                 return 1;
 208         } else {
 209                 return 0;
 210         }
 211 }
 212
 213 /**
 214  * pm_qos_request - returns current system wide qos expectation
 215  * @pm_qos_class: identification of which qos value is requested
 216  *
 217  * This function returns the current target value.
 218  */
 219 int pm_qos_request(int pm_qos_class)
 220 {
 221         return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
 222 }
 223 EXPORT_SYMBOL_GPL(pm_qos_request);
 224
 225 int pm_qos_request_active(struct pm_qos_request *req)
 226 {
 227         return req->pm_qos_class != 0;
 228 }
 229 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 230
 231 /**
 232  * pm_qos_add_request - inserts new qos request into the list
 233  * @req: pointer to a preallocated handle
 234  * @pm_qos_class: identifies which list of qos request to use
 235  * @value: defines the qos request
 236  *
 237  * This function inserts a new entry in the pm_qos_class list of requested qos
 238  * performance characteristics.  It recomputes the aggregate QoS expectations
 239  * for the pm_qos_class of parameters and initializes the pm_qos_request
 240  * handle.  Caller needs to save this handle for later use in updates and
 241  * removal.
 242  */
 243
 244 void pm_qos_add_request(struct pm_qos_request *req,
 245                         int pm_qos_class, s32 value)
 246 {
 247         if (!req) /*guard against callers passing in null */
 248                 return;
 249
 250         if (pm_qos_request_active(req)) {
 251                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 252                 return;
 253         }
 254         req->pm_qos_class = pm_qos_class;
 255         pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
 256                              &req->node, PM_QOS_ADD_REQ, value);
 257 }
 258 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 259
 260 /**
 261  * pm_qos_update_request - modifies an existing qos request
 262  * @req : handle to list element holding a pm_qos request to use
 263  * @value: defines the qos request
 264  *
 265  * Updates an existing qos request for the pm_qos_class of parameters along
 266  * with updating the target pm_qos_class value.
 267  *
 268  * Attempts are made to make this code callable on hot code paths.
 269  */
 270 void pm_qos_update_request(struct pm_qos_request *req,
 271                            s32 new_value)
 272 {
 273         if (!req) /*guard against callers passing in null */
 274                 return;
 275
 276         if (!pm_qos_request_active(req)) {
 277                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 278                 return;
 279         }
 280
 281         if (new_value != req->node.prio)
 282                 pm_qos_update_target(
 283                         pm_qos_array[req->pm_qos_class]->constraints,
 284                         &req->node, PM_QOS_UPDATE_REQ, new_value);
 285 }
 286 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 287
 288 /**
 289  * pm_qos_remove_request - modifies an existing qos request
 290  * @req: handle to request list element
 291  *
 292  * Will remove pm qos request from the list of constraints and
 293  * recompute the current target value for the pm_qos_class.  Call this
 294  * on slow code paths.
 295  */
 296 void pm_qos_remove_request(struct pm_qos_request *req)
 297 {
 298         if (!req) /*guard against callers passing in null */
 299                 return;
 300                 /* silent return to keep pcm code cleaner */
 301
 302         if (!pm_qos_request_active(req)) {
 303                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 304                 return;
 305         }
 306
 307         pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
 308                              &req->node, PM_QOS_REMOVE_REQ,
 309                              PM_QOS_DEFAULT_VALUE);
 310         memset(req, 0, sizeof(*req));
 311 }
 312 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 313
 314 /**
 315  * pm_qos_add_notifier - sets notification entry for changes to target value
 316  * @pm_qos_class: identifies which qos target changes should be notified.
 317  * @notifier: notifier block managed by caller.
 318  *
 319  * will register the notifier into a notification chain that gets called
 320  * upon changes to the pm_qos_class target value.
 321  */
 322 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 323 {
 324         int retval;
 325
 326         retval = blocking_notifier_chain_register(
 327                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 328                         notifier);
 329
 330         return retval;
 331 }
 332 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 333
 334 /**
 335  * pm_qos_remove_notifier - deletes notification entry from chain.
 336  * @pm_qos_class: identifies which qos target changes are notified.
 337  * @notifier: notifier block to be removed.
 338  *
 339  * will remove the notifier from the notification chain that gets called
 340  * upon changes to the pm_qos_class target value.
 341  */
 342 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 343 {
 344         int retval;
 345
 346         retval = blocking_notifier_chain_unregister(
 347                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 348                         notifier);
 349
 350         return retval;
 351 }
 352 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 353
 354 /* User space interface to PM QoS classes via misc devices */
 355 static int register_pm_qos_misc(struct pm_qos_object *qos)
 356 {
 357         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 358         qos->pm_qos_power_miscdev.name = qos->name;
 359         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 360
 361         return misc_register(&qos->pm_qos_power_miscdev);
 362 }
 363
 364 static int find_pm_qos_object_by_minor(int minor)
 365 {
 366         int pm_qos_class;
 367
 368         for (pm_qos_class = 0;
 369                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 370                 if (minor ==
 371                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 372                         return pm_qos_class;
 373         }
 374         return -1;
 375 }
 376
 377 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 378 {
 379         long pm_qos_class;
 380
 381         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 382         if (pm_qos_class >= 0) {
 383                 struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
 384                 if (!req)
 385                         return -ENOMEM;
 386
 387                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 388                 filp->private_data = req;
 389
 390                 return 0;
 391         }
 392         return -EPERM;
 393 }
 394
 395 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 396 {
 397         struct pm_qos_request *req;
 398
 399         req = filp->private_data;
 400         pm_qos_remove_request(req);
 401         kfree(req);
 402
 403         return 0;
 404 }
 405
 406
 407 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 408                 size_t count, loff_t *f_pos)
 409 {
 410         s32 value;
 411         unsigned long flags;
 412         struct pm_qos_request *req = filp->private_data;
 413
 414         if (!req)
 415                 return -EINVAL;
 416         if (!pm_qos_request_active(req))
 417                 return -EINVAL;
 418
 419         spin_lock_irqsave(&pm_qos_lock, flags);
 420         value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
 421         spin_unlock_irqrestore(&pm_qos_lock, flags);
 422
 423         return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 424 }
 425
 426 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 427                 size_t count, loff_t *f_pos)
 428 {
 429         s32 value;
 430         struct pm_qos_request *req;
 431
 432         if (count == sizeof(s32)) {
 433                 if (copy_from_user(&value, buf, sizeof(s32)))
 434                         return -EFAULT;
 435         } else if (count <= 11) { /* ASCII perhaps? */
 436                 char ascii_value[11];
 437                 unsigned long int ulval;
 438                 int ret;
 439
 440                 if (copy_from_user(ascii_value, buf, count))
 441                         return -EFAULT;
 442
 443                 if (count > 10) {
 444                         if (ascii_value[10] == '\n')
 445                                 ascii_value[10] = '\0';
 446                         else
 447                                 return -EINVAL;
 448                 } else {
 449                         ascii_value[count] = '\0';
 450                 }
 451                 ret = strict_strtoul(ascii_value, 16, &ulval);
 452                 if (ret) {
 453                         pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 454                         return -EINVAL;
 455                 }
 456                 value = (s32)lower_32_bits(ulval);
 457         } else {
 458                 return -EINVAL;
 459         }
 460
 461         req = filp->private_data;
 462         pm_qos_update_request(req, value);
 463
 464         return count;
 465 }
 466
 467
 468 static int __init pm_qos_power_init(void)
 469 {
 470         int ret = 0;
 471
 472         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 473         if (ret < 0) {
 474                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 475                 return ret;
 476         }
 477         ret = register_pm_qos_misc(&network_lat_pm_qos);
 478         if (ret < 0) {
 479                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 480                 return ret;
 481         }
 482         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 483         if (ret < 0)
 484                 printk(KERN_ERR
 485                         "pm_qos_param: network_throughput setup failed\n");
 486
 487         return ret;
 488 }
 489
 490 late_initcall(pm_qos_power_init);