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         .name = "cpu_dma_latency",
  74 };
  75
  76 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  77 static 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 };
  84 static struct pm_qos_object network_lat_pm_qos = {
  85         .constraints = &network_lat_constraints,
  86         .name = "network_latency",
  87 };
  88
  89
  90 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  91 static 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 };
  98 static struct pm_qos_object network_throughput_pm_qos = {
  99         .constraints = &network_tput_constraints,
 100         .name = "network_throughput",
 101 };
 102
 103
 104 static 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
 111 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 112                 size_t count, loff_t *f_pos);
 113 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 114                 size_t count, loff_t *f_pos);
 115 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 116 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 117
 118 static 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 */
 127 static 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
 145 s32 pm_qos_read_value(struct pm_qos_constraints *c)
 146 {
 147         return c->target_value;
 148 }
 149
 150 static 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  */
 166 int 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  */
 220 int pm_qos_request(int pm_qos_class)
 221 {
 222         return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
 223 }
 224 EXPORT_SYMBOL_GPL(pm_qos_request);
 225
 226 int pm_qos_request_active(struct pm_qos_request *req)
 227 {
 228         return req->pm_qos_class != 0;
 229 }
 230 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 231
 232 /**
 233  * pm_qos_add_request - inserts new qos request into the list
 234  * @req: pointer to a preallocated handle
 235  * @pm_qos_class: identifies which list of qos request to use
 236  * @value: defines the qos request
 237  *
 238  * This function inserts a new entry in the pm_qos_class list of requested qos
 239  * performance characteristics.  It recomputes the aggregate QoS expectations
 240  * for the pm_qos_class of parameters and initializes the pm_qos_request
 241  * handle.  Caller needs to save this handle for later use in updates and
 242  * removal.
 243  */
 244
 245 void pm_qos_add_request(struct pm_qos_request *req,
 246                         int pm_qos_class, s32 value)
 247 {
 248         if (!req) /*guard against callers passing in null */
 249                 return;
 250
 251         if (pm_qos_request_active(req)) {
 252                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 253                 return;
 254         }
 255         req->pm_qos_class = pm_qos_class;
 256         pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
 257                              &req->node, PM_QOS_ADD_REQ, value);
 258 }
 259 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 260
 261 /**
 262  * pm_qos_update_request - modifies an existing qos request
 263  * @req : handle to list element holding a pm_qos request to use
 264  * @value: defines the qos request
 265  *
 266  * Updates an existing qos request for the pm_qos_class of parameters along
 267  * with updating the target pm_qos_class value.
 268  *
 269  * Attempts are made to make this code callable on hot code paths.
 270  */
 271 void pm_qos_update_request(struct pm_qos_request *req,
 272                            s32 new_value)
 273 {
 274         if (!req) /*guard against callers passing in null */
 275                 return;
 276
 277         if (!pm_qos_request_active(req)) {
 278                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 279                 return;
 280         }
 281
 282         if (new_value != req->node.prio)
 283                 pm_qos_update_target(
 284                         pm_qos_array[req->pm_qos_class]->constraints,
 285                         &req->node, PM_QOS_UPDATE_REQ, new_value);
 286 }
 287 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 288
 289 /**
 290  * pm_qos_remove_request - modifies an existing qos request
 291  * @req: handle to request list element
 292  *
 293  * Will remove pm qos request from the list of constraints and
 294  * recompute the current target value for the pm_qos_class.  Call this
 295  * on slow code paths.
 296  */
 297 void pm_qos_remove_request(struct pm_qos_request *req)
 298 {
 299         if (!req) /*guard against callers passing in null */
 300                 return;
 301                 /* silent return to keep pcm code cleaner */
 302
 303         if (!pm_qos_request_active(req)) {
 304                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 305                 return;
 306         }
 307
 308         pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
 309                              &req->node, PM_QOS_REMOVE_REQ,
 310                              PM_QOS_DEFAULT_VALUE);
 311         memset(req, 0, sizeof(*req));
 312 }
 313 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 314
 315 /**
 316  * pm_qos_add_notifier - sets notification entry for changes to target value
 317  * @pm_qos_class: identifies which qos target changes should be notified.
 318  * @notifier: notifier block managed by caller.
 319  *
 320  * will register the notifier into a notification chain that gets called
 321  * upon changes to the pm_qos_class target value.
 322  */
 323 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 324 {
 325         int retval;
 326
 327         retval = blocking_notifier_chain_register(
 328                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 329                         notifier);
 330
 331         return retval;
 332 }
 333 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 334
 335 /**
 336  * pm_qos_remove_notifier - deletes notification entry from chain.
 337  * @pm_qos_class: identifies which qos target changes are notified.
 338  * @notifier: notifier block to be removed.
 339  *
 340  * will remove the notifier from the notification chain that gets called
 341  * upon changes to the pm_qos_class target value.
 342  */
 343 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 344 {
 345         int retval;
 346
 347         retval = blocking_notifier_chain_unregister(
 348                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 349                         notifier);
 350
 351         return retval;
 352 }
 353 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 354
 355 /* User space interface to PM QoS classes via misc devices */
 356 static int register_pm_qos_misc(struct pm_qos_object *qos)
 357 {
 358         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 359         qos->pm_qos_power_miscdev.name = qos->name;
 360         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 361
 362         return misc_register(&qos->pm_qos_power_miscdev);
 363 }
 364
 365 static int find_pm_qos_object_by_minor(int minor)
 366 {
 367         int pm_qos_class;
 368
 369         for (pm_qos_class = 0;
 370                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 371                 if (minor ==
 372                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 373                         return pm_qos_class;
 374         }
 375         return -1;
 376 }
 377
 378 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 379 {
 380         long pm_qos_class;
 381
 382         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 383         if (pm_qos_class >= 0) {
 384                 struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
 385                 if (!req)
 386                         return -ENOMEM;
 387
 388                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 389                 filp->private_data = req;
 390
 391                 return 0;
 392         }
 393         return -EPERM;
 394 }
 395
 396 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 397 {
 398         struct pm_qos_request *req;
 399
 400         req = filp->private_data;
 401         pm_qos_remove_request(req);
 402         kfree(req);
 403
 404         return 0;
 405 }
 406
 407
 408 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 409                 size_t count, loff_t *f_pos)
 410 {
 411         s32 value;
 412         unsigned long flags;
 413         struct pm_qos_request *req = filp->private_data;
 414
 415         if (!req)
 416                 return -EINVAL;
 417         if (!pm_qos_request_active(req))
 418                 return -EINVAL;
 419
 420         spin_lock_irqsave(&pm_qos_lock, flags);
 421         value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
 422         spin_unlock_irqrestore(&pm_qos_lock, flags);
 423
 424         return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 425 }
 426
 427 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 428                 size_t count, loff_t *f_pos)
 429 {
 430         s32 value;
 431         struct pm_qos_request *req;
 432
 433         if (count == sizeof(s32)) {
 434                 if (copy_from_user(&value, buf, sizeof(s32)))
 435                         return -EFAULT;
 436         } else if (count <= 11) { /* ASCII perhaps? */
 437                 char ascii_value[11];
 438                 unsigned long int ulval;
 439                 int ret;
 440
 441                 if (copy_from_user(ascii_value, buf, count))
 442                         return -EFAULT;
 443
 444                 if (count > 10) {
 445                         if (ascii_value[10] == '\n')
 446                                 ascii_value[10] = '\0';
 447                         else
 448                                 return -EINVAL;
 449                 } else {
 450                         ascii_value[count] = '\0';
 451                 }
 452                 ret = strict_strtoul(ascii_value, 16, &ulval);
 453                 if (ret) {
 454                         pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 455                         return -EINVAL;
 456                 }
 457                 value = (s32)lower_32_bits(ulval);
 458         } else {
 459                 return -EINVAL;
 460         }
 461
 462         req = filp->private_data;
 463         pm_qos_update_request(req, value);
 464
 465         return count;
 466 }
 467
 468
 469 static int __init pm_qos_power_init(void)
 470 {
 471         int ret = 0;
 472         int i;
 473
 474         BUILD_BUG_ON(ARRAY_SIZE(pm_qos_array) != PM_QOS_NUM_CLASSES);
 475
 476         for (i = 1; i < PM_QOS_NUM_CLASSES; i++) {
 477                 ret = register_pm_qos_misc(pm_qos_array[i]);
 478                 if (ret < 0) {
 479                         printk(KERN_ERR "pm_qos_param: %s setup failed\n",
 480                                pm_qos_array[i]->name);
 481                         return ret;
 482                 }
 483         }
 484
 485         return ret;
 486 }
 487
 488 late_initcall(pm_qos_power_init);