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
  47 /*
  48  * locking rule: all changes to constraints or notifiers lists
  49  * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
  50  * held, taken with _irqsave.  One lock to rule them all
  51  */
  52 struct pm_qos_object {
  53         struct pm_qos_constraints *constraints;
  54         struct miscdevice pm_qos_power_miscdev;
  55         char *name;
  56 };
  57
  58 static DEFINE_SPINLOCK(pm_qos_lock);
  59
  60 static struct pm_qos_object null_pm_qos;
  61
  62 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  63 static struct pm_qos_constraints cpu_dma_constraints = {
  64         .list = PLIST_HEAD_INIT(cpu_dma_constraints.list),
  65         .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  66         .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  67         .type = PM_QOS_MIN,
  68         .notifiers = &cpu_dma_lat_notifier,
  69 };
  70 static struct pm_qos_object cpu_dma_pm_qos = {
  71         .constraints = &cpu_dma_constraints,
  72 };
  73
  74 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  75 static struct pm_qos_constraints network_lat_constraints = {
  76         .list = PLIST_HEAD_INIT(network_lat_constraints.list),
  77         .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  78         .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  79         .type = PM_QOS_MIN,
  80         .notifiers = &network_lat_notifier,
  81 };
  82 static struct pm_qos_object network_lat_pm_qos = {
  83         .constraints = &network_lat_constraints,
  84         .name = "network_latency",
  85 };
  86
  87
  88 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  89 static struct pm_qos_constraints network_tput_constraints = {
  90         .list = PLIST_HEAD_INIT(network_tput_constraints.list),
  91         .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
  92         .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
  93         .type = PM_QOS_MAX,
  94         .notifiers = &network_throughput_notifier,
  95 };
  96 static struct pm_qos_object network_throughput_pm_qos = {
  97         .constraints = &network_tput_constraints,
  98         .name = "network_throughput",
  99 };
 100
 101
 102 static struct pm_qos_object *pm_qos_array[] = {
 103         &null_pm_qos,
 104         &cpu_dma_pm_qos,
 105         &network_lat_pm_qos,
 106         &network_throughput_pm_qos
 107 };
 108
 109 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 110                 size_t count, loff_t *f_pos);
 111 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 112                 size_t count, loff_t *f_pos);
 113 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 114 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 115
 116 static const struct file_operations pm_qos_power_fops = {
 117         .write = pm_qos_power_write,
 118         .read = pm_qos_power_read,
 119         .open = pm_qos_power_open,
 120         .release = pm_qos_power_release,
 121         .llseek = noop_llseek,
 122 };
 123
 124 /* unlocked internal variant */
 125 static inline int pm_qos_get_value(struct pm_qos_constraints *c)
 126 {
 127         if (plist_head_empty(&c->list))
 128                 return c->default_value;
 129
 130         switch (c->type) {
 131         case PM_QOS_MIN:
 132                 return plist_first(&c->list)->prio;
 133
 134         case PM_QOS_MAX:
 135                 return plist_last(&c->list)->prio;
 136
 137         default:
 138                 /* runtime check for not using enum */
 139                 BUG();
 140         }
 141 }
 142
 143 s32 pm_qos_read_value(struct pm_qos_constraints *c)
 144 {
 145         return c->target_value;
 146 }
 147
 148 static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value)
 149 {
 150         c->target_value = value;
 151 }
 152
 153 /**
 154  * pm_qos_update_target - manages the constraints list and calls the notifiers
 155  *  if needed
 156  * @c: constraints data struct
 157  * @node: request to add to the list, to update or to remove
 158  * @action: action to take on the constraints list
 159  * @value: value of the request to add or update
 160  *
 161  * This function returns 1 if the aggregated constraint value has changed, 0
 162  *  otherwise.
 163  */
 164 int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node,
 165                          enum pm_qos_req_action action, int value)
 166 {
 167         unsigned long flags;
 168         int prev_value, curr_value, new_value;
 169
 170         spin_lock_irqsave(&pm_qos_lock, flags);
 171         prev_value = pm_qos_get_value(c);
 172         if (value == PM_QOS_DEFAULT_VALUE)
 173                 new_value = c->default_value;
 174         else
 175                 new_value = value;
 176
 177         switch (action) {
 178         case PM_QOS_REMOVE_REQ:
 179                 plist_del(node, &c->list);
 180                 break;
 181         case PM_QOS_UPDATE_REQ:
 182                 /*
 183                  * to change the list, we atomically remove, reinit
 184                  * with new value and add, then see if the extremal
 185                  * changed
 186                  */
 187                 plist_del(node, &c->list);
 188         case PM_QOS_ADD_REQ:
 189                 plist_node_init(node, new_value);
 190                 plist_add(node, &c->list);
 191                 break;
 192         default:
 193                 /* no action */
 194                 ;
 195         }
 196
 197         curr_value = pm_qos_get_value(c);
 198         pm_qos_set_value(c, curr_value);
 199
 200         spin_unlock_irqrestore(&pm_qos_lock, flags);
 201
 202         if (prev_value != curr_value) {
 203                 blocking_notifier_call_chain(c->notifiers,
 204                                              (unsigned long)curr_value,
 205                                              NULL);
 206                 return 1;
 207         } else {
 208                 return 0;
 209         }
 210 }
 211
 212 /**
 213  * pm_qos_request - returns current system wide qos expectation
 214  * @pm_qos_class: identification of which qos value is requested
 215  *
 216  * This function returns the current target value.
 217  */
 218 int pm_qos_request(int pm_qos_class)
 219 {
 220         return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints);
 221 }
 222 EXPORT_SYMBOL_GPL(pm_qos_request);
 223
 224 int pm_qos_request_active(struct pm_qos_request *req)
 225 {
 226         return req->pm_qos_class != 0;
 227 }
 228 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 229
 230 /**
 231  * pm_qos_add_request - inserts new qos request into the list
 232  * @req: pointer to a preallocated handle
 233  * @pm_qos_class: identifies which list of qos request to use
 234  * @value: defines the qos request
 235  *
 236  * This function inserts a new entry in the pm_qos_class list of requested qos
 237  * performance characteristics.  It recomputes the aggregate QoS expectations
 238  * for the pm_qos_class of parameters and initializes the pm_qos_request
 239  * handle.  Caller needs to save this handle for later use in updates and
 240  * removal.
 241  */
 242
 243 void pm_qos_add_request(struct pm_qos_request *req,
 244                         int pm_qos_class, s32 value)
 245 {
 246         if (!req) /*guard against callers passing in null */
 247                 return;
 248
 249         if (pm_qos_request_active(req)) {
 250                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 251                 return;
 252         }
 253         req->pm_qos_class = pm_qos_class;
 254         pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints,
 255                              &req->node, PM_QOS_ADD_REQ, value);
 256 }
 257 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 258
 259 /**
 260  * pm_qos_update_request - modifies an existing qos request
 261  * @req : handle to list element holding a pm_qos request to use
 262  * @value: defines the qos request
 263  *
 264  * Updates an existing qos request for the pm_qos_class of parameters along
 265  * with updating the target pm_qos_class value.
 266  *
 267  * Attempts are made to make this code callable on hot code paths.
 268  */
 269 void pm_qos_update_request(struct pm_qos_request *req,
 270                            s32 new_value)
 271 {
 272         if (!req) /*guard against callers passing in null */
 273                 return;
 274
 275         if (!pm_qos_request_active(req)) {
 276                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 277                 return;
 278         }
 279
 280         if (new_value != req->node.prio)
 281                 pm_qos_update_target(
 282                         pm_qos_array[req->pm_qos_class]->constraints,
 283                         &req->node, PM_QOS_UPDATE_REQ, new_value);
 284 }
 285 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 286
 287 /**
 288  * pm_qos_remove_request - modifies an existing qos request
 289  * @req: handle to request list element
 290  *
 291  * Will remove pm qos request from the list of constraints and
 292  * recompute the current target value for the pm_qos_class.  Call this
 293  * on slow code paths.
 294  */
 295 void pm_qos_remove_request(struct pm_qos_request *req)
 296 {
 297         if (!req) /*guard against callers passing in null */
 298                 return;
 299                 /* silent return to keep pcm code cleaner */
 300
 301         if (!pm_qos_request_active(req)) {
 302                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 303                 return;
 304         }
 305
 306         pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints,
 307                              &req->node, PM_QOS_REMOVE_REQ,
 308                              PM_QOS_DEFAULT_VALUE);
 309         memset(req, 0, sizeof(*req));
 310 }
 311 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 312
 313 /**
 314  * pm_qos_add_notifier - sets notification entry for changes to target value
 315  * @pm_qos_class: identifies which qos target changes should be notified.
 316  * @notifier: notifier block managed by caller.
 317  *
 318  * will register the notifier into a notification chain that gets called
 319  * upon changes to the pm_qos_class target value.
 320  */
 321 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 322 {
 323         int retval;
 324
 325         retval = blocking_notifier_chain_register(
 326                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 327                         notifier);
 328
 329         return retval;
 330 }
 331 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 332
 333 /**
 334  * pm_qos_remove_notifier - deletes notification entry from chain.
 335  * @pm_qos_class: identifies which qos target changes are notified.
 336  * @notifier: notifier block to be removed.
 337  *
 338  * will remove the notifier from the notification chain that gets called
 339  * upon changes to the pm_qos_class target value.
 340  */
 341 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 342 {
 343         int retval;
 344
 345         retval = blocking_notifier_chain_unregister(
 346                         pm_qos_array[pm_qos_class]->constraints->notifiers,
 347                         notifier);
 348
 349         return retval;
 350 }
 351 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 352
 353 /* User space interface to PM QoS classes via misc devices */
 354 static int register_pm_qos_misc(struct pm_qos_object *qos)
 355 {
 356         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 357         qos->pm_qos_power_miscdev.name = qos->name;
 358         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 359
 360         return misc_register(&qos->pm_qos_power_miscdev);
 361 }
 362
 363 static int find_pm_qos_object_by_minor(int minor)
 364 {
 365         int pm_qos_class;
 366
 367         for (pm_qos_class = 0;
 368                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 369                 if (minor ==
 370                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 371                         return pm_qos_class;
 372         }
 373         return -1;
 374 }
 375
 376 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 377 {
 378         long pm_qos_class;
 379
 380         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 381         if (pm_qos_class >= 0) {
 382                 struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL);
 383                 if (!req)
 384                         return -ENOMEM;
 385
 386                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 387                 filp->private_data = req;
 388
 389                 return 0;
 390         }
 391         return -EPERM;
 392 }
 393
 394 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 395 {
 396         struct pm_qos_request *req;
 397
 398         req = filp->private_data;
 399         pm_qos_remove_request(req);
 400         kfree(req);
 401
 402         return 0;
 403 }
 404
 405
 406 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 407                 size_t count, loff_t *f_pos)
 408 {
 409         s32 value;
 410         unsigned long flags;
 411         struct pm_qos_request *req = filp->private_data;
 412
 413         if (!req)
 414                 return -EINVAL;
 415         if (!pm_qos_request_active(req))
 416                 return -EINVAL;
 417
 418         spin_lock_irqsave(&pm_qos_lock, flags);
 419         value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints);
 420         spin_unlock_irqrestore(&pm_qos_lock, flags);
 421
 422         return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 423 }
 424
 425 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 426                 size_t count, loff_t *f_pos)
 427 {
 428         s32 value;
 429         struct pm_qos_request *req;
 430
 431         if (count == sizeof(s32)) {
 432                 if (copy_from_user(&value, buf, sizeof(s32)))
 433                         return -EFAULT;
 434         } else if (count <= 11) { /* ASCII perhaps? */
 435                 char ascii_value[11];
 436                 unsigned long int ulval;
 437                 int ret;
 438
 439                 if (copy_from_user(ascii_value, buf, count))
 440                         return -EFAULT;
 441
 442                 if (count > 10) {
 443                         if (ascii_value[10] == '\n')
 444                                 ascii_value[10] = '\0';
 445                         else
 446                                 return -EINVAL;
 447                 } else {
 448                         ascii_value[count] = '\0';
 449                 }
 450                 ret = strict_strtoul(ascii_value, 16, &ulval);
 451                 if (ret) {
 452                         pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 453                         return -EINVAL;
 454                 }
 455                 value = (s32)lower_32_bits(ulval);
 456         } else {
 457                 return -EINVAL;
 458         }
 459
 460         req = filp->private_data;
 461         pm_qos_update_request(req, value);
 462
 463         return count;
 464 }
 465
 466
 467 static int __init pm_qos_power_init(void)
 468 {
 469         int ret = 0;
 470
 471         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 472         if (ret < 0) {
 473                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 474                 return ret;
 475         }
 476         ret = register_pm_qos_misc(&network_lat_pm_qos);
 477         if (ret < 0) {
 478                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 479                 return ret;
 480         }
 481         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 482         if (ret < 0)
 483                 printk(KERN_ERR
 484                         "pm_qos_param: network_throughput setup failed\n");
 485
 486         return ret;
 487 }
 488
 489 late_initcall(pm_qos_power_init);