kernel/pm_qos_params.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_params.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 requests 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 enum pm_qos_type {
  53         PM_QOS_MAX,             /* return the largest value */
  54         PM_QOS_MIN              /* return the smallest value */
  55 };
  56
  57 /*
  58  * Note: The lockless read path depends on the CPU accessing
  59  * target_value atomically.  Atomic access is only guaranteed on all CPU
  60  * types linux supports for 32 bit quantites
  61  */
  62 struct pm_qos_object {
  63         struct plist_head requests;
  64         struct blocking_notifier_head *notifiers;
  65         struct miscdevice pm_qos_power_miscdev;
  66         char *name;
  67         s32 target_value;       /* Do not change to 64 bit */
  68         s32 default_value;
  69         enum pm_qos_type type;
  70 };
  71
  72 static DEFINE_SPINLOCK(pm_qos_lock);
  73
  74 static struct pm_qos_object null_pm_qos;
  75 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  76 static struct pm_qos_object cpu_dma_pm_qos = {
  77         .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests),
  78         .notifiers = &cpu_dma_lat_notifier,
  79         .name = "cpu_dma_latency",
  80         .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  81         .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  82         .type = PM_QOS_MIN,
  83 };
  84
  85 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  86 static struct pm_qos_object network_lat_pm_qos = {
  87         .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests),
  88         .notifiers = &network_lat_notifier,
  89         .name = "network_latency",
  90         .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  91         .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  92         .type = PM_QOS_MIN
  93 };
  94
  95
  96 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  97 static struct pm_qos_object network_throughput_pm_qos = {
  98         .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests),
  99         .notifiers = &network_throughput_notifier,
 100         .name = "network_throughput",
 101         .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
 102         .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
 103         .type = PM_QOS_MAX,
 104 };
 105
 106
 107 static struct pm_qos_object *pm_qos_array[] = {
 108         &null_pm_qos,
 109         &cpu_dma_pm_qos,
 110         &network_lat_pm_qos,
 111         &network_throughput_pm_qos
 112 };
 113
 114 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 115                 size_t count, loff_t *f_pos);
 116 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 117                 size_t count, loff_t *f_pos);
 118 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 119 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 120
 121 static const struct file_operations pm_qos_power_fops = {
 122         .write = pm_qos_power_write,
 123         .read = pm_qos_power_read,
 124         .open = pm_qos_power_open,
 125         .release = pm_qos_power_release,
 126         .llseek = noop_llseek,
 127 };
 128
 129 /* unlocked internal variant */
 130 static inline int pm_qos_get_value(struct pm_qos_object *o)
 131 {
 132         if (plist_head_empty(&o->requests))
 133                 return o->default_value;
 134
 135         switch (o->type) {
 136         case PM_QOS_MIN:
 137                 return plist_first(&o->requests)->prio;
 138
 139         case PM_QOS_MAX:
 140                 return plist_last(&o->requests)->prio;
 141
 142         default:
 143                 /* runtime check for not using enum */
 144                 BUG();
 145         }
 146 }
 147
 148 static inline s32 pm_qos_read_value(struct pm_qos_object *o)
 149 {
 150         return o->target_value;
 151 }
 152
 153 static inline void pm_qos_set_value(struct pm_qos_object *o, s32 value)
 154 {
 155         o->target_value = value;
 156 }
 157
 158 static void update_target(struct pm_qos_object *o, struct plist_node *node,
 159                           int del, int value)
 160 {
 161         unsigned long flags;
 162         int prev_value, curr_value;
 163
 164         spin_lock_irqsave(&pm_qos_lock, flags);
 165         prev_value = pm_qos_get_value(o);
 166         /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
 167         if (value != PM_QOS_DEFAULT_VALUE) {
 168                 /*
 169                  * to change the list, we atomically remove, reinit
 170                  * with new value and add, then see if the extremal
 171                  * changed
 172                  */
 173                 plist_del(node, &o->requests);
 174                 plist_node_init(node, value);
 175                 plist_add(node, &o->requests);
 176         } else if (del) {
 177                 plist_del(node, &o->requests);
 178         } else {
 179                 plist_add(node, &o->requests);
 180         }
 181         curr_value = pm_qos_get_value(o);
 182         pm_qos_set_value(o, curr_value);
 183         spin_unlock_irqrestore(&pm_qos_lock, flags);
 184
 185         if (prev_value != curr_value)
 186                 blocking_notifier_call_chain(o->notifiers,
 187                                              (unsigned long)curr_value,
 188                                              NULL);
 189 }
 190
 191 static int register_pm_qos_misc(struct pm_qos_object *qos)
 192 {
 193         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 194         qos->pm_qos_power_miscdev.name = qos->name;
 195         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 196
 197         return misc_register(&qos->pm_qos_power_miscdev);
 198 }
 199
 200 static int find_pm_qos_object_by_minor(int minor)
 201 {
 202         int pm_qos_class;
 203
 204         for (pm_qos_class = 0;
 205                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 206                 if (minor ==
 207                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 208                         return pm_qos_class;
 209         }
 210         return -1;
 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]);
 222 }
 223 EXPORT_SYMBOL_GPL(pm_qos_request);
 224
 225 int pm_qos_request_active(struct pm_qos_request_list *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  * @dep: 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_list
 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_list *dep,
 245                         int pm_qos_class, s32 value)
 246 {
 247         struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
 248         int new_value;
 249
 250         if (pm_qos_request_active(dep)) {
 251                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 252                 return;
 253         }
 254         if (value == PM_QOS_DEFAULT_VALUE)
 255                 new_value = o->default_value;
 256         else
 257                 new_value = value;
 258         plist_node_init(&dep->list, new_value);
 259         dep->pm_qos_class = pm_qos_class;
 260         update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
 261 }
 262 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 263
 264 /**
 265  * pm_qos_update_request - modifies an existing qos request
 266  * @pm_qos_req : handle to list element holding a pm_qos request to use
 267  * @value: defines the qos request
 268  *
 269  * Updates an existing qos request for the pm_qos_class of parameters along
 270  * with updating the target pm_qos_class value.
 271  *
 272  * Attempts are made to make this code callable on hot code paths.
 273  */
 274 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
 275                            s32 new_value)
 276 {
 277         s32 temp;
 278         struct pm_qos_object *o;
 279
 280         if (!pm_qos_req) /*guard against callers passing in null */
 281                 return;
 282
 283         if (!pm_qos_request_active(pm_qos_req)) {
 284                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 285                 return;
 286         }
 287
 288         o = pm_qos_array[pm_qos_req->pm_qos_class];
 289
 290         if (new_value == PM_QOS_DEFAULT_VALUE)
 291                 temp = o->default_value;
 292         else
 293                 temp = new_value;
 294
 295         if (temp != pm_qos_req->list.prio)
 296                 update_target(o, &pm_qos_req->list, 0, temp);
 297 }
 298 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 299
 300 /**
 301  * pm_qos_remove_request - modifies an existing qos request
 302  * @pm_qos_req: handle to request list element
 303  *
 304  * Will remove pm qos request from the list of requests and
 305  * recompute the current target value for the pm_qos_class.  Call this
 306  * on slow code paths.
 307  */
 308 void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
 309 {
 310         struct pm_qos_object *o;
 311
 312         if (pm_qos_req == NULL)
 313                 return;
 314                 /* silent return to keep pcm code cleaner */
 315
 316         if (!pm_qos_request_active(pm_qos_req)) {
 317                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 318                 return;
 319         }
 320
 321         o = pm_qos_array[pm_qos_req->pm_qos_class];
 322         update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
 323         memset(pm_qos_req, 0, sizeof(*pm_qos_req));
 324 }
 325 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 326
 327 /**
 328  * pm_qos_add_notifier - sets notification entry for changes to target value
 329  * @pm_qos_class: identifies which qos target changes should be notified.
 330  * @notifier: notifier block managed by caller.
 331  *
 332  * will register the notifier into a notification chain that gets called
 333  * upon changes to the pm_qos_class target value.
 334  */
 335 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 336 {
 337         int retval;
 338
 339         retval = blocking_notifier_chain_register(
 340                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 341
 342         return retval;
 343 }
 344 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 345
 346 /**
 347  * pm_qos_remove_notifier - deletes notification entry from chain.
 348  * @pm_qos_class: identifies which qos target changes are notified.
 349  * @notifier: notifier block to be removed.
 350  *
 351  * will remove the notifier from the notification chain that gets called
 352  * upon changes to the pm_qos_class target value.
 353  */
 354 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 355 {
 356         int retval;
 357
 358         retval = blocking_notifier_chain_unregister(
 359                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 360
 361         return retval;
 362 }
 363 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 364
 365 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 366 {
 367         long pm_qos_class;
 368
 369         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 370         if (pm_qos_class >= 0) {
 371                struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
 372                 if (!req)
 373                         return -ENOMEM;
 374
 375                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 376                 filp->private_data = req;
 377
 378                 if (filp->private_data)
 379                         return 0;
 380         }
 381         return -EPERM;
 382 }
 383
 384 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 385 {
 386         struct pm_qos_request_list *req;
 387
 388         req = filp->private_data;
 389         pm_qos_remove_request(req);
 390         kfree(req);
 391
 392         return 0;
 393 }
 394
 395
 396 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 397                 size_t count, loff_t *f_pos)
 398 {
 399         s32 value;
 400         unsigned long flags;
 401         struct pm_qos_object *o;
 402         struct pm_qos_request_list *pm_qos_req = filp->private_data;
 403
 404         if (!pm_qos_req)
 405                 return -EINVAL;
 406         if (!pm_qos_request_active(pm_qos_req))
 407                 return -EINVAL;
 408
 409         o = pm_qos_array[pm_qos_req->pm_qos_class];
 410         spin_lock_irqsave(&pm_qos_lock, flags);
 411         value = pm_qos_get_value(o);
 412         spin_unlock_irqrestore(&pm_qos_lock, flags);
 413
 414         return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 415 }
 416
 417 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 418                 size_t count, loff_t *f_pos)
 419 {
 420         s32 value;
 421         struct pm_qos_request_list *pm_qos_req;
 422
 423         if (count == sizeof(s32)) {
 424                 if (copy_from_user(&value, buf, sizeof(s32)))
 425                         return -EFAULT;
 426         } else if (count <= 11) { /* ASCII perhaps? */
 427                 char ascii_value[11];
 428                 unsigned long int ulval;
 429                 int ret;
 430
 431                 if (copy_from_user(ascii_value, buf, count))
 432                         return -EFAULT;
 433
 434                 if (count > 10) {
 435                         if (ascii_value[10] == '\n')
 436                                 ascii_value[10] = '\0';
 437                         else
 438                                 return -EINVAL;
 439                 } else {
 440                         ascii_value[count] = '\0';
 441                 }
 442                 ret = strict_strtoul(ascii_value, 16, &ulval);
 443                 if (ret) {
 444                         pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 445                         return -EINVAL;
 446                 }
 447                 value = (s32)lower_32_bits(ulval);
 448         } else {
 449                 return -EINVAL;
 450         }
 451
 452         pm_qos_req = filp->private_data;
 453         pm_qos_update_request(pm_qos_req, value);
 454
 455         return count;
 456 }
 457
 458
 459 static int __init pm_qos_power_init(void)
 460 {
 461         int ret = 0;
 462
 463         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 464         if (ret < 0) {
 465                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 466                 return ret;
 467         }
 468         ret = register_pm_qos_misc(&network_lat_pm_qos);
 469         if (ret < 0) {
 470                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 471                 return ret;
 472         }
 473         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 474         if (ret < 0)
 475                 printk(KERN_ERR
 476                         "pm_qos_param: network_throughput setup failed\n");
 477
 478         return ret;
 479 }
 480
 481 late_initcall(pm_qos_power_init);