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 struct pm_qos_object {
  58         struct plist_head requests;
  59         struct blocking_notifier_head *notifiers;
  60         struct miscdevice pm_qos_power_miscdev;
  61         char *name;
  62         s32 default_value;
  63         enum pm_qos_type type;
  64 };
  65
  66 static DEFINE_SPINLOCK(pm_qos_lock);
  67
  68 static struct pm_qos_object null_pm_qos;
  69 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  70 static struct pm_qos_object cpu_dma_pm_qos = {
  71         .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),
  72         .notifiers = &cpu_dma_lat_notifier,
  73         .name = "cpu_dma_latency",
  74         .default_value = 2000 * USEC_PER_SEC,
  75         .type = PM_QOS_MIN,
  76 };
  77
  78 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  79 static struct pm_qos_object network_lat_pm_qos = {
  80         .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),
  81         .notifiers = &network_lat_notifier,
  82         .name = "network_latency",
  83         .default_value = 2000 * USEC_PER_SEC,
  84         .type = PM_QOS_MIN
  85 };
  86
  87
  88 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  89 static struct pm_qos_object network_throughput_pm_qos = {
  90         .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
  91         .notifiers = &network_throughput_notifier,
  92         .name = "network_throughput",
  93         .default_value = 0,
  94         .type = PM_QOS_MAX,
  95 };
  96
  97
  98 static struct pm_qos_object *pm_qos_array[] = {
  99         &null_pm_qos,
 100         &cpu_dma_pm_qos,
 101         &network_lat_pm_qos,
 102         &network_throughput_pm_qos
 103 };
 104
 105 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 106                 size_t count, loff_t *f_pos);
 107 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 108                 size_t count, loff_t *f_pos);
 109 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 110 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 111
 112 static const struct file_operations pm_qos_power_fops = {
 113         .write = pm_qos_power_write,
 114         .read = pm_qos_power_read,
 115         .open = pm_qos_power_open,
 116         .release = pm_qos_power_release,
 117         .llseek = noop_llseek,
 118 };
 119
 120 /* unlocked internal variant */
 121 static inline int pm_qos_get_value(struct pm_qos_object *o)
 122 {
 123         if (plist_head_empty(&o->requests))
 124                 return o->default_value;
 125
 126         switch (o->type) {
 127         case PM_QOS_MIN:
 128                 return plist_first(&o->requests)->prio;
 129
 130         case PM_QOS_MAX:
 131                 return plist_last(&o->requests)->prio;
 132
 133         default:
 134                 /* runtime check for not using enum */
 135                 BUG();
 136         }
 137 }
 138
 139 static void update_target(struct pm_qos_object *o, struct plist_node *node,
 140                           int del, int value)
 141 {
 142         unsigned long flags;
 143         int prev_value, curr_value;
 144
 145         spin_lock_irqsave(&pm_qos_lock, flags);
 146         prev_value = pm_qos_get_value(o);
 147         /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
 148         if (value != PM_QOS_DEFAULT_VALUE) {
 149                 /*
 150                  * to change the list, we atomically remove, reinit
 151                  * with new value and add, then see if the extremal
 152                  * changed
 153                  */
 154                 plist_del(node, &o->requests);
 155                 plist_node_init(node, value);
 156                 plist_add(node, &o->requests);
 157         } else if (del) {
 158                 plist_del(node, &o->requests);
 159         } else {
 160                 plist_add(node, &o->requests);
 161         }
 162         curr_value = pm_qos_get_value(o);
 163         spin_unlock_irqrestore(&pm_qos_lock, flags);
 164
 165         if (prev_value != curr_value)
 166                 blocking_notifier_call_chain(o->notifiers,
 167                                              (unsigned long)curr_value,
 168                                              NULL);
 169 }
 170
 171 static int register_pm_qos_misc(struct pm_qos_object *qos)
 172 {
 173         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 174         qos->pm_qos_power_miscdev.name = qos->name;
 175         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 176
 177         return misc_register(&qos->pm_qos_power_miscdev);
 178 }
 179
 180 static int find_pm_qos_object_by_minor(int minor)
 181 {
 182         int pm_qos_class;
 183
 184         for (pm_qos_class = 0;
 185                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 186                 if (minor ==
 187                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 188                         return pm_qos_class;
 189         }
 190         return -1;
 191 }
 192
 193 /**
 194  * pm_qos_request - returns current system wide qos expectation
 195  * @pm_qos_class: identification of which qos value is requested
 196  *
 197  * This function returns the current target value in an atomic manner.
 198  */
 199 int pm_qos_request(int pm_qos_class)
 200 {
 201         unsigned long flags;
 202         int value;
 203
 204         spin_lock_irqsave(&pm_qos_lock, flags);
 205         value = pm_qos_get_value(pm_qos_array[pm_qos_class]);
 206         spin_unlock_irqrestore(&pm_qos_lock, flags);
 207
 208         return value;
 209 }
 210 EXPORT_SYMBOL_GPL(pm_qos_request);
 211
 212 int pm_qos_request_active(struct pm_qos_request_list *req)
 213 {
 214         return req->pm_qos_class != 0;
 215 }
 216 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 217
 218 /**
 219  * pm_qos_add_request - inserts new qos request into the list
 220  * @dep: pointer to a preallocated handle
 221  * @pm_qos_class: identifies which list of qos request to use
 222  * @value: defines the qos request
 223  *
 224  * This function inserts a new entry in the pm_qos_class list of requested qos
 225  * performance characteristics.  It recomputes the aggregate QoS expectations
 226  * for the pm_qos_class of parameters and initializes the pm_qos_request_list
 227  * handle.  Caller needs to save this handle for later use in updates and
 228  * removal.
 229  */
 230
 231 void pm_qos_add_request(struct pm_qos_request_list *dep,
 232                         int pm_qos_class, s32 value)
 233 {
 234         struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
 235         int new_value;
 236
 237         if (pm_qos_request_active(dep)) {
 238                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 239                 return;
 240         }
 241         if (value == PM_QOS_DEFAULT_VALUE)
 242                 new_value = o->default_value;
 243         else
 244                 new_value = value;
 245         plist_node_init(&dep->list, new_value);
 246         dep->pm_qos_class = pm_qos_class;
 247         update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
 248 }
 249 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 250
 251 /**
 252  * pm_qos_update_request - modifies an existing qos request
 253  * @pm_qos_req : handle to list element holding a pm_qos request to use
 254  * @value: defines the qos request
 255  *
 256  * Updates an existing qos request for the pm_qos_class of parameters along
 257  * with updating the target pm_qos_class value.
 258  *
 259  * Attempts are made to make this code callable on hot code paths.
 260  */
 261 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
 262                            s32 new_value)
 263 {
 264         s32 temp;
 265         struct pm_qos_object *o;
 266
 267         if (!pm_qos_req) /*guard against callers passing in null */
 268                 return;
 269
 270         if (!pm_qos_request_active(pm_qos_req)) {
 271                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 272                 return;
 273         }
 274
 275         o = pm_qos_array[pm_qos_req->pm_qos_class];
 276
 277         if (new_value == PM_QOS_DEFAULT_VALUE)
 278                 temp = o->default_value;
 279         else
 280                 temp = new_value;
 281
 282         if (temp != pm_qos_req->list.prio)
 283                 update_target(o, &pm_qos_req->list, 0, temp);
 284 }
 285 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 286
 287 /**
 288  * pm_qos_remove_request - modifies an existing qos request
 289  * @pm_qos_req: handle to request list element
 290  *
 291  * Will remove pm qos request from the list of requests 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_list *pm_qos_req)
 296 {
 297         struct pm_qos_object *o;
 298
 299         if (pm_qos_req == NULL)
 300                 return;
 301                 /* silent return to keep pcm code cleaner */
 302
 303         if (!pm_qos_request_active(pm_qos_req)) {
 304                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 305                 return;
 306         }
 307
 308         o = pm_qos_array[pm_qos_req->pm_qos_class];
 309         update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
 310         memset(pm_qos_req, 0, sizeof(*pm_qos_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]->notifiers, 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]->notifiers, notifier);
 347
 348         return retval;
 349 }
 350 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 351
 352 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 353 {
 354         long pm_qos_class;
 355
 356         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 357         if (pm_qos_class >= 0) {
 358                struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
 359                 if (!req)
 360                         return -ENOMEM;
 361
 362                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 363                 filp->private_data = req;
 364
 365                 if (filp->private_data)
 366                         return 0;
 367         }
 368         return -EPERM;
 369 }
 370
 371 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 372 {
 373         struct pm_qos_request_list *req;
 374
 375         req = filp->private_data;
 376         pm_qos_remove_request(req);
 377         kfree(req);
 378
 379         return 0;
 380 }
 381
 382
 383 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 384                 size_t count, loff_t *f_pos)
 385 {
 386         s32 value;
 387         unsigned long flags;
 388         struct pm_qos_object *o;
 389         struct pm_qos_request_list *pm_qos_req = filp->private_data;
 390
 391         if (!pm_qos_req)
 392                 return -EINVAL;
 393         if (!pm_qos_request_active(pm_qos_req))
 394                 return -EINVAL;
 395
 396         o = pm_qos_array[pm_qos_req->pm_qos_class];
 397         spin_lock_irqsave(&pm_qos_lock, flags);
 398         value = pm_qos_get_value(o);
 399         spin_unlock_irqrestore(&pm_qos_lock, flags);
 400
 401         return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 402 }
 403
 404 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 405                 size_t count, loff_t *f_pos)
 406 {
 407         s32 value;
 408         struct pm_qos_request_list *pm_qos_req;
 409
 410         if (count == sizeof(s32)) {
 411                 if (copy_from_user(&value, buf, sizeof(s32)))
 412                         return -EFAULT;
 413         } else if (count <= 11) { /* ASCII perhaps? */
 414                 char ascii_value[11];
 415                 unsigned long int ulval;
 416                 int ret;
 417
 418                 if (copy_from_user(ascii_value, buf, count))
 419                         return -EFAULT;
 420
 421                 if (count > 10) {
 422                         if (ascii_value[10] == '\n')
 423                                 ascii_value[10] = '\0';
 424                         else
 425                                 return -EINVAL;
 426                 } else {
 427                         ascii_value[count] = '\0';
 428                 }
 429                 ret = strict_strtoul(ascii_value, 16, &ulval);
 430                 if (ret) {
 431                         pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret);
 432                         return -EINVAL;
 433                 }
 434                 value = (s32)lower_32_bits(ulval);
 435         } else {
 436                 return -EINVAL;
 437         }
 438
 439         pm_qos_req = filp->private_data;
 440         pm_qos_update_request(pm_qos_req, value);
 441
 442         return count;
 443 }
 444
 445
 446 static int __init pm_qos_power_init(void)
 447 {
 448         int ret = 0;
 449
 450         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 451         if (ret < 0) {
 452                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 453                 return ret;
 454         }
 455         ret = register_pm_qos_misc(&network_lat_pm_qos);
 456         if (ret < 0) {
 457                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 458                 return ret;
 459         }
 460         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 461         if (ret < 0)
 462                 printk(KERN_ERR
 463                         "pm_qos_param: network_throughput setup failed\n");
 464
 465         return ret;
 466 }
 467
 468 late_initcall(pm_qos_power_init);