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
  44 #include <linux/uaccess.h>
  45
  46 /*
  47  * locking rule: all changes to requests or notifiers lists
  48  * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
  49  * held, taken with _irqsave.  One lock to rule them all
  50  */
  51 enum pm_qos_type {
  52         PM_QOS_MAX,             /* return the largest value */
  53         PM_QOS_MIN              /* return the smallest value */
  54 };
  55
  56 struct pm_qos_object {
  57         struct plist_head requests;
  58         struct blocking_notifier_head *notifiers;
  59         struct miscdevice pm_qos_power_miscdev;
  60         char *name;
  61         s32 default_value;
  62         enum pm_qos_type type;
  63 };
  64
  65 static DEFINE_SPINLOCK(pm_qos_lock);
  66
  67 static struct pm_qos_object null_pm_qos;
  68 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  69 static struct pm_qos_object cpu_dma_pm_qos = {
  70         .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),
  71         .notifiers = &cpu_dma_lat_notifier,
  72         .name = "cpu_dma_latency",
  73         .default_value = 2000 * USEC_PER_SEC,
  74         .type = PM_QOS_MIN,
  75 };
  76
  77 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  78 static struct pm_qos_object network_lat_pm_qos = {
  79         .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),
  80         .notifiers = &network_lat_notifier,
  81         .name = "network_latency",
  82         .default_value = 2000 * USEC_PER_SEC,
  83         .type = PM_QOS_MIN
  84 };
  85
  86
  87 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  88 static struct pm_qos_object network_throughput_pm_qos = {
  89         .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
  90         .notifiers = &network_throughput_notifier,
  91         .name = "network_throughput",
  92         .default_value = 0,
  93         .type = PM_QOS_MAX,
  94 };
  95
  96
  97 static struct pm_qos_object *pm_qos_array[] = {
  98         &null_pm_qos,
  99         &cpu_dma_pm_qos,
 100         &network_lat_pm_qos,
 101         &network_throughput_pm_qos
 102 };
 103
 104 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 105                 size_t count, loff_t *f_pos);
 106 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 107 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 108
 109 static const struct file_operations pm_qos_power_fops = {
 110         .write = pm_qos_power_write,
 111         .open = pm_qos_power_open,
 112         .release = pm_qos_power_release,
 113         .llseek = noop_llseek,
 114 };
 115
 116 /* unlocked internal variant */
 117 static inline int pm_qos_get_value(struct pm_qos_object *o)
 118 {
 119         if (plist_head_empty(&o->requests))
 120                 return o->default_value;
 121
 122         switch (o->type) {
 123         case PM_QOS_MIN:
 124                 return plist_first(&o->requests)->prio;
 125
 126         case PM_QOS_MAX:
 127                 return plist_last(&o->requests)->prio;
 128
 129         default:
 130                 /* runtime check for not using enum */
 131                 BUG();
 132         }
 133 }
 134
 135 static void update_target(struct pm_qos_object *o, struct plist_node *node,
 136                           int del, int value)
 137 {
 138         unsigned long flags;
 139         int prev_value, curr_value;
 140
 141         spin_lock_irqsave(&pm_qos_lock, flags);
 142         prev_value = pm_qos_get_value(o);
 143         /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
 144         if (value != PM_QOS_DEFAULT_VALUE) {
 145                 /*
 146                  * to change the list, we atomically remove, reinit
 147                  * with new value and add, then see if the extremal
 148                  * changed
 149                  */
 150                 plist_del(node, &o->requests);
 151                 plist_node_init(node, value);
 152                 plist_add(node, &o->requests);
 153         } else if (del) {
 154                 plist_del(node, &o->requests);
 155         } else {
 156                 plist_add(node, &o->requests);
 157         }
 158         curr_value = pm_qos_get_value(o);
 159         spin_unlock_irqrestore(&pm_qos_lock, flags);
 160
 161         if (prev_value != curr_value)
 162                 blocking_notifier_call_chain(o->notifiers,
 163                                              (unsigned long)curr_value,
 164                                              NULL);
 165 }
 166
 167 static int register_pm_qos_misc(struct pm_qos_object *qos)
 168 {
 169         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 170         qos->pm_qos_power_miscdev.name = qos->name;
 171         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 172
 173         return misc_register(&qos->pm_qos_power_miscdev);
 174 }
 175
 176 static int find_pm_qos_object_by_minor(int minor)
 177 {
 178         int pm_qos_class;
 179
 180         for (pm_qos_class = 0;
 181                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 182                 if (minor ==
 183                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 184                         return pm_qos_class;
 185         }
 186         return -1;
 187 }
 188
 189 /**
 190  * pm_qos_request - returns current system wide qos expectation
 191  * @pm_qos_class: identification of which qos value is requested
 192  *
 193  * This function returns the current target value in an atomic manner.
 194  */
 195 int pm_qos_request(int pm_qos_class)
 196 {
 197         unsigned long flags;
 198         int value;
 199
 200         spin_lock_irqsave(&pm_qos_lock, flags);
 201         value = pm_qos_get_value(pm_qos_array[pm_qos_class]);
 202         spin_unlock_irqrestore(&pm_qos_lock, flags);
 203
 204         return value;
 205 }
 206 EXPORT_SYMBOL_GPL(pm_qos_request);
 207
 208 int pm_qos_request_active(struct pm_qos_request_list *req)
 209 {
 210         return req->pm_qos_class != 0;
 211 }
 212 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 213
 214 /**
 215  * pm_qos_add_request - inserts new qos request into the list
 216  * @dep: pointer to a preallocated handle
 217  * @pm_qos_class: identifies which list of qos request to use
 218  * @value: defines the qos request
 219  *
 220  * This function inserts a new entry in the pm_qos_class list of requested qos
 221  * performance characteristics.  It recomputes the aggregate QoS expectations
 222  * for the pm_qos_class of parameters and initializes the pm_qos_request_list
 223  * handle.  Caller needs to save this handle for later use in updates and
 224  * removal.
 225  */
 226
 227 void pm_qos_add_request(struct pm_qos_request_list *dep,
 228                         int pm_qos_class, s32 value)
 229 {
 230         struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
 231         int new_value;
 232
 233         if (pm_qos_request_active(dep)) {
 234                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 235                 return;
 236         }
 237         if (value == PM_QOS_DEFAULT_VALUE)
 238                 new_value = o->default_value;
 239         else
 240                 new_value = value;
 241         plist_node_init(&dep->list, new_value);
 242         dep->pm_qos_class = pm_qos_class;
 243         update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
 244 }
 245 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 246
 247 /**
 248  * pm_qos_update_request - modifies an existing qos request
 249  * @pm_qos_req : handle to list element holding a pm_qos request to use
 250  * @value: defines the qos request
 251  *
 252  * Updates an existing qos request for the pm_qos_class of parameters along
 253  * with updating the target pm_qos_class value.
 254  *
 255  * Attempts are made to make this code callable on hot code paths.
 256  */
 257 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
 258                            s32 new_value)
 259 {
 260         s32 temp;
 261         struct pm_qos_object *o;
 262
 263         if (!pm_qos_req) /*guard against callers passing in null */
 264                 return;
 265
 266         if (!pm_qos_request_active(pm_qos_req)) {
 267                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 268                 return;
 269         }
 270
 271         o = pm_qos_array[pm_qos_req->pm_qos_class];
 272
 273         if (new_value == PM_QOS_DEFAULT_VALUE)
 274                 temp = o->default_value;
 275         else
 276                 temp = new_value;
 277
 278         if (temp != pm_qos_req->list.prio)
 279                 update_target(o, &pm_qos_req->list, 0, temp);
 280 }
 281 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 282
 283 /**
 284  * pm_qos_remove_request - modifies an existing qos request
 285  * @pm_qos_req: handle to request list element
 286  *
 287  * Will remove pm qos request from the list of requests and
 288  * recompute the current target value for the pm_qos_class.  Call this
 289  * on slow code paths.
 290  */
 291 void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
 292 {
 293         struct pm_qos_object *o;
 294
 295         if (pm_qos_req == NULL)
 296                 return;
 297                 /* silent return to keep pcm code cleaner */
 298
 299         if (!pm_qos_request_active(pm_qos_req)) {
 300                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 301                 return;
 302         }
 303
 304         o = pm_qos_array[pm_qos_req->pm_qos_class];
 305         update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
 306         memset(pm_qos_req, 0, sizeof(*pm_qos_req));
 307 }
 308 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 309
 310 /**
 311  * pm_qos_add_notifier - sets notification entry for changes to target value
 312  * @pm_qos_class: identifies which qos target changes should be notified.
 313  * @notifier: notifier block managed by caller.
 314  *
 315  * will register the notifier into a notification chain that gets called
 316  * upon changes to the pm_qos_class target value.
 317  */
 318 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 319 {
 320         int retval;
 321
 322         retval = blocking_notifier_chain_register(
 323                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 324
 325         return retval;
 326 }
 327 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 328
 329 /**
 330  * pm_qos_remove_notifier - deletes notification entry from chain.
 331  * @pm_qos_class: identifies which qos target changes are notified.
 332  * @notifier: notifier block to be removed.
 333  *
 334  * will remove the notifier from the notification chain that gets called
 335  * upon changes to the pm_qos_class target value.
 336  */
 337 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 338 {
 339         int retval;
 340
 341         retval = blocking_notifier_chain_unregister(
 342                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 343
 344         return retval;
 345 }
 346 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 347
 348 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 349 {
 350         long pm_qos_class;
 351
 352         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 353         if (pm_qos_class >= 0) {
 354                struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
 355                 if (!req)
 356                         return -ENOMEM;
 357
 358                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 359                 filp->private_data = req;
 360
 361                 if (filp->private_data)
 362                         return 0;
 363         }
 364         return -EPERM;
 365 }
 366
 367 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 368 {
 369         struct pm_qos_request_list *req;
 370
 371         req = filp->private_data;
 372         pm_qos_remove_request(req);
 373         kfree(req);
 374
 375         return 0;
 376 }
 377
 378
 379 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 380                 size_t count, loff_t *f_pos)
 381 {
 382         s32 value;
 383         int x;
 384         char ascii_value[11];
 385         struct pm_qos_request_list *pm_qos_req;
 386
 387         if (count == sizeof(s32)) {
 388                 if (copy_from_user(&value, buf, sizeof(s32)))
 389                         return -EFAULT;
 390         } else if (count == 11) { /* len('0x12345678/0') */
 391                 if (copy_from_user(ascii_value, buf, 11))
 392                         return -EFAULT;
 393                 if (strlen(ascii_value) != 10)
 394                         return -EINVAL;
 395                 x = sscanf(ascii_value, "%x", &value);
 396                 if (x != 1)
 397                         return -EINVAL;
 398                 pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
 399         } else
 400                 return -EINVAL;
 401
 402         pm_qos_req = filp->private_data;
 403         pm_qos_update_request(pm_qos_req, value);
 404
 405         return count;
 406 }
 407
 408
 409 static int __init pm_qos_power_init(void)
 410 {
 411         int ret = 0;
 412
 413         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 414         if (ret < 0) {
 415                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 416                 return ret;
 417         }
 418         ret = register_pm_qos_misc(&network_lat_pm_qos);
 419         if (ret < 0) {
 420                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 421                 return ret;
 422         }
 423         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 424         if (ret < 0)
 425                 printk(KERN_ERR
 426                         "pm_qos_param: network_throughput setup failed\n");
 427
 428         return ret;
 429 }
 430
 431 late_initcall(pm_qos_power_init);