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 ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 107                 size_t count, loff_t *f_pos);
 108 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 109 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 110
 111 static const struct file_operations pm_qos_power_fops = {
 112         .write = pm_qos_power_write,
 113         .read = pm_qos_power_read,
 114         .open = pm_qos_power_open,
 115         .release = pm_qos_power_release,
 116         .llseek = noop_llseek,
 117 };
 118
 119 /* unlocked internal variant */
 120 static inline int pm_qos_get_value(struct pm_qos_object *o)
 121 {
 122         if (plist_head_empty(&o->requests))
 123                 return o->default_value;
 124
 125         switch (o->type) {
 126         case PM_QOS_MIN:
 127                 return plist_first(&o->requests)->prio;
 128
 129         case PM_QOS_MAX:
 130                 return plist_last(&o->requests)->prio;
 131
 132         default:
 133                 /* runtime check for not using enum */
 134                 BUG();
 135         }
 136 }
 137
 138 static void update_target(struct pm_qos_object *o, struct plist_node *node,
 139                           int del, int value)
 140 {
 141         unsigned long flags;
 142         int prev_value, curr_value;
 143
 144         spin_lock_irqsave(&pm_qos_lock, flags);
 145         prev_value = pm_qos_get_value(o);
 146         /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
 147         if (value != PM_QOS_DEFAULT_VALUE) {
 148                 /*
 149                  * to change the list, we atomically remove, reinit
 150                  * with new value and add, then see if the extremal
 151                  * changed
 152                  */
 153                 plist_del(node, &o->requests);
 154                 plist_node_init(node, value);
 155                 plist_add(node, &o->requests);
 156         } else if (del) {
 157                 plist_del(node, &o->requests);
 158         } else {
 159                 plist_add(node, &o->requests);
 160         }
 161         curr_value = pm_qos_get_value(o);
 162         spin_unlock_irqrestore(&pm_qos_lock, flags);
 163
 164         if (prev_value != curr_value)
 165                 blocking_notifier_call_chain(o->notifiers,
 166                                              (unsigned long)curr_value,
 167                                              NULL);
 168 }
 169
 170 static int register_pm_qos_misc(struct pm_qos_object *qos)
 171 {
 172         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 173         qos->pm_qos_power_miscdev.name = qos->name;
 174         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 175
 176         return misc_register(&qos->pm_qos_power_miscdev);
 177 }
 178
 179 static int find_pm_qos_object_by_minor(int minor)
 180 {
 181         int pm_qos_class;
 182
 183         for (pm_qos_class = 0;
 184                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 185                 if (minor ==
 186                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 187                         return pm_qos_class;
 188         }
 189         return -1;
 190 }
 191
 192 /**
 193  * pm_qos_request - returns current system wide qos expectation
 194  * @pm_qos_class: identification of which qos value is requested
 195  *
 196  * This function returns the current target value in an atomic manner.
 197  */
 198 int pm_qos_request(int pm_qos_class)
 199 {
 200         unsigned long flags;
 201         int value;
 202
 203         spin_lock_irqsave(&pm_qos_lock, flags);
 204         value = pm_qos_get_value(pm_qos_array[pm_qos_class]);
 205         spin_unlock_irqrestore(&pm_qos_lock, flags);
 206
 207         return value;
 208 }
 209 EXPORT_SYMBOL_GPL(pm_qos_request);
 210
 211 int pm_qos_request_active(struct pm_qos_request_list *req)
 212 {
 213         return req->pm_qos_class != 0;
 214 }
 215 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 216
 217 /**
 218  * pm_qos_add_request - inserts new qos request into the list
 219  * @dep: pointer to a preallocated handle
 220  * @pm_qos_class: identifies which list of qos request to use
 221  * @value: defines the qos request
 222  *
 223  * This function inserts a new entry in the pm_qos_class list of requested qos
 224  * performance characteristics.  It recomputes the aggregate QoS expectations
 225  * for the pm_qos_class of parameters and initializes the pm_qos_request_list
 226  * handle.  Caller needs to save this handle for later use in updates and
 227  * removal.
 228  */
 229
 230 void pm_qos_add_request(struct pm_qos_request_list *dep,
 231                         int pm_qos_class, s32 value)
 232 {
 233         struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
 234         int new_value;
 235
 236         if (pm_qos_request_active(dep)) {
 237                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 238                 return;
 239         }
 240         if (value == PM_QOS_DEFAULT_VALUE)
 241                 new_value = o->default_value;
 242         else
 243                 new_value = value;
 244         plist_node_init(&dep->list, new_value);
 245         dep->pm_qos_class = pm_qos_class;
 246         update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
 247 }
 248 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 249
 250 /**
 251  * pm_qos_update_request - modifies an existing qos request
 252  * @pm_qos_req : handle to list element holding a pm_qos request to use
 253  * @value: defines the qos request
 254  *
 255  * Updates an existing qos request for the pm_qos_class of parameters along
 256  * with updating the target pm_qos_class value.
 257  *
 258  * Attempts are made to make this code callable on hot code paths.
 259  */
 260 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
 261                            s32 new_value)
 262 {
 263         s32 temp;
 264         struct pm_qos_object *o;
 265
 266         if (!pm_qos_req) /*guard against callers passing in null */
 267                 return;
 268
 269         if (!pm_qos_request_active(pm_qos_req)) {
 270                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 271                 return;
 272         }
 273
 274         o = pm_qos_array[pm_qos_req->pm_qos_class];
 275
 276         if (new_value == PM_QOS_DEFAULT_VALUE)
 277                 temp = o->default_value;
 278         else
 279                 temp = new_value;
 280
 281         if (temp != pm_qos_req->list.prio)
 282                 update_target(o, &pm_qos_req->list, 0, temp);
 283 }
 284 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 285
 286 /**
 287  * pm_qos_remove_request - modifies an existing qos request
 288  * @pm_qos_req: handle to request list element
 289  *
 290  * Will remove pm qos request from the list of requests and
 291  * recompute the current target value for the pm_qos_class.  Call this
 292  * on slow code paths.
 293  */
 294 void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
 295 {
 296         struct pm_qos_object *o;
 297
 298         if (pm_qos_req == NULL)
 299                 return;
 300                 /* silent return to keep pcm code cleaner */
 301
 302         if (!pm_qos_request_active(pm_qos_req)) {
 303                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 304                 return;
 305         }
 306
 307         o = pm_qos_array[pm_qos_req->pm_qos_class];
 308         update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
 309         memset(pm_qos_req, 0, sizeof(*pm_qos_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]->notifiers, notifier);
 327
 328         return retval;
 329 }
 330 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 331
 332 /**
 333  * pm_qos_remove_notifier - deletes notification entry from chain.
 334  * @pm_qos_class: identifies which qos target changes are notified.
 335  * @notifier: notifier block to be removed.
 336  *
 337  * will remove the notifier from the notification chain that gets called
 338  * upon changes to the pm_qos_class target value.
 339  */
 340 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 341 {
 342         int retval;
 343
 344         retval = blocking_notifier_chain_unregister(
 345                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 346
 347         return retval;
 348 }
 349 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 350
 351 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 352 {
 353         long pm_qos_class;
 354
 355         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 356         if (pm_qos_class >= 0) {
 357                struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
 358                 if (!req)
 359                         return -ENOMEM;
 360
 361                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 362                 filp->private_data = req;
 363
 364                 if (filp->private_data)
 365                         return 0;
 366         }
 367         return -EPERM;
 368 }
 369
 370 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 371 {
 372         struct pm_qos_request_list *req;
 373
 374         req = filp->private_data;
 375         pm_qos_remove_request(req);
 376         kfree(req);
 377
 378         return 0;
 379 }
 380
 381
 382 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf,
 383                 size_t count, loff_t *f_pos)
 384 {
 385         s32 value;
 386         unsigned long flags;
 387         struct pm_qos_object *o;
 388         struct pm_qos_request_list *pm_qos_req = filp->private_data;;
 389
 390         if (!pm_qos_req)
 391                 return -EINVAL;
 392         if (!pm_qos_request_active(pm_qos_req))
 393                 return -EINVAL;
 394
 395         o = pm_qos_array[pm_qos_req->pm_qos_class];
 396         spin_lock_irqsave(&pm_qos_lock, flags);
 397         value = pm_qos_get_value(o);
 398         spin_unlock_irqrestore(&pm_qos_lock, flags);
 399
 400         return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32));
 401 }
 402
 403 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 404                 size_t count, loff_t *f_pos)
 405 {
 406         s32 value;
 407         int x;
 408         char ascii_value[11];
 409         struct pm_qos_request_list *pm_qos_req;
 410
 411         if (count == sizeof(s32)) {
 412                 if (copy_from_user(&value, buf, sizeof(s32)))
 413                         return -EFAULT;
 414         } else if (count == 11) { /* len('0x12345678/0') */
 415                 if (copy_from_user(ascii_value, buf, 11))
 416                         return -EFAULT;
 417                 if (strlen(ascii_value) != 10)
 418                         return -EINVAL;
 419                 x = sscanf(ascii_value, "%x", &value);
 420                 if (x != 1)
 421                         return -EINVAL;
 422                 pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
 423         } else
 424                 return -EINVAL;
 425
 426         pm_qos_req = filp->private_data;
 427         pm_qos_update_request(pm_qos_req, value);
 428
 429         return count;
 430 }
 431
 432
 433 static int __init pm_qos_power_init(void)
 434 {
 435         int ret = 0;
 436
 437         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 438         if (ret < 0) {
 439                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 440                 return ret;
 441         }
 442         ret = register_pm_qos_misc(&network_lat_pm_qos);
 443         if (ret < 0) {
 444                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 445                 return ret;
 446         }
 447         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 448         if (ret < 0)
 449                 printk(KERN_ERR
 450                         "pm_qos_param: network_throughput setup failed\n");
 451
 452         return ret;
 453 }
 454
 455 late_initcall(pm_qos_power_init);