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