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 /*
  57  * Note: The lockless read path depends on the CPU accessing
  58  * target_value atomically.  Atomic access is only guaranteed on all CPU
  59  * types linux supports for 32 bit quantites
  60  */
  61 struct pm_qos_object {
  62         struct plist_head requests;
  63         struct blocking_notifier_head *notifiers;
  64         struct miscdevice pm_qos_power_miscdev;
  65         char *name;
  66         s32 target_value;       /* Do not change to 64 bit */
  67         s32 default_value;
  68         enum pm_qos_type type;
  69 };
  70
  71 static DEFINE_SPINLOCK(pm_qos_lock);
  72
  73 static struct pm_qos_object null_pm_qos;
  74 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  75 static struct pm_qos_object cpu_dma_pm_qos = {
  76         .requests = PLIST_HEAD_INIT(cpu_dma_pm_qos.requests, pm_qos_lock),
  77         .notifiers = &cpu_dma_lat_notifier,
  78         .name = "cpu_dma_latency",
  79         .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  80         .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE,
  81         .type = PM_QOS_MIN,
  82 };
  83
  84 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  85 static struct pm_qos_object network_lat_pm_qos = {
  86         .requests = PLIST_HEAD_INIT(network_lat_pm_qos.requests, pm_qos_lock),
  87         .notifiers = &network_lat_notifier,
  88         .name = "network_latency",
  89         .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  90         .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE,
  91         .type = PM_QOS_MIN
  92 };
  93
  94
  95 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  96 static struct pm_qos_object network_throughput_pm_qos = {
  97         .requests = PLIST_HEAD_INIT(network_throughput_pm_qos.requests, pm_qos_lock),
  98         .notifiers = &network_throughput_notifier,
  99         .name = "network_throughput",
 100         .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
 101         .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE,
 102         .type = PM_QOS_MAX,
 103 };
 104
 105
 106 static struct pm_qos_object *pm_qos_array[] = {
 107         &null_pm_qos,
 108         &cpu_dma_pm_qos,
 109         &network_lat_pm_qos,
 110         &network_throughput_pm_qos
 111 };
 112
 113 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 114                 size_t count, loff_t *f_pos);
 115 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 116 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 117
 118 static const struct file_operations pm_qos_power_fops = {
 119         .write = pm_qos_power_write,
 120         .open = pm_qos_power_open,
 121         .release = pm_qos_power_release,
 122         .llseek = noop_llseek,
 123 };
 124
 125 /* unlocked internal variant */
 126 static inline int pm_qos_get_value(struct pm_qos_object *o)
 127 {
 128         if (plist_head_empty(&o->requests))
 129                 return o->default_value;
 130
 131         switch (o->type) {
 132         case PM_QOS_MIN:
 133                 return plist_first(&o->requests)->prio;
 134
 135         case PM_QOS_MAX:
 136                 return plist_last(&o->requests)->prio;
 137
 138         default:
 139                 /* runtime check for not using enum */
 140                 BUG();
 141         }
 142 }
 143
 144 static inline s32 pm_qos_read_value(struct pm_qos_object *o)
 145 {
 146         return o->target_value;
 147 }
 148
 149 static inline void pm_qos_set_value(struct pm_qos_object *o, s32 value)
 150 {
 151         o->target_value = value;
 152 }
 153
 154 static void update_target(struct pm_qos_object *o, struct plist_node *node,
 155                           int del, int value)
 156 {
 157         unsigned long flags;
 158         int prev_value, curr_value;
 159
 160         spin_lock_irqsave(&pm_qos_lock, flags);
 161         prev_value = pm_qos_get_value(o);
 162         /* PM_QOS_DEFAULT_VALUE is a signal that the value is unchanged */
 163         if (value != PM_QOS_DEFAULT_VALUE) {
 164                 /*
 165                  * to change the list, we atomically remove, reinit
 166                  * with new value and add, then see if the extremal
 167                  * changed
 168                  */
 169                 plist_del(node, &o->requests);
 170                 plist_node_init(node, value);
 171                 plist_add(node, &o->requests);
 172         } else if (del) {
 173                 plist_del(node, &o->requests);
 174         } else {
 175                 plist_add(node, &o->requests);
 176         }
 177         curr_value = pm_qos_get_value(o);
 178         pm_qos_set_value(o, curr_value);
 179         spin_unlock_irqrestore(&pm_qos_lock, flags);
 180
 181         if (prev_value != curr_value)
 182                 blocking_notifier_call_chain(o->notifiers,
 183                                              (unsigned long)curr_value,
 184                                              NULL);
 185 }
 186
 187 static int register_pm_qos_misc(struct pm_qos_object *qos)
 188 {
 189         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 190         qos->pm_qos_power_miscdev.name = qos->name;
 191         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 192
 193         return misc_register(&qos->pm_qos_power_miscdev);
 194 }
 195
 196 static int find_pm_qos_object_by_minor(int minor)
 197 {
 198         int pm_qos_class;
 199
 200         for (pm_qos_class = 0;
 201                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 202                 if (minor ==
 203                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 204                         return pm_qos_class;
 205         }
 206         return -1;
 207 }
 208
 209 /**
 210  * pm_qos_request - returns current system wide qos expectation
 211  * @pm_qos_class: identification of which qos value is requested
 212  *
 213  * This function returns the current target value.
 214  */
 215 int pm_qos_request(int pm_qos_class)
 216 {
 217         return pm_qos_read_value(pm_qos_array[pm_qos_class]);
 218 }
 219 EXPORT_SYMBOL_GPL(pm_qos_request);
 220
 221 int pm_qos_request_active(struct pm_qos_request_list *req)
 222 {
 223         return req->pm_qos_class != 0;
 224 }
 225 EXPORT_SYMBOL_GPL(pm_qos_request_active);
 226
 227 /**
 228  * pm_qos_add_request - inserts new qos request into the list
 229  * @dep: pointer to a preallocated handle
 230  * @pm_qos_class: identifies which list of qos request to use
 231  * @value: defines the qos request
 232  *
 233  * This function inserts a new entry in the pm_qos_class list of requested qos
 234  * performance characteristics.  It recomputes the aggregate QoS expectations
 235  * for the pm_qos_class of parameters and initializes the pm_qos_request_list
 236  * handle.  Caller needs to save this handle for later use in updates and
 237  * removal.
 238  */
 239
 240 void pm_qos_add_request(struct pm_qos_request_list *dep,
 241                         int pm_qos_class, s32 value)
 242 {
 243         struct pm_qos_object *o =  pm_qos_array[pm_qos_class];
 244         int new_value;
 245
 246         if (pm_qos_request_active(dep)) {
 247                 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n");
 248                 return;
 249         }
 250         if (value == PM_QOS_DEFAULT_VALUE)
 251                 new_value = o->default_value;
 252         else
 253                 new_value = value;
 254         plist_node_init(&dep->list, new_value);
 255         dep->pm_qos_class = pm_qos_class;
 256         update_target(o, &dep->list, 0, PM_QOS_DEFAULT_VALUE);
 257 }
 258 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 259
 260 /**
 261  * pm_qos_update_request - modifies an existing qos request
 262  * @pm_qos_req : handle to list element holding a pm_qos request to use
 263  * @value: defines the qos request
 264  *
 265  * Updates an existing qos request for the pm_qos_class of parameters along
 266  * with updating the target pm_qos_class value.
 267  *
 268  * Attempts are made to make this code callable on hot code paths.
 269  */
 270 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
 271                            s32 new_value)
 272 {
 273         s32 temp;
 274         struct pm_qos_object *o;
 275
 276         if (!pm_qos_req) /*guard against callers passing in null */
 277                 return;
 278
 279         if (!pm_qos_request_active(pm_qos_req)) {
 280                 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n");
 281                 return;
 282         }
 283
 284         o = pm_qos_array[pm_qos_req->pm_qos_class];
 285
 286         if (new_value == PM_QOS_DEFAULT_VALUE)
 287                 temp = o->default_value;
 288         else
 289                 temp = new_value;
 290
 291         if (temp != pm_qos_req->list.prio)
 292                 update_target(o, &pm_qos_req->list, 0, temp);
 293 }
 294 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 295
 296 /**
 297  * pm_qos_remove_request - modifies an existing qos request
 298  * @pm_qos_req: handle to request list element
 299  *
 300  * Will remove pm qos request from the list of requests and
 301  * recompute the current target value for the pm_qos_class.  Call this
 302  * on slow code paths.
 303  */
 304 void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
 305 {
 306         struct pm_qos_object *o;
 307
 308         if (pm_qos_req == NULL)
 309                 return;
 310                 /* silent return to keep pcm code cleaner */
 311
 312         if (!pm_qos_request_active(pm_qos_req)) {
 313                 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n");
 314                 return;
 315         }
 316
 317         o = pm_qos_array[pm_qos_req->pm_qos_class];
 318         update_target(o, &pm_qos_req->list, 1, PM_QOS_DEFAULT_VALUE);
 319         memset(pm_qos_req, 0, sizeof(*pm_qos_req));
 320 }
 321 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 322
 323 /**
 324  * pm_qos_add_notifier - sets notification entry for changes to target value
 325  * @pm_qos_class: identifies which qos target changes should be notified.
 326  * @notifier: notifier block managed by caller.
 327  *
 328  * will register the notifier into a notification chain that gets called
 329  * upon changes to the pm_qos_class target value.
 330  */
 331 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 332 {
 333         int retval;
 334
 335         retval = blocking_notifier_chain_register(
 336                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 337
 338         return retval;
 339 }
 340 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 341
 342 /**
 343  * pm_qos_remove_notifier - deletes notification entry from chain.
 344  * @pm_qos_class: identifies which qos target changes are notified.
 345  * @notifier: notifier block to be removed.
 346  *
 347  * will remove the notifier from the notification chain that gets called
 348  * upon changes to the pm_qos_class target value.
 349  */
 350 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 351 {
 352         int retval;
 353
 354         retval = blocking_notifier_chain_unregister(
 355                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 356
 357         return retval;
 358 }
 359 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 360
 361 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 362 {
 363         long pm_qos_class;
 364
 365         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 366         if (pm_qos_class >= 0) {
 367                struct pm_qos_request_list *req = kzalloc(sizeof(*req), GFP_KERNEL);
 368                 if (!req)
 369                         return -ENOMEM;
 370
 371                 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE);
 372                 filp->private_data = req;
 373
 374                 if (filp->private_data)
 375                         return 0;
 376         }
 377         return -EPERM;
 378 }
 379
 380 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 381 {
 382         struct pm_qos_request_list *req;
 383
 384         req = filp->private_data;
 385         pm_qos_remove_request(req);
 386         kfree(req);
 387
 388         return 0;
 389 }
 390
 391
 392 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 393                 size_t count, loff_t *f_pos)
 394 {
 395         s32 value;
 396         int x;
 397         char ascii_value[11];
 398         struct pm_qos_request_list *pm_qos_req;
 399
 400         if (count == sizeof(s32)) {
 401                 if (copy_from_user(&value, buf, sizeof(s32)))
 402                         return -EFAULT;
 403         } else if (count == 11) { /* len('0x12345678/0') */
 404                 if (copy_from_user(ascii_value, buf, 11))
 405                         return -EFAULT;
 406                 if (strlen(ascii_value) != 10)
 407                         return -EINVAL;
 408                 x = sscanf(ascii_value, "%x", &value);
 409                 if (x != 1)
 410                         return -EINVAL;
 411                 pr_debug("%s, %d, 0x%x\n", ascii_value, x, value);
 412         } else
 413                 return -EINVAL;
 414
 415         pm_qos_req = filp->private_data;
 416         pm_qos_update_request(pm_qos_req, value);
 417
 418         return count;
 419 }
 420
 421
 422 static int __init pm_qos_power_init(void)
 423 {
 424         int ret = 0;
 425
 426         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 427         if (ret < 0) {
 428                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 429                 return ret;
 430         }
 431         ret = register_pm_qos_misc(&network_lat_pm_qos);
 432         if (ret < 0) {
 433                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 434                 return ret;
 435         }
 436         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 437         if (ret < 0)
 438                 printk(KERN_ERR
 439                         "pm_qos_param: network_throughput setup failed\n");
 440
 441         return ret;
 442 }
 443
 444 late_initcall(pm_qos_power_init);