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 struct pm_qos_request_list {
  52         struct list_head list;
  53         union {
  54                 s32 value;
  55                 s32 usec;
  56                 s32 kbps;
  57         };
  58         int pm_qos_class;
  59 };
  60
  61 static s32 max_compare(s32 v1, s32 v2);
  62 static s32 min_compare(s32 v1, s32 v2);
  63
  64 struct pm_qos_object {
  65         struct pm_qos_request_list requests;
  66         struct blocking_notifier_head *notifiers;
  67         struct miscdevice pm_qos_power_miscdev;
  68         char *name;
  69         s32 default_value;
  70         atomic_t target_value;
  71         s32 (*comparitor)(s32, s32);
  72 };
  73
  74 static struct pm_qos_object null_pm_qos;
  75 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
  76 static struct pm_qos_object cpu_dma_pm_qos = {
  77         .requests = {LIST_HEAD_INIT(cpu_dma_pm_qos.requests.list)},
  78         .notifiers = &cpu_dma_lat_notifier,
  79         .name = "cpu_dma_latency",
  80         .default_value = 2000 * USEC_PER_SEC,
  81         .target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
  82         .comparitor = min_compare
  83 };
  84
  85 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
  86 static struct pm_qos_object network_lat_pm_qos = {
  87         .requests = {LIST_HEAD_INIT(network_lat_pm_qos.requests.list)},
  88         .notifiers = &network_lat_notifier,
  89         .name = "network_latency",
  90         .default_value = 2000 * USEC_PER_SEC,
  91         .target_value = ATOMIC_INIT(2000 * USEC_PER_SEC),
  92         .comparitor = min_compare
  93 };
  94
  95
  96 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
  97 static struct pm_qos_object network_throughput_pm_qos = {
  98         .requests = {LIST_HEAD_INIT(network_throughput_pm_qos.requests.list)},
  99         .notifiers = &network_throughput_notifier,
 100         .name = "network_throughput",
 101         .default_value = 0,
 102         .target_value = ATOMIC_INIT(0),
 103         .comparitor = max_compare
 104 };
 105
 106
 107 static struct pm_qos_object *pm_qos_array[] = {
 108         &null_pm_qos,
 109         &cpu_dma_pm_qos,
 110         &network_lat_pm_qos,
 111         &network_throughput_pm_qos
 112 };
 113
 114 static DEFINE_SPINLOCK(pm_qos_lock);
 115
 116 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 117                 size_t count, loff_t *f_pos);
 118 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 119 static int pm_qos_power_release(struct inode *inode, struct file *filp);
 120
 121 static const struct file_operations pm_qos_power_fops = {
 122         .write = pm_qos_power_write,
 123         .open = pm_qos_power_open,
 124         .release = pm_qos_power_release,
 125 };
 126
 127 /* static helper functions */
 128 static s32 max_compare(s32 v1, s32 v2)
 129 {
 130         return max(v1, v2);
 131 }
 132
 133 static s32 min_compare(s32 v1, s32 v2)
 134 {
 135         return min(v1, v2);
 136 }
 137
 138
 139 static void update_target(int pm_qos_class)
 140 {
 141         s32 extreme_value;
 142         struct pm_qos_request_list *node;
 143         unsigned long flags;
 144         int call_notifier = 0;
 145
 146         spin_lock_irqsave(&pm_qos_lock, flags);
 147         extreme_value = pm_qos_array[pm_qos_class]->default_value;
 148         list_for_each_entry(node,
 149                         &pm_qos_array[pm_qos_class]->requests.list, list) {
 150                 extreme_value = pm_qos_array[pm_qos_class]->comparitor(
 151                                 extreme_value, node->value);
 152         }
 153         if (atomic_read(&pm_qos_array[pm_qos_class]->target_value) !=
 154                         extreme_value) {
 155                 call_notifier = 1;
 156                 atomic_set(&pm_qos_array[pm_qos_class]->target_value,
 157                                 extreme_value);
 158                 pr_debug(KERN_ERR "new target for qos %d is %d\n", pm_qos_class,
 159                         atomic_read(&pm_qos_array[pm_qos_class]->target_value));
 160         }
 161         spin_unlock_irqrestore(&pm_qos_lock, flags);
 162
 163         if (call_notifier)
 164                 blocking_notifier_call_chain(
 165                                 pm_qos_array[pm_qos_class]->notifiers,
 166                                         (unsigned long) extreme_value, NULL);
 167 }
 168
 169 static int register_pm_qos_misc(struct pm_qos_object *qos)
 170 {
 171         qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 172         qos->pm_qos_power_miscdev.name = qos->name;
 173         qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;
 174
 175         return misc_register(&qos->pm_qos_power_miscdev);
 176 }
 177
 178 static int find_pm_qos_object_by_minor(int minor)
 179 {
 180         int pm_qos_class;
 181
 182         for (pm_qos_class = 0;
 183                 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 184                 if (minor ==
 185                         pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 186                         return pm_qos_class;
 187         }
 188         return -1;
 189 }
 190
 191 /**
 192  * pm_qos_request - returns current system wide qos expectation
 193  * @pm_qos_class: identification of which qos value is requested
 194  *
 195  * This function returns the current target value in an atomic manner.
 196  */
 197 int pm_qos_request(int pm_qos_class)
 198 {
 199         return atomic_read(&pm_qos_array[pm_qos_class]->target_value);
 200 }
 201 EXPORT_SYMBOL_GPL(pm_qos_request);
 202
 203 /**
 204  * pm_qos_add_request - inserts new qos request into the list
 205  * @pm_qos_class: identifies which list of qos request to us
 206  * @value: defines the qos request
 207  *
 208  * This function inserts a new entry in the pm_qos_class list of requested qos
 209  * performance characteristics.  It recomputes the aggregate QoS expectations
 210  * for the pm_qos_class of parameters, and returns the pm_qos_request list
 211  * element as a handle for use in updating and removal.  Call needs to save
 212  * this handle for later use.
 213  */
 214 struct pm_qos_request_list *pm_qos_add_request(int pm_qos_class, s32 value)
 215 {
 216         struct pm_qos_request_list *dep;
 217         unsigned long flags;
 218
 219         dep = kzalloc(sizeof(struct pm_qos_request_list), GFP_KERNEL);
 220         if (dep) {
 221                 if (value == PM_QOS_DEFAULT_VALUE)
 222                         dep->value = pm_qos_array[pm_qos_class]->default_value;
 223                 else
 224                         dep->value = value;
 225                 dep->pm_qos_class = pm_qos_class;
 226
 227                 spin_lock_irqsave(&pm_qos_lock, flags);
 228                 list_add(&dep->list,
 229                         &pm_qos_array[pm_qos_class]->requests.list);
 230                 spin_unlock_irqrestore(&pm_qos_lock, flags);
 231                 update_target(pm_qos_class);
 232         }
 233
 234         return dep;
 235 }
 236 EXPORT_SYMBOL_GPL(pm_qos_add_request);
 237
 238 /**
 239  * pm_qos_update_request - modifies an existing qos request
 240  * @pm_qos_req : handle to list element holding a pm_qos request to use
 241  * @value: defines the qos request
 242  *
 243  * Updates an existing qos request for the pm_qos_class of parameters along
 244  * with updating the target pm_qos_class value.
 245  *
 246  * Attempts are made to make this code callable on hot code paths.
 247  */
 248 void pm_qos_update_request(struct pm_qos_request_list *pm_qos_req,
 249                 s32 new_value)
 250 {
 251         unsigned long flags;
 252         int pending_update = 0;
 253         s32 temp;
 254
 255         if (pm_qos_req) { /*guard against callers passing in null */
 256                 spin_lock_irqsave(&pm_qos_lock, flags);
 257                 if (new_value == PM_QOS_DEFAULT_VALUE)
 258                         temp = pm_qos_array[pm_qos_req->pm_qos_class]->default_value;
 259                 else
 260                         temp = new_value;
 261
 262                 if (temp != pm_qos_req->value) {
 263                         pending_update = 1;
 264                         pm_qos_req->value = temp;
 265                 }
 266                 spin_unlock_irqrestore(&pm_qos_lock, flags);
 267                 if (pending_update)
 268                         update_target(pm_qos_req->pm_qos_class);
 269         }
 270 }
 271 EXPORT_SYMBOL_GPL(pm_qos_update_request);
 272
 273 /**
 274  * pm_qos_remove_request - modifies an existing qos request
 275  * @pm_qos_req: handle to request list element
 276  *
 277  * Will remove pm qos request from the list of requests and
 278  * recompute the current target value for the pm_qos_class.  Call this
 279  * on slow code paths.
 280  */
 281 void pm_qos_remove_request(struct pm_qos_request_list *pm_qos_req)
 282 {
 283         unsigned long flags;
 284         int qos_class;
 285
 286         if (pm_qos_req == NULL)
 287                 return;
 288                 /* silent return to keep pcm code cleaner */
 289
 290         qos_class = pm_qos_req->pm_qos_class;
 291         spin_lock_irqsave(&pm_qos_lock, flags);
 292         list_del(&pm_qos_req->list);
 293         kfree(pm_qos_req);
 294         spin_unlock_irqrestore(&pm_qos_lock, flags);
 295         update_target(qos_class);
 296 }
 297 EXPORT_SYMBOL_GPL(pm_qos_remove_request);
 298
 299 /**
 300  * pm_qos_add_notifier - sets notification entry for changes to target value
 301  * @pm_qos_class: identifies which qos target changes should be notified.
 302  * @notifier: notifier block managed by caller.
 303  *
 304  * will register the notifier into a notification chain that gets called
 305  * upon changes to the pm_qos_class target value.
 306  */
 307 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 308 {
 309         int retval;
 310
 311         retval = blocking_notifier_chain_register(
 312                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 313
 314         return retval;
 315 }
 316 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);
 317
 318 /**
 319  * pm_qos_remove_notifier - deletes notification entry from chain.
 320  * @pm_qos_class: identifies which qos target changes are notified.
 321  * @notifier: notifier block to be removed.
 322  *
 323  * will remove the notifier from the notification chain that gets called
 324  * upon changes to the pm_qos_class target value.
 325  */
 326 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 327 {
 328         int retval;
 329
 330         retval = blocking_notifier_chain_unregister(
 331                         pm_qos_array[pm_qos_class]->notifiers, notifier);
 332
 333         return retval;
 334 }
 335 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);
 336
 337 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 338 {
 339         long pm_qos_class;
 340
 341         pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 342         if (pm_qos_class >= 0) {
 343                 filp->private_data = (void *) pm_qos_add_request(pm_qos_class,
 344                                 PM_QOS_DEFAULT_VALUE);
 345
 346                 if (filp->private_data)
 347                         return 0;
 348         }
 349         return -EPERM;
 350 }
 351
 352 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 353 {
 354         struct pm_qos_request_list *req;
 355
 356         req = (struct pm_qos_request_list *)filp->private_data;
 357         pm_qos_remove_request(req);
 358
 359         return 0;
 360 }
 361
 362
 363 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 364                 size_t count, loff_t *f_pos)
 365 {
 366         s32 value;
 367         int x;
 368         char ascii_value[11];
 369         struct pm_qos_request_list *pm_qos_req;
 370
 371         if (count == sizeof(s32)) {
 372                 if (copy_from_user(&value, buf, sizeof(s32)))
 373                         return -EFAULT;
 374         } else if (count == 11) { /* len('0x12345678/0') */
 375                 if (copy_from_user(ascii_value, buf, 11))
 376                         return -EFAULT;
 377                 x = sscanf(ascii_value, "%x", &value);
 378                 if (x != 1)
 379                         return -EINVAL;
 380                 pr_debug(KERN_ERR "%s, %d, 0x%x\n", ascii_value, x, value);
 381         } else
 382                 return -EINVAL;
 383
 384         pm_qos_req = (struct pm_qos_request_list *)filp->private_data;
 385         pm_qos_update_request(pm_qos_req, value);
 386
 387         return count;
 388 }
 389
 390
 391 static int __init pm_qos_power_init(void)
 392 {
 393         int ret = 0;
 394
 395         ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 396         if (ret < 0) {
 397                 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 398                 return ret;
 399         }
 400         ret = register_pm_qos_misc(&network_lat_pm_qos);
 401         if (ret < 0) {
 402                 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 403                 return ret;
 404         }
 405         ret = register_pm_qos_misc(&network_throughput_pm_qos);
 406         if (ret < 0)
 407                 printk(KERN_ERR
 408                         "pm_qos_param: network_throughput setup failed\n");
 409
 410         return ret;
 411 }
 412
 413 late_initcall(pm_qos_power_init);