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.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 #include <linux/kernel.h> 44 45 #include <linux/uaccess.h> 46 #include <linux/export.h> 47 48 /* 49 * locking rule: all changes to constraints or notifiers lists 50 * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock 51 * held, taken with _irqsave. One lock to rule them all 52 */ 53 struct pm_qos_object { 54 struct pm_qos_constraints *constraints; 55 struct miscdevice pm_qos_power_miscdev; 56 char *name; 57 }; 58 59 static DEFINE_SPINLOCK(pm_qos_lock); 60 61 static struct pm_qos_object null_pm_qos; 62 63 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier); 64 static struct pm_qos_constraints cpu_dma_constraints = { 65 .list = PLIST_HEAD_INIT(cpu_dma_constraints.list), 66 .target_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE, 67 .default_value = PM_QOS_CPU_DMA_LAT_DEFAULT_VALUE, 68 .type = PM_QOS_MIN, 69 .notifiers = &cpu_dma_lat_notifier, 70 }; 71 static struct pm_qos_object cpu_dma_pm_qos = { 72 .constraints = &cpu_dma_constraints, 73 .name = "cpu_dma_latency", 74 }; 75 76 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier); 77 static struct pm_qos_constraints network_lat_constraints = { 78 .list = PLIST_HEAD_INIT(network_lat_constraints.list), 79 .target_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE, 80 .default_value = PM_QOS_NETWORK_LAT_DEFAULT_VALUE, 81 .type = PM_QOS_MIN, 82 .notifiers = &network_lat_notifier, 83 }; 84 static struct pm_qos_object network_lat_pm_qos = { 85 .constraints = &network_lat_constraints, 86 .name = "network_latency", 87 }; 88 89 90 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier); 91 static struct pm_qos_constraints network_tput_constraints = { 92 .list = PLIST_HEAD_INIT(network_tput_constraints.list), 93 .target_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE, 94 .default_value = PM_QOS_NETWORK_THROUGHPUT_DEFAULT_VALUE, 95 .type = PM_QOS_MAX, 96 .notifiers = &network_throughput_notifier, 97 }; 98 static struct pm_qos_object network_throughput_pm_qos = { 99 .constraints = &network_tput_constraints, 100 .name = "network_throughput", 101 }; 102 103 104 static struct pm_qos_object *pm_qos_array[] = { 105 &null_pm_qos, 106 &cpu_dma_pm_qos, 107 &network_lat_pm_qos, 108 &network_throughput_pm_qos 109 }; 110 111 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf, 112 size_t count, loff_t *f_pos); 113 static ssize_t pm_qos_power_read(struct file *filp, 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 .read = pm_qos_power_read, 121 .open = pm_qos_power_open, 122 .release = pm_qos_power_release, 123 .llseek = noop_llseek, 124 }; 125 126 /* unlocked internal variant */ 127 static inline int pm_qos_get_value(struct pm_qos_constraints *c) 128 { 129 if (plist_head_empty(&c->list)) 130 return c->default_value; 131 132 switch (c->type) { 133 case PM_QOS_MIN: 134 return plist_first(&c->list)->prio; 135 136 case PM_QOS_MAX: 137 return plist_last(&c->list)->prio; 138 139 default: 140 /* runtime check for not using enum */ 141 BUG(); 142 } 143 } 144 145 s32 pm_qos_read_value(struct pm_qos_constraints *c) 146 { 147 return c->target_value; 148 } 149 150 static inline void pm_qos_set_value(struct pm_qos_constraints *c, s32 value) 151 { 152 c->target_value = value; 153 } 154 155 /** 156 * pm_qos_update_target - manages the constraints list and calls the notifiers 157 * if needed 158 * @c: constraints data struct 159 * @node: request to add to the list, to update or to remove 160 * @action: action to take on the constraints list 161 * @value: value of the request to add or update 162 * 163 * This function returns 1 if the aggregated constraint value has changed, 0 164 * otherwise. 165 */ 166 int pm_qos_update_target(struct pm_qos_constraints *c, struct plist_node *node, 167 enum pm_qos_req_action action, int value) 168 { 169 unsigned long flags; 170 int prev_value, curr_value, new_value; 171 172 spin_lock_irqsave(&pm_qos_lock, flags); 173 prev_value = pm_qos_get_value(c); 174 if (value == PM_QOS_DEFAULT_VALUE) 175 new_value = c->default_value; 176 else 177 new_value = value; 178 179 switch (action) { 180 case PM_QOS_REMOVE_REQ: 181 plist_del(node, &c->list); 182 break; 183 case PM_QOS_UPDATE_REQ: 184 /* 185 * to change the list, we atomically remove, reinit 186 * with new value and add, then see if the extremal 187 * changed 188 */ 189 plist_del(node, &c->list); 190 case PM_QOS_ADD_REQ: 191 plist_node_init(node, new_value); 192 plist_add(node, &c->list); 193 break; 194 default: 195 /* no action */ 196 ; 197 } 198 199 curr_value = pm_qos_get_value(c); 200 pm_qos_set_value(c, curr_value); 201 202 spin_unlock_irqrestore(&pm_qos_lock, flags); 203 204 if (prev_value != curr_value) { 205 blocking_notifier_call_chain(c->notifiers, 206 (unsigned long)curr_value, 207 NULL); 208 return 1; 209 } else { 210 return 0; 211 } 212 } 213 214 /** 215 * pm_qos_request - returns current system wide qos expectation 216 * @pm_qos_class: identification of which qos value is requested 217 * 218 * This function returns the current target value. 219 */ 220 int pm_qos_request(int pm_qos_class) 221 { 222 return pm_qos_read_value(pm_qos_array[pm_qos_class]->constraints); 223 } 224 EXPORT_SYMBOL_GPL(pm_qos_request); 225 226 int pm_qos_request_active(struct pm_qos_request *req) 227 { 228 return req->pm_qos_class != 0; 229 } 230 EXPORT_SYMBOL_GPL(pm_qos_request_active); 231 232 /** 233 * pm_qos_add_request - inserts new qos request into the list 234 * @req: pointer to a preallocated handle 235 * @pm_qos_class: identifies which list of qos request to use 236 * @value: defines the qos request 237 * 238 * This function inserts a new entry in the pm_qos_class list of requested qos 239 * performance characteristics. It recomputes the aggregate QoS expectations 240 * for the pm_qos_class of parameters and initializes the pm_qos_request 241 * handle. Caller needs to save this handle for later use in updates and 242 * removal. 243 */ 244 245 void pm_qos_add_request(struct pm_qos_request *req, 246 int pm_qos_class, s32 value) 247 { 248 if (!req) /*guard against callers passing in null */ 249 return; 250 251 if (pm_qos_request_active(req)) { 252 WARN(1, KERN_ERR "pm_qos_add_request() called for already added request\n"); 253 return; 254 } 255 req->pm_qos_class = pm_qos_class; 256 pm_qos_update_target(pm_qos_array[pm_qos_class]->constraints, 257 &req->node, PM_QOS_ADD_REQ, value); 258 } 259 EXPORT_SYMBOL_GPL(pm_qos_add_request); 260 261 /** 262 * pm_qos_update_request - modifies an existing qos request 263 * @req : handle to list element holding a pm_qos request to use 264 * @value: defines the qos request 265 * 266 * Updates an existing qos request for the pm_qos_class of parameters along 267 * with updating the target pm_qos_class value. 268 * 269 * Attempts are made to make this code callable on hot code paths. 270 */ 271 void pm_qos_update_request(struct pm_qos_request *req, 272 s32 new_value) 273 { 274 if (!req) /*guard against callers passing in null */ 275 return; 276 277 if (!pm_qos_request_active(req)) { 278 WARN(1, KERN_ERR "pm_qos_update_request() called for unknown object\n"); 279 return; 280 } 281 282 if (new_value != req->node.prio) 283 pm_qos_update_target( 284 pm_qos_array[req->pm_qos_class]->constraints, 285 &req->node, PM_QOS_UPDATE_REQ, new_value); 286 } 287 EXPORT_SYMBOL_GPL(pm_qos_update_request); 288 289 /** 290 * pm_qos_remove_request - modifies an existing qos request 291 * @req: handle to request list element 292 * 293 * Will remove pm qos request from the list of constraints and 294 * recompute the current target value for the pm_qos_class. Call this 295 * on slow code paths. 296 */ 297 void pm_qos_remove_request(struct pm_qos_request *req) 298 { 299 if (!req) /*guard against callers passing in null */ 300 return; 301 /* silent return to keep pcm code cleaner */ 302 303 if (!pm_qos_request_active(req)) { 304 WARN(1, KERN_ERR "pm_qos_remove_request() called for unknown object\n"); 305 return; 306 } 307 308 pm_qos_update_target(pm_qos_array[req->pm_qos_class]->constraints, 309 &req->node, PM_QOS_REMOVE_REQ, 310 PM_QOS_DEFAULT_VALUE); 311 memset(req, 0, sizeof(*req)); 312 } 313 EXPORT_SYMBOL_GPL(pm_qos_remove_request); 314 315 /** 316 * pm_qos_add_notifier - sets notification entry for changes to target value 317 * @pm_qos_class: identifies which qos target changes should be notified. 318 * @notifier: notifier block managed by caller. 319 * 320 * will register the notifier into a notification chain that gets called 321 * upon changes to the pm_qos_class target value. 322 */ 323 int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier) 324 { 325 int retval; 326 327 retval = blocking_notifier_chain_register( 328 pm_qos_array[pm_qos_class]->constraints->notifiers, 329 notifier); 330 331 return retval; 332 } 333 EXPORT_SYMBOL_GPL(pm_qos_add_notifier); 334 335 /** 336 * pm_qos_remove_notifier - deletes notification entry from chain. 337 * @pm_qos_class: identifies which qos target changes are notified. 338 * @notifier: notifier block to be removed. 339 * 340 * will remove the notifier from the notification chain that gets called 341 * upon changes to the pm_qos_class target value. 342 */ 343 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier) 344 { 345 int retval; 346 347 retval = blocking_notifier_chain_unregister( 348 pm_qos_array[pm_qos_class]->constraints->notifiers, 349 notifier); 350 351 return retval; 352 } 353 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier); 354 355 /* User space interface to PM QoS classes via misc devices */ 356 static int register_pm_qos_misc(struct pm_qos_object *qos) 357 { 358 qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR; 359 qos->pm_qos_power_miscdev.name = qos->name; 360 qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops; 361 362 return misc_register(&qos->pm_qos_power_miscdev); 363 } 364 365 static int find_pm_qos_object_by_minor(int minor) 366 { 367 int pm_qos_class; 368 369 for (pm_qos_class = 0; 370 pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) { 371 if (minor == 372 pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor) 373 return pm_qos_class; 374 } 375 return -1; 376 } 377 378 static int pm_qos_power_open(struct inode *inode, struct file *filp) 379 { 380 long pm_qos_class; 381 382 pm_qos_class = find_pm_qos_object_by_minor(iminor(inode)); 383 if (pm_qos_class >= 0) { 384 struct pm_qos_request *req = kzalloc(sizeof(*req), GFP_KERNEL); 385 if (!req) 386 return -ENOMEM; 387 388 pm_qos_add_request(req, pm_qos_class, PM_QOS_DEFAULT_VALUE); 389 filp->private_data = req; 390 391 return 0; 392 } 393 return -EPERM; 394 } 395 396 static int pm_qos_power_release(struct inode *inode, struct file *filp) 397 { 398 struct pm_qos_request *req; 399 400 req = filp->private_data; 401 pm_qos_remove_request(req); 402 kfree(req); 403 404 return 0; 405 } 406 407 408 static ssize_t pm_qos_power_read(struct file *filp, char __user *buf, 409 size_t count, loff_t *f_pos) 410 { 411 s32 value; 412 unsigned long flags; 413 struct pm_qos_request *req = filp->private_data; 414 415 if (!req) 416 return -EINVAL; 417 if (!pm_qos_request_active(req)) 418 return -EINVAL; 419 420 spin_lock_irqsave(&pm_qos_lock, flags); 421 value = pm_qos_get_value(pm_qos_array[req->pm_qos_class]->constraints); 422 spin_unlock_irqrestore(&pm_qos_lock, flags); 423 424 return simple_read_from_buffer(buf, count, f_pos, &value, sizeof(s32)); 425 } 426 427 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf, 428 size_t count, loff_t *f_pos) 429 { 430 s32 value; 431 struct pm_qos_request *req; 432 433 if (count == sizeof(s32)) { 434 if (copy_from_user(&value, buf, sizeof(s32))) 435 return -EFAULT; 436 } else if (count <= 11) { /* ASCII perhaps? */ 437 char ascii_value[11]; 438 unsigned long int ulval; 439 int ret; 440 441 if (copy_from_user(ascii_value, buf, count)) 442 return -EFAULT; 443 444 if (count > 10) { 445 if (ascii_value[10] == '\n') 446 ascii_value[10] = '\0'; 447 else 448 return -EINVAL; 449 } else { 450 ascii_value[count] = '\0'; 451 } 452 ret = strict_strtoul(ascii_value, 16, &ulval); 453 if (ret) { 454 pr_debug("%s, 0x%lx, 0x%x\n", ascii_value, ulval, ret); 455 return -EINVAL; 456 } 457 value = (s32)lower_32_bits(ulval); 458 } else { 459 return -EINVAL; 460 } 461 462 req = filp->private_data; 463 pm_qos_update_request(req, value); 464 465 return count; 466 } 467 468 469 static int __init pm_qos_power_init(void) 470 { 471 int ret = 0; 472 473 ret = register_pm_qos_misc(&cpu_dma_pm_qos); 474 if (ret < 0) { 475 printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n"); 476 return ret; 477 } 478 ret = register_pm_qos_misc(&network_lat_pm_qos); 479 if (ret < 0) { 480 printk(KERN_ERR "pm_qos_param: network_latency setup failed\n"); 481 return ret; 482 } 483 ret = register_pm_qos_misc(&network_throughput_pm_qos); 484 if (ret < 0) 485 printk(KERN_ERR 486 "pm_qos_param: network_throughput setup failed\n"); 487 488 return ret; 489 } 490 491 late_initcall(pm_qos_power_init); 492