1 /* 2 * cpuidle.c - core cpuidle infrastructure 3 * 4 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> 5 * Shaohua Li <shaohua.li@intel.com> 6 * Adam Belay <abelay@novell.com> 7 * 8 * This code is licenced under the GPL. 9 */ 10 11 #include <linux/kernel.h> 12 #include <linux/mutex.h> 13 #include <linux/sched.h> 14 #include <linux/notifier.h> 15 #include <linux/pm_qos_params.h> 16 #include <linux/cpu.h> 17 #include <linux/cpuidle.h> 18 #include <linux/ktime.h> 19 #include <linux/hrtimer.h> 20 #include <trace/events/power.h> 21 22 #include "cpuidle.h" 23 24 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices); 25 26 DEFINE_MUTEX(cpuidle_lock); 27 LIST_HEAD(cpuidle_detected_devices); 28 static void (*pm_idle_old)(void); 29 30 static int enabled_devices; 31 32 #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT) 33 static void cpuidle_kick_cpus(void) 34 { 35 cpu_idle_wait(); 36 } 37 #elif defined(CONFIG_SMP) 38 # error "Arch needs cpu_idle_wait() equivalent here" 39 #else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */ 40 static void cpuidle_kick_cpus(void) {} 41 #endif 42 43 static int __cpuidle_register_device(struct cpuidle_device *dev); 44 45 /** 46 * cpuidle_idle_call - the main idle loop 47 * 48 * NOTE: no locks or semaphores should be used here 49 */ 50 static void cpuidle_idle_call(void) 51 { 52 struct cpuidle_device *dev = __this_cpu_read(cpuidle_devices); 53 struct cpuidle_state *target_state; 54 int next_state; 55 56 /* check if the device is ready */ 57 if (!dev || !dev->enabled) { 58 if (pm_idle_old) 59 pm_idle_old(); 60 else 61 #if defined(CONFIG_ARCH_HAS_DEFAULT_IDLE) 62 default_idle(); 63 #else 64 local_irq_enable(); 65 #endif 66 return; 67 } 68 69 #if 0 70 /* shows regressions, re-enable for 2.6.29 */ 71 /* 72 * run any timers that can be run now, at this point 73 * before calculating the idle duration etc. 74 */ 75 hrtimer_peek_ahead_timers(); 76 #endif 77 78 /* 79 * Call the device's prepare function before calling the 80 * governor's select function. ->prepare gives the device's 81 * cpuidle driver a chance to update any dynamic information 82 * of its cpuidle states for the current idle period, e.g. 83 * state availability, latencies, residencies, etc. 84 */ 85 if (dev->prepare) 86 dev->prepare(dev); 87 88 /* ask the governor for the next state */ 89 next_state = cpuidle_curr_governor->select(dev); 90 if (need_resched()) { 91 local_irq_enable(); 92 return; 93 } 94 95 target_state = &dev->states[next_state]; 96 97 /* enter the state and update stats */ 98 dev->last_state = target_state; 99 100 trace_power_start(POWER_CSTATE, next_state, dev->cpu); 101 trace_cpu_idle(next_state, dev->cpu); 102 103 dev->last_residency = target_state->enter(dev, target_state); 104 105 trace_power_end(dev->cpu); 106 trace_cpu_idle(PWR_EVENT_EXIT, dev->cpu); 107 108 if (dev->last_state) 109 target_state = dev->last_state; 110 111 target_state->time += (unsigned long long)dev->last_residency; 112 target_state->usage++; 113 114 /* give the governor an opportunity to reflect on the outcome */ 115 if (cpuidle_curr_governor->reflect) 116 cpuidle_curr_governor->reflect(dev); 117 } 118 119 /** 120 * cpuidle_install_idle_handler - installs the cpuidle idle loop handler 121 */ 122 void cpuidle_install_idle_handler(void) 123 { 124 if (enabled_devices && (pm_idle != cpuidle_idle_call)) { 125 /* Make sure all changes finished before we switch to new idle */ 126 smp_wmb(); 127 pm_idle = cpuidle_idle_call; 128 } 129 } 130 131 /** 132 * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler 133 */ 134 void cpuidle_uninstall_idle_handler(void) 135 { 136 if (enabled_devices && pm_idle_old && (pm_idle != pm_idle_old)) { 137 pm_idle = pm_idle_old; 138 cpuidle_kick_cpus(); 139 } 140 } 141 142 /** 143 * cpuidle_pause_and_lock - temporarily disables CPUIDLE 144 */ 145 void cpuidle_pause_and_lock(void) 146 { 147 mutex_lock(&cpuidle_lock); 148 cpuidle_uninstall_idle_handler(); 149 } 150 151 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock); 152 153 /** 154 * cpuidle_resume_and_unlock - resumes CPUIDLE operation 155 */ 156 void cpuidle_resume_and_unlock(void) 157 { 158 cpuidle_install_idle_handler(); 159 mutex_unlock(&cpuidle_lock); 160 } 161 162 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock); 163 164 #ifdef CONFIG_ARCH_HAS_CPU_RELAX 165 static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st) 166 { 167 ktime_t t1, t2; 168 s64 diff; 169 int ret; 170 171 t1 = ktime_get(); 172 local_irq_enable(); 173 while (!need_resched()) 174 cpu_relax(); 175 176 t2 = ktime_get(); 177 diff = ktime_to_us(ktime_sub(t2, t1)); 178 if (diff > INT_MAX) 179 diff = INT_MAX; 180 181 ret = (int) diff; 182 return ret; 183 } 184 185 static void poll_idle_init(struct cpuidle_device *dev) 186 { 187 struct cpuidle_state *state = &dev->states[0]; 188 189 cpuidle_set_statedata(state, NULL); 190 191 snprintf(state->name, CPUIDLE_NAME_LEN, "POLL"); 192 snprintf(state->desc, CPUIDLE_DESC_LEN, "CPUIDLE CORE POLL IDLE"); 193 state->exit_latency = 0; 194 state->target_residency = 0; 195 state->power_usage = -1; 196 state->flags = 0; 197 state->enter = poll_idle; 198 } 199 #else 200 static void poll_idle_init(struct cpuidle_device *dev) {} 201 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */ 202 203 /** 204 * cpuidle_enable_device - enables idle PM for a CPU 205 * @dev: the CPU 206 * 207 * This function must be called between cpuidle_pause_and_lock and 208 * cpuidle_resume_and_unlock when used externally. 209 */ 210 int cpuidle_enable_device(struct cpuidle_device *dev) 211 { 212 int ret, i; 213 214 if (dev->enabled) 215 return 0; 216 if (!cpuidle_get_driver() || !cpuidle_curr_governor) 217 return -EIO; 218 if (!dev->state_count) 219 return -EINVAL; 220 221 if (dev->registered == 0) { 222 ret = __cpuidle_register_device(dev); 223 if (ret) 224 return ret; 225 } 226 227 poll_idle_init(dev); 228 229 if ((ret = cpuidle_add_state_sysfs(dev))) 230 return ret; 231 232 if (cpuidle_curr_governor->enable && 233 (ret = cpuidle_curr_governor->enable(dev))) 234 goto fail_sysfs; 235 236 for (i = 0; i < dev->state_count; i++) { 237 dev->states[i].usage = 0; 238 dev->states[i].time = 0; 239 } 240 dev->last_residency = 0; 241 dev->last_state = NULL; 242 243 smp_wmb(); 244 245 dev->enabled = 1; 246 247 enabled_devices++; 248 return 0; 249 250 fail_sysfs: 251 cpuidle_remove_state_sysfs(dev); 252 253 return ret; 254 } 255 256 EXPORT_SYMBOL_GPL(cpuidle_enable_device); 257 258 /** 259 * cpuidle_disable_device - disables idle PM for a CPU 260 * @dev: the CPU 261 * 262 * This function must be called between cpuidle_pause_and_lock and 263 * cpuidle_resume_and_unlock when used externally. 264 */ 265 void cpuidle_disable_device(struct cpuidle_device *dev) 266 { 267 if (!dev->enabled) 268 return; 269 if (!cpuidle_get_driver() || !cpuidle_curr_governor) 270 return; 271 272 dev->enabled = 0; 273 274 if (cpuidle_curr_governor->disable) 275 cpuidle_curr_governor->disable(dev); 276 277 cpuidle_remove_state_sysfs(dev); 278 enabled_devices--; 279 } 280 281 EXPORT_SYMBOL_GPL(cpuidle_disable_device); 282 283 /** 284 * __cpuidle_register_device - internal register function called before register 285 * and enable routines 286 * @dev: the cpu 287 * 288 * cpuidle_lock mutex must be held before this is called 289 */ 290 static int __cpuidle_register_device(struct cpuidle_device *dev) 291 { 292 int ret; 293 struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu); 294 struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver(); 295 296 if (!sys_dev) 297 return -EINVAL; 298 if (!try_module_get(cpuidle_driver->owner)) 299 return -EINVAL; 300 301 init_completion(&dev->kobj_unregister); 302 303 /* 304 * cpuidle driver should set the dev->power_specified bit 305 * before registering the device if the driver provides 306 * power_usage numbers. 307 * 308 * For those devices whose ->power_specified is not set, 309 * we fill in power_usage with decreasing values as the 310 * cpuidle code has an implicit assumption that state Cn 311 * uses less power than C(n-1). 312 * 313 * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned 314 * an power value of -1. So we use -2, -3, etc, for other 315 * c-states. 316 */ 317 if (!dev->power_specified) { 318 int i; 319 for (i = CPUIDLE_DRIVER_STATE_START; i < dev->state_count; i++) 320 dev->states[i].power_usage = -1 - i; 321 } 322 323 per_cpu(cpuidle_devices, dev->cpu) = dev; 324 list_add(&dev->device_list, &cpuidle_detected_devices); 325 if ((ret = cpuidle_add_sysfs(sys_dev))) { 326 module_put(cpuidle_driver->owner); 327 return ret; 328 } 329 330 dev->registered = 1; 331 return 0; 332 } 333 334 /** 335 * cpuidle_register_device - registers a CPU's idle PM feature 336 * @dev: the cpu 337 */ 338 int cpuidle_register_device(struct cpuidle_device *dev) 339 { 340 int ret; 341 342 mutex_lock(&cpuidle_lock); 343 344 if ((ret = __cpuidle_register_device(dev))) { 345 mutex_unlock(&cpuidle_lock); 346 return ret; 347 } 348 349 cpuidle_enable_device(dev); 350 cpuidle_install_idle_handler(); 351 352 mutex_unlock(&cpuidle_lock); 353 354 return 0; 355 356 } 357 358 EXPORT_SYMBOL_GPL(cpuidle_register_device); 359 360 /** 361 * cpuidle_unregister_device - unregisters a CPU's idle PM feature 362 * @dev: the cpu 363 */ 364 void cpuidle_unregister_device(struct cpuidle_device *dev) 365 { 366 struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu); 367 struct cpuidle_driver *cpuidle_driver = cpuidle_get_driver(); 368 369 if (dev->registered == 0) 370 return; 371 372 cpuidle_pause_and_lock(); 373 374 cpuidle_disable_device(dev); 375 376 cpuidle_remove_sysfs(sys_dev); 377 list_del(&dev->device_list); 378 wait_for_completion(&dev->kobj_unregister); 379 per_cpu(cpuidle_devices, dev->cpu) = NULL; 380 381 cpuidle_resume_and_unlock(); 382 383 module_put(cpuidle_driver->owner); 384 } 385 386 EXPORT_SYMBOL_GPL(cpuidle_unregister_device); 387 388 #ifdef CONFIG_SMP 389 390 static void smp_callback(void *v) 391 { 392 /* we already woke the CPU up, nothing more to do */ 393 } 394 395 /* 396 * This function gets called when a part of the kernel has a new latency 397 * requirement. This means we need to get all processors out of their C-state, 398 * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that 399 * wakes them all right up. 400 */ 401 static int cpuidle_latency_notify(struct notifier_block *b, 402 unsigned long l, void *v) 403 { 404 smp_call_function(smp_callback, NULL, 1); 405 return NOTIFY_OK; 406 } 407 408 static struct notifier_block cpuidle_latency_notifier = { 409 .notifier_call = cpuidle_latency_notify, 410 }; 411 412 static inline void latency_notifier_init(struct notifier_block *n) 413 { 414 pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n); 415 } 416 417 #else /* CONFIG_SMP */ 418 419 #define latency_notifier_init(x) do { } while (0) 420 421 #endif /* CONFIG_SMP */ 422 423 /** 424 * cpuidle_init - core initializer 425 */ 426 static int __init cpuidle_init(void) 427 { 428 int ret; 429 430 pm_idle_old = pm_idle; 431 432 ret = cpuidle_add_class_sysfs(&cpu_sysdev_class); 433 if (ret) 434 return ret; 435 436 latency_notifier_init(&cpuidle_latency_notifier); 437 438 return 0; 439 } 440 441 core_initcall(cpuidle_init); 442