drivers/cpuidle/cpuidle.c

   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
  20 #include "cpuidle.h"
  21
  22 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
  23
  24 DEFINE_MUTEX(cpuidle_lock);
  25 LIST_HEAD(cpuidle_detected_devices);
  26 static void (*pm_idle_old)(void);
  27
  28 static int enabled_devices;
  29
  30 #if defined(CONFIG_ARCH_HAS_CPU_IDLE_WAIT)
  31 static void cpuidle_kick_cpus(void)
  32 {
  33         cpu_idle_wait();
  34 }
  35 #elif defined(CONFIG_SMP)
  36 # error "Arch needs cpu_idle_wait() equivalent here"
  37 #else /* !CONFIG_ARCH_HAS_CPU_IDLE_WAIT && !CONFIG_SMP */
  38 static void cpuidle_kick_cpus(void) {}
  39 #endif
  40
  41 /**
  42  * cpuidle_idle_call - the main idle loop
  43  *
  44  * NOTE: no locks or semaphores should be used here
  45  */
  46 static void cpuidle_idle_call(void)
  47 {
  48         struct cpuidle_device *dev = __get_cpu_var(cpuidle_devices);
  49         struct cpuidle_state *target_state;
  50         int next_state;
  51
  52         /* check if the device is ready */
  53         if (!dev || !dev->enabled) {
  54                 if (pm_idle_old)
  55                         pm_idle_old();
  56                 else
  57                         local_irq_enable();
  58                 return;
  59         }
  60
  61         /* ask the governor for the next state */
  62         next_state = cpuidle_curr_governor->select(dev);
  63         if (need_resched())
  64                 return;
  65         target_state = &dev->states[next_state];
  66
  67         /* enter the state and update stats */
  68         dev->last_residency = target_state->enter(dev, target_state);
  69         dev->last_state = target_state;
  70         target_state->time += dev->last_residency;
  71         target_state->usage++;
  72
  73         /* give the governor an opportunity to reflect on the outcome */
  74         if (cpuidle_curr_governor->reflect)
  75                 cpuidle_curr_governor->reflect(dev);
  76 }
  77
  78 /**
  79  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
  80  */
  81 void cpuidle_install_idle_handler(void)
  82 {
  83         if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
  84                 /* Make sure all changes finished before we switch to new idle */
  85                 smp_wmb();
  86                 pm_idle = cpuidle_idle_call;
  87         }
  88 }
  89
  90 /**
  91  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
  92  */
  93 void cpuidle_uninstall_idle_handler(void)
  94 {
  95         if (enabled_devices && (pm_idle != pm_idle_old)) {
  96                 pm_idle = pm_idle_old;
  97                 cpuidle_kick_cpus();
  98         }
  99 }
 100
 101 /**
 102  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
 103  */
 104 void cpuidle_pause_and_lock(void)
 105 {
 106         mutex_lock(&cpuidle_lock);
 107         cpuidle_uninstall_idle_handler();
 108 }
 109
 110 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 111
 112 /**
 113  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 114  */
 115 void cpuidle_resume_and_unlock(void)
 116 {
 117         cpuidle_install_idle_handler();
 118         mutex_unlock(&cpuidle_lock);
 119 }
 120
 121 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 122
 123 /**
 124  * cpuidle_enable_device - enables idle PM for a CPU
 125  * @dev: the CPU
 126  *
 127  * This function must be called between cpuidle_pause_and_lock and
 128  * cpuidle_resume_and_unlock when used externally.
 129  */
 130 int cpuidle_enable_device(struct cpuidle_device *dev)
 131 {
 132         int ret, i;
 133
 134         if (dev->enabled)
 135                 return 0;
 136         if (!cpuidle_curr_driver || !cpuidle_curr_governor)
 137                 return -EIO;
 138         if (!dev->state_count)
 139                 return -EINVAL;
 140
 141         if ((ret = cpuidle_add_state_sysfs(dev)))
 142                 return ret;
 143
 144         if (cpuidle_curr_governor->enable &&
 145             (ret = cpuidle_curr_governor->enable(dev)))
 146                 goto fail_sysfs;
 147
 148         for (i = 0; i < dev->state_count; i++) {
 149                 dev->states[i].usage = 0;
 150                 dev->states[i].time = 0;
 151         }
 152         dev->last_residency = 0;
 153         dev->last_state = NULL;
 154
 155         smp_wmb();
 156
 157         dev->enabled = 1;
 158
 159         enabled_devices++;
 160         return 0;
 161
 162 fail_sysfs:
 163         cpuidle_remove_state_sysfs(dev);
 164
 165         return ret;
 166 }
 167
 168 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 169
 170 /**
 171  * cpuidle_disable_device - disables idle PM for a CPU
 172  * @dev: the CPU
 173  *
 174  * This function must be called between cpuidle_pause_and_lock and
 175  * cpuidle_resume_and_unlock when used externally.
 176  */
 177 void cpuidle_disable_device(struct cpuidle_device *dev)
 178 {
 179         if (!dev->enabled)
 180                 return;
 181         if (!cpuidle_curr_driver || !cpuidle_curr_governor)
 182                 return;
 183
 184         dev->enabled = 0;
 185
 186         if (cpuidle_curr_governor->disable)
 187                 cpuidle_curr_governor->disable(dev);
 188
 189         cpuidle_remove_state_sysfs(dev);
 190         enabled_devices--;
 191 }
 192
 193 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 194
 195 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 196 static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
 197 {
 198         ktime_t t1, t2;
 199         s64 diff;
 200         int ret;
 201
 202         t1 = ktime_get();
 203         local_irq_enable();
 204         while (!need_resched())
 205                 cpu_relax();
 206
 207         t2 = ktime_get();
 208         diff = ktime_to_us(ktime_sub(t2, t1));
 209         if (diff > INT_MAX)
 210                 diff = INT_MAX;
 211
 212         ret = (int) diff;
 213         return ret;
 214 }
 215
 216 static void poll_idle_init(struct cpuidle_device *dev)
 217 {
 218         struct cpuidle_state *state = &dev->states[0];
 219
 220         cpuidle_set_statedata(state, NULL);
 221
 222         snprintf(state->name, CPUIDLE_NAME_LEN, "C0 (poll idle)");
 223         state->exit_latency = 0;
 224         state->target_residency = 0;
 225         state->power_usage = -1;
 226         state->flags = CPUIDLE_FLAG_POLL | CPUIDLE_FLAG_TIME_VALID;
 227         state->enter = poll_idle;
 228 }
 229 #else
 230 static void poll_idle_init(struct cpuidle_device *dev) {}
 231 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 232
 233 /**
 234  * cpuidle_register_device - registers a CPU's idle PM feature
 235  * @dev: the cpu
 236  */
 237 int cpuidle_register_device(struct cpuidle_device *dev)
 238 {
 239         int ret;
 240         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 241
 242         if (!sys_dev)
 243                 return -EINVAL;
 244         if (!try_module_get(cpuidle_curr_driver->owner))
 245                 return -EINVAL;
 246
 247         init_completion(&dev->kobj_unregister);
 248
 249         mutex_lock(&cpuidle_lock);
 250
 251         poll_idle_init(dev);
 252
 253         per_cpu(cpuidle_devices, dev->cpu) = dev;
 254         list_add(&dev->device_list, &cpuidle_detected_devices);
 255         if ((ret = cpuidle_add_sysfs(sys_dev))) {
 256                 mutex_unlock(&cpuidle_lock);
 257                 module_put(cpuidle_curr_driver->owner);
 258                 return ret;
 259         }
 260
 261         cpuidle_enable_device(dev);
 262         cpuidle_install_idle_handler();
 263
 264         mutex_unlock(&cpuidle_lock);
 265
 266         return 0;
 267
 268 }
 269
 270 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 271
 272 /**
 273  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 274  * @dev: the cpu
 275  */
 276 void cpuidle_unregister_device(struct cpuidle_device *dev)
 277 {
 278         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 279
 280         cpuidle_pause_and_lock();
 281
 282         cpuidle_disable_device(dev);
 283
 284         cpuidle_remove_sysfs(sys_dev);
 285         list_del(&dev->device_list);
 286         wait_for_completion(&dev->kobj_unregister);
 287         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 288
 289         cpuidle_resume_and_unlock();
 290
 291         module_put(cpuidle_curr_driver->owner);
 292 }
 293
 294 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 295
 296 #ifdef CONFIG_SMP
 297
 298 static void smp_callback(void *v)
 299 {
 300         /* we already woke the CPU up, nothing more to do */
 301 }
 302
 303 /*
 304  * This function gets called when a part of the kernel has a new latency
 305  * requirement.  This means we need to get all processors out of their C-state,
 306  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 307  * wakes them all right up.
 308  */
 309 static int cpuidle_latency_notify(struct notifier_block *b,
 310                 unsigned long l, void *v)
 311 {
 312         smp_call_function(smp_callback, NULL, 0, 1);
 313         return NOTIFY_OK;
 314 }
 315
 316 static struct notifier_block cpuidle_latency_notifier = {
 317         .notifier_call = cpuidle_latency_notify,
 318 };
 319
 320 static inline void latency_notifier_init(struct notifier_block *n)
 321 {
 322         pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 323 }
 324
 325 #else /* CONFIG_SMP */
 326
 327 #define latency_notifier_init(x) do { } while (0)
 328
 329 #endif /* CONFIG_SMP */
 330
 331 /**
 332  * cpuidle_init - core initializer
 333  */
 334 static int __init cpuidle_init(void)
 335 {
 336         int ret;
 337
 338         pm_idle_old = pm_idle;
 339
 340         ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
 341         if (ret)
 342                 return ret;
 343
 344         latency_notifier_init(&cpuidle_latency_notifier);
 345
 346         return 0;
 347 }
 348
 349 core_initcall(cpuidle_init);