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/latency.h>
  16 #include <linux/cpu.h>
  17 #include <linux/cpuidle.h>
  18
  19 #include "cpuidle.h"
  20
  21 DEFINE_PER_CPU(struct cpuidle_device *, cpuidle_devices);
  22 EXPORT_PER_CPU_SYMBOL_GPL(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 /**
  31  * cpuidle_idle_call - the main idle loop
  32  *
  33  * NOTE: no locks or semaphores should be used here
  34  */
  35 static void cpuidle_idle_call(void)
  36 {
  37         struct cpuidle_device *dev = __get_cpu_var(cpuidle_devices);
  38         struct cpuidle_state *target_state;
  39         int next_state;
  40
  41         /* check if the device is ready */
  42         if (!dev || !dev->enabled) {
  43                 if (pm_idle_old)
  44                         pm_idle_old();
  45                 else
  46                         local_irq_enable();
  47                 return;
  48         }
  49
  50         /* ask the governor for the next state */
  51         next_state = cpuidle_curr_governor->select(dev);
  52         if (need_resched())
  53                 return;
  54         target_state = &dev->states[next_state];
  55
  56         /* enter the state and update stats */
  57         dev->last_residency = target_state->enter(dev, target_state);
  58         dev->last_state = target_state;
  59         target_state->time += dev->last_residency;
  60         target_state->usage++;
  61
  62         /* give the governor an opportunity to reflect on the outcome */
  63         if (cpuidle_curr_governor->reflect)
  64                 cpuidle_curr_governor->reflect(dev);
  65 }
  66
  67 /**
  68  * cpuidle_install_idle_handler - installs the cpuidle idle loop handler
  69  */
  70 void cpuidle_install_idle_handler(void)
  71 {
  72         if (enabled_devices && (pm_idle != cpuidle_idle_call)) {
  73                 /* Make sure all changes finished before we switch to new idle */
  74                 smp_wmb();
  75                 pm_idle = cpuidle_idle_call;
  76         }
  77 }
  78
  79 /**
  80  * cpuidle_uninstall_idle_handler - uninstalls the cpuidle idle loop handler
  81  */
  82 void cpuidle_uninstall_idle_handler(void)
  83 {
  84         if (enabled_devices && (pm_idle != pm_idle_old)) {
  85                 pm_idle = pm_idle_old;
  86                 cpu_idle_wait();
  87         }
  88 }
  89
  90 /**
  91  * cpuidle_pause_and_lock - temporarily disables CPUIDLE
  92  */
  93 void cpuidle_pause_and_lock(void)
  94 {
  95         mutex_lock(&cpuidle_lock);
  96         cpuidle_uninstall_idle_handler();
  97 }
  98
  99 EXPORT_SYMBOL_GPL(cpuidle_pause_and_lock);
 100
 101 /**
 102  * cpuidle_resume_and_unlock - resumes CPUIDLE operation
 103  */
 104 void cpuidle_resume_and_unlock(void)
 105 {
 106         cpuidle_install_idle_handler();
 107         mutex_unlock(&cpuidle_lock);
 108 }
 109
 110 EXPORT_SYMBOL_GPL(cpuidle_resume_and_unlock);
 111
 112 /**
 113  * cpuidle_enable_device - enables idle PM for a CPU
 114  * @dev: the CPU
 115  *
 116  * This function must be called between cpuidle_pause_and_lock and
 117  * cpuidle_resume_and_unlock when used externally.
 118  */
 119 int cpuidle_enable_device(struct cpuidle_device *dev)
 120 {
 121         int ret, i;
 122
 123         if (dev->enabled)
 124                 return 0;
 125         if (!cpuidle_curr_driver || !cpuidle_curr_governor)
 126                 return -EIO;
 127         if (!dev->state_count)
 128                 return -EINVAL;
 129
 130         if ((ret = cpuidle_add_state_sysfs(dev)))
 131                 return ret;
 132
 133         if (cpuidle_curr_governor->enable &&
 134             (ret = cpuidle_curr_governor->enable(dev)))
 135                 goto fail_sysfs;
 136
 137         for (i = 0; i < dev->state_count; i++) {
 138                 dev->states[i].usage = 0;
 139                 dev->states[i].time = 0;
 140         }
 141         dev->last_residency = 0;
 142         dev->last_state = NULL;
 143
 144         smp_wmb();
 145
 146         dev->enabled = 1;
 147
 148         enabled_devices++;
 149         return 0;
 150
 151 fail_sysfs:
 152         cpuidle_remove_state_sysfs(dev);
 153
 154         return ret;
 155 }
 156
 157 EXPORT_SYMBOL_GPL(cpuidle_enable_device);
 158
 159 /**
 160  * cpuidle_disable_device - disables idle PM for a CPU
 161  * @dev: the CPU
 162  *
 163  * This function must be called between cpuidle_pause_and_lock and
 164  * cpuidle_resume_and_unlock when used externally.
 165  */
 166 void cpuidle_disable_device(struct cpuidle_device *dev)
 167 {
 168         if (!dev->enabled)
 169                 return;
 170         if (!cpuidle_curr_driver || !cpuidle_curr_governor)
 171                 return;
 172
 173         dev->enabled = 0;
 174
 175         if (cpuidle_curr_governor->disable)
 176                 cpuidle_curr_governor->disable(dev);
 177
 178         cpuidle_remove_state_sysfs(dev);
 179         enabled_devices--;
 180 }
 181
 182 EXPORT_SYMBOL_GPL(cpuidle_disable_device);
 183
 184 /**
 185  * cpuidle_register_device - registers a CPU's idle PM feature
 186  * @dev: the cpu
 187  */
 188 int cpuidle_register_device(struct cpuidle_device *dev)
 189 {
 190         int ret;
 191         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 192
 193         if (!sys_dev)
 194                 return -EINVAL;
 195         if (!try_module_get(cpuidle_curr_driver->owner))
 196                 return -EINVAL;
 197
 198         init_completion(&dev->kobj_unregister);
 199
 200         mutex_lock(&cpuidle_lock);
 201
 202         per_cpu(cpuidle_devices, dev->cpu) = dev;
 203         list_add(&dev->device_list, &cpuidle_detected_devices);
 204         if ((ret = cpuidle_add_sysfs(sys_dev))) {
 205                 mutex_unlock(&cpuidle_lock);
 206                 module_put(cpuidle_curr_driver->owner);
 207                 return ret;
 208         }
 209
 210         cpuidle_enable_device(dev);
 211         cpuidle_install_idle_handler();
 212
 213         mutex_unlock(&cpuidle_lock);
 214
 215         return 0;
 216
 217 }
 218
 219 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 220
 221 /**
 222  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 223  * @dev: the cpu
 224  */
 225 void cpuidle_unregister_device(struct cpuidle_device *dev)
 226 {
 227         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 228
 229         cpuidle_pause_and_lock();
 230
 231         cpuidle_disable_device(dev);
 232
 233         cpuidle_remove_sysfs(sys_dev);
 234         list_del(&dev->device_list);
 235         wait_for_completion(&dev->kobj_unregister);
 236         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 237
 238         cpuidle_resume_and_unlock();
 239
 240         module_put(cpuidle_curr_driver->owner);
 241 }
 242
 243 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 244
 245 #ifdef CONFIG_SMP
 246
 247 static void smp_callback(void *v)
 248 {
 249         /* we already woke the CPU up, nothing more to do */
 250 }
 251
 252 /*
 253  * This function gets called when a part of the kernel has a new latency
 254  * requirement.  This means we need to get all processors out of their C-state,
 255  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 256  * wakes them all right up.
 257  */
 258 static int cpuidle_latency_notify(struct notifier_block *b,
 259                 unsigned long l, void *v)
 260 {
 261         smp_call_function(smp_callback, NULL, 0, 1);
 262         return NOTIFY_OK;
 263 }
 264
 265 static struct notifier_block cpuidle_latency_notifier = {
 266         .notifier_call = cpuidle_latency_notify,
 267 };
 268
 269 #define latency_notifier_init(x) do { register_latency_notifier(x); } while (0)
 270
 271 #else /* CONFIG_SMP */
 272
 273 #define latency_notifier_init(x) do { } while (0)
 274
 275 #endif /* CONFIG_SMP */
 276
 277 /**
 278  * cpuidle_init - core initializer
 279  */
 280 static int __init cpuidle_init(void)
 281 {
 282         int ret;
 283
 284         pm_idle_old = pm_idle;
 285
 286         ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
 287         if (ret)
 288                 return ret;
 289
 290         latency_notifier_init(&cpuidle_latency_notifier);
 291
 292         return 0;
 293 }
 294
 295 core_initcall(cpuidle_init);