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