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 /**
  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 #ifdef CONFIG_ARCH_HAS_CPU_RELAX
 185 static int poll_idle(struct cpuidle_device *dev, struct cpuidle_state *st)
 186 {
 187         ktime_t t1, t2;
 188         s64 diff;
 189         int ret;
 190
 191         t1 = ktime_get();
 192         local_irq_enable();
 193         while (!need_resched())
 194                 cpu_relax();
 195
 196         t2 = ktime_get();
 197         diff = ktime_to_us(ktime_sub(t2, t1));
 198         if (diff > INT_MAX)
 199                 diff = INT_MAX;
 200
 201         ret = (int) diff;
 202         return ret;
 203 }
 204
 205 static void poll_idle_init(struct cpuidle_device *dev)
 206 {
 207         struct cpuidle_state *state = &dev->states[0];
 208
 209         cpuidle_set_statedata(state, NULL);
 210
 211         snprintf(state->name, CPUIDLE_NAME_LEN, "C0 (poll idle)");
 212         state->exit_latency = 0;
 213         state->target_residency = 0;
 214         state->power_usage = -1;
 215         state->flags = CPUIDLE_FLAG_POLL | CPUIDLE_FLAG_TIME_VALID;
 216         state->enter = poll_idle;
 217 }
 218 #else
 219 static void poll_idle_init(struct cpuidle_device *dev) {}
 220 #endif /* CONFIG_ARCH_HAS_CPU_RELAX */
 221
 222 /**
 223  * cpuidle_register_device - registers a CPU's idle PM feature
 224  * @dev: the cpu
 225  */
 226 int cpuidle_register_device(struct cpuidle_device *dev)
 227 {
 228         int ret;
 229         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 230
 231         if (!sys_dev)
 232                 return -EINVAL;
 233         if (!try_module_get(cpuidle_curr_driver->owner))
 234                 return -EINVAL;
 235
 236         init_completion(&dev->kobj_unregister);
 237
 238         mutex_lock(&cpuidle_lock);
 239
 240         poll_idle_init(dev);
 241
 242         per_cpu(cpuidle_devices, dev->cpu) = dev;
 243         list_add(&dev->device_list, &cpuidle_detected_devices);
 244         if ((ret = cpuidle_add_sysfs(sys_dev))) {
 245                 mutex_unlock(&cpuidle_lock);
 246                 module_put(cpuidle_curr_driver->owner);
 247                 return ret;
 248         }
 249
 250         cpuidle_enable_device(dev);
 251         cpuidle_install_idle_handler();
 252
 253         mutex_unlock(&cpuidle_lock);
 254
 255         return 0;
 256
 257 }
 258
 259 EXPORT_SYMBOL_GPL(cpuidle_register_device);
 260
 261 /**
 262  * cpuidle_unregister_device - unregisters a CPU's idle PM feature
 263  * @dev: the cpu
 264  */
 265 void cpuidle_unregister_device(struct cpuidle_device *dev)
 266 {
 267         struct sys_device *sys_dev = get_cpu_sysdev((unsigned long)dev->cpu);
 268
 269         cpuidle_pause_and_lock();
 270
 271         cpuidle_disable_device(dev);
 272
 273         cpuidle_remove_sysfs(sys_dev);
 274         list_del(&dev->device_list);
 275         wait_for_completion(&dev->kobj_unregister);
 276         per_cpu(cpuidle_devices, dev->cpu) = NULL;
 277
 278         cpuidle_resume_and_unlock();
 279
 280         module_put(cpuidle_curr_driver->owner);
 281 }
 282
 283 EXPORT_SYMBOL_GPL(cpuidle_unregister_device);
 284
 285 #ifdef CONFIG_SMP
 286
 287 static void smp_callback(void *v)
 288 {
 289         /* we already woke the CPU up, nothing more to do */
 290 }
 291
 292 /*
 293  * This function gets called when a part of the kernel has a new latency
 294  * requirement.  This means we need to get all processors out of their C-state,
 295  * and then recalculate a new suitable C-state. Just do a cross-cpu IPI; that
 296  * wakes them all right up.
 297  */
 298 static int cpuidle_latency_notify(struct notifier_block *b,
 299                 unsigned long l, void *v)
 300 {
 301         smp_call_function(smp_callback, NULL, 0, 1);
 302         return NOTIFY_OK;
 303 }
 304
 305 static struct notifier_block cpuidle_latency_notifier = {
 306         .notifier_call = cpuidle_latency_notify,
 307 };
 308
 309 static inline void latency_notifier_init(struct notifier_block *n)
 310 {
 311         pm_qos_add_notifier(PM_QOS_CPU_DMA_LATENCY, n);
 312 }
 313
 314 #else /* CONFIG_SMP */
 315
 316 #define latency_notifier_init(x) do { } while (0)
 317
 318 #endif /* CONFIG_SMP */
 319
 320 /**
 321  * cpuidle_init - core initializer
 322  */
 323 static int __init cpuidle_init(void)
 324 {
 325         int ret;
 326
 327         pm_idle_old = pm_idle;
 328
 329         ret = cpuidle_add_class_sysfs(&cpu_sysdev_class);
 330         if (ret)
 331                 return ret;
 332
 333         latency_notifier_init(&cpuidle_latency_notifier);
 334
 335         return 0;
 336 }
 337
 338 core_initcall(cpuidle_init);