drivers/cpuidle/driver.c

   1 /*
   2  * driver.c - driver support
   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/mutex.h>
  12 #include <linux/module.h>
  13 #include <linux/sched.h>
  14 #include <linux/sched/idle.h>
  15 #include <linux/cpuidle.h>
  16 #include <linux/cpumask.h>
  17 #include <linux/tick.h>
  18 #include <linux/cpu.h>
  19
  20 #include "cpuidle.h"
  21
  22 DEFINE_SPINLOCK(cpuidle_driver_lock);
  23
  24 #ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
  25
  26 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
  27
  28 /**
  29  * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
  30  * @cpu: the CPU handled by the driver
  31  *
  32  * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
  33  * registered for @cpu.
  34  */
  35 static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  36 {
  37         return per_cpu(cpuidle_drivers, cpu);
  38 }
  39
  40 /**
  41  * __cpuidle_unset_driver - unset per CPU driver variables.
  42  * @drv: a valid pointer to a struct cpuidle_driver
  43  *
  44  * For each CPU in the driver's CPU mask, unset the registered driver per CPU
  45  * variable. If @drv is different from the registered driver, the corresponding
  46  * variable is not cleared.
  47  */
  48 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
  49 {
  50         int cpu;
  51
  52         for_each_cpu(cpu, drv->cpumask) {
  53
  54                 if (drv != __cpuidle_get_cpu_driver(cpu))
  55                         continue;
  56
  57                 per_cpu(cpuidle_drivers, cpu) = NULL;
  58         }
  59 }
  60
  61 /**
  62  * __cpuidle_set_driver - set per CPU driver variables for the given driver.
  63  * @drv: a valid pointer to a struct cpuidle_driver
  64  *
  65  * Returns 0 on success, -EBUSY if any CPU in the cpumask have a driver
  66  * different from drv already.
  67  */
  68 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
  69 {
  70         int cpu;
  71
  72         for_each_cpu(cpu, drv->cpumask) {
  73                 struct cpuidle_driver *old_drv;
  74
  75                 old_drv = __cpuidle_get_cpu_driver(cpu);
  76                 if (old_drv && old_drv != drv)
  77                         return -EBUSY;
  78         }
  79
  80         for_each_cpu(cpu, drv->cpumask)
  81                 per_cpu(cpuidle_drivers, cpu) = drv;
  82
  83         return 0;
  84 }
  85
  86 #else
  87
  88 static struct cpuidle_driver *cpuidle_curr_driver;
  89
  90 /**
  91  * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
  92  * @cpu: ignored without the multiple driver support
  93  *
  94  * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
  95  * previously registered.
  96  */
  97 static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  98 {
  99         return cpuidle_curr_driver;
 100 }
 101
 102 /**
 103  * __cpuidle_set_driver - assign the global cpuidle driver variable.
 104  * @drv: pointer to a struct cpuidle_driver object
 105  *
 106  * Returns 0 on success, -EBUSY if the driver is already registered.
 107  */
 108 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 109 {
 110         if (cpuidle_curr_driver)
 111                 return -EBUSY;
 112
 113         cpuidle_curr_driver = drv;
 114
 115         return 0;
 116 }
 117
 118 /**
 119  * __cpuidle_unset_driver - unset the global cpuidle driver variable.
 120  * @drv: a pointer to a struct cpuidle_driver
 121  *
 122  * Reset the global cpuidle variable to NULL.  If @drv does not match the
 123  * registered driver, do nothing.
 124  */
 125 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 126 {
 127         if (drv == cpuidle_curr_driver)
 128                 cpuidle_curr_driver = NULL;
 129 }
 130
 131 #endif
 132
 133 /**
 134  * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
 135  * @arg: a void pointer used to match the SMP cross call API
 136  *
 137  * If @arg is NULL broadcast is disabled otherwise enabled
 138  *
 139  * This function is executed per CPU by an SMP cross call.  It's not
 140  * supposed to be called directly.
 141  */
 142 static void cpuidle_setup_broadcast_timer(void *arg)
 143 {
 144         if (arg)
 145                 tick_broadcast_enable();
 146         else
 147                 tick_broadcast_disable();
 148 }
 149
 150 /**
 151  * __cpuidle_driver_init - initialize the driver's internal data
 152  * @drv: a valid pointer to a struct cpuidle_driver
 153  */
 154 static void __cpuidle_driver_init(struct cpuidle_driver *drv)
 155 {
 156         int i;
 157
 158         /*
 159          * Use all possible CPUs as the default, because if the kernel boots
 160          * with some CPUs offline and then we online one of them, the CPU
 161          * notifier has to know which driver to assign.
 162          */
 163         if (!drv->cpumask)
 164                 drv->cpumask = (struct cpumask *)cpu_possible_mask;
 165
 166         for (i = 0; i < drv->state_count; i++) {
 167                 struct cpuidle_state *s = &drv->states[i];
 168
 169                 /*
 170                  * Look for the timer stop flag in the different states and if
 171                  * it is found, indicate that the broadcast timer has to be set
 172                  * up.
 173                  */
 174                 if (s->flags & CPUIDLE_FLAG_TIMER_STOP)
 175                         drv->bctimer = 1;
 176
 177                 /*
 178                  * The core will use the target residency and exit latency
 179                  * values in nanoseconds, but allow drivers to provide them in
 180                  * microseconds too.
 181                  */
 182                 if (s->target_residency > 0)
 183                         s->target_residency_ns = s->target_residency * NSEC_PER_USEC;
 184
 185                 if (s->exit_latency > 0)
 186                         s->exit_latency_ns = s->exit_latency * NSEC_PER_USEC;
 187         }
 188 }
 189
 190 /**
 191  * __cpuidle_register_driver: register the driver
 192  * @drv: a valid pointer to a struct cpuidle_driver
 193  *
 194  * Do some sanity checks, initialize the driver, assign the driver to the
 195  * global cpuidle driver variable(s) and set up the broadcast timer if the
 196  * cpuidle driver has some states that shut down the local timer.
 197  *
 198  * Returns 0 on success, a negative error code otherwise:
 199  *  * -EINVAL if the driver pointer is NULL or no idle states are available
 200  *  * -ENODEV if the cpuidle framework is disabled
 201  *  * -EBUSY if the driver is already assigned to the global variable(s)
 202  */
 203 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 204 {
 205         int ret;
 206
 207         if (!drv || !drv->state_count)
 208                 return -EINVAL;
 209
 210         ret = cpuidle_coupled_state_verify(drv);
 211         if (ret)
 212                 return ret;
 213
 214         if (cpuidle_disabled())
 215                 return -ENODEV;
 216
 217         __cpuidle_driver_init(drv);
 218
 219         ret = __cpuidle_set_driver(drv);
 220         if (ret)
 221                 return ret;
 222
 223         if (drv->bctimer)
 224                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 225                                  (void *)1, 1);
 226
 227         return 0;
 228 }
 229
 230 /**
 231  * __cpuidle_unregister_driver - unregister the driver
 232  * @drv: a valid pointer to a struct cpuidle_driver
 233  *
 234  * Check if the driver is no longer in use, reset the global cpuidle driver
 235  * variable(s) and disable the timer broadcast notification mechanism if it was
 236  * in use.
 237  *
 238  */
 239 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 240 {
 241         if (drv->bctimer) {
 242                 drv->bctimer = 0;
 243                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 244                                  NULL, 1);
 245         }
 246
 247         __cpuidle_unset_driver(drv);
 248 }
 249
 250 /**
 251  * cpuidle_register_driver - registers a driver
 252  * @drv: a pointer to a valid struct cpuidle_driver
 253  *
 254  * Register the driver under a lock to prevent concurrent attempts to
 255  * [un]register the driver from occuring at the same time.
 256  *
 257  * Returns 0 on success, a negative error code (returned by
 258  * __cpuidle_register_driver()) otherwise.
 259  */
 260 int cpuidle_register_driver(struct cpuidle_driver *drv)
 261 {
 262         struct cpuidle_governor *gov;
 263         int ret;
 264
 265         spin_lock(&cpuidle_driver_lock);
 266         ret = __cpuidle_register_driver(drv);
 267         spin_unlock(&cpuidle_driver_lock);
 268
 269         if (!ret && !strlen(param_governor) && drv->governor &&
 270             (cpuidle_get_driver() == drv)) {
 271                 mutex_lock(&cpuidle_lock);
 272                 gov = cpuidle_find_governor(drv->governor);
 273                 if (gov) {
 274                         cpuidle_prev_governor = cpuidle_curr_governor;
 275                         if (cpuidle_switch_governor(gov) < 0)
 276                                 cpuidle_prev_governor = NULL;
 277                 }
 278                 mutex_unlock(&cpuidle_lock);
 279         }
 280
 281         return ret;
 282 }
 283 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 284
 285 /**
 286  * cpuidle_unregister_driver - unregisters a driver
 287  * @drv: a pointer to a valid struct cpuidle_driver
 288  *
 289  * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
 290  * to [un]register the driver from occuring at the same time.  @drv has to
 291  * match the currently registered driver.
 292  */
 293 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 294 {
 295         bool enabled = (cpuidle_get_driver() == drv);
 296
 297         spin_lock(&cpuidle_driver_lock);
 298         __cpuidle_unregister_driver(drv);
 299         spin_unlock(&cpuidle_driver_lock);
 300
 301         if (!enabled)
 302                 return;
 303
 304         mutex_lock(&cpuidle_lock);
 305         if (cpuidle_prev_governor) {
 306                 if (!cpuidle_switch_governor(cpuidle_prev_governor))
 307                         cpuidle_prev_governor = NULL;
 308         }
 309         mutex_unlock(&cpuidle_lock);
 310 }
 311 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 312
 313 /**
 314  * cpuidle_get_driver - return the driver tied to the current CPU.
 315  *
 316  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
 317  */
 318 struct cpuidle_driver *cpuidle_get_driver(void)
 319 {
 320         struct cpuidle_driver *drv;
 321         int cpu;
 322
 323         cpu = get_cpu();
 324         drv = __cpuidle_get_cpu_driver(cpu);
 325         put_cpu();
 326
 327         return drv;
 328 }
 329 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 330
 331 /**
 332  * cpuidle_get_cpu_driver - return the driver registered for a CPU.
 333  * @dev: a valid pointer to a struct cpuidle_device
 334  *
 335  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
 336  * for the CPU associated with @dev.
 337  */
 338 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 339 {
 340         if (!dev)
 341                 return NULL;
 342
 343         return __cpuidle_get_cpu_driver(dev->cpu);
 344 }
 345 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 346
 347 /**
 348  * cpuidle_driver_state_disabled - Disable or enable an idle state
 349  * @drv: cpuidle driver owning the state
 350  * @idx: State index
 351  * @disable: Whether or not to disable the state
 352  */
 353 void cpuidle_driver_state_disabled(struct cpuidle_driver *drv, int idx,
 354                                  bool disable)
 355 {
 356         unsigned int cpu;
 357
 358         mutex_lock(&cpuidle_lock);
 359
 360         spin_lock(&cpuidle_driver_lock);
 361
 362         if (!drv->cpumask) {
 363                 drv->states[idx].flags |= CPUIDLE_FLAG_UNUSABLE;
 364                 goto unlock;
 365         }
 366
 367         for_each_cpu(cpu, drv->cpumask) {
 368                 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
 369
 370                 if (!dev)
 371                         continue;
 372
 373                 if (disable)
 374                         dev->states_usage[idx].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
 375                 else
 376                         dev->states_usage[idx].disable &= ~CPUIDLE_STATE_DISABLED_BY_DRIVER;
 377         }
 378
 379 unlock:
 380         spin_unlock(&cpuidle_driver_lock);
 381
 382         mutex_unlock(&cpuidle_lock);
 383 }