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 #include <linux/math64.h>
  20
  21 #include "cpuidle.h"
  22
  23 DEFINE_SPINLOCK(cpuidle_driver_lock);
  24
  25 #ifdef CONFIG_CPU_IDLE_MULTIPLE_DRIVERS
  26
  27 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
  28
  29 /**
  30  * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
  31  * @cpu: the CPU handled by the driver
  32  *
  33  * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
  34  * registered for @cpu.
  35  */
  36 static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  37 {
  38         return per_cpu(cpuidle_drivers, cpu);
  39 }
  40
  41 /**
  42  * __cpuidle_unset_driver - unset per CPU driver variables.
  43  * @drv: a valid pointer to a struct cpuidle_driver
  44  *
  45  * For each CPU in the driver's CPU mask, unset the registered driver per CPU
  46  * variable. If @drv is different from the registered driver, the corresponding
  47  * variable is not cleared.
  48  */
  49 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
  50 {
  51         int cpu;
  52
  53         for_each_cpu(cpu, drv->cpumask) {
  54
  55                 if (drv != __cpuidle_get_cpu_driver(cpu))
  56                         continue;
  57
  58                 per_cpu(cpuidle_drivers, cpu) = NULL;
  59         }
  60 }
  61
  62 /**
  63  * __cpuidle_set_driver - set per CPU driver variables for the given driver.
  64  * @drv: a valid pointer to a struct cpuidle_driver
  65  *
  66  * Returns 0 on success, -EBUSY if any CPU in the cpumask have a driver
  67  * different from drv already.
  68  */
  69 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
  70 {
  71         int cpu;
  72
  73         for_each_cpu(cpu, drv->cpumask) {
  74                 struct cpuidle_driver *old_drv;
  75
  76                 old_drv = __cpuidle_get_cpu_driver(cpu);
  77                 if (old_drv && old_drv != drv)
  78                         return -EBUSY;
  79         }
  80
  81         for_each_cpu(cpu, drv->cpumask)
  82                 per_cpu(cpuidle_drivers, cpu) = drv;
  83
  84         return 0;
  85 }
  86
  87 #else
  88
  89 static struct cpuidle_driver *cpuidle_curr_driver;
  90
  91 /**
  92  * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
  93  * @cpu: ignored without the multiple driver support
  94  *
  95  * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
  96  * previously registered.
  97  */
  98 static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
  99 {
 100         return cpuidle_curr_driver;
 101 }
 102
 103 /**
 104  * __cpuidle_set_driver - assign the global cpuidle driver variable.
 105  * @drv: pointer to a struct cpuidle_driver object
 106  *
 107  * Returns 0 on success, -EBUSY if the driver is already registered.
 108  */
 109 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 110 {
 111         if (cpuidle_curr_driver)
 112                 return -EBUSY;
 113
 114         cpuidle_curr_driver = drv;
 115
 116         return 0;
 117 }
 118
 119 /**
 120  * __cpuidle_unset_driver - unset the global cpuidle driver variable.
 121  * @drv: a pointer to a struct cpuidle_driver
 122  *
 123  * Reset the global cpuidle variable to NULL.  If @drv does not match the
 124  * registered driver, do nothing.
 125  */
 126 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 127 {
 128         if (drv == cpuidle_curr_driver)
 129                 cpuidle_curr_driver = NULL;
 130 }
 131
 132 #endif
 133
 134 /**
 135  * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer on a cpu
 136  * @arg: a void pointer used to match the SMP cross call API
 137  *
 138  * If @arg is NULL broadcast is disabled otherwise enabled
 139  *
 140  * This function is executed per CPU by an SMP cross call.  It's not
 141  * supposed to be called directly.
 142  */
 143 static void cpuidle_setup_broadcast_timer(void *arg)
 144 {
 145         if (arg)
 146                 tick_broadcast_enable();
 147         else
 148                 tick_broadcast_disable();
 149 }
 150
 151 /**
 152  * __cpuidle_driver_init - initialize the driver's internal data
 153  * @drv: a valid pointer to a struct cpuidle_driver
 154  */
 155 static void __cpuidle_driver_init(struct cpuidle_driver *drv)
 156 {
 157         int i;
 158
 159         /*
 160          * Use all possible CPUs as the default, because if the kernel boots
 161          * with some CPUs offline and then we online one of them, the CPU
 162          * notifier has to know which driver to assign.
 163          */
 164         if (!drv->cpumask)
 165                 drv->cpumask = (struct cpumask *)cpu_possible_mask;
 166
 167         for (i = 0; i < drv->state_count; i++) {
 168                 struct cpuidle_state *s = &drv->states[i];
 169
 170                 /*
 171                  * Look for the timer stop flag in the different states and if
 172                  * it is found, indicate that the broadcast timer has to be set
 173                  * up.
 174                  */
 175                 if (s->flags & CPUIDLE_FLAG_TIMER_STOP)
 176                         drv->bctimer = 1;
 177
 178                 /*
 179                  * The core will use the target residency and exit latency
 180                  * values in nanoseconds, but allow drivers to provide them in
 181                  * microseconds too.
 182                  */
 183                 if (s->target_residency > 0)
 184                         s->target_residency_ns = s->target_residency * NSEC_PER_USEC;
 185                 else if (s->target_residency_ns < 0)
 186                         s->target_residency_ns = 0;
 187                 else
 188                         s->target_residency = div_u64(s->target_residency_ns, NSEC_PER_USEC);
 189
 190                 if (s->exit_latency > 0)
 191                         s->exit_latency_ns = mul_u32_u32(s->exit_latency, NSEC_PER_USEC);
 192                 else if (s->exit_latency_ns < 0)
 193                         s->exit_latency_ns =  0;
 194                 else
 195                         s->exit_latency = div_u64(s->exit_latency_ns, NSEC_PER_USEC);
 196         }
 197 }
 198
 199 /**
 200  * __cpuidle_register_driver: register the driver
 201  * @drv: a valid pointer to a struct cpuidle_driver
 202  *
 203  * Do some sanity checks, initialize the driver, assign the driver to the
 204  * global cpuidle driver variable(s) and set up the broadcast timer if the
 205  * cpuidle driver has some states that shut down the local timer.
 206  *
 207  * Returns 0 on success, a negative error code otherwise:
 208  *  * -EINVAL if the driver pointer is NULL or no idle states are available
 209  *  * -ENODEV if the cpuidle framework is disabled
 210  *  * -EBUSY if the driver is already assigned to the global variable(s)
 211  */
 212 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 213 {
 214         int ret;
 215
 216         if (!drv || !drv->state_count)
 217                 return -EINVAL;
 218
 219         ret = cpuidle_coupled_state_verify(drv);
 220         if (ret)
 221                 return ret;
 222
 223         if (cpuidle_disabled())
 224                 return -ENODEV;
 225
 226         __cpuidle_driver_init(drv);
 227
 228         ret = __cpuidle_set_driver(drv);
 229         if (ret)
 230                 return ret;
 231
 232         if (drv->bctimer)
 233                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 234                                  (void *)1, 1);
 235
 236         return 0;
 237 }
 238
 239 /**
 240  * __cpuidle_unregister_driver - unregister the driver
 241  * @drv: a valid pointer to a struct cpuidle_driver
 242  *
 243  * Check if the driver is no longer in use, reset the global cpuidle driver
 244  * variable(s) and disable the timer broadcast notification mechanism if it was
 245  * in use.
 246  *
 247  */
 248 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 249 {
 250         if (drv->bctimer) {
 251                 drv->bctimer = 0;
 252                 on_each_cpu_mask(drv->cpumask, cpuidle_setup_broadcast_timer,
 253                                  NULL, 1);
 254         }
 255
 256         __cpuidle_unset_driver(drv);
 257 }
 258
 259 /**
 260  * cpuidle_register_driver - registers a driver
 261  * @drv: a pointer to a valid struct cpuidle_driver
 262  *
 263  * Register the driver under a lock to prevent concurrent attempts to
 264  * [un]register the driver from occurring at the same time.
 265  *
 266  * Returns 0 on success, a negative error code (returned by
 267  * __cpuidle_register_driver()) otherwise.
 268  */
 269 int cpuidle_register_driver(struct cpuidle_driver *drv)
 270 {
 271         struct cpuidle_governor *gov;
 272         int ret;
 273
 274         spin_lock(&cpuidle_driver_lock);
 275         ret = __cpuidle_register_driver(drv);
 276         spin_unlock(&cpuidle_driver_lock);
 277
 278         if (!ret && !strlen(param_governor) && drv->governor &&
 279             (cpuidle_get_driver() == drv)) {
 280                 mutex_lock(&cpuidle_lock);
 281                 gov = cpuidle_find_governor(drv->governor);
 282                 if (gov) {
 283                         cpuidle_prev_governor = cpuidle_curr_governor;
 284                         if (cpuidle_switch_governor(gov) < 0)
 285                                 cpuidle_prev_governor = NULL;
 286                 }
 287                 mutex_unlock(&cpuidle_lock);
 288         }
 289
 290         return ret;
 291 }
 292 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 293
 294 /**
 295  * cpuidle_unregister_driver - unregisters a driver
 296  * @drv: a pointer to a valid struct cpuidle_driver
 297  *
 298  * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
 299  * to [un]register the driver from occurring at the same time.  @drv has to
 300  * match the currently registered driver.
 301  */
 302 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 303 {
 304         bool enabled = (cpuidle_get_driver() == drv);
 305
 306         spin_lock(&cpuidle_driver_lock);
 307         __cpuidle_unregister_driver(drv);
 308         spin_unlock(&cpuidle_driver_lock);
 309
 310         if (!enabled)
 311                 return;
 312
 313         mutex_lock(&cpuidle_lock);
 314         if (cpuidle_prev_governor) {
 315                 if (!cpuidle_switch_governor(cpuidle_prev_governor))
 316                         cpuidle_prev_governor = NULL;
 317         }
 318         mutex_unlock(&cpuidle_lock);
 319 }
 320 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 321
 322 /**
 323  * cpuidle_get_driver - return the driver tied to the current CPU.
 324  *
 325  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
 326  */
 327 struct cpuidle_driver *cpuidle_get_driver(void)
 328 {
 329         struct cpuidle_driver *drv;
 330         int cpu;
 331
 332         cpu = get_cpu();
 333         drv = __cpuidle_get_cpu_driver(cpu);
 334         put_cpu();
 335
 336         return drv;
 337 }
 338 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 339
 340 /**
 341  * cpuidle_get_cpu_driver - return the driver registered for a CPU.
 342  * @dev: a valid pointer to a struct cpuidle_device
 343  *
 344  * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
 345  * for the CPU associated with @dev.
 346  */
 347 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 348 {
 349         if (!dev)
 350                 return NULL;
 351
 352         return __cpuidle_get_cpu_driver(dev->cpu);
 353 }
 354 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 355
 356 /**
 357  * cpuidle_driver_state_disabled - Disable or enable an idle state
 358  * @drv: cpuidle driver owning the state
 359  * @idx: State index
 360  * @disable: Whether or not to disable the state
 361  */
 362 void cpuidle_driver_state_disabled(struct cpuidle_driver *drv, int idx,
 363                                  bool disable)
 364 {
 365         unsigned int cpu;
 366
 367         mutex_lock(&cpuidle_lock);
 368
 369         spin_lock(&cpuidle_driver_lock);
 370
 371         if (!drv->cpumask) {
 372                 drv->states[idx].flags |= CPUIDLE_FLAG_UNUSABLE;
 373                 goto unlock;
 374         }
 375
 376         for_each_cpu(cpu, drv->cpumask) {
 377                 struct cpuidle_device *dev = per_cpu(cpuidle_devices, cpu);
 378
 379                 if (!dev)
 380                         continue;
 381
 382                 if (disable)
 383                         dev->states_usage[idx].disable |= CPUIDLE_STATE_DISABLED_BY_DRIVER;
 384                 else
 385                         dev->states_usage[idx].disable &= ~CPUIDLE_STATE_DISABLED_BY_DRIVER;
 386         }
 387
 388 unlock:
 389         spin_unlock(&cpuidle_driver_lock);
 390
 391         mutex_unlock(&cpuidle_lock);
 392 }