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/cpuidle.h>
  14
  15 #include "cpuidle.h"
  16
  17 static struct cpuidle_driver *cpuidle_curr_driver;
  18 DEFINE_SPINLOCK(cpuidle_driver_lock);
  19 int cpuidle_driver_refcount;
  20
  21 static void set_power_states(struct cpuidle_driver *drv)
  22 {
  23         int i;
  24
  25         /*
  26          * cpuidle driver should set the drv->power_specified bit
  27          * before registering if the driver provides
  28          * power_usage numbers.
  29          *
  30          * If power_specified is not set,
  31          * we fill in power_usage with decreasing values as the
  32          * cpuidle code has an implicit assumption that state Cn
  33          * uses less power than C(n-1).
  34          *
  35          * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
  36          * an power value of -1.  So we use -2, -3, etc, for other
  37          * c-states.
  38          */
  39         for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
  40                 drv->states[i].power_usage = -1 - i;
  41 }
  42
  43 /**
  44  * cpuidle_register_driver - registers a driver
  45  * @drv: the driver
  46  */
  47 int cpuidle_register_driver(struct cpuidle_driver *drv)
  48 {
  49         if (!drv || !drv->state_count)
  50                 return -EINVAL;
  51
  52         if (cpuidle_disabled())
  53                 return -ENODEV;
  54
  55         spin_lock(&cpuidle_driver_lock);
  56         if (cpuidle_curr_driver) {
  57                 spin_unlock(&cpuidle_driver_lock);
  58                 return -EBUSY;
  59         }
  60
  61         if (!drv->power_specified)
  62                 set_power_states(drv);
  63
  64         cpuidle_curr_driver = drv;
  65
  66         spin_unlock(&cpuidle_driver_lock);
  67
  68         return 0;
  69 }
  70 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
  71
  72 /**
  73  * cpuidle_get_driver - return the current driver
  74  */
  75 struct cpuidle_driver *cpuidle_get_driver(void)
  76 {
  77         return cpuidle_curr_driver;
  78 }
  79 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
  80
  81 /**
  82  * cpuidle_unregister_driver - unregisters a driver
  83  * @drv: the driver
  84  */
  85 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
  86 {
  87         if (drv != cpuidle_curr_driver) {
  88                 WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
  89                         drv->name);
  90                 return;
  91         }
  92
  93         spin_lock(&cpuidle_driver_lock);
  94
  95         if (!WARN_ON(cpuidle_driver_refcount > 0))
  96                 cpuidle_curr_driver = NULL;
  97
  98         spin_unlock(&cpuidle_driver_lock);
  99 }
 100 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 101
 102 struct cpuidle_driver *cpuidle_driver_ref(void)
 103 {
 104         struct cpuidle_driver *drv;
 105
 106         spin_lock(&cpuidle_driver_lock);
 107
 108         drv = cpuidle_curr_driver;
 109         cpuidle_driver_refcount++;
 110
 111         spin_unlock(&cpuidle_driver_lock);
 112         return drv;
 113 }
 114
 115 void cpuidle_driver_unref(void)
 116 {
 117         spin_lock(&cpuidle_driver_lock);
 118
 119         if (!WARN_ON(cpuidle_driver_refcount <= 0))
 120                 cpuidle_driver_refcount--;
 121
 122         spin_unlock(&cpuidle_driver_lock);
 123 }