Pileus Git - ~andy/linux/blob - 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 __cpuidle_register_driver(struct cpuidle_driver *drv)
  22 {
  23         int i;
  24         /*
  25          * cpuidle driver should set the drv->power_specified bit
  26          * before registering if the driver provides
  27          * power_usage numbers.
  28          *
  29          * If power_specified is not set,
  30          * we fill in power_usage with decreasing values as the
  31          * cpuidle code has an implicit assumption that state Cn
  32          * uses less power than C(n-1).
  33          *
  34          * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
  35          * an power value of -1.  So we use -2, -3, etc, for other
  36          * c-states.
  37          */
  38         if (!drv->power_specified) {
  39                 for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
  40                         drv->states[i].power_usage = -1 - i;
  41         }
  42 }
  43
  44
  45 /**
  46  * cpuidle_register_driver - registers a driver
  47  * @drv: the driver
  48  */
  49 int cpuidle_register_driver(struct cpuidle_driver *drv)
  50 {
  51         if (!drv || !drv->state_count)
  52                 return -EINVAL;
  53
  54         if (cpuidle_disabled())
  55                 return -ENODEV;
  56
  57         spin_lock(&cpuidle_driver_lock);
  58         if (cpuidle_curr_driver) {
  59                 spin_unlock(&cpuidle_driver_lock);
  60                 return -EBUSY;
  61         }
  62         __cpuidle_register_driver(drv);
  63         cpuidle_curr_driver = drv;
  64         spin_unlock(&cpuidle_driver_lock);
  65
  66         return 0;
  67 }
  68
  69 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
  70
  71 /**
  72  * cpuidle_get_driver - return the current driver
  73  */
  74 struct cpuidle_driver *cpuidle_get_driver(void)
  75 {
  76         return cpuidle_curr_driver;
  77 }
  78 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
  79
  80 /**
  81  * cpuidle_unregister_driver - unregisters a driver
  82  * @drv: the driver
  83  */
  84 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
  85 {
  86         if (drv != cpuidle_curr_driver) {
  87                 WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
  88                         drv->name);
  89                 return;
  90         }
  91
  92         spin_lock(&cpuidle_driver_lock);
  93
  94         if (!WARN_ON(cpuidle_driver_refcount > 0))
  95                 cpuidle_curr_driver = NULL;
  96
  97         spin_unlock(&cpuidle_driver_lock);
  98 }
  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 }