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 } 124