Root/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
17static struct cpuidle_driver *cpuidle_curr_driver;
18DEFINE_SPINLOCK(cpuidle_driver_lock);
19int cpuidle_driver_refcount;
20
21static 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 */
49int 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
69EXPORT_SYMBOL_GPL(cpuidle_register_driver);
70
71/**
72 * cpuidle_get_driver - return the current driver
73 */
74struct cpuidle_driver *cpuidle_get_driver(void)
75{
76    return cpuidle_curr_driver;
77}
78EXPORT_SYMBOL_GPL(cpuidle_get_driver);
79
80/**
81 * cpuidle_unregister_driver - unregisters a driver
82 * @drv: the driver
83 */
84void 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
100EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
101
102struct 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
115void 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

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