summaryrefslogtreecommitdiff
path: root/drivers/cpuidle/driver.c
blob: 87db3877fead7280d93eaf53baabcc6e4fe0f043 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
/*
 * driver.c - driver support
 *
 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *               Shaohua Li <shaohua.li@intel.com>
 *               Adam Belay <abelay@novell.com>
 *
 * This code is licenced under the GPL.
 */

#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/cpuidle.h>

#include "cpuidle.h"

static struct cpuidle_driver *cpuidle_curr_driver;
DEFINE_SPINLOCK(cpuidle_driver_lock);
int cpuidle_driver_refcount;

static void set_power_states(struct cpuidle_driver *drv)
{
	int i;

	/*
	 * cpuidle driver should set the drv->power_specified bit
	 * before registering if the driver provides
	 * power_usage numbers.
	 *
	 * If power_specified is not set,
	 * we fill in power_usage with decreasing values as the
	 * cpuidle code has an implicit assumption that state Cn
	 * uses less power than C(n-1).
	 *
	 * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
	 * an power value of -1.  So we use -2, -3, etc, for other
	 * c-states.
	 */
	for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
		drv->states[i].power_usage = -1 - i;
}

/**
 * cpuidle_register_driver - registers a driver
 * @drv: the driver
 */
int cpuidle_register_driver(struct cpuidle_driver *drv)
{
	if (!drv || !drv->state_count)
		return -EINVAL;

	if (cpuidle_disabled())
		return -ENODEV;

	spin_lock(&cpuidle_driver_lock);
	if (cpuidle_curr_driver) {
		spin_unlock(&cpuidle_driver_lock);
		return -EBUSY;
	}

	if (!drv->power_specified)
		set_power_states(drv);

	cpuidle_curr_driver = drv;

	spin_unlock(&cpuidle_driver_lock);

	return 0;
}
EXPORT_SYMBOL_GPL(cpuidle_register_driver);

/**
 * cpuidle_get_driver - return the current driver
 */
struct cpuidle_driver *cpuidle_get_driver(void)
{
	return cpuidle_curr_driver;
}
EXPORT_SYMBOL_GPL(cpuidle_get_driver);

/**
 * cpuidle_unregister_driver - unregisters a driver
 * @drv: the driver
 */
void cpuidle_unregister_driver(struct cpuidle_driver *drv)
{
	if (drv != cpuidle_curr_driver) {
		WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
			drv->name);
		return;
	}

	spin_lock(&cpuidle_driver_lock);

	if (!WARN_ON(cpuidle_driver_refcount > 0))
		cpuidle_curr_driver = NULL;

	spin_unlock(&cpuidle_driver_lock);
}
EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);

struct cpuidle_driver *cpuidle_driver_ref(void)
{
	struct cpuidle_driver *drv;

	spin_lock(&cpuidle_driver_lock);

	drv = cpuidle_curr_driver;
	cpuidle_driver_refcount++;

	spin_unlock(&cpuidle_driver_lock);
	return drv;
}

void cpuidle_driver_unref(void)
{
	spin_lock(&cpuidle_driver_lock);

	if (!WARN_ON(cpuidle_driver_refcount <= 0))
		cpuidle_driver_refcount--;

	spin_unlock(&cpuidle_driver_lock);
}