summaryrefslogtreecommitdiffstats
path: root/drivers/base/power/domain_governor.c
blob: 51527ee92d101018680cd5b633265105a2952df1 (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
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
/*
 * drivers/base/power/domain_governor.c - Governors for device PM domains.
 *
 * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
 *
 * This file is released under the GPLv2.
 */

#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/pm_domain.h>
#include <linux/pm_qos.h>
#include <linux/hrtimer.h>

/**
 * default_stop_ok - Default PM domain governor routine for stopping devices.
 * @dev: Device to check.
 */
bool default_stop_ok(struct device *dev)
{
	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;

	dev_dbg(dev, "%s()\n", __func__);

	if (dev->power.max_time_suspended_ns < 0 || td->break_even_ns == 0)
		return true;

	return td->stop_latency_ns + td->start_latency_ns < td->break_even_ns
		&& td->break_even_ns < dev->power.max_time_suspended_ns;
}

/**
 * default_power_down_ok - Default generic PM domain power off governor routine.
 * @pd: PM domain to check.
 *
 * This routine must be executed under the PM domain's lock.
 */
static bool default_power_down_ok(struct dev_pm_domain *pd)
{
	struct generic_pm_domain *genpd = pd_to_genpd(pd);
	struct gpd_link *link;
	struct pm_domain_data *pdd;
	s64 min_dev_off_time_ns;
	s64 off_on_time_ns;
	ktime_t time_now = ktime_get();

	off_on_time_ns = genpd->power_off_latency_ns +
				genpd->power_on_latency_ns;
	/*
	 * It doesn't make sense to remove power from the domain if saving
	 * the state of all devices in it and the power off/power on operations
	 * take too much time.
	 *
	 * All devices in this domain have been stopped already at this point.
	 */
	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
		if (pdd->dev->driver)
			off_on_time_ns +=
				to_gpd_data(pdd)->td.save_state_latency_ns;
	}

	/*
	 * Check if subdomains can be off for enough time.
	 *
	 * All subdomains have been powered off already at this point.
	 */
	list_for_each_entry(link, &genpd->master_links, master_node) {
		struct generic_pm_domain *sd = link->slave;
		s64 sd_max_off_ns = sd->max_off_time_ns;

		if (sd_max_off_ns < 0)
			continue;

		sd_max_off_ns -= ktime_to_ns(ktime_sub(time_now,
						       sd->power_off_time));
		/*
		 * Check if the subdomain is allowed to be off long enough for
		 * the current domain to turn off and on (that's how much time
		 * it will have to wait worst case).
		 */
		if (sd_max_off_ns <= off_on_time_ns)
			return false;
	}

	/*
	 * Check if the devices in the domain can be off enough time.
	 */
	min_dev_off_time_ns = -1;
	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
		struct gpd_timing_data *td;
		struct device *dev = pdd->dev;
		s64 dev_off_time_ns;

		if (!dev->driver || dev->power.max_time_suspended_ns < 0)
			continue;

		td = &to_gpd_data(pdd)->td;
		dev_off_time_ns = dev->power.max_time_suspended_ns -
			(td->start_latency_ns + td->restore_state_latency_ns +
				ktime_to_ns(ktime_sub(time_now,
						dev->power.suspend_time)));
		if (dev_off_time_ns <= off_on_time_ns)
			return false;

		if (min_dev_off_time_ns > dev_off_time_ns
		    || min_dev_off_time_ns < 0)
			min_dev_off_time_ns = dev_off_time_ns;
	}

	if (min_dev_off_time_ns < 0) {
		/*
		 * There are no latency constraints, so the domain can spend
		 * arbitrary time in the "off" state.
		 */
		genpd->max_off_time_ns = -1;
		return true;
	}

	/*
	 * The difference between the computed minimum delta and the time needed
	 * to turn the domain on is the maximum theoretical time this domain can
	 * spend in the "off" state.
	 */
	min_dev_off_time_ns -= genpd->power_on_latency_ns;

	/*
	 * If the difference between the computed minimum delta and the time
	 * needed to turn the domain off and back on on is smaller than the
	 * domain's power break even time, removing power from the domain is not
	 * worth it.
	 */
	if (genpd->break_even_ns >
	    min_dev_off_time_ns - genpd->power_off_latency_ns)
		return false;

	genpd->max_off_time_ns = min_dev_off_time_ns;
	return true;
}

struct dev_power_governor simple_qos_governor = {
	.stop_ok = default_stop_ok,
	.power_down_ok = default_power_down_ok,
};

static bool always_on_power_down_ok(struct dev_pm_domain *domain)
{
	return false;
}

/**
 * pm_genpd_gov_always_on - A governor implementing an always-on policy
 */
struct dev_power_governor pm_domain_always_on_gov = {
	.power_down_ok = always_on_power_down_ok,
	.stop_ok = default_stop_ok,
};
OpenPOWER on IntegriCloud