summaryrefslogtreecommitdiff
path: root/drivers/base/power/domain_governor.c
blob: e60dd12e23aaee75a2a0d90ba0ba720c28c769e7 (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
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
/*
 * 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/kernel.h>
#include <linux/pm_domain.h>
#include <linux/pm_qos.h>
#include <linux/hrtimer.h>

static int dev_update_qos_constraint(struct device *dev, void *data)
{
	s64 *constraint_ns_p = data;
	s32 constraint_ns = -1;

	if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
		constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;

	if (constraint_ns < 0) {
		constraint_ns = dev_pm_qos_read_value(dev);
		constraint_ns *= NSEC_PER_USEC;
	}
	if (constraint_ns == 0)
		return 0;

	/*
	 * constraint_ns cannot be negative here, because the device has been
	 * suspended.
	 */
	if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
		*constraint_ns_p = constraint_ns;

	return 0;
}

/**
 * default_stop_ok - Default PM domain governor routine for stopping devices.
 * @dev: Device to check.
 */
static bool default_stop_ok(struct device *dev)
{
	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
	unsigned long flags;
	s64 constraint_ns;

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

	spin_lock_irqsave(&dev->power.lock, flags);

	if (!td->constraint_changed) {
		bool ret = td->cached_stop_ok;

		spin_unlock_irqrestore(&dev->power.lock, flags);
		return ret;
	}
	td->constraint_changed = false;
	td->cached_stop_ok = false;
	td->effective_constraint_ns = -1;
	constraint_ns = __dev_pm_qos_read_value(dev);

	spin_unlock_irqrestore(&dev->power.lock, flags);

	if (constraint_ns < 0)
		return false;

	constraint_ns *= NSEC_PER_USEC;
	/*
	 * We can walk the children without any additional locking, because
	 * they all have been suspended at this point and their
	 * effective_constraint_ns fields won't be modified in parallel with us.
	 */
	if (!dev->power.ignore_children)
		device_for_each_child(dev, &constraint_ns,
				      dev_update_qos_constraint);

	if (constraint_ns > 0) {
		constraint_ns -= td->suspend_latency_ns +
				td->resume_latency_ns;
		if (constraint_ns == 0)
			return false;
	}
	td->effective_constraint_ns = constraint_ns;
	td->cached_stop_ok = constraint_ns >= 0;

	/*
	 * The children have been suspended already, so we don't need to take
	 * their stop latencies into account here.
	 */
	return td->cached_stop_ok;
}

/**
 * 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_off_time_ns;
	s64 off_on_time_ns;

	if (genpd->max_off_time_changed) {
		struct gpd_link *link;

		/*
		 * We have to invalidate the cached results for the masters, so
		 * use the observation that default_power_down_ok() is not
		 * going to be called for any master until this instance
		 * returns.
		 */
		list_for_each_entry(link, &genpd->slave_links, slave_node)
			link->master->max_off_time_changed = true;

		genpd->max_off_time_changed = false;
		genpd->cached_power_down_ok = false;
		genpd->max_off_time_ns = -1;
	} else {
		return genpd->cached_power_down_ok;
	}

	off_on_time_ns = genpd->power_off_latency_ns +
				genpd->power_on_latency_ns;

	min_off_time_ns = -1;
	/*
	 * 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;

		/*
		 * 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;

		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
			min_off_time_ns = sd_max_off_ns;
	}

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

		if (!pdd->dev->driver)
			continue;

		/*
		 * Check if the device is allowed to be off long enough for the
		 * domain to turn off and on (that's how much time it will
		 * have to wait worst case).
		 */
		td = &to_gpd_data(pdd)->td;
		constraint_ns = td->effective_constraint_ns;
		/* default_stop_ok() need not be called before us. */
		if (constraint_ns < 0) {
			constraint_ns = dev_pm_qos_read_value(pdd->dev);
			constraint_ns *= NSEC_PER_USEC;
		}
		if (constraint_ns == 0)
			continue;

		/*
		 * constraint_ns cannot be negative here, because the device has
		 * been suspended.
		 */
		if (constraint_ns <= off_on_time_ns)
			return false;

		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
			min_off_time_ns = constraint_ns;
	}

	genpd->cached_power_down_ok = true;

	/*
	 * If the computed minimum device off time is negative, there are no
	 * latency constraints, so the domain can spend arbitrary time in the
	 * "off" state.
	 */
	if (min_off_time_ns < 0)
		return true;

	/*
	 * The difference between the computed minimum subdomain or device off
	 * time and the time needed to turn the domain on is the maximum
	 * theoretical time this domain can spend in the "off" state.
	 */
	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
	return true;
}

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

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

/**
 * 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,
};