1/*
2 * drivers/base/power/domain_governor.c - Governors for device PM domains.
3 *
4 * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
5 *
6 * This file is released under the GPLv2.
7 */
8
9#include <linux/kernel.h>
10#include <linux/pm_domain.h>
11#include <linux/pm_qos.h>
12#include <linux/hrtimer.h>
13
14static int dev_update_qos_constraint(struct device *dev, void *data)
15{
16	s64 *constraint_ns_p = data;
17	s32 constraint_ns = -1;
18
19	if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
20		constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
21
22	if (constraint_ns < 0) {
23		constraint_ns = dev_pm_qos_read_value(dev);
24		constraint_ns *= NSEC_PER_USEC;
25	}
26	if (constraint_ns == 0)
27		return 0;
28
29	/*
30	 * constraint_ns cannot be negative here, because the device has been
31	 * suspended.
32	 */
33	if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
34		*constraint_ns_p = constraint_ns;
35
36	return 0;
37}
38
39/**
40 * default_stop_ok - Default PM domain governor routine for stopping devices.
41 * @dev: Device to check.
42 */
43static bool default_stop_ok(struct device *dev)
44{
45	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
46	unsigned long flags;
47	s64 constraint_ns;
48
49	dev_dbg(dev, "%s()\n", __func__);
50
51	spin_lock_irqsave(&dev->power.lock, flags);
52
53	if (!td->constraint_changed) {
54		bool ret = td->cached_stop_ok;
55
56		spin_unlock_irqrestore(&dev->power.lock, flags);
57		return ret;
58	}
59	td->constraint_changed = false;
60	td->cached_stop_ok = false;
61	td->effective_constraint_ns = -1;
62	constraint_ns = __dev_pm_qos_read_value(dev);
63
64	spin_unlock_irqrestore(&dev->power.lock, flags);
65
66	if (constraint_ns < 0)
67		return false;
68
69	constraint_ns *= NSEC_PER_USEC;
70	/*
71	 * We can walk the children without any additional locking, because
72	 * they all have been suspended at this point and their
73	 * effective_constraint_ns fields won't be modified in parallel with us.
74	 */
75	if (!dev->power.ignore_children)
76		device_for_each_child(dev, &constraint_ns,
77				      dev_update_qos_constraint);
78
79	if (constraint_ns > 0) {
80		constraint_ns -= td->start_latency_ns;
81		if (constraint_ns == 0)
82			return false;
83	}
84	td->effective_constraint_ns = constraint_ns;
85	td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
86				constraint_ns == 0;
87	/*
88	 * The children have been suspended already, so we don't need to take
89	 * their stop latencies into account here.
90	 */
91	return td->cached_stop_ok;
92}
93
94/**
95 * default_power_down_ok - Default generic PM domain power off governor routine.
96 * @pd: PM domain to check.
97 *
98 * This routine must be executed under the PM domain's lock.
99 */
100static bool default_power_down_ok(struct dev_pm_domain *pd)
101{
102	struct generic_pm_domain *genpd = pd_to_genpd(pd);
103	struct gpd_link *link;
104	struct pm_domain_data *pdd;
105	s64 min_off_time_ns;
106	s64 off_on_time_ns;
107
108	if (genpd->max_off_time_changed) {
109		struct gpd_link *link;
110
111		/*
112		 * We have to invalidate the cached results for the masters, so
113		 * use the observation that default_power_down_ok() is not
114		 * going to be called for any master until this instance
115		 * returns.
116		 */
117		list_for_each_entry(link, &genpd->slave_links, slave_node)
118			link->master->max_off_time_changed = true;
119
120		genpd->max_off_time_changed = false;
121		genpd->cached_power_down_ok = false;
122		genpd->max_off_time_ns = -1;
123	} else {
124		return genpd->cached_power_down_ok;
125	}
126
127	off_on_time_ns = genpd->power_off_latency_ns +
128				genpd->power_on_latency_ns;
129	/*
130	 * It doesn't make sense to remove power from the domain if saving
131	 * the state of all devices in it and the power off/power on operations
132	 * take too much time.
133	 *
134	 * All devices in this domain have been stopped already at this point.
135	 */
136	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
137		if (pdd->dev->driver)
138			off_on_time_ns +=
139				to_gpd_data(pdd)->td.save_state_latency_ns;
140	}
141
142	min_off_time_ns = -1;
143	/*
144	 * Check if subdomains can be off for enough time.
145	 *
146	 * All subdomains have been powered off already at this point.
147	 */
148	list_for_each_entry(link, &genpd->master_links, master_node) {
149		struct generic_pm_domain *sd = link->slave;
150		s64 sd_max_off_ns = sd->max_off_time_ns;
151
152		if (sd_max_off_ns < 0)
153			continue;
154
155		/*
156		 * Check if the subdomain is allowed to be off long enough for
157		 * the current domain to turn off and on (that's how much time
158		 * it will have to wait worst case).
159		 */
160		if (sd_max_off_ns <= off_on_time_ns)
161			return false;
162
163		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
164			min_off_time_ns = sd_max_off_ns;
165	}
166
167	/*
168	 * Check if the devices in the domain can be off enough time.
169	 */
170	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
171		struct gpd_timing_data *td;
172		s64 constraint_ns;
173
174		if (!pdd->dev->driver)
175			continue;
176
177		/*
178		 * Check if the device is allowed to be off long enough for the
179		 * domain to turn off and on (that's how much time it will
180		 * have to wait worst case).
181		 */
182		td = &to_gpd_data(pdd)->td;
183		constraint_ns = td->effective_constraint_ns;
184		/* default_stop_ok() need not be called before us. */
185		if (constraint_ns < 0) {
186			constraint_ns = dev_pm_qos_read_value(pdd->dev);
187			constraint_ns *= NSEC_PER_USEC;
188		}
189		if (constraint_ns == 0)
190			continue;
191
192		/*
193		 * constraint_ns cannot be negative here, because the device has
194		 * been suspended.
195		 */
196		constraint_ns -= td->restore_state_latency_ns;
197		if (constraint_ns <= off_on_time_ns)
198			return false;
199
200		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
201			min_off_time_ns = constraint_ns;
202	}
203
204	genpd->cached_power_down_ok = true;
205
206	/*
207	 * If the computed minimum device off time is negative, there are no
208	 * latency constraints, so the domain can spend arbitrary time in the
209	 * "off" state.
210	 */
211	if (min_off_time_ns < 0)
212		return true;
213
214	/*
215	 * The difference between the computed minimum subdomain or device off
216	 * time and the time needed to turn the domain on is the maximum
217	 * theoretical time this domain can spend in the "off" state.
218	 */
219	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
220	return true;
221}
222
223static bool always_on_power_down_ok(struct dev_pm_domain *domain)
224{
225	return false;
226}
227
228struct dev_power_governor simple_qos_governor = {
229	.stop_ok = default_stop_ok,
230	.power_down_ok = default_power_down_ok,
231};
232
233/**
234 * pm_genpd_gov_always_on - A governor implementing an always-on policy
235 */
236struct dev_power_governor pm_domain_always_on_gov = {
237	.power_down_ok = always_on_power_down_ok,
238	.stop_ok = default_stop_ok,
239};
240