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 
14 static 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  */
43 static 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  */
100 static 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 
223 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
224 {
225 	return false;
226 }
227 
228 struct 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  */
236 struct 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