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/init.h>
10 #include <linux/kernel.h>
11 #include <linux/pm_domain.h>
12 #include <linux/pm_qos.h>
13 #include <linux/hrtimer.h>
14 
15 #ifdef CONFIG_PM_RUNTIME
16 
17 static int dev_update_qos_constraint(struct device *dev, void *data)
18 {
19 	s64 *constraint_ns_p = data;
20 	s32 constraint_ns = -1;
21 
22 	if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
23 		constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
24 
25 	if (constraint_ns < 0) {
26 		constraint_ns = dev_pm_qos_read_value(dev);
27 		constraint_ns *= NSEC_PER_USEC;
28 	}
29 	if (constraint_ns == 0)
30 		return 0;
31 
32 	/*
33 	 * constraint_ns cannot be negative here, because the device has been
34 	 * suspended.
35 	 */
36 	if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
37 		*constraint_ns_p = constraint_ns;
38 
39 	return 0;
40 }
41 
42 /**
43  * default_stop_ok - Default PM domain governor routine for stopping devices.
44  * @dev: Device to check.
45  */
46 bool default_stop_ok(struct device *dev)
47 {
48 	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
49 	unsigned long flags;
50 	s64 constraint_ns;
51 
52 	dev_dbg(dev, "%s()\n", __func__);
53 
54 	spin_lock_irqsave(&dev->power.lock, flags);
55 
56 	if (!td->constraint_changed) {
57 		bool ret = td->cached_stop_ok;
58 
59 		spin_unlock_irqrestore(&dev->power.lock, flags);
60 		return ret;
61 	}
62 	td->constraint_changed = false;
63 	td->cached_stop_ok = false;
64 	td->effective_constraint_ns = -1;
65 	constraint_ns = __dev_pm_qos_read_value(dev);
66 
67 	spin_unlock_irqrestore(&dev->power.lock, flags);
68 
69 	if (constraint_ns < 0)
70 		return false;
71 
72 	constraint_ns *= NSEC_PER_USEC;
73 	/*
74 	 * We can walk the children without any additional locking, because
75 	 * they all have been suspended at this point and their
76 	 * effective_constraint_ns fields won't be modified in parallel with us.
77 	 */
78 	if (!dev->power.ignore_children)
79 		device_for_each_child(dev, &constraint_ns,
80 				      dev_update_qos_constraint);
81 
82 	if (constraint_ns > 0) {
83 		constraint_ns -= td->start_latency_ns;
84 		if (constraint_ns == 0)
85 			return false;
86 	}
87 	td->effective_constraint_ns = constraint_ns;
88 	td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
89 				constraint_ns == 0;
90 	/*
91 	 * The children have been suspended already, so we don't need to take
92 	 * their stop latencies into account here.
93 	 */
94 	return td->cached_stop_ok;
95 }
96 
97 /**
98  * default_power_down_ok - Default generic PM domain power off governor routine.
99  * @pd: PM domain to check.
100  *
101  * This routine must be executed under the PM domain's lock.
102  */
103 static bool default_power_down_ok(struct dev_pm_domain *pd)
104 {
105 	struct generic_pm_domain *genpd = pd_to_genpd(pd);
106 	struct gpd_link *link;
107 	struct pm_domain_data *pdd;
108 	s64 min_off_time_ns;
109 	s64 off_on_time_ns;
110 
111 	if (genpd->max_off_time_changed) {
112 		struct gpd_link *link;
113 
114 		/*
115 		 * We have to invalidate the cached results for the masters, so
116 		 * use the observation that default_power_down_ok() is not
117 		 * going to be called for any master until this instance
118 		 * returns.
119 		 */
120 		list_for_each_entry(link, &genpd->slave_links, slave_node)
121 			link->master->max_off_time_changed = true;
122 
123 		genpd->max_off_time_changed = false;
124 		genpd->cached_power_down_ok = false;
125 		genpd->max_off_time_ns = -1;
126 	} else {
127 		return genpd->cached_power_down_ok;
128 	}
129 
130 	off_on_time_ns = genpd->power_off_latency_ns +
131 				genpd->power_on_latency_ns;
132 	/*
133 	 * It doesn't make sense to remove power from the domain if saving
134 	 * the state of all devices in it and the power off/power on operations
135 	 * take too much time.
136 	 *
137 	 * All devices in this domain have been stopped already at this point.
138 	 */
139 	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
140 		if (pdd->dev->driver)
141 			off_on_time_ns +=
142 				to_gpd_data(pdd)->td.save_state_latency_ns;
143 	}
144 
145 	min_off_time_ns = -1;
146 	/*
147 	 * Check if subdomains can be off for enough time.
148 	 *
149 	 * All subdomains have been powered off already at this point.
150 	 */
151 	list_for_each_entry(link, &genpd->master_links, master_node) {
152 		struct generic_pm_domain *sd = link->slave;
153 		s64 sd_max_off_ns = sd->max_off_time_ns;
154 
155 		if (sd_max_off_ns < 0)
156 			continue;
157 
158 		/*
159 		 * Check if the subdomain is allowed to be off long enough for
160 		 * the current domain to turn off and on (that's how much time
161 		 * it will have to wait worst case).
162 		 */
163 		if (sd_max_off_ns <= off_on_time_ns)
164 			return false;
165 
166 		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
167 			min_off_time_ns = sd_max_off_ns;
168 	}
169 
170 	/*
171 	 * Check if the devices in the domain can be off enough time.
172 	 */
173 	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
174 		struct gpd_timing_data *td;
175 		s64 constraint_ns;
176 
177 		if (!pdd->dev->driver)
178 			continue;
179 
180 		/*
181 		 * Check if the device is allowed to be off long enough for the
182 		 * domain to turn off and on (that's how much time it will
183 		 * have to wait worst case).
184 		 */
185 		td = &to_gpd_data(pdd)->td;
186 		constraint_ns = td->effective_constraint_ns;
187 		/* default_stop_ok() need not be called before us. */
188 		if (constraint_ns < 0) {
189 			constraint_ns = dev_pm_qos_read_value(pdd->dev);
190 			constraint_ns *= NSEC_PER_USEC;
191 		}
192 		if (constraint_ns == 0)
193 			continue;
194 
195 		/*
196 		 * constraint_ns cannot be negative here, because the device has
197 		 * been suspended.
198 		 */
199 		constraint_ns -= td->restore_state_latency_ns;
200 		if (constraint_ns <= off_on_time_ns)
201 			return false;
202 
203 		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
204 			min_off_time_ns = constraint_ns;
205 	}
206 
207 	genpd->cached_power_down_ok = true;
208 
209 	/*
210 	 * If the computed minimum device off time is negative, there are no
211 	 * latency constraints, so the domain can spend arbitrary time in the
212 	 * "off" state.
213 	 */
214 	if (min_off_time_ns < 0)
215 		return true;
216 
217 	/*
218 	 * The difference between the computed minimum subdomain or device off
219 	 * time and the time needed to turn the domain on is the maximum
220 	 * theoretical time this domain can spend in the "off" state.
221 	 */
222 	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
223 	return true;
224 }
225 
226 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
227 {
228 	return false;
229 }
230 
231 #else /* !CONFIG_PM_RUNTIME */
232 
233 bool default_stop_ok(struct device *dev)
234 {
235 	return false;
236 }
237 
238 #define default_power_down_ok	NULL
239 #define always_on_power_down_ok	NULL
240 
241 #endif /* !CONFIG_PM_RUNTIME */
242 
243 struct dev_power_governor simple_qos_governor = {
244 	.stop_ok = default_stop_ok,
245 	.power_down_ok = default_power_down_ok,
246 };
247 
248 /**
249  * pm_genpd_gov_always_on - A governor implementing an always-on policy
250  */
251 struct dev_power_governor pm_domain_always_on_gov = {
252 	.power_down_ok = always_on_power_down_ok,
253 	.stop_ok = default_stop_ok,
254 };
255