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->save_state_latency_ns +
81 				td->stop_latency_ns +
82 				td->start_latency_ns +
83 				td->restore_state_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 >= 0;
89 
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 	min_off_time_ns = -1;
134 	/*
135 	 * Check if subdomains can be off for enough time.
136 	 *
137 	 * All subdomains have been powered off already at this point.
138 	 */
139 	list_for_each_entry(link, &genpd->master_links, master_node) {
140 		struct generic_pm_domain *sd = link->slave;
141 		s64 sd_max_off_ns = sd->max_off_time_ns;
142 
143 		if (sd_max_off_ns < 0)
144 			continue;
145 
146 		/*
147 		 * Check if the subdomain is allowed to be off long enough for
148 		 * the current domain to turn off and on (that's how much time
149 		 * it will have to wait worst case).
150 		 */
151 		if (sd_max_off_ns <= off_on_time_ns)
152 			return false;
153 
154 		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
155 			min_off_time_ns = sd_max_off_ns;
156 	}
157 
158 	/*
159 	 * Check if the devices in the domain can be off enough time.
160 	 */
161 	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
162 		struct gpd_timing_data *td;
163 		s64 constraint_ns;
164 
165 		if (!pdd->dev->driver)
166 			continue;
167 
168 		/*
169 		 * Check if the device is allowed to be off long enough for the
170 		 * domain to turn off and on (that's how much time it will
171 		 * have to wait worst case).
172 		 */
173 		td = &to_gpd_data(pdd)->td;
174 		constraint_ns = td->effective_constraint_ns;
175 		/* default_stop_ok() need not be called before us. */
176 		if (constraint_ns < 0) {
177 			constraint_ns = dev_pm_qos_read_value(pdd->dev);
178 			constraint_ns *= NSEC_PER_USEC;
179 		}
180 		if (constraint_ns == 0)
181 			continue;
182 
183 		/*
184 		 * constraint_ns cannot be negative here, because the device has
185 		 * been suspended.
186 		 */
187 		if (constraint_ns <= off_on_time_ns)
188 			return false;
189 
190 		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
191 			min_off_time_ns = constraint_ns;
192 	}
193 
194 	genpd->cached_power_down_ok = true;
195 
196 	/*
197 	 * If the computed minimum device off time is negative, there are no
198 	 * latency constraints, so the domain can spend arbitrary time in the
199 	 * "off" state.
200 	 */
201 	if (min_off_time_ns < 0)
202 		return true;
203 
204 	/*
205 	 * The difference between the computed minimum subdomain or device off
206 	 * time and the time needed to turn the domain on is the maximum
207 	 * theoretical time this domain can spend in the "off" state.
208 	 */
209 	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
210 	return true;
211 }
212 
213 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
214 {
215 	return false;
216 }
217 
218 struct dev_power_governor simple_qos_governor = {
219 	.stop_ok = default_stop_ok,
220 	.power_down_ok = default_power_down_ok,
221 };
222 
223 /**
224  * pm_genpd_gov_always_on - A governor implementing an always-on policy
225  */
226 struct dev_power_governor pm_domain_always_on_gov = {
227 	.power_down_ok = always_on_power_down_ok,
228 	.stop_ok = default_stop_ok,
229 };
230