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->suspend_latency_ns +
81 				td->resume_latency_ns;
82 		if (constraint_ns == 0)
83 			return false;
84 	}
85 	td->effective_constraint_ns = constraint_ns;
86 	td->cached_stop_ok = constraint_ns >= 0;
87 
88 	/*
89 	 * The children have been suspended already, so we don't need to take
90 	 * their stop latencies into account here.
91 	 */
92 	return td->cached_stop_ok;
93 }
94 
95 /**
96  * default_power_down_ok - Default generic PM domain power off governor routine.
97  * @pd: PM domain to check.
98  *
99  * This routine must be executed under the PM domain's lock.
100  */
101 static bool default_power_down_ok(struct dev_pm_domain *pd)
102 {
103 	struct generic_pm_domain *genpd = pd_to_genpd(pd);
104 	struct gpd_link *link;
105 	struct pm_domain_data *pdd;
106 	s64 min_off_time_ns;
107 	s64 off_on_time_ns;
108 
109 	if (genpd->max_off_time_changed) {
110 		struct gpd_link *link;
111 
112 		/*
113 		 * We have to invalidate the cached results for the masters, so
114 		 * use the observation that default_power_down_ok() is not
115 		 * going to be called for any master until this instance
116 		 * returns.
117 		 */
118 		list_for_each_entry(link, &genpd->slave_links, slave_node)
119 			link->master->max_off_time_changed = true;
120 
121 		genpd->max_off_time_changed = false;
122 		genpd->cached_power_down_ok = false;
123 		genpd->max_off_time_ns = -1;
124 	} else {
125 		return genpd->cached_power_down_ok;
126 	}
127 
128 	off_on_time_ns = genpd->power_off_latency_ns +
129 				genpd->power_on_latency_ns;
130 
131 	min_off_time_ns = -1;
132 	/*
133 	 * Check if subdomains can be off for enough time.
134 	 *
135 	 * All subdomains have been powered off already at this point.
136 	 */
137 	list_for_each_entry(link, &genpd->master_links, master_node) {
138 		struct generic_pm_domain *sd = link->slave;
139 		s64 sd_max_off_ns = sd->max_off_time_ns;
140 
141 		if (sd_max_off_ns < 0)
142 			continue;
143 
144 		/*
145 		 * Check if the subdomain is allowed to be off long enough for
146 		 * the current domain to turn off and on (that's how much time
147 		 * it will have to wait worst case).
148 		 */
149 		if (sd_max_off_ns <= off_on_time_ns)
150 			return false;
151 
152 		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
153 			min_off_time_ns = sd_max_off_ns;
154 	}
155 
156 	/*
157 	 * Check if the devices in the domain can be off enough time.
158 	 */
159 	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
160 		struct gpd_timing_data *td;
161 		s64 constraint_ns;
162 
163 		/*
164 		 * Check if the device is allowed to be off long enough for the
165 		 * domain to turn off and on (that's how much time it will
166 		 * have to wait worst case).
167 		 */
168 		td = &to_gpd_data(pdd)->td;
169 		constraint_ns = td->effective_constraint_ns;
170 		/* default_stop_ok() need not be called before us. */
171 		if (constraint_ns < 0) {
172 			constraint_ns = dev_pm_qos_read_value(pdd->dev);
173 			constraint_ns *= NSEC_PER_USEC;
174 		}
175 		if (constraint_ns == 0)
176 			continue;
177 
178 		/*
179 		 * constraint_ns cannot be negative here, because the device has
180 		 * been suspended.
181 		 */
182 		if (constraint_ns <= off_on_time_ns)
183 			return false;
184 
185 		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
186 			min_off_time_ns = constraint_ns;
187 	}
188 
189 	genpd->cached_power_down_ok = true;
190 
191 	/*
192 	 * If the computed minimum device off time is negative, there are no
193 	 * latency constraints, so the domain can spend arbitrary time in the
194 	 * "off" state.
195 	 */
196 	if (min_off_time_ns < 0)
197 		return true;
198 
199 	/*
200 	 * The difference between the computed minimum subdomain or device off
201 	 * time and the time needed to turn the domain on is the maximum
202 	 * theoretical time this domain can spend in the "off" state.
203 	 */
204 	genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
205 	return true;
206 }
207 
208 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
209 {
210 	return false;
211 }
212 
213 struct dev_power_governor simple_qos_governor = {
214 	.stop_ok = default_stop_ok,
215 	.power_down_ok = default_power_down_ok,
216 };
217 
218 /**
219  * pm_genpd_gov_always_on - A governor implementing an always-on policy
220  */
221 struct dev_power_governor pm_domain_always_on_gov = {
222 	.power_down_ok = always_on_power_down_ok,
223 	.stop_ok = default_stop_ok,
224 };
225