1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * drivers/base/power/domain_governor.c - Governors for device PM domains.
4  *
5  * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
6  */
7 #include <linux/kernel.h>
8 #include <linux/pm_domain.h>
9 #include <linux/pm_qos.h>
10 #include <linux/hrtimer.h>
11 #include <linux/cpuidle.h>
12 #include <linux/cpumask.h>
13 #include <linux/ktime.h>
14 
15 static int dev_update_qos_constraint(struct device *dev, void *data)
16 {
17 	s64 *constraint_ns_p = data;
18 	s64 constraint_ns;
19 
20 	if (dev->power.subsys_data && dev->power.subsys_data->domain_data) {
21 		/*
22 		 * Only take suspend-time QoS constraints of devices into
23 		 * account, because constraints updated after the device has
24 		 * been suspended are not guaranteed to be taken into account
25 		 * anyway.  In order for them to take effect, the device has to
26 		 * be resumed and suspended again.
27 		 */
28 		constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
29 	} else {
30 		/*
31 		 * The child is not in a domain and there's no info on its
32 		 * suspend/resume latencies, so assume them to be negligible and
33 		 * take its current PM QoS constraint (that's the only thing
34 		 * known at this point anyway).
35 		 */
36 		constraint_ns = dev_pm_qos_read_value(dev);
37 		constraint_ns *= NSEC_PER_USEC;
38 	}
39 
40 	if (constraint_ns < *constraint_ns_p)
41 		*constraint_ns_p = constraint_ns;
42 
43 	return 0;
44 }
45 
46 /**
47  * default_suspend_ok - Default PM domain governor routine to suspend devices.
48  * @dev: Device to check.
49  */
50 static bool default_suspend_ok(struct device *dev)
51 {
52 	struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
53 	unsigned long flags;
54 	s64 constraint_ns;
55 
56 	dev_dbg(dev, "%s()\n", __func__);
57 
58 	spin_lock_irqsave(&dev->power.lock, flags);
59 
60 	if (!td->constraint_changed) {
61 		bool ret = td->cached_suspend_ok;
62 
63 		spin_unlock_irqrestore(&dev->power.lock, flags);
64 		return ret;
65 	}
66 	td->constraint_changed = false;
67 	td->cached_suspend_ok = false;
68 	td->effective_constraint_ns = 0;
69 	constraint_ns = __dev_pm_qos_read_value(dev);
70 
71 	spin_unlock_irqrestore(&dev->power.lock, flags);
72 
73 	if (constraint_ns == 0)
74 		return false;
75 
76 	constraint_ns *= NSEC_PER_USEC;
77 	/*
78 	 * We can walk the children without any additional locking, because
79 	 * they all have been suspended at this point and their
80 	 * effective_constraint_ns fields won't be modified in parallel with us.
81 	 */
82 	if (!dev->power.ignore_children)
83 		device_for_each_child(dev, &constraint_ns,
84 				      dev_update_qos_constraint);
85 
86 	if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) {
87 		/* "No restriction", so the device is allowed to suspend. */
88 		td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
89 		td->cached_suspend_ok = true;
90 	} else if (constraint_ns == 0) {
91 		/*
92 		 * This triggers if one of the children that don't belong to a
93 		 * domain has a zero PM QoS constraint and it's better not to
94 		 * suspend then.  effective_constraint_ns is zero already and
95 		 * cached_suspend_ok is false, so bail out.
96 		 */
97 		return false;
98 	} else {
99 		constraint_ns -= td->suspend_latency_ns +
100 				td->resume_latency_ns;
101 		/*
102 		 * effective_constraint_ns is zero already and cached_suspend_ok
103 		 * is false, so if the computed value is not positive, return
104 		 * right away.
105 		 */
106 		if (constraint_ns <= 0)
107 			return false;
108 
109 		td->effective_constraint_ns = constraint_ns;
110 		td->cached_suspend_ok = true;
111 	}
112 
113 	/*
114 	 * The children have been suspended already, so we don't need to take
115 	 * their suspend latencies into account here.
116 	 */
117 	return td->cached_suspend_ok;
118 }
119 
120 static bool __default_power_down_ok(struct dev_pm_domain *pd,
121 				     unsigned int state)
122 {
123 	struct generic_pm_domain *genpd = pd_to_genpd(pd);
124 	struct gpd_link *link;
125 	struct pm_domain_data *pdd;
126 	s64 min_off_time_ns;
127 	s64 off_on_time_ns;
128 
129 	off_on_time_ns = genpd->states[state].power_off_latency_ns +
130 		genpd->states[state].power_on_latency_ns;
131 
132 	min_off_time_ns = -1;
133 	/*
134 	 * Check if subdomains can be off for enough time.
135 	 *
136 	 * All subdomains have been powered off already at this point.
137 	 */
138 	list_for_each_entry(link, &genpd->master_links, master_node) {
139 		struct generic_pm_domain *sd = link->slave;
140 		s64 sd_max_off_ns = sd->max_off_time_ns;
141 
142 		if (sd_max_off_ns < 0)
143 			continue;
144 
145 		/*
146 		 * Check if the subdomain is allowed to be off long enough for
147 		 * the current domain to turn off and on (that's how much time
148 		 * it will have to wait worst case).
149 		 */
150 		if (sd_max_off_ns <= off_on_time_ns)
151 			return false;
152 
153 		if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
154 			min_off_time_ns = sd_max_off_ns;
155 	}
156 
157 	/*
158 	 * Check if the devices in the domain can be off enough time.
159 	 */
160 	list_for_each_entry(pdd, &genpd->dev_list, list_node) {
161 		struct gpd_timing_data *td;
162 		s64 constraint_ns;
163 
164 		/*
165 		 * Check if the device is allowed to be off long enough for the
166 		 * domain to turn off and on (that's how much time it will
167 		 * have to wait worst case).
168 		 */
169 		td = &to_gpd_data(pdd)->td;
170 		constraint_ns = td->effective_constraint_ns;
171 		/*
172 		 * Zero means "no suspend at all" and this runs only when all
173 		 * devices in the domain are suspended, so it must be positive.
174 		 */
175 		if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS)
176 			continue;
177 
178 		if (constraint_ns <= off_on_time_ns)
179 			return false;
180 
181 		if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
182 			min_off_time_ns = constraint_ns;
183 	}
184 
185 	/*
186 	 * If the computed minimum device off time is negative, there are no
187 	 * latency constraints, so the domain can spend arbitrary time in the
188 	 * "off" state.
189 	 */
190 	if (min_off_time_ns < 0)
191 		return true;
192 
193 	/*
194 	 * The difference between the computed minimum subdomain or device off
195 	 * time and the time needed to turn the domain on is the maximum
196 	 * theoretical time this domain can spend in the "off" state.
197 	 */
198 	genpd->max_off_time_ns = min_off_time_ns -
199 		genpd->states[state].power_on_latency_ns;
200 	return true;
201 }
202 
203 /**
204  * default_power_down_ok - Default generic PM domain power off governor routine.
205  * @pd: PM domain to check.
206  *
207  * This routine must be executed under the PM domain's lock.
208  */
209 static bool default_power_down_ok(struct dev_pm_domain *pd)
210 {
211 	struct generic_pm_domain *genpd = pd_to_genpd(pd);
212 	struct gpd_link *link;
213 
214 	if (!genpd->max_off_time_changed) {
215 		genpd->state_idx = genpd->cached_power_down_state_idx;
216 		return genpd->cached_power_down_ok;
217 	}
218 
219 	/*
220 	 * We have to invalidate the cached results for the masters, so
221 	 * use the observation that default_power_down_ok() is not
222 	 * going to be called for any master until this instance
223 	 * returns.
224 	 */
225 	list_for_each_entry(link, &genpd->slave_links, slave_node)
226 		link->master->max_off_time_changed = true;
227 
228 	genpd->max_off_time_ns = -1;
229 	genpd->max_off_time_changed = false;
230 	genpd->cached_power_down_ok = true;
231 	genpd->state_idx = genpd->state_count - 1;
232 
233 	/* Find a state to power down to, starting from the deepest. */
234 	while (!__default_power_down_ok(pd, genpd->state_idx)) {
235 		if (genpd->state_idx == 0) {
236 			genpd->cached_power_down_ok = false;
237 			break;
238 		}
239 		genpd->state_idx--;
240 	}
241 
242 	genpd->cached_power_down_state_idx = genpd->state_idx;
243 	return genpd->cached_power_down_ok;
244 }
245 
246 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
247 {
248 	return false;
249 }
250 
251 #ifdef CONFIG_CPU_IDLE
252 static bool cpu_power_down_ok(struct dev_pm_domain *pd)
253 {
254 	struct generic_pm_domain *genpd = pd_to_genpd(pd);
255 	struct cpuidle_device *dev;
256 	ktime_t domain_wakeup, next_hrtimer;
257 	s64 idle_duration_ns;
258 	int cpu, i;
259 
260 	/* Validate dev PM QoS constraints. */
261 	if (!default_power_down_ok(pd))
262 		return false;
263 
264 	if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN))
265 		return true;
266 
267 	/*
268 	 * Find the next wakeup for any of the online CPUs within the PM domain
269 	 * and its subdomains. Note, we only need the genpd->cpus, as it already
270 	 * contains a mask of all CPUs from subdomains.
271 	 */
272 	domain_wakeup = ktime_set(KTIME_SEC_MAX, 0);
273 	for_each_cpu_and(cpu, genpd->cpus, cpu_online_mask) {
274 		dev = per_cpu(cpuidle_devices, cpu);
275 		if (dev) {
276 			next_hrtimer = READ_ONCE(dev->next_hrtimer);
277 			if (ktime_before(next_hrtimer, domain_wakeup))
278 				domain_wakeup = next_hrtimer;
279 		}
280 	}
281 
282 	/* The minimum idle duration is from now - until the next wakeup. */
283 	idle_duration_ns = ktime_to_ns(ktime_sub(domain_wakeup, ktime_get()));
284 	if (idle_duration_ns <= 0)
285 		return false;
286 
287 	/*
288 	 * Find the deepest idle state that has its residency value satisfied
289 	 * and by also taking into account the power off latency for the state.
290 	 * Start at the state picked by the dev PM QoS constraint validation.
291 	 */
292 	i = genpd->state_idx;
293 	do {
294 		if (idle_duration_ns >= (genpd->states[i].residency_ns +
295 		    genpd->states[i].power_off_latency_ns)) {
296 			genpd->state_idx = i;
297 			return true;
298 		}
299 	} while (--i >= 0);
300 
301 	return false;
302 }
303 
304 struct dev_power_governor pm_domain_cpu_gov = {
305 	.suspend_ok = default_suspend_ok,
306 	.power_down_ok = cpu_power_down_ok,
307 };
308 #endif
309 
310 struct dev_power_governor simple_qos_governor = {
311 	.suspend_ok = default_suspend_ok,
312 	.power_down_ok = default_power_down_ok,
313 };
314 
315 /**
316  * pm_genpd_gov_always_on - A governor implementing an always-on policy
317  */
318 struct dev_power_governor pm_domain_always_on_gov = {
319 	.power_down_ok = always_on_power_down_ok,
320 	.suspend_ok = default_suspend_ok,
321 };
322