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, DEV_PM_QOS_RESUME_LATENCY);
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_resume_latency(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 };