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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
15static 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 struct gpd_timing_data *td = dev_gpd_data(dev)->td;
22
23 /*
24 * Only take suspend-time QoS constraints of devices into
25 * account, because constraints updated after the device has
26 * been suspended are not guaranteed to be taken into account
27 * anyway. In order for them to take effect, the device has to
28 * be resumed and suspended again.
29 */
30 constraint_ns = td ? td->effective_constraint_ns :
31 PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
32 } else {
33 /*
34 * The child is not in a domain and there's no info on its
35 * suspend/resume latencies, so assume them to be negligible and
36 * take its current PM QoS constraint (that's the only thing
37 * known at this point anyway).
38 */
39 constraint_ns = dev_pm_qos_read_value(dev, DEV_PM_QOS_RESUME_LATENCY);
40 constraint_ns *= NSEC_PER_USEC;
41 }
42
43 if (constraint_ns < *constraint_ns_p)
44 *constraint_ns_p = constraint_ns;
45
46 return 0;
47}
48
49/**
50 * default_suspend_ok - Default PM domain governor routine to suspend devices.
51 * @dev: Device to check.
52 */
53static bool default_suspend_ok(struct device *dev)
54{
55 struct gpd_timing_data *td = dev_gpd_data(dev)->td;
56 unsigned long flags;
57 s64 constraint_ns;
58
59 dev_dbg(dev, "%s()\n", __func__);
60
61 spin_lock_irqsave(&dev->power.lock, flags);
62
63 if (!td->constraint_changed) {
64 bool ret = td->cached_suspend_ok;
65
66 spin_unlock_irqrestore(&dev->power.lock, flags);
67 return ret;
68 }
69 td->constraint_changed = false;
70 td->cached_suspend_ok = false;
71 td->effective_constraint_ns = 0;
72 constraint_ns = __dev_pm_qos_resume_latency(dev);
73
74 spin_unlock_irqrestore(&dev->power.lock, flags);
75
76 if (constraint_ns == 0)
77 return false;
78
79 constraint_ns *= NSEC_PER_USEC;
80 /*
81 * We can walk the children without any additional locking, because
82 * they all have been suspended at this point and their
83 * effective_constraint_ns fields won't be modified in parallel with us.
84 */
85 if (!dev->power.ignore_children)
86 device_for_each_child(dev, &constraint_ns,
87 dev_update_qos_constraint);
88
89 if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) {
90 /* "No restriction", so the device is allowed to suspend. */
91 td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
92 td->cached_suspend_ok = true;
93 } else if (constraint_ns == 0) {
94 /*
95 * This triggers if one of the children that don't belong to a
96 * domain has a zero PM QoS constraint and it's better not to
97 * suspend then. effective_constraint_ns is zero already and
98 * cached_suspend_ok is false, so bail out.
99 */
100 return false;
101 } else {
102 constraint_ns -= td->suspend_latency_ns +
103 td->resume_latency_ns;
104 /*
105 * effective_constraint_ns is zero already and cached_suspend_ok
106 * is false, so if the computed value is not positive, return
107 * right away.
108 */
109 if (constraint_ns <= 0)
110 return false;
111
112 td->effective_constraint_ns = constraint_ns;
113 td->cached_suspend_ok = true;
114 }
115
116 /*
117 * The children have been suspended already, so we don't need to take
118 * their suspend latencies into account here.
119 */
120 return td->cached_suspend_ok;
121}
122
123static void update_domain_next_wakeup(struct generic_pm_domain *genpd, ktime_t now)
124{
125 ktime_t domain_wakeup = KTIME_MAX;
126 ktime_t next_wakeup;
127 struct pm_domain_data *pdd;
128 struct gpd_link *link;
129
130 if (!(genpd->flags & GENPD_FLAG_MIN_RESIDENCY))
131 return;
132
133 /*
134 * Devices that have a predictable wakeup pattern, may specify
135 * their next wakeup. Let's find the next wakeup from all the
136 * devices attached to this domain and from all the sub-domains.
137 * It is possible that component's a next wakeup may have become
138 * stale when we read that here. We will ignore to ensure the domain
139 * is able to enter its optimal idle state.
140 */
141 list_for_each_entry(pdd, &genpd->dev_list, list_node) {
142 next_wakeup = to_gpd_data(pdd)->td->next_wakeup;
143 if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
144 if (ktime_before(next_wakeup, domain_wakeup))
145 domain_wakeup = next_wakeup;
146 }
147
148 list_for_each_entry(link, &genpd->parent_links, parent_node) {
149 struct genpd_governor_data *cgd = link->child->gd;
150
151 next_wakeup = cgd ? cgd->next_wakeup : KTIME_MAX;
152 if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
153 if (ktime_before(next_wakeup, domain_wakeup))
154 domain_wakeup = next_wakeup;
155 }
156
157 genpd->gd->next_wakeup = domain_wakeup;
158}
159
160static bool next_wakeup_allows_state(struct generic_pm_domain *genpd,
161 unsigned int state, ktime_t now)
162{
163 ktime_t domain_wakeup = genpd->gd->next_wakeup;
164 s64 idle_time_ns, min_sleep_ns;
165
166 min_sleep_ns = genpd->states[state].power_off_latency_ns +
167 genpd->states[state].residency_ns;
168
169 idle_time_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));
170
171 return idle_time_ns >= min_sleep_ns;
172}
173
174static bool __default_power_down_ok(struct dev_pm_domain *pd,
175 unsigned int state)
176{
177 struct generic_pm_domain *genpd = pd_to_genpd(pd);
178 struct gpd_link *link;
179 struct pm_domain_data *pdd;
180 s64 min_off_time_ns;
181 s64 off_on_time_ns;
182
183 off_on_time_ns = genpd->states[state].power_off_latency_ns +
184 genpd->states[state].power_on_latency_ns;
185
186 min_off_time_ns = -1;
187 /*
188 * Check if subdomains can be off for enough time.
189 *
190 * All subdomains have been powered off already at this point.
191 */
192 list_for_each_entry(link, &genpd->parent_links, parent_node) {
193 struct genpd_governor_data *cgd = link->child->gd;
194
195 s64 sd_max_off_ns = cgd ? cgd->max_off_time_ns : -1;
196
197 if (sd_max_off_ns < 0)
198 continue;
199
200 /*
201 * Check if the subdomain is allowed to be off long enough for
202 * the current domain to turn off and on (that's how much time
203 * it will have to wait worst case).
204 */
205 if (sd_max_off_ns <= off_on_time_ns)
206 return false;
207
208 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
209 min_off_time_ns = sd_max_off_ns;
210 }
211
212 /*
213 * Check if the devices in the domain can be off enough time.
214 */
215 list_for_each_entry(pdd, &genpd->dev_list, list_node) {
216 struct gpd_timing_data *td;
217 s64 constraint_ns;
218
219 /*
220 * Check if the device is allowed to be off long enough for the
221 * domain to turn off and on (that's how much time it will
222 * have to wait worst case).
223 */
224 td = to_gpd_data(pdd)->td;
225 constraint_ns = td->effective_constraint_ns;
226 /*
227 * Zero means "no suspend at all" and this runs only when all
228 * devices in the domain are suspended, so it must be positive.
229 */
230 if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS)
231 continue;
232
233 if (constraint_ns <= off_on_time_ns)
234 return false;
235
236 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
237 min_off_time_ns = constraint_ns;
238 }
239
240 /*
241 * If the computed minimum device off time is negative, there are no
242 * latency constraints, so the domain can spend arbitrary time in the
243 * "off" state.
244 */
245 if (min_off_time_ns < 0)
246 return true;
247
248 /*
249 * The difference between the computed minimum subdomain or device off
250 * time and the time needed to turn the domain on is the maximum
251 * theoretical time this domain can spend in the "off" state.
252 */
253 genpd->gd->max_off_time_ns = min_off_time_ns -
254 genpd->states[state].power_on_latency_ns;
255 return true;
256}
257
258/**
259 * _default_power_down_ok - Default generic PM domain power off governor routine.
260 * @pd: PM domain to check.
261 * @now: current ktime.
262 *
263 * This routine must be executed under the PM domain's lock.
264 */
265static bool _default_power_down_ok(struct dev_pm_domain *pd, ktime_t now)
266{
267 struct generic_pm_domain *genpd = pd_to_genpd(pd);
268 struct genpd_governor_data *gd = genpd->gd;
269 int state_idx = genpd->state_count - 1;
270 struct gpd_link *link;
271
272 /*
273 * Find the next wakeup from devices that can determine their own wakeup
274 * to find when the domain would wakeup and do it for every device down
275 * the hierarchy. It is not worth while to sleep if the state's residency
276 * cannot be met.
277 */
278 update_domain_next_wakeup(genpd, now);
279 if ((genpd->flags & GENPD_FLAG_MIN_RESIDENCY) && (gd->next_wakeup != KTIME_MAX)) {
280 /* Let's find out the deepest domain idle state, the devices prefer */
281 while (state_idx >= 0) {
282 if (next_wakeup_allows_state(genpd, state_idx, now)) {
283 gd->max_off_time_changed = true;
284 break;
285 }
286 state_idx--;
287 }
288
289 if (state_idx < 0) {
290 state_idx = 0;
291 gd->cached_power_down_ok = false;
292 goto done;
293 }
294 }
295
296 if (!gd->max_off_time_changed) {
297 genpd->state_idx = gd->cached_power_down_state_idx;
298 return gd->cached_power_down_ok;
299 }
300
301 /*
302 * We have to invalidate the cached results for the parents, so
303 * use the observation that default_power_down_ok() is not
304 * going to be called for any parent until this instance
305 * returns.
306 */
307 list_for_each_entry(link, &genpd->child_links, child_node) {
308 struct genpd_governor_data *pgd = link->parent->gd;
309
310 if (pgd)
311 pgd->max_off_time_changed = true;
312 }
313
314 gd->max_off_time_ns = -1;
315 gd->max_off_time_changed = false;
316 gd->cached_power_down_ok = true;
317
318 /*
319 * Find a state to power down to, starting from the state
320 * determined by the next wakeup.
321 */
322 while (!__default_power_down_ok(pd, state_idx)) {
323 if (state_idx == 0) {
324 gd->cached_power_down_ok = false;
325 break;
326 }
327 state_idx--;
328 }
329
330done:
331 genpd->state_idx = state_idx;
332 gd->cached_power_down_state_idx = genpd->state_idx;
333 return gd->cached_power_down_ok;
334}
335
336static bool default_power_down_ok(struct dev_pm_domain *pd)
337{
338 return _default_power_down_ok(pd, ktime_get());
339}
340
341#ifdef CONFIG_CPU_IDLE
342static bool cpu_power_down_ok(struct dev_pm_domain *pd)
343{
344 struct generic_pm_domain *genpd = pd_to_genpd(pd);
345 struct cpuidle_device *dev;
346 ktime_t domain_wakeup, next_hrtimer;
347 ktime_t now = ktime_get();
348 s64 idle_duration_ns;
349 int cpu, i;
350
351 /* Validate dev PM QoS constraints. */
352 if (!_default_power_down_ok(pd, now))
353 return false;
354
355 if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN))
356 return true;
357
358 /*
359 * Find the next wakeup for any of the online CPUs within the PM domain
360 * and its subdomains. Note, we only need the genpd->cpus, as it already
361 * contains a mask of all CPUs from subdomains.
362 */
363 domain_wakeup = ktime_set(KTIME_SEC_MAX, 0);
364 for_each_cpu_and(cpu, genpd->cpus, cpu_online_mask) {
365 dev = per_cpu(cpuidle_devices, cpu);
366 if (dev) {
367 next_hrtimer = READ_ONCE(dev->next_hrtimer);
368 if (ktime_before(next_hrtimer, domain_wakeup))
369 domain_wakeup = next_hrtimer;
370 }
371 }
372
373 /* The minimum idle duration is from now - until the next wakeup. */
374 idle_duration_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));
375 if (idle_duration_ns <= 0)
376 return false;
377
378 /* Store the next domain_wakeup to allow consumers to use it. */
379 genpd->gd->next_hrtimer = domain_wakeup;
380
381 /*
382 * Find the deepest idle state that has its residency value satisfied
383 * and by also taking into account the power off latency for the state.
384 * Start at the state picked by the dev PM QoS constraint validation.
385 */
386 i = genpd->state_idx;
387 do {
388 if (idle_duration_ns >= (genpd->states[i].residency_ns +
389 genpd->states[i].power_off_latency_ns)) {
390 genpd->state_idx = i;
391 return true;
392 }
393 } while (--i >= 0);
394
395 return false;
396}
397
398struct dev_power_governor pm_domain_cpu_gov = {
399 .suspend_ok = default_suspend_ok,
400 .power_down_ok = cpu_power_down_ok,
401};
402#endif
403
404struct dev_power_governor simple_qos_governor = {
405 .suspend_ok = default_suspend_ok,
406 .power_down_ok = default_power_down_ok,
407};
408
409/**
410 * pm_genpd_gov_always_on - A governor implementing an always-on policy
411 */
412struct dev_power_governor pm_domain_always_on_gov = {
413 .suspend_ok = default_suspend_ok,
414};