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 | 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, type: 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 | */ |
53 | static 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(lock: &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(lock: &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, data: &constraint_ns, |
87 | fn: 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 | |
123 | static 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(cmp1: next_wakeup, cmp2: now)) |
144 | if (ktime_before(cmp1: next_wakeup, cmp2: 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(cmp1: next_wakeup, cmp2: now)) |
153 | if (ktime_before(cmp1: next_wakeup, cmp2: domain_wakeup)) |
154 | domain_wakeup = next_wakeup; |
155 | } |
156 | |
157 | genpd->gd->next_wakeup = domain_wakeup; |
158 | } |
159 | |
160 | static 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 | |
174 | static 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 | */ |
265 | static 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: 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: state_idx)) { |
323 | if (state_idx == 0) { |
324 | gd->cached_power_down_ok = false; |
325 | break; |
326 | } |
327 | state_idx--; |
328 | } |
329 | |
330 | done: |
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 | |
336 | static bool default_power_down_ok(struct dev_pm_domain *pd) |
337 | { |
338 | return _default_power_down_ok(pd, now: ktime_get()); |
339 | } |
340 | |
341 | #ifdef CONFIG_CPU_IDLE |
342 | static 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, nsecs: 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(cmp1: next_hrtimer, cmp2: 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 | |
398 | struct 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 | |
404 | struct 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 | */ |
412 | struct dev_power_governor pm_domain_always_on_gov = { |
413 | .suspend_ok = default_suspend_ok, |
414 | }; |
415 | |