drivers/base/power/domain_governor.c

   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 void update_domain_next_wakeup(struct generic_pm_domain *genpd, ktime_t now)
 121 {
 122         ktime_t domain_wakeup = KTIME_MAX;
 123         ktime_t next_wakeup;
 124         struct pm_domain_data *pdd;
 125         struct gpd_link *link;
 126
 127         if (!(genpd->flags & GENPD_FLAG_MIN_RESIDENCY))
 128                 return;
 129
 130         /*
 131          * Devices that have a predictable wakeup pattern, may specify
 132          * their next wakeup. Let's find the next wakeup from all the
 133          * devices attached to this domain and from all the sub-domains.
 134          * It is possible that component's a next wakeup may have become
 135          * stale when we read that here. We will ignore to ensure the domain
 136          * is able to enter its optimal idle state.
 137          */
 138         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 139                 next_wakeup = to_gpd_data(pdd)->next_wakeup;
 140                 if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
 141                         if (ktime_before(next_wakeup, domain_wakeup))
 142                                 domain_wakeup = next_wakeup;
 143         }
 144
 145         list_for_each_entry(link, &genpd->parent_links, parent_node) {
 146                 next_wakeup = link->child->next_wakeup;
 147                 if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
 148                         if (ktime_before(next_wakeup, domain_wakeup))
 149                                 domain_wakeup = next_wakeup;
 150         }
 151
 152         genpd->next_wakeup = domain_wakeup;
 153 }
 154
 155 static bool next_wakeup_allows_state(struct generic_pm_domain *genpd,
 156                                      unsigned int state, ktime_t now)
 157 {
 158         ktime_t domain_wakeup = genpd->next_wakeup;
 159         s64 idle_time_ns, min_sleep_ns;
 160
 161         min_sleep_ns = genpd->states[state].power_off_latency_ns +
 162                        genpd->states[state].residency_ns;
 163
 164         idle_time_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));
 165
 166         return idle_time_ns >= min_sleep_ns;
 167 }
 168
 169 static bool __default_power_down_ok(struct dev_pm_domain *pd,
 170                                      unsigned int state)
 171 {
 172         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 173         struct gpd_link *link;
 174         struct pm_domain_data *pdd;
 175         s64 min_off_time_ns;
 176         s64 off_on_time_ns;
 177
 178         off_on_time_ns = genpd->states[state].power_off_latency_ns +
 179                 genpd->states[state].power_on_latency_ns;
 180
 181         min_off_time_ns = -1;
 182         /*
 183          * Check if subdomains can be off for enough time.
 184          *
 185          * All subdomains have been powered off already at this point.
 186          */
 187         list_for_each_entry(link, &genpd->parent_links, parent_node) {
 188                 struct generic_pm_domain *sd = link->child;
 189                 s64 sd_max_off_ns = sd->max_off_time_ns;
 190
 191                 if (sd_max_off_ns < 0)
 192                         continue;
 193
 194                 /*
 195                  * Check if the subdomain is allowed to be off long enough for
 196                  * the current domain to turn off and on (that's how much time
 197                  * it will have to wait worst case).
 198                  */
 199                 if (sd_max_off_ns <= off_on_time_ns)
 200                         return false;
 201
 202                 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
 203                         min_off_time_ns = sd_max_off_ns;
 204         }
 205
 206         /*
 207          * Check if the devices in the domain can be off enough time.
 208          */
 209         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 210                 struct gpd_timing_data *td;
 211                 s64 constraint_ns;
 212
 213                 /*
 214                  * Check if the device is allowed to be off long enough for the
 215                  * domain to turn off and on (that's how much time it will
 216                  * have to wait worst case).
 217                  */
 218                 td = &to_gpd_data(pdd)->td;
 219                 constraint_ns = td->effective_constraint_ns;
 220                 /*
 221                  * Zero means "no suspend at all" and this runs only when all
 222                  * devices in the domain are suspended, so it must be positive.
 223                  */
 224                 if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS)
 225                         continue;
 226
 227                 if (constraint_ns <= off_on_time_ns)
 228                         return false;
 229
 230                 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
 231                         min_off_time_ns = constraint_ns;
 232         }
 233
 234         /*
 235          * If the computed minimum device off time is negative, there are no
 236          * latency constraints, so the domain can spend arbitrary time in the
 237          * "off" state.
 238          */
 239         if (min_off_time_ns < 0)
 240                 return true;
 241
 242         /*
 243          * The difference between the computed minimum subdomain or device off
 244          * time and the time needed to turn the domain on is the maximum
 245          * theoretical time this domain can spend in the "off" state.
 246          */
 247         genpd->max_off_time_ns = min_off_time_ns -
 248                 genpd->states[state].power_on_latency_ns;
 249         return true;
 250 }
 251
 252 /**
 253  * _default_power_down_ok - Default generic PM domain power off governor routine.
 254  * @pd: PM domain to check.
 255  * @now: current ktime.
 256  *
 257  * This routine must be executed under the PM domain's lock.
 258  */
 259 static bool _default_power_down_ok(struct dev_pm_domain *pd, ktime_t now)
 260 {
 261         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 262         int state_idx = genpd->state_count - 1;
 263         struct gpd_link *link;
 264
 265         /*
 266          * Find the next wakeup from devices that can determine their own wakeup
 267          * to find when the domain would wakeup and do it for every device down
 268          * the hierarchy. It is not worth while to sleep if the state's residency
 269          * cannot be met.
 270          */
 271         update_domain_next_wakeup(genpd, now);
 272         if ((genpd->flags & GENPD_FLAG_MIN_RESIDENCY) && (genpd->next_wakeup != KTIME_MAX)) {
 273                 /* Let's find out the deepest domain idle state, the devices prefer */
 274                 while (state_idx >= 0) {
 275                         if (next_wakeup_allows_state(genpd, state_idx, now)) {
 276                                 genpd->max_off_time_changed = true;
 277                                 break;
 278                         }
 279                         state_idx--;
 280                 }
 281
 282                 if (state_idx < 0) {
 283                         state_idx = 0;
 284                         genpd->cached_power_down_ok = false;
 285                         goto done;
 286                 }
 287         }
 288
 289         if (!genpd->max_off_time_changed) {
 290                 genpd->state_idx = genpd->cached_power_down_state_idx;
 291                 return genpd->cached_power_down_ok;
 292         }
 293
 294         /*
 295          * We have to invalidate the cached results for the parents, so
 296          * use the observation that default_power_down_ok() is not
 297          * going to be called for any parent until this instance
 298          * returns.
 299          */
 300         list_for_each_entry(link, &genpd->child_links, child_node)
 301                 link->parent->max_off_time_changed = true;
 302
 303         genpd->max_off_time_ns = -1;
 304         genpd->max_off_time_changed = false;
 305         genpd->cached_power_down_ok = true;
 306
 307         /*
 308          * Find a state to power down to, starting from the state
 309          * determined by the next wakeup.
 310          */
 311         while (!__default_power_down_ok(pd, state_idx)) {
 312                 if (state_idx == 0) {
 313                         genpd->cached_power_down_ok = false;
 314                         break;
 315                 }
 316                 state_idx--;
 317         }
 318
 319 done:
 320         genpd->state_idx = state_idx;
 321         genpd->cached_power_down_state_idx = genpd->state_idx;
 322         return genpd->cached_power_down_ok;
 323 }
 324
 325 static bool default_power_down_ok(struct dev_pm_domain *pd)
 326 {
 327         return _default_power_down_ok(pd, ktime_get());
 328 }
 329
 330 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 331 {
 332         return false;
 333 }
 334
 335 #ifdef CONFIG_CPU_IDLE
 336 static bool cpu_power_down_ok(struct dev_pm_domain *pd)
 337 {
 338         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 339         struct cpuidle_device *dev;
 340         ktime_t domain_wakeup, next_hrtimer;
 341         ktime_t now = ktime_get();
 342         s64 idle_duration_ns;
 343         int cpu, i;
 344
 345         /* Validate dev PM QoS constraints. */
 346         if (!_default_power_down_ok(pd, now))
 347                 return false;
 348
 349         if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN))
 350                 return true;
 351
 352         /*
 353          * Find the next wakeup for any of the online CPUs within the PM domain
 354          * and its subdomains. Note, we only need the genpd->cpus, as it already
 355          * contains a mask of all CPUs from subdomains.
 356          */
 357         domain_wakeup = ktime_set(KTIME_SEC_MAX, 0);
 358         for_each_cpu_and(cpu, genpd->cpus, cpu_online_mask) {
 359                 dev = per_cpu(cpuidle_devices, cpu);
 360                 if (dev) {
 361                         next_hrtimer = READ_ONCE(dev->next_hrtimer);
 362                         if (ktime_before(next_hrtimer, domain_wakeup))
 363                                 domain_wakeup = next_hrtimer;
 364                 }
 365         }
 366
 367         /* The minimum idle duration is from now - until the next wakeup. */
 368         idle_duration_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));
 369         if (idle_duration_ns <= 0)
 370                 return false;
 371
 372         /*
 373          * Find the deepest idle state that has its residency value satisfied
 374          * and by also taking into account the power off latency for the state.
 375          * Start at the state picked by the dev PM QoS constraint validation.
 376          */
 377         i = genpd->state_idx;
 378         do {
 379                 if (idle_duration_ns >= (genpd->states[i].residency_ns +
 380                     genpd->states[i].power_off_latency_ns)) {
 381                         genpd->state_idx = i;
 382                         return true;
 383                 }
 384         } while (--i >= 0);
 385
 386         return false;
 387 }
 388
 389 struct dev_power_governor pm_domain_cpu_gov = {
 390         .suspend_ok = default_suspend_ok,
 391         .power_down_ok = cpu_power_down_ok,
 392 };
 393 #endif
 394
 395 struct dev_power_governor simple_qos_governor = {
 396         .suspend_ok = default_suspend_ok,
 397         .power_down_ok = default_power_down_ok,
 398 };
 399
 400 /**
 401  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 402  */
 403 struct dev_power_governor pm_domain_always_on_gov = {
 404         .power_down_ok = always_on_power_down_ok,
 405         .suspend_ok = default_suspend_ok,
 406 };