drivers/base/power/domain_governor.c

   1 /*
   2  * drivers/base/power/domain_governor.c - Governors for device PM domains.
   3  *
   4  * Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
   5  *
   6  * This file is released under the GPLv2.
   7  */
   8
   9 #include <linux/kernel.h>
  10 #include <linux/pm_domain.h>
  11 #include <linux/pm_qos.h>
  12 #include <linux/hrtimer.h>
  13
  14 static int dev_update_qos_constraint(struct device *dev, void *data)
  15 {
  16         s64 *constraint_ns_p = data;
  17         s64 constraint_ns;
  18
  19         if (dev->power.subsys_data && dev->power.subsys_data->domain_data) {
  20                 /*
  21                  * Only take suspend-time QoS constraints of devices into
  22                  * account, because constraints updated after the device has
  23                  * been suspended are not guaranteed to be taken into account
  24                  * anyway.  In order for them to take effect, the device has to
  25                  * be resumed and suspended again.
  26                  */
  27                 constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
  28         } else {
  29                 /*
  30                  * The child is not in a domain and there's no info on its
  31                  * suspend/resume latencies, so assume them to be negligible and
  32                  * take its current PM QoS constraint (that's the only thing
  33                  * known at this point anyway).
  34                  */
  35                 constraint_ns = dev_pm_qos_read_value(dev);
  36                 constraint_ns *= NSEC_PER_USEC;
  37         }
  38
  39         if (constraint_ns < *constraint_ns_p)
  40                 *constraint_ns_p = constraint_ns;
  41
  42         return 0;
  43 }
  44
  45 /**
  46  * default_suspend_ok - Default PM domain governor routine to suspend devices.
  47  * @dev: Device to check.
  48  */
  49 static bool default_suspend_ok(struct device *dev)
  50 {
  51         struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
  52         unsigned long flags;
  53         s64 constraint_ns;
  54
  55         dev_dbg(dev, "%s()\n", __func__);
  56
  57         spin_lock_irqsave(&dev->power.lock, flags);
  58
  59         if (!td->constraint_changed) {
  60                 bool ret = td->cached_suspend_ok;
  61
  62                 spin_unlock_irqrestore(&dev->power.lock, flags);
  63                 return ret;
  64         }
  65         td->constraint_changed = false;
  66         td->cached_suspend_ok = false;
  67         td->effective_constraint_ns = 0;
  68         constraint_ns = __dev_pm_qos_read_value(dev);
  69
  70         spin_unlock_irqrestore(&dev->power.lock, flags);
  71
  72         if (constraint_ns == 0)
  73                 return false;
  74
  75         constraint_ns *= NSEC_PER_USEC;
  76         /*
  77          * We can walk the children without any additional locking, because
  78          * they all have been suspended at this point and their
  79          * effective_constraint_ns fields won't be modified in parallel with us.
  80          */
  81         if (!dev->power.ignore_children)
  82                 device_for_each_child(dev, &constraint_ns,
  83                                       dev_update_qos_constraint);
  84
  85         if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) {
  86                 /* "No restriction", so the device is allowed to suspend. */
  87                 td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
  88                 td->cached_suspend_ok = true;
  89         } else if (constraint_ns == 0) {
  90                 /*
  91                  * This triggers if one of the children that don't belong to a
  92                  * domain has a zero PM QoS constraint and it's better not to
  93                  * suspend then.  effective_constraint_ns is zero already and
  94                  * cached_suspend_ok is false, so bail out.
  95                  */
  96                 return false;
  97         } else {
  98                 constraint_ns -= td->suspend_latency_ns +
  99                                 td->resume_latency_ns;
 100                 /*
 101                  * effective_constraint_ns is zero already and cached_suspend_ok
 102                  * is false, so if the computed value is not positive, return
 103                  * right away.
 104                  */
 105                 if (constraint_ns <= 0)
 106                         return false;
 107
 108                 td->effective_constraint_ns = constraint_ns;
 109                 td->cached_suspend_ok = true;
 110         }
 111
 112         /*
 113          * The children have been suspended already, so we don't need to take
 114          * their suspend latencies into account here.
 115          */
 116         return td->cached_suspend_ok;
 117 }
 118
 119 static bool __default_power_down_ok(struct dev_pm_domain *pd,
 120                                      unsigned int state)
 121 {
 122         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 123         struct gpd_link *link;
 124         struct pm_domain_data *pdd;
 125         s64 min_off_time_ns;
 126         s64 off_on_time_ns;
 127
 128         off_on_time_ns = genpd->states[state].power_off_latency_ns +
 129                 genpd->states[state].power_on_latency_ns;
 130
 131         min_off_time_ns = -1;
 132         /*
 133          * Check if subdomains can be off for enough time.
 134          *
 135          * All subdomains have been powered off already at this point.
 136          */
 137         list_for_each_entry(link, &genpd->master_links, master_node) {
 138                 struct generic_pm_domain *sd = link->slave;
 139                 s64 sd_max_off_ns = sd->max_off_time_ns;
 140
 141                 if (sd_max_off_ns < 0)
 142                         continue;
 143
 144                 /*
 145                  * Check if the subdomain is allowed to be off long enough for
 146                  * the current domain to turn off and on (that's how much time
 147                  * it will have to wait worst case).
 148                  */
 149                 if (sd_max_off_ns <= off_on_time_ns)
 150                         return false;
 151
 152                 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
 153                         min_off_time_ns = sd_max_off_ns;
 154         }
 155
 156         /*
 157          * Check if the devices in the domain can be off enough time.
 158          */
 159         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 160                 struct gpd_timing_data *td;
 161                 s64 constraint_ns;
 162
 163                 /*
 164                  * Check if the device is allowed to be off long enough for the
 165                  * domain to turn off and on (that's how much time it will
 166                  * have to wait worst case).
 167                  */
 168                 td = &to_gpd_data(pdd)->td;
 169                 constraint_ns = td->effective_constraint_ns;
 170                 /*
 171                  * Zero means "no suspend at all" and this runs only when all
 172                  * devices in the domain are suspended, so it must be positive.
 173                  */
 174                 if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS)
 175                         continue;
 176
 177                 if (constraint_ns <= off_on_time_ns)
 178                         return false;
 179
 180                 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
 181                         min_off_time_ns = constraint_ns;
 182         }
 183
 184         /*
 185          * If the computed minimum device off time is negative, there are no
 186          * latency constraints, so the domain can spend arbitrary time in the
 187          * "off" state.
 188          */
 189         if (min_off_time_ns < 0)
 190                 return true;
 191
 192         /*
 193          * The difference between the computed minimum subdomain or device off
 194          * time and the time needed to turn the domain on is the maximum
 195          * theoretical time this domain can spend in the "off" state.
 196          */
 197         genpd->max_off_time_ns = min_off_time_ns -
 198                 genpd->states[state].power_on_latency_ns;
 199         return true;
 200 }
 201
 202 /**
 203  * default_power_down_ok - Default generic PM domain power off governor routine.
 204  * @pd: PM domain to check.
 205  *
 206  * This routine must be executed under the PM domain's lock.
 207  */
 208 static bool default_power_down_ok(struct dev_pm_domain *pd)
 209 {
 210         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 211         struct gpd_link *link;
 212
 213         if (!genpd->max_off_time_changed)
 214                 return genpd->cached_power_down_ok;
 215
 216         /*
 217          * We have to invalidate the cached results for the masters, so
 218          * use the observation that default_power_down_ok() is not
 219          * going to be called for any master until this instance
 220          * returns.
 221          */
 222         list_for_each_entry(link, &genpd->slave_links, slave_node)
 223                 link->master->max_off_time_changed = true;
 224
 225         genpd->max_off_time_ns = -1;
 226         genpd->max_off_time_changed = false;
 227         genpd->cached_power_down_ok = true;
 228         genpd->state_idx = genpd->state_count - 1;
 229
 230         /* Find a state to power down to, starting from the deepest. */
 231         while (!__default_power_down_ok(pd, genpd->state_idx)) {
 232                 if (genpd->state_idx == 0) {
 233                         genpd->cached_power_down_ok = false;
 234                         break;
 235                 }
 236                 genpd->state_idx--;
 237         }
 238
 239         return genpd->cached_power_down_ok;
 240 }
 241
 242 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 243 {
 244         return false;
 245 }
 246
 247 struct dev_power_governor simple_qos_governor = {
 248         .suspend_ok = default_suspend_ok,
 249         .power_down_ok = default_power_down_ok,
 250 };
 251
 252 /**
 253  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 254  */
 255 struct dev_power_governor pm_domain_always_on_gov = {
 256         .power_down_ok = always_on_power_down_ok,
 257         .suspend_ok = default_suspend_ok,
 258 };