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
 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                 return genpd->cached_power_down_ok;
 216
 217         /*
 218          * We have to invalidate the cached results for the masters, so
 219          * use the observation that default_power_down_ok() is not
 220          * going to be called for any master until this instance
 221          * returns.
 222          */
 223         list_for_each_entry(link, &genpd->slave_links, slave_node)
 224                 link->master->max_off_time_changed = true;
 225
 226         genpd->max_off_time_ns = -1;
 227         genpd->max_off_time_changed = false;
 228         genpd->cached_power_down_ok = true;
 229         genpd->state_idx = genpd->state_count - 1;
 230
 231         /* Find a state to power down to, starting from the deepest. */
 232         while (!__default_power_down_ok(pd, genpd->state_idx)) {
 233                 if (genpd->state_idx == 0) {
 234                         genpd->cached_power_down_ok = false;
 235                         break;
 236                 }
 237                 genpd->state_idx--;
 238         }
 239
 240         return genpd->cached_power_down_ok;
 241 }
 242
 243 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 244 {
 245         return false;
 246 }
 247
 248 struct dev_power_governor simple_qos_governor = {
 249         .suspend_ok = default_suspend_ok,
 250         .power_down_ok = default_power_down_ok,
 251 };
 252
 253 /**
 254  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 255  */
 256 struct dev_power_governor pm_domain_always_on_gov = {
 257         .power_down_ok = always_on_power_down_ok,
 258         .suspend_ok = default_suspend_ok,
 259 };