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         s32 constraint_ns = -1;
  18
  19         if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
  20                 constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
  21
  22         if (constraint_ns < 0) {
  23                 constraint_ns = dev_pm_qos_read_value(dev);
  24                 constraint_ns *= NSEC_PER_USEC;
  25         }
  26         if (constraint_ns == 0)
  27                 return 0;
  28
  29         /*
  30          * constraint_ns cannot be negative here, because the device has been
  31          * suspended.
  32          */
  33         if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
  34                 *constraint_ns_p = constraint_ns;
  35
  36         return 0;
  37 }
  38
  39 /**
  40  * default_stop_ok - Default PM domain governor routine for stopping devices.
  41  * @dev: Device to check.
  42  */
  43 static bool default_stop_ok(struct device *dev)
  44 {
  45         struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
  46         unsigned long flags;
  47         s64 constraint_ns;
  48
  49         dev_dbg(dev, "%s()\n", __func__);
  50
  51         spin_lock_irqsave(&dev->power.lock, flags);
  52
  53         if (!td->constraint_changed) {
  54                 bool ret = td->cached_stop_ok;
  55
  56                 spin_unlock_irqrestore(&dev->power.lock, flags);
  57                 return ret;
  58         }
  59         td->constraint_changed = false;
  60         td->cached_stop_ok = false;
  61         td->effective_constraint_ns = -1;
  62         constraint_ns = __dev_pm_qos_read_value(dev);
  63
  64         spin_unlock_irqrestore(&dev->power.lock, flags);
  65
  66         if (constraint_ns < 0)
  67                 return false;
  68
  69         constraint_ns *= NSEC_PER_USEC;
  70         /*
  71          * We can walk the children without any additional locking, because
  72          * they all have been suspended at this point and their
  73          * effective_constraint_ns fields won't be modified in parallel with us.
  74          */
  75         if (!dev->power.ignore_children)
  76                 device_for_each_child(dev, &constraint_ns,
  77                                       dev_update_qos_constraint);
  78
  79         if (constraint_ns > 0) {
  80                 constraint_ns -= td->start_latency_ns;
  81                 if (constraint_ns == 0)
  82                         return false;
  83         }
  84         td->effective_constraint_ns = constraint_ns;
  85         td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
  86                                 constraint_ns == 0;
  87         /*
  88          * The children have been suspended already, so we don't need to take
  89          * their stop latencies into account here.
  90          */
  91         return td->cached_stop_ok;
  92 }
  93
  94 /**
  95  * default_power_down_ok - Default generic PM domain power off governor routine.
  96  * @pd: PM domain to check.
  97  *
  98  * This routine must be executed under the PM domain's lock.
  99  */
 100 static bool default_power_down_ok(struct dev_pm_domain *pd)
 101 {
 102         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 103         struct gpd_link *link;
 104         struct pm_domain_data *pdd;
 105         s64 min_off_time_ns;
 106         s64 off_on_time_ns;
 107
 108         if (genpd->max_off_time_changed) {
 109                 struct gpd_link *link;
 110
 111                 /*
 112                  * We have to invalidate the cached results for the masters, so
 113                  * use the observation that default_power_down_ok() is not
 114                  * going to be called for any master until this instance
 115                  * returns.
 116                  */
 117                 list_for_each_entry(link, &genpd->slave_links, slave_node)
 118                         link->master->max_off_time_changed = true;
 119
 120                 genpd->max_off_time_changed = false;
 121                 genpd->cached_power_down_ok = false;
 122                 genpd->max_off_time_ns = -1;
 123         } else {
 124                 return genpd->cached_power_down_ok;
 125         }
 126
 127         off_on_time_ns = genpd->power_off_latency_ns +
 128                                 genpd->power_on_latency_ns;
 129         /*
 130          * It doesn't make sense to remove power from the domain if saving
 131          * the state of all devices in it and the power off/power on operations
 132          * take too much time.
 133          *
 134          * All devices in this domain have been stopped already at this point.
 135          */
 136         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 137                 if (pdd->dev->driver)
 138                         off_on_time_ns +=
 139                                 to_gpd_data(pdd)->td.save_state_latency_ns;
 140         }
 141
 142         min_off_time_ns = -1;
 143         /*
 144          * Check if subdomains can be off for enough time.
 145          *
 146          * All subdomains have been powered off already at this point.
 147          */
 148         list_for_each_entry(link, &genpd->master_links, master_node) {
 149                 struct generic_pm_domain *sd = link->slave;
 150                 s64 sd_max_off_ns = sd->max_off_time_ns;
 151
 152                 if (sd_max_off_ns < 0)
 153                         continue;
 154
 155                 /*
 156                  * Check if the subdomain is allowed to be off long enough for
 157                  * the current domain to turn off and on (that's how much time
 158                  * it will have to wait worst case).
 159                  */
 160                 if (sd_max_off_ns <= off_on_time_ns)
 161                         return false;
 162
 163                 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
 164                         min_off_time_ns = sd_max_off_ns;
 165         }
 166
 167         /*
 168          * Check if the devices in the domain can be off enough time.
 169          */
 170         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 171                 struct gpd_timing_data *td;
 172                 s64 constraint_ns;
 173
 174                 if (!pdd->dev->driver)
 175                         continue;
 176
 177                 /*
 178                  * Check if the device is allowed to be off long enough for the
 179                  * domain to turn off and on (that's how much time it will
 180                  * have to wait worst case).
 181                  */
 182                 td = &to_gpd_data(pdd)->td;
 183                 constraint_ns = td->effective_constraint_ns;
 184                 /* default_stop_ok() need not be called before us. */
 185                 if (constraint_ns < 0) {
 186                         constraint_ns = dev_pm_qos_read_value(pdd->dev);
 187                         constraint_ns *= NSEC_PER_USEC;
 188                 }
 189                 if (constraint_ns == 0)
 190                         continue;
 191
 192                 /*
 193                  * constraint_ns cannot be negative here, because the device has
 194                  * been suspended.
 195                  */
 196                 constraint_ns -= td->restore_state_latency_ns;
 197                 if (constraint_ns <= off_on_time_ns)
 198                         return false;
 199
 200                 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
 201                         min_off_time_ns = constraint_ns;
 202         }
 203
 204         genpd->cached_power_down_ok = true;
 205
 206         /*
 207          * If the computed minimum device off time is negative, there are no
 208          * latency constraints, so the domain can spend arbitrary time in the
 209          * "off" state.
 210          */
 211         if (min_off_time_ns < 0)
 212                 return true;
 213
 214         /*
 215          * The difference between the computed minimum subdomain or device off
 216          * time and the time needed to turn the domain on is the maximum
 217          * theoretical time this domain can spend in the "off" state.
 218          */
 219         genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
 220         return true;
 221 }
 222
 223 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 224 {
 225         return false;
 226 }
 227
 228 struct dev_power_governor simple_qos_governor = {
 229         .stop_ok = default_stop_ok,
 230         .power_down_ok = default_power_down_ok,
 231 };
 232
 233 /**
 234  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 235  */
 236 struct dev_power_governor pm_domain_always_on_gov = {
 237         .power_down_ok = always_on_power_down_ok,
 238         .stop_ok = default_stop_ok,
 239 };