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->suspend_latency_ns +
  81                                 td->resume_latency_ns;
  82                 if (constraint_ns == 0)
  83                         return false;
  84         }
  85         td->effective_constraint_ns = constraint_ns;
  86         td->cached_stop_ok = constraint_ns >= 0;
  87
  88         /*
  89          * The children have been suspended already, so we don't need to take
  90          * their stop latencies into account here.
  91          */
  92         return td->cached_stop_ok;
  93 }
  94
  95 /**
  96  * default_power_down_ok - Default generic PM domain power off governor routine.
  97  * @pd: PM domain to check.
  98  *
  99  * This routine must be executed under the PM domain's lock.
 100  */
 101 static bool default_power_down_ok(struct dev_pm_domain *pd)
 102 {
 103         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 104         struct gpd_link *link;
 105         struct pm_domain_data *pdd;
 106         s64 min_off_time_ns;
 107         s64 off_on_time_ns;
 108
 109         if (genpd->max_off_time_changed) {
 110                 struct gpd_link *link;
 111
 112                 /*
 113                  * We have to invalidate the cached results for the masters, so
 114                  * use the observation that default_power_down_ok() is not
 115                  * going to be called for any master until this instance
 116                  * returns.
 117                  */
 118                 list_for_each_entry(link, &genpd->slave_links, slave_node)
 119                         link->master->max_off_time_changed = true;
 120
 121                 genpd->max_off_time_changed = false;
 122                 genpd->cached_power_down_ok = false;
 123                 genpd->max_off_time_ns = -1;
 124         } else {
 125                 return genpd->cached_power_down_ok;
 126         }
 127
 128         off_on_time_ns = genpd->power_off_latency_ns +
 129                                 genpd->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                 /* default_stop_ok() need not be called before us. */
 171                 if (constraint_ns < 0) {
 172                         constraint_ns = dev_pm_qos_read_value(pdd->dev);
 173                         constraint_ns *= NSEC_PER_USEC;
 174                 }
 175                 if (constraint_ns == 0)
 176                         continue;
 177
 178                 /*
 179                  * constraint_ns cannot be negative here, because the device has
 180                  * been suspended.
 181                  */
 182                 if (constraint_ns <= off_on_time_ns)
 183                         return false;
 184
 185                 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
 186                         min_off_time_ns = constraint_ns;
 187         }
 188
 189         genpd->cached_power_down_ok = true;
 190
 191         /*
 192          * If the computed minimum device off time is negative, there are no
 193          * latency constraints, so the domain can spend arbitrary time in the
 194          * "off" state.
 195          */
 196         if (min_off_time_ns < 0)
 197                 return true;
 198
 199         /*
 200          * The difference between the computed minimum subdomain or device off
 201          * time and the time needed to turn the domain on is the maximum
 202          * theoretical time this domain can spend in the "off" state.
 203          */
 204         genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
 205         return true;
 206 }
 207
 208 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 209 {
 210         return false;
 211 }
 212
 213 struct dev_power_governor simple_qos_governor = {
 214         .stop_ok = default_stop_ok,
 215         .power_down_ok = default_power_down_ok,
 216 };
 217
 218 /**
 219  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 220  */
 221 struct dev_power_governor pm_domain_always_on_gov = {
 222         .power_down_ok = always_on_power_down_ok,
 223         .stop_ok = default_stop_ok,
 224 };