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 #ifdef CONFIG_PM_RUNTIME
  15
  16 static int dev_update_qos_constraint(struct device *dev, void *data)
  17 {
  18         s64 *constraint_ns_p = data;
  19         s32 constraint_ns = -1;
  20
  21         if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
  22                 constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
  23
  24         if (constraint_ns < 0) {
  25                 constraint_ns = dev_pm_qos_read_value(dev);
  26                 constraint_ns *= NSEC_PER_USEC;
  27         }
  28         if (constraint_ns == 0)
  29                 return 0;
  30
  31         /*
  32          * constraint_ns cannot be negative here, because the device has been
  33          * suspended.
  34          */
  35         if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
  36                 *constraint_ns_p = constraint_ns;
  37
  38         return 0;
  39 }
  40
  41 /**
  42  * default_stop_ok - Default PM domain governor routine for stopping devices.
  43  * @dev: Device to check.
  44  */
  45 bool default_stop_ok(struct device *dev)
  46 {
  47         struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
  48         unsigned long flags;
  49         s64 constraint_ns;
  50
  51         dev_dbg(dev, "%s()\n", __func__);
  52
  53         spin_lock_irqsave(&dev->power.lock, flags);
  54
  55         if (!td->constraint_changed) {
  56                 bool ret = td->cached_stop_ok;
  57
  58                 spin_unlock_irqrestore(&dev->power.lock, flags);
  59                 return ret;
  60         }
  61         td->constraint_changed = false;
  62         td->cached_stop_ok = false;
  63         td->effective_constraint_ns = -1;
  64         constraint_ns = __dev_pm_qos_read_value(dev);
  65
  66         spin_unlock_irqrestore(&dev->power.lock, flags);
  67
  68         if (constraint_ns < 0)
  69                 return false;
  70
  71         constraint_ns *= NSEC_PER_USEC;
  72         /*
  73          * We can walk the children without any additional locking, because
  74          * they all have been suspended at this point and their
  75          * effective_constraint_ns fields won't be modified in parallel with us.
  76          */
  77         if (!dev->power.ignore_children)
  78                 device_for_each_child(dev, &constraint_ns,
  79                                       dev_update_qos_constraint);
  80
  81         if (constraint_ns > 0) {
  82                 constraint_ns -= td->start_latency_ns;
  83                 if (constraint_ns == 0)
  84                         return false;
  85         }
  86         td->effective_constraint_ns = constraint_ns;
  87         td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
  88                                 constraint_ns == 0;
  89         /*
  90          * The children have been suspended already, so we don't need to take
  91          * their stop latencies into account here.
  92          */
  93         return td->cached_stop_ok;
  94 }
  95
  96 /**
  97  * default_power_down_ok - Default generic PM domain power off governor routine.
  98  * @pd: PM domain to check.
  99  *
 100  * This routine must be executed under the PM domain's lock.
 101  */
 102 static bool default_power_down_ok(struct dev_pm_domain *pd)
 103 {
 104         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 105         struct gpd_link *link;
 106         struct pm_domain_data *pdd;
 107         s64 min_off_time_ns;
 108         s64 off_on_time_ns;
 109
 110         if (genpd->max_off_time_changed) {
 111                 struct gpd_link *link;
 112
 113                 /*
 114                  * We have to invalidate the cached results for the masters, so
 115                  * use the observation that default_power_down_ok() is not
 116                  * going to be called for any master until this instance
 117                  * returns.
 118                  */
 119                 list_for_each_entry(link, &genpd->slave_links, slave_node)
 120                         link->master->max_off_time_changed = true;
 121
 122                 genpd->max_off_time_changed = false;
 123                 genpd->cached_power_down_ok = false;
 124                 genpd->max_off_time_ns = -1;
 125         } else {
 126                 return genpd->cached_power_down_ok;
 127         }
 128
 129         off_on_time_ns = genpd->power_off_latency_ns +
 130                                 genpd->power_on_latency_ns;
 131         /*
 132          * It doesn't make sense to remove power from the domain if saving
 133          * the state of all devices in it and the power off/power on operations
 134          * take too much time.
 135          *
 136          * All devices in this domain have been stopped already at this point.
 137          */
 138         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 139                 if (pdd->dev->driver)
 140                         off_on_time_ns +=
 141                                 to_gpd_data(pdd)->td.save_state_latency_ns;
 142         }
 143
 144         min_off_time_ns = -1;
 145         /*
 146          * Check if subdomains can be off for enough time.
 147          *
 148          * All subdomains have been powered off already at this point.
 149          */
 150         list_for_each_entry(link, &genpd->master_links, master_node) {
 151                 struct generic_pm_domain *sd = link->slave;
 152                 s64 sd_max_off_ns = sd->max_off_time_ns;
 153
 154                 if (sd_max_off_ns < 0)
 155                         continue;
 156
 157                 /*
 158                  * Check if the subdomain is allowed to be off long enough for
 159                  * the current domain to turn off and on (that's how much time
 160                  * it will have to wait worst case).
 161                  */
 162                 if (sd_max_off_ns <= off_on_time_ns)
 163                         return false;
 164
 165                 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
 166                         min_off_time_ns = sd_max_off_ns;
 167         }
 168
 169         /*
 170          * Check if the devices in the domain can be off enough time.
 171          */
 172         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 173                 struct gpd_timing_data *td;
 174                 s64 constraint_ns;
 175
 176                 if (!pdd->dev->driver)
 177                         continue;
 178
 179                 /*
 180                  * Check if the device is allowed to be off long enough for the
 181                  * domain to turn off and on (that's how much time it will
 182                  * have to wait worst case).
 183                  */
 184                 td = &to_gpd_data(pdd)->td;
 185                 constraint_ns = td->effective_constraint_ns;
 186                 /* default_stop_ok() need not be called before us. */
 187                 if (constraint_ns < 0) {
 188                         constraint_ns = dev_pm_qos_read_value(pdd->dev);
 189                         constraint_ns *= NSEC_PER_USEC;
 190                 }
 191                 if (constraint_ns == 0)
 192                         continue;
 193
 194                 /*
 195                  * constraint_ns cannot be negative here, because the device has
 196                  * been suspended.
 197                  */
 198                 constraint_ns -= td->restore_state_latency_ns;
 199                 if (constraint_ns <= off_on_time_ns)
 200                         return false;
 201
 202                 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
 203                         min_off_time_ns = constraint_ns;
 204         }
 205
 206         genpd->cached_power_down_ok = true;
 207
 208         /*
 209          * If the computed minimum device off time is negative, there are no
 210          * latency constraints, so the domain can spend arbitrary time in the
 211          * "off" state.
 212          */
 213         if (min_off_time_ns < 0)
 214                 return true;
 215
 216         /*
 217          * The difference between the computed minimum subdomain or device off
 218          * time and the time needed to turn the domain on is the maximum
 219          * theoretical time this domain can spend in the "off" state.
 220          */
 221         genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
 222         return true;
 223 }
 224
 225 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 226 {
 227         return false;
 228 }
 229
 230 #else /* !CONFIG_PM_RUNTIME */
 231
 232 bool default_stop_ok(struct device *dev)
 233 {
 234         return false;
 235 }
 236
 237 #define default_power_down_ok   NULL
 238 #define always_on_power_down_ok NULL
 239
 240 #endif /* !CONFIG_PM_RUNTIME */
 241
 242 struct dev_power_governor simple_qos_governor = {
 243         .stop_ok = default_stop_ok,
 244         .power_down_ok = default_power_down_ok,
 245 };
 246
 247 /**
 248  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 249  */
 250 struct dev_power_governor pm_domain_always_on_gov = {
 251         .power_down_ok = always_on_power_down_ok,
 252         .stop_ok = default_stop_ok,
 253 };