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/init.h>
  10 #include <linux/kernel.h>
  11 #include <linux/pm_domain.h>
  12 #include <linux/pm_qos.h>
  13 #include <linux/hrtimer.h>
  14
  15 #ifdef CONFIG_PM_RUNTIME
  16
  17 static int dev_update_qos_constraint(struct device *dev, void *data)
  18 {
  19         s64 *constraint_ns_p = data;
  20         s32 constraint_ns = -1;
  21
  22         if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
  23                 constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
  24
  25         if (constraint_ns < 0) {
  26                 constraint_ns = dev_pm_qos_read_value(dev);
  27                 constraint_ns *= NSEC_PER_USEC;
  28         }
  29         if (constraint_ns == 0)
  30                 return 0;
  31
  32         /*
  33          * constraint_ns cannot be negative here, because the device has been
  34          * suspended.
  35          */
  36         if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
  37                 *constraint_ns_p = constraint_ns;
  38
  39         return 0;
  40 }
  41
  42 /**
  43  * default_stop_ok - Default PM domain governor routine for stopping devices.
  44  * @dev: Device to check.
  45  */
  46 bool default_stop_ok(struct device *dev)
  47 {
  48         struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
  49         unsigned long flags;
  50         s64 constraint_ns;
  51
  52         dev_dbg(dev, "%s()\n", __func__);
  53
  54         spin_lock_irqsave(&dev->power.lock, flags);
  55
  56         if (!td->constraint_changed) {
  57                 bool ret = td->cached_stop_ok;
  58
  59                 spin_unlock_irqrestore(&dev->power.lock, flags);
  60                 return ret;
  61         }
  62         td->constraint_changed = false;
  63         td->cached_stop_ok = false;
  64         td->effective_constraint_ns = -1;
  65         constraint_ns = __dev_pm_qos_read_value(dev);
  66
  67         spin_unlock_irqrestore(&dev->power.lock, flags);
  68
  69         if (constraint_ns < 0)
  70                 return false;
  71
  72         constraint_ns *= NSEC_PER_USEC;
  73         /*
  74          * We can walk the children without any additional locking, because
  75          * they all have been suspended at this point and their
  76          * effective_constraint_ns fields won't be modified in parallel with us.
  77          */
  78         if (!dev->power.ignore_children)
  79                 device_for_each_child(dev, &constraint_ns,
  80                                       dev_update_qos_constraint);
  81
  82         if (constraint_ns > 0) {
  83                 constraint_ns -= td->start_latency_ns;
  84                 if (constraint_ns == 0)
  85                         return false;
  86         }
  87         td->effective_constraint_ns = constraint_ns;
  88         td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
  89                                 constraint_ns == 0;
  90         /*
  91          * The children have been suspended already, so we don't need to take
  92          * their stop latencies into account here.
  93          */
  94         return td->cached_stop_ok;
  95 }
  96
  97 /**
  98  * default_power_down_ok - Default generic PM domain power off governor routine.
  99  * @pd: PM domain to check.
 100  *
 101  * This routine must be executed under the PM domain's lock.
 102  */
 103 static bool default_power_down_ok(struct dev_pm_domain *pd)
 104 {
 105         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 106         struct gpd_link *link;
 107         struct pm_domain_data *pdd;
 108         s64 min_off_time_ns;
 109         s64 off_on_time_ns;
 110
 111         if (genpd->max_off_time_changed) {
 112                 struct gpd_link *link;
 113
 114                 /*
 115                  * We have to invalidate the cached results for the masters, so
 116                  * use the observation that default_power_down_ok() is not
 117                  * going to be called for any master until this instance
 118                  * returns.
 119                  */
 120                 list_for_each_entry(link, &genpd->slave_links, slave_node)
 121                         link->master->max_off_time_changed = true;
 122
 123                 genpd->max_off_time_changed = false;
 124                 genpd->cached_power_down_ok = false;
 125                 genpd->max_off_time_ns = -1;
 126         } else {
 127                 return genpd->cached_power_down_ok;
 128         }
 129
 130         off_on_time_ns = genpd->power_off_latency_ns +
 131                                 genpd->power_on_latency_ns;
 132         /*
 133          * It doesn't make sense to remove power from the domain if saving
 134          * the state of all devices in it and the power off/power on operations
 135          * take too much time.
 136          *
 137          * All devices in this domain have been stopped already at this point.
 138          */
 139         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 140                 if (pdd->dev->driver)
 141                         off_on_time_ns +=
 142                                 to_gpd_data(pdd)->td.save_state_latency_ns;
 143         }
 144
 145         min_off_time_ns = -1;
 146         /*
 147          * Check if subdomains can be off for enough time.
 148          *
 149          * All subdomains have been powered off already at this point.
 150          */
 151         list_for_each_entry(link, &genpd->master_links, master_node) {
 152                 struct generic_pm_domain *sd = link->slave;
 153                 s64 sd_max_off_ns = sd->max_off_time_ns;
 154
 155                 if (sd_max_off_ns < 0)
 156                         continue;
 157
 158                 /*
 159                  * Check if the subdomain is allowed to be off long enough for
 160                  * the current domain to turn off and on (that's how much time
 161                  * it will have to wait worst case).
 162                  */
 163                 if (sd_max_off_ns <= off_on_time_ns)
 164                         return false;
 165
 166                 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
 167                         min_off_time_ns = sd_max_off_ns;
 168         }
 169
 170         /*
 171          * Check if the devices in the domain can be off enough time.
 172          */
 173         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 174                 struct gpd_timing_data *td;
 175                 s64 constraint_ns;
 176
 177                 if (!pdd->dev->driver)
 178                         continue;
 179
 180                 /*
 181                  * Check if the device is allowed to be off long enough for the
 182                  * domain to turn off and on (that's how much time it will
 183                  * have to wait worst case).
 184                  */
 185                 td = &to_gpd_data(pdd)->td;
 186                 constraint_ns = td->effective_constraint_ns;
 187                 /* default_stop_ok() need not be called before us. */
 188                 if (constraint_ns < 0) {
 189                         constraint_ns = dev_pm_qos_read_value(pdd->dev);
 190                         constraint_ns *= NSEC_PER_USEC;
 191                 }
 192                 if (constraint_ns == 0)
 193                         continue;
 194
 195                 /*
 196                  * constraint_ns cannot be negative here, because the device has
 197                  * been suspended.
 198                  */
 199                 constraint_ns -= td->restore_state_latency_ns;
 200                 if (constraint_ns <= off_on_time_ns)
 201                         return false;
 202
 203                 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
 204                         min_off_time_ns = constraint_ns;
 205         }
 206
 207         genpd->cached_power_down_ok = true;
 208
 209         /*
 210          * If the computed minimum device off time is negative, there are no
 211          * latency constraints, so the domain can spend arbitrary time in the
 212          * "off" state.
 213          */
 214         if (min_off_time_ns < 0)
 215                 return true;
 216
 217         /*
 218          * The difference between the computed minimum subdomain or device off
 219          * time and the time needed to turn the domain on is the maximum
 220          * theoretical time this domain can spend in the "off" state.
 221          */
 222         genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
 223         return true;
 224 }
 225
 226 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 227 {
 228         return false;
 229 }
 230
 231 #else /* !CONFIG_PM_RUNTIME */
 232
 233 bool default_stop_ok(struct device *dev)
 234 {
 235         return false;
 236 }
 237
 238 #define default_power_down_ok   NULL
 239 #define always_on_power_down_ok NULL
 240
 241 #endif /* !CONFIG_PM_RUNTIME */
 242
 243 struct dev_power_governor simple_qos_governor = {
 244         .stop_ok = default_stop_ok,
 245         .power_down_ok = default_power_down_ok,
 246 };
 247
 248 /**
 249  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 250  */
 251 struct dev_power_governor pm_domain_always_on_gov = {
 252         .power_down_ok = always_on_power_down_ok,
 253         .stop_ok = default_stop_ok,
 254 };