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_suspend_ok - Default PM domain governor routine to suspend devices.
  41  * @dev: Device to check.
  42  */
  43 static bool default_suspend_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_suspend_ok;
  55
  56                 spin_unlock_irqrestore(&dev->power.lock, flags);
  57                 return ret;
  58         }
  59         td->constraint_changed = false;
  60         td->cached_suspend_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_suspend_ok = constraint_ns >= 0;
  87
  88         /*
  89          * The children have been suspended already, so we don't need to take
  90          * their suspend latencies into account here.
  91          */
  92         return td->cached_suspend_ok;
  93 }
  94
  95 static bool __default_power_down_ok(struct dev_pm_domain *pd,
  96                                      unsigned int state)
  97 {
  98         struct generic_pm_domain *genpd = pd_to_genpd(pd);
  99         struct gpd_link *link;
 100         struct pm_domain_data *pdd;
 101         s64 min_off_time_ns;
 102         s64 off_on_time_ns;
 103
 104         off_on_time_ns = genpd->states[state].power_off_latency_ns +
 105                 genpd->states[state].power_on_latency_ns;
 106
 107
 108         min_off_time_ns = -1;
 109         /*
 110          * Check if subdomains can be off for enough time.
 111          *
 112          * All subdomains have been powered off already at this point.
 113          */
 114         list_for_each_entry(link, &genpd->master_links, master_node) {
 115                 struct generic_pm_domain *sd = link->slave;
 116                 s64 sd_max_off_ns = sd->max_off_time_ns;
 117
 118                 if (sd_max_off_ns < 0)
 119                         continue;
 120
 121                 /*
 122                  * Check if the subdomain is allowed to be off long enough for
 123                  * the current domain to turn off and on (that's how much time
 124                  * it will have to wait worst case).
 125                  */
 126                 if (sd_max_off_ns <= off_on_time_ns)
 127                         return false;
 128
 129                 if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
 130                         min_off_time_ns = sd_max_off_ns;
 131         }
 132
 133         /*
 134          * Check if the devices in the domain can be off enough time.
 135          */
 136         list_for_each_entry(pdd, &genpd->dev_list, list_node) {
 137                 struct gpd_timing_data *td;
 138                 s64 constraint_ns;
 139
 140                 /*
 141                  * Check if the device is allowed to be off long enough for the
 142                  * domain to turn off and on (that's how much time it will
 143                  * have to wait worst case).
 144                  */
 145                 td = &to_gpd_data(pdd)->td;
 146                 constraint_ns = td->effective_constraint_ns;
 147                 /* default_suspend_ok() need not be called before us. */
 148                 if (constraint_ns < 0) {
 149                         constraint_ns = dev_pm_qos_read_value(pdd->dev);
 150                         constraint_ns *= NSEC_PER_USEC;
 151                 }
 152                 if (constraint_ns == 0)
 153                         continue;
 154
 155                 /*
 156                  * constraint_ns cannot be negative here, because the device has
 157                  * been suspended.
 158                  */
 159                 if (constraint_ns <= off_on_time_ns)
 160                         return false;
 161
 162                 if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
 163                         min_off_time_ns = constraint_ns;
 164         }
 165
 166         /*
 167          * If the computed minimum device off time is negative, there are no
 168          * latency constraints, so the domain can spend arbitrary time in the
 169          * "off" state.
 170          */
 171         if (min_off_time_ns < 0)
 172                 return true;
 173
 174         /*
 175          * The difference between the computed minimum subdomain or device off
 176          * time and the time needed to turn the domain on is the maximum
 177          * theoretical time this domain can spend in the "off" state.
 178          */
 179         genpd->max_off_time_ns = min_off_time_ns -
 180                 genpd->states[state].power_on_latency_ns;
 181         return true;
 182 }
 183
 184 /**
 185  * default_power_down_ok - Default generic PM domain power off governor routine.
 186  * @pd: PM domain to check.
 187  *
 188  * This routine must be executed under the PM domain's lock.
 189  */
 190 static bool default_power_down_ok(struct dev_pm_domain *pd)
 191 {
 192         struct generic_pm_domain *genpd = pd_to_genpd(pd);
 193         struct gpd_link *link;
 194
 195         if (!genpd->max_off_time_changed)
 196                 return genpd->cached_power_down_ok;
 197
 198         /*
 199          * We have to invalidate the cached results for the masters, so
 200          * use the observation that default_power_down_ok() is not
 201          * going to be called for any master until this instance
 202          * returns.
 203          */
 204         list_for_each_entry(link, &genpd->slave_links, slave_node)
 205                 link->master->max_off_time_changed = true;
 206
 207         genpd->max_off_time_ns = -1;
 208         genpd->max_off_time_changed = false;
 209         genpd->cached_power_down_ok = true;
 210         genpd->state_idx = genpd->state_count - 1;
 211
 212         /* Find a state to power down to, starting from the deepest. */
 213         while (!__default_power_down_ok(pd, genpd->state_idx)) {
 214                 if (genpd->state_idx == 0) {
 215                         genpd->cached_power_down_ok = false;
 216                         break;
 217                 }
 218                 genpd->state_idx--;
 219         }
 220
 221         return genpd->cached_power_down_ok;
 222 }
 223
 224 static bool always_on_power_down_ok(struct dev_pm_domain *domain)
 225 {
 226         return false;
 227 }
 228
 229 struct dev_power_governor simple_qos_governor = {
 230         .suspend_ok = default_suspend_ok,
 231         .power_down_ok = default_power_down_ok,
 232 };
 233
 234 /**
 235  * pm_genpd_gov_always_on - A governor implementing an always-on policy
 236  */
 237 struct dev_power_governor pm_domain_always_on_gov = {
 238         .power_down_ok = always_on_power_down_ok,
 239         .suspend_ok = default_suspend_ok,
 240 };