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/*
* drivers/base/power/domain_governor.c - Governors for device PM domains.
*
* Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
*
* This file is released under the GPLv2.
*/
#include <linux/kernel.h>
#include <linux/pm_domain.h>
#include <linux/pm_qos.h>
#include <linux/hrtimer.h>
static int dev_update_qos_constraint(struct device *dev, void *data)
{
s64 *constraint_ns_p = data;
s32 constraint_ns = -1;
if (dev->power.subsys_data && dev->power.subsys_data->domain_data)
constraint_ns = dev_gpd_data(dev)->td.effective_constraint_ns;
if (constraint_ns < 0) {
constraint_ns = dev_pm_qos_read_value(dev);
constraint_ns *= NSEC_PER_USEC;
}
if (constraint_ns == 0)
return 0;
/*
* constraint_ns cannot be negative here, because the device has been
* suspended.
*/
if (constraint_ns < *constraint_ns_p || *constraint_ns_p == 0)
*constraint_ns_p = constraint_ns;
return 0;
}
/**
* default_stop_ok - Default PM domain governor routine for stopping devices.
* @dev: Device to check.
*/
static bool default_stop_ok(struct device *dev)
{
struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
unsigned long flags;
s64 constraint_ns;
dev_dbg(dev, "%s()\n", __func__);
spin_lock_irqsave(&dev->power.lock, flags);
if (!td->constraint_changed) {
bool ret = td->cached_stop_ok;
spin_unlock_irqrestore(&dev->power.lock, flags);
return ret;
}
td->constraint_changed = false;
td->cached_stop_ok = false;
td->effective_constraint_ns = -1;
constraint_ns = __dev_pm_qos_read_value(dev);
spin_unlock_irqrestore(&dev->power.lock, flags);
if (constraint_ns < 0)
return false;
constraint_ns *= NSEC_PER_USEC;
/*
* We can walk the children without any additional locking, because
* they all have been suspended at this point and their
* effective_constraint_ns fields won't be modified in parallel with us.
*/
if (!dev->power.ignore_children)
device_for_each_child(dev, &constraint_ns,
dev_update_qos_constraint);
if (constraint_ns > 0) {
constraint_ns -= td->start_latency_ns;
if (constraint_ns == 0)
return false;
}
td->effective_constraint_ns = constraint_ns;
td->cached_stop_ok = constraint_ns > td->stop_latency_ns ||
constraint_ns == 0;
/*
* The children have been suspended already, so we don't need to take
* their stop latencies into account here.
*/
return td->cached_stop_ok;
}
/**
* default_power_down_ok - Default generic PM domain power off governor routine.
* @pd: PM domain to check.
*
* This routine must be executed under the PM domain's lock.
*/
static bool default_power_down_ok(struct dev_pm_domain *pd)
{
struct generic_pm_domain *genpd = pd_to_genpd(pd);
struct gpd_link *link;
struct pm_domain_data *pdd;
s64 min_off_time_ns;
s64 off_on_time_ns;
if (genpd->max_off_time_changed) {
struct gpd_link *link;
/*
* We have to invalidate the cached results for the masters, so
* use the observation that default_power_down_ok() is not
* going to be called for any master until this instance
* returns.
*/
list_for_each_entry(link, &genpd->slave_links, slave_node)
link->master->max_off_time_changed = true;
genpd->max_off_time_changed = false;
genpd->cached_power_down_ok = false;
genpd->max_off_time_ns = -1;
} else {
return genpd->cached_power_down_ok;
}
off_on_time_ns = genpd->power_off_latency_ns +
genpd->power_on_latency_ns;
/*
* It doesn't make sense to remove power from the domain if saving
* the state of all devices in it and the power off/power on operations
* take too much time.
*
* All devices in this domain have been stopped already at this point.
*/
list_for_each_entry(pdd, &genpd->dev_list, list_node) {
if (pdd->dev->driver)
off_on_time_ns +=
to_gpd_data(pdd)->td.save_state_latency_ns;
}
min_off_time_ns = -1;
/*
* Check if subdomains can be off for enough time.
*
* All subdomains have been powered off already at this point.
*/
list_for_each_entry(link, &genpd->master_links, master_node) {
struct generic_pm_domain *sd = link->slave;
s64 sd_max_off_ns = sd->max_off_time_ns;
if (sd_max_off_ns < 0)
continue;
/*
* Check if the subdomain is allowed to be off long enough for
* the current domain to turn off and on (that's how much time
* it will have to wait worst case).
*/
if (sd_max_off_ns <= off_on_time_ns)
return false;
if (min_off_time_ns > sd_max_off_ns || min_off_time_ns < 0)
min_off_time_ns = sd_max_off_ns;
}
/*
* Check if the devices in the domain can be off enough time.
*/
list_for_each_entry(pdd, &genpd->dev_list, list_node) {
struct gpd_timing_data *td;
s64 constraint_ns;
if (!pdd->dev->driver)
continue;
/*
* Check if the device is allowed to be off long enough for the
* domain to turn off and on (that's how much time it will
* have to wait worst case).
*/
td = &to_gpd_data(pdd)->td;
constraint_ns = td->effective_constraint_ns;
/* default_stop_ok() need not be called before us. */
if (constraint_ns < 0) {
constraint_ns = dev_pm_qos_read_value(pdd->dev);
constraint_ns *= NSEC_PER_USEC;
}
if (constraint_ns == 0)
continue;
/*
* constraint_ns cannot be negative here, because the device has
* been suspended.
*/
constraint_ns -= td->restore_state_latency_ns;
if (constraint_ns <= off_on_time_ns)
return false;
if (min_off_time_ns > constraint_ns || min_off_time_ns < 0)
min_off_time_ns = constraint_ns;
}
genpd->cached_power_down_ok = true;
/*
* If the computed minimum device off time is negative, there are no
* latency constraints, so the domain can spend arbitrary time in the
* "off" state.
*/
if (min_off_time_ns < 0)
return true;
/*
* The difference between the computed minimum subdomain or device off
* time and the time needed to turn the domain on is the maximum
* theoretical time this domain can spend in the "off" state.
*/
genpd->max_off_time_ns = min_off_time_ns - genpd->power_on_latency_ns;
return true;
}
static bool always_on_power_down_ok(struct dev_pm_domain *domain)
{
return false;
}
struct dev_power_governor simple_qos_governor = {
.stop_ok = default_stop_ok,
.power_down_ok = default_power_down_ok,
};
/**
* pm_genpd_gov_always_on - A governor implementing an always-on policy
*/
struct dev_power_governor pm_domain_always_on_gov = {
.power_down_ok = always_on_power_down_ok,
.stop_ok = default_stop_ok,
};
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