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linux-next/drivers/base/power/domain_governor.c
Rafael J. Wysocki b723b0eb91 PM / Domains: Fix computation of maximum domain off time
The default domain power off governor function for generic PM
domains, default_power_down_ok(), may violate subdomain maximum
off time limit by allowing the master domain to be off for too
long.  Namely, it only finds the minium of all device maximum
off times over the domain's devices and uses that to compute the
domain's maximum off time, but it should do the same for the
subdomains.

Fix this problem by modifying default_power_down_ok() to compute
the given domain's maximum off time as the difference between the
minimum off time over all devices and subdomains in the domain and
its power on latency.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
2012-05-11 21:11:44 +02:00

255 lines
6.5 KiB
C

/*
* 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/init.h>
#include <linux/kernel.h>
#include <linux/pm_domain.h>
#include <linux/pm_qos.h>
#include <linux/hrtimer.h>
#ifdef CONFIG_PM_RUNTIME
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.
*/
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;
}
#else /* !CONFIG_PM_RUNTIME */
bool default_stop_ok(struct device *dev)
{
return false;
}
#define default_power_down_ok NULL
#define always_on_power_down_ok NULL
#endif /* !CONFIG_PM_RUNTIME */
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,
};