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// SPDX-License-Identifier: GPL-2.0
/*
* drivers/base/power/domain_governor.c - Governors for device PM domains.
*
* Copyright (C) 2011 Rafael J. Wysocki <rjw@sisk.pl>, Renesas Electronics Corp.
*/
#include <linux/kernel.h>
#include <linux/pm_domain.h>
#include <linux/pm_qos.h>
#include <linux/hrtimer.h>
#include <linux/cpuidle.h>
#include <linux/cpumask.h>
#include <linux/ktime.h>
static int dev_update_qos_constraint(struct device *dev, void *data)
{
s64 *constraint_ns_p = data;
s64 constraint_ns;
if (dev->power.subsys_data && dev->power.subsys_data->domain_data) {
struct gpd_timing_data *td = dev_gpd_data(dev)->td;
/*
* Only take suspend-time QoS constraints of devices into
* account, because constraints updated after the device has
* been suspended are not guaranteed to be taken into account
* anyway. In order for them to take effect, the device has to
* be resumed and suspended again.
*/
constraint_ns = td ? td->effective_constraint_ns :
PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
} else {
/*
* The child is not in a domain and there's no info on its
* suspend/resume latencies, so assume them to be negligible and
* take its current PM QoS constraint (that's the only thing
* known at this point anyway).
*/
constraint_ns = dev_pm_qos_read_value(dev, DEV_PM_QOS_RESUME_LATENCY);
constraint_ns *= NSEC_PER_USEC;
}
if (constraint_ns < *constraint_ns_p)
*constraint_ns_p = constraint_ns;
return 0;
}
/**
* default_suspend_ok - Default PM domain governor routine to suspend devices.
* @dev: Device to check.
*
* Returns: true if OK to suspend, false if not OK to suspend
*/
static bool default_suspend_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_suspend_ok;
spin_unlock_irqrestore(&dev->power.lock, flags);
return ret;
}
td->constraint_changed = false;
td->cached_suspend_ok = false;
td->effective_constraint_ns = 0;
constraint_ns = __dev_pm_qos_resume_latency(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 == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS) {
/* "No restriction", so the device is allowed to suspend. */
td->effective_constraint_ns = PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS;
td->cached_suspend_ok = true;
} else if (constraint_ns == 0) {
/*
* This triggers if one of the children that don't belong to a
* domain has a zero PM QoS constraint and it's better not to
* suspend then. effective_constraint_ns is zero already and
* cached_suspend_ok is false, so bail out.
*/
return false;
} else {
constraint_ns -= td->suspend_latency_ns +
td->resume_latency_ns;
/*
* effective_constraint_ns is zero already and cached_suspend_ok
* is false, so if the computed value is not positive, return
* right away.
*/
if (constraint_ns <= 0)
return false;
td->effective_constraint_ns = constraint_ns;
td->cached_suspend_ok = true;
}
/*
* The children have been suspended already, so we don't need to take
* their suspend latencies into account here.
*/
return td->cached_suspend_ok;
}
static void update_domain_next_wakeup(struct generic_pm_domain *genpd, ktime_t now)
{
ktime_t domain_wakeup = KTIME_MAX;
ktime_t next_wakeup;
struct pm_domain_data *pdd;
struct gpd_link *link;
if (!(genpd->flags & GENPD_FLAG_MIN_RESIDENCY))
return;
/*
* Devices that have a predictable wakeup pattern, may specify
* their next wakeup. Let's find the next wakeup from all the
* devices attached to this domain and from all the sub-domains.
* It is possible that component's a next wakeup may have become
* stale when we read that here. We will ignore to ensure the domain
* is able to enter its optimal idle state.
*/
list_for_each_entry(pdd, &genpd->dev_list, list_node) {
next_wakeup = to_gpd_data(pdd)->td->next_wakeup;
if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
if (ktime_before(next_wakeup, domain_wakeup))
domain_wakeup = next_wakeup;
}
list_for_each_entry(link, &genpd->parent_links, parent_node) {
struct genpd_governor_data *cgd = link->child->gd;
next_wakeup = cgd ? cgd->next_wakeup : KTIME_MAX;
if (next_wakeup != KTIME_MAX && !ktime_before(next_wakeup, now))
if (ktime_before(next_wakeup, domain_wakeup))
domain_wakeup = next_wakeup;
}
genpd->gd->next_wakeup = domain_wakeup;
}
static bool next_wakeup_allows_state(struct generic_pm_domain *genpd,
unsigned int state, ktime_t now)
{
ktime_t domain_wakeup = genpd->gd->next_wakeup;
s64 idle_time_ns, min_sleep_ns;
min_sleep_ns = genpd->states[state].power_off_latency_ns +
genpd->states[state].residency_ns;
idle_time_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));
return idle_time_ns >= min_sleep_ns;
}
static bool __default_power_down_ok(struct dev_pm_domain *pd,
unsigned int state)
{
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;
off_on_time_ns = genpd->states[state].power_off_latency_ns +
genpd->states[state].power_on_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->parent_links, parent_node) {
struct genpd_governor_data *cgd = link->child->gd;
s64 sd_max_off_ns = cgd ? cgd->max_off_time_ns : -1;
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;
/*
* 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;
/*
* Zero means "no suspend at all" and this runs only when all
* devices in the domain are suspended, so it must be positive.
*/
if (constraint_ns == PM_QOS_RESUME_LATENCY_NO_CONSTRAINT_NS)
continue;
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;
}
/*
* 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->gd->max_off_time_ns = min_off_time_ns -
genpd->states[state].power_on_latency_ns;
return true;
}
/**
* _default_power_down_ok - Default generic PM domain power off governor routine.
* @pd: PM domain to check.
* @now: current ktime.
*
* This routine must be executed under the PM domain's lock.
*
* Returns: true if OK to power down, false if not OK to power down
*/
static bool _default_power_down_ok(struct dev_pm_domain *pd, ktime_t now)
{
struct generic_pm_domain *genpd = pd_to_genpd(pd);
struct genpd_governor_data *gd = genpd->gd;
int state_idx = genpd->state_count - 1;
struct gpd_link *link;
/*
* Find the next wakeup from devices that can determine their own wakeup
* to find when the domain would wakeup and do it for every device down
* the hierarchy. It is not worth while to sleep if the state's residency
* cannot be met.
*/
update_domain_next_wakeup(genpd, now);
if ((genpd->flags & GENPD_FLAG_MIN_RESIDENCY) && (gd->next_wakeup != KTIME_MAX)) {
/* Let's find out the deepest domain idle state, the devices prefer */
while (state_idx >= 0) {
if (next_wakeup_allows_state(genpd, state_idx, now)) {
gd->max_off_time_changed = true;
break;
}
state_idx--;
}
if (state_idx < 0) {
state_idx = 0;
gd->cached_power_down_ok = false;
goto done;
}
}
if (!gd->max_off_time_changed) {
genpd->state_idx = gd->cached_power_down_state_idx;
return gd->cached_power_down_ok;
}
/*
* We have to invalidate the cached results for the parents, so
* use the observation that default_power_down_ok() is not
* going to be called for any parent until this instance
* returns.
*/
list_for_each_entry(link, &genpd->child_links, child_node) {
struct genpd_governor_data *pgd = link->parent->gd;
if (pgd)
pgd->max_off_time_changed = true;
}
gd->max_off_time_ns = -1;
gd->max_off_time_changed = false;
gd->cached_power_down_ok = true;
/*
* Find a state to power down to, starting from the state
* determined by the next wakeup.
*/
while (!__default_power_down_ok(pd, state_idx)) {
if (state_idx == 0) {
gd->cached_power_down_ok = false;
break;
}
state_idx--;
}
done:
genpd->state_idx = state_idx;
gd->cached_power_down_state_idx = genpd->state_idx;
return gd->cached_power_down_ok;
}
static bool default_power_down_ok(struct dev_pm_domain *pd)
{
return _default_power_down_ok(pd, ktime_get());
}
#ifdef CONFIG_CPU_IDLE
static bool cpu_power_down_ok(struct dev_pm_domain *pd)
{
struct generic_pm_domain *genpd = pd_to_genpd(pd);
struct cpuidle_device *dev;
ktime_t domain_wakeup, next_hrtimer;
ktime_t now = ktime_get();
s64 idle_duration_ns;
int cpu, i;
/* Validate dev PM QoS constraints. */
if (!_default_power_down_ok(pd, now))
return false;
if (!(genpd->flags & GENPD_FLAG_CPU_DOMAIN))
return true;
/*
* Find the next wakeup for any of the online CPUs within the PM domain
* and its subdomains. Note, we only need the genpd->cpus, as it already
* contains a mask of all CPUs from subdomains.
*/
domain_wakeup = ktime_set(KTIME_SEC_MAX, 0);
for_each_cpu_and(cpu, genpd->cpus, cpu_online_mask) {
dev = per_cpu(cpuidle_devices, cpu);
if (dev) {
next_hrtimer = READ_ONCE(dev->next_hrtimer);
if (ktime_before(next_hrtimer, domain_wakeup))
domain_wakeup = next_hrtimer;
}
}
/* The minimum idle duration is from now - until the next wakeup. */
idle_duration_ns = ktime_to_ns(ktime_sub(domain_wakeup, now));
if (idle_duration_ns <= 0)
return false;
/* Store the next domain_wakeup to allow consumers to use it. */
genpd->gd->next_hrtimer = domain_wakeup;
/*
* Find the deepest idle state that has its residency value satisfied
* and by also taking into account the power off latency for the state.
* Start at the state picked by the dev PM QoS constraint validation.
*/
i = genpd->state_idx;
do {
if (idle_duration_ns >= (genpd->states[i].residency_ns +
genpd->states[i].power_off_latency_ns)) {
genpd->state_idx = i;
return true;
}
} while (--i >= 0);
return false;
}
struct dev_power_governor pm_domain_cpu_gov = {
.suspend_ok = default_suspend_ok,
.power_down_ok = cpu_power_down_ok,
};
#endif
struct dev_power_governor simple_qos_governor = {
.suspend_ok = default_suspend_ok,
.power_down_ok = default_power_down_ok,
};
/*
* pm_domain_always_on_gov - A governor implementing an always-on policy
*/
struct dev_power_governor pm_domain_always_on_gov = {
.suspend_ok = default_suspend_ok,
};