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Subject[update][PATCH 6/7] PM / Domains: Add default power off governor function (v4)
Date
From: Rafael J. Wysocki <rjw@sisk.pl>

Add a function deciding whether or not a given PM domain should
be powered off on the basis of the PM QoS constraints of devices
belonging to it and their PM QoS timing data.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
drivers/base/power/domain.c | 12 +++
drivers/base/power/domain_governor.c | 110 +++++++++++++++++++++++++++++++++++
include/linux/pm_domain.h | 7 ++
3 files changed, 129 insertions(+)
Index: linux/include/linux/pm_domain.h
===================================================================
--- linux.orig/include/linux/pm_domain.h
+++ linux/include/linux/pm_domain.h
@@ -57,8 +57,13 @@ struct generic_pm_domain {
bool suspend_power_off; /* Power status before system suspend */
bool dev_irq_safe; /* Device callbacks are IRQ-safe */
int (*power_off)(struct generic_pm_domain *domain);
+ s64 power_off_latency_ns;
int (*power_on)(struct generic_pm_domain *domain);
+ s64 power_on_latency_ns;
struct gpd_dev_ops dev_ops;
+ s64 break_even_ns; /* Power break even for the entire domain. */
+ s64 max_off_time_ns; /* Maximum allowed "suspended" time. */
+ ktime_t power_off_time;
};

static inline struct generic_pm_domain *pd_to_genpd(struct dev_pm_domain *pd)
@@ -76,6 +81,8 @@ struct gpd_link {
struct gpd_timing_data {
s64 stop_latency_ns;
s64 start_latency_ns;
+ s64 save_state_latency_ns;
+ s64 restore_state_latency_ns;
s64 break_even_ns;
};

Index: linux/drivers/base/power/domain_governor.c
===================================================================
--- linux.orig/drivers/base/power/domain_governor.c
+++ linux/drivers/base/power/domain_governor.c
@@ -10,6 +10,7 @@
#include <linux/kernel.h>
#include <linux/pm_domain.h>
#include <linux/pm_qos.h>
+#include <linux/hrtimer.h>

/**
* default_stop_ok - Default PM domain governor routine for stopping devices.
@@ -28,6 +29,115 @@ bool default_stop_ok(struct device *dev)
&& td->break_even_ns < dev->power.max_time_suspended_ns;
}

+/**
+ * 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_dev_off_time_ns;
+ s64 off_on_time_ns;
+ ktime_t time_now = ktime_get();
+
+ 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;
+ }
+
+ /*
+ * 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;
+
+ sd_max_off_ns -= ktime_to_ns(ktime_sub(time_now,
+ sd->power_off_time));
+ /*
+ * 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;
+ }
+
+ /*
+ * Check if the devices in the domain can be off enough time.
+ */
+ min_dev_off_time_ns = -1;
+ list_for_each_entry(pdd, &genpd->dev_list, list_node) {
+ struct gpd_timing_data *td;
+ struct device *dev = pdd->dev;
+ s64 dev_off_time_ns;
+
+ if (!dev->driver || dev->power.max_time_suspended_ns < 0)
+ continue;
+
+ td = &to_gpd_data(pdd)->td;
+ dev_off_time_ns = dev->power.max_time_suspended_ns -
+ (td->start_latency_ns + td->restore_state_latency_ns +
+ ktime_to_ns(ktime_sub(time_now,
+ dev->power.suspend_time)));
+ if (dev_off_time_ns <= off_on_time_ns)
+ return false;
+
+ if (min_dev_off_time_ns > dev_off_time_ns
+ || min_dev_off_time_ns < 0)
+ min_dev_off_time_ns = dev_off_time_ns;
+ }
+
+ if (min_dev_off_time_ns < 0) {
+ /*
+ * There are no latency constraints, so the domain can spend
+ * arbitrary time in the "off" state.
+ */
+ genpd->max_off_time_ns = -1;
+ return true;
+ }
+
+ /*
+ * The difference between the computed minimum delta and the time needed
+ * to turn the domain on is the maximum theoretical time this domain can
+ * spend in the "off" state.
+ */
+ min_dev_off_time_ns -= genpd->power_on_latency_ns;
+
+ /*
+ * If the difference between the computed minimum delta and the time
+ * needed to turn the domain off and back on on is smaller than the
+ * domain's power break even time, removing power from the domain is not
+ * worth it.
+ */
+ if (genpd->break_even_ns >
+ min_dev_off_time_ns - genpd->power_off_latency_ns)
+ return false;
+
+ genpd->max_off_time_ns = min_dev_off_time_ns;
+ return true;
+}
+
struct dev_power_governor simple_qos_governor = {
.stop_ok = default_stop_ok,
+ .power_down_ok = default_power_down_ok,
};
Index: linux/drivers/base/power/domain.c
===================================================================
--- linux.orig/drivers/base/power/domain.c
+++ linux/drivers/base/power/domain.c
@@ -398,6 +398,17 @@ static int pm_genpd_poweroff(struct gene
}

genpd->status = GPD_STATE_POWER_OFF;
+ genpd->power_off_time = ktime_get();
+
+ /* Update PM QoS information for devices in the domain. */
+ list_for_each_entry_reverse(pdd, &genpd->dev_list, list_node) {
+ struct gpd_timing_data *td = &to_gpd_data(pdd)->td;
+
+ pm_runtime_update_max_time_suspended(pdd->dev,
+ td->start_latency_ns +
+ td->restore_state_latency_ns +
+ genpd->power_on_latency_ns);
+ }

list_for_each_entry(link, &genpd->slave_links, slave_node) {
genpd_sd_counter_dec(link->master);
@@ -1417,6 +1428,7 @@ void pm_genpd_init(struct generic_pm_dom
genpd->resume_count = 0;
genpd->device_count = 0;
genpd->suspended_count = 0;
+ genpd->max_off_time_ns = -1;
genpd->domain.ops.runtime_suspend = pm_genpd_runtime_suspend;
genpd->domain.ops.runtime_resume = pm_genpd_runtime_resume;
genpd->domain.ops.runtime_idle = pm_generic_runtime_idle;


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