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Date: Wed, 25 Apr 2012 21:29:22 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Linux PM list <linux-pm@...r.kernel.org>
Cc: LKML <linux-kernel@...r.kernel.org>, Kevin Hilman <khilman@...com>,
Magnus Damm <magnus.damm@...il.com>, linux-sh@...r.kernel.org,
Mark Brown <broonie@...nsource.wolfsonmicro.com>,
markgross@...gnar.org, Jean Pihet <j-pihet@...com>,
Simon Horman <horms@...ge.net.au>
Subject: [PATCH 1/3] PM / Domains: Rework default device stop governor function, v2
From: Rafael J. Wysocki <rjw@...k.pl>
The existing default device stop governor function for PM domains,
default_stop_ok(), is supposed to check whether or not the device's
PM QoS latency constraint will be violated if the device is stopped
by pm_genpd_runtime_suspend(). However, the computations carried out
by it don't reflect the definition of the PM QoS latency constrait in
Documentation/ABI/testing/sysfs-devices-power.
Make default_stop_ok() follow the definition of the PM QoS latency
constrait. In particular, make it take the device's start and stop
latencies correctly.
Add a new field, effective_constraint_ns, to struct gpd_timing_data
and use it to store the difference between the device's PM QoS
constraint and its resume latency for use by the device's parent
(the effective_constraint_ns values for the children are used for
computing the parent's one along with its PM QoS constraint).
Remove the break_even_ns field from struct gpd_timing_data, because
it's not used any more.
Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
---
drivers/base/power/domain.c | 1
drivers/base/power/domain_governor.c | 55 +++++++++++++++++++++++++++++++----
include/linux/pm_domain.h | 2 -
3 files changed, 52 insertions(+), 6 deletions(-)
Index: linux/drivers/base/power/domain_governor.c
===================================================================
--- linux.orig/drivers/base/power/domain_governor.c
+++ linux/drivers/base/power/domain_governor.c
@@ -14,6 +14,31 @@
#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.
@@ -21,14 +46,34 @@
bool default_stop_ok(struct device *dev)
{
struct gpd_timing_data *td = &dev_gpd_data(dev)->td;
+ s64 constraint_ns;
dev_dbg(dev, "%s()\n", __func__);
- if (dev->power.max_time_suspended_ns < 0 || td->break_even_ns == 0)
- return true;
-
- return td->stop_latency_ns + td->start_latency_ns < td->break_even_ns
- && td->break_even_ns < dev->power.max_time_suspended_ns;
+ constraint_ns = dev_pm_qos_read_value(dev);
+ 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.
+ */
+ 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;
+ /*
+ * The children have been suspended already, so we don't need to take
+ * their stop latencies into account here.
+ */
+ return constraint_ns > td->stop_latency_ns || constraint_ns == 0;
}
/**
Index: linux/include/linux/pm_domain.h
===================================================================
--- linux.orig/include/linux/pm_domain.h
+++ linux/include/linux/pm_domain.h
@@ -93,7 +93,7 @@ struct gpd_timing_data {
s64 start_latency_ns;
s64 save_state_latency_ns;
s64 restore_state_latency_ns;
- s64 break_even_ns;
+ s64 effective_constraint_ns;
};
struct generic_pm_domain_data {
Index: linux/drivers/base/power/domain.c
===================================================================
--- linux.orig/drivers/base/power/domain.c
+++ linux/drivers/base/power/domain.c
@@ -506,6 +506,7 @@ static int pm_genpd_runtime_suspend(stru
if (dev_gpd_data(dev)->always_on)
return -EBUSY;
+ dev_gpd_data(dev)->td.effective_constraint_ns = -1;
stop_ok = genpd->gov ? genpd->gov->stop_ok : NULL;
if (stop_ok && !stop_ok(dev))
return -EBUSY;
--
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