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Date: Thu, 14 Jan 2016 02:56:53 +0100
From: "Rafael J. Wysocki" <rjw@...ysocki.net>
To: Linux PM list <linux-pm@...r.kernel.org>
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Alan Stern <stern@...land.harvard.edu>,
Grant Likely <grant.likely@...aro.org>,
Mark Brown <broonie@...nel.og>, Rob Herring <robh@...nel.org>,
Tomeu Vizoso <tomeu.vizoso@...labora.com>,
Thierry Reding <treding@...dia.com>,
Dmitry Torokhov <dtor@...gle.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Michael Turquette <mturquette@...libre.com>
Subject: [RFC][PATCH 5/5] PM core: Optimize the use of device links for runtime PM
From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
If the device has no links to suppliers that should be used for
runtime PM (links with DEVICE_LINK_PM_RUNTIME set), there is no
reason to walk the list of suppliers for that device during
runtime suspend and resume.
Add a simple mechanism to detect that case and possibly avoid the
extra unnecessary overhead.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
drivers/base/core.c | 6 ++++++
drivers/base/power/runtime.c | 23 ++++++++++++++++++++---
include/linux/pm.h | 1 +
include/linux/pm_runtime.h | 4 ++++
4 files changed, 31 insertions(+), 3 deletions(-)
Index: linux-pm/include/linux/pm.h
===================================================================
--- linux-pm.orig/include/linux/pm.h
+++ linux-pm/include/linux/pm.h
@@ -596,6 +596,7 @@ struct dev_pm_info {
unsigned int use_autosuspend:1;
unsigned int timer_autosuspends:1;
unsigned int memalloc_noio:1;
+ unsigned int links_count;
enum rpm_request request;
enum rpm_status runtime_status;
int runtime_error;
Index: linux-pm/drivers/base/power/runtime.c
===================================================================
--- linux-pm.orig/drivers/base/power/runtime.c
+++ linux-pm/drivers/base/power/runtime.c
@@ -270,6 +270,7 @@ static int __rpm_callback(int (*cb)(stru
{
struct devlink *link;
int retval, idx;
+ bool use_links = dev->power.links_count > 0;
if (dev->power.irq_safe) {
spin_unlock(&dev->power.lock);
@@ -283,7 +284,7 @@ static int __rpm_callback(int (*cb)(stru
* routine returns, so it is safe to read the status outside of
* the lock.
*/
- if (dev->power.runtime_status == RPM_RESUMING) {
+ if (use_links && dev->power.runtime_status == RPM_RESUMING) {
idx = device_links_read_lock();
list_for_each_entry_rcu(link, &dev->consumer_links, c_node)
@@ -314,8 +315,9 @@ static int __rpm_callback(int (*cb)(stru
*
* Do that if resume fails too.
*/
- if ((dev->power.runtime_status == RPM_SUSPENDING && !retval)
- || (dev->power.runtime_status == RPM_RESUMING && retval)) {
+ if (use_links
+ && ((dev->power.runtime_status == RPM_SUSPENDING && !retval)
+ || (dev->power.runtime_status == RPM_RESUMING && retval))) {
idx = device_links_read_lock();
fail:
@@ -1525,6 +1527,21 @@ void pm_runtime_clean_up_links(struct de
device_links_read_unlock(idx);
}
+void pm_runtime_new_link(struct device *dev)
+{
+ spin_lock_irq(&dev->power.lock);
+ dev->power.links_count++;
+ spin_unlock_irq(&dev->power.lock);
+}
+
+void pm_runtime_drop_link(struct device *dev)
+{
+ spin_lock_irq(&dev->power.lock);
+ WARN_ON(dev->power.links_count == 0);
+ dev->power.links_count--;
+ spin_unlock_irq(&dev->power.lock);
+}
+
/**
* pm_runtime_force_suspend - Force a device into suspend state if needed.
* @dev: Device to suspend.
Index: linux-pm/include/linux/pm_runtime.h
===================================================================
--- linux-pm.orig/include/linux/pm_runtime.h
+++ linux-pm/include/linux/pm_runtime.h
@@ -56,6 +56,8 @@ extern void pm_runtime_update_max_time_s
s64 delta_ns);
extern void pm_runtime_set_memalloc_noio(struct device *dev, bool enable);
extern void pm_runtime_clean_up_links(struct device *dev);
+extern void pm_runtime_new_link(struct device *dev);
+extern void pm_runtime_drop_link(struct device *dev);
static inline bool pm_children_suspended(struct device *dev)
{
@@ -182,6 +184,8 @@ static inline unsigned long pm_runtime_a
static inline void pm_runtime_set_memalloc_noio(struct device *dev,
bool enable){}
static inline void pm_runtime_clean_up_links(struct device *dev) {}
+static inline void pm_runtime_new_link(struct device *dev) {}
+static inline void pm_runtime_drop_link(struct device *dev) {}
#endif /* !CONFIG_PM */
Index: linux-pm/drivers/base/core.c
===================================================================
--- linux-pm.orig/drivers/base/core.c
+++ linux-pm/drivers/base/core.c
@@ -119,6 +119,9 @@ struct devlink *device_link_add(struct d
get_device(consumer);
link->consumer = consumer;
INIT_LIST_HEAD(&link->c_node);
+ if (flags & DEVICE_LINK_PM_RUNTIME)
+ pm_runtime_new_link(consumer);
+
link->flags = flags;
link->status = (flags & DEVICE_LINK_PROBE_TIME) ?
DEVICE_LINK_CONSUMER_PROBE : DEVICE_LINK_DORMANT;
@@ -161,6 +164,9 @@ static void devlink_del(struct devlink *
dev_info(link->consumer, "Dropping the link to %s\n",
dev_name(link->supplier));
+ if (link->flags & DEVICE_LINK_PM_RUNTIME)
+ pm_runtime_drop_link(link->consumer);
+
list_del_rcu(&link->s_node);
list_del_rcu(&link->c_node);
call_srcu(&device_links_srcu, &link->rcu_head, __devlink_free_srcu);
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