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PM / runtime: Optimize the use of device links

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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@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Rafael J. Wysocki 2016-10-30 17:32:43 +01:00 committed by Greg Kroah-Hartman
parent 21d5c57b37
commit baa8809f60
4 changed files with 38 additions and 10 deletions
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20
drivers/base/core.c
View file

@ -205,14 +205,17 @@ struct device_link *device_link_add(struct device *consumer,
if (!link)
goto out;
if ((flags & DL_FLAG_PM_RUNTIME) && (flags & DL_FLAG_RPM_ACTIVE)) {
if (pm_runtime_get_sync(supplier) < 0) {
pm_runtime_put_noidle(supplier);
kfree(link);
link = NULL;
goto out;
if (flags & DL_FLAG_PM_RUNTIME) {
if (flags & DL_FLAG_RPM_ACTIVE) {
if (pm_runtime_get_sync(supplier) < 0) {
pm_runtime_put_noidle(supplier);
kfree(link);
link = NULL;
goto out;
}
link->rpm_active = true;
}
link->rpm_active = true;
pm_runtime_new_link(consumer);
}
get_device(supplier);
link->supplier = supplier;
@ -296,6 +299,9 @@ static void __device_link_del(struct device_link *link)
dev_info(link->consumer, "Dropping the link to %s\n",
dev_name(link->supplier));
if (link->flags & DL_FLAG_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, __device_link_free_srcu);

23
drivers/base/power/runtime.c
View file

@ -305,6 +305,7 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
__releases(&dev->power.lock) __acquires(&dev->power.lock)
{
int retval, idx;
bool use_links = dev->power.links_count > 0;
if (dev->power.irq_safe) {
spin_unlock(&dev->power.lock);
@ -318,7 +319,7 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
* 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();
retval = rpm_get_suppliers(dev);
@ -341,8 +342,9 @@ static int __rpm_callback(int (*cb)(struct device *), struct device *dev)
*
* 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:
@ -1593,6 +1595,21 @@ void pm_runtime_put_suppliers(struct device *dev)
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.

1
include/linux/pm.h
View file

@ -597,6 +597,7 @@ 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;

4
include/linux/pm_runtime.h
View file

@ -58,6 +58,8 @@ 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_get_suppliers(struct device *dev);
extern void pm_runtime_put_suppliers(struct device *dev);
extern void pm_runtime_new_link(struct device *dev);
extern void pm_runtime_drop_link(struct device *dev);
static inline void pm_suspend_ignore_children(struct device *dev, bool enable)
{
@ -192,6 +194,8 @@ static inline void pm_runtime_set_memalloc_noio(struct device *dev,
static inline void pm_runtime_clean_up_links(struct device *dev) {}
static inline void pm_runtime_get_suppliers(struct device *dev) {}
static inline void pm_runtime_put_suppliers(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 */