PM / runtime: Optimize the use of device links

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>

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 876c62b12462792b546a99ea00b23309c5505871..d0c9df5cdd9ed5f2098500dabb8a6b7b16cfb244 100644 (file)
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -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);

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index 462f90e952f84fdfb2e5383d98cb061f1b038f2a..ba7b4a8c07e5e2f3c9edf70ca7a792e2128847a6 100644 (file)
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -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.

diff --git a/include/linux/pm.h b/include/linux/pm.h
index 721a70241fcdcbacd61d2a63704ca8a36967f592..ccfe00ecc7e64b92e3ca4d2a01e6329394d3adcd 100644 (file)
--- a/include/linux/pm.h
+++ b/include/linux/pm.h
@@ -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;

diff --git a/include/linux/pm_runtime.h b/include/linux/pm_runtime.h
index c2ee87138e4affb30f620f69c98907f7b256a449..73814877537dd2432674ca9359e3c36cf03af89c 100644 (file)
--- a/include/linux/pm_runtime.h
+++ b/include/linux/pm_runtime.h
@@ -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 */