[PATCH 1/2] PM: runtime: Only queue an idle check for RPM-linked suppliers

[Brian Norris]

When a device RPM-suspends, it queues up an idle check for all of its
suppliers, in case that device was the last consumer, and those
suppliers are now able to suspend. Today, we do this for all suppliers,
and not only for those suppliers that are marked for use by runtime PM.
This isn't directly harmful, but it is a bit wasteful, and also may
induce unexpected suspend attempts (e.g., if a device was purposely last
touched with pm_runtime_put_noidle()).

To avoid excess idle checks, only call pm_request_idle() on linked
suppliers that opted into runtime PM.

Noticed by inspection of trace logs.

This is not expected to have a functional impact on systems that are
using device links properly, and should only be considered an
optimization.

Fixes: 5244f5e2d801 ("PM: runtime: Defer suspending suppliers")
Signed-off-by: Brian Norris <briannorris@xxxxxxxxxxxx>
---

 drivers/base/power/runtime.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/runtime.c b/drivers/base/power/runtime.c
index fab38bc98113..4d84d97f09c4 100644
--- a/drivers/base/power/runtime.c
+++ b/drivers/base/power/runtime.c
@@ -361,7 +361,8 @@ static void rpm_suspend_suppliers(struct device *dev)
 
 	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,
 				device_links_read_lock_held())
-		pm_request_idle(link->supplier);
+		if (device_link_test(link, DL_FLAG_PM_RUNTIME))
+			pm_request_idle(link->supplier);
 
 	device_links_read_unlock(idx);
 }
-- 
2.55.0.970.g62bdec98f9-goog