[PATCH] PM / runtime: Document steps for device removal

From: Krzysztof Kozlowski
Date: Sat Mar 12 2016 - 01:02:33 EST

Put a reminder that during device removal drivers should revert all PM
runtime changes from the probe. Also add a note that
pm_runtime_disable() won't wait for pending suspend requests if
autosuspend is not disabled before.

Signed-off-by: Krzysztof Kozlowski <krzk@xxxxxxxxxx>
Documentation/power/runtime_pm.txt | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/Documentation/power/runtime_pm.txt b/Documentation/power/runtime_pm.txt
index 7328cf85236c..c05e5a17a52d 100644
--- a/Documentation/power/runtime_pm.txt
+++ b/Documentation/power/runtime_pm.txt
@@ -410,7 +410,8 @@ drivers/base/power/runtime.c and include/linux/pm_runtime.h:
field was previously zero, this prevents subsystem-level runtime PM
callbacks from being run for the device), make sure that all of the
pending runtime PM operations on the device are either completed or
- canceled; returns 1 if there was a resume request pending and it was
+ canceled (although this depends on disabling autosuspend before
+ calling this); returns 1 if there was a resume request pending and it was
necessary to execute the subsystem-level resume callback for the device
to satisfy that request, otherwise 0 is returned

@@ -586,6 +587,10 @@ drivers to make their ->remove() callbacks avoid races with runtime PM directly,
but also it allows of more flexibility in the handling of devices during the
removal of their drivers.

+Drivers in ->remove() callback should undo the runtime PM changes done
+in ->probe(). Usually this means calling pm_runtime_disable(),
+pm_runtime_dont_use_autosuspend() etc.
The user space can effectively disallow the driver of the device to power manage
it at run time by changing the value of its /sys/devices/.../power/control
attribute to "on", which causes pm_runtime_forbid() to be called. In principle,