On Thu, 2011-12-15 at 00:51 +0800, Alan Stern wrote:

On Wed, 14 Dec 2011, Lin Ming wrote:

quoted

On Wed, Dec 14, 2011 at 11:18 AM, Lin Ming [off-list ref] wrote:

quoted

[Patch description from Alan Stern]

If a child device was runtime-suspended when a system suspend began,
then there will be nothing to prevent its parent from
runtime-suspending as soon as it is woken up during the system resume.
Then when the time comes to resume the child, the resume will fail
because the parent is already back at low power.

On the other hand, there are some devices which should remain at low
power across an entire suspend-resume cycle. �The details depend on the
device and the platform.

This suggests that the PM core is not the right place to solve the
problem. �One possible solution is for the subsystem or device driver
to call pm_runtime_get_sync(dev->parent) at the start of the
system-resume procedure and pm_runtime_put_sync(dev->parent) at the
end.

Signed-off-by: Lin Ming <redacted>

Hi Alan,

May I add your SOB?

You can add: Acked-by: Alan Stern [off-list ref]

Did you test this?  Does it do what you want?

Yes, I have tested this and it fixes the problem.

Thanks.

Alan Stern