On Thursday, October 27, 2016 01:53:03 PM Ulf Hansson wrote:

On 27 October 2016 at 13:41, Geert Uytterhoeven [off-list ref] wrote:

quoted

Hi Ulf,

On Thu, Oct 27, 2016 at 1:23 PM, Ulf Hansson [off-list ref] wrote:

quoted

The smsc911c driver puts its device into low power state when entering
system suspend. Although it doesn't update the device's runtime PM status
to RPM_SUSPENDED, which causes problems for a parent device.

In particular, when the runtime PM status of the parent is requested to be
updated to RPM_SUSPENDED, the runtime PM core prevent this, because it's
forbidden to runtime suspend a device, which has an active child.

Fix this by updating the runtime PM status of the smsc911x device to
RPM_SUSPENDED during system suspend. In system resume, let's reverse that
action by runtime resuming the device and thus also the parent.

Thanks for your patch!

The changelog sounds quite innocent, but this does fix a system crash
during resume from s2ram.

quoted

Signed-off-by: Ulf Hansson <redacted>
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Steve Glendinning <steve.glendinning@shawell.net>
Fixes: 8b1107b85efd ("PM / Runtime: Don't allow to suspend a device with an active child")

While the abovementioned commit made the problem visible, the root cause
was present before, right?

Yes.

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Note that the commit this change fixes is currently queued for 4.10 via
Rafael's linux-pm tree. So this fix should go via that tree as well.

Alternatively, this could go in in v4.9 to avoid the problem from ever
appearing in upstream?

Makes perfect sense! In that case we should remove the fixes tag.

Rafael, can you pick this up for 4.9 rc[n]?

If that is to go into 4.9-rc, it really should go in via the networking tree,
because there is no PM dependency for it as of today.

I can rearrange my 4.10 queue to put this one before the runtime PM commit
exposing the problem in smsc911x, though.

Let me know what you prefer.

Thanks,
Rafael