On Wed, 3 Aug 2016, Heiner Kallweit wrote:
> Since commit 71723f95463d "PM / runtime: print error when activating a
> child to unactive parent" I see the following error message:
>
> scsi host2: usb-storage 1-3:1.0
> scsi host2: runtime PM trying to activate child device host2 but parent
> (1-3:1.0) is not active
>
> Digging into it it seems to be related to the problem described in the
> commit message for cd998ded5c12 "i2c: designware: Prevent runtime
> suspend during adapter registration" as scsi_add_host also calls
> device_add and after the call to device_add the parent device is
> suspended.
>
> Fix this by using the approach from the mentioned commit and getting
> the runtime pm reference before calling scsi_add_host.
Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
There's nothing wrong with this patch; it's a worthwhile thing to do
because it can prevent an unnecessary runtime-suspend/resume cycle.
Still, it looks like the real problem here may lie in
drivers/scsi/hosts.c. Commit bc4f24014de5 ("[SCSI] implement runtime
Power Management") added a call to pm_runtime_set_active() in
scsi_add_host_with_dma() _after_ device_add() instead of _before_.
If that were changed, this problem would not have occurred.
Alan Stern
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