Commit 9262c19d14 "usb: disable port power control if not supported in
wHubCharacteristics" gated enabling runtime pm for usb_port devices on
whether the parent hub supports power control, which causes a
regression. The port must still be allowed to carry out runtime pm
callbacks and receive a -EAGAIN or -EBUSY result. Otherwise the
usb_port device will transition to the pm error state and trigger the
same for the child usb_device.
Prior to the offending commit usb_hub_create_port_device() arranged for
runtime pm to be disabled is dev_pm_qos_expose_flags() failed. Instead,
force the default state of PM_QOS_FLAG_NO_POWER_OFF flag to be set prior
to enabling runtime pm. If that policy can not be set then fail
registration.
Report: http://marc.info/?l=linux-usb&m=140290586301336&w=2
Fixes: 9262c19d14 ("usb: disable port power control if not supported in wHubCharacteristics")
Reported-by: Bjørn Mork <bjorn@mork.no>
Reported-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
e3d1050555