Re: [PATCH v4 05/14] usb: defer suspension of superspeed port while peer is powered

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On Fri, 7 Feb 2014, Dan Williams wrote:

> >> +     /* power on our usb3 peer before this usb2 port to prevent a usb3
> >> +      * device from degrading to its usb2 connection
> >> +      */
> >> +     if (!hub_is_superspeed(hdev) && peer)
> >> +             pm_runtime_get_sync(&peer->dev);
> >> +
> >
> > Have you considered what would happen if this runs before the ACPI data
> > causes the peers to be re-matched?
> 
> If userspace is sets pm_qos_no_poweroff to 0 before we have figured
> out the peer then suspending this port may lead to a disconnect.

What if userspace sets pm_qos_no_poweroff to 0 _after_ we have figured 
out the peer and _before_ the ACPI data causes us to change the peer?

Alan Stern

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