Re: [PATCH v2 2/8] USB / PCI / PM: Allow the PCI core to do the resume cleanup

[Rafael J. Wysocki]

On Tuesday, June 13, 2017 10:52:52 AM Greg KH wrote:
> On Mon, Jun 12, 2017 at 10:49:40PM +0200, Rafael J. Wysocki wrote:
> > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > 
> > hcd_pci_resume_noirq() used as a universal _resume_noirq handler for
> > PCI USB controllers calls pci_back_from_sleep() which is unnecessary
> > and may become problematic.
> > 
> > It is unnecessary, because the PCI bus type carries out post-suspend
> > cleanup of all PCI devices during resume and that covers all things
> > done by the pci_back_from_sleep().  There is no reason why USB cannot
> > follow all of the other PCI devices in that respect.
> > 
> > It will become problematic after subsequent changes that make it
> > possible to go back to sleep again after executing dpm_resume_noirq()
> > if no valid system wakeup events have been detected at that point.
> > Namely, calling pci_back_from_sleep() at the _resume_noirq stage
> > will cause the wakeup status of the devices in question to be cleared
> > and if any of them has triggered system wakeup, that event may be
> > missed then.
> > 
> > For the above reasons, drop the pci_back_from_sleep() invocation
> > from hcd_pci_resume_noirq().
> > 
> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> > Acked-by: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
> 
> Acked-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

Thanks!