From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Linux ACPI <linux-acpi@vger.kernel.org>,
        Linux PCI <linux-pci@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        Bjorn Helgaas <bhelgaas@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Mika Westerberg <mika.westerberg@linux.intel.com>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        Linux USB <linux-usb@vger.kernel.org>,
        Mathias Nyman <mathias.nyman@linux.intel.com>,
        Felipe Balbi <balbi@kernel.org>,
        Mario Limonciello <mario_limonciello@dell.com>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Dominik Brodowski <linux@dominikbrodowski.net>,
        Hans De Goede <hdegoede@redhat.com>
Subject: Re: [PATCH 2/6] USB / PCI / PM: Allow the PCI core to do the resume cleanup
Date: Fri, 09 Jun 2017 01:01:45 +0200
Message-ID: <4103609.n9yJNxPNSu@aspire.rjw.lan>
User-Agent: KMail/4.14.10 (Linux/4.12.0-rc1+; KDE/4.14.9; x86_64; ; )
In-Reply-To: <Pine.LNX.4.44L0.1706081124310.1949-100000@iolanthe.rowland.org>
References: <Pine.LNX.4.44L0.1706081124310.1949-100000@iolanthe.rowland.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2032
Lines: 51

On Thursday, June 08, 2017 11:24:55 AM Alan Stern wrote:
> On Thu, 8 Jun 2017, Rafael J. Wysocki wrote:
> 
> > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> > 
> > 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@intel.com>
> > ---
> >  drivers/usb/core/hcd-pci.c |    7 +------
> >  1 file changed, 1 insertion(+), 6 deletions(-)
> > 
> > Index: linux-pm/drivers/usb/core/hcd-pci.c
> > ===================================================================
> > --- linux-pm.orig/drivers/usb/core/hcd-pci.c
> > +++ linux-pm/drivers/usb/core/hcd-pci.c
> > @@ -584,12 +584,7 @@ static int hcd_pci_suspend_noirq(struct
> >  
> >  static int hcd_pci_resume_noirq(struct device *dev)
> >  {
> > -	struct pci_dev		*pci_dev = to_pci_dev(dev);
> > -
> > -	powermac_set_asic(pci_dev, 1);
> > -
> > -	/* Go back to D0 and disable remote wakeup */
> > -	pci_back_from_sleep(pci_dev);
> > +	powermac_set_asic(to_pci_dev(dev), 1);
> >  	return 0;
> >  }
> 
> Acked-by: Alan Stern <stern@rowland.harvard.edu>

Thanks!