linux-kernel - Re: [PATCH] PM / USB: hcd_pci: Skip secondary root hub check for HCD

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Date:   Tue, 25 Jul 2017 23:36:40 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     Linux USB <linux-usb@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Felipe Balbi <balbi@...nel.org>
Subject: Re: [PATCH] PM / USB: hcd_pci: Skip secondary root hub check for HCD_DEAD()

On Tuesday, July 25, 2017 05:06:40 PM Alan Stern wrote:
> On Tue, 25 Jul 2017, Rafael J. Wysocki wrote:
> 
> > On Tuesday, July 25, 2017 05:59:04 PM Rafael J. Wysocki wrote:
> > > On Tuesday, July 25, 2017 10:05:03 AM Alan Stern wrote:
> > > > On Tue, 25 Jul 2017, Rafael J. Wysocki wrote:
> > > > 
> > > > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > > 
> > > > > If HCD_DEAD(hcd) is "true" in check_root_hub_suspended(), it is
> > > > > rather pointless to check the secondary root hub, so return early
> > > > > then.
> > > > > 
> > > > > This actually fixes occasional suspend failures on one of my test
> > > > > machines.
> > > > > 
> > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > > > > ---
> > > > >  drivers/usb/core/hcd-pci.c |    3 +++
> > > > >  1 file changed, 3 insertions(+)
> > > > > 
> > > > > 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
> > > > > @@ -427,6 +427,9 @@ static int check_root_hub_suspended(stru
> > > > >  		dev_warn(dev, "Root hub is not suspended\n");
> > > > >  		return -EBUSY;
> > > > >  	}
> > > > > +	if (HCD_DEAD(hcd))
> > > > > +		return 0;
> > > > > +
> > > > >  	if (hcd->shared_hcd) {
> > > > >  		hcd = hcd->shared_hcd;
> > > > >  		if (HCD_RH_RUNNING(hcd)) {
> > > > 
> > > > While this is an okay solution, IMO it would be more reliable and more 
> > > > general to have usb_hc_died() clear the HCD_FLAG_RH_RUNNING bit and set 
> > > > the HCD_FLAG_DEAD bit in the shared hcd.  Right now it only does these 
> > > > things for the primary.
> > > > 
> > > > Would you like to write and test a patch to do that?
> > > 
> > > I can do that.
> > 
> > Just to make sure that we are on the same page, is the below what you mean?
> > 
> > ---
> >  drivers/usb/core/hcd.c |    2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > Index: linux-pm/drivers/usb/core/hcd.c
> > ===================================================================
> > --- linux-pm.orig/drivers/usb/core/hcd.c
> > +++ linux-pm/drivers/usb/core/hcd.c
> > @@ -2485,6 +2485,8 @@ void usb_hc_died (struct usb_hcd *hcd)
> >  	}
> >  	if (usb_hcd_is_primary_hcd(hcd) && hcd->shared_hcd) {
> >  		hcd = hcd->shared_hcd;
> > +		clear_bit(HCD_FLAG_RH_RUNNING, &hcd->flags);
> > +		set_bit(HCD_FLAG_DEAD, &hcd->flags);
> >  		if (hcd->rh_registered) {
> >  			clear_bit(HCD_FLAG_POLL_RH, &hcd->flags);
> 
> Yes, exactly.  Does it fix your suspend problem?

Yes, it does.

I guess I should resend it with a changelog and tags, then.

Thanks,
Rafael