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

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Date:   Tue, 25 Jul 2017 22:35:37 +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 05:59:04 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);