Re: [PATCH] net: smsc911x: Synchronize the runtime PM status during system suspend

From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Ulf Hansson <ulf.hansson@linaro.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Linux PM list <linux-pm@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
	Kevin Hilman <khilman@kernel.org>,
	Lina Iyer <lina.iyer@linaro.org>,
	Jon Hunter <jonathanh@nvidia.com>,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Linus Walleij <linus.walleij@linaro.org>,
	Steve Glendinning <steve.glendinning@shawell.net>
Subject: Re: [PATCH] net: smsc911x: Synchronize the runtime PM status during system suspend
Date: Tue, 01 Nov 2016 05:19:25 +0100	[thread overview]
Message-ID: <3305877.UjuP622RYi@vostro.rjw.lan> (raw)
In-Reply-To: <CAPDyKFprWcita5sbdwTqbdi2CMW4gx7_UB7+kMd9R2rqXdcALQ@mail.gmail.com>

On Thursday, October 27, 2016 01:53:03 PM Ulf Hansson wrote:
> On 27 October 2016 at 13:41, Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> > Hi Ulf,
> >
> > On Thu, Oct 27, 2016 at 1:23 PM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
> >> The smsc911c driver puts its device into low power state when entering
> >> system suspend. Although it doesn't update the device's runtime PM status
> >> to RPM_SUSPENDED, which causes problems for a parent device.
> >>
> >> In particular, when the runtime PM status of the parent is requested to be
> >> updated to RPM_SUSPENDED, the runtime PM core prevent this, because it's
> >> forbidden to runtime suspend a device, which has an active child.
> >>
> >> Fix this by updating the runtime PM status of the smsc911x device to
> >> RPM_SUSPENDED during system suspend. In system resume, let's reverse that
> >> action by runtime resuming the device and thus also the parent.
> >
> > Thanks for your patch!
> >
> > The changelog sounds quite innocent, but this does fix a system crash
> > during resume from s2ram.
> >
> >> Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
> >> Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
> >> Cc: Steve Glendinning <steve.glendinning@shawell.net>
> >> Fixes: 8b1107b85efd ("PM / Runtime: Don't allow to suspend a device with an active child")
> >
> > While the abovementioned commit made the problem visible, the root cause
> > was present before, right?
> 
> Yes.
> 
> >
> >> ---
> >>
> >> Note that the commit this change fixes is currently queued for 4.10 via
> >> Rafael's linux-pm tree. So this fix should go via that tree as well.
> >
> > Alternatively, this could go in in v4.9 to avoid the problem from ever
> > appearing in upstream?
> 
> Makes perfect sense! In that case we should remove the fixes tag.
> 
> Rafael, can you pick this up for 4.9 rc[n]?

If that is to go into 4.9-rc, it really should go in via the networking tree,
because there is no PM dependency for it as of today.

I can rearrange my 4.10 queue to put this one before the runtime PM commit
exposing the problem in smsc911x, though.

Let me know what you prefer.

Thanks,
Rafael