[Intel-gfx] Potential BUG in drm/i915/execlists: Reset RING registers upon resume

[Greg Kroah-Hartman]

On Mon, Mar 20, 2017 at 11:24:38AM -0400, Eric Blau wrote:
> On Mon, Mar 20, 2017 at 11:13 AM, Greg Kroah-Hartman
> <gregkh at linuxfoundation.org> wrote:
> > On Mon, Mar 20, 2017 at 05:01:34PM +0200, Jani Nikula wrote:
> >> On Tue, 14 Mar 2017, Eric Blau <eblau at eblau.com> wrote:
> >> > That's funny. I have a MacBook Pro 12,1 from late 2015. Hibernate
> >> > failed for me in 4.9.6 through 4.9.8 (possibly earlier as well, I do
> >> > no recall) without the patch. The patch you reference fixed my problem
> >> > and apparently many others based on the bug reports:
> >> >
> >> > https://bugs.freedesktop.org/show_bug.cgi?id=96526
> >> >
> >> > I applied the patch myself in 4.9.6 through 4.9.8 and hibernate works
> >> > for me. I have run vanilla 4.9.9 and 4.10.1 and in both hibernate
> >> > works.
> >>
> >> So I'm quite surprised
> >>
> >> commit f2a0409a08502d64fbe3990354dff5902b08d2fb
> >> Author: Chris Wilson <chris at chris-wilson.co.uk>
> >> Date:   Wed Sep 21 14:51:08 2016 +0100
> >>
> >>     drm/i915/execlists: Reset RING registers upon resume
> >>
> >>     commit bafb2f7d4755bf1571bd5e9a03b97f3fc4fe69ae upstream.
> >>
> >> ended up in v4.9.9 considering that the upstream commit is not annotated
> >> for stable, it has no Fixes: tags, and I can't find any backport
> >> requests or even notifications for it in my mails. (Admittedly I'm not
> >> subscribed on stable@, but I'd expect our lists, maintainers or
> >> developers be Cc'd.)
> >
> > Eric sent this to the stable list a few times, my mistake for not seeing
> > he hadn't also cc:ed the developer list.
> >
> > Want me to revert it?
> >
> > thanks,
> >
> > greg k-h
> 
> My apologies. I'm new to requesting stable patches, but I thought
> sending to the stable mailing lists would keep the proper folks in the
> loop. Sorry about that.
> 
> The bug that the commit fixes has quite a long documentation trail:
> 
> [BAT execlists] Sporadic - gem_exec_suspend basic-s4 GPU hang after resume
> https://bugs.freedesktop.org/show_bug.cgi?id=96526
> 
> I've had problems with that one and this one that is not fixed in 4.10.x stable:
> 
> [Regression BDW] kernel panic in Intel i915 module, complete system
> freeze in 4.10-rc2
> https://bugs.freedesktop.org/show_bug.cgi?id=99295

So, what needs to be done here?

Do I need to revert something in 4.9? Add something?  Do something else?

totally confused,

greg k-h