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

[Greg Kroah-Hartman]

On Wed, Apr 12, 2017 at 04:35:47PM +0300, Jani Nikula wrote:
> On Wed, 12 Apr 2017, Greg Kroah-Hartman <gregkh at linuxfoundation.org> wrote:
> > 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,
> 
> I did reply to you [1]:
> 
> >> Want me to revert it?
> >
> > Chris says that would be the correct thing to do. I'm no expert in the
> > area, but IIUC having just that commit backported is not enough,
> > something more would be needed, but we're not sure yet what exactly and
> > if those dependencies can easily be backported.
> 
> "it" being commit f2a0409a0850 ("drm/i915/execlists: Reset RING
> registers upon resume") in 4.9.9+.

Ah, ok, now reverted, thanks.

greg k-h