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

[Jani Nikula]

On Mon, 20 Mar 2017, 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?

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.

BR,
Jani.

-- 
Jani Nikula, Intel Open Source Technology Center