[Intel-gfx] [git pull] i915 fixes

[Jesse Barnes]

On Tue, 8 Mar 2011 14:00:45 +1000
Dave Airlie <airlied at gmail.com> wrote:

> On Tue, Mar 8, 2011 at 7:28 AM, Jim Gettys <jg at freedesktop.org> wrote:
> > On 03/07/2011 07:00 AM, Chris Wilson wrote:
> >>
> >> Dave, hopefully this completes the regression fixes for .38. There is
> >> still some doubt over eDP, with 011b9910bdaf failing for Jim Gettys but
> >> seeming required for other (currently working in .37) machines. And
> >> despite Linus's intervention, backlight controls are still broken for some
> >> users.
> >
> > FWIW:
> >
> > The failure is not so common for me as to claim the change should not go in;
> > and my work around is to suspend/resume the system again.
> 
> The thing with this patch is the only think I can think it could do
> different on your system is timing related.
> 
> I'm a bit worried that I haven't seen much attempt at debugging this
> from the Intel folks,
> since its an 80 line patch it really wouldn't harm if they could
> suggest something.
> 
> It might be interetsing to print out the is_pch_port to make sure it
> never changes,
> and also to see if bypassing the whole new code section added in to
> turn off the CPU FDI and PCH FDI
> helps at all.

I did check out the reg dumps, and the only theory I have is that we're
re-training DP at resume and coming up with a different vswing and/or
pre-emphasis, which could cause trouble.  The patch should only affect
things in a timing sense though like you say.  I'll try to find time
this week to come up with a patch to allow suspend/resume to use fast
link training, and see if that makes things better.

I don't think this is a regression relative to 2.6.37 though?  If not,
we probably shouldn't revert, since the patch referenced fixes so many
other machines...

Jesse