[Regression] 3.18 black screen after boot (bisected)

[Daniel Vetter]

On Sun, Dec 14, 2014 at 12:58:31PM +0100, Heinz Diehl wrote:
> Hi,
> 
> since kernel 3.18 I'm no longer able to run X on my machine. While
> 3.17.6 is fine, 3.18 leaves me with a black screen when starting
> X. Booting into runlevel 1/3 is fine.
> 
> I did a "git bisect", and the offending commit is this one:
> 
> [root at kiera linux-git]# git bisect bad
> 83f45fc360c8e16a330474860ebda872d1384c8c is the first bad commit
> commit 83f45fc360c8e16a330474860ebda872d1384c8c
> Author: Daniel Vetter <daniel.vetter at ffwll.ch>
> Date:   Wed Aug 6 09:10:18 2014 +0200
> 
>     drm: Don't grab an fb reference for the idr
> 
> [....]
> 
> I double-checked, and 3.18 is fine with this commit reverted.
> 
> My machine is an Asus U45JC laptop, and the CPU is an Intel i450M
> (Ironlake). Please contact me if I can help in any way (I'm subscribed
> to lkml, but not to other X or kernel related lists).

Can you please boot with drm.debug=0xf on both good and bad kernels and
then grab dmesg from each?

To make sure we don't forget this please file the above summary plus dmesg
files as a new bug against dri -> drm(intel) on bugs.freedesktop.org.
Please add "[ilk bisected]" to the bug summary so it shows up in all the
right searches for us.

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch