Re: Critical regression in 4.7-rcX

From: Larry Finger
Date: Fri Jul 15 2016 - 11:34:31 EST


On 07/15/2016 09:43 AM, Ville Syrjälä wrote:
On Fri, Jul 15, 2016 at 04:27:27PM +0200, Daniel Vetter wrote:
On Fri, Jul 15, 2016 at 8:55 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
On Thu, 14 Jul 2016, Larry Finger wrote:
To anyone keeping track of regressions in kernel 4.7, I call your attention to
https://bugs.freedesktop.org/show_bug.cgi?id=96675.

This bug causes driver i915 to fail to connect to the display, and results in
a blank screen as soon as the kernel is loaded. The only way to operate with
kernel 4.7 is to add "nomodeset" to the command line. The problem was bisected
to commit f21a21983ef13a ("drm/i915: Splitting intel_dp_detect").

Daniel? Jani? Time to revert?

Yup. Means that I'll get to revert a pile of patches (plus even more
in -next), but that's what we get for not handling regressions timely.
Dave poked me about the same bug already too. But will take a few days
until the pull is in your inbox I guess.

I attached a oneliner to the bug today, that I *think* should fix the
problem.

After I checked out the problem commit and built that kernel with the one-line patch, the display works; however, mainline still fails. I am currently bisecting to find what other commit fails. At a minimum, we should be able to reduce the number of commits that need reverting.

Larry