[Intel-gfx] Regression: Backlight not coming on after resume.

[Takashi Iwai]

At Thu, 28 Feb 2013 17:33:56 +0200,
Jani Nikula wrote:
> 
> On Thu, 28 Feb 2013, James Courtier-Dutton <james.dutton at gmail.com> wrote:
> > Bisect done on tree:
> > git://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git
> > Worked on 3.7.
> > Broken on 3.8
> >
> > Problem: "Backlight not coming on after resume."
> > git finally bisected  for my Samsung Serial 7 Laptop.
> > Bisecting: 0 revisions left to test after this (roughly 0 steps)
> > [cf0a6584aa6d382f802f2c3cacac23ccbccde0cd] drm/i915: write backlight
> > harder     <- This is the problem commit. Seems that fixing some
> > machines breaks others, based on the existing comments on that patch.
> 
> The backlight haunts us again. Could you post the dmesg with
> drm.debug=0xe module parameter, first running vanilla 3.8, and then with
> the bad commit reverted, please?
> 
> Might not be a bad idea to file a bug on Product=DRI,
> Component=DRM/Intel at https://bugs.freedesktop.org (see
> https://01.org/linuxgraphics/documentation/how-report-bugs-0 for
> details) and attach your bisect results and the dmesgs there.

I'm afraid the patch doesn't do it right.  It fixes for Dell, but the
old problem on others back by that.  It was merged before actually
testing on the machines the original fix was intended for.

Now I can confirm a problem (partially) with the latest Linus tree on
a new laptop.  I write "partially" because it happens only during the
splash screen of S4 hibernation, so I've ignored, so far.

James, try to revert that commit.  Does it fix?

If so, you should check the output of intel_reg_dumper at broken and
working states.


Takashi