linux-kernel - [bisected] i915 dpms does not switch back light on

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Date:	Thu, 27 Oct 2011 11:19:23 +0100
From:	"Wouter M. Koolen" <wmkoolen@...ence.uva.nl>
To:	keithp@...thp.com, mjg@...hat.com
CC:	linux-kernel@...r.kernel.org
Subject: [bisected] i915 dpms does not switch back light on

Hi guys,

After update from kernel 3.0.8 to 3.1 I encounter the following problem. 
When power saving turns off the back light, key/mouse activity does not 
turn it back on. I can turn it back on by pressing the "brightness++" key.

The following sequence also leaves the backlight off:
xset dpms force off; xset dpms force on
while the next, conceptually similar sequence, reenables it just fine:
xbacklight -set 0; xbacklight -set 100

In each case the problem only manifests itself on the laptop's internal 
panel. The backlight of a second display panel connected to the mini DVI 
port (using a VGA converter) is turned back on in each case.

My graphics card is a
00:02.0 VGA compatible controller: Intel Corporation Mobile GM965/GL960 
Integrated Graphics Controller (primary) (rev 03)
which is driven by i915.

The problem is perfectly reproducible. Bisection points out that first 
bad commit is aaa6fd2a004147bf32fce05720938236de3361d9

Author: Matthew Garrett <mjg@...hat.com>  2011-08-12 11:11:33
Committer: Keith Packard <keithp@...thp.com>  2011-08-15 20:10:25
Parent: 13d83a672e9bbd52ae82c2f611dfd845a957e8b4 (drm/i915: split out 
PCH refclk update code)
Branches: linux-3.1.y, master, remotes/origin/linux-3.1.y, 
remotes/origin/master
Follows: v3.1-rc1
Precedes: v3.1-rc3

     Not all systems expose a firmware or platform mechanism for 
changing the backlight intensity on i915, so add native driver support.

I am running Debian testing on a MacBook 4,1 with the following X tools.

xorg                                  1:7.6+9
xserver-xorg                          1:7.6+9
xserver-xorg-core                     2:1.11.1.901-2
xserver-xorg-input-all                1:7.6+9
xserver-xorg-input-evdev              1:2.6.0-2+b2
xserver-xorg-input-synaptics          1.4.1-1+b1
xserver-xorg-video-intel              2:2.16.0-1

dmesg, lspci and .config attached.

I hope this information is helpful in sorting out the problem. If not, 
don't hesitate to indicate additional information that would be relevant.

With kind regards,

Wouter Koolen

View attachment "dmesg" of type "text/plain" (89401 bytes)

View attachment "lspci" of type "text/plain" (2038 bytes)

View attachment "config-3.1.0.git" of type "text/plain" (72555 bytes)