Bug 79423

Summary: [bisected regression] Screen extemely dim on Dell Latitude D630
Product: DRI Reporter: Marc Milgram <mmilgram>
Component: DRM/IntelAssignee: Jani Nikula <jani.nikula>
Status: CLOSED FIXED QA Contact: Intel GFX Bugs mailing list <intel-gfx-bugs>
Severity: normal    
Priority: high CC: ben, intel-gfx-bugs, jwrdegoede, rdieter
Version: unspecified   
Hardware: x86-64 (AMD64)   
OS: Linux (All)   
Whiteboard:
i915 platform: i915 features:
Attachments:
Description Flags
dmesg from 3.14 kernel
none
i915_opregion from 3.14 boot
none
Output of intel-gpu-tools for good kernel
none
Output of intel_reg_dumper for bad kernel
none
drm/i915: set backlight duty cycle after backlight enable for gen4
none
Output of intel-gpu-tools for fixed kernel none

Description Marc Milgram 2014-05-29 18:31:18 UTC
Previously reported against Fedora here:
https://bugzilla.redhat.com/show_bug.cgi?id=1094066

It seems that the backligt goes dim when the laptop boots.

I bisected the kernel, and found that the issue started with the following commit:
b35684b8fa94e04f55fd38bf672b737741d2f9e2 is the first bad commit
commit b35684b8fa94e04f55fd38bf672b737741d2f9e2
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Thu Nov 14 12:13:41 2013 +0200

    drm/i915: do full backlight setup at enable time
    
    We should now have all the information we need to do a full
    initialization of the backlight registers.
    
    v2: Keep QUIRK_NO_PCH_PWM_ENABLE for now (Imre).
    
    Signed-off-by: Jani Nikula <jani.nikula@intel.com>
    Reviewed-by: Imre Deak <imre.deak@intel.com>
    Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

:040000 040000 0aae5515ca62ff1bfd2e1c2769e30c58b016ffeb 01c2f8cd145f8cf29730908d52e7e89b787a059e M	drivers

I tested with the latest 3.15-rc kernel (as of 2 nights ago), and it has the same problem.
Comment 1 Marc Milgram 2014-05-29 18:33:09 UTC
Created attachment 100119 [details]
dmesg from 3.14 kernel

dmesg from 3.14 kernel with drm.debug=0xe module parameter set
Comment 2 Marc Milgram 2014-05-29 18:34:21 UTC
Created attachment 100120 [details]
i915_opregion from 3.14 boot
Comment 3 Marc Milgram 2014-05-29 18:37:55 UTC
I saved a copy of all the *brightness* files from under /sys when I booted a 3.13 kernel and compared it to when I booted a 3.14 kerel.  The following is the only one that changed:

diff -r 3.13.10-200/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/actual_brightness 3.14.4-200/sys/devices/pci0000:00/0000:00:02.0/drm/card0/card0-LVDS-1/intel_backlight/actual_brightness
1c1
< 255000
---
> 0
Comment 4 Jani Nikula 2014-06-05 15:05:49 UTC
Marc, please attach intel_reg_dumper output from the intel-gpu-tools [1] running 1) the bad commit b35684b8fa94e04f55fd38bf672b737741d2f9e2 and 2) the (presumed good) commit immediately before it.

Running the good kernel, please also try to change the brightness by echoing to the /sys/class/backlight/intel_backlight/brightness file - does it work as expected? Does the dell_backlight work?

[1] http://cgit.freedesktop.org/xorg/app/intel-gpu-tools/
Comment 5 Jani Nikula 2014-06-05 15:13:45 UTC
Same bisect result as [1] but I like to keep both of these open as one as opregion and the other doesn't.

[1] https://bugzilla.kernel.org/show_bug.cgi?id=75791
Comment 6 Marc Milgram 2014-06-05 18:02:56 UTC
Created attachment 100479 [details]
Output of intel-gpu-tools for good kernel
Comment 7 Marc Milgram 2014-06-05 18:05:05 UTC
Created attachment 100480 [details]
Output of intel_reg_dumper for bad kernel

With the good kernel, I could change the backlight by echoing values to /sys/class/backlight/intel_backlight/brightness.
Comment 8 Jani Nikula 2014-06-06 06:33:00 UTC
Created attachment 100506 [details] [review]
drm/i915: set backlight duty cycle after backlight enable for gen4

Please try this patch on top of the bad commit. See if it works and provide the reg dump. Thanks.
Comment 9 Marc Milgram 2014-06-07 01:50:41 UTC
Created attachment 100579 [details]
Output of intel-gpu-tools for fixed kernel

The patch fixes the problem.

Thanks for the great work!
Comment 10 Jani Nikula 2014-06-09 15:25:49 UTC
(In reply to comment #9)
> Created attachment 100579 [details]
> Output of intel-gpu-tools for fixed kernel
> 
> The patch fixes the problem.
> 
> Thanks for the great work!

Thanks for the report and testing. Patch submitted, I'll close when we get it merged.
Comment 11 Jani Nikula 2014-06-10 16:40:54 UTC
commit 6d0cfd569ff908336cbf312e6a211793db843d5a
Author: Jani Nikula <jani.nikula@intel.com>
Date:   Mon Jun 9 18:24:34 2014 +0300

    drm/i915: set backlight duty cycle after backlight enable for gen4

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