Bug 18072

Summary:	Probing, false LVDS detection [enabled in VBT but not connected!]
Product:	Drivers	Reporter:	Anisse Astier (anisse)
Component:	Video(DRI - Intel)	Assignee:	drivers_video-dri-intel (drivers_video-dri-intel)
Status:	CLOSED CODE_FIX
Severity:	normal	CC:	chris, florian
Priority:	P1
Hardware:	All
OS:	Linux
Kernel Version:	2.6.36-rc3	Subsystem:
Regression:	No	Bisected commit-id:
Attachments:	Dmesg of wrong resolution/modeline detection, followed by xrandr commands. /sys/kernel/debug/dri/0/i915_opregion Dmidecode output for MSI AE1920 Probe 0xa0 on LVDS port before declaring we attached.

Description Anisse Astier 2010-09-08 10:52:47 UTC

Created attachment 29292 [details]
Dmesg of wrong resolution/modeline detection, followed by xrandr commands.

On an all in one desktop computer, resolution won't be properly detected, and it will show a black band on the right (screen shifted on the left).

Running xrandr auto-setting on "VGA1" output fixes it:
# xrandr
Screen 0: minimum 320 x 200, current 1024 x 768, maximum 4096 x 4096
LVDS1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0*+   85.0     75.0     70.1     60.0* 
   832x624        74.6  
   800x600        85.1     72.2     75.0     60.3     56.2  
   640x480        85.0     72.8     75.0     59.9  
   720x400        85.0  
   640x400        85.1  
   640x350        85.1  
VGA1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 410mm x 230mm
   1366x768       60.0 +
   1280x720       60.0  
   1024x768       75.1     70.1     60.0* 
   800x600        75.0     60.3  
   640x480        60.0  
# xrandr --output VGA1 --auto
# xrandr
Screen 0: minimum 320 x 200, current 1366 x 768, maximum 4096 x 4096
LVDS1 connected 1024x768+0+0 (normal left inverted right x axis y axis) 0mm x 0mm
   1024x768       60.0*+   85.0     75.0     70.1     60.0* 
   832x624        74.6  
   800x600        85.1     72.2     75.0     60.3     56.2  
   640x480        85.0     72.8     75.0     59.9  
   720x400        85.0  
   640x400        85.1  
   640x350        85.1  
VGA1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 410mm x 230mm
   1366x768       60.0*+
   1280x720       60.0  
   1024x768       75.1     70.1     60.0  
   800x600        75.0     60.3  
   640x480        60.0  


Lspci of this machine is in attachment 28041 [details] .

Please note that to obtain this log, I used Daniel Vetters's intel-gtt-rework branch, that fixed another boot-blocking bug 16891 .
Also, this bug might be a regression between 2.6.36-rc2 and 2.6.36-rc3, as previous tests with -rc2 didn't show this behavior.

Comment 1 Anisse Astier 2010-09-08 11:03:42 UTC

Created attachment 29302 [details]
/sys/kernel/debug/dri/0/i915_opregion

Comment 2 Chris Wilson 2010-09-11 09:21:36 UTC

IIRC, the display is connected via the VGA and the LVDS is not actually connected to anything?

In which case the VBT is lying and we need to apply a quirk for the false LVDS. Can you attach a dmidecode for the machine?

Comment 3 Anisse Astier 2010-09-11 20:38:12 UTC

Indeed, it's an all-in-one computer, but I don't know on which output the screen is connected. xrandr output seems to say it's on VGA1.
 
Also, it's weird, because it used to work with 2.6.34.1 without a quirk. It also worked when I tested Daniel Vetter's branch but that it was based on 2.6.36-rc2.
That's why I said I thought it was a regression.
Now maybe the code is supposed to behave more "correctly" now and the right way is to add a quirk for this board. I don't know, as I'm not familiar with recent changes.

I'll provide dmidecode output on Monday when I have access to the hardware.

Comment 4 Chris Wilson 2010-09-21 12:20:57 UTC

Ah, in which case an xrandr when it was working would help confirm which connector they use for the screen. Similarly, it could be the timing snafu fixed in -rc4.

Comment 5 Anisse Astier 2010-09-22 10:48:49 UTC

xrandr output on 2.6.34.1 :

# xrandr
Screen 0: minimum 320 x 200, current 1366 x 768, maximum 4096 x 4096
VGA1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 410mm x 230mm
   1366x768       60.0*+
   1280x720       60.0  
   1024x768       75.1     70.1     60.0  
   800x600        75.0     60.3  
   640x480        60.0

Comment 6 Anisse Astier 2010-09-22 10:55:51 UTC

Created attachment 30952 [details]
Dmidecode output for MSI AE1920

So VGA1 is indeed the default output.
In case the preferred solution is to add a quirk, here is the dmidecode output in attachment.

Comment 7 Chris Wilson 2010-09-23 11:14:20 UTC

Created attachment 31082 [details]
Probe 0xa0 on LVDS port before declaring we attached.

Comment 8 Anisse Astier 2010-09-28 14:50:57 UTC

It works (sorry for the delay):
[   21.627039] [drm:intel_lvds_init], LVDS did not respond to DDC probe
xrandr output is the same as in comment #5.

I tested directly your drm-intel-next branch, which had commit 428d2e828c0a68206e5158a42451487601dc9194 :
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Thu Sep 23 11:16:49 2010 +0100

    drm/i915/lvds: Probe DDC on creation



Thanks

Comment 9 Chris Wilson 2010-12-16 14:27:12 UTC

Now in mainline.