Re: Problems w/Sandy Bridge & 27" monitor

[Chun-Yu Shei <cshei@cs.indiana.edu>]

On 8/15/2012 6:47 PM, Daniel Vetter wrote:
> On Wed, Aug 15, 2012 at 06:38:10PM -0400, Chun-Yu Shei wrote:
>> Hi,
>>
>> I recently upgraded to a 27" monitor (2560x1440) from a 23" one
>> (1920x1080), and had to switch to Windows because the new monitor is
>> unusable in Linux.  Today, about a month later, I decided to give
>> Linux another try, since there have been several updates to the
>> Intel graphics driver since then.
>>
>> Unfortunately, it seems that it's still unusable with
>> xf86-video-intel 2.20.3 -- after a little while, the video signal to
>> the 27" monitor completely stops, and it goes into power saving
>> mode.  I'm running dual monitors with the old 23", and that one
>> continues running fine when this happens.  This happens on my
>> ThinkPad X220 (i5-2540M).  The 27" is connected via DisplayPort, and
>> the 23" via DVI.  SNA is enabled, if it makes any difference (I
>> haven't tried turning it off, but I probably should).  This is the
>> biggest problem I'm facing when it comes to Linux support.
>>
>> I also gave the new "TearFree" option a try, and while it does a
>> great job of eliminating tearing, it makes the two monitors become
>> mirrors of each other for some reason.  If I take a screenshot with
>> the GNOME tool, the screenshot comes out as expected (unmirrored),
>> but the video output on the two monitors is mirrored in reality.
>> Disabling "TearFree" fixes this.
>>
>> Also, when I'm using the ThinkPad's built-in display, it sometimes
>> turns off for no apparent reason, although it's not too big of a
>> deal since a suspend/resume cycle seems to fix things (and I haven't
>> used 2.20.3 long enough to experience this yet).
>>
>> Any ideas/things I can do to help track these issues down?
>
> For the screen blanking issues, the kernel is the important part. Please
> boot with drm.debug=0xe added to your kernel bootline and grab the full
> dmesg.
> -Daniel
>

OK, I finally got around to doing this... I just upgraded to the 3.5.3 
kernel and xf86-video-intel 2.20.5 as well.

Here's the initial dmesg upon bootup: http://pastebin.com/41F2AA0f

And here's the dmesg right after the 27" goes blank: 
http://pastebin.com/3CTRETQ4 (not completely blank, though... there are 
a few lines at the very left & top edge of the display)

A few seconds later, the display came back, and here's the dmesg right 
after that: http://pastebin.com/9mdfY5P1

Chun-Yu