[Intel-gfx] Problems w/Sandy Bridge & 27" monitor

[Chun-Yu Shei]

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?

Thanks,
Chun-Yu