I'm using a monitor with DisplayPort cable. The maximal resolution of that monitor is 2560x1440. When using a 3.7 Linux kernel everything works like a charm. With all the 3.8 kernels I have tried (the "official" Arch kernels 3.8.3 and 3.8.4), I'm not longer able to use that resolution. The maximal resolution I can get is 1920x1080 (the same aspect ratio that the native LCD which is 1366x768). When using the 3.8+ kernel, the machine boots but when X starts, it just produces a black screen or a static screen that is kind of readable. I have tried downgrading the X server, xf86-video-intel, and intel-dir without any change (I'm currently using xf86-video-intel 2.21.6-1, intel-dri 9.1.1-1, and xorg-server 1.14.0-2). Downgrading to Linux 3.7.10-1-ARCH had solved the problem.
Your Xorg.0.log with v3.8 should be a good starting point (it should have most of the information in a condensed format). Also drm.debug=6 dmesgs from booting with v3.7 and v3.8 would be useful.
Created attachment 99011 [details] 3.7.10 Xorg.logs
Created attachment 99021 [details] 3.8.7 Xorg logs
Created attachment 99031 [details] Clean message log from 3.7.10
Created attachment 99041 [details] Clean message log from 3.8.7
Hm, something's strange with your dmesg. drm.debug=6 is set in the kernel cmdline, but all the drm debug noise is missing. Does your distro per chance block out debug output by default? Another thing worth checking is whether the option is indeed set at runtime in /sys/module/parameters. Maybe also check whether dmesg buffer itself (see man dmesg) contains the debug stuff, but it's just filtered out in the log files.
Created attachment 100851 [details] dmesg-3.7.10
Created attachment 100861 [details] dmesg-3.8-10
Created attachment 100871 [details] dmesg-3.9.2
I added three new dmesg files. Let me know if the have what you are looking for. I also tried version 3.9.2 with the same results. Thanks.
Yep, logfiles look good now. But nothing jumped out which would explain what's going on here with your system, it looks like the code is still picking the same DP configuration. And nothing else seems to fail, either. Can you please attempt to bisect where this regression has been introduced?
Created attachment 100891 [details] dmesg-3.8-10-after-xrandr This is everything after I ran xrandr --output DP3 --mode 2560x1440 I also have to run xrandr --output DP3 --mode 1024x768 to get my screen back.
This is working now on 3.10.5 and 3.10.6. Thanks.