Hi Igor and Len,

When I cold boot 3.4 on my laptop the second monitor attached to the 
displayport stays blank. It works fine with 3.3.8 and earlier.

I get two error messages in dmesg:

kernel: video: probe of LNXVIDEO:00 failed with error -5

kernel: [drm:intel_dp_complete_link_train] *ERROR* failed to train DP, 
aborting

When I warm boot 3.4 after running kernel 3.3.8 first, only the first 
message appears and the display works fine.

A bisection based on the occurrence of the first error message resulted in

Author: Igor Murzov <intergalactic.anonymous@gmail.com>  2012-03-30 18:32:08
Committer: Len Brown <len.brown@intel.com>  2012-03-30 20:44:05
Parent: c16fa4f2ad19908a47c63d8fa436a1178438c7e7 (Linux 3.3)
Branches: linux-3.4.y, remotes/origin/linux-3.4.y, remotes/origin/master
Follows: v3.3
Precedes: v3.4-rc1

     ACPI video: Harden video bus adding.

     It is always better to check return values, so add some new checks and
     correct existing ones.

     v2: Be consistent and don't mix errors from -E* and AE_* namespaces.

     Signed-off-by: Igor Murzov <e-mail@date.by>
     Signed-off-by: Len Brown <len.brown@intel.com>


The laptop is a Dell System XPS L702X/0XN71K, BIOS A17 02/22/2012. It 
has two graphics card in Optimus configuration:
00:02.0 VGA compatible controller: Intel Corporation 2nd Generation Core 
Processor Family Integrated Graphics Controller (rev 09)
01:00.0 VGA compatible controller: NVIDIA Corporation Device 124d (rev a1)

I only use the Intel card (which drives the DP port if I am not mistaken)

I hope this is helpful. Please let me know what I can do next to track 
this problem down.

With kind regards,

Wouter Koolen