[strange workaround found] Kernel 4.01 & radeon => black screen on display port

[orinoco]

I have a AMD graphics card in my desktop (Advanced Micro Devices [AMD/ATI] Juniper XT [Radeon HD 6770]) with two displays (EIZO S2433W on display port and EIZO L767 on dvi port). Since kernel 4.0 the display port behaves strange. I see kdm on both displays but after initialisation of plasma the display on display port gets dark and falls into standby mode. Even with Alt-F1 the display stays black und in standby mode. The display on dvi port works like before showing his part of the plasma desktop.
Booting with kernel 3.19 gives the normal behavior: Two displays with different resolutions and a plasma desktop "sitting" on top of both.


Are there kernel parameters to solve this issue?

[orinoco]

Hello,


after an extensive try & error session I found out that it depends on the resolution of the monitor connected to the display port. With a resolution of 1280x1024 I got an output but that looks terrible on a 24" monitor.


After playing around with the options of the radeon module I had success with

Code Select Expand

options radeon audio=0


I don't understand why because this option should disable hdmi-audio. Strange but it helped.


But I had to pay a price. I lost my dual-screen setup. KDE system configuration won't save my 1920x1200 (24" on display port) and right to it 1280X1024 (19" on dvi port) anymore. Now both displays have 1280x1024 resolution sitting on each other. I have to rearrange both displays and restore optimal resolution manually after each KDE start.

Rule 1: do try & error step by step
Rule 2: remember your steps


I forgot to reenable kscreen2 service. Now eveything is fine again. 

[melmarker]

no clue about mult monitor - but why radeon instead of fglrx?

[orinoco]

In the past I ran into trouble with new siduction kernels und incompatible fglrx versions which ends in an unusable desktop till somebody releases a fixed fglrx.