DELL U2415 monitor detection issue
Submitted by Michiel Janssens
Assigned to Default DRI bug account
As advised on launchpad.net I'm reporting this issue upstream:
HW: HP Elitebook 8749w
video: Mobility Radeon HD 5870
OS: Ubuntu 14.04.2
My Laptop HP Elitebook 8740w has two external screens connected, 1 DELL U2412M connected to vga connector, and 1 DELL U2415 connected to Displayport.
When booting up and with screens attached and active, the 2415 boots in 1024x768 resolution, the 2412 boots at the same moment in 1920x1200 as it should. At the point where the login screen appears the 2415 goes in power save mode, most of the time. After logging in, turning the 2415 off and on, sometimes helps the get the screen active (out of power save). Also switching VT7 to another and back helps.
When it gets active, the resolution is 1024x768, not 1920x1200.
In unity-control-center in display settings the 2415 is displayed as "Unknown Display" and the maximum resolution I can select is 1024x768.
Tried windows 8.1, no issues with both screens.
Tried fglrx, not theses issues, but lag.
Current partial workaround:
Exported edid form U2415 and booting now with kernel commandline parameter drm_kms_helper.edid_firmware=DP-1:edid/U2415.edid
With this workaround, only power save issue exists.
Please advise if you need more info