https://bugs.freedesktop.org/show_bug.cgi?id=83184

Priority: medium Bug ID: 83184 Assignee: dri-devel@lists.freedesktop.org Summary: Screen flickering at low resolution when monitor is attached via VGA dongle to DVI port Severity: normal Classification: Unclassified OS: Linux (All) Reporter: Rainer.Koenig@ts.fujitsu.com Hardware: x86-64 (AMD64) Status: NEW Version: unspecified Component: DRM/Radeon Product: DRI

Created attachment 105377 --> https://bugs.freedesktop.org/attachment.cgi?id=105377&action=edit dmesg output with drm debug information

Encountered a strange problem with Radeon HD 6250 (or HD 6310) on a Fujitsu D3003-S1x mainboard. Occurs with every tested linux distribution and older and newer kernels.

Problem occurs only when a monitor is attached via VGA to the DVI port. If the monitor is attached via DVI then the problem does not occur.

Problem is that - Monitor is flickering sporadically - Monitor resolution is fixed to 1024x768 instead of higher resolutions that are possible - xrandr shows 2 monitors while just one monitor is attached

Tried to debug this with kernel parameter drm.debug=14 (dmesg log is attached) and found the following messages that would explain the flickering screen.

[ 4.098364] [drm:radeon_connector_analog_encoder_conflict_solve] 1: conflicting encoders switching off DVI-I-1 [ 4.098369] [drm:radeon_connector_analog_encoder_conflict_solve] in favor of VGA-1 [ 4.219817] [drm:radeon_connector_analog_encoder_conflict_solve] 1: conflicting encoders switching off VGA-1 [ 4.219830] [drm:radeon_connector_analog_encoder_conflict_solve] in favor of DVI-I-1 [ 4.231344] [drm:radeon_connector_analog_encoder_conflict_solve] 1: conflicting encoders switching off DVI-I-1 [ 4.231350] [drm:radeon_connector_analog_encoder_conflict_solve] in favor of VGA-1 [ 13.949336] [drm:radeon_connector_analog_encoder_conflict_solve] 1: conflicting encoders switching off VGA-1 [ 13.949350] [drm:radeon_connector_analog_encoder_conflict_solve] in favor of DVI-I-1 [ 13.967886] [drm:radeon_connector_analog_encoder_conflict_solve] 1: conflicting encoders switching off DVI-I-1 [ 13.967891] [drm:radeon_connector_analog_encoder_conflict_solve] in favor of VGA-1 [ 14.023332] [drm:radeon_connector_analog_encoder_conflict_solve] 1: conflicting encoders switching off VGA-1 [ 14.023345] [drm:radeon_connector_analog_encoder_conflict_solve] in favor of DVI-I-1 [ 14.056688] [drm:radeon_connector_analog_encoder_conflict_solve] 1: conflicting encoders switching off DVI-I-1 [ 14.056694] [drm:radeon_connector_analog_encoder_conflict_solve] in favor of VGA-1

The problem is still to find the root cause that leads to the issue of having "conflicting encoders". Any idea what could cause this behaviour?

Regards Rainer