https://bugs.freedesktop.org/show_bug.cgi?id=83184
Priority: medium
Bug ID: 83184
Assignee: dri-devel at 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 at 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
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