https://bugs.freedesktop.org/show_bug.cgi?id=48357
Bug #: 48357 Summary: Display resolutions not detected correctly after startup with VGA over DisplayPort Classification: Unclassified Product: DRI Version: unspecified Platform: x86-64 (AMD64) OS/Version: Linux (All) Status: NEW Severity: normal Priority: medium Component: DRM/Radeon AssignedTo: dri-devel@lists.freedesktop.org ReportedBy: heroeschman@gmx.de
Created attachment 59545 --> https://bugs.freedesktop.org/attachment.cgi?id=59545 dmesg
Hi. One of my monitors is a VGA LCD connected over DisplayPort. After startup not all resolutions are detected but only resolutions up to 1024x768. However if i disconnect the monitor and reconnect it again (at 287.472381 in the log file) all screen resolutions are detected correctly.
The initial detection does not work and dmesg shows "[drm:radeon_dp_i2c_aux_ch], aux i2c too many retries, giving up" error messages. drm_helper_probe_single_connector_modes() then falls back and probes some modes up to 1024x768 that is why higher resolutions are missing. No idea why it works after reconnecting the monitor.
dmesg log is "dmesg | grep drm" with drm.debug=0x0e from a 3.4-rc1 kernel but the problem already happend in earlier versions. The problem also happens if only the VGA monitor is connected.