Dear Linux folks,


Using the MST display Dell UP3214Q (two panels) with an AMD system,
the virtual monitor object is not created. GDM and Xfce consider both
panels as separate screens (`xrandr --listmonitors`).

[    0.000000] Linux version 4.20.13.mx64.248 (root-mccexzeWwsejwueTl6BtlB+uRONw2XZa@public.gmane.orggen.mpg.de) (gcc version 7.3.0 (GCC)) #1 SMP Wed Feb 27 14:10:55 CET 2019

[   79.494297] [drm] DM_MST: stopping TM on aconnector: 00000000a8109331 [id: 56]
[   79.494362] [drm] DM_MST: Disabling connector: 00000000776ea22b [id: 63] [master: 00000000a8109331]
[   79.494406] [drm] DM_MST: Disabling connector: 00000000057ebdbb [id: 67] [master: 00000000a8109331]
[   79.781882] snd_hda_intel 0000:00:1f.3: spurious response 0x0:0x2, last cmd=0x201f0500
[   86.028806] [drm] DM_MST: starting TM on aconnector: 00000000a8109331 [id: 56]
[   86.053072] [drm] DM_MST: added connector: 000000001c9b49ed [id: 71] [master: 00000000a8109331]
[   86.108540] [drm] SADs count is: -2, don't need to read it
[   86.386661] [drm:create_stream_for_sink [amdgpu]] *ERROR* Failed to create stream for sink!
[   87.237878] [drm] DM_MST: added connector: 00000000c3ffcbbb [id: 80] [master: 00000000a8109331]
[   87.293028] [drm] SADs count is: -2, don't need to read it
[  206.993344] [drm] DM_MST: stopping TM on aconnector: 00000000a8109331 [id: 56]
[  206.993423] [drm] DM_MST: Disabling connector: 000000001c9b49ed [id: 71] [master: 00000000a8109331]
[  206.993456] [drm] DM_MST: Disabling connector: 00000000c3ffcbbb [id: 80] [master: 00000000a8109331]
[  207.548051] [drm:create_stream_for_sink [amdgpu]] *ERROR* Failed to create stream for sink!
[  207.603193] [drm:create_stream_for_sink [amdgpu]] *ERROR* Failed to create stream for sink!
[  207.762388] traps: xfdesktop[2225] general protection fault ip:7f588981226c sp:7ffee65af370 error:0 in libgobject-2.0.so.0.5800.1[7f58897da000+56000]
[  210.320612] [drm] DM_MST: starting TM on aconnector: 00000000b456cd59 [id: 62]
[  210.343497] [drm] DM_MST: added connector: 00000000735839d5 [id: 73] [master: 00000000b456cd59]
[  210.399168] [drm] SADs count is: -2, don't need to read it
[  210.404454] [drm] DM_MST: added connector: 00000000cccb0c2d [id: 88] [master: 00000000b456cd59]
[  210.675589] [drm] SADs count is: -2, don't need to read it

With an Intel system, the monitor object is shown.

    $ xrandr --listmonitors
    Monitors: 1
     0: +Auto-Monitor-1 3840/698x2160/392+0+0  DP-1-9 DP-1-8

Do you have an idea, what the AMD drivers does differently, and how
to fix this?

Please find the Linux 4.20.13 messages attached.


Kind regards,

Paul