iMX8QM display port

[cp2]

Hi,

we have some problems with the display port on the iMX8QM board from Varisite. Using a dp adapter, only a couple of DP aware monitors work. When using a dp to hdmi adapter no connected monitor is detected. Connecting those monitors directly with hdmi works ok. I tried different 5.4.x kernels (5.4.47/5.4.142) but the error is usually something like:

[drm:cdns_mhdp_get_edid_block] *ERROR* get block[0] edid failed: -22 
[drm:cdns_dp_connector_get_modes] *ERROR* Invalid edid 
[drm] Mode: 1024x768p65000
[drm] Failed to Get DP link ID: -5
[drm:cdns_mhdp_train_link] *ERROR* training failed: -110
[drm:cdns_mhdp_train_link] *ERROR* Failed to start training -110
[drm:cdn_dp_bridge_enable] *ERROR* Failed link train -110

So I overwrote the edid with an edid block from the same monitor I acquired over a working hdmi connection. Now the edid error is gone, however we still get the training error:

[drm:cdns_dp_bridge_mode_set] *ERROR* Failed to get caps -5
[drm:cdns_mhdp_train_link] *ERROR* training failed: -110
[drm:cdns_mhdp_train_link] *ERROR* Failed to start training -110
[drm:cdn_dp_bridge_enable] *ERROR* Failed link train -110

fw is:

[drm] HDP FW Version - ver 34219 verlib 20560

Can you confirm that dp->hdmi adapters should work with the iMX8QM board? Also why do a lot of dp monitors not work (I tested at least 5 monitors where only 2 would work with a direct dp connection)? What else could I do to debug this issue or is there a solution already available?

Thanks