The driver is doing exactly as it is told. The default behaviour of fbcon and X is to create a "mirrored" fb that is the same on all outputs. The display manager then sets whatever mode it wants upon loading. There is no logs here from the failure of the display manager, and since subsequent attempts to change mode work fine, there is no indication that there is a bug in the driver - just userspace.
The driver is doing exactly as it is told. The default behaviour of fbcon and X is to create a "mirrored" fb that is the same on all outputs. The display manager then sets whatever mode it wants upon loading. There is no logs here from the failure of the display manager, and since subsequent attempts to change mode work fine, there is no indication that there is a bug in the driver - just userspace.