Disable Xorg nvidia-auto-select

I have some issues getting a HDReady TV to work on my Jetson TK1. For some reasons the TV doesn’t sync on the reported preferred mode (1920x1080@30). Therefore I added a supported mode to my xorg.conf.jetson-tk1. However when I start the board the TV first syncs for some seconds but then stays black. In Xorg.0.log I see the driver first setting the requested mode but later on setting it again to the “nvidia-auto-select” selected mode.
How can “nvidia-auto-select” be disabled?