The tracing tool is misinterpreting the ioctl number. It’s not actually a Radeon call, it’s most likely a decoding artifact from strace.
On Jetson AGX Orin, vkcube (Vulkan) will open a DRM render node like /dev/dri/renderD128 provided by the NVIDIA Tegra nvgpu stack. When you strace ioctls, strace has to pick some C macro name to label each DRM ioctl number. Many vendor-specific DRM ioctls share the same numeric values across drivers. Since strace can’t know which kernel driver a given fd belongs to, it may print the first matching symbol it knows (e.g., DRM_IOCTL_RADEON_GEM_PWRITE) although the call is going to the NVIDIA render node.
And if aren’t using it, nvstart-weston.sh very nicely stops gdm3, sets up and starts weston for non-root user.