By default the Linux kernel selects the aging Radeon DRM driver for GCN 1.0 “Southern Islands” and GCN 1.1 “Sea Islands” hardware (as well as all older ATI/AMD GPUs) while it’s GCN 1.2 and newer that defaults to the modern AMDGPU kernel driver. But for years there has been experimental GCN 1.0/1.1 support available via kernel module options, but now for the original GCN GPUs that code is at risk of being dropped…

Source: Phoronix – The Experimental GCN 1.0 GPU Support Might Be Dropped From AMDGPU Linux Driver