https://bugzilla.kernel.org/show_bug.cgi?id=200695
--- Comment #29 from John Doe (anode.dev@gmail.com) --- amdgpu.dc=1 set by default for all kernels since 4.17 and it seems that amdgpu.dc=0 is deprecated attribute as new Display core is replacement for old amdgpu code
5.0 version is works same as 4.20 with a lot of warnings and messages in dmesg https://bugzilla.kernel.org/show_bug.cgi?id=201957