Well the title already say what is happening... GPU get stuck at maximum clock speed after close any 3d application i find the root of the problem and is coming from that AMDRSServ... after terminate the process the gpu get back to low speeds at idle i don't know what that process do so i just remove him lol everything seems to work just fine so far.
It is DX12 specific problem. "Radeon Settings: Host Service" AMDRSServ.exe is responsible for screen capture. If you delete it all video capture/streaming/replay features will be unavailable.
Well i don't think is isolated issue with DX12... i had the same problem with Vulkan, DX11 and possible DX9 <--- CSGO?
Thanks for the information in what that process do... i don't use any kind of screen capture so this will be a deleted forever to me.