the amdgpu ucode package is missing a firmware file for Tonga GPUs under linux 4.9.1: Jan 07 11:54:19 localhost kernel: amdgpu 0000:01:00.0: Direct firmware load for amdgpu/tonga_k_smc.bin failed with error -2 Jan 07 11:54:19 localhost kernel: [drm:amdgpu_cgs_get_firmware_info [amdgpu]] *ERROR* Failed to request firmware Jan 07 11:54:19 localhost kernel: [ powerplay ] SMU Firmware start failed Jan 07 11:54:19 localhost kernel: [ powerplay ] smc start failed Jan 07 11:54:19 localhost kernel: [drm:amdgpu_device_init [amdgpu]] *ERROR* hw_init of IP block <amdgpu_powerplay> failed -22 Jan 07 11:54:19 localhost kernel: amdgpu 0000:01:00.0: amdgpu_init failed the file in question was introduced here: https://git.kernel.org/cgit/linux/kernel/git/stable/linux-stable.git/commit/drivers/gpu/drm/amd/amdgpu/amdgpu_cgs.c?h=linux-4.9.y&id=646cccb55b26b95b981ea9a63512260d0c21cac3 and is available at the ebuild's HOMEPAGE
fixed with sys-firmware/amdgpu-ucode-20161121