OK let's do this.
MHWD uninstall part
The first step is to remove every video-driver inside mwhd so please remove them.
you can list them by
Here we install all the dependencies that is mostly the latest xserver and linux.
sudo pacman -S "xorg-server>=1.18" "linux>=4.9" xf86-video-amdgpu xf86-input-libinput
Setting up Grub
Because this is experimental we need to tell linux on bootup that it activated the experimental hardware support. Thanks to Philm this is enabled in linux4.9 for GCN 1.0. To do this you need to edit the file
/etc/default/grub look for the line
amdgpu.exp_hw_support=1. So if there is nothing else in this line it should look like this:
And we need to update grub with
Kernel Module loads n' unloads
Because its the most important thing to have amdgpu kernel module (kmod) loaded and radeon blocked, we need to create some files to do that. At first create a file
/etc/modules-load.d/amdgpu.conf with the content
and another file
Next you have to switch Xorgs driver(DDX), because it WILL load the radeon ddx by default. So create another file
/etc/X11/xorg.conf.d/90-mhwd.conf (lets use the manjaro default for this) with just following entry in it (delete everything else if needed)
Identifier "R9270" #identifier can be everything
now restart and you should be on amdgpu