Arch Linux does not currently have the latest version of the Linux kernel with the Vega DC patches in the repo, so you’ll have to download it from another repository.
- 123[mesa-git]SigLevel = PackageOptionalServer = http://pkgbuild.com/~lcarlier/$repo/$arch
sudo pacman -Syu
Install Linux 4.12 for AMD GPUs
sudo pacman -S linux-amd-staging linux-firmware-git mesa-git
Once the packages are available in a few weeks this will not be necessary. This is a similar situation as to when the RX 480 first launched. One thing to note is Chrome is currently super buggy and artifacts like crazy. So much so that it’s unusable. Also I noticed some weird mouse cursor flickering in Gnome, but that was only when I first logged in. I tried playing some Quake III and it worked perfectly.
This is no longer required as all of the packages are now in the repo. Just use the latest Linux kernel and latest Mesa that Arch has.