Radeon

Radeon is the open source graphics driver for AMD/ATI Radeon graphics cards that is often replaced by fglrx due to seemingly poor 3D acceleration. This guide will attempt to fix this, mostly by making use of the new feature-set, namely, DRI3.

Disclaimer: This is quite bleeding edge and might not work. Should it fail, you will be on your own.

Before starting

Check your cards feature-set: https://wiki.freedesktop.org/xorg/RadeonFeature/#index6h2 "Decoder ring for engineering vs marketing names" will tell you what model your card actually is.

Back your xorg.conf up by issuing sudo cp /etc/X11/xorg.conf /etc/X11/xorg.conf~

What should I expect?

Run: vblank_mode=0 glxgears & sleep 15 ; killall glxgears

GPU mode	Before	After
r9 280x (gigabyte)	3258.964 FPS	18001.777 FPS

glxgears is a very simple test, but you can use it to test a driver's 3D performance relative to another one. As you can see here, the results speak for themselves and indicate a performance increase of roughly 560%.

Requirements & dependencies

X.Org Server 1.17 (not absolutely necessary, but recommended for stability) media-libs/mesa (the newest version you can find)

  `--  x11-libs/libdrm-2.4.65  (>=2.4.58)
  `--  x11-libs/libpciaccess (>=0.8.0)
  `--  x11-base/xorg-server
  `--  x11-libs/glamor (>=0.6)
  `--  virtual/udev
  `--  x11-proto/fontsproto
  `--  x11-proto/randrproto
  `--  x11-proto/renderproto
  `--  x11-proto/videoproto
  `--  x11-proto/xextproto
  `--  x11-proto/xf86driproto
  `--  x11-proto/xproto
  `--  sys-devel/automake  (>1.15)
  `--  sys-devel/autoconf  (>=2.69)
  `--  sys-devel/libtool  (>=2.4)
  `--  sys-devel/m4
  `--  x11-misc/util-macros-1.19.0  (>=1.18)
  `--  media-fonts/font-util  (>=1.2.0)
  `--  virtual/pkgconfig
  `--  x11-proto/glproto
  `--  x11-proto/dri2proto
  `--  x11-proto/xineramaproto

Note: apt and yum users need only run 'sudo apt-get build-dep xserver-xorg-video-ati' and 'sudo yum-builddep xorg-x11-drv-ati' respectively, to build the dependencies automagically. Arch users can do this with pkgbuild somehow, and gentoo users need only emerge the actual driver to have all the dependencies.

Building

 # git clone git://anongit.freedesktop.org/xorg/driver/xf86-video-ati
 # ./autogen.sh --prefix=/opt/xorg
 # make
 # sudo make install

Afterwards

 # sudo vim /etc/X11/xorg.conf
     Section "Files"
             ModulePath "/opt/xorg/lib/xorg/modules,/usr/lib/xorg/modules"
     EndSection

Make sure you have these as well:

     Section "Module"
             Load "dri"
             Load "dbe" # Double buffer extension // See compatibility on features page
             Load "glx" # OpenGL X protocol interface // See compatibility on features page
             Load "extmod" # Misc. required extension // See compatibility on features page
     EndSection
     
     Section "DRI"
             Group        "video"
             Mode         0666
     EndSection

 #sudo vim /etc/X11/xorg.conf.d/20-radeon
     Section "Device"
             Identifier "radeonVGA"
                         Driver "radeon"
                         Option "AccelMethod" "Glamor" # See compatibility on features page
                         Option "DRI3" "on" # Compatibility not very well documented, remove it if it fails
                         Option "EnablePageFlip" "On"
     EndSection

Feel free to run sudo chattr +i /etc/X11/xorg.conf to keep X from overwriting this (chattr -i will undo this).

Example xorg.conf: http://pastebin.com/aE3e21Bn

IMPORTANT: Recompiling the driver will become a necessity after each X upgrade.

External links

For more info (eg: building Mesa and libdrm from source): http://www.x.org/wiki/radeonBuildHowTo/