If you want to try the the latest Mali blob with dsd's xf86-video-armsoc as dicussed here :
http://forum.odroid.com/viewtopic.php?f=77&t=4456#p35809
I've built packages which do this.
PKGBUILD's : https://github.com/gripped/odroid-u2-pkgbuilds
Packages : http://odroidxu.leeharris.me.uk/u2/
To do this you can add a custom repo (as root) :
cat >> /etc/pacman.conf <<EOF
[odroidu]
SigLevel = Never
Server = http://odroidxu.leeharris.me.uk/u2
EOF
And then update pacman :
pacman -Syu
And then install them with pacman :
pacman -S linux-odroidu-r4p0 mali-odroid-r4p0 xf86-video-armsoc-dsd xorg-server-dsd
And you'll need to edit /etc/xorg.conf. Mine now has
# X.Org X server configuration file for xfree86-video-mali
Section "Device"
Identifier "Mali-Fbdev"
Driver "armsoc"
Option "fbdev" "/dev/fb1"
Option "DriverName" "exynos"
EndSection
Section "Screen"
Identifier "Mali-Screen"
Device "Mali-Fbdev"
DefaultDepth 24
EndSection
Section "DRI"
Mode 0666
EndSection
I'm not sure if I'm going to maintain/update these packages, etc as I don't know if I am going to keep using the armsoc driver myself. But the PKGBUILD's are there so you can fork the repo and DIY.