HD7640G Trinity weird blue stripes on boot

[slamd64]

I am having this problem long before, but now as of Xorg 1.16 and kernel 3.15 I am forced to use radeon driver, because proprietary driver is up to Xorg 1.15 and Linux 3.13.
So, what happens with radeon driver is that it loads driver without any error ([drm] initialized driver) and I get this screen and it's fading to white. It looks like broken screen.

http://imgbox.com/LXh03H2o

I can boot with UMS disabled (passing radeon.modeset=0 in kernel line), but I only have basic graphics support. It started to occur since kernel 3.12. Same result both on Arch Linux and Slackware -current. However, with kernel 3.10 and Xorg 1.12 it works fine.
Is there any solution to this problem rather than downgrading?

[Guest]

Have you tried mainline kernel 3.16?

Could be totally unrelated, but I did have some weird color banding issues going on on my Trinity hardware, but it's been fixed since 3.16 for me.

[slamd64]

I found what caused problem. It is dpm. Leaving it off lets the system to boot: add radeon.dpm=0 to boot parameters.
But without that, it seems that GPU is much hotter. Anyway, it works also with 3.16 on Arch Linux. I don't know if it is because of KDE 4.13, but also brightness controls are now working.
But I managed also to install catalyst instead, because it handles temperature better. It is needed to downgrade Xorg to 1.15 and kernel to 3.13 (on Slackware and other distributions than Arch Linux).