Comment # 22 on bug 99275 from Reimar Imhof

I also tried to build a 4.8 kernel with 4.9 drm:
git clone -b drm-next-4.9-wip git://people.freedesktop.org/~agd5f/linux
freedektop-drm-next-4.9-wip
cd freedektop-drm-next-4.9-wip
make rpm

That kernel showed no problems.