mesa 18.2.0_rc4
lspci:
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
Cayman PRO [Radeon HD 6950]
glxinfo:
    Device: AMD CAYMAN (DRM 2.50.0 / 4.17.14-gentoo, LLVM 6.0.1) (0x6719)
    Version: 18.2.0

Using Kodi to watch tv using the HTSP plugin, using VDPAU for decoding:
kodi.bin: ../mesa-18.2.0-rc4/src/mesa/state_tracker/st_sampler_view.c:546:
st_get_texture_sampler_view_from_stobj: Assertion `stObj->level_override ||
last_level(stObj) == view->u.tex.last_level' failed.

VAAPI decoding works.