https://bugs.freedesktop.org/show_bug.cgi?id=77673
--- Comment #6 from Christian König deathsimple@vodafone.de --- Please try the attached patch.
We now always use the fixed reference divider if both RADEON_PLL_USE_REF_DIV and RADEON_PLL_USE_FRAC_FB_DIV are set.
If only RADEON_PLL_USE_REF_DIV is set then we only use the fixed value as minimum limit.