Performance is more than halved in games (used Talos Principle on RADV for
bisection) due to the mclk being stuck at 167 MHz.

commit 42a2d4839bc4f095621d259a3ff5401063b914cc (HEAD, refs/bisect/bad)
Author: Evan Quan <evan.quan@amd.com>
Date:   Fri Jan 25 14:09:40 2019 +0800

    drm/amd/powerplay: support Vega10 SOCclk and DCEFclk dpm level settings

    Enable SOCclk and DCEFclk dpm level retrieving and setting on Vega10.

    Change-Id: Iab35a6cc85cdfcf48f06f7d20b95a52c6feb60d1
    Signed-off-by: Evan Quan <evan.quan@amd.com>
    Reviewed-by: Alex Deucher <alexander.deucher@amd.com>

Kernel cmdline has
amdgpu.exp_hw_support=1 log_buf_len=1 amdgpu.sched_hw_submission=64
amdgpu.gpu_recovery=1 amdgpu.cik_support=1 radeon.cik_support=0
amdgpu.cg_mask=0 amdgpu.pg_mask=0 idle=nomwait


and nothing interesting showing up in dmesg.

I can't CC Evan Quan due to lack of bugzilla account.