Ubuntu - GPU - AMD GPU - Overclocking - Boot parameter

It is required to unlock access to adjust clocks and voltages in sysfs by appending the Kernel parameter amdgpu.ppfeaturemask=0xffffffff.

NOTE: Not all bits are defined, and new features may be added over time.

Setting all 32 bits may enable unstable features that cause problems such as screen flicker or broken resume from suspend.
It should be sufficient to set the PP_OVERDRIVE_MASK bit, 0x4000, in combination with the default ppfeaturemask.

To compute a reasonable parameter for your system, execute:

printf 'amdgpu.ppfeaturemask=0x%x\n' "$(($(cat /sys/module/amdgpu/parameters/ppfeaturemask) | 0x4000))"

returns:

amdgpu.ppfeaturemask=0xfff7ffff