I can unlock the access to adjust clocks and voltages of my AMD GPU by appending the Kernel parameter
amdgpu.ppfeaturemask=0xffffffff with kernel 5.8.x of Ubuntu 20.04 but not with kernel 5.4. Why not with kernel 5.4 ? With kernel 5.8, I can edit the file
/sys/class/drm/card0/device/pp_od_clk_voltage but with kernel 5.4, I can't, as the file is not unlocked, permission deny even with root. I confirm I update grub after each modify. I followed the procedure from: https://wiki.archlinux.org/index.php/AMDGPU
Wiki Achlinux: § OverclockingSince Linux 4.17, it is possible to adjust clocks and voltages of the graphics card via /sys/class/drm/card0/device/pp_od_clk_voltage.
Some of my data:
$ cat /etc/default/grub | grep GRUB_CMDLINE_LINUX_DEFAULT GRUB_CMDLINE_LINUX_DEFAULT="quiet splash amdgpu.ppfeaturemask=0xffffffff" $ ls /sys/class/drm/card0/device | grep pp_od pp_od_clk_voltage $ cat /sys/class/drm/card0/device/pp_od_clk_voltage $ uname -a Linux ASUS-xxx 5.4.0-45-generic #49-Ubuntu SMP Wed Aug 26 13:38:52 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux