[REGRESSION][BISECTED] on 5.11 GPU clock is stuck at the lowest value

Brief summary of the problem:

Update from linux 5.10 to linux 5.11.11 caused games to start lagging. Some research showed that that /sys/class/drm/card1/device/pp_dpm_mclk on 5.11.11 is always at 150Mhz, whereas when booting 5.10.27 kernel, it correctly scales to 1000Mhz whenever under load.

Hardware description:

• CPU: Intel(R) Core(TM) i5-7200U CPU @ 2.50GHz
• GPU: Topaz XT [Radeon R7 M260/M265 / M340/M360 / M440/M445 / 530/535 / 620/625 Mobile]
• Laptop: DELL Inspiron 5767
• System Memory: 8G
• Display(s): 1
• Type of Diplay Connection: eDP

System information:

• Archlinux
• Kernel version: 5.11.11
• AMD package version: No package

How to reproduce the issue:

1. Run DRI_PRIME=1 xonotic-glx
2. Go to menu Multiplayer → Media. It should show demos, press a button Timedemo at the bottom.
3. Switch to a terminal and execute cat /sys/class/drm/card1/device/pp_dpm_mclk

Expected

Frequency is highest possible, so:

0: 150Mhz
1: 1000Mhz *

Actual

Frequency is the lowest possible, which is:

0: 150Mhz *
1: 1000Mhz

Attached files:

• Dmesg log 5.11.11 (BAD): dmesg-5.11.11.log
• Dmesg log 5.10.27 (GOOD): dmesg-5.10.27.log
• Xorg log: Xorg.0.log