MCLK fixed to 2000 MHz on Polaris 20 at 1440p75

Brief summary of the problem:

If the display's refresh rate is set to 75 Hz instead of 60, the GPU memory clock is fixed at 2000 MHz. This causes unnecessary power draw and heat. But after a suspend-to-ram the memory clock ramps up and down as expected.

Hardware description:

• CPU: AMD Ryzen 7 1700X
• GPU: Asus RX 580
• Display: AOC Q3279VWF (1440p 75 Hz FreeSync)
• Type of Diplay Connection: DP

System infomration:

• Distro name and Version: Manjaro Linux
• Kernel version: 5.11.0-1-MANJARO
• Older kernel versions make no difference

How to reproduce the issue:

1. After a fresh boot, set the display's refresh rate to 60 Hz. The idle power consumption is low and the memory clock at the minimum (300 MHz):

GFX Clocks and Power:
	300 MHz (MCLK)
	300 MHz (SCLK)
	600 MHz (PSTATE_SCLK)
	1000 MHz (PSTATE_MCLK)
	750 mV (VDDGFX)
	6.253 W (average GPU)

2. Set the refresh rate to 75 Hz. The memory clock is fixed to the maximum frequency and the power consumption rises:

GFX Clocks and Power:
	2000 MHz (MCLK)
	300 MHz (SCLK)
	600 MHz (PSTATE_SCLK)
	1000 MHz (PSTATE_MCLK)
	950 mV (VDDGFX)
	26.6 W (average GPU)

3. Put the computer into suspend-to-ram and wake it up again. Now the refresh rate is still at 75 Hz, but the memory clock is no longer fixed, resulting in a similar power consumption as in the 60 Hz case now. Switching between refresh rates does no longer trigger this behaviour, until I perform a full reboot.

Edit on 28.01.21: Updated with correctly reported power draw values from kernel 5.11

Attached files:

dmesg.txt

amdgpu_pm_info_60Hz.txt

amdgpu_pm_info_75Hz.txt