No power management for AMD Radeon Pro WX 5100

When I install an AMD Radeon Pro WX 5100 in my Linux workstation, the card works out of the box, and runs my desktop environment just fine. However, I have noticed it has a very high power draw at idle, almost 20W - about the same as when it's active.

Hence, it seems the amdgpu kernel driver does not provide much power management for cards like the WX 5100. Can this be added, please?

(In contrast, power management for a consumer card like the RX 550 is excellent.)

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By "at idle" I mean at the login screen, with all users logged out, and after expiry of the screen blanking timeout. That is, the graphics card is not producing a video signal, and the display is in power save mode.

Tests have been performed on openSUSE Leap 15.2, both with and without the Pro drivers from AMD installed. Tests on the latest openSUSE Tumbleweed (kernel 5.3.16) gives similar results.

When testing on Windows 10 with the Pro drivers installed, it works as expected: Power draw at idle is a good 5W, and the fan stops.