[PATCH] drm/amdgpu: getting fan speed pwm for vega10 properly

[Yury Zhuravlev]

Hello,

During the setup, the fan manager https://github.com/markusressel/fan2go I
found that my Vega56 was not working correctly. This fan manager expects
what read PWM value should be the same as you wrote before, but it's not
the case. PWM value was volatile, and what is more critical, if I wrote
200, after reading I saw ~70-100, which is very confusing.
After that, I started reading the amdgpu driver, and how fan speed works,
and I found what PWM value was calculated from RPM speed and not correct
for my case (different BIOS or fan configuration?).
Because it looked wrong, I started looking into different implementations
and found that Vega20 used mmCG_FDO_CTRL1 and mmCG_THERMAL_STATUS registers
to calculate the PWM value.
I also checked how we set PWM for Vega10 and found the same registers.
After that, I copy-pasted the function from Vega20 to Vega10, and it
started working much better. It still has some fluctuation, but as I
understand, this behavior is expected.

I have no in-depth information about amdgpu, and the original function may
have been for some reason (maybe for some broken BIOS?), but I suppose
somebody forgot to backport this code after prototype implementation.

It would be my first patch here. Sorry if I skipped some procedures, will
be appreciated it if you help me.
Also, sorry for the patch in the attachment, I have not been using any mail
programs for the last six years, only web clients, and it's strange to do
it nowadays (PRs much more common...).

Regards,
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