radeon: Force loading with no microcode - will it damage any hardware?

[Christian König]

Hi Damien,

well there are a whole bunch of firmware files used by radeon for 
different hardware blocks:

1. The firmware for the memory controller (MC).

This one is usually loaded by the VBIOS as well, but we tend to update 
it because the version from the VBIOS is sometimes limited in features 
and full of bugs.

Without working MC you basically get nothing from the hardware, e.g. not 
even a picture on the screen. So what sometimes happens is that when you 
don't update the MC firmware you can only run "classic" VGA resolutions.

2. The firmware for power management.

Named differently for different hardware generations, but essentially 
always the same functionality: Regulating voltages, clocks and fans 
based on load and temperature.

What can happen is that your system overheats without that, but in 
practice you usually need 3D load for the system to heat up 
significantly (there are a few exceptions, e.g. bugs in the VBIOS and 
hardware).

3. The firmware for the 3D command processor (CP).

Without that you don't get any acceleration, not even 2D.

4. The firmware for the multimedia blocks (UVD/VCE).

Without them you don't get hardware accelerated video decoding 
(encoding) and on some occasions problems with power management.

The reason for the power management problems are that the electronics 
responsible for power management "asks" the UVD block how much it has 
TODO. And without the firmware the UVD block never answers.

So to sum it up: It is generally not recommended nor well supported to 
run without firmware, but should at least provide a picture on the screen.

Regards,
Christian.

Am 13.05.2018 um 06:22 schrieb Damien Zammit:
> Can someone with some AMD gpu hardware expertise please advise whether
> forcing cards to continue loading regardless if microcode is missing
> will do damage to hardware long term, for the cards supported by
> 'radeon' driver?
>
> I have heard from someone that it might just be for the 3d CP unit only,
> which might just disable 3d graphics if the microcode is missing on r600
> and rv770.
>
> I want to know if it's okay so we can get basic 2D support in libre
> kernels where the microcode is deblobbed, even though I know it's
> generally not recommended to omit microcode for all kinds of reasons.
>
> Cheers,
> Damien
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