AMDGPU Support

[Morris Zuss]

Hi all,

I've been attempting to patch linux-libre for my AMD RX 460 and wanted 
to submit my findings so far.

This is the guide I've followed: 
https://trisquel.info/en/forum/first-development-alpha-iso-images-trisquel-80-flidas#comment-106872

Previously I could only launch into xorg with the "nomodeset" boot 
parameter and there was noticeable stuttering. When I de-blobbed and 
compiled the kernel, I was able to get into xorg without the "nomodeset" 
parameter. The stuttering isn't as prominent anymore but the amdgpu 
module still isn't loading.

One small quirk is that when I reach the tty login prompt, the screen 
freezes but there is still the ability to type in the username/password 
and execute commands, you just have to guess where you are currently at. 
But once I entered startx, everything started functioning normally. I 
assume the issue can be mitigated by using a display manager but I 
haven't tested this yet.

When I plug in a second monitor, I get a duplicate output but xrandr 
doesn't seem to recognize it. The only available resolutions are 
"1920x1080" and "640x480"


Currently I'm doing everything on Parabola, the kernel used is 5.10.89, 
on a BIOS/GPT setup with LVM on LUKS.

Relevant logs/information:

Dmesg output on modprobe amdgpu: https://termbin.com/ec0x

Xorg log: https://termbin.com/zh5w

Modifications done to the deblob-5.10 script: https://termbin.com/pjpz

.config for compiling the kernel: 
https://git.parabola.nu/abslibre.git/plain/libre/linux-libre/config.x86_64


If any further information or testing is required, please let me know 
and I'd be willing to assist.

-- Morris Zuss