On 2021-12-10 10:13 a.m., Christian König wrote:

Am 10.12.21 um 15:25 schrieb Guilherme G. Piccoli:

quoted

On 10/12/2021 11:16, Alex Deucher wrote:> [...]

quoted

Why not just reload the driver after kexec?

Alex

Because the original issue is the kdump case, and we want a very very
tiny kernel - also, the crash originally could have been caused by
amdgpu itself, so if it's a GPU issue, we don't want to mess with that
in kdump. And I confess I tried modprobe amdgpu after a kdump, no
success - kdump won't call shutdown handlers, so GPU will be in a
"rogue" state...

My question was about regular kexec because it's much simpler usually,
we can do whatever we want there. My line of thought was: if I make it
work in regular kexec with a simple framebuffer, I might be able to get
it working on kdump heheh

How about issuing a PCIe reset and re-initializing the ASIC with just 
the VBIOS?

That should be pretty straightforward I think.

Do you actually need to restore the exact boot-up mode? If you have the 
same framebuffer memory layout (width, height, bpp, stride) the precise 
display timing doesn't really matter. So we "just" need to switch to a 
mode that's compatible with the efifb framebuffer parameters and point 
the display engine at the efifb as the scan-out buffer.

Regards,
   Felix

Christian.