Reuse framebuffer after a kexec (amdgpu / efifb)

[Guilherme G. Piccoli]

On 09/12/2021 14:31, Alex Deucher wrote:
> [...] 
> Once the driver takes over, none of the pre-driver state is retained.
> You'll need to load the driver in the new kernel to initialize the
> displays.  Note the efifb doesn't actually have the ability to program
> any hardware, it just takes over the memory region that was used for
> the pre-OS framebuffer and whatever display timing was set up by the
> GOP driver prior to the OS loading.  Once that OS driver has loaded
> the area is gone and the display configuration may have changed.
> 

Hi Christian and Alex, thanks for the clarifications!

Is there any way to save/retain this state before amdgpu takes over?
Would simpledrm be able to program the device again, to a working state?

Finally, do you have any example of such a GOP driver (open source) so I
can take a look? I tried to find something like that in Tianocore
project, but didn't find anything that seemed useful for my issue.

Thanks again!