Reuse framebuffer after a kexec (amdgpu / efifb)

[Guilherme G. Piccoli]

Thanks again Alex! Some comments inlined below:

On 09/12/2021 15:06, Alex Deucher wrote:
> Not really in a generic way.  It's asic and platform specific.  In
> addition most modern displays require link training to bring up the
> display, so you can't just save and restore registers.

Oh sure, I understand that. My question is more like: is there a way,
inside amdgpu driver, to save this state before taking
over/overwriting/reprogramming the device? So we could (again, from
inside the amdgpu driver) dump this pre-saved state in the shutdown
handler, for example, having the device in a "pre-OS" state when the new
kexec'ed kernel starts.

> 
> The drivers are asic and platform specific.  E.g., the driver for
> vangogh is different from renoir is different from skylake, etc.  The
> display programming interfaces are asic specific.

Cool, that makes sense! But if you (or anybody here) know some of these
GOP drivers, e.g. for the qemu/qxl device, I'm just curious to
see/understand how complex is the FW driver to just put the
device/screen in a usable state.

Cheers,


Guilherme