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