Reuse framebuffer after a kexec (amdgpu / efifb)

[Christian König]

Am 10.12.21 um 16:24 schrieb Guilherme G. Piccoli:
> On 10/12/2021 12:13, Christian König wrote:
>> [...]
>> How about issuing a PCIe reset and re-initializing the ASIC with just
>> the VBIOS?
>>
>> That should be pretty straightforward I think.
>>
>> Christian.
>
> Thanks Christian, that'd be perfect! Is it feasible? Per Alex comment,
> we'd need to run atombios commands to reprogram the timings, display
> info, etc...like a small driver would do, a full init.
>
> Also, what kind of PCIe reset is recommended for this adapter? Like a
> hot reset, powering-off/re-power, FLR or that MODE2 reset present in
> amdgpu code? Remembering this is an APU device.

Well, Alex is the expert on that.

APU makes the whole thing pretty tricky since the VBIOS is part of the 
system BIOS there and I'm not sure you can only re-initialize the GPU 
without a complete reset.

On dGPUs just making sure the ROM is mapped and calling the VESA modeset 
BIOS functions might already do the trick.

Christian.

>
> Thanks a lot!
>