second display not working on imac after debian bookworm upgrade

[giorez]

after I reinstalled debian from bullseye to bookworm, my second display stopped working. I actually use 2 displays on both windows and mac osx. the machine is imac 27, with VGA compatible controller [0300]: Advanced Micro Devices, Inc. [AMD/ATI] Broadway PRO [Mobility Radeon HD 5850]. I also tryed differente cable, but no luck. I checked dmesg:

[drm:radeon_pci_probe [radeon]] *ERROR* radeon kernel modesetting for R600 or later requires firmware installed
See https://wiki.debian.org/Firmware for information about missing firmware

I installed installed firmware-amd-graphics, but the main display stays black and works just second display. How can I solve the issue?

[giorez]

anybody can hel me?
thanks

[mrmazda]

Paste here input/output from inxi -GSIaz. Also attach here or pastebin the file Xorg.0.log. This file should exist in either in /var/log/ or ~/.local/share/xorg/. If firmware-radeon-graphics is not installed, you need to install it. Firmware-amd-graphics is for newer GPUs than your 5850.