Radeon trouble Jessie 8.3. [drm:radeon_pci_probe] *ERROR* with firmware-linux-nonfree installed

[Trond Arild Ydersbond]

I have got this working on the same machine with Wheezy 7.6 and Knoppixes up to 
and including 7.6.1, but it seems that radeon_pci_probe refuses to recognize 
the installed firmware. Have tried different settings, but dmesg stille gives 
the same error.
*ERROR* radeon kernel modesetting for R600 or later requires 
firmware-linux-nonfree

What can I do about this?

Trond