A little more progress today.
I noticed that not all init functions for sb800 were called. It seems like they should be be called from: src/northbridge/amd/agesa/family15/northbridge.c because that's where they are called from in f14 code. So I added that and now it seems solve some problems but the SATA softreset problem still remains.
I added "pci=nocrs" to the kernel boot option and the BAR errors aren't there anymore.
I have attached a new diff and logfile of the kernel output.
To me it doesn't seem to be any more obvious errors so I would be really grateful for any help or hints at all.
I have managed to boot from usb sticks with both fedora and ubuntu. They seem to be able to mount the usb stick and boot to desktop. However because I'm stuck with serial and they don't seem to have any serial login I can't confirm or dump lspci etc. But I can see that they respond to the power button event and doesn't seem like they hang or crash.
Does anybody know a dist where serial console login is on by default?