Dear Ben,

Thank you for your answer.

On 09 July 2015 at 09:53 AM, Benjamin Herrenschmidt wrote:
>
> Michael, the crash looks like a neat NULL dereference, any chance you
> can spot something in the code that might explain it ?
>
> The strange thing is that the crash is in sb600_8259_cascade(), however
> that function doesn't seem to exist in a current kernel tree, or if it
> does it's somewhat hidden behind grep-defeating macros.
>
> All I can find that relates to something called "sb600" is some quirks
> in AHCI and x86 fixups that seem ATI related.
>
> Christian, do you have some out of tree driver in that kernel ?
Yes I have. Our PA6T system uses the AMD/ATI SB600 South Bridge to 
provide various integrated I/O functions including SATA/PATA ports, USB 
and audio. The SB600 connects to the PA6T CPU via a PCIe x4 link. This 
is termed an “A-link II Express” link by ATI/AMD.

I/O features:

- PCIe x4 link to CPU
- SATA-II AHCI controller with 4 ports
- PATA (IDE) controller (single channel)
- multiple USB ports (5 OHCI and 1 EHCI host controllers and all ports 
are fully USB 1.1 and USB 2.0 compliant)
- UAA compatible HD Audio controller
- PCIe-PCI bridge supporting multiple PCI slots with 5V signalling support
- 8259 compatible interrupt controller
- Real Time Clock

I have to patch the official kernel source code because of the SB600 
South Bridge.

I have added the patch for the kernel 4.1 as an email attachment.

I would like to thank you very much in advance for helping me. If you 
have any further questions, please do not hesitate to ask. I am looking 
forward to getting your reply.

Rgds,

Christian