Radeon 9000 Pro corruption problem on PPC when DRI is enabled

[Benjamin Herrenschmidt]

> If I understand that correctly, the driver can't use _anything_ it reads
> from the bios (clock info, connector info,...)? A true wonder it almost
> works then I guess with all those bogus values...

Yes, it looks like it read random data from the OF ROM. It would be good
to figure out why 6.8.2 properly detected that no VBIOS was available
while 7.x fails... we should definitely at least test the BIOS header
type I suppose... And some sanity checking on the values read would do
no harm.

> It looks like adding a check for the bios type is the right thing to do.
> I'd hope it's not possible that it might fail wrongly on some cards?

I think that if the BIOS type in the header is wrong, x86 won't even
boot it, though that might indeed not be the case with laptops where the
gfx BIOS is mangled with the main BIOS image and what you get is the
memory copy from c0000... I don't know. We should try to see what
changed since 6.8.2 and what is the commit message justifying the
change. Also, some sanity checking of the values would probably catch
bogus ones in 99% of the cases. 

Ben.