Who is stomping PCI config space?

[Benjamin Herrenschmidt]

On Thu, 2005-03-03 at 14:03 -0500, Jon Smirl wrote:
> I have two video cards:
> PCI Rage128
> AGP Radeon
> 
> X is loaded on the Rage128 on VT7
> X is not configured to support the radeon
> 
> I switch to VT1 and load radeonfb
> This works fine.
> 
> Now I switch to VT7 and dump PCI config space for the radeon
> 
> [root at jonsmirl 0000:01:00.0]# hexdump config >/foo
> [root at jonsmirl 0000:01:00.0]# diff /foo /bar
> 1c1
> < 0000000 1002 4966 0080 02b0 0001 0300 4010 0080
> ---
> > 0000000 1002 4966 0083 02b0 0001 0300 4010 0080
> 4c4
> < 0000030 0000 fea0 0058 0000 0000 0000 010b 0008
> ---
> > 0000030 0000 fe90 0058 0000 0000 0000 010b 0008
> [root at jonsmirl 0000:01:00.0]#
> 
> Somebody is changing PCI command from 83 to 80 and disabling my
> radeon's memory and iospace. Who is doing this? It has to be X since
> it doesn't happen if I switch to VT6 or VT8.
> 
> Why is X mucking with a card it doesn't have a driver loaded for? 
> Where is this happening in the X code?

I had a report of something similar with X and a mach64 ... I haven't
yet investigated, but basically, X is using "fbdev" (so no specific
driver) and seem to be disabling memory access to the card, thus blowing
up the kernel fbdev.

Ben.