Re: FPGA access over PCI-E on MPC8536

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> > However when I attempt to access FPGA memory my mmapping it in  
> > userspace the read hangs. The same happens in kernel space. Does it  
> > happen because FPGA memory is marked as disabled, or because FPGA  
> > code is doing something wrong ?
> 
> Can you access the device in u-boot?  That would possible tell you if  
> the HW is functioning or not.
> 
> > Another question is what can cause PCI device memory be marked as
> > disabled.
> 
> Good question, no idea how lspci decided to print [disabled].  Take a  
> look at lspci source and see :)

Maybe the memory enable in the PCI command register isn't set ?

If you don't have a kernel driver that sets it (by calling
pci_enable_device) and u-boot doesn't set it then it's going
to be off and you'll get hangs or machine checks trying to
access the device...

Just an idea...

Cheers,
Ben.