Subject: Re: pci in arch/powerpc vs arch/ppc

From: Scott Wood <[email-masked]>
Date: Wed, 08 Aug 2007 14:11:28 -0500

Alexandros Kostopoulos wrote:
> I've noticed the following: In function pci_process_bridge_OF_ranges, 
> when  parsing the ranges for MEM and I/O space, the res->start for mem 
> is  correctly set to ranges[na+2], which is the cpu address in the 
> ranges  property. However, in I/O related code, res->start is set to 
> ranges[2],  which is in the PCI address field of the ranges property 
> (and in my case  is 0, as is also for the mpc8272ads case as well). 
> Thus, the res->start of  the I/O of the bridge is 0, which leads to the 
> first device with I/O space  (a davicom ethernet device) been also 
> assigned a I/O region starting at 0.  Finally, the dmfe (davicom 
> ethernet driver over PCI) fails with "dmfe: I/O  base is zero". So, is 
> the implementation of pci_process_bridge_OF_ranges  correct ? shouldn't 
> res->start = ranges[na+2] for I/O as well?

Ideally, yes -- but currently IO-space resources are relative to the 
start of the primary bus's IO-space.

As a workaround, try not setting the primary flag when calling 
pci_process_bridge_OF_ranges.  Note that this means that any legacy I/O 
ports that may exist on cards you plug in (such as VGA cards) will not 
be found.

The proper solution is probably to refuse pre-existing BARs that are 
lower than PCIBIOS_MIN_IO, and/or provide a flag to tell the PCI layer 
to completely ignore pre-existing BARs.

-Scott