Subject: Re: [PATCH] Add MPC837xEMDS PCIE RC mode support

From: Scott Wood <[email-masked]>
Date: Fri, 30 Nov 2007 09:19:28 -0600

On Fri, Nov 30, 2007 at 08:57:33AM -0600, Kumar Gala wrote:
> On Nov 30, 2007, at 3:37 AM, Li Li wrote:
> > If do it standard, a 256M config space, at least 256M mem space and  
> > 16M
> > io space are needed for each PCIE controller.
> > To allocate PCIE window, the window size only can be 512M or 1G.
> > If we choose 1G space, two PCIE controller needs 2G space.
> > We do not have 2G free physical space now. Usually, we use upper 128M
> > configure space. So, we have to cut down the config space.

That decision should be made in the kernel, not the dts.

> Is it possible to make the outbound window for cfg space 4k and change  
> the region of config space its looking at?

Yes, that'd be best.

> > Here is a little complex. The MPC837xE board needs a carrier board to
> > extend PCIE slot. If user does not populate carrier board onto MPC837xE
> > board and do PCIE scan, the system will halt. I just want to provide a
> > easy way to disable the PCIe other than modify and recompile the dts.
> 
> So I have to recompile the kernel for this case, that seems even more  
> painful to the user.  Can we not detect if this board isn't there and  
> not hang?

Assuming it's similar to PCI on other 83xxMDS, yes -- there's a bit in the
reset control words that can be checked.

We don't currently do it on any 83xx that I'm aware of, though. :-P

-Scott