PCI example for device tree

[Stephan Gatzka]

Hi Grant!

> Hi Stephan,
>
> Thanks for this work.  That is useful.  Before I take it out of draft,
> I'd like some changes to be made so that it better fits with the rest
> of the documents.  I talked about it in an earlier email, but I don't
> know if you got it or not.  Here's what I wrote:

No, unfortunately, I haven't read it.

>> - Instead, of using an MPC5200 example, add a pci bus to the sample
>> Coyote's Revenge system used in the rest of the page and describe
>> that.  The goal of this document is to lead a user step-by-step how
>> each part of the device tree works.  So, instead of plopping down the
>> complete PCI bus node, the document should gradually build it up, and
>> talk about each element as it is added.  Focus on how it all works
>> together.

My intention was to describe a working example for a Host-to-PCI bridge. 
Of course it is possible to rework it to your imaginary example but 
again, I definitely prefer to do that for an existing board. Please just 
consider to write something about the interrupt-map property without 
having the schematics and a user manual for the SoC used. I can't 
explain it without the wiring of IDSEL lines and the mapping of IDSEL to 
device numbers in the PCI bridge.

>>
>> - It would be useful to also show a PCI-to-PCI bridge,
OK, but maybe sometimes later.
 >> and maybe a
>> fixed PCI device as children of the host bridge node.

OK, but I think at least for PCI the current policy is just to describe 
the bridge and leave the PCI devices up for PCI probing code. So adding 
a PCI device as a children might be a bit academically.

>
> The most important bit I think it to break up the adding of the PCI
> node so that it is built up piece by piece.  For each element being
> discussed, I want a reader to be able to focus on just the properties
> that are involved.

I have to think about it. My intention was more to explain what needs to 
be done for integrating a HOST-to-PCI bridge in a device tree and to 
describe the properties that are necessary for. There are some 
properties that belong together and I can't easily explain them 
stand-alone. That's the reason why I used colors to display the related 
properties.

I know that my sections breaks with the style you've used in the intro 
document. But I think for this complex PCI thing it is better to have a 
walk-through example.

Kind regards,

Stephan

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