[coreboot] device tree rework (was: Re: [PATCH] use Kconfig for both options on Lippert boards)

Stefan Reinauer stefan.reinauer at coresystems.de
Wed Sep 1 17:03:03 CEST 2010

 Peter Stuge wrote:
> Jens Rottmann wrote:
>>> Maybe make that one option per port instead,
>> I had considered this but decided against it.
> Oh well.
>> It is simply not feasible to make _everything_ configurable,
> I'm not sure I agree about feasible. I agree it's not worthwhile
> though. You know your customers best, but from my experience with
> embedded customers, more configurability is better. :)
It also changes the code from "do the minimal effort for hardware init"
to "parse a lot of different options and make sure all possible
combinations make sense and work".

I'm not saying we shouldn't. I'm just saying it'll be a shift in
principles. (And a lot of effort if done right)

>> you'd have to start with devicetree.cb,
> I know. This is one part of coreboot "infrastructure" that I think
> needs some improvement. A first step would be interrupt routing.
> It might also be nice to make it a little easier to use devicetree.cb
> from the coreboot code.

Now that we have a good grip on the device tree and sconfig is
increasingly stable, we should discuss how to get the routing into our
device tree. Suggestions?

Some brainstorming:
- every device that has an APIC needs to have IRQ routing information.
Every bridge, even?
- what about 8259? Virtual Wire?
- We need to represent the IO apics in the device tree so we can walk
the system for dynamic boot time table creation.
- any of the i945 ports would be an easy initial target, as they have
i945_pci_irqs.asl, ich7_pci_irqs.asl, irq_tables.c and mptable.c in
separate files, so they could be replaced easily by something auto
generated. *.asl could (at least for now) be created from the device
tree at compile time.
- A good first start (and relatively easy, since its only refactoring)
would also be to factor out interrupt routing from the K8/Fam10 boards
into separate files, and move their acpi code to the north/southbridge
like it's done on i945/ich7. Any takers?


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