ARM PCI controller registration and representation using device tree?

[linux@arm.linux.org.uk (Russell King - ARM Linux)]

On Sun, Jun 03, 2012 at 02:41:52AM +0000, Arnd Bergmann wrote:
> On Saturday 02 June 2012, Russell King - ARM Linux wrote:
> > I think we have to keep the existing strategy of having struct hw_pci and
> > its pci_sys_data, registering each bus separately with its own individual
> > swizzle and map_irq functions depending on how the bus hardware is setup.
> 
> Actually, I think we won't need to call pci_fixup_irqs for DT at all, so
> there won't be host specific swizzle and map_irq functions. AFAICT the
> interrupt-map property can handle all possible cases, it certainly does
> so for a large number of obscure buses on powerpc.

That means you have to list every PCI device in DT along with its
interrupt number - which means your boot loader will have to scan the
PCI bus and provide interrupt and BAR settings into the kernel.

And that will suck if you have something like a 4 port PCI network card
which has a PCI-to-PCI bridge on - are boot loaders going to have the
correct swizzling support?  I think not.