cns3xxx PCIe domain support

[Lorenzo Pieralisi]

On Sun, Jan 03, 2021 at 11:47:45PM +0100, Arnd Bergmann wrote:
> I'm working on a patch series to simplify the ARM pci-common
> implementation and came across cns3xxx, which unlike the other
> non-DT platforms does not partition the bus space of PCI domain
> zero but instead uses the default bus range 0...255 for each
> host bridge without assigning domain numbers.
> 
> Before linux-3.20, commitm c88d54ba0c3d ("CNS3xxx: Remove
> artificial dependency on pci_sys_data domain."), it used to
> assign a domain number, but since then, the pci-common code
> just supports a single domain.
> 
> My question is: does this actually work correctly without
> leading to duplicate domain/bus/device/function tuples?
> Is there anything I'm missing in the code, or could it be
> that the machines that Koen and Krzysztof were running
> on never used more than one of the host bridges?

Hi Arnd,

Happy New Year !! I don't think there is anything you are missing, I
think that's an issue. A possible solution would consist in selecting
PCI_DOMAINS_GENERIC (the OF code should fall back to using a counter for
PCI domains - which should do the trick), I'd rather avoid adding back
an arch/arm hook to set-up the domain number

Please let me know how we can handle this, thanks a lot for spotting
it.

Lorenzo