Re: [RFC 1/2] arm64: PCI: Allow use arch-specific pci sysdata

On Mon, Mar 29, 2021 at 4:32 PM Boqun Feng [off-list ref] wrote:

Hi Arnd,

On Sat, Mar 20, 2021 at 05:09:10PM +0100, Arnd Bergmann wrote:

quoted

On Sat, Mar 20, 2021 at 1:54 PM Arnd Bergmann [off-list ref] wrote:

quoted

     I actually still have a (not really tested) patch series to clean up
the pci host bridge registration, and this should make this a lot easier
to add on top.

I should dig that out of my backlog and post for review.

I've uploaded my series to
https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git
pci-probe-rework-20210320

The purpose of this series is mostly to simplify what variations of
host probe methods exist, towards using pci_host_probe() as the
only method. It does provide some simplifications based on that
that, including a way to universally have access to the pci_host_bridge
pointer during the probe function.

Thanks for the suggestion and code. I spend some time to catch up. Yes,
Bjorn and you are correct, the better way is having a 'domain_nr' in the
'pci_host_bridge' and making sure every driver fill that correctly
before probe. I definitly will use this approach.

However, I may start small: I plan to introduce 'domain_nr' and only
fill the field at probe time for PCI_DOMAINS_GENERIC=y archs, and leave
other archs and driver alone. (honestly, I was shocked by the number of
pci_scan_root_bus_bridge() and pci_host_probe() that I need to adjust if
I really want to unify the 'domain_nr' handling for every arch and
driver ;-)). This will fulfil my requirement for Hyper-V PCI controller
on ARM64. And later on, we can switch each arch to this approach one by
one and keep the rest still working.

Thoughts?

That sounds reasonable to me, yes. I would also suggest you look
at my hyperv patch from the branch I mentioned [1] and try to integrate
that first. I suspect this makes it easier to do the domain rework and
possibly other changes on top.

       Arnd

https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/commit/?h=pci-probe-rework-20210320&id=44db8df9d729d

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