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

From: Arnd Bergmann <arnd@arndb.de>
To: Boqun Feng <boqun.feng@gmail.com>
Cc: Bjorn Helgaas <helgaas@kernel.org>,
	Bjorn Helgaas <bhelgaas@google.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Linux on Hyper-V List <linux-hyperv@vger.kernel.org>,
	linux-pci <linux-pci@vger.kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	"K. Y. Srinivasan" <kys@microsoft.com>,
	Haiyang Zhang <haiyangz@microsoft.com>,
	Stephen Hemminger <sthemmin@microsoft.com>,
	Wei Liu <wei.liu@kernel.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Rob Herring <robh@kernel.org>, Clint Sbisa <csbisa@amazon.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	Sunil Muthuswamy <sunilmut@microsoft.com>,
	Marc Zyngier <maz@kernel.org>
Subject: Re: [RFC 1/2] arm64: PCI: Allow use arch-specific pci sysdata
Date: Mon, 29 Mar 2021 16:43:13 +0200	[thread overview]
Message-ID: <CAK8P3a3rgu-zU=Ef_Dnmm-kB2rjb4JfRhvCmnLTH6R_ZZ6kHSQ@mail.gmail.com> (raw)
In-Reply-To: <YGHlA2pXHgyu13T0@boqun-archlinux>

On Mon, Mar 29, 2021 at 4:32 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> Hi Arnd,
>
> On Sat, Mar 20, 2021 at 05:09:10PM +0100, Arnd Bergmann wrote:
> > On Sat, Mar 20, 2021 at 1:54 PM Arnd Bergmann <arnd@arndb.de> wrote:
> > >      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