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

From: Boqun Feng <boqun.feng@gmail.com>
To: Arnd Bergmann <arnd@arndb.de>
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 22:32:35 +0800	[thread overview]
Message-ID: <YGHlA2pXHgyu13T0@boqun-archlinux> (raw)
In-Reply-To: <CAK8P3a07wedojBU6xDKotiOsPR8k2XEXMB1SvJSRpeG++URA5Q@mail.gmail.com>

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?

Regards,
Boqun

>          Arnd

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