linux-kernel - Re: [PATCH] pci: Add support for creating a generic host

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Message-ID: <CACoXjc=epN8=tFQKw6kZ27hTA=a+c56q1pikX_SSMKK1rsScCw@mail.gmail.com>
Date:	Thu, 13 Feb 2014 00:36:44 -0800
From:	Tanmay Inamdar <tinamdar@....com>
To:	Jingoo Han <jg1.han@...sung.com>
Cc:	Liviu Dudau <Liviu.Dudau@....com>, Arnd Bergmann <arnd@...db.de>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	LKML <linux-kernel@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] pci: Add support for creating a generic host_bridge from
 device tree

On Thu, Feb 13, 2014 at 12:10 AM, Jingoo Han <jg1.han@...sung.com> wrote:
> On Thursday, February 06, 2014 7:18 PM, Liviu Dudau wrote:
>> On Wed, Feb 05, 2014 at 10:26:27PM +0000, Tanmay Inamdar wrote:
>> > Hello Liviu,
>> >
>> > I did not get the first email of this particular patch on any of
>> > subscribed mailing lists (don't know why), hence replying here.
>>
>> Strange, it shows in the MARC and GMANE archive for linux-pci, probably
>> a hickup on your receiving side?
>>
>> >
>> > +struct pci_host_bridge *
>> > +pci_host_bridge_of_init(struct device *parent, int busno, struct pci_ops *ops,
>> > + void *host_data, struct list_head *resources)
>> > +{
>> > + struct pci_bus *root_bus;
>> > + struct pci_host_bridge *bridge;
>> > +
>> > + /* first parse the host bridge bus ranges */
>> > + if (pci_host_bridge_of_get_ranges(parent->of_node, resources))
>> > + return NULL;
>> > +
>> > + /* then create the root bus */
>> > + root_bus = pci_create_root_bus(parent, busno, ops, host_data, resources);
>> > + if (!root_bus)
>> > + return NULL;
>> > +
>> > + bridge = to_pci_host_bridge(root_bus->bridge);
>> > +
>> > + return bridge;
>> > +}
>> >
>> > You are keeping the domain_nr inside pci_host_bridge structure. In
>> > above API, domain_nr is required in 'pci_find_bus' function called
>> > from 'pci_create_root_bus'. Since the bridge is allocated after
>> > creating root bus, 'pci_find_bus' always gets domain_nr as 0. This
>> > will cause problem for scanning multiple domains.
>>
>> Good catch. I was switching between creating a pci_controller in arch/arm64 and
>> adding the needed bits in pci_host_bridge. After internal review I've decided to
>> add the domain_nr to pci_host_bridge, but forgot to update the code everywhere.
>
> Hi Liviu Dudau,
>
> One more thing,
> I am reviewing and compiling your patch.
> Would you consider adding 'struct pci_sys_data' and 'struct hw_pci'?
>
> Currently, 4 PCIe Host drivers (pci-mvebu.c, pci-tegra.c,
> pci-rcar-gen2.c, pcie-designware.c) are using 'struct pci_sys_data'
> and 'struct hw_pci' in their drivers. Without this, it makes build
> errors.
>
> In arm32, 'struct pci_sys_data' and 'struct hw_pci' is defined
> in "arch/arm/include/asm/mach/pci.h".
>
> Tanmay Inamdar,
> Your 'APM X-Gene PCIe' patch also needs 'struct pci_sys_data' and
> 'struct hw_pci'. With Liviu Dudau's patch, it will make build
> errors. Would you check this?

X-Gene PCIe host driver is dependent on arm64 PCI patch. My previous
approach was based on 32bit arm PCI support. With Liviu's approach, I
will have to make changes in host driver to get rid of hw_pci and
pci_sys_data which are no longer required.

IMO it should not cause build errors for PCI host drivers dependent on
architectures other than arm64. Can you post the error?

>
> Thank you.
>
> Best regards,
> Jingoo Han
>
>>
>> Thanks for reviewing this, will fix in v2.
>>
>> Do you find porting to the new API straight forward?
>>
>
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