linux-kernel - Re: [RFC 2/4] PCI: generic: Add support for ARM64 and MSI(x)

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Message-ID: <54A6E0DE.6090309@amd.com>
Date:	Fri, 2 Jan 2015 12:18:06 -0600
From:	Suravee Suthikulanit <suravee.suthikulpanit@....com>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>
CC:	Arnd Bergmann <arnd@...db.de>, Liviu Dudau <Liviu.Dudau@....com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Mark Rutland <Mark.Rutland@....com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"jason@...edaemon.net" <jason@...edaemon.net>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Marc Zyngier <Marc.Zyngier@....com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Will Deacon <Will.Deacon@....com>,
	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"Catalin Marinas" <Catalin.Marinas@....com>,
	"bhelgaas@...gle.com" <bhelgaas@...gle.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>
Subject: Re: [RFC 2/4] PCI: generic: Add support for ARM64 and MSI(x)

On 1/2/2015 5:55 AM, Lorenzo Pieralisi wrote:
> Hi Suravee,
>
> On Mon, Dec 29, 2014 at 07:32:44PM +0000, Suravee Suthikulpanit wrote:
>> >Hi,
>> >
>> >I am not sure if this thread is still alive. I'm trying to see what I
>> >can do to help clean up/convert to make the PCI GHC also works for arm64
>> >w/ zero or minimal ifdefs.
>> >
>> >Please let me know if someone is already working on this. I noticed that
>> >Lorenzo's patches has already been in 3.19-rc1, and in Bjorn's
>> >pci/domain branch. Otherwise, I'll try to continue the work based on the
>> >sample patch from Arnd here.
> If I am not mistaken, the only bit missing to remove pci_sys_data (and so
> having a generic host controller driver that works on ARM32/64) is generic
> MSI management.

Lorenzo,

Do you mean to remove pci_sys_data from pci-host-generic.c or removing 
it completely? I assume the former case.

So, looking at the current code in the pci-host-generic.c, my 
understanding is that the:
     *gen_pci = pci_bus->sysdata->private_data
will be changed to:
     *gen_pci = pci_bus->sysdata

Then, we can simply just call pci_scan_root_bus() directly since we no 
longer need to declare hw_pci for calling pci_common_init_dev().

> I know for certain Marc is working on it, and the solution is WIP,
> I think we should prevent adding more churn to pci_sys_data, since
> I managed to remove most of the dependencies (domain, mem_offset).

Thanks for cleaning up the domain and mem_offset.

I saw Marc's irq/msi_domain patch series 
(http://git.kernel.org/cgit/linux/kernel/git/maz/arm-platforms.git/log/?h=irq/msi_domain). 

My understanding is that deals with associating the newly introduced 
msi_domain to each device, which replaces the need for pci_bus->msi and 
hw_pci->msi_ctrl when configure with CONFIG_PCI_MSI_IRQ_DOMAIN (not sure 
if this would be the plan for all arm32).  For ARM32, if not define 
CONFIG_PCI_MSI_IRQ_DOMAIN, it would still fall back to using the 
[pci_sys_data|hw_pci]->msi_ctrl.

However, I noticed that the hw_pci->msi_controller is not even used for 
the pci-host-generic. So, this should not be blocking the work to free 
pci-host-generic from pci_sys_data and hw_pci, as the MSI stuff can go 
in separately. Am I missing something?

> So to sum it up, to have a generic host controller driver for ARM32/64
> we just need to work out how to handle the MSI data, patches will be
> on the lists shortly to handle that, please review.
>
> Thanks,
> Lorenzo
>

Thanks for the update and the summary. I'll help review/test the MSI 
patch once posted.

Thanks,

Suravee

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