linux-kernel - Re: [PATCH v3] pcie: Add Xilinx PCIe Host Bridge IP driver

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Message-ID: <87d2fpoct3.fsf@approximate.cambridge.arm.com>
Date:	Wed, 07 May 2014 15:58:48 +0100
From:	Marc Zyngier <marc.zyngier@....com>
To:	Will Deacon <will.deacon@....com>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Srikanth Thokala <sthokal@...inx.com>,
	"linux-arm-kernel\@lists.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Michal Simek <michal.simek@...inx.com>,
	"grant.likely\@linaro.org" <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree\@vger.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pci\@vger.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@...r.kernel.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
Subject: Re: [PATCH v3] pcie: Add Xilinx PCIe Host Bridge IP driver

On Wed, May 07 2014 at  3:53:27 pm BST, Will Deacon <will.deacon@....com> wrote:
> Hi all,
>
> Thanks for CC'ing me, Arnd.
>
> On Wed, May 07, 2014 at 03:35:48PM +0100, Arnd Bergmann wrote:
>> On Wednesday 07 May 2014 17:21:13 Srikanth Thokala wrote:
>> > On Wed, Apr 30, 2014 at 9:04 PM, Arnd Bergmann <arnd@...db.de> wrote:
>> > > Would it be possible to split the config space access out into
>> > > a separate file? It would be nice to share that with the generic
>> > > ECAM driver that Will Deacon has sent.
>> > 
>> > Yes, it should be possible.  Is it ok, if I work on top of this driver?
>> 
>> Do you mean as a follow-on patch? My feeling is that since we are trying
>> to merge both for 3.16, it would be good to get it done right away if
>> it doesn't cause too much extra work.
>
> Do you mean something as simple as a helper for base + offset ECAM
> addressing, or something more involved that handles the mapping as well? The
> latter would need some alignment on sys->private_data, I think.
>
> Srikanth: I'll CC you on the next version of my patches (I'll send them
> now).
>
>> > > As a general comment about the MSI implementation, I wonder if
>> > > this is actually
>> > > generic enough to be shared with other host controllers. It could be moved
>> > > into a separate file like the config space access in that case.
>> > 
>> > I feel the MSI implementation is not generic by looking into the other
>> > host controllers,
>> > it is more specific to the hardware.  Correct me, if am wrong.
>> 
>> The other host controllers are certainly incompatible, but this one looks
>> like it could be used on other controllers easily.
>> 
>> Splitting it out would also make it easier to use another MSI implementation
>> like the one in the GIC.
>
> Actually, MarcZ and I already have my driver working with GICv3 + MSI. The
> code basically amounts to implementing {add,remove}_bus callbacks to set
> the msi_chip for the pci_bus, based on what we got out of the devicetree.
> I don't think we needed anything else... Marc?

No, that's it, really. I use the "msi-parent" property to find the
msi_chip, which should have been registered as a "msi-controller".

	M.
-- 
Jazz is not dead. It just smells funny.
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