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

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Message-ID: <20140507145327.GB2563@arm.com>
Date:	Wed, 7 May 2014 15:53:27 +0100
From:	Will Deacon <will.deacon@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Srikanth Thokala <sthokal@...inx.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Michal Simek <michal.simek@...inx.com>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	marc.zyngier@....com
Subject: Re: [PATCH v3] pcie: Add Xilinx PCIe Host Bridge IP driver

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?

Will
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