linux-kernel - Re: [PATCH 10/14] PCI: tegra: Move PCIe driver to drivers/pci/host

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Date:	Thu, 17 Jan 2013 15:42:36 +0000
From:	Andrew Murray <andrew.murray@....com>
To:	Thierry Reding <thierry.reding@...onic-design.de>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Stephen Warren <swarren@...dotorg.org>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	Grant Likely <grant.likely@...retlab.ca>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Russell King <linux@....linux.org.uk>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>,
	"devicetree-discuss@...ts.ozlabs.org" 
	<devicetree-discuss@...ts.ozlabs.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>
Subject: Re: [PATCH 10/14] PCI: tegra: Move PCIe driver to drivers/pci/host

On Wed, Jan 16, 2013 at 06:31:01PM +0000, Thierry Reding wrote:
> Alright, putting the functions into pci_ops doesn't sound like a very
> good idea then. Or perhaps it would make sense for hardware where the
> root complex and the MSI controller are handled by the same driver.
> Basically it could be done as a shortcut and if those are not filled
> in, the drivers could still opt to look up an MSI controller from a
> phandle specified in DT.
> 
> Even another alternative would be to keep the functions within the
> struct pci_ops and use generic ones if an external MSI controller is
> used. Just tossing around ideas.

I think an ideal solution would be for additional logic in drivers/msi.c
(e.g. in functions like msi_capability_init) to determine (based on the
passed in pci_dev) which MSI controller ops to use. I'm not sure the best
way to implement an association between an MSI controller and PCI busses
(I believe arch/sparc does something like this - perhaps there will be
inspiration there).

As you've pointed out, most RCs will have their own MSI controllers - so
it should be easy to register and associate both together.

I've submitted my previous work on MSI controller registration, but it
doesn't quite solve this problem - perhaps it can be a starting point?

Andrew Murray

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