linux-kernel - Re: [PATCH 00/14] Rewrite Tegra PCIe driver

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Date:	Thu, 10 Jan 2013 09:34:47 +0100
From:	Thomas Petazzoni <thomas.petazzoni@...e-electrons.com>
To:	Thierry Reding <thierry.reding@...onic-design.de>
Cc:	linux-tegra@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	Rob Herring <rob.herring@...xeda.com>,
	Russell King <linux@....linux.org.uk>,
	Stephen Warren <swarren@...dotorg.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Andrew Murray <andrew.murray@....com>,
	Jason Gunthorpe <jgunthorpe@...idianresearch.com>,
	Arnd Bergmann <arnd@...db.de>,
	devicetree-discuss@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-pci@...r.kernel.org
Subject: Re: [PATCH 00/14] Rewrite Tegra PCIe driver

Dear Thierry Reding,

On Thu, 10 Jan 2013 07:55:37 +0100, Thierry Reding wrote:

> The reason is that with the latest bindings the matching of root ports
> to device tree nodes works as-is and nothing else indicates that the
> emulated host bridge is actually required to make any of this work. So
> in order not to introduce unneeded code I've left it out for now. If
> somebody decides that we actually need this host bridge (for standards
> compliance or whatnot) it could easily be added back.

Ok.

> However, before the emulated bridge implementation can be merged I think
> the PCI ID issue needs to be resolved.

Indeed. I am not sure yet how to solve that, though.

> > So, I instantiate one unique emulated Host Bridge, and then one
> > emulated PCI-to-PCI Bridge for each PCIe interface that I have.
> 
> Oh dear, that's even worse than on Tegra. The Marvell hardware doesn't
> even expose the root ports as PCI devices on the bus?

My understanding is that no, it doesn't, but I am still figuring out
many things in this PCIe topic.

> I suppose that in your case it really makes sense because you already
> need the emulated PCI-to-PCI bridges and therefore adding an emulated
> host bridge doesn't add much. As I said, for Tegra everything still
> works without, so I didn't see a reason to add needless code.

Ok, thanks!

Thomas
-- 
Thomas Petazzoni, Free Electrons
Kernel, drivers, real-time and embedded Linux
development, consulting, training and support.
http://free-electrons.com
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