[PATCH 6/8] arm: mach-armada: add support for Armada XP board with device tree

On 05/15/2012 08:37 AM, Arnd Bergmann wrote:

On Tuesday 15 May 2012, Ben Dooks wrote:

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  * Maybe those mappings can be done using a normal ioremap() rather
    than in ->map_io(), according to DT informations (but most other ARM
    SoC support at the moment seem to do PCI mappings using static
    mappings in ->map_io)

That's a very old way of doing it. I'm pretty sure there's no reason to
get these allocated so early.

Well, you might actually still want to use static mappings for any large
areas that are accessed a lot in the kernel, because that lets you
use larger page TLB entries, which ioremap by itself cannot. The host
driver should however still use ioremap, it will now just get the area
that was set up with map_io.

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I believe you can probably leave the PCI/PCIe bindings until you have
enough kernel state to do ioremap() or similar and then associate the
necessary mappings with the bus creation.

I think it was Stephen Warrent who told me that he can actually do
a PCI host driver as a loadable module now, with only a few changes
in the ARM core code.

Thierry Redding was working on this (actually, perhaps PCIe as a
platform driver rather than as a module, but I'm not sure) in the
context of the Tegra PCIe driver. See some of the patches at
http://patchwork.ozlabs.org/project/linux-tegra/list/, e.g. "PCI: Keep
pci_fixup_irqs() around after init" and "ARM: pci: Keep
pci_common_init() around after init" IIRC.