Integrator PCI base dilemma

Arnd Bergmann arnd at
Fri Mar 22 08:34:59 EDT 2013

On Friday 22 March 2013, Russell King - ARM Linux wrote:
> > Also, in many cases, you don't even have the choice in the kernel between
> > the two options, either PCI is identity mapped or mapped starting at
> > address zero based on whatever the soc or board designer thought, and the
> > only thing we can do is tell the kernel what the hardware does.
> Exactly which is why you're wrong. :)  If the hardware enforces a
> separation of the physical address space from the PCI address space
> by way of an offset translation, then you have no option but to have
> a non-zero mem_offset.

I still think we are in complete agreement about the facts here, at least
I was trying to say the same thing above that you replied with.

> > It looks like cns3xxx, tegra, versatile and ks8695 are all hardwired to a
> > zero mem_offset, while dc21285, integrator, it8152 and sa1100/pci-nanoengine
> > map the PCI bus starting at bus address 0.
> Don't read too much into the versatile stuff.  All that is very very much
> untested and fragile.  It's fairly buggered at the moment as it stands,
> and as far as I can tell there's absolutely no way to know what the right
> solution is - because the ARM documentation is extremely poor and all the
> real hardware has been stuffed through the mincer.
> So that leaves cns3xxx, tegra and ks8695 being the non-plat ones which
> are "different" from the majority on ARM.

Well, those and all the ones that chose to set up their windows in the
same way like the plat-orion based ones.


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