Subject: Re: pci and pcie device-tree binding - range No cells

From: Mitch Bradley <[email-masked]>
Date: Mon, 10 Dec 2012 13:11:38 -1000

On 12/10/2012 12:38 PM, Benjamin Herrenschmidt wrote:
> On Mon, 2012-12-10 at 21:43 +0000, Grant Likely wrote:
>>> Sorry for my pci ignorance (have never got hw for mb/zynq)
>>> I just want to get better overview how we should we our drivers to
>> be compatible.
>>>
>>> Does it mean that pci is supposed be always 64 bit wide?
>>> And there is no option to have just 32bit values.
>>
>> Yes, PCIe addressing is always 64 bits wide. Even on 32bit PCI systems
>> we use 64 bit PCI addressing in the device tree.
> 
> Right. The size & format of an address cell for PCI is specified in the
> OF PCI bindings and we follow that binding. It's always 3 cells.

.. and the reason why it must be 3 cells, even if the host PCI bus only
supports 32-bit addressing, is because a plug-in PCI card has no way of
knowing what the host supports.

> 
> Cheers,
> Ben.
> 
> 
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