On 03/08/2013 01:14 AM, Thierry Reding wrote:
> On Thu, Mar 07, 2013 at 06:05:33PM -0600, Rob Herring wrote:
>> On 03/07/2013 02:47 PM, Thierry Reding wrote:
> [...]
>>> In a nutshell (since some of the context isn't quoted anymore) the
>>> problem that we're trying to solve is that some of the embedded SoCs
>>> require per-root-port registers for configuration. The PCI DT
>>> specification doesn't make any provisions for this. A few alternatives
>>> have been discussed so far:
>>
>> I'm not sure I follow. This is different than the host controller
>> registers? Why would this not just be multiple entries in the reg property?
>
> Well the register regions are per root-port. On Tegra20 there's 2 of
> them, Tegra30 has 3 and if I understand correctly Marvell can have up to
> 10 (!). Adding all of them to the reg property of the host controller
> could work but it needs some way to match the reg entry to the root port
> similar to option 1 below.
The compatible property of the PCI host controller can imply what each
index of the reg property entries is for.
>
> Adding a property in the root port nodes seems like a cleaner and more
> accurate representation of the hardware to me, but if that's not
> acceptable perhaps we need to bite the bullet and add the code to look
> the registers up from the parent's reg property.
What I don't like is a new property defined to describe mmio addresses.
We already have a property for that and it is "reg". But I think I'm
still missing something:
>>> pci@0,1 {
>>> ...
>>> reg = <0x00000800 0 0 0 0>;
Is this a PCI bus address?
>>> regs = <0x80000000 0x00001000>;
>>> };
Rob
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