[PATCH 2/2] powerpc/mpc5121: add initial support for PDM360NG board

[Grant Likely]

On Wed, May 19, 2010 at 3:37 PM, Scott Wood <scottwood at freescale.com> wrote:
> On 05/19/2010 04:27 PM, Grant Likely wrote:
>>
>> On Mon, May 3, 2010 at 10:34 AM, Scott Wood<scottwood at freescale.com>
>>  wrote:
>>>
>>> Grant Likely wrote:
>>>>>
>>>>> +               // IPIC
>>>>> +               // interrupts cell =<intr #, sense>
>>>>> +               // sense values match linux IORESOURCE_IRQ_* defines:
>>>>> +               // sense == 8: Level, low assertion
>>>>> +               // sense == 2: Edge, high-to-low change
>>>>> +               //
>>>>> +               ipic: interrupt-controller at c00 {
>>>>> +                       compatible = "fsl,mpc5121-ipic", "fsl,ipic";
>>>>> +                       interrupt-controller;
>>>>> +                       #address-cells =<0>;
>>>>
>>>> Don't need #address-cells here
>>>
>>> #address-cells is required by ePAPR for interrupt controllers if an
>>> interrupt-map is used.
>>
>> Why?
>>
>> /me is too lazy to dig out ePAPR and look.
>
> Address cells are part of the interrupt identification.  Typically with
> interrupt maps this is only used on the child end (e.g. to select a
> particular PCI slot), but if the parent interrupt controller's address cells
> are non-zero it will be expected in the parent interrupt specifier as well.
>
> I believe the only part of this that is new with ePAPR is that it asks that
> the interrupt controller address cells be explicitly specified, as it's a
> bit icky for it to default to 2 in some contexts and 0 in others.

Hmmm.  I've not seen that before.  On the 5200 the value of
#address-cells for interrupt controllers has apparently defaulted to
<0> so I've never encountered or thought about it.  I'm not even sure
what #address-cells != 0 would mean in the context of interrupt
mapping, or where it would be relevant.

g.