Subject: Re: [PATCH v2 5/7] powerpc/corenet: Add MDIO bus muxing support to the board device tree(s)

From: Emil Medve <[email-masked]>
Date: Thu, 31 Jul 2014 00:48:03 -0500

Hello Scott,

On 07/31/2014 12:28 AM, Scott Wood wrote:
> On Wed, 2014-07-30 at 23:35 -0500, Emil Medve wrote:
>> Hello Scott,
>>
>>
>> On 07/30/2014 09:30 PM, Scott Wood wrote:
>>> On Wed, 2014-07-30 at 16:52 -0500, Emil Medve wrote:
>>>>>>>> +			mdio0: mdio <at> fc000 {
>>>>>>>> +			};
>>>>>>>
>>>>>>> Why is the empty node needed?
>>>>>>
>>>>>> For the label
>>>>>
>>>>> For mdio-parent-bus, or is there some other dts layer that makes this
>>>>> node non-empty?
>>>>
>>>> 'powerpc/corenet: Create the dts components for the DPAA FMan' -
>>>> http://patchwork.ozlabs.org/patch/370872
>>>
>>> Why does this patch define the mdio0 label for mdio@e1120, but not
>>> define a label for any other node?
>>
>> Only MDIO controllers that are pinned out have these labels. Only pinned
>> out MDIO(s) are capable of controlling external PHY(s) via these board
>> level MDIO buses
> 
> Is there any reason to describe non-pinned-out MDIO controllers at all?

Yes. For the internal TBI PHY(s). Each MAC supporting SGMII has a TBI
PHY that is attached to the MDIO controller of the respective MAC

> Is the lack of pinning out inherent to the silicon, or is it board
> design/config?

It's a silicon level decision

> Is the answer different for different MDIO controllers?

You mean non-FSL MDIO controllers? Dunno. All FSL SoC have the same MDIO
pin-out decision

> I'm just curious why mdio@e1120 is labelled in a non-board dtsi while
> others are labelled elsewhere.

Labels are relevant only in the context of 'powerpc/corenet: Add MDIO
bus muxing support to the board device tree(s)' -
http://patchwork.ozlabs.org/patch/370866. Most labels are created and
used in the board .dts file except b4qds.dtsi which is shared between
b4420qds.dts and b4860qds.dts

Cheers,