[U-Boot] [RFC PATCH] net: gem: Add support for more PHYs on MDIO bus

[Joe Hershberger]

On Mon, Feb 5, 2018 at 1:17 AM, Michal Simek <michal.simek at xilinx.com> wrote:
> Hi Joe,
>
> On 2.2.2018 20:35, Joe Hershberger wrote:
>> Hi Michal,
>>
>> On Thu, Feb 1, 2018 at 6:42 AM, Michal Simek <michal.simek at xilinx.com> wrote:
>>> Find out MDIO bus and enable MDIO access to it if this is done via
>>> different controller.
>>>
>>> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
>>> ---
>>>
>>> Hi Joe,
>>>
>>> this is the code I have hacked a year ago for ZynqMP where we can have
>>> configuration that 4 gems are enabled but they share the same MDIO bus
>>> which can be assigned to only gem. Normally recommendation is that you
>>> should assign it to IP which is required for boot and this is suitable I
>>> would say for almost everybody.
>>> But for testing purpose it will be good to support sharing mdio bus
>>> between others IPs. This hack is "enabling" this for others gem but not
>>> across different ethernet drivers.
>>
>> Seems practical.
>>
>>> And my question is if there is any solution which can be used now for
>>> handling it. Or even this should work even now but we do something
>>> wrong.
>>
>> I would envision some DM way to model the NIC, the MDIO bus, and the
>> PHY separately. The big roadblock is that the DTS format is different
>> for every NIC.
>
> Is it really that different? There should be phy handle which is
> pointing to actual phy and that should be enough to recognize parents
> and IP responsible for MDIO bus.

The point is different drivers express the relationship with varying
levels of implication, so there are a number of ways people describe
it.

>>> I am refreshing this topic based on communication with Tomasz
>>> Gorochowik when he wanted to separate mdio part but it is not compatible
>>> with solution used in Linux which is pattern we should follow.
>>
>> We do the same thing on our 7020 products.
>
> What exactly are you doing on 7020?

We are using a single MDIO interface to connect the PHYs for 2 GEMs.

-Joe