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

[Joe Hershberger]

On Wed, Feb 7, 2018 at 1:46 AM, Michal Simek <michal.simek at xilinx.com> wrote:
> On 6.2.2018 22:11, Joe Hershberger wrote:
>> 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.
>
> ok.
>
>>
>>>>> 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.
>
> And I expect you are using only one interface for boot right?

That's right. Currently we only have one defined in U-Boot, but of
course use both from Linux.

-Joe