linux-kernel - Re: [PATCH net-next 1/3] net: phy: Add binding for vendor specific C45 MDIO address space

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Date:   Tue, 17 Apr 2018 11:29:27 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     vicentiu.galanopulo@....com, robh@...nel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        mark.rutland@....com, davem@...emloft.net, marcel@...tmann.org,
        devicetree@...r.kernel.org, alexandru.marginean@....com,
        madalin.bucur@....com
Subject: Re: [PATCH net-next 1/3] net: phy: Add binding for vendor specific
 C45 MDIO address space

On 04/17/2018 11:27 AM, Andrew Lunn wrote:
> On Tue, Apr 17, 2018 at 11:18:20AM -0700, Florian Fainelli wrote:
>> On 04/17/2018 02:02 AM, Vicentiu Galanopulo wrote:
>>> The extra property enables the discovery on the MDIO bus
>>> of the PHYs which have a vendor specific address space
>>> for accessing the C45 MDIO registers.
>>>
>>> Signed-off-by: Vicentiu Galanopulo <vicentiu.galanopulo@....com>
>>> ---
>>>  Documentation/devicetree/bindings/net/phy.txt | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>> diff --git a/Documentation/devicetree/bindings/net/phy.txt b/Documentation/devicetree/bindings/net/phy.txt
>>> index d2169a5..82692e2 100644
>>> --- a/Documentation/devicetree/bindings/net/phy.txt
>>> +++ b/Documentation/devicetree/bindings/net/phy.txt
>>> @@ -61,6 +61,11 @@ Optional Properties:
>>>  - reset-deassert-us: Delay after the reset was deasserted in microseconds.
>>>    If this property is missing the delay will be skipped.
>>>  
>>> +- dev-addr: If set, it indicates the device address of the PHY to be used
>>> +  when accessing the C45 PHY registers over MDIO. It is used for vendor specific
>>> +  register space addresses that do no conform to standard address for the MDIO
>>> +  registers (e.g. MMD30)
>>
>> Rob made that comment earlier, and I have to ask again now, why don't we
>> have the Clause 45 PHY binding be modified such that you have a reg
>> property that has #address-size = 2? This should be entirely backwards
>> compatible, but it would allow you to specify that device address in a
>> more traditional way.
> 
> Hi Florian
> 
> I think we might get into trouble when we have both c22 and c45 on the
> same bus. Two different reg formats. I would have to try it and see to
> be sure.

Hum indeed, we would no longer be able to mix and match on the same MDIO
bus, unless we give C22 PHYs a "fake" second cell. Disregard that idea
then, and let's stick with 'dev-addr'.
-- 
Florian