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SubjectRe: [PATCH RFT 1/2] phylib: add device reset GPIO support
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Hello.

On 05/14/2016 02:44 AM, Andrew Lunn wrote:

>>>>> Another issue is that on some boards we have one reset line tied to
>>>>> multiple PHYs.How do we prevent multiple resets being taking place when each of
>>>>> the PHYs are registered?
>>>>
>>>> My patch just doesn't address this case -- it's about the
>>>> individual resets only.
>>>
>>> This actually needs to be addresses a layer above. What you have is a
>>> bus reset, not a device reset.
>>
>> No.
>> There's simply no such thing as a bus reset for the xMII/MDIO
>> busses, there's simply no reset signaling on them. Every device has
>> its own reset signal and its own timing requirements.
>
> Except in the case above, where two phys are sharing the same reset
> signal. So although it is not part of the mdio standard to have a bus
> reset, this is in effect what the gpio line is doing, resetting all
> devices on the bus. If you don't model that as a bus reset, how do you
> model it?

I'm not suggesting that the shared reset should be handled by my patch.
Contrariwise, I suggested to use the mii_bus::reset() method -- I see it as a
necessary evil. However, in the more common case of a single PHY, this method
simply doesn't scale -- you'd have to teach each and every individual MAC/
MDIO driver to do the GPIO reset trick.

> Andrew

MBR, Sergei

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