netdev - Re: [PATCH RFT 1/2] phylib: add device reset GPIO support

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Date:	Sun, 15 May 2016 00:46:20 +0300
From:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:	Andrew Lunn <andrew@...n.ch>
Cc:	Roger Quadros <rogerq@...com>,
	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
	grant.likely@...aro.org, robh+dt@...nel.org,
	devicetree@...r.kernel.org, f.fainelli@...il.com,
	netdev@...r.kernel.org, frowand.list@...il.com, pawel.moll@....com,
	mark.rutland@....com, ijc+devicetree@...lion.org.uk,
	galak@...eaurora.org, linux-kernel@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>
Subject: Re: [PATCH RFT 1/2] phylib: add device reset GPIO support

Hello.

On 05/14/2016 10:50 PM, 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 think we miss understood each other somewhere.
>
> Your code is great for one gpio reset line for one phy.
>
> I think there could be similar code one layer above to handle one gpio
> line for multiple phys.

    Ah, you want me to recognize some MAC/MDIO bound prop (e.g. 
"mdio-reset-gpios") in of_mdiobus_register()? I'll think about it now that my 
patch needs fixing anyway...

>      Andrew

MBR, Sergei