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

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Message-ID: <1a44a737-2b81-625b-8edf-d1c3dfcdd619@cogentembedded.com>
Date:	Fri, 13 May 2016 23:56:12 +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

On 05/13/2016 11:44 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.

> So the gpio line is associated to the mdio bus, not a PHY.

    No.

> Either your MDIO driver needs to handle the gpio
> line,  or in __mdio_register(),

    __mdiobus_register(), you mean?

> before it starts looking at the
> children.

    It's basically the same thing.
    The MDIO bus reset is a misconception.

>
> 	Andrew

MBR, Sergei