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

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Date:	Sat, 14 May 2016 01:44:10 +0200
From:	Andrew Lunn <andrew@...n.ch>
To:	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
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 Fri, May 13, 2016 at 11:56:12PM +0300, Sergei Shtylyov wrote:
> 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.

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?

      Andrew