netdev - Re: [EXT] Re: [PATCH net-next 10/18] net: mvpp2: use the GoP interrupt for link status changes

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Message-ID: <20170824105923.GF23960@kwain>
Date:   Thu, 24 Aug 2017 12:59:23 +0200
From:   Antoine Tenart <antoine.tenart@...e-electrons.com>
To:     Marcin Wojtas <mw@...ihalf.com>
Cc:     Antoine Tenart <antoine.tenart@...e-electrons.com>,
        Stefan Chulski <stefanc@...vell.com>,
        Andrew Lunn <andrew@...n.ch>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "jason@...edaemon.net" <jason@...edaemon.net>,
        "gregory.clement@...e-electrons.com" 
        <gregory.clement@...e-electrons.com>,
        "sebastian.hesselbarth@...il.com" <sebastian.hesselbarth@...il.com>,
        "thomas.petazzoni@...e-electrons.com" 
        <thomas.petazzoni@...e-electrons.com>,
        Nadav Haklai <nadavh@...vell.com>,
        "linux@...linux.org.uk" <linux@...linux.org.uk>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [EXT] Re: [PATCH net-next 10/18] net: mvpp2: use the GoP
 interrupt for link status changes

Hi Marcin,

On Wed, Aug 23, 2017 at 11:05:33PM +0200, Marcin Wojtas wrote:
> 2017-08-23 18:04 GMT+02:00 Antoine Tenart <antoine.tenart@...e-electrons.com>:
> > On Wed, Aug 23, 2017 at 03:24:55PM +0000, Stefan Chulski wrote:
> >> > When the cable is connected (there is signal) and the serdes is in sync and AN
> >> > succeeded.
> >> >
> >> > > With SFF/SFP ports, you generally need a gpio line the fibre module
> >> > > can use to indicate if it has link. Fixed-phy has such support, and
> >> > > your link_change function will get called when the link changes.
> >> >
> >> > So that would work when using SFP modules but I wonder if the GoP irq isn't
> >> > needed when using passive cable, in which case this patch would still be needed
> >> > (and of course we should support the new Russell phylib capabilities).
> >>
> >> Even if new phylib driver supports passive direct cables connection,
> >> GoP IRQ required for SOHO/Peridot external switch support.
> >> SOHO/Peridot external switch could be connected directly to Serdes line.
> >
> > So I guess the GoP link irq patches are needed. Should I resend them
> > then?
> >
> > We'll have to discuss how to handle fixed-phy vs GoP IRQ, but I guess we
> > can do this when adding the fixed-phy support later.
> >
> 
> Please check mvneta.c - you can find there coexistence of normal
> libphy support, fixed phy and link irq for the inband management mode.
> IMO it's exactly, what you need here.

From what I see it should be pretty easy to support phy, fixed-phy and
the GoP irq without breaking anything: if no phy is found in the dt,
call of_phy_register_fixed_link() and if the fixed-phy property isn't
found either use the GoP link IRQ. This way all the possibilities would
be supported.

So we should be able to support fixed-phy in a future series.

Antoine

-- 
Antoine Ténart, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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