netdev - Re: [PATCH net-next v2 03/13] net: phy: sfp: warn the user when no tx

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Date:   Tue, 8 May 2018 13:45:53 +0100
From:   Russell King - ARM Linux <linux@...linux.org.uk>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Florian Fainelli <f.fainelli@...il.com>, mw@...ihalf.com,
        ymarkman@...vell.com, jason@...edaemon.net,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        netdev@...r.kernel.org, gregory.clement@...tlin.com, kishon@...com,
        nadavh@...vell.com, linux-arm-kernel@...ts.infradead.org,
        thomas.petazzoni@...tlin.com, miquel.raynal@...tlin.com,
        stefanc@...vell.com, maxime.chevallier@...tlin.com,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        sebastian.hesselbarth@...il.com
Subject: Re: [PATCH net-next v2 03/13] net: phy: sfp: warn the user when no
 tx_disable pin is available

On Sat, May 05, 2018 at 10:52:42PM +0200, Andrew Lunn wrote:
> On Sat, May 05, 2018 at 01:38:31PM -0700, Florian Fainelli wrote:
> > On May 4, 2018 10:14:25 AM PDT, Andrew Lunn <andrew@...n.ch> wrote:
> > >On Fri, May 04, 2018 at 10:07:53AM -0700, Florian Fainelli wrote:
> > >> On 05/04/2018 06:56 AM, Antoine Tenart wrote:
> > >> > In case no Tx disable pin is available the SFP modules will always
> > >be
> > >> > emitting. This could be an issue when using modules using laser as
> > >their
> > >> > light source as we would have no way to disable it when the fiber
> > >is
> > >> > removed. This patch adds a warning when registering an SFP cage
> > >which do
> > >> > not have its tx_disable pin wired or available.
> > >> 
> > >> Is this something that was done in a possibly earlier revision of a
> > >> given board design and which was finally fixed? Nothing wrong with
> > >the
> > >> patch, but this seems like a pretty serious board design mistake,
> > >that
> > >> needs to be addressed.
> > >
> > >Hi Florian
> > >
> > >Zii Devel B is like this. Only the "Signal Detect" pin is wired to a
> > >GPIO.
> > 
> 
> > Good point, indeed. BTW what do you think about exposing the SFF's
> > EEPROM and diagnostics through the standard ethtool operations even
> > if we have to keep the description of the SFF as a fixed link in
> > Device Tree because of the unfortunate wiring?
> 
> I believe in Antoine case, all the control plane is broken. He cannot
> read the EEPROM, nor any of the modules pins via GPIOs.

Correct.

> For Zii Devel B, the EEPROM is accessible, and so is the SD pin. What
> is missing is transmit disable. So i would expose it as an SFF module.

Agreed.

-- 
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