netdev - Re: [PATCH v2] net: phylink: don't start and stop SGMII PHYs in SFP modules twice

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Date:   Wed, 24 Jul 2019 14:38:10 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     asolokha@...kras.ru
Cc:     claudiu.manoil@....com, ioana.ciornei@....com,
        linux@...linux.org.uk, andrew@...n.ch, netdev@...r.kernel.org
Subject: Re: [PATCH v2] net: phylink: don't start and stop SGMII PHYs in
 SFP modules twice

From: Arseny Solokha <asolokha@...kras.ru>
Date: Wed, 24 Jul 2019 20:31:39 +0700

> SFP modules connected using the SGMII interface have their own PHYs which
> are handled by the struct phylink's phydev field. On the other hand, for
> the modules connected using 1000Base-X interface that field is not set.
> 
> Since commit ce0aa27ff3f6 ("sfp: add sfp-bus to bridge between network
> devices and sfp cages") phylink_start() ends up setting the phydev field
> using the sfp-bus infrastructure, which eventually calls phy_start() on it,
> and then calling phy_start() again on the same phydev from phylink_start()
> itself. Similar call sequence holds for phylink_stop(), only in the reverse
> order. This results in WARNs during network interface bringup and shutdown
> when a copper SFP module is connected, as phy_start() and phy_stop() are
> called twice in a row for the same phy_device:
 ...
> SFP modules with the 1000Base-X interface are not affected.
> 
> Place explicit calls to phy_start() and phy_stop() before enabling or after
> disabling an attached SFP module, where phydev is not yet set (or is
> already unset), so they will be made only from the inside of sfp-bus, if
> needed.
> 
> Signed-off-by: Arseny Solokha <asolokha@...kras.ru>

Applied with appropriate Fixes: tag added and queued up for -stable.

Thanks.