netdev - Re: [RFC PATCH 2/2] net: phylink: don't start and stop SGMII PHYs in SFP modules twice

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Date:   Wed, 24 Jul 2019 10:01:39 +0100
From:   Russell King - ARM Linux admin <linux@...linux.org.uk>
To:     Arseny Solokha <asolokha@...kras.ru>
Cc:     Claudiu Manoil <claudiu.manoil@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Andrew Lunn <andrew@...n.ch>, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 2/2] net: phylink: don't start and stop SGMII PHYs in
 SFP modules twice

On Tue, Jul 23, 2019 at 10:17:02PM +0700, Arseny Solokha wrote:
> SFP modules connected using the SGMII interface have their own PHYs which
> are handled by the struct phylink's phydev field. After commit ce0aa27ff3f6
> ("sfp: add sfp-bus to bridge between network devices and sfp cages") an
> sfp-bus attached to the same phylink also gets control over a PHY in an SFP
> module which is actually the same PHY managed by phylink itself. 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:
>...
> So, skip explicit calls to phy_start() and phy_stop() when phylink has just
> enabled or disabled an attached SFP module.

I'd prefer if we re-ordered these so phy_start() happens before
sfp_upstream_start() and the reverse for the stop calls.

pl->phydev won't be set at these points, so the calls will be no-ops.
(The reason is when we support mac--phy--sfp setups, having the
phy_start() and phy_stop() here are still necessary.)

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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