netdev - Re: Cutting the link on ndo_stop - phy_stop or phy

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Message-ID: <CA+h21hrJPAoieooUKY=dBxoteJ32DfAXHYtfm0rVi25g9gKuxg@mail.gmail.com>
Date:   Tue, 4 Jun 2019 23:42:45 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     "linux@...linux.org.uk" <linux@...linux.org.uk>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Ioana Ciornei <ioana.ciornei@....com>
Subject: Re: Cutting the link on ndo_stop - phy_stop or phy_disconnect?

On Tue, 4 Jun 2019 at 23:07, Andrew Lunn <andrew@...n.ch> wrote:
>
> On Tue, Jun 04, 2019 at 10:58:41PM +0300, Vladimir Oltean wrote:
> > Hi,
> >
> > I've been wondering what is the correct approach to cut the Ethernet link
> > when the user requests it to be administratively down (aka ip link set dev
> > eth0 down).
> > Most of the Ethernet drivers simply call phy_stop or the phylink equivalent.
> > This leaves an Ethernet link between the PHY and its link partner.
> > The Freescale gianfar driver (authored by Andy Fleming who also authored the
> > phylib) does a phy_disconnect here. It may seem a bit overkill, but of the
> > extra things it does, it calls phy_suspend where most PHY drivers set the
> > BMCR_PDOWN bit. Only this achieves the intended purpose of also cutting the
> > link partner's link on 'ip link set dev eth0 down'.
>
> Hi Vladimir
>
> Heiner knows the state machine better than i. But when we transition
> to PHY_HALTED, as part of phy_stop(), it should do a phy_suspend().
>
>    Andrew

Hi Andrew, Florian,

Thanks for giving me the PHY_HALTED hint!
Indeed it looks like I conflated two things - the Ehernet port that
uses phy_disconnect also happens to be connected to a PHY that has
phy_suspend implemented. Whereas the one that only does phy_stop is
connected to a PHY that doesn't have that... I thought that in absence
of .suspend, the PHY library automatically calls genphy_suspend. Oh
well, looks like it doesn't. So of course, phy_stop calls phy_suspend
too.
But now the second question: between a phy_connect and a phy_start,
shouldn't the PHY be suspended too? Experimentally it looks like it
still isn't.
By the way, Florian, yes, PHY drivers that use WOL still set
BMCR_ISOLATE, which cuts the MII-side, so that's ok. However that's
not the case here - no WOL.

Regards,
-Vladimir