netdev - Re: [PATCH v4 net-next 5/8] net: phylink: explicitly configure in-band autoneg for on-board PHYs

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Message-ID: <Y3dZ35RBf3z83Ph9@shell.armlinux.org.uk>
Date:   Fri, 18 Nov 2022 10:09:35 +0000
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Vladimir Oltean <vladimir.oltean@....com>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        UNGLinuxDriver@...rochip.com,
        bcm-kernel-feedback-list@...adcom.com,
        Madalin Bucur <madalin.bucur@....nxp.com>,
        Camelia Groza <camelia.groza@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Maxim Kochetkov <fido_max@...ox.ru>,
        Sean Anderson <sean.anderson@...o.com>,
        Antoine Tenart <atenart@...nel.org>,
        Michael Walle <michael@...le.cc>,
        Raag Jadav <raagjadav@...il.com>,
        Siddharth Vadapalli <s-vadapalli@...com>,
        Ong Boon Leong <boon.leong.ong@...el.com>,
        Colin Foster <colin.foster@...advantage.com>,
        Marek Behun <marek.behun@....cz>
Subject: Re: [PATCH v4 net-next 5/8] net: phylink: explicitly configure
 in-band autoneg for on-board PHYs

On Fri, Nov 18, 2022 at 02:01:21AM +0200, Vladimir Oltean wrote:
> +	if (pl->config->sync_an_inband && !phy_on_sfp(phy)) {

Hmm, this phy_on_sfp() is new to me, and looking at the git history, I
really don't think this does what it claims to do. This returns the
status of phydev->is_on_sfp_module, which is set by this code:

        phydev->phy_link_change = phy_link_change;
        if (dev) {
                phydev->attached_dev = dev;
                dev->phydev = phydev;

                if (phydev->sfp_bus_attached)
                        dev->sfp_bus = phydev->sfp_bus;
                else if (dev->sfp_bus)
                        phydev->is_on_sfp_module = true;
        }

... which is very wrong. "dev" here is the net_device, and a net_device
will have its sfp_bus member set when there is a SFP cage present,
which may be behind a off-SFP PHY.

This means that when a PHY is attached by the network driver in their
ndo_open, if there is a SFP bus on the interface (such as on the
Macchiatobin board), the above will set is_on_sfp_module true for the
on-board PHY even though it is not in the SFP module.

Essentially, commit b834489bcecc is incorrect, and needs to be fixed
before use is made of phy_on_sfp() outside of the broadcom driver.

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