netdev - Re: [PATCH net-next 4/7] net: phy: marvell10g: Add support for 2.5GBASET and 5GBASET

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Message-ID: <20190121201715.GA20277@lunn.ch>
Date:   Mon, 21 Jan 2019 21:17:15 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Maxime Chevallier <maxime.chevallier@...tlin.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Florian Fainelli <f.fainelli@...il.com>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Russell King <linux@...linux.org.uk>,
        linux-arm-kernel@...ts.infradead.org,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        thomas.petazzoni@...tlin.com, gregory.clement@...tlin.com,
        miquel.raynal@...tlin.com, nadavh@...vell.com, stefanc@...vell.com,
        mw@...ihalf.com
Subject: Re: [PATCH net-next 4/7] net: phy: marvell10g: Add support for
 2.5GBASET and 5GBASET

> @@ -264,8 +265,10 @@ static int mv3310_config_init(struct phy_device *phydev)
>  	if (ret)
>  		return ret;
>  
> -	linkmode_and(phydev->advertising, phydev->advertising,
> -		     phydev->supported);
> +	/* Make sure we advertise all the supported modes, and not just the
> +	 * default one specified in the driver's .features.
> +	 */
> +	linkmode_copy(phydev->advertising, phydev->supported);

Hi Maxime

What Russell is referring to is:

static int phy_probe(struct device *dev)
{
..
        /* Start out supporting everything. Eventually,
         * a controller will attach, and may modify one
         * or both of these values
         */
        linkmode_copy(phydev->supported, phydrv->features);
        of_set_phy_supported(phydev);
        linkmode_copy(phydev->advertising, phydev->supported);

        /* Get the EEE modes we want to prohibit. We will ask
         * the PHY stop advertising these mode later on
         */
        of_set_phy_eee_broken(phydev);

        /* The Pause Frame bits indicate that the PHY can support passing
         * pause frames. During autonegotiation, the PHYs will determine if
         * they should allow pause frames to pass.  The MAC driver should then
         * use that result to determine whether to enable flow control via
         * pause frames.
         *
         * Normally, PHY drivers should not set the Pause bits, and instead
         * allow phylib to do that.  However, there may be some situations
         * (e.g. hardware erratum) where the driver wants to set only one
         * of these bits.
         */
        if (test_bit(ETHTOOL_LINK_MODE_Pause_BIT, phydrv->features) ||
            test_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT, phydrv->features)) {
                linkmode_clear_bit(ETHTOOL_LINK_MODE_Pause_BIT,
                                   phydev->supported);
                linkmode_clear_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT,
                                  phydev->supported);
                if (test_bit(ETHTOOL_LINK_MODE_Pause_BIT, phydrv->features))
                        linkmode_set_bit(ETHTOOL_LINK_MODE_Pause_BIT,
                                         phydev->supported);
                if (test_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT,
                             phydrv->features))
                        linkmode_set_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT,
                                         phydev->supported);
        } else {
                linkmode_set_bit(ETHTOOL_LINK_MODE_Pause_BIT,
                                 phydev->supported);
                linkmode_set_bit(ETHTOOL_LINK_MODE_Asym_Pause_BIT,
                                 phydev->supported);
        }

So by doing a copy of supported into advertising, you can stomping
over any restrictions applied via of_set_phy_supported(),
of_set_phy_eee_broken(phydev), and any pause control settings which
might of happened.

What might make sense here is that a PHY driver can replace its
.features member at run time, in its config_init() call. The core then
needs to perform these evaluations. So i'm guessing we need to split
this code out of probe() and move it into phy_init_hw()?

Heiner, you know this code better than anybody. What do you think?

	Andrew