netdev - Re: [PATCH 1/3] net: ethernet: add support for PCS and 2.5G speed

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Date:   Fri, 22 Feb 2019 22:39:53 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Parshuram Thombare <pthombar@...ence.com>
Cc:     nicolas.ferre@...rochip.com, davem@...emloft.net,
        netdev@...r.kernel.org, f.fainelli@...il.com, hkallweit1@...il.com,
        linux-kernel@...r.kernel.org, rafalc@...ence.com,
        piotrs@...ence.com, jank@...ence.com
Subject: Re: [PATCH 1/3] net: ethernet: add support for PCS and 2.5G speed

>  	/* mask with MAC supported features */
> -	if (macb_is_gem(bp) && bp->caps & MACB_CAPS_GIGABIT_MODE_AVAILABLE)
> -		phy_set_max_speed(phydev, SPEED_1000);
> -	else
> -		phy_set_max_speed(phydev, SPEED_100);
> +	if (macb_is_gem(bp)) {
> +		linkmode_copy(phydev->supported, PHY_GBIT_FEATURES);
> +		if (bp->caps & MACB_CAPS_TWO_PT_FIVE_GIG_SPEED)
> +			linkmode_set_bit(ETHTOOL_LINK_MODE_2500baseT_Full_BIT,
> +					 phydev->supported);
> +	} else {
> +		linkmode_copy(phydev->supported, PHY_BASIC_FEATURES);
> +	}
> +
> +	linkmode_copy(phydev->advertising, phydev->supported);

This is not correct. Just because the MAC can do 2.5G does not mean
the PHY can. So you should not be adding links modes. Also, somebody
might be using a PHY that can do 2.5G with a MAC which can only do 1G.

The correct thing to do is call phy_set_max_speed() with the maximum
speed the MAC can do.

      Andrew