Re: [PATCH v2 net-next 3/3] net: phy: aquantia: add support for aqr115c

["Russell King (Oracle)" <linux@armlinux.org.uk>]

On Thu, Jun 27, 2024 at 01:30:17PM +0200, Bartosz Golaszewski wrote:
> +static int aqr115c_config_init(struct phy_device *phydev)
> +{
> +	/* Check that the PHY interface type is compatible */
> +	if (phydev->interface != PHY_INTERFACE_MODE_SGMII &&
> +	    phydev->interface != PHY_INTERFACE_MODE_2500BASEX)
> +		return -ENODEV;
> +
> +	phy_set_max_speed(phydev, SPEED_2500);

Please can you explain why this is necessary? Does the PHY report that
it incorrectly supports faster speeds than 2500base-X ?

If phylib is incorrectly detecting the PHYs features, then this should
be corrected via the .get_features method, not in the .config_init
method.

(The same should be true of the other Aquantia PHYs.)

Note that phy_set_max_speed() is documented as:

 * The PHY might be more capable than the MAC. For example a Fast Ethernet
 * is connected to a 1G PHY. This function allows the MAC to indicate its
 * maximum speed, and so limit what the PHY will advertise.

Aquantia seems to be the only PHY driver that calls this function.

Thanks.

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