On Tue, Nov 19, 2024 at 02:46:59PM +0100, Krzysztof Hałasa wrote:

Hi,

ASIX AX88772B based USB 10/100 Ethernet adapter doesn't come
up ("carrier off"), despite the built-in 100BASE-FX PHY positive link
indication.

The problem appears to be in usbnet.c framework:

void usbnet_link_change(struct usbnet *dev, bool link, bool need_reset)
{
	/* update link after link is reseted */
	if (link && !need_reset)
		netif_carrier_on(dev->net);
	else
		netif_carrier_off(dev->net);

	if (need_reset && link)
		usbnet_defer_kevent(dev, EVENT_LINK_RESET);
	else
		usbnet_defer_kevent(dev, EVENT_LINK_CHANGE);
}

static int ax88772_phylink_setup(struct usbnet *dev)
{
        struct asix_common_private *priv = dev->driver_priv;
        phy_interface_t phy_if_mode;
        struct phylink *phylink;

        priv->phylink_config.dev = &dev->net->dev;
        priv->phylink_config.type = PHYLINK_NETDEV;
        priv->phylink_config.mac_capabilities = MAC_SYM_PAUSE | MAC_ASYM_PAUSE |
                MAC_10 | MAC_100;

etc.

This device is using phylink to manage the PHY. phylink will than
manage the carrier. It assumes it is solely responsible for the
carrier. So i think your fix is wrong. You probably should be removing
all code in this driver which touches the carrier.

	Andrew