linux-kernel - Re: [PATCH] usbnet_link_change() fails to call netif_carrier

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Message-ID: <9baf4f17-bae6-4f5c-b9a1-92dc48fd7a8d@lunn.ch>
Date: Tue, 19 Nov 2024 17:20:34 +0100
From: Andrew Lunn <andrew@...n.ch>
To: Krzysztof Hałasa <khalasa@...p.pl>
Cc: netdev <netdev@...r.kernel.org>, Oliver Neukum <oneukum@...e.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
	Jose Ignacio Tornos Martinez <jtornosm@...hat.com>,
	Ming Lei <ming.lei@...onical.com>
Subject: Re: [PATCH] usbnet_link_change() fails to call netif_carrier_on()

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