linux-kernel - [PATCH net] net: phylink: initialize carrier state at creation

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Date:   Mon,  6 Nov 2023 19:05:06 +0100
From:   Klaus Kudielka <klaus.kudielka@...il.com>
To:     Russell King <linux@...linux.org.uk>, Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Klaus Kudielka <klaus.kudielka@...il.com>
Subject: [PATCH net] net: phylink: initialize carrier state at creation

Background: Turris Omnia (Armada 385); eth2 (mvneta) connected to SFP bus;
SFP module is present, but no fiber connected, so definitely no carrier.

After booting, eth2 is down, but netdev LED trigger surprisingly reports
link active. Then, after "ip link set eth2 up", the link indicator goes
away - as I would have expected it from the beginning.

It turns out, that the default carrier state after netdev creation is
"carrier ok". Some ethernet drivers explicitly call netif_carrier_off
during probing, others (like mvneta) don't - which explains the current
behaviour: only when the device is brought up, phylink_start calls
netif_carrier_off.

Fix this for all drivers, by calling netif_carrier_off in phylink_create.

Suggested-by: Andrew Lunn <andrew@...n.ch>
Signed-off-by: Klaus Kudielka <klaus.kudielka@...il.com>
---
 drivers/net/phy/phylink.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/net/phy/phylink.c b/drivers/net/phy/phylink.c
index 6712883498..a28da80bde 100644
--- a/drivers/net/phy/phylink.c
+++ b/drivers/net/phy/phylink.c
@@ -1616,6 +1616,7 @@ struct phylink *phylink_create(struct phylink_config *config,
 	pl->config = config;
 	if (config->type == PHYLINK_NETDEV) {
 		pl->netdev = to_net_dev(config->dev);
+		netif_carrier_off(pl->netdev);
 	} else if (config->type == PHYLINK_DEV) {
 		pl->dev = config->dev;
 	} else {
-- 
2.42.0