netdev - [PATCH net-nex 2/2] net: mvneta: Don't speed down the PHY when changing mtu

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Date:   Mon, 27 Jul 2020 19:53:14 +0800
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Russell King <linux@...linux.org.uk>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH net-nex 2/2] net: mvneta: Don't speed down the PHY when
 changing mtu

We found a case where the phy link speed is changed to 10Mbps
then back to 1000Mbps when changing the mtu:

ethtool -s eth0 wol g
ip link set eth0 mtu 1400

Add a simple check to avoid unnecessary phylink_speed_down() when
changing the mtu.

Signed-off-by: Jisheng Zhang <Jisheng.Zhang@...aptics.com>
---
 drivers/net/ethernet/marvell/mvneta.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/marvell/mvneta.c b/drivers/net/ethernet/marvell/mvneta.c
index c9b6b0f85bb0..9cdbb05277eb 100644
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -3651,7 +3651,8 @@ static void mvneta_stop_dev(struct mvneta_port *pp)
 
 	set_bit(__MVNETA_DOWN, &pp->state);
 
-	if (device_may_wakeup(&pp->dev->dev))
+	if (device_may_wakeup(&pp->dev->dev) &&
+	    pp->pkt_size == MVNETA_RX_PKT_SIZE(pp->dev->mtu))
 		phylink_speed_down(pp->phylink, false);
 
 	phylink_stop(pp->phylink);
-- 
2.28.0.rc0