netdev - [net-next PATCH] net: ethernet: stmicro: stmmac: permit MTU change with interface up

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Date:   Wed, 15 Jun 2022 00:41:41 +0200
From:   Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
To:     Giuseppe Cavallaro <peppe.cavallaro@...com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Jose Abreu <joabreu@...opsys.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        netdev@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Cc:     Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
Subject: [net-next PATCH] net: ethernet: stmicro: stmmac: permit MTU change with interface up

Remove the limitation where the interface needs to be down to change
MTU by releasing and opening the stmmac driver to set the new MTU.
Also call the set_filter function to correctly init the port.
This permits to remove the EBUSY error while the ethernet port is
running permitting a correct MTU change if for example a DSA request
a MTU change for a switch CPU port.

Signed-off-by: Christian 'Ansuel' Marangi <ansuelsmth@...il.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index d1a7cf4567bc..a968a13b3183 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -5448,11 +5448,6 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 
 	txfifosz /= priv->plat->tx_queues_to_use;
 
-	if (netif_running(dev)) {
-		netdev_err(priv->dev, "must be stopped to change its MTU\n");
-		return -EBUSY;
-	}
-
 	if (stmmac_xdp_is_enabled(priv) && new_mtu > ETH_DATA_LEN) {
 		netdev_dbg(priv->dev, "Jumbo frames not supported for XDP\n");
 		return -EINVAL;
@@ -5466,6 +5461,14 @@ static int stmmac_change_mtu(struct net_device *dev, int new_mtu)
 
 	dev->mtu = mtu;
 
+	if (netif_running(dev)) {
+		netdev_dbg(priv->dev, "restarting interface to change its MTU\n");
+		stmmac_release(dev);
+
+		stmmac_open(dev);
+		stmmac_set_filter(priv, priv->hw, dev);
+	}
+
 	netdev_update_features(dev);
 
 	return 0;
-- 
2.36.1