[PATCH v4] net: ethernet: mtk_eth_soc: fix MTU warnings

[Frank Wunderlich <linux@fw-web.de>]

From: Landen Chao <landen.chao@mediatek.com>

in recent kernel versions there are warnings about incorrect MTU size
like these:

eth0: mtu greater than device maximum
mtk_soc_eth 1b100000.ethernet eth0: error -22 setting MTU to include DSA overhead

Fixes: bfcb813203e6 ("net: dsa: configure the MTU for switch ports")
Fixes: 72579e14a1d3 ("net: dsa: don't fail to probe if we couldn't set the MTU")
Fixes: 7a4c53bee332 ("net: report invalid mtu value via netlink extack")
Signed-off-by: Landen Chao <landen.chao@mediatek.com>
Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
---
v3->v4
  - fix commit-message (hyphernations,capitalisation) as suggested by Russell
  - add Signed-off-by Landen
  - dropped wrong signed-off from rene (because previous v1/2 was from him)
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index 85735d32ecb0..a1c45b39a230 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -2891,6 +2891,8 @@ static int mtk_add_mac(struct mtk_eth *eth, struct device_node *np)
 	eth->netdev[id]->irq = eth->irq[0];
 	eth->netdev[id]->dev.of_node = np;
 
+	eth->netdev[id]->max_mtu = MTK_MAX_RX_LENGTH - MTK_RX_ETH_HLEN;
+
 	return 0;
 
 free_netdev:
-- 
2.25.1