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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Jan Hoffmann <jan@3e8.eu>,
        Hauke Mehrtens <hauke@hauke-m.de>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 5.4 186/260] net: dsa: lantiq_gswip: fix maximum frame length
Date:   Mon, 20 Sep 2021 18:43:24 +0200
Message-Id: <20210920163937.430977332@linuxfoundation.org>
In-Reply-To: <20210920163931.123590023@linuxfoundation.org>
References: <20210920163931.123590023@linuxfoundation.org>
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From: Jan Hoffmann <jan@3e8.eu>

commit 552799f8b3b0074d2617f53a63a088f9514a66e3 upstream.

Currently, outgoing packets larger than 1496 bytes are dropped when
tagged VLAN is used on a switch port.

Add the frame check sequence length to the value of the register
GSWIP_MAC_FLEN to fix this. This matches the lantiq_ppa vendor driver,
which uses a value consisting of 1518 bytes for the MAC frame, plus the
lengths of special tag and VLAN tags.

Fixes: 14fceff4771e ("net: dsa: Add Lantiq / Intel DSA driver for vrx200")
Cc: stable@vger.kernel.org
Signed-off-by: Jan Hoffmann <jan@3e8.eu>
Acked-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/dsa/lantiq_gswip.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/dsa/lantiq_gswip.c
+++ b/drivers/net/dsa/lantiq_gswip.c
@@ -837,7 +837,8 @@ static int gswip_setup(struct dsa_switch
 
 	gswip_switch_mask(priv, 0, GSWIP_MAC_CTRL_2_MLEN,
 			  GSWIP_MAC_CTRL_2p(cpu_port));
-	gswip_switch_w(priv, VLAN_ETH_FRAME_LEN + 8, GSWIP_MAC_FLEN);
+	gswip_switch_w(priv, VLAN_ETH_FRAME_LEN + 8 + ETH_FCS_LEN,
+		       GSWIP_MAC_FLEN);
 	gswip_switch_mask(priv, 0, GSWIP_BM_QUEUE_GCTRL_GL_MOD,
 			  GSWIP_BM_QUEUE_GCTRL);