net: systemport: Fix reception of BPDUs

BugLink: https://bugs.launchpad.net/bugs/1822271

[ Upstream commit a40061ea ]

SYSTEMPORT has its RXCHK parser block that attempts to validate the
packet structures, unfortunately setting the L2 header check bit will
cause Bridge PDUs (BPDUs) to be incorrectly rejected because they look
like LLC/SNAP packets with a non-IPv4 or non-IPv6 Ethernet Type.

Fixes: 4e8aedfe78c7 ("net: systemport: Turn on offloads by default")
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Juerg Haefliger <juerg.haefliger@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/ethernet/broadcom/bcmsysport.c

@@ -126,6 +126,10 @@ static int bcm_sysport_set_rx_csum(struct net_device *dev,
 
 	priv->rx_chk_en = !!(wanted & NETIF_F_RXCSUM);
 	reg = rxchk_readl(priv, RXCHK_CONTROL);
+	/* Clear L2 header checks, which would prevent BPDUs
+	 * from being received.
+	 */
+	reg &= ~RXCHK_L2_HDR_DIS;
 	if (priv->rx_chk_en)
 		reg |= RXCHK_EN;
 	else