net: lan966x: Fix the MTU calculation

When the MTU was changed, the lan966x didn't take in consideration
the L2 header and the FCS. So the HW was configured with a smaller
value than what was desired. Therefore the correct value to configure
the HW would be new_mtu + ETH_HLEN + ETH_FCS_LEN.
The vlan tag is not considered here, because at the time when the
blamed commit was added, there was no vlan filtering support. The
vlan fix will be part of the next patch.

Fixes: d28d6d2e37d1 ("net: lan966x: add port module support")
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
index be2fd03..b3070c3 100644 (file)
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.c
@@ -386,7 +386,7 @@ static int lan966x_port_change_mtu(struct net_device *dev, int new_mtu)
        int old_mtu = dev->mtu;
        int err;
 
-       lan_wr(DEV_MAC_MAXLEN_CFG_MAX_LEN_SET(new_mtu),
+       lan_wr(DEV_MAC_MAXLEN_CFG_MAX_LEN_SET(LAN966X_HW_MTU(new_mtu)),
               lan966x, DEV_MAC_MAXLEN_CFG(port->chip_port));
        dev->mtu = new_mtu;
 

diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
index 9656071..4ec3399 100644 (file)
--- a/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
+++ b/drivers/net/ethernet/microchip/lan966x/lan966x_main.h
@@ -26,6 +26,8 @@
 #define LAN966X_BUFFER_MEMORY          (160 * 1024)
 #define LAN966X_BUFFER_MIN_SZ          60
 
+#define LAN966X_HW_MTU(mtu)            ((mtu) + ETH_HLEN + ETH_FCS_LEN)
+
 #define PGID_AGGR                      64
 #define PGID_SRC                       80
 #define PGID_ENTRIES                   89