cxgb3: FIx VLAN over Jumbo frames

The mac is expected to auto-inflate the Maximum Frame size for VLAN
tagged frames. It however does not work with jumbo frames.
Work around the bug adding 4 to the Maximum Frame for MTUs
greater than 1536.

Signed-off-by: Divy Le Ray <divy@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/drivers/net/cxgb3/xgmac.c b/drivers/net/cxgb3/xgmac.c
index 0109ee4f2f9..0c08de5d09f 100644
--- a/drivers/net/cxgb3/xgmac.c
+++ b/drivers/net/cxgb3/xgmac.c
@@ -353,6 +353,9 @@ int t3_mac_set_mtu(struct cmac *mac, unsigned int mtu)
          * packet size register includes header, but not FCS.
          */
         mtu += 14;
+        if (mtu > 1536)
+                mtu += 4;
+
         if (mtu > MAX_FRAME_SIZE - 4)
                 return -EINVAL;
         t3_write_reg(adap, A_XGM_RX_MAX_PKT_SIZE + mac->offset, mtu);