[dpdk-dev] [PATCH 2/2] cxgbe: fix setting wrong device mtu

[Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>]

max_rx_pkt_len already includes ETHER_HDR_LEN and ETHER_CRC_LEN for the
mtu. But, the firmware also adds ETHER_HDR_LEN and ETHER_CRC_LEN to the
mtu specified. Fix by subtracting these values from the mtu before
passing it to firmware.

Fixes: 4b2eff452d2e ("cxgbe: enable jumbo frames")

Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: Kumar Sanghvi <kumaras@chelsio.com>
---
 doc/guides/rel_notes/release_2_3.rst | 5 +++++
 drivers/net/cxgbe/cxgbe_main.c       | 5 ++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/guides/rel_notes/release_2_3.rst b/doc/guides/rel_notes/release_2_3.rst
index 4c5843d..15cc572 100644
--- a/doc/guides/rel_notes/release_2_3.rst
+++ b/doc/guides/rel_notes/release_2_3.rst
@@ -21,6 +21,11 @@ Drivers
   table that gets overwritten by subsequent port 1's part of the rss
   table due to incorrect size allocated for each entry in the table.
 
+* **cxgbe: fix setting wrong device mtu**
+
+  Fixed an incorrect device mtu being set due to ethernet header and
+  crc lengths being added twice.
+
 
 Libraries
 ~~~~~~~~~
diff --git a/drivers/net/cxgbe/cxgbe_main.c b/drivers/net/cxgbe/cxgbe_main.c
index 632abc2..1683ca5 100644
--- a/drivers/net/cxgbe/cxgbe_main.c
+++ b/drivers/net/cxgbe/cxgbe_main.c
@@ -855,7 +855,10 @@ int link_start(struct port_info *pi)
 {
 	struct adapter *adapter = pi->adapter;
 	int ret;
-	unsigned int mtu = pi->eth_dev->data->dev_conf.rxmode.max_rx_pkt_len;
+	unsigned int mtu;
+
+	mtu = pi->eth_dev->data->dev_conf.rxmode.max_rx_pkt_len -
+	      (ETHER_HDR_LEN + ETHER_CRC_LEN);
 
 	/*
 	 * We do not set address filters and promiscuity here, the stack does
-- 
2.5.3