[PATCH 3/4] enic: add an update MTU function for non-Rx scatter mode

[John Daley <johndale@cisco.com>]

Provide an update MTU callbaack. The function returns -ENOTSUP
if Rx scatter is enabled. Updating the MTU to be greater than
the value configured via the Cisco CIMC/UCSM management interface
is allowed provided it is still less than the maximum egress packet
size allowed by the NIC.

Signed-off-by: John Daley <johndale@cisco.com>
---
 drivers/net/enic/enic.h        |  1 +
 drivers/net/enic/enic_ethdev.c | 10 +++++++++-
 drivers/net/enic/enic_main.c   | 44 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 54 insertions(+), 1 deletion(-)

diff --git a/drivers/net/enic/enic.h b/drivers/net/enic/enic.h
index 78f7bd7..8122358 100644
--- a/drivers/net/enic/enic.h
+++ b/drivers/net/enic/enic.h
@@ -245,4 +245,5 @@ uint16_t enic_recv_pkts(void *rx_queue, struct rte_mbuf **rx_pkts,
 			uint16_t nb_pkts);
 uint16_t enic_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
 			       uint16_t nb_pkts);
+int enic_set_mtu(struct enic *enic, uint16_t new_mtu);
 #endif /* _ENIC_H_ */
diff --git a/drivers/net/enic/enic_ethdev.c b/drivers/net/enic/enic_ethdev.c
index 31d9600..9a738c2 100644
--- a/drivers/net/enic/enic_ethdev.c
+++ b/drivers/net/enic/enic_ethdev.c
@@ -520,6 +520,14 @@ static void enicpmd_remove_mac_addr(struct rte_eth_dev *eth_dev, __rte_unused ui
 	enic_del_mac_address(enic);
 }
 
+static int enicpmd_mtu_set(struct rte_eth_dev *eth_dev, uint16_t mtu)
+{
+	struct enic *enic = pmd_priv(eth_dev);
+
+	ENICPMD_FUNC_TRACE();
+	return enic_set_mtu(enic, mtu);
+}
+
 static const struct eth_dev_ops enicpmd_eth_dev_ops = {
 	.dev_configure        = enicpmd_dev_configure,
 	.dev_start            = enicpmd_dev_start,
@@ -537,7 +545,7 @@ static const struct eth_dev_ops enicpmd_eth_dev_ops = {
 	.queue_stats_mapping_set = NULL,
 	.dev_infos_get        = enicpmd_dev_info_get,
 	.dev_supported_ptypes_get = enicpmd_dev_supported_ptypes_get,
-	.mtu_set              = NULL,
+	.mtu_set              = enicpmd_mtu_set,
 	.vlan_filter_set      = enicpmd_vlan_filter_set,
 	.vlan_tpid_set        = NULL,
 	.vlan_offload_set     = enicpmd_vlan_offload_set,
diff --git a/drivers/net/enic/enic_main.c b/drivers/net/enic/enic_main.c
index 32ecdae..c23938a 100644
--- a/drivers/net/enic/enic_main.c
+++ b/drivers/net/enic/enic_main.c
@@ -854,6 +854,50 @@ int enic_set_vnic_res(struct enic *enic)
 	return rc;
 }
 
+/* The Cisco NIC can send and receive packets up to a max packet size
+ * determined by the NIC type and firmware. There is also an MTU
+ * configured into the NIC via the CIMC/UCSM management interface
+ * which can be overridden by this function (up to the max packet size).
+ * Depending on the network setup, doing so may cause packet drops
+ * and unexpected behavior.
+ */
+int enic_set_mtu(struct enic *enic, uint16_t new_mtu)
+{
+	uint16_t old_mtu;	/* previous setting */
+	uint16_t config_mtu;	/* Value configured into NIC via CIMC/UCSM */
+	struct rte_eth_dev *eth_dev = enic->rte_dev;
+
+	old_mtu = eth_dev->data->mtu;
+	config_mtu = enic->config.mtu;
+
+	/* only works with Rx scatter disabled */
+	if (enic->rte_dev->data->dev_conf.rxmode.enable_scatter)
+		return -ENOTSUP;
+
+	if (new_mtu > enic->max_mtu) {
+		dev_err(enic,
+			"MTU not updated: requested (%u) greater than max (%u)\n",
+			new_mtu, enic->max_mtu);
+		return -EINVAL;
+	}
+	if (new_mtu < ENIC_MIN_MTU) {
+		dev_info(enic,
+			"MTU not updated: requested (%u) less than min (%u)\n",
+			new_mtu, ENIC_MIN_MTU);
+		return -EINVAL;
+	}
+	if (new_mtu > config_mtu)
+		dev_warning(enic,
+			"MTU (%u) is greater than value configured in NIC (%u)\n",
+			new_mtu, config_mtu);
+
+	/* update the mtu */
+	eth_dev->data->mtu = new_mtu;
+
+	dev_info(enic, "MTU changed from %u to %u\n",  old_mtu, new_mtu);
+	return 0;
+}
+
 static int enic_dev_init(struct enic *enic)
 {
 	int err;
-- 
2.7.0