net: hns3: Add support to change MTU in HNS3 hardware

This patch adds the following support to the HNS3 driver:
1. Support to change the Maximum Transmission Unit of a
   port in the HNS NIC hardware.
2. Initializes the supported MTU range for the netdevice.
Signed-off-by: Nlipeng <lipeng321@huawei.com>
Signed-off-by: NSalil Mehta <salil.mehta@huawei.com>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Reviewed-by: NLeon Romanovsky <leonro@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.c

@@ -1278,11 +1278,42 @@ static int hns3_ndo_set_vf_vlan(struct net_device *netdev, int vf, u16 vlan,
 	return ret;
 }
 
+static int hns3_nic_change_mtu(struct net_device *netdev, int new_mtu)
+{
+	struct hns3_nic_priv *priv = netdev_priv(netdev);
+	struct hnae3_handle *h = priv->ae_handle;
+	bool if_running = netif_running(netdev);
+	int ret;
+
+	if (!h->ae_algo->ops->set_mtu)
+		return -EOPNOTSUPP;
+
+	/* if this was called with netdev up then bring netdevice down */
+	if (if_running) {
+		(void)hns3_nic_net_stop(netdev);
+		msleep(100);
+	}
+
+	ret = h->ae_algo->ops->set_mtu(h, new_mtu);
+	if (ret) {
+		netdev_err(netdev, "failed to change MTU in hardware %d\n",
+			   ret);
+		return ret;
+	}
+
+	/* if the netdev was running earlier, bring it up again */
+	if (if_running && hns3_nic_net_open(netdev))
+		ret = -EINVAL;
+
+	return ret;
+}
+
 static const struct net_device_ops hns3_nic_netdev_ops = {
 	.ndo_open		= hns3_nic_net_open,
 	.ndo_stop		= hns3_nic_net_stop,
 	.ndo_start_xmit		= hns3_nic_net_xmit,
 	.ndo_set_mac_address	= hns3_nic_net_set_mac_address,
+	.ndo_change_mtu		= hns3_nic_change_mtu,
 	.ndo_set_features	= hns3_nic_set_features,
 	.ndo_get_stats64	= hns3_nic_get_stats64,
 	.ndo_setup_tc		= hns3_nic_setup_tc,
@@ -2752,6 +2783,9 @@ static int hns3_client_init(struct hnae3_handle *handle)
 		goto out_reg_netdev_fail;
 	}
 
+	/* MTU range: (ETH_MIN_MTU(kernel default) - 9706) */
+	netdev->max_mtu = HNS3_MAX_MTU - (ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN);
+
 	return ret;
 
 out_reg_netdev_fail:

drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.h

@@ -76,6 +76,7 @@ enum hns3_nic_state {
 #define HNS3_RING_NAME_LEN			16
 #define HNS3_BUFFER_SIZE_2048			2048
 #define HNS3_RING_MAX_PENDING			32768
+#define HNS3_MAX_MTU				9728
 
 #define HNS3_BD_SIZE_512_TYPE			0
 #define HNS3_BD_SIZE_1024_TYPE			1