[PATCH V2 net-next] net: hns3: Add support to change MTU in HNS3 hardware

[Salil Mehta]

This patch adds the following support to the HNS3 driver:
1. Support to change the Maximum Transmission Unit of a
   of a port in the HNS NIC hardware .
2. Initializes the supported MTU range for the netdevice.

Signed-off-by: lipeng <lipeng...@huawei.com>
Signed-off-by: Salil Mehta <salil.me...@huawei.com>
---
PATCH V2: Addresses comments given by Andrew Lunn
          1. https://lkml.org/lkml/2017/8/18/282
PATCH V1: Initial Submit
---
 .../net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.c | 38 ++++++++++++++++++++++
 .../net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.h |  1 +
 2 files changed, 39 insertions(+)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.c 
b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.c
index e731f87..d905ea1 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.c
@@ -1278,11 +1278,46 @@ 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 -ENOTSUPP;
+
+       /* 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) {
+               if (hns3_nic_net_open(netdev)) {
+                       netdev_err(netdev, "MTU, couldnt up netdev again\n");
+                       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 +2787,9 @@ 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:
diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.h 
b/drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.h
index a6e8f15..7e87461 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3pf/hns3_enet.h
+++ b/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
-- 
2.7.4