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Date: Thu, 16 Feb 2023 18:38:02 +0100
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Mengyuan Lou <mengyuanlou@...-swift.com>
CC: <netdev@...r.kernel.org>, <jiawenwu@...stnetic.com>,
Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH net-next] net: wangxun: Implement the ndo change mtu
interface
From: Mengyuan Lou <mengyuanlou@...-swift.com>
Date: Thu, 16 Feb 2023 16:44:13 +0800
> Add ngbe and txgbe ndo_change_mtu support.
>
> Signed-off-by: Mengyuan Lou <mengyuanlou@...-swift.com>
> ---
> drivers/net/ethernet/wangxun/libwx/wx_type.h | 2 +
> drivers/net/ethernet/wangxun/ngbe/ngbe_main.c | 38 ++++++++++++++++++-
> drivers/net/ethernet/wangxun/ngbe/ngbe_type.h | 1 -
> .../net/ethernet/wangxun/txgbe/txgbe_main.c | 38 ++++++++++++++++++-
> .../net/ethernet/wangxun/txgbe/txgbe_type.h | 1 -
> 5 files changed, 76 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/net/ethernet/wangxun/libwx/wx_type.h b/drivers/net/ethernet/wangxun/libwx/wx_type.h
> index 77d8d7f1707e..2b9efd13c500 100644
> --- a/drivers/net/ethernet/wangxun/libwx/wx_type.h
> +++ b/drivers/net/ethernet/wangxun/libwx/wx_type.h
> @@ -300,6 +300,8 @@
> #define WX_MAX_RXD 8192
> #define WX_MAX_TXD 8192
>
> +#define WX_MAX_JUMBO_FRAME_SIZE 9432 /* max payload 9414 */
Please use tabs.
> +
> /* Supported Rx Buffer Sizes */
> #define WX_RXBUFFER_256 256 /* Used for skb receive header */
> #define WX_RXBUFFER_2K 2048
> diff --git a/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c b/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c
> index 5b564d348c09..78bfaff02aad 100644
> --- a/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c
> +++ b/drivers/net/ethernet/wangxun/ngbe/ngbe_main.c
> @@ -361,6 +361,15 @@ static void ngbe_up(struct wx *wx)
> phy_start(wx->phydev);
> }
>
> +static void ngbe_reinit_locked(struct wx *wx)
> +{
> + /* prevent tx timeout */
> + netif_trans_update(wx->netdev);
Why doing this? Your driver/device can reload for longer than 5 seconds
(default Tx timeout) or...?
> + ngbe_down(wx);
> + wx_configure(wx);
> + ngbe_up(wx);
> +}
> +
> /**
> * ngbe_open - Called when a network interface is made active
> * @netdev: network interface device structure
> @@ -435,6 +444,32 @@ static int ngbe_close(struct net_device *netdev)
> return 0;
> }
>
> +/**
> + * ngbe_change_mtu - Change the Maximum Transfer Unit
> + * @netdev: network interface device structure
> + * @new_mtu: new value for maximum frame size
> + *
> + * Returns 0 on success, negative on failure
> + **/
> +static int ngbe_change_mtu(struct net_device *netdev, int new_mtu)
> +{
> + int max_frame = new_mtu + ETH_HLEN + ETH_FCS_LEN;
You must also account `2 * VLAN_HLEN`. The difference between MTU and
frame size is `ETH_HLEN + 2 * VLAN_HLEN + ETH_FCS_LEN`, i.e. 26 bytes.
...except for if your device doesn't handle VLANs, but I doubt so.
> + struct wx *wx = netdev_priv(netdev);
> +
> + if (max_frame > WX_MAX_JUMBO_FRAME_SIZE)
> + return -EINVAL;
(Andrew already said that...)
> +
> + netdev_info(netdev, "Changing MTU from %d to %d.\n",
> + netdev->mtu, new_mtu);
As Andrew already said, it's netdev_dbg() at most, but TBH I consider
this a development-time-only-debug-message that shouldn't go into the
release code.
> +
> + /* must set new MTU before calling down or up */
> + netdev->mtu = new_mtu;
If you look at the default implementation, you'll see that netdev->mtu
must now be accessed using READ_ONCE()/WRITE_ONCE(), so please change
accordingly. Otherwise there can be race around this field and you'll
get some unexpected results some day.
> + if (netif_running(netdev))
> + ngbe_reinit_locked(wx);
> +
> + return 0;
> +}
> +
> static void ngbe_dev_shutdown(struct pci_dev *pdev, bool *enable_wake)
> {
> struct wx *wx = pci_get_drvdata(pdev);
> @@ -470,6 +505,7 @@ static void ngbe_shutdown(struct pci_dev *pdev)
> static const struct net_device_ops ngbe_netdev_ops = {
> .ndo_open = ngbe_open,
> .ndo_stop = ngbe_close,
> + .ndo_change_mtu = ngbe_change_mtu,
> .ndo_start_xmit = wx_xmit_frame,
> .ndo_set_rx_mode = wx_set_rx_mode,
> .ndo_validate_addr = eth_validate_addr,
> @@ -562,7 +598,7 @@ static int ngbe_probe(struct pci_dev *pdev,
> netdev->priv_flags |= IFF_SUPP_NOFCS;
>
> netdev->min_mtu = ETH_MIN_MTU;
> - netdev->max_mtu = NGBE_MAX_JUMBO_FRAME_SIZE - (ETH_HLEN + ETH_FCS_LEN);
> + netdev->max_mtu = WX_MAX_JUMBO_FRAME_SIZE - (ETH_HLEN + ETH_FCS_LEN);
Same regarding frame size vs MTU.
Also, these braces are redundant.
>
> wx->bd_number = func_nums;
> /* setup the private structure */
> diff --git a/drivers/net/ethernet/wangxun/ngbe/ngbe_type.h b/drivers/net/ethernet/wangxun/ngbe/ngbe_type.h
> index a2351349785e..373d5af628cd 100644
> --- a/drivers/net/ethernet/wangxun/ngbe/ngbe_type.h
> +++ b/drivers/net/ethernet/wangxun/ngbe/ngbe_type.h
> @@ -137,7 +137,6 @@ enum NGBE_MSCA_CMD_value {
> #define NGBE_RX_PB_SIZE 42
> #define NGBE_MC_TBL_SIZE 128
> #define NGBE_TDB_PB_SZ (20 * 1024) /* 160KB Packet Buffer */
> -#define NGBE_MAX_JUMBO_FRAME_SIZE 9432 /* max payload 9414 */
>
> /* TX/RX descriptor defines */
> #define NGBE_DEFAULT_TXD 512 /* default ring size */
> diff --git a/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c b/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c
> index 6c0a98230557..0b09f982a2c8 100644
> --- a/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c
> +++ b/drivers/net/ethernet/wangxun/txgbe/txgbe_main.c
For the second driver, the questions are the same.
Thanks,
Olek
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