On 2017-06-09 22:32:15 +0200, Niklas Söderlund wrote:
> The hardware supports the MTU to be changed and the driver it self is
> somewhat prepared to support this. This patch hooks up the callbacks to
> be able to change the MTU from user-space.
>
> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@xxxxxxxxxxxx>
> Acked-by: Sergei Shtylyov <sergei.shtylyov@xxxxxxxxxxxxxxxxxx>
> ---
>
> Based on v4.12-rc1 and tested on Renesas R-Car Koelsch M2.
>
> Test procedure:
>
> 1. On host set MTU to something large (9000) was used for this test.
>
> 2. On target set MTU to something other then 1500, in this test the max
> MTU of 1978 is used.
>
> 3. Send ping with large payload and observe that it works.
>
> ping -M do -s 1954 <target>
>
> The reason for 1954 instead of 1982 is two fold:
>
> 1. On Linux (different on Mac IIRC) the ICMP/ping implementation
> doesn’t encapsulate the 28 byte ICMP (8) + IP (20).
> 2. The driver internally reserve 4 bytes of transmission buffer for
> an optional VLAN header (4). And since no VLAN is used in this
> setup the additional 4 bytes can carry data.
>
> 4. For extra verification the packet flow is inspected using tcpdump to
> verify that there is no packet fragmentation.
>
> * Changes since v1
> - Fix spelling mistake in comment, thanks Sergei!
> - Add Acked-by from Sergei.
>
> drivers/net/ethernet/renesas/sh_eth.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/drivers/net/ethernet/renesas/sh_eth.c b/drivers/net/ethernet/renesas/sh_eth.c
> index f68c4db656eda846..9c6e4025bfc9f5c5 100644
> --- a/drivers/net/ethernet/renesas/sh_eth.c
> +++ b/drivers/net/ethernet/renesas/sh_eth.c
> @@ -2558,6 +2558,17 @@ static int sh_eth_do_ioctl(struct net_device *ndev, struct ifreq *rq, int cmd)
> return phy_mii_ioctl(phydev, rq, cmd);
> }
>
> +static int sh_eth_change_mtu(struct net_device *dev, int new_mtu)
> +{
> + if (netif_running(dev))
> + return -EBUSY;
> +
> + dev->mtu = new_mtu;
> + netdev_update_features(dev);
> +
> + return 0;
> +}
> +
> /* For TSU_POSTn. Please refer to the manual about this (strange) bitfields */
> static void *sh_eth_tsu_get_post_reg_offset(struct sh_eth_private *mdp,
> int entry)
> @@ -3029,6 +3040,7 @@ static const struct net_device_ops sh_eth_netdev_ops = {
> .ndo_set_rx_mode = sh_eth_set_rx_mode,
> .ndo_tx_timeout = sh_eth_tx_timeout,
> .ndo_do_ioctl = sh_eth_do_ioctl,
> + .ndo_change_mtu = sh_eth_change_mtu,
> .ndo_validate_addr = eth_validate_addr,
> .ndo_set_mac_address = eth_mac_addr,
> };
> @@ -3043,6 +3055,7 @@ static const struct net_device_ops sh_eth_netdev_ops_tsu = {
> .ndo_vlan_rx_kill_vid = sh_eth_vlan_rx_kill_vid,
> .ndo_tx_timeout = sh_eth_tx_timeout,
> .ndo_do_ioctl = sh_eth_do_ioctl,
> + .ndo_change_mtu = sh_eth_change_mtu,
> .ndo_validate_addr = eth_validate_addr,
> .ndo_set_mac_address = eth_mac_addr,
> };
> @@ -3171,6 +3184,13 @@ static int sh_eth_drv_probe(struct platform_device *pdev)
> }
> sh_eth_set_default_cpu_data(mdp->cd);
>
> + /* User's manua states max MTU should be 2048 but due to the
s/manua/manual/
Do I need to resend or can this be fixed up when applying? Sorry for
this.
> + * alignment calculations in sh_eth_ring_init() the practical
> + * MTU is a bit less. Maybe this can be optimized some more.
> + */
> + ndev->max_mtu = 2000 - (ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN);
> + ndev->min_mtu = ETH_MIN_MTU;
> +
> /* set function */
> if (mdp->cd->tsu)
> ndev->netdev_ops = &sh_eth_netdev_ops_tsu;
> --
> 2.13.1
>
--
Regards,
Niklas Söderlund
