On Thu, Oct 29, 2020 at 9:02 PM Andrew Lunn <and...@lunn.ch> wrote:
>
> On Thu, Oct 29, 2020 at 02:39:15PM +0800, DENG Qingfang wrote:
> > MT762x HW supports frame length up to 2048 (maximum length on GDM),
> > so allow setting MTU up to 2030.
> >
> > Signed-off-by: DENG Qingfang <dqf...@gmail.com>
> > ---
> >
> > I only tested this on MT7621, no sure if it is applicable for other SoCs
> > especially MT7628, which has an old IP.
> >
> > ---
> > drivers/net/ethernet/mediatek/mtk_eth_soc.c | 31 ++++++++++++++++++++-
> > drivers/net/ethernet/mediatek/mtk_eth_soc.h | 11 ++++++--
> > 2 files changed, 38 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > index 6d2d60675ffd..a0c56d9be1d5 100644
> > --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > @@ -353,7 +353,7 @@ static void mtk_mac_config(struct phylink_config
> > *config, unsigned int mode,
> > /* Setup gmac */
> > mcr_cur = mtk_r32(mac->hw, MTK_MAC_MCR(mac->id));
> > mcr_new = mcr_cur;
> > - mcr_new |= MAC_MCR_MAX_RX_1536 | MAC_MCR_IPG_CFG | MAC_MCR_FORCE_MODE
> > |
> > + mcr_new |= MAC_MCR_IPG_CFG | MAC_MCR_FORCE_MODE |
> > MAC_MCR_BACKOFF_EN | MAC_MCR_BACKPR_EN |
> > MAC_MCR_FORCE_LINK;
>
> Since you no longer set MAC_MCR_MAX_RX_1536, what does the hardware
> default to?
2'b00, i.e. 1518 bytes.
>
> > /* Only update control register when needed! */
> > @@ -2499,6 +2499,34 @@ static void mtk_uninit(struct net_device *dev)
> > mtk_rx_irq_disable(eth, ~0);
> > }
> >
> > +static int mtk_change_mtu(struct net_device *dev, int new_mtu)
> > +{
> > + struct mtk_mac *mac = netdev_priv(dev);
> > + u32 mcr_cur, mcr_new;
> > + int length;
> > +
> > + mcr_cur = mtk_r32(mac->hw, MTK_MAC_MCR(mac->id));
> > + mcr_new = mcr_cur & ~MAC_MCR_MAX_RX_LEN_MASK;
> > + length = new_mtu + MTK_RX_ETH_HLEN;
> > +
> > + if (length <= 1518)
> > + mcr_new |= MAC_MCR_MAX_RX_LEN(MAC_MCR_MAX_RX_LEN_1518);
> > + else if (length <= 1536)
> > + mcr_new |= MAC_MCR_MAX_RX_LEN(MAC_MCR_MAX_RX_LEN_1536);
> > + else if (length <= 1552)
> > + mcr_new |= MAC_MCR_MAX_RX_LEN(MAC_MCR_MAX_RX_LEN_1552);
> > + else
> > + mcr_new |= MAC_MCR_MAX_RX_LEN(MAC_MCR_MAX_RX_LEN_2048);
>
> You should have another if here, and return -EIVAL is the user asked
> for an MTU of 2049 of greater.
It is handled in net_device->max_mtu:
> eth->netdev[id]->max_mtu = MTK_MAX_RX_LENGTH - MTK_RX_ETH_HLEN;
As I tested:
> # ip link set eth0 mtu 2031
> RTNETLINK answers: Invalid argument
>
> Andrew
