| Message ID | 20231001203958.2995526-1-linus.walleij@linaro.org |
|---|---|
| State | Superseded |
| Delegated to: | Hauke Mehrtens |
| Headers | show |
| Series | bmips: bcm6368-enetsw: Bump max MTU to 1536 | expand |
On Sun, 1 Oct 2023 at 22:40, Linus Walleij <linus.walleij@linaro.org> wrote: > > The max MTU for this ethernet switch is 1536 bytes, not 1510 as it is The maximum *frame* size accepted is 1536 bytes, not MTU. A difference of 14 bytes. > right now. The available overhead is needed when using the DSA switch with > a cascaded DSA switch, which is something that exist in real products, > in this case the Inteno XG6846. > > Before this patch (on the lan1 DSA port in this case): > dsa_slave_change_mtu: master->max_mtu = 9724, dev->max_mtu = 10218, DSA overhead = 8 > dsa_slave_change_mtu: master = extsw, dev = lan1 > dsa_slave_change_mtu: master->max_mtu = 1510, dev->max_mtu = 9724, DSA overhead = 6 > dsa_slave_change_mtu: master = eth0, dev = extsw > dsa_slave_change_mtu new_master_mtu 1514 > mtu_limit 1510 > mdio_mux-0.1:00: nonfatal error -34 setting MTU to 1500 on port 0 > > After this patch the error is gone. Did you test this? As in verified that 1536 bytes long frames are correctly received and sent? > Cc: Álvaro Fernández Rojas <noltari@gmail.com> > Cc: Jonas Gorski <jonas.gorski@gmail.com> > Signed-off-by: Linus Walleij <linus.walleij@linaro.org> > --- > .../bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c b/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c > index 321e95dbbb3d..96f4c303a433 100644 > --- a/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c > +++ b/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c > @@ -24,6 +24,7 @@ > > /* MTU */ > #define ENETSW_TAG_SIZE (6 + VLAN_HLEN) > +#define ENETSW_MAX_MTU 1536 Again, not MTU. FRAME_LEN. > #define ENETSW_MTU_OVERHEAD (VLAN_ETH_HLEN + VLAN_HLEN + \ > ENETSW_TAG_SIZE) > #define ENETSW_FRAG_SIZE(x) (SKB_DATA_ALIGN(NET_SKB_PAD + x + \ > @@ -1067,7 +1068,7 @@ static int bcm6368_enetsw_probe(struct platform_device *pdev) > ndev->netdev_ops = &bcm6368_enetsw_ops; > ndev->min_mtu = ETH_ZLEN; > ndev->mtu = ETH_DATA_LEN + ENETSW_TAG_SIZE; > - ndev->max_mtu = ETH_DATA_LEN + ENETSW_TAG_SIZE; > + ndev->max_mtu = ENETSW_MAX_MTU; And here you would need to subtract the ETH_HLEN first, else you will allow 14 bytes too much. Also not sure if the ENETSW_TAG_SIZE should be still added here, as it is stripped on rx and added on tx on the cpu port. Best Regards, Jonas
On Sun, Oct 1, 2023 at 10:55 PM Jonas Gorski <jonas.gorski@gmail.com> wrote: > On Sun, 1 Oct 2023 at 22:40, Linus Walleij <linus.walleij@linaro.org> wrote: > > > > The max MTU for this ethernet switch is 1536 bytes, not 1510 as it is > > The maximum *frame* size accepted is 1536 bytes, not MTU. A difference > of 14 bytes. Darn. I sent a new version which is tested and hopefully better. Let's take it from there (it may have more/other bugs...) Yours, Linus Walleij
diff --git a/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c b/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c index 321e95dbbb3d..96f4c303a433 100644 --- a/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c +++ b/target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c @@ -24,6 +24,7 @@ /* MTU */ #define ENETSW_TAG_SIZE (6 + VLAN_HLEN) +#define ENETSW_MAX_MTU 1536 #define ENETSW_MTU_OVERHEAD (VLAN_ETH_HLEN + VLAN_HLEN + \ ENETSW_TAG_SIZE) #define ENETSW_FRAG_SIZE(x) (SKB_DATA_ALIGN(NET_SKB_PAD + x + \ @@ -1067,7 +1068,7 @@ static int bcm6368_enetsw_probe(struct platform_device *pdev) ndev->netdev_ops = &bcm6368_enetsw_ops; ndev->min_mtu = ETH_ZLEN; ndev->mtu = ETH_DATA_LEN + ENETSW_TAG_SIZE; - ndev->max_mtu = ETH_DATA_LEN + ENETSW_TAG_SIZE; + ndev->max_mtu = ENETSW_MAX_MTU; #if LINUX_VERSION_CODE >= KERNEL_VERSION(6,1,0) netif_napi_add(ndev, &priv->napi, bcm6368_enetsw_poll); #else
The max MTU for this ethernet switch is 1536 bytes, not 1510 as it is right now. The available overhead is needed when using the DSA switch with a cascaded DSA switch, which is something that exist in real products, in this case the Inteno XG6846. Before this patch (on the lan1 DSA port in this case): dsa_slave_change_mtu: master->max_mtu = 9724, dev->max_mtu = 10218, DSA overhead = 8 dsa_slave_change_mtu: master = extsw, dev = lan1 dsa_slave_change_mtu: master->max_mtu = 1510, dev->max_mtu = 9724, DSA overhead = 6 dsa_slave_change_mtu: master = eth0, dev = extsw dsa_slave_change_mtu new_master_mtu 1514 > mtu_limit 1510 mdio_mux-0.1:00: nonfatal error -34 setting MTU to 1500 on port 0 After this patch the error is gone. Cc: Álvaro Fernández Rojas <noltari@gmail.com> Cc: Jonas Gorski <jonas.gorski@gmail.com> Signed-off-by: Linus Walleij <linus.walleij@linaro.org> --- .../bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)