Messages in this thread | | | Date | Tue, 7 Feb 2023 11:42:05 +0100 | Subject | Re: [PATCH net] net: ethernet: mtk_eth_soc: fix DSA TX tag hwaccel for switch port 0 | From | Felix Fietkau <> |
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On 07.02.23 11:30, Vladimir Oltean wrote: > Arınç reports that on his MT7621AT Unielec U7621-06 board and MT7623NI > Bananapi BPI-R2, packets received by the CPU over mt7530 switch port 0 > (of which this driver acts as the DSA master) are not processed > correctly by software. More precisely, they arrive without a DSA tag > (in packet or in the hwaccel area - skb_metadata_dst()), so DSA cannot > demux them towards the switch's interface for port 0. Traffic from other > ports receives a skb_metadata_dst() with the correct port and is demuxed > properly. > > Looking at mtk_poll_rx(), it becomes apparent that this driver uses the > skb vlan hwaccel area: > > union { > u32 vlan_all; > struct { > __be16 vlan_proto; > __u16 vlan_tci; > }; > }; > > as a temporary storage for the VLAN hwaccel tag, or the DSA hwaccel tag. > If this is a DSA master it's a DSA hwaccel tag, and finally clears up > the skb VLAN hwaccel header. > > I'm guessing that the problem is the (mis)use of API. > skb_vlan_tag_present() looks like this: > > #define skb_vlan_tag_present(__skb) (!!(__skb)->vlan_all) > > So if both vlan_proto and vlan_tci are zeroes, skb_vlan_tag_present() > returns precisely false. I don't know for sure what is the format of the > DSA hwaccel tag, but I surely know that lowermost 3 bits of vlan_proto > are 0 when receiving from port 0: > > unsigned int port = vlan_proto & GENMASK(2, 0); > > If the RX descriptor has no other bits set to non-zero values in > RX_DMA_VTAG, then the call to __vlan_hwaccel_put_tag() will not, in > fact, make the subsequent skb_vlan_tag_present() return true, because > it's implemented like this: > > static inline void __vlan_hwaccel_put_tag(struct sk_buff *skb, > __be16 vlan_proto, u16 vlan_tci) > { > skb->vlan_proto = vlan_proto; > skb->vlan_tci = vlan_tci; > } > > What we need to do to fix this problem (assuming this is the problem) is > to stop using skb->vlan_all as temporary storage for driver affairs, and > just create some local variables that serve the same purpose, but > hopefully better. Instead of calling skb_vlan_tag_present(), let's look > at a boolean has_hwaccel_tag which we set to true when the RX DMA > descriptors have something. Disambiguate based on netdev_uses_dsa() > whether this is a VLAN or DSA hwaccel tag, and only call > __vlan_hwaccel_put_tag() if we're certain it's a VLAN tag. > > Arınç confirms that the treatment works, so this validates the > assumption. > > Link: https://lore.kernel.org/netdev/704f3a72-fc9e-714a-db54-272e17612637@arinc9.com/ > Fixes: 2d7605a72906 ("net: ethernet: mtk_eth_soc: enable hardware DSA untagging") > Reported-by: Arınç ÜNAL <arinc.unal@arinc9.com> > Tested-by: Arınç ÜNAL <arinc.unal@arinc9.com> > Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com> Reviewed-by: Felix Fietkau <nbd@nbd.name>
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