net: dsa: permit cross-chip bridging between all trees in the system
One way of utilizing DSA is by cascading switches which do not all have compatible taggers. Consider the following real-life topology: +---------------------------------------------------------------+ | LS1028A | | +------------------------------+ | | | DSA master for Felix | | | |(internal ENETC port 2: eno2))| | | +------------+------------------------------+-------------+ | | | Felix embedded L2 switch | | | | | | | | +--------------+ +--------------+ +--------------+ | | | | |DSA master for| |DSA master for| |DSA master for| | | | | | SJA1105 1 | | SJA1105 2 | | SJA1105 3 | | | | | |(Felix port 1)| |(Felix port 2)| |(Felix port 3)| | | +--+-+--------------+---+--------------+---+--------------+--+--+ +-----------------------+ +-----------------------+ +-----------------------+ | SJA1105 switch 1 | | SJA1105 switch 2 | | SJA1105 switch 3 | +-----+-----+-----+-----+ +-----+-----+-----+-----+ +-----+-----+-----+-----+ |sw1p0|sw1p1|sw1p2|sw1p3| |sw2p0|sw2p1|sw2p2|sw2p3| |sw3p0|sw3p1|sw3p2|sw3p3| +-----+-----+-----+-----+ +-----+-----+-----+-----+ +-----+-----+-----+-----+ The above can be described in the device tree as follows (obviously not complete): mscc_felix { dsa,member = <0 0>; ports { port@4 { ethernet = <&enetc_port2>; }; }; }; sja1105_switch1 { dsa,member = <1 1>; ports { port@4 { ethernet = <&mscc_felix_port1>; }; }; }; sja1105_switch2 { dsa,member = <2 2>; ports { port@4 { ethernet = <&mscc_felix_port2>; }; }; }; sja1105_switch3 { dsa,member = <3 3>; ports { port@4 { ethernet = <&mscc_felix_port3>; }; }; }; Basically we instantiate one DSA switch tree for every hardware switch in the system, but we still give them globally unique switch IDs (will come back to that later). Having 3 disjoint switch trees makes the tagger drivers "just work", because net devices are registered for the 3 Felix DSA master ports, and they are also DSA slave ports to the ENETC port. So packets received on the ENETC port are stripped of their stacked DSA tags one by one. Currently, hardware bridging between ports on the same sja1105 chip is possible, but switching between sja1105 ports on different chips is handled by the software bridge. This is fine, but we can do better. In fact, the dsa_8021q tag used by sja1105 is compatible with cascading. In other words, a sja1105 switch can correctly parse and route a packet containing a dsa_8021q tag. So if we could enable hardware bridging on the Felix DSA master ports, cross-chip bridging could be completely offloaded. Such as system would be used as follows: ip link add dev br0 type bridge && ip link set dev br0 up for port in sw0p0 sw0p1 sw0p2 sw0p3 \ sw1p0 sw1p1 sw1p2 sw1p3 \ sw2p0 sw2p1 sw2p2 sw2p3; do ip link set dev $port master br0 done The above makes switching between ports on the same row be performed in hardware, and between ports on different rows in software. Now assume the Felix switch ports are called swp0, swp1, swp2. By running the following extra commands: ip link add dev br1 type bridge && ip link set dev br1 up for port in swp0 swp1 swp2; do ip link set dev $port master br1 done the CPU no longer sees packets which traverse sja1105 switch boundaries and can be forwarded directly by Felix. The br1 bridge would not be used for any sort of traffic termination. For this to work, we need to give drivers an opportunity to listen for bridging events on DSA trees other than their own, and pass that other tree index as argument. I have made the assumption, for the moment, that the other existing DSA notifiers don't need to be broadcast to other trees. That assumption might turn out to be incorrect. But in the meantime, introduce a dsa_broadcast function, similar in purpose to dsa_port_notify, which is used only by the bridging notifiers. Signed-off-by: NVladimir Oltean <vladimir.oltean@nxp.com> Reviewed-by: NFlorian Fainelli <f.fainelli@gmail.com> Signed-off-by: NJakub Kicinski <kuba@kernel.org>
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