Documentation: net: dsa: sja1105: Add info about supported traffic modes
This adds a table which illustrates what combinations of management / regular traffic work depending on the state the switch ports are in. Signed-off-by: Vladimir Oltean <olteanv@gmail.com> Reviewed-by: Florian Fainelli <f.fainelli@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -63,6 +63,38 @@ If that changed setting can be transmitted to the switch through the dynamic
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reconfiguration interface, it is; otherwise the switch is reset and
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reprogrammed with the updated static configuration.
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Traffic support
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===============
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The switches do not support switch tagging in hardware. But they do support
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customizing the TPID by which VLAN traffic is identified as such. The switch
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driver is leveraging ``CONFIG_NET_DSA_TAG_8021Q`` by requesting that special
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VLANs (with a custom TPID of ``ETH_P_EDSA`` instead of ``ETH_P_8021Q``) are
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installed on its ports when not in ``vlan_filtering`` mode. This does not
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interfere with the reception and transmission of real 802.1Q-tagged traffic,
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because the switch does no longer parse those packets as VLAN after the TPID
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change.
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The TPID is restored when ``vlan_filtering`` is requested by the user through
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the bridge layer, and general IP termination becomes no longer possible through
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the switch netdevices in this mode.
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The switches have two programmable filters for link-local destination MACs.
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These are used to trap BPDUs and PTP traffic to the master netdevice, and are
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further used to support STP and 1588 ordinary clock/boundary clock
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functionality.
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The following traffic modes are supported over the switch netdevices:
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+--------------------+------------+------------------+------------------+
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| | Standalone | Bridged with | Bridged with |
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| | ports | vlan_filtering 0 | vlan_filtering 1 |
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+====================+============+==================+==================+
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| Regular traffic | Yes | Yes | No (use master) |
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+--------------------+------------+------------------+------------------+
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| Management traffic | Yes | Yes | Yes |
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| (BPDU, PTP) | | | |
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+--------------------+------------+------------------+------------------+
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Switching features
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==================
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@ -92,6 +124,28 @@ that VLAN awareness is global at the switch level is that once a bridge with
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``vlan_filtering`` enslaves at least one switch port, the other un-bridged
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ports are no longer available for standalone traffic termination.
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Topology and loop detection through STP is supported.
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L2 FDB manipulation (add/delete/dump) is currently possible for the first
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generation devices. Aging time of FDB entries, as well as enabling fully static
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management (no address learning and no flooding of unknown traffic) is not yet
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configurable in the driver.
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A special comment about bridging with other netdevices (illustrated with an
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example):
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A board has eth0, eth1, swp0@eth1, swp1@eth1, swp2@eth1, swp3@eth1.
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The switch ports (swp0-3) are under br0.
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It is desired that eth0 is turned into another switched port that communicates
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with swp0-3.
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If br0 has vlan_filtering 0, then eth0 can simply be added to br0 with the
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intended results.
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If br0 has vlan_filtering 1, then a new br1 interface needs to be created that
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enslaves eth0 and eth1 (the DSA master of the switch ports). This is because in
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this mode, the switch ports beneath br0 are not capable of regular traffic, and
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are only used as a conduit for switchdev operations.
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Device Tree bindings and board design
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=====================================
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