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Documentation: net: dsa: sja1105: Add info about supported traffic modes

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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>
This commit is contained in:
Vladimir Oltean 2019-05-05 13:19:29 +03:00 committed by David S. Miller
parent 640f763f98
commit 0a58d471de
1 changed files with 54 additions and 0 deletions
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54
Documentation/networking/dsa/sja1105.rst
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@ -63,6 +63,38 @@ If that changed setting can be transmitted to the switch through the dynamic
reconfiguration interface, it is; otherwise the switch is reset and
reprogrammed with the updated static configuration.
Traffic support
===============
The switches do not support switch tagging in hardware. But they do support
customizing the TPID by which VLAN traffic is identified as such. The switch
driver is leveraging ``CONFIG_NET_DSA_TAG_8021Q`` by requesting that special
VLANs (with a custom TPID of ``ETH_P_EDSA`` instead of ``ETH_P_8021Q``) are
installed on its ports when not in ``vlan_filtering`` mode. This does not
interfere with the reception and transmission of real 802.1Q-tagged traffic,
because the switch does no longer parse those packets as VLAN after the TPID
change.
The TPID is restored when ``vlan_filtering`` is requested by the user through
the bridge layer, and general IP termination becomes no longer possible through
the switch netdevices in this mode.
The switches have two programmable filters for link-local destination MACs.
These are used to trap BPDUs and PTP traffic to the master netdevice, and are
further used to support STP and 1588 ordinary clock/boundary clock
functionality.
The following traffic modes are supported over the switch netdevices:
+--------------------+------------+------------------+------------------+
| | Standalone | Bridged with | Bridged with |
| | ports | vlan_filtering 0 | vlan_filtering 1 |
+====================+============+==================+==================+
| Regular traffic | Yes | Yes | No (use master) |
+--------------------+------------+------------------+------------------+
| Management traffic | Yes | Yes | Yes |
| (BPDU, PTP) | | | |
+--------------------+------------+------------------+------------------+
Switching features
==================
@ -92,6 +124,28 @@ that VLAN awareness is global at the switch level is that once a bridge with
``vlan_filtering`` enslaves at least one switch port, the other un-bridged
ports are no longer available for standalone traffic termination.
Topology and loop detection through STP is supported.
L2 FDB manipulation (add/delete/dump) is currently possible for the first
generation devices. Aging time of FDB entries, as well as enabling fully static
management (no address learning and no flooding of unknown traffic) is not yet
configurable in the driver.
A special comment about bridging with other netdevices (illustrated with an
example):
A board has eth0, eth1, swp0@eth1, swp1@eth1, swp2@eth1, swp3@eth1.
The switch ports (swp0-3) are under br0.
It is desired that eth0 is turned into another switched port that communicates
with swp0-3.
If br0 has vlan_filtering 0, then eth0 can simply be added to br0 with the
intended results.
If br0 has vlan_filtering 1, then a new br1 interface needs to be created that
enslaves eth0 and eth1 (the DSA master of the switch ports). This is because in
this mode, the switch ports beneath br0 are not capable of regular traffic, and
are only used as a conduit for switchdev operations.
Device Tree bindings and board design
=====================================