Lines Matching +full:dsa +full:- +full:specific
5 This document describes the **Distributed Switch Architecture (DSA)** subsystem
22 An Ethernet switch is typically comprised of multiple front-panel ports, and one
23 or more CPU or management port. The DSA subsystem currently relies on the
27 gateways, or even top-of-the rack switches. This host Ethernet controller will
28 be later referred to as "master" and "cpu" in DSA terminology and code.
30 The D in DSA stands for Distributed, because the subsystem has been designed
32 using upstream and downstream Ethernet links between switches. These specific
33 ports are referred to as "dsa" ports in DSA terminology and code. A collection
36 For each front-panel port, DSA will create specialized network devices which are
37 used as controlling and data-flowing endpoints for use by the Linux networking
39 interfaces in DSA terminology and code.
41 The ideal case for using DSA is when an Ethernet switch supports a "switch tag"
42 which is a hardware feature making the switch insert a specific tag for each
43 Ethernet frames it received to/from specific ports to help the management
46 - what port is this frame coming from
47 - what was the reason why this frame got forwarded
48 - how to send CPU originated traffic to specific ports
52 on Port-based VLAN IDs).
54 Note that DSA does not currently create network interfaces for the "cpu" and
55 "dsa" ports because:
57 - the "cpu" port is the Ethernet switch facing side of the management
61 - the "dsa" port(s) are just conduits between two or more switches, and as such
63 downstream, or the top-most upstream interface makes sense with that model
66 ------------------------
68 DSA currently supports 5 different tagging protocols, and a tag-less mode as
71 - ``net/dsa/tag_trailer.c``: Marvell's 4 trailer tag mode (legacy)
72 - ``net/dsa/tag_dsa.c``: Marvell's original DSA tag
73 - ``net/dsa/tag_edsa.c``: Marvell's enhanced DSA tag
74 - ``net/dsa/tag_brcm.c``: Broadcom's 4 bytes tag
75 - ``net/dsa/tag_qca.c``: Qualcomm's 2 bytes tag
77 The exact format of the tag protocol is vendor specific, but in general, they
80 - identifies which port the Ethernet frame came from/should be sent to
81 - provides a reason why this frame was forwarded to the management interface
84 ----------------------
88 know whether DSA is enabled (e.g.: to enable/disable specific offload features),
89 but the DSA subsystem has been proven to work with industry standard drivers:
96 ----------------------
98 When a master netdev is used with DSA, a small hook is placed in the
99 networking stack is in order to have the DSA subsystem process the Ethernet
100 switch specific tagging protocol. DSA accomplishes this by registering a
101 specific (and fake) Ethernet type (later becoming ``skb->protocol``) with the
109 - receive function is invoked
110 - basic packet processing is done: getting length, status etc.
111 - packet is prepared to be processed by the Ethernet layer by calling
117 if (dev->dsa_ptr != NULL)
118 -> skb->protocol = ETH_P_XDSA
123 -> iterate over registered packet_type
124 -> invoke handler for ETH_P_XDSA, calls dsa_switch_rcv()
126 4. net/dsa/dsa.c::
128 -> dsa_switch_rcv()
129 -> invoke switch tag specific protocol handler in 'net/dsa/tag_*.c'
131 5. net/dsa/tag_*.c:
133 - inspect and strip switch tag protocol to determine originating port
134 - locate per-port network device
135 - invoke ``eth_type_trans()`` with the DSA slave network device
136 - invoked ``netif_receive_skb()``
138 Past this point, the DSA slave network devices get delivered regular Ethernet
142 ---------------------
144 Slave network devices created by DSA are stacked on top of their master network
146 controlling and data-flowing end-point for each front-panel port of the switch.
149 - insert/remove the switch tag protocol (if it exists) when sending traffic
150 to/from specific switch ports
151 - query the switch for ethtool operations: statistics, link state,
152 Wake-on-LAN, register dumps...
153 - external/internal PHY management: link, auto-negotiation etc.
156 pointers which allow DSA to introduce a level of layering between the networking
159 Upon frame transmission from these slave network devices, DSA will look up which
161 invoke a specific transmit routine which takes care of adding the relevant
170 ------------------------
172 Summarized, this is basically how DSA looks like from a network device
176 |---------------------------
178 ----------------------------
183 |--------------------------------------------|
185 |--------------------------------------------|
187 |-------| |-------| |-------|
189 |-------| |-------| |-------|
194 --------------
196 In order to be able to read to/from a switch PHY built into it, DSA creates a
197 slave MDIO bus which allows a specific switch driver to divert and intercept
198 MDIO reads/writes towards specific PHY addresses. In most MDIO-connected
201 library and/or to return link status, link partner pages, auto-negotiation
210 ---------------
212 DSA data structures are defined in ``include/net/dsa.h`` as well as
213 ``net/dsa/dsa_priv.h``:
215 - ``dsa_chip_data``: platform data configuration for a given switch device,
220 - ``dsa_platform_data``: platform device configuration data which can reference
225 - ``dsa_switch_tree``: structure assigned to the master network device under
232 - ``dsa_switch``: structure describing a switch device in the tree, referencing
236 - ``dsa_switch_ops``: structure referencing function pointers, see below for a
243 -----------------------------------------
245 DSA currently limits the number of maximum switches within a tree to 4
250 Lack of CPU/DSA network devices
251 -------------------------------
253 DSA does not currently create slave network devices for the CPU or DSA ports, as
256 - inability to fetch switch CPU port statistics counters using ethtool, which
259 - inability to configure the CPU port link parameters based on the Ethernet
262 - inability to configure specific VLAN IDs / trunking VLANs between switches
265 Common pitfalls using DSA setups
266 --------------------------------
268 Once a master network device is configured to use DSA (dev->dsa_ptr becomes
269 non-NULL), and the switch behind it expects a tagging protocol, this network
283 DSA currently leverages the following subsystems:
285 - MDIO/PHY library: ``drivers/net/phy/phy.c``, ``mdio_bus.c``
286 - Switchdev:``net/switchdev/*``
287 - Device Tree for various of_* functions
290 ----------------
292 Slave network devices exposed by DSA may or may not be interfacing with PHY
293 devices (``struct phy_device`` as defined in ``include/linux/phy.h)``, but the DSA
296 - internal PHY devices, built into the Ethernet switch hardware
297 - external PHY devices, connected via an internal or external MDIO bus
298 - internal PHY devices, connected via an internal MDIO bus
299 - special, non-autonegotiated or non MDIO-managed PHY devices: SFPs, MoCA; a.k.a
305 - if Device Tree is used, the PHY device is looked up using the standard
306 "phy-handle" property, if found, this PHY device is created and registered
309 - if Device Tree is used, and the PHY device is "fixed", that is, conforms to
310 the definition of a non-MDIO managed PHY as defined in
311 ``Documentation/devicetree/bindings/net/fixed-link.txt``, the PHY is registered
314 - finally, if the PHY is built into the switch, as is very common with
316 by DSA
320 ---------
322 DSA directly utilizes SWITCHDEV when interfacing with the bridge layer, and
324 of per-port slave network devices. Since DSA primarily deals with
325 MDIO-connected switches, although not exclusively, SWITCHDEV's
327 checks whether the operation is supported by the DSA switch driver, and a commit
330 As of today, the only SWITCHDEV objects supported by DSA are the FDB and VLAN
334 -----------
336 DSA features a standardized binding which is documented in
337 ``Documentation/devicetree/bindings/net/dsa/dsa.txt``. PHY/MDIO library helper
339 per-port PHY specific details: interface connection, MDIO bus location etc..
344 DSA switch drivers need to implement a dsa_switch_ops structure which will
350 Unless requested differently by setting the priv_size member accordingly, DSA
354 --------------------
356 - ``tag_protocol``: this is to indicate what kind of tagging protocol is supported,
359 - ``probe``: probe routine which will be invoked by the DSA platform device upon
362 the switch pseudo-PHY and return whether this is a supported device. For other
363 buses, return a non-NULL string
365 - ``setup``: setup function for the switch, this function is responsible for setting
370 a Port-based VLAN ID for each port and allowing only the CPU port and the
371 specific port to be in the forwarding vector. Ports that are unused by the
379 -------------------------------
381 - ``get_phy_flags``: Some switches are interfaced to various kinds of Ethernet PHYs,
384 should return a 32-bits bitmask of "flags", that is private between the switch
387 - ``phy_read``: Function invoked by the DSA slave MDIO bus when attempting to read
390 status, auto-negotiation results, link partner pages etc..
392 - ``phy_write``: Function invoked by the DSA slave MDIO bus when attempting to write
396 - ``adjust_link``: Function invoked by the PHY library when a slave network device
401 - ``fixed_link_update``: Function invoked by the PHY library, and specifically by
403 not be auto-negotiated, or obtained by reading the PHY registers through MDIO.
404 This is particularly useful for specific kinds of hardware such as QSGMII,
405 MoCA or other kinds of non-MDIO managed PHYs where out of band link
409 ------------------
411 - ``get_strings``: ethtool function used to query the driver's strings, will
414 - ``get_ethtool_stats``: ethtool function used to query per-port statistics and
415 return their values. DSA overlays slave network devices general statistics:
416 RX/TX counters from the network device, with switch driver specific statistics
419 - ``get_sset_count``: ethtool function used to query the number of statistics items
421 - ``get_wol``: ethtool function used to obtain Wake-on-LAN settings per-port, this
423 Wake-on-LAN settings if this interface needs to participate in Wake-on-LAN
425 - ``set_wol``: ethtool function used to configure Wake-on-LAN settings per-port,
428 - ``set_eee``: ethtool function which is used to configure a switch port EEE (Green
431 controller and data-processing logic
433 - ``get_eee``: ethtool function which is used to query a switch port EEE settings,
435 and data-processing logic as well as query the PHY for its currently configured
438 - ``get_eeprom_len``: ethtool function returning for a given switch the EEPROM
441 - ``get_eeprom``: ethtool function returning for a given switch the EEPROM contents
443 - ``set_eeprom``: ethtool function writing specified data to a given switch EEPROM
445 - ``get_regs_len``: ethtool function returning the register length for a given
448 - ``get_regs``: ethtool function returning the Ethernet switch internal register
449 contents. This function might require user-land code in ethtool to
450 pretty-print register values and registers
453 ----------------
455 - ``suspend``: function invoked by the DSA platform device when the system goes to
457 participating in Wake-on-LAN active as well as additional wake-up logic if
460 - ``resume``: function invoked by the DSA platform device when the system resumes,
461 should resume all Ethernet switch activities and re-configure the switch to be
464 - ``port_enable``: function invoked by the DSA slave network device ndo_open
466 fully enabling a given switch port. DSA takes care of marking the port with
470 - ``port_disable``: function invoked by the DSA slave network device ndo_close
472 fully disabling a given switch port. DSA takes care of marking the port with
477 ------------
479 - ``port_bridge_join``: bridge layer function invoked when a given switch port is
484 - ``port_bridge_leave``: bridge layer function invoked when a given switch port is
491 - ``port_stp_state_set``: bridge layer function invoked when a given switch port STP
498 ---------------------
500 - ``port_vlan_filtering``: bridge layer function invoked when the bridge gets
501 configured for turning on or off VLAN filtering. If nothing specific needs to
510 - ``port_vlan_prepare``: bridge layer function invoked when the bridge prepares the
512 by the hardware, this function should return ``-EOPNOTSUPP`` to inform the bridge
516 - ``port_vlan_add``: bridge layer function invoked when a VLAN is configured
519 - ``port_vlan_del``: bridge layer function invoked when a VLAN is removed from the
522 - ``port_vlan_dump``: bridge layer function invoked with a switchdev callback
526 - ``port_fdb_add``: bridge layer function invoked when the bridge wants to install a
530 function should return ``-EOPNOTSUPP`` to inform the bridge code to fallback to
534 of DSA, would be its port-based VLAN, used by the associated bridge device.
536 - ``port_fdb_del``: bridge layer function invoked when the bridge wants to remove a
541 - ``port_fdb_dump``: bridge layer function invoked with a switchdev callback
545 - ``port_mdb_prepare``: bridge layer function invoked when the bridge prepares the
547 this function should return ``-EOPNOTSUPP`` to inform the bridge code to fallback
551 - ``port_mdb_add``: bridge layer function invoked when the bridge wants to install
557 of DSA, would be its port-based VLAN, used by the associated bridge device.
559 - ``port_mdb_del``: bridge layer function invoked when the bridge wants to remove a
564 - ``port_mdb_dump``: bridge layer function invoked with a switchdev callback
571 Making SWITCHDEV and DSA converge towards an unified codebase
572 -------------------------------------------------------------
576 the other DSA enforces a fairly strict device driver model, and deals with most
577 of the switch specific. At some point we should envision a merger between these
581 --------------------
583 - making the number of ports fully dynamic and not dependent on ``DSA_MAX_PORTS``
584 - allowing more than one CPU/management interface:
586 - porting more drivers from other vendors: