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authorLinus Torvalds <torvalds@linux-foundation.org>2019-05-08 08:03:58 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2019-05-08 08:03:58 +0300
commit80f232121b69cc69a31ccb2b38c1665d770b0710 (patch)
tree106263eac4ff03b899df695e00dd11e593e74fe2 /Documentation/networking/dsa/bcm_sf2.rst
parent82efe439599439a5e1e225ce5740e6cfb777a7dd (diff)
parenta9e41a529681b38087c91ebc0bb91e12f510ca2d (diff)
downloadlinux-80f232121b69cc69a31ccb2b38c1665d770b0710.tar.xz
Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next
Pull networking updates from David Miller: "Highlights: 1) Support AES128-CCM ciphers in kTLS, from Vakul Garg. 2) Add fib_sync_mem to control the amount of dirty memory we allow to queue up between synchronize RCU calls, from David Ahern. 3) Make flow classifier more lockless, from Vlad Buslov. 4) Add PHY downshift support to aquantia driver, from Heiner Kallweit. 5) Add SKB cache for TCP rx and tx, from Eric Dumazet. This reduces contention on SLAB spinlocks in heavy RPC workloads. 6) Partial GSO offload support in XFRM, from Boris Pismenny. 7) Add fast link down support to ethtool, from Heiner Kallweit. 8) Use siphash for IP ID generator, from Eric Dumazet. 9) Pull nexthops even further out from ipv4/ipv6 routes and FIB entries, from David Ahern. 10) Move skb->xmit_more into a per-cpu variable, from Florian Westphal. 11) Improve eBPF verifier speed and increase maximum program size, from Alexei Starovoitov. 12) Eliminate per-bucket spinlocks in rhashtable, and instead use bit spinlocks. From Neil Brown. 13) Allow tunneling with GUE encap in ipvs, from Jacky Hu. 14) Improve link partner cap detection in generic PHY code, from Heiner Kallweit. 15) Add layer 2 encap support to bpf_skb_adjust_room(), from Alan Maguire. 16) Remove SKB list implementation assumptions in SCTP, your's truly. 17) Various cleanups, optimizations, and simplifications in r8169 driver. From Heiner Kallweit. 18) Add memory accounting on TX and RX path of SCTP, from Xin Long. 19) Switch PHY drivers over to use dynamic featue detection, from Heiner Kallweit. 20) Support flow steering without masking in dpaa2-eth, from Ioana Ciocoi. 21) Implement ndo_get_devlink_port in netdevsim driver, from Jiri Pirko. 22) Increase the strict parsing of current and future netlink attributes, also export such policies to userspace. From Johannes Berg. 23) Allow DSA tag drivers to be modular, from Andrew Lunn. 24) Remove legacy DSA probing support, also from Andrew Lunn. 25) Allow ll_temac driver to be used on non-x86 platforms, from Esben Haabendal. 26) Add a generic tracepoint for TX queue timeouts to ease debugging, from Cong Wang. 27) More indirect call optimizations, from Paolo Abeni" * git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next: (1763 commits) cxgb4: Fix error path in cxgb4_init_module net: phy: improve pause mode reporting in phy_print_status dt-bindings: net: Fix a typo in the phy-mode list for ethernet bindings net: macb: Change interrupt and napi enable order in open net: ll_temac: Improve error message on error IRQ net/sched: remove block pointer from common offload structure net: ethernet: support of_get_mac_address new ERR_PTR error net: usb: smsc: fix warning reported by kbuild test robot staging: octeon-ethernet: Fix of_get_mac_address ERR_PTR check net: dsa: support of_get_mac_address new ERR_PTR error net: dsa: sja1105: Fix status initialization in sja1105_get_ethtool_stats vrf: sit mtu should not be updated when vrf netdev is the link net: dsa: Fix error cleanup path in dsa_init_module l2tp: Fix possible NULL pointer dereference taprio: add null check on sched_nest to avoid potential null pointer dereference net: mvpp2: cls: fix less than zero check on a u32 variable net_sched: sch_fq: handle non connected flows net_sched: sch_fq: do not assume EDT packets are ordered net: hns3: use devm_kcalloc when allocating desc_cb net: hns3: some cleanup for struct hns3_enet_ring ...
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+=============================================
+Broadcom Starfighter 2 Ethernet switch driver
+=============================================
+
+Broadcom's Starfighter 2 Ethernet switch hardware block is commonly found and
+deployed in the following products:
+
+- xDSL gateways such as BCM63138
+- streaming/multimedia Set Top Box such as BCM7445
+- Cable Modem/residential gateways such as BCM7145/BCM3390
+
+The switch is typically deployed in a configuration involving between 5 to 13
+ports, offering a range of built-in and customizable interfaces:
+
+- single integrated Gigabit PHY
+- quad integrated Gigabit PHY
+- quad external Gigabit PHY w/ MDIO multiplexer
+- integrated MoCA PHY
+- several external MII/RevMII/GMII/RGMII interfaces
+
+The switch also supports specific congestion control features which allow MoCA
+fail-over not to lose packets during a MoCA role re-election, as well as out of
+band back-pressure to the host CPU network interface when downstream interfaces
+are connected at a lower speed.
+
+The switch hardware block is typically interfaced using MMIO accesses and
+contains a bunch of sub-blocks/registers:
+
+- ``SWITCH_CORE``: common switch registers
+- ``SWITCH_REG``: external interfaces switch register
+- ``SWITCH_MDIO``: external MDIO bus controller (there is another one in SWITCH_CORE,
+ which is used for indirect PHY accesses)
+- ``SWITCH_INDIR_RW``: 64-bits wide register helper block
+- ``SWITCH_INTRL2_0/1``: Level-2 interrupt controllers
+- ``SWITCH_ACB``: Admission control block
+- ``SWITCH_FCB``: Fail-over control block
+
+Implementation details
+======================
+
+The driver is located in ``drivers/net/dsa/bcm_sf2.c`` and is implemented as a DSA
+driver; see ``Documentation/networking/dsa/dsa.rst`` for details on the subsystem
+and what it provides.
+
+The SF2 switch is configured to enable a Broadcom specific 4-bytes switch tag
+which gets inserted by the switch for every packet forwarded to the CPU
+interface, conversely, the CPU network interface should insert a similar tag for
+packets entering the CPU port. The tag format is described in
+``net/dsa/tag_brcm.c``.
+
+Overall, the SF2 driver is a fairly regular DSA driver; there are a few
+specifics covered below.
+
+Device Tree probing
+-------------------
+
+The DSA platform device driver is probed using a specific compatible string
+provided in ``net/dsa/dsa.c``. The reason for that is because the DSA subsystem gets
+registered as a platform device driver currently. DSA will provide the needed
+device_node pointers which are then accessible by the switch driver setup
+function to setup resources such as register ranges and interrupts. This
+currently works very well because none of the of_* functions utilized by the
+driver require a struct device to be bound to a struct device_node, but things
+may change in the future.
+
+MDIO indirect accesses
+----------------------
+
+Due to a limitation in how Broadcom switches have been designed, external
+Broadcom switches connected to a SF2 require the use of the DSA slave MDIO bus
+in order to properly configure them. By default, the SF2 pseudo-PHY address, and
+an external switch pseudo-PHY address will both be snooping for incoming MDIO
+transactions, since they are at the same address (30), resulting in some kind of
+"double" programming. Using DSA, and setting ``ds->phys_mii_mask`` accordingly, we
+selectively divert reads and writes towards external Broadcom switches
+pseudo-PHY addresses. Newer revisions of the SF2 hardware have introduced a
+configurable pseudo-PHY address which circumvents the initial design limitation.
+
+Multimedia over CoAxial (MoCA) interfaces
+-----------------------------------------
+
+MoCA interfaces are fairly specific and require the use of a firmware blob which
+gets loaded onto the MoCA processor(s) for packet processing. The switch
+hardware contains logic which will assert/de-assert link states accordingly for
+the MoCA interface whenever the MoCA coaxial cable gets disconnected or the
+firmware gets reloaded. The SF2 driver relies on such events to properly set its
+MoCA interface carrier state and properly report this to the networking stack.
+
+The MoCA interfaces are supported using the PHY library's fixed PHY/emulated PHY
+device and the switch driver registers a ``fixed_link_update`` callback for such
+PHYs which reflects the link state obtained from the interrupt handler.
+
+
+Power Management
+----------------
+
+Whenever possible, the SF2 driver tries to minimize the overall switch power
+consumption by applying a combination of:
+
+- turning off internal buffers/memories
+- disabling packet processing logic
+- putting integrated PHYs in IDDQ/low-power
+- reducing the switch core clock based on the active port count
+- enabling and advertising EEE
+- turning off RGMII data processing logic when the link goes down
+
+Wake-on-LAN
+-----------
+
+Wake-on-LAN is currently implemented by utilizing the host processor Ethernet
+MAC controller wake-on logic. Whenever Wake-on-LAN is requested, an intersection
+between the user request and the supported host Ethernet interface WoL
+capabilities is done and the intersection result gets configured. During
+system-wide suspend/resume, only ports not participating in Wake-on-LAN are
+disabled.