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Diffstat (limited to 'Documentation/networking/dsa/bcm_sf2.txt')
| -rw-r--r-- | Documentation/networking/dsa/bcm_sf2.txt | 114 |
1 files changed, 0 insertions, 114 deletions
diff --git a/Documentation/networking/dsa/bcm_sf2.txt b/Documentation/networking/dsa/bcm_sf2.txt deleted file mode 100644 index eba3a2431e91..000000000000 --- a/Documentation/networking/dsa/bcm_sf2.txt +++ /dev/null @@ -1,114 +0,0 @@ -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.txt 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. |