Add a README file describing the driver architecture, components and I/O interface. Signed-off-by: Ioana Radulescu <ruxandra.radulescu@xxxxxxx> --- v2: no changes drivers/staging/fsl-dpaa2/ethernet/README | 186 ++++++++++++++++++++++++++++++ 1 file changed, 186 insertions(+) create mode 100644 drivers/staging/fsl-dpaa2/ethernet/README diff --git a/drivers/staging/fsl-dpaa2/ethernet/README b/drivers/staging/fsl-dpaa2/ethernet/README new file mode 100644 index 000000000000..410952ecf657 --- /dev/null +++ b/drivers/staging/fsl-dpaa2/ethernet/README @@ -0,0 +1,186 @@ +Freescale DPAA2 Ethernet driver +=============================== + +This file provides documentation for the Freescale DPAA2 Ethernet driver. + + +Contents +======== + Supported Platforms + Architecture Overview + Creating a Network Interface + Features & Offloads + + +Supported Platforms +=================== +This driver provides networking support for Freescale DPAA2 SoCs, e.g. +LS2080A, LS2088A, LS1088A. + + +Architecture Overview +===================== +Unlike regular NICs, in the DPAA2 architecture there is no single hardware block +representing network interfaces; instead, several separate hardware resources +concur to provide the networking functionality: + - network interfaces + - queues, channels + - buffer pools + - MAC/PHY + +All hardware resources are allocated and configured through the Management +Complex (MC) portals. MC abstracts most of these resources as DPAA2 objects +and exposes ABIs through which they can be configured and controlled. A few +hardware resources, like queues, do not have a corresponding MC object and +are treated as internal resources of other objects. + +For a more detailed description of the DPAA2 architecture and its object +abstractions see: + drivers/staging/fsl-mc/README.txt + +Each Linux net device is built on top of a Datapath Network Interface (DPNI) +object and uses Buffer Pools (DPBPs), I/O Portals (DPIOs) and Concentrators +(DPCONs). + +Configuration interface: + + ----------------------- + | DPAA2 Ethernet Driver | + ----------------------- + . . . + . . . + . . . . . . . . . . . . + . . . + . . . + ---------- ---------- ----------- + | DPBP API | | DPNI API | | DPCON API | + ---------- ---------- ----------- + . . . software +=========== . ========== . ============ . =================== + . . . hardware + ------------------------------------------ + | MC hardware portals | + ------------------------------------------ + . . . + . . . + ------ ------ ------- + | DPBP | | DPNI | | DPCON | + ------ ------ ------- + +The DPNIs are network interfaces without a direct one-on-one mapping to PHYs. +DPBPs represent hardware buffer pools. Packet I/O is performed in the context +of DPCON objects, using DPIO portals for managing and communicating with the +hardware resources. + +Datapath (I/O) interface: + + ----------------------------------------------- + | DPAA2 Ethernet Driver | + ----------------------------------------------- + | ^ ^ | | + | | | | | + enqueue| dequeue| data | dequeue| seed | + (Tx) | (Rx, TxC)| avail.| request| buffers| + | | notify| | | + | | | | | + V | | V V + ----------------------------------------------- + | DPIO Driver | + ----------------------------------------------- + | | | | | software + | | | | | ================ + | | | | | hardware + ----------------------------------------------- + | I/O hardware portals | + ----------------------------------------------- + | ^ ^ | | + | | | | | + | | | V | + V | ================ V + ---------------------- | ------------- + queues ---------------------- | | Buffer pool | + ---------------------- | ------------- + ======================= + Channel + +Datapath I/O (DPIO) portals provide enqueue and dequeue services, data +availability notifications and buffer pool management. DPIOs are shared between +all DPAA2 objects (and implicitly all DPAA2 kernel drivers) that work with data +frames, but must be affine to the CPUs for the purpose of traffic distribution. + +Frames are transmitted and received through hardware frame queues, which can be +grouped in channels for the purpose of hardware scheduling. The Ethernet driver +enqueues TX frames on egress queues and after transmission is complete a TX +confirmation frame is sent back to the CPU. + +When frames are available on ingress queues, a data availability notification +is sent to the CPU; notifications are raised per channel, so even if multiple +queues in the same channel have available frames, only one notification is sent. +After a channel fires a notification, is must be explicitly rearmed. + +Each network interface can have multiple Rx, Tx and confirmation queues affined +to CPUs, and one channel (DPCON) for each CPU that services at least one queue. +DPCONs are used to distribute ingress traffic to different CPUs via the cores' +affine DPIOs. + +The role of hardware buffer pools is storage of ingress frame data. Each network +interface has a privately owned buffer pool which it seeds with kernel allocated +buffers. + + +DPNIs are decoupled from PHYs; a DPNI can be connected to a PHY through a DPMAC +object or to another DPNI through an internal link, but the connection is +managed by MC and completely transparent to the Ethernet driver. + + --------- --------- --------- + | eth if1 | | eth if2 | | eth ifn | + --------- --------- --------- + . . . + . . . + . . . + --------------------------- + | DPAA2 Ethernet Driver | + --------------------------- + . . . + . . . + . . . + ------ ------ ------ ------- + | DPNI | | DPNI | | DPNI | | DPMAC |----+ + ------ ------ ------ ------- | + | | | | | + | | | | ----- + =========== ================== | PHY | + ----- + +Creating a Network Interface +============================ +A net device is created for each DPNI object probed on the MC bus. Each DPNI has +a number of properties which determine the network interface configuration +options and associated hardware resources. + +DPNI objects (and the other DPAA2 objects needed for a network interface) can be +added to a container on the MC bus in one of two ways: statically, through a +Datapath Layout Binary file (DPL) that is parsed by MC at boot time; or created +dynamically at runtime, via the DPAA2 objects APIs. + + +Features & Offloads +=================== +Hardware checksum offloading is supported for TCP and UDP over IPv4/6 frames. +The checksum offloads can be independently configured on RX and TX through +ethtool. + +Hardware offload of unicast and multicast MAC filtering is supported on the +ingress path and permanently enabled. + +Scatter-gather frames are supported on both RX and TX paths. On TX, SG support +is configurable via ethtool; on RX it is always enabled. + +The DPAA2 hardware can process jumbo Ethernet frames of up to 10K bytes. + +The Ethernet driver defines a static flow hashing scheme that distributes +traffic based on a 5-tuple key: src IP, dst IP, IP proto, L4 src port, +L4 dst port. No user configuration is supported for now. + +Hardware specific statistics for the network interface as well as some +non-standard driver stats can be consulted through ethtool -S option. -- 2.11.0 _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
