| 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. |
