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Subject[PATCH v2 2/9] staging: fsl-dpaa2/eth: Add Ethernet driver overview document
Date
Add a README file describing the driver architecture, components
and I/O interface.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@nxp.com>
---
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
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