Documentation: networking: add DPAA Ethernet document

Signed-off-by: Madalin Bucur <madalin.bucur@nxp.com>
Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/dpaa.txt

+The QorIQ DPAA Ethernet Driver
+==============================
+
+Authors:
+Madalin Bucur <madalin.bucur@nxp.com>
+Camelia Groza <camelia.groza@nxp.com>
+
+Contents
+========
+
+	- DPAA Ethernet Overview
+	- DPAA Ethernet Supported SoCs
+	- Configuring DPAA Ethernet in your kernel
+	- DPAA Ethernet Frame Processing
+	- DPAA Ethernet Features
+	- Debugging
+
+DPAA Ethernet Overview
+======================
+
+DPAA stands for Data Path Acceleration Architecture and it is a
+set of networking acceleration IPs that are available on several
+generations of SoCs, both on PowerPC and ARM64.
+
+The Freescale DPAA architecture consists of a series of hardware blocks
+that support Ethernet connectivity. The Ethernet driver depends upon the
+following drivers in the Linux kernel:
+
+ - Peripheral Access Memory Unit (PAMU) (* needed only for PPC platforms)
+    drivers/iommu/fsl_*
+ - Frame Manager (FMan)
+    drivers/net/ethernet/freescale/fman
+ - Queue Manager (QMan), Buffer Manager (BMan)
+    drivers/soc/fsl/qbman
+
+A simplified view of the dpaa_eth interfaces mapped to FMan MACs:
+
+  dpaa_eth       /eth0\     ...       /ethN\
+  driver        |      |             |      |
+  -------------   ----   -----------   ----   -------------
+       -Ports  / Tx  Rx \    ...    / Tx  Rx \
+  FMan        |          |         |          |
+       -MACs  |   MAC0   |         |   MACN   |
+             /   dtsec0   \  ...  /   dtsecN   \ (or tgec)
+            /              \     /              \(or memac)
+  ---------  --------------  ---  --------------  ---------
+      FMan, FMan Port, FMan SP, FMan MURAM drivers
+  ---------------------------------------------------------
+      FMan HW blocks: MURAM, MACs, Ports, SP
+  ---------------------------------------------------------
+
+The dpaa_eth relation to the QMan, BMan and FMan:
+              ________________________________
+  dpaa_eth   /            eth0                \
+  driver    /                                  \
+  ---------   -^-   -^-   -^-   ---    ---------
+  QMan driver / \   / \   / \  \   /  | BMan    |
+             |Rx | |Rx | |Tx | |Tx |  | driver  |
+  ---------  |Dfl| |Err| |Cnf| |FQs|  |         |
+  QMan HW    |FQ | |FQ | |FQs| |   |  |         |
+             /   \ /   \ /   \  \ /   |         |
+  ---------   ---   ---   ---   -v-    ---------
+            |        FMan QMI         |         |
+            | FMan HW       FMan BMI  | BMan HW |
+              -----------------------   --------
+
+where the acronyms used above (and in the code) are:
+DPAA = Data Path Acceleration Architecture
+FMan = DPAA Frame Manager
+QMan = DPAA Queue Manager
+BMan = DPAA Buffers Manager
+QMI = QMan interface in FMan
+BMI = BMan interface in FMan
+FMan SP = FMan Storage Profiles
+MURAM = Multi-user RAM in FMan
+FQ = QMan Frame Queue
+Rx Dfl FQ = default reception FQ
+Rx Err FQ = Rx error frames FQ
+Tx Cnf FQ = Tx confirmation FQs
+Tx FQs = transmission frame queues
+dtsec = datapath three speed Ethernet controller (10/100/1000 Mbps)
+tgec = ten gigabit Ethernet controller (10 Gbps)
+memac = multirate Ethernet MAC (10/100/1000/10000)
+
+DPAA Ethernet Supported SoCs
+============================
+
+The DPAA drivers enable the Ethernet controllers present on the following SoCs:
+
+# PPC
+P1023
+P2041
+P3041
+P4080
+P5020
+P5040
+T1023
+T1024
+T1040
+T1042
+T2080
+T4240
+B4860
+
+# ARM
+LS1043A
+LS1046A
+
+Configuring DPAA Ethernet in your kernel
+========================================
+
+To enable the DPAA Ethernet driver, the following Kconfig options are required:
+
+# common for arch/arm64 and arch/powerpc platforms
+CONFIG_FSL_DPAA=y
+CONFIG_FSL_FMAN=y
+CONFIG_FSL_DPAA_ETH=y
+CONFIG_FSL_XGMAC_MDIO=y
+
+# for arch/powerpc only
+CONFIG_FSL_PAMU=y
+
+# common options needed for the PHYs used on the RDBs
+CONFIG_VITESSE_PHY=y
+CONFIG_REALTEK_PHY=y
+CONFIG_AQUANTIA_PHY=y
+
+DPAA Ethernet Frame Processing
+==============================
+
+On Rx, buffers for the incoming frames are retrieved from one of the three
+existing buffers pools. The driver initializes and seeds these, each with
+buffers of different sizes: 1KB, 2KB and 4KB.
+
+On Tx, all transmitted frames are returned to the driver through Tx
+confirmation frame queues. The driver is then responsible for freeing the
+buffers. In order to do this properly, a backpointer is added to the buffer
+before transmission that points to the skb. When the buffer returns to the
+driver on a confirmation FQ, the skb can be correctly consumed.
+
+DPAA Ethernet Features
+======================
+
+Currently the DPAA Ethernet driver enables the basic features required for
+a Linux Ethernet driver. The support for advanced features will be added
+gradually.
+
+The driver has Rx and Tx checksum offloading for UDP and TCP. Currently the Rx
+checksum offload feature is enabled by default and cannot be controlled through
+ethtool.
+
+The driver has support for multiple prioritized Tx traffic classes. Priorities
+range from 0 (lowest) to 3 (highest). These are mapped to HW workqueues with
+strict priority levels. Each traffic class contains NR_CPU TX queues. By
+default, only one traffic class is enabled and the lowest priority Tx queues
+are used. Higher priority traffic classes can be enabled with the mqprio
+qdisc. For example, all four traffic classes are enabled on an interface with
+the following command. Furthermore, skb priority levels are mapped to traffic
+classes as follows:
+
+	* priorities 0 to 3 - traffic class 0 (low priority)
+	* priorities 4 to 7 - traffic class 1 (medium-low priority)
+	* priorities 8 to 11 - traffic class 2 (medium-high priority)
+	* priorities 12 to 15 - traffic class 3 (high priority)
+
+tc qdisc add dev <int> root handle 1: \
+	 mqprio num_tc 4 map 0 0 0 0 1 1 1 1 2 2 2 2 3 3 3 3 hw 1
+
+Debugging
+=========
+
+The following statistics are exported for each interface through ethtool:
+
+	- interrupt count per CPU
+	- Rx packets count per CPU
+	- Tx packets count per CPU
+	- Tx confirmed packets count per CPU
+	- Tx S/G frames count per CPU
+	- Tx error count per CPU
+	- Rx error count per CPU
+	- Rx error count per type
+	- congestion related statistics:
+		- congestion status
+		- time spent in congestion
+		- number of time the device entered congestion
+		- dropped packets count per cause
+
+The driver also exports the following information in sysfs:
+
+	- the FQ IDs for each FQ type
+	/sys/devices/platform/dpaa-ethernet.0/net/<int>/fqids
+
+	- the IDs of the buffer pools in use
+	/sys/devices/platform/dpaa-ethernet.0/net/<int>/bpids