diff options
Diffstat (limited to 'Documentation/networking/dpaa.txt')
| -rw-r--r-- | Documentation/networking/dpaa.txt | 260 |
1 files changed, 260 insertions, 0 deletions
diff --git a/Documentation/networking/dpaa.txt b/Documentation/networking/dpaa.txt new file mode 100644 index 000000000..f88194f71 --- /dev/null +++ b/Documentation/networking/dpaa.txt @@ -0,0 +1,260 @@ +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 + - DPAA IRQ Affinity and Receive Side Scaling + - 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. Also, rx-flow-hash and rx-hashing was added. The addition of RSS +provides a big performance boost for the forwarding scenarios, allowing +different traffic flows received by one interface to be processed by different +CPUs in parallel. + +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 + +DPAA IRQ Affinity and Receive Side Scaling +========================================== + +Traffic coming on the DPAA Rx queues or on the DPAA Tx confirmation +queues is seen by the CPU as ingress traffic on a certain portal. +The DPAA QMan portal interrupts are affined each to a certain CPU. +The same portal interrupt services all the QMan portal consumers. + +By default the DPAA Ethernet driver enables RSS, making use of the +DPAA FMan Parser and Keygen blocks to distribute traffic on 128 +hardware frame queues using a hash on IP v4/v6 source and destination +and L4 source and destination ports, in present in the received frame. +When RSS is disabled, all traffic received by a certain interface is +received on the default Rx frame queue. The default DPAA Rx frame +queues are configured to put the received traffic into a pool channel +that allows any available CPU portal to dequeue the ingress traffic. +The default frame queues have the HOLDACTIVE option set, ensuring that +traffic bursts from a certain queue are serviced by the same CPU. +This ensures a very low rate of frame reordering. A drawback of this +is that only one CPU at a time can service the traffic received by a +certain interface when RSS is not enabled. + +To implement RSS, the DPAA Ethernet driver allocates an extra set of +128 Rx frame queues that are configured to dedicated channels, in a +round-robin manner. The mapping of the frame queues to CPUs is now +hardcoded, there is no indirection table to move traffic for a certain +FQ (hash result) to another CPU. The ingress traffic arriving on one +of these frame queues will arrive at the same portal and will always +be processed by the same CPU. This ensures intra-flow order preservation +and workload distribution for multiple traffic flows. + +RSS can be turned off for a certain interface using ethtool, i.e. + + # ethtool -N fm1-mac9 rx-flow-hash tcp4 "" + +To turn it back on, one needs to set rx-flow-hash for tcp4/6 or udp4/6: + + # ethtool -N fm1-mac9 rx-flow-hash udp4 sfdn + +There is no independent control for individual protocols, any command +run for one of tcp4|udp4|ah4|esp4|sctp4|tcp6|udp6|ah6|esp6|sctp6 is +going to control the rx-flow-hashing for all protocols on that interface. + +Besides using the FMan Keygen computed hash for spreading traffic on the +128 Rx FQs, the DPAA Ethernet driver also sets the skb hash value when +the NETIF_F_RXHASH feature is on (active by default). This can be turned +on or off through ethtool, i.e.: + + # ethtool -K fm1-mac9 rx-hashing off + # ethtool -k fm1-mac9 | grep hash + receive-hashing: off + # ethtool -K fm1-mac9 rx-hashing on + Actual changes: + receive-hashing: on + # ethtool -k fm1-mac9 | grep hash + receive-hashing: on + +Please note that Rx hashing depends upon the rx-flow-hashing being on +for that interface - turning off rx-flow-hashing will also disable the +rx-hashing (without ethtool reporting it as off as that depends on the +NETIF_F_RXHASH feature flag). + +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 |