| 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 |
