6. OCTEON TX2 DMA Driver

OCTEON TX2 has an internal DMA unit which can be used by applications to initiate DMA transaction internally, from/to host when OCTEON TX2 operates in PCIe End Point mode. The DMA PF function supports 8 VFs corresponding to 8 DMA queues. Each DMA queue was exposed as a VF function when SRIOV enabled.

6.1. Features

This DMA PMD supports below 3 modes of memory transfers

  1. Internal - OCTEON TX2 DRAM to DRAM without core intervention
  2. Inbound - Host DRAM to OCTEON TX2 DRAM without host/OCTEON TX2 cores involvement
  3. Outbound - OCTEON TX2 DRAM to Host DRAM without host/OCTEON TX2 cores involvement

6.2. Prerequisites and Compilation procedure

See Marvell OCTEON TX2 Platform Guide for setup information.

6.3. Enabling logs

For enabling logs, use the following EAL parameter:

./your_dma_application <EAL args> --log-level=pmd.raw.octeontx2.dpi,<level>

Using pmd.raw.octeontx2.dpi as log matching criteria, all Event PMD logs can be enabled which are lower than logging level.

6.4. Initialization

The number of DMA VFs (queues) enabled can be controlled by setting sysfs entry, sriov_numvfs for the corresponding PF driver.

echo <num_vfs> > /sys/bus/pci/drivers/octeontx2-dpi/0000\:05\:00.0/sriov_numvfs

Once the required VFs are enabled, to be accessible from DPDK, VFs need to be bound to vfio-pci driver.

6.5. Device Setup

The OCTEON TX2 DPI DMA HW devices will need to be bound to a user-space IO driver for use. The script dpdk-devbind.py script included with DPDK can be used to view the state of the devices and to bind them to a suitable DPDK-supported kernel driver. When querying the status of the devices, they will appear under the category of “Misc (rawdev) devices”, i.e. the command dpdk-devbind.py --status-dev misc can be used to see the state of those devices alone.

6.6. Device Configuration

Configuring DMA rawdev device is done using the rte_rawdev_configure() API, which takes the mempool as parameter. PMD uses this pool to submit DMA commands to HW.

The following code shows how the device is configured

struct dpi_rawdev_conf_s conf = {0};
struct rte_rawdev_info rdev_info = {.dev_private = &conf};

conf.chunk_pool = (void *)rte_mempool_create_empty(...);
rte_mempool_set_ops_byname(conf.chunk_pool, rte_mbuf_platform_mempool_ops(), NULL);
rte_mempool_populate_default(conf.chunk_pool);

rte_rawdev_configure(dev_id, (rte_rawdev_obj_t)&rdev_info, sizeof(conf));

6.7. Performing Data Transfer

To perform data transfer using OCTEON TX2 DMA rawdev devices use standard rte_rawdev_enqueue_buffers() and rte_rawdev_dequeue_buffers() APIs.

6.8. Self test

On EAL initialization, dma devices will be probed and populated into the raw devices. The rawdev ID of the device can be obtained using

  • Invoke rte_rawdev_get_dev_id("DPI:x") from the application where x is the VF device’s bus id specified in “bus:device.func” format. Use this index for further rawdev function calls.
  • This PMD supports driver self test, to test DMA internal mode from test application one can directly calls rte_rawdev_selftest(rte_rawdev_get_dev_id("DPI:x"))