doc: add LBK to Marvell OCTEON TX2 guide

Add LBK HW block abstraction details and the application
usage models.

This patch also updates missing DPI HW block to DPDK
subsystem mapping as well.

Signed-off-by: Jerin Jacob <jerinj@marvell.com>

diff --git a/doc/guides/platform/octeontx2.rst b/doc/guides/platform/octeontx2.rst
index f5be973..4194a43 100644 (file)
--- a/doc/guides/platform/octeontx2.rst
+++ b/doc/guides/platform/octeontx2.rst
@@ -61,6 +61,10 @@ DPDK subsystem.
    +---+-----+--------------------------------------------------------------+
    | 6 | TIM | rte_event_timer_adapter                                      |
    +---+-----+--------------------------------------------------------------+
+   | 7 | LBK | rte_ethdev                                                   |
+   +---+-----+--------------------------------------------------------------+
+   | 8 | DPI | rte_rawdev                                                   |
+   +---+-----+--------------------------------------------------------------+
 
 PF0 is called the administrative / admin function (AF) and has exclusive
 privileges to provision RVU functional block's LFs to each of the PF/VF.
@@ -82,6 +86,23 @@ resource provisioning example where,
 2. PFx-VF1 ethdev driver bound to the first DPDK application.
 3. PFy ethdev driver, PFy-VF0 ethdev driver, PFz eventdev driver, PFm-VF0 cryptodev driver bound to the second DPDK application.
 
+LBK HW Access
+-------------
+
+Loopback HW Unit (LBK) receives packets from NIX-RX and sends packets back to NIX-TX.
+The loopback block has N channels and contains data buffering that is shared across
+all channels. The LBK HW Unit is abstracted using ethdev subsystem, Where PF0's
+VFs are exposed as ethdev device and odd-even pairs of VFs are tied together,
+that is, packets sent on odd VF end up received on even VF and vice versa.
+This would enable HW accelerated means of communication between two domains
+where even VF bound to the first domain and odd VF bound to the second domain.
+
+Typical application usage models are,
+
+#. Communication between the Linux kernel and DPDK application.
+#. Exception path to Linux kernel from DPDK application as SW ``KNI`` replacement.
+#. Communication between two different DPDK applications.
+
 OCTEON TX2 packet flow
 ----------------------