.. SPDX-License-Identifier: BSD-3-Clause
   Copyright(c) 2021 Marvell.

Marvell cnxk SSO Eventdev Driver
================================

The SSO PMD (**librte_event_cnxk**) and provides poll mode
eventdev driver support for the inbuilt event device found in the
**Marvell OCTEON cnxk** SoC family.

More information about OCTEON cnxk SoC can be found at `Marvell Official Website
<https://www.marvell.com/embedded-processors/infrastructure-processors/>`_.

Supported OCTEON cnxk SoCs
--------------------------

- CN9XX
- CN10XX
- CN20XX

Features
--------

Features of the OCTEON cnxk SSO PMD are:

- 256 Event queues
- 26 (dual) and 52 (single) Event ports on CN9XX
- 52 Event ports on CN10XX
- HW event scheduler
- Supports 1M flows per event queue
- Flow based event pipelining
- Flow pinning support in flow based event pipelining
- Queue based event pipelining
- Supports ATOMIC, ORDERED, PARALLEL schedule types per flow
- Event scheduling QoS based on event queue priority
- Open system with configurable amount of outstanding events limited only by
  DRAM
- HW accelerated dequeue timeout support to enable power management
- HW managed event timers support through TIM, with high precision and
  time granularity of 2.5us on CN9K and 1us on CN10K/CN20K.
- Up to 256 TIM rings a.k.a event timer adapters.
- Up to 8 rings traversed in parallel.
- HW managed packets enqueued from ethdev to eventdev exposed through event eth
  RX adapter.
- N:1 ethernet device Rx queue to Event queue mapping.
- Lockfree Tx from event eth Tx adapter using ``RTE_ETH_TX_OFFLOAD_MT_LOCKFREE``
  capability while maintaining receive packet order.
- Full Rx/Tx offload support defined through ethdev queue configuration.
- HW managed event vectorization on CN10K/CN20K for packets enqueued from ethdev
  to eventdev configurable per each Rx queue in Rx adapter.
- Event vector transmission via Tx adapter.
- Up to 2 event link profiles.

Prerequisites and Compilation procedure
---------------------------------------

   See :doc:`../platform/cnxk` for setup information.


Runtime Config Options
----------------------

- ``Maximum number of in-flight events`` (default ``8192``)

  In **Marvell OCTEON cnxk** the max number of in-flight events are only limited
  by DRAM size, the ``xae_cnt`` devargs parameter is introduced to provide
  upper limit for in-flight events.

  For example::

    -a 0002:0e:00.0,xae_cnt=16384

- ``CN9K Getwork mode``

  CN9K ``single_ws`` devargs parameter is introduced to select single workslot
  mode in SSO and disable the default dual workslot mode.

  For example::

    -a 0002:0e:00.0,single_ws=1

- ``Event Group QoS support``

  SSO GGRPs i.e. queue uses DRAM & SRAM buffers to hold in-flight
  events. By default the buffers are assigned to the SSO GGRPs to
  satisfy minimum HW requirements. SSO is free to assign the remaining
  buffers to GGRPs based on a preconfigured threshold.
  We can control the QoS of SSO GGRP by modifying the above mentioned
  thresholds. GGRPs that have higher importance can be assigned higher
  thresholds than the rest. The dictionary format is as follows
  [Qx-TAQ-IAQ][Qz-TAQ-IAQ] expressed in percentages, 0 represents default.

  For example::

    -a 0002:0e:00.0,qos=[1-50-50]

- ``CN10K/CN20K WQE stashing support``

  CN10K/CN20K supports stashing the scheduled WQE carried by `rte_event` to the
  cores L2 Dcache. The number of cache lines to be stashed and the offset
  is configurable per HWGRP i.e. event queue. The dictionary format is as
  follows `[Qx|stash_offset|stash_length]` here the stash offset can be
  a negative integer.
  By default, stashing is enabled on queues which have been connected to
  Rx adapter. Both MBUF and NIX_RX_WQE_HDR + NIX_RX_PARSE_S are stashed.

  For example::

    For stashing mbuf on queue 0 and mbuf + headroom on queue 1
    -a 0002:0e:00.0,stash="[0|-1|1][1|-1|2]"

- ``Force Rx Back pressure``

   Force Rx back pressure when same mempool is used across ethernet device
   connected to event device.

   For example::

      -a 0002:0e:00.0,force_rx_bp=1

- ``TIM disable NPA``

  By default chunks are allocated from NPA then TIM can automatically free
  them when traversing the list of chunks. The ``tim_disable_npa`` devargs
  parameter disables NPA and uses software mempool to manage chunks

  For example::

    -a 0002:0e:00.0,tim_disable_npa=1

- ``TIM modify chunk slots``

  The ``tim_chnk_slots`` devargs can be used to modify number of chunk slots.
  Chunks are used to store event timers, a chunk can be visualised as an array
  where the last element points to the next chunk and rest of them are used to
  store events. TIM traverses the list of chunks and enqueues the event timers
  to SSO. The default value is 255 and the max value is 4095.

  For example::

    -a 0002:0e:00.0,tim_chnk_slots=1023

- ``TIM enable arm/cancel statistics``

  The ``tim_stats_ena`` devargs can be used to enable arm and cancel stats of
  event timer adapter.

  For example::

    -a 0002:0e:00.0,tim_stats_ena=1

- ``TIM limit max rings reserved``

  The ``tim_rings_lmt`` devargs can be used to limit the max number of TIM
  rings i.e. event timer adapter reserved on probe. Since, TIM rings are HW
  resources we can avoid starving other applications by not grabbing all the
  rings.

  For example::

    -a 0002:0e:00.0,tim_rings_lmt=5

- ``TIM ring control internal parameters``

  When using multiple TIM rings the ``tim_ring_ctl`` devargs can be used to
  control each TIM rings internal parameters uniquely. The following dict
  format is expected [ring-chnk_slots-disable_npa-stats_ena]. 0 represents
  default values.

  For Example::

    -a 0002:0e:00.0,tim_ring_ctl=[2-1023-1-0]

- ``TIM external clock frequency``

  The ``tim_eclk_freq`` devagrs can be used to pass external clock frequencies
  when external clock source is selected.

  External clock frequencies are mapped as follows::

    RTE_EVENT_TIMER_ADAPTER_EXT_CLK0 = TIM_CLK_SRC_10NS,
    RTE_EVENT_TIMER_ADAPTER_EXT_CLK1 = TIM_CLK_SRC_GPIO,
    RTE_EVENT_TIMER_ADAPTER_EXT_CLK2 = TIM_CLK_SRC_PTP,
    RTE_EVENT_TIMER_ADAPTER_EXT_CLK3 = TIM_CLK_SRC_SYNCE

  The order of frequencies supplied to device args should be GPIO-PTP-SYNCE.

  For Example::

    -a 0002:0e:00.0,tim_eclk_freq=122880000-1000000000-0

Power Saving on CN10K/CN20K
---------------------------

ARM cores can additionally use WFE when polling for transactions on SSO bus
to save power i.e., in the event dequeue call ARM core can enter WFE and exit
when either work has been scheduled or dequeue timeout has reached.
This feature can be selected by configuring meson with ``RTE_ARM_USE_WFE`` enabled.

Debugging Options
-----------------

.. _table_octeon_cnxk_event_debug_options:

.. table:: OCTEON cnxk event device debug options

   +---+------------+-------------------------------------------------------+
   | # | Component  | EAL log command                                       |
   +===+============+=======================================================+
   | 1 | SSO        | --log-level='pmd\.common\.cnxk\.event,8'              |
   +---+------------+-------------------------------------------------------+
   | 2 | TIM        | --log-level='pmd\.common\.cnxk\.timer,8'              |
   +---+------------+-------------------------------------------------------+

Limitations
-----------

Rx adapter support
~~~~~~~~~~~~~~~~~~

Using the same mempool for all the ethernet device ports connected to
event device would cause back pressure to be asserted only on the first
ethernet device.
Back pressure is automatically disabled when using same mempool for all the
ethernet devices connected to event device to override this applications can
use `force_rx_bp=1` device arguments.
Using unique mempool per each ethernet device is recommended when they are
connected to event device.

DMA adapter new mode support
~~~~~~~~~~~~~~~~~~~~~~~~~~~~

DMA driver does not support DMA adapter configured in new mode.
