2. 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.

2.1. Supported OCTEON cnxk SoCs

CN9XX
CN10XX

2.2. 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.
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 for packets enqueued from ethdev to eventdev configurable per each Rx queue in Rx adapter.
Event vector transmission via Tx adapter.

2.3. Prerequisites and Compilation procedure

See Marvell cnxk platform guide for setup information.

2.4. 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
```
CN10K Getwork mode

CN10K supports multiple getwork prefetch modes, by default the prefetch mode is set to none.

For example:
```
-a 0002:0e:00.0,gw_mode=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-XAQ-TAQ-IAQ][Qz-XAQ-TAQ-IAQ] expressed in percentages, 0 represents default.

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

2.5. Debugging Options

Table 2.3 OCTEON cnxk event device debug options
#	Component	EAL log command
1	SSO	–log-level=’pmd.event.cnxk,8’
2	TIM	–log-level=’pmd.event.cnxk.timer,8’

2.6. Limitations

2.6.1. 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.