[dpdk-dev] [PATCH v3 5/6] doc: clarification of usage of HARQ in bbdev doc

[Tom Rix]

On 9/7/21 6:15 PM, Nicolas Chautru wrote:
> New paragraph detailing typical VRAN usecase and mapping
> to bbdev API usage.
>
> Signed-off-by: Nicolas Chautru <nicolas.chautru at intel.com>
> ---
>   doc/guides/prog_guide/bbdev.rst | 23 +++++++++++++++++++++++
>   1 file changed, 23 insertions(+)
>
> diff --git a/doc/guides/prog_guide/bbdev.rst b/doc/guides/prog_guide/bbdev.rst
> index 8bd7cba..f39b62f 100644
> --- a/doc/guides/prog_guide/bbdev.rst
> +++ b/doc/guides/prog_guide/bbdev.rst
> @@ -1054,6 +1054,29 @@ capability RTE_BBDEV_LDPC_INTERNAL_HARQ_MEMORY_OUT_ENABLE is set
>   then the HARQ is stored in memory internal to the device and not visible
>   to BBDEV.
>   
> +.. note::
> +    More explicitly for a typical usage of HARQ retransmission in a VRAN
> +    application using a HW PMD, there will be 2 cases.
> +
> +    For 1st transmission, only the HARQ output is enabled :
> +
> +    - the harq_combined_output.offset is provided to a given address. ie. typically an integer index * 32K, where the index is tracked by the application based on code block index for a given UE and HARQ process.
> +
> +    - the related operation flag would notably include RTE_BBDEV_LDPC_HQ_COMBINE_OUT_ENABLE and RTE_BBDEV_LDPC_HARQ_6BIT_COMPRESSION.
> +
> +    - note that not explicit flush or reset of the memory is required.
> +
> +    For 2nd transmission, an input is also required to benefit from HARQ combination gain:
> +
> +    - the changes mentioned above are the same (note that rvIndex may be adjusted).
> +
> +    - the operation flag would additionally include the LDPC_HQ_COMBINE_IN_ENABLE flag.
> +
> +    - the harq_combined_input.offset must set to the address of the related code block (ie. same as the harq_combine_output index above for the same code block, HARQ process, UE).
> +
> +    - the harq_combined_input.length must be set to the length which was provided back in the related harq_combined_output.length when it has processed and dequeued (previous HARQ iteration).
> +
> +
>   The output mbuf data structures are expected to be allocated by the
>   application with enough room for the output data.
>   

Fine.

Reviewed-by: Tom Rix <trix at redhat.com>