From d7e3805608e878678dad5271edf2c28b9fe56fab Mon Sep 17 00:00:00 2001 From: Nicolas Chautru Date: Tue, 7 Sep 2021 18:15:40 -0700 Subject: [PATCH] doc: clarify usage of HARQ in bbdev New paragraph is added for detailing typical VRAN usecase and mapping to bbdev API usage. Signed-off-by: Nicolas Chautru Reviewed-by: Tom Rix --- doc/guides/prog_guide/bbdev.rst | 31 +++++++++++++++++++++++++++++++ 1 file changed, 31 insertions(+) diff --git a/doc/guides/prog_guide/bbdev.rst b/doc/guides/prog_guide/bbdev.rst index 8bd7cbae67..70fa01ada5 100644 --- a/doc/guides/prog_guide/bbdev.rst +++ b/doc/guides/prog_guide/bbdev.rst @@ -1054,6 +1054,37 @@ 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 no 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 be 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. -- 2.20.1