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.chau...@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 <t...@redhat.com>
