[dpdk-dev] [PATCH] net/mlx5: add debug print of LRO minimal size

[Dekel Peled <dekelp@nvidia.com>]

Add debug printout showing HCA capability lro_min_mss_size - the
minimal size of TCP segment required for coalescing.
MLX5 PMD documentation is updated to note this condition.

Signed-off-by: Dekel Peled <dekelp@nvidia.com>
---
 doc/guides/nics/mlx5.rst             | 4 +++-
 drivers/common/mlx5/mlx5_devx_cmds.c | 2 ++
 drivers/common/mlx5/mlx5_devx_cmds.h | 1 +
 drivers/net/mlx5/linux/mlx5_os.c     | 3 +++
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index b0614ae..f4632dc 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -302,8 +302,10 @@ Limitations
     it with size limited to max LRO size, not to max RX packet length.
   - LRO can be used with outer header of TCP packets of the standard format:
         eth (with or without vlan) / ipv4 or ipv6 / tcp / payload
-
     Other TCP packets (e.g. with MPLS label) received on Rx queue with LRO enabled, will be received with bad checksum.
+  - LRO packet aggregation is performed by HW only for packet size larger than
+    ``lro_min_mss_size``. This value is reported on device start, when debug
+    mode is enabled.
 
 - CRC:
 
diff --git a/drivers/common/mlx5/mlx5_devx_cmds.c b/drivers/common/mlx5/mlx5_devx_cmds.c
index 7c81ae1..224f72c 100644
--- a/drivers/common/mlx5/mlx5_devx_cmds.c
+++ b/drivers/common/mlx5/mlx5_devx_cmds.c
@@ -792,6 +792,8 @@ struct mlx5_devx_obj *
 			MLX5_GET(per_protocol_networking_offload_caps, hcattr,
 				 lro_timer_supported_periods[i]);
 	}
+	attr->lro_min_mss_size = MLX5_GET(per_protocol_networking_offload_caps,
+					  hcattr, lro_min_mss_size);
 	attr->tunnel_stateless_geneve_rx =
 			    MLX5_GET(per_protocol_networking_offload_caps,
 				     hcattr, tunnel_stateless_geneve_rx);
diff --git a/drivers/common/mlx5/mlx5_devx_cmds.h b/drivers/common/mlx5/mlx5_devx_cmds.h
index 1c84cea..1834132 100644
--- a/drivers/common/mlx5/mlx5_devx_cmds.h
+++ b/drivers/common/mlx5/mlx5_devx_cmds.h
@@ -85,6 +85,7 @@ struct mlx5_hca_attr {
 	uint32_t tunnel_lro_vxlan:1;
 	uint32_t lro_max_msg_sz_mode:2;
 	uint32_t lro_timer_supported_periods[MLX5_LRO_NUM_SUPP_PERIODS];
+	uint16_t lro_min_mss_size;
 	uint32_t flex_parser_protocols;
 	uint32_t hairpin:1;
 	uint32_t log_max_hairpin_queues:5;
diff --git a/drivers/net/mlx5/linux/mlx5_os.c b/drivers/net/mlx5/linux/mlx5_os.c
index 487714f..5bf460a 100644
--- a/drivers/net/mlx5/linux/mlx5_os.c
+++ b/drivers/net/mlx5/linux/mlx5_os.c
@@ -1071,6 +1071,9 @@
 				config->hca_attr.lro_timer_supported_periods[0];
 			DRV_LOG(DEBUG, "LRO session timeout set to %d usec",
 				config->lro.timeout);
+			DRV_LOG(DEBUG, "LRO minimal size of TCP segment "
+				"required for coalescing is %d bytes",
+				config->hca_attr.lro_min_mss_size);
 		}
 #if defined(HAVE_MLX5DV_DR) && defined(HAVE_MLX5_DR_CREATE_ACTION_FLOW_METER)
 		if (config->hca_attr.qos.sup &&
-- 
1.8.3.1