[dpdk-dev] [PATCH 4/4] doc: update the description for Rx delay drop

[Bing Zhao <bingz@nvidia.com>]

The release note and new device parameter "delay_drop_en" for the
delay drop feature in mlx5.rst are updated.

Signed-off-by: Bing Zhao <bingz@nvidia.com>
---
 doc/guides/nics/mlx5.rst               | 26 ++++++++++++++++++++++++++
 doc/guides/rel_notes/release_21_11.rst |  1 +
 2 files changed, 27 insertions(+)

diff --git a/doc/guides/nics/mlx5.rst b/doc/guides/nics/mlx5.rst
index bb92520dff..2874a34cb6 100644
--- a/doc/guides/nics/mlx5.rst
+++ b/doc/guides/nics/mlx5.rst
@@ -1123,6 +1123,27 @@ Driver options
 
   By default, the PMD will set this value to 1.
 
+- ``delay_drop_en`` parameter [int]
+
+  Bitmask value for the Rx queue delay drop attribute. Bit 0 is used for standard
+  Rx queue and bit 1 is used for hairpin Rx queue.
+  By default, the delay drop will be enabled for all hairpin Rx queues (if any)
+  and disabled for all standard Rx queues. It will be ignored if the NIC does
+  not support the attribute.
+  A timeout value is set in the driver to control the waiting time before dropping
+  a packet when there is no WQE available on a delay drop Rx queue. Once the timer
+  is expired, the delay drop will be deactivated for all queues. To re-activeate it,
+  a rearming is needed and now it is part of the kernel driver.
+
+  To enable / disable the delay drop rearming, the private flag ``dropless_rq`` can
+  be set and queried via ethtool:
+
+  - ethtool --set-priv-flags <netdev> dropless_rq on (/ off)
+  - ethtool --show-priv-flags <netdev>
+
+  The configuration flag is global per PF and can only be set on the PF, once it is on,
+  all the VFs', SFs' and representors' Rx queues will share the timer and rearming.
+
 .. _mlx5_firmware_config:
 
 Firmware configuration
@@ -1797,6 +1818,11 @@ Supported hardware offloads
    |                       | |               | | rdma-core 35  |
    |                       | |               | | ConnectX-6 Dx |
    +-----------------------+-----------------+-----------------+
+   | Rxq Delay drop        | | DPDK 21.11    | | DPDK 21.11    |
+   |                       | | OFED 5.5      | | OFED 5.5      |
+   |                       | | N/A           | | N/A           |
+   |                       | | ConnectX-5    | | ConnectX-5    |
+   +-----------------------+-----------------+-----------------+
 
 .. table:: Minimal SW/HW versions for shared action offload
    :name: sact
diff --git a/doc/guides/rel_notes/release_21_11.rst b/doc/guides/rel_notes/release_21_11.rst
index 13d8330873..76d18aeb6b 100644
--- a/doc/guides/rel_notes/release_21_11.rst
+++ b/doc/guides/rel_notes/release_21_11.rst
@@ -191,6 +191,7 @@ New Features
   * Added implicit mempool registration to avoid data path hiccups (opt-out).
   * Added NIC offloads for the PMD on Windows (TSO, VLAN strip, CRC keep).
   * Added socket direct mode bonding support.
+  * Added delay drop support for Rx queue.
 
 * **Updated Solarflare network PMD.**
 
-- 
2.27.0