netdev - [PATCH v2 net-next 6/7] dpaa2-eth: Add congestion group taildrop

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Date:   Fri, 15 May 2020 21:47:52 +0300
From:   Ioana Ciornei <ioana.ciornei@....com>
To:     davem@...emloft.net, netdev@...r.kernel.org
Cc:     Ioana Radulescu <ruxandra.radulescu@....com>,
        Ioana Ciornei <ioana.ciornei@....com>
Subject: [PATCH v2 net-next 6/7] dpaa2-eth: Add congestion group taildrop

From: Ioana Radulescu <ruxandra.radulescu@....com>

The increase in number of ingress frame queues means we now risk
depleting the buffer pool before the FQ taildrop kicks in.

Congestion group taildrop allows us to control the number of frames
that can accumulate on a group of Rx frame queues belonging to the
same traffic class.

This setting coexists with the frame queue based taildrop: whichever
limit gets hit first triggers the frame drop.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@....com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@....com>
---
Changes in v2:
 - none

 drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c | 16 ++++++++++++++++
 drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h |  9 +++++++++
 2 files changed, 25 insertions(+)

diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index d8b1d6ab6656..318b4332df87 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -1309,6 +1309,22 @@ static void dpaa2_eth_set_rx_taildrop(struct dpaa2_eth_priv *priv,
 		}
 	}
 
+	/* Congestion group taildrop: threshold is in frames, per group
+	 * of FQs belonging to the same traffic class
+	 */
+	td.threshold = DPAA2_ETH_CG_TAILDROP_THRESH(priv);
+	td.units = DPNI_CONGESTION_UNIT_FRAMES;
+	for (i = 0; i < dpaa2_eth_tc_count(priv); i++) {
+		err = dpni_set_taildrop(priv->mc_io, 0, priv->mc_token,
+					DPNI_CP_GROUP, DPNI_QUEUE_RX,
+					i, 0, &td);
+		if (err) {
+			netdev_err(priv->net_dev,
+				   "dpni_set_taildrop(CG) failed\n");
+			return;
+		}
+	}
+
 	priv->rx_td_enabled = td.enable;
 }
 
diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h
index 1b9f6689e9ec..184d5d83e497 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h
@@ -57,6 +57,15 @@
 #define DPAA2_ETH_REFILL_THRESH \
 	(DPAA2_ETH_NUM_BUFS - DPAA2_ETH_BUFS_PER_CMD)
 
+/* Congestion group taildrop threshold: number of frames allowed to accumulate
+ * at any moment in a group of Rx queues belonging to the same traffic class.
+ * Choose value such that we don't risk depleting the buffer pool before the
+ * taildrop kicks in
+ */
+#define DPAA2_ETH_CG_TAILDROP_THRESH(priv)				\
+	(DPAA2_ETH_MAX_FRAMES_PER_QUEUE * dpaa2_eth_queue_count(priv) /	\
+	 dpaa2_eth_tc_count(priv))
+
 /* Maximum number of buffers that can be acquired/released through a single
  * QBMan command
  */
-- 
2.17.1