dpaa2-eth: Add congestion group taildrop

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@nxp.com>
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
index c16c8ea..04eff63 100644
--- a/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
+++ b/drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c
@@ -1287,17 +1287,20 @@ static void disable_ch_napi(struct dpaa2_eth_priv *priv)
 	}
 }
 
-static void dpaa2_eth_set_rx_taildrop(struct dpaa2_eth_priv *priv, bool enable)
+static void dpaa2_eth_set_rx_taildrop(struct dpaa2_eth_priv *priv,
+				      bool tx_pause)
 {
 	struct dpni_taildrop td = {0};
 	struct dpaa2_eth_fq *fq;
 	int i, err;
 
-	if (priv->rx_td_enabled == enable)
+	td.enable = !tx_pause;
+	if (priv->rx_td_enabled == td.enable)
 		return;
 
-	td.enable = enable;
-	td.threshold = DPAA2_ETH_TAILDROP_THRESH;
+	/* FQ taildrop: threshold is in bytes, per frame queue */
+	td.threshold = DPAA2_ETH_FQ_TAILDROP_THRESH;
+	td.units = DPNI_CONGESTION_UNIT_BYTES;
 
 	for (i = 0; i < priv->num_fqs; i++) {
 		fq = &priv->fq[i];
@@ -1308,12 +1311,28 @@ static void dpaa2_eth_set_rx_taildrop(struct dpaa2_eth_priv *priv, bool enable)
 					fq->tc, fq->flowid, &td);
 		if (err) {
 			netdev_err(priv->net_dev,
-				   "dpni_set_taildrop() failed\n");
-			break;
+				   "dpni_set_taildrop(FQ) failed\n");
+			return;
 		}
 	}
 
-	priv->rx_td_enabled = enable;
+	/* 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;
 }
 
 static int link_state_update(struct dpaa2_eth_priv *priv)
@@ -1334,7 +1353,7 @@ static int link_state_update(struct dpaa2_eth_priv *priv)
 	 * only when pause frame generation is disabled.
 	 */
 	tx_pause = dpaa2_eth_tx_pause_enabled(state.options);
-	dpaa2_eth_set_rx_taildrop(priv, !tx_pause);
+	dpaa2_eth_set_rx_taildrop(priv, tx_pause);
 
 	/* When we manage the MAC/PHY using phylink there is no need
 	 * to manually update the netif_carrier.