From 11a1b0633b31adb168fa49be548b732f38989fda Mon Sep 17 00:00:00 2001
From: Camelia Groza <camelia.groza@nxp.com>
Date: Fri, 24 Nov 2017 10:48:31 +0200
Subject: sdk_dpaa: ceetm: stop transmitting frames when the CQ is congested

When the egress CQ is congested, drop the frames instead of enqueueing
them. This is more efficient than enqueueing and receiving them back on
the ERN queue.

We also can't stop the netdev queues because that would affect all the CQs
and would hinder prioritization.

Signed-off-by: Camelia Groza <camelia.groza@nxp.com>

diff --git a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.c b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.c
index bf635b9..b7362bd 100644
--- a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.c
+++ b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.c
@@ -125,16 +125,16 @@ static void ceetm_cscn(struct qm_ceetm_ccg *ccg, void *cb_ctx, int congested)
 		break;
 	}
 
+	ceetm_fq->congested = congested;
+
 	if (congested) {
 		dpa_priv->cgr_data.congestion_start_jiffies = jiffies;
-		netif_tx_stop_all_queues(dpa_priv->net_dev);
 		dpa_priv->cgr_data.cgr_congested_count++;
 		if (cstats)
 			cstats->congested_count++;
 	} else {
 		dpa_priv->cgr_data.congested_jiffies +=
 			(jiffies - dpa_priv->cgr_data.congestion_start_jiffies);
-		netif_tx_wake_all_queues(dpa_priv->net_dev);
 	}
 }
 
@@ -148,6 +148,7 @@ static int ceetm_alloc_fq(struct ceetm_fq **fq, struct net_device *dev,
 
 	(*fq)->net_dev = dev;
 	(*fq)->ceetm_cls = cls;
+	(*fq)->congested = 0;
 	return 0;
 }
 
@@ -1913,7 +1914,8 @@ int __hot ceetm_tx(struct sk_buff *skb, struct net_device *net_dev)
 	struct Qdisc *sch = net_dev->qdisc;
 	struct ceetm_class *cl;
 	struct dpa_priv_s *priv_dpa;
-	struct qman_fq *egress_fq, *conf_fq;
+	struct ceetm_fq *ceetm_fq;
+	struct qman_fq *conf_fq;
 	struct ceetm_qdisc *priv = qdisc_priv(sch);
 	struct ceetm_qdisc_stats *qstats = this_cpu_ptr(priv->root.qstats);
 	struct ceetm_class_stats *cstats;
@@ -1945,11 +1947,11 @@ int __hot ceetm_tx(struct sk_buff *skb, struct net_device *net_dev)
 	 */
 	switch (cl->type) {
 	case CEETM_PRIO:
-		egress_fq = &cl->prio.fq->fq;
+		ceetm_fq = cl->prio.fq;
 		cstats = this_cpu_ptr(cl->prio.cstats);
 		break;
 	case CEETM_WBFS:
-		egress_fq = &cl->wbfs.fq->fq;
+		ceetm_fq = cl->wbfs.fq;
 		cstats = this_cpu_ptr(cl->wbfs.cstats);
 		break;
 	default:
@@ -1957,8 +1959,16 @@ int __hot ceetm_tx(struct sk_buff *skb, struct net_device *net_dev)
 		goto drop;
 	}
 
+	/* If the FQ is congested, avoid enqueuing the frame and dropping it
+	 * when it returns on the ERN path. Drop it here directly instead.
+	 */
+	if (unlikely(ceetm_fq->congested)) {
+		qstats->drops++;
+		goto drop;
+	}
+
 	bstats_update(&cstats->bstats, skb);
-	return dpa_tx_extended(skb, net_dev, egress_fq, conf_fq);
+	return dpa_tx_extended(skb, net_dev, &ceetm_fq->fq, conf_fq);
 
 drop:
 	dev_kfree_skb_any(skb);
diff --git a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.h b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.h
index 63cc3475..0ff3b9d 100644
--- a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.h
+++ b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_ceetm.h
@@ -105,6 +105,7 @@ struct ceetm_fq {
 	struct qman_fq fq;
 	struct net_device *net_dev;
 	struct ceetm_class *ceetm_cls;
+	int congested; /* Congestion status */
 };
 
 struct root_q {
-- 
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