From: Felix Fietkau <nbd@nbd.name>
Subject: mvneta: tx queue workaround

The hardware queue scheduling is apparently configured with fixed
priorities, which creates a nasty fairness issue where traffic from one
CPU can starve traffic from all other CPUs.

Work around this issue by forcing all tx packets to go through one CPU,
until this issue is fixed properly.

Ref: https://github.com/openwrt/openwrt/issues/5411

Signed-off-by: Felix Fietkau <nbd@nbd.name>
---
--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -5233,6 +5233,16 @@ static int mvneta_setup_tc(struct net_de
 	}
 }
 
+#ifndef CONFIG_ARM64
+static u16 mvneta_select_queue(struct net_device *dev, struct sk_buff *skb,
+			       struct net_device *sb_dev)
+{
+	/* XXX: hardware queue scheduling is broken,
+	 * use only one queue until it is fixed */
+	return 0;
+}
+#endif
+
 static const struct net_device_ops mvneta_netdev_ops = {
 	.ndo_open            = mvneta_open,
 	.ndo_stop            = mvneta_stop,
@@ -5243,6 +5253,9 @@ static const struct net_device_ops mvnet
 	.ndo_fix_features    = mvneta_fix_features,
 	.ndo_get_stats64     = mvneta_get_stats64,
 	.ndo_eth_ioctl        = mvneta_ioctl,
+#ifndef CONFIG_ARM64
+	.ndo_select_queue    = mvneta_select_queue,
+#endif
 	.ndo_bpf	     = mvneta_xdp,
 	.ndo_xdp_xmit        = mvneta_xdp_xmit,
 	.ndo_setup_tc	     = mvneta_setup_tc,