net: renesas: rswitch: Add spin lock protection for irq {un}mask

Add spin lock protection for irq {un}mask registers' control.

After napi_complete_done() and this protection were applied,
a lot of redundant interrupts no longer occur.

For example: when "iperf3 -c <ipaddr> -R" on R-Car S4-8 Spider
 Before the patches are applied: about 800,000 times happened
 After the patches were applied: about 100,000 times happened

Fixes: 3590918b ("net: ethernet: renesas: Add support for "Ethernet Switch"")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/ethernet/renesas/rswitch.c

@@ -799,6 +799,7 @@ static int rswitch_poll(struct napi_struct *napi, int budget)
 	struct net_device *ndev = napi->dev;
 	struct rswitch_private *priv;
 	struct rswitch_device *rdev;
+	unsigned long flags;
 	int quota = budget;
 
 	rdev = netdev_priv(ndev);
@@ -817,8 +818,10 @@ static int rswitch_poll(struct napi_struct *napi, int budget)
 	netif_wake_subqueue(ndev, 0);
 
 	if (napi_complete_done(napi, budget - quota)) {
+		spin_lock_irqsave(&priv->lock, flags);
 		rswitch_enadis_data_irq(priv, rdev->tx_queue->index, true);
 		rswitch_enadis_data_irq(priv, rdev->rx_queue->index, true);
+		spin_unlock_irqrestore(&priv->lock, flags);
 	}
 
 out:
@@ -835,8 +838,10 @@ static void rswitch_queue_interrupt(struct net_device *ndev)
 	struct rswitch_device *rdev = netdev_priv(ndev);
 
 	if (napi_schedule_prep(&rdev->napi)) {
+		spin_lock(&rdev->priv->lock);
 		rswitch_enadis_data_irq(rdev->priv, rdev->tx_queue->index, false);
 		rswitch_enadis_data_irq(rdev->priv, rdev->rx_queue->index, false);
+		spin_unlock(&rdev->priv->lock);
 		__napi_schedule(&rdev->napi);
 	}
 }
@@ -1440,14 +1445,17 @@ static void rswitch_ether_port_deinit_all(struct rswitch_private *priv)
 static int rswitch_open(struct net_device *ndev)
 {
 	struct rswitch_device *rdev = netdev_priv(ndev);
+	unsigned long flags;
 
 	phy_start(ndev->phydev);
 
 	napi_enable(&rdev->napi);
 	netif_start_queue(ndev);
 
+	spin_lock_irqsave(&rdev->priv->lock, flags);
 	rswitch_enadis_data_irq(rdev->priv, rdev->tx_queue->index, true);
 	rswitch_enadis_data_irq(rdev->priv, rdev->rx_queue->index, true);
+	spin_unlock_irqrestore(&rdev->priv->lock, flags);
 
 	if (bitmap_empty(rdev->priv->opened_ports, RSWITCH_NUM_PORTS))
 		iowrite32(GWCA_TS_IRQ_BIT, rdev->priv->addr + GWTSDIE);
@@ -1461,6 +1469,7 @@ static int rswitch_stop(struct net_device *ndev)
 {
 	struct rswitch_device *rdev = netdev_priv(ndev);
 	struct rswitch_gwca_ts_info *ts_info, *ts_info2;
+	unsigned long flags;
 
 	netif_tx_stop_all_queues(ndev);
 	bitmap_clear(rdev->priv->opened_ports, rdev->port, 1);
@@ -1476,8 +1485,10 @@ static int rswitch_stop(struct net_device *ndev)
 		kfree(ts_info);
 	}
 
+	spin_lock_irqsave(&rdev->priv->lock, flags);
 	rswitch_enadis_data_irq(rdev->priv, rdev->tx_queue->index, false);
 	rswitch_enadis_data_irq(rdev->priv, rdev->rx_queue->index, false);
+	spin_unlock_irqrestore(&rdev->priv->lock, flags);
 
 	phy_stop(ndev->phydev);
 	napi_disable(&rdev->napi);
@@ -1887,6 +1898,7 @@ static int renesas_eth_sw_probe(struct platform_device *pdev)
 	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
 	if (!priv)
 		return -ENOMEM;
+	spin_lock_init(&priv->lock);
 
 	attr = soc_device_match(rswitch_soc_no_speed_change);
 	if (attr)

drivers/net/ethernet/renesas/rswitch.h

@@ -1011,6 +1011,8 @@ struct rswitch_private {
 	struct rswitch_etha etha[RSWITCH_NUM_PORTS];
 	struct rswitch_mfwd mfwd;
 
+	spinlock_t lock;	/* lock interrupt registers' control */
+
 	bool etha_no_runtime_change;
 	bool gwca_halt;
 };