[PATCH] net: ftgmac100: Ensure tx descriptor updates are visible

[Jacky Chou]

The driver must ensure TX descriptor updates are visible
before updating TX pointer and TX clear pointer.

This resolves TX hangs observed on AST2600 when running
iperf3.

Signed-off-by: Jacky Chou <jacky_chou@xxxxxxxxxxxxxx>
---
 drivers/net/ethernet/faraday/ftgmac100.c | 26 ++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/drivers/net/ethernet/faraday/ftgmac100.c b/drivers/net/ethernet/faraday/ftgmac100.c
index 93862b027be0..9c521d0af7ac 100644
--- a/drivers/net/ethernet/faraday/ftgmac100.c
+++ b/drivers/net/ethernet/faraday/ftgmac100.c
@@ -582,7 +582,7 @@ static bool ftgmac100_rx_packet(struct ftgmac100 *priv, int *processed)
 	(*processed)++;
 	return true;
 
- drop:
+drop:
 	/* Clean rxdes0 (which resets own bit) */
 	rxdes->rxdes0 = cpu_to_le32(status & priv->rxdes0_edorr_mask);
 	priv->rx_pointer = ftgmac100_next_rx_pointer(priv, pointer);
@@ -666,6 +666,11 @@ static bool ftgmac100_tx_complete_packet(struct ftgmac100 *priv)
 	ftgmac100_free_tx_packet(priv, pointer, skb, txdes, ctl_stat);
 	txdes->txdes0 = cpu_to_le32(ctl_stat & priv->txdes0_edotr_mask);
 
+	/* Ensure the descriptor config is visible before setting the tx
+	 * pointer.
+	 */
+	smp_wmb();
+
 	priv->tx_clean_pointer = ftgmac100_next_tx_pointer(priv, pointer);
 
 	return true;
@@ -819,6 +824,11 @@ static netdev_tx_t ftgmac100_hard_start_xmit(struct sk_buff *skb,
 	dma_wmb();
 	first->txdes0 = cpu_to_le32(f_ctl_stat);
 
+	/* Ensure the descriptor config is visible before setting the tx
+	 * pointer.
+	 */
+	smp_wmb();
+
 	/* Update next TX pointer */
 	priv->tx_pointer = pointer;
 
@@ -839,7 +849,7 @@ static netdev_tx_t ftgmac100_hard_start_xmit(struct sk_buff *skb,
 
 	return NETDEV_TX_OK;
 
- dma_err:
+dma_err:
 	if (net_ratelimit())
 		netdev_err(netdev, "map tx fragment failed\n");
 
@@ -861,7 +871,7 @@ static netdev_tx_t ftgmac100_hard_start_xmit(struct sk_buff *skb,
 	 * last fragment, so we know ftgmac100_free_tx_packet()
 	 * hasn't freed the skb yet.
 	 */
- drop:
+drop:
 	/* Drop the packet */
 	dev_kfree_skb_any(skb);
 	netdev->stats.tx_dropped++;
@@ -1354,7 +1364,7 @@ static void ftgmac100_reset(struct ftgmac100 *priv)
 	ftgmac100_init_all(priv, true);
 
 	netdev_dbg(netdev, "Reset done !\n");
- bail:
+bail:
 	if (priv->mii_bus)
 		mutex_unlock(&priv->mii_bus->mdio_lock);
 	if (netdev->phydev)
@@ -1554,15 +1564,15 @@ static int ftgmac100_open(struct net_device *netdev)
 
 	return 0;
 
- err_ncsi:
+err_ncsi:
 	napi_disable(&priv->napi);
 	netif_stop_queue(netdev);
- err_alloc:
+err_alloc:
 	ftgmac100_free_buffers(priv);
 	free_irq(netdev->irq, netdev);
- err_irq:
+err_irq:
 	netif_napi_del(&priv->napi);
- err_hw:
+err_hw:
 	iowrite32(0, priv->base + FTGMAC100_OFFSET_IER);
 	ftgmac100_free_rings(priv);
 	return err;
-- 
2.25.1