[PATCH] net: lantiq: Add locking for TX DMA channel

[Hauke Mehrtens]

The TX DMA channel data is accessed by the xrx200_start_xmit() and the
xrx200_tx_housekeeping() function from different threads. Make sure the
accesses are synchronized by using locking around the accesses.

Signed-off-by: Hauke Mehrtens <ha...@hauke-m.de>
---
 drivers/net/ethernet/lantiq_xrx200.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/lantiq_xrx200.c 
b/drivers/net/ethernet/lantiq_xrx200.c
index 635ff3a5dcfb..f4de09d1f582 100644
--- a/drivers/net/ethernet/lantiq_xrx200.c
+++ b/drivers/net/ethernet/lantiq_xrx200.c
@@ -59,6 +59,7 @@ struct xrx200_chan {
        struct ltq_dma_channel dma;
        struct sk_buff *skb[LTQ_DESC_NUM];
 
+       spinlock_t lock;
        struct xrx200_priv *priv;
 };
 
@@ -242,9 +243,11 @@ static int xrx200_tx_housekeeping(struct napi_struct 
*napi, int budget)
        struct xrx200_chan *ch = container_of(napi,
                                struct xrx200_chan, napi);
        struct net_device *net_dev = ch->priv->net_dev;
+       unsigned long flags;
        int pkts = 0;
        int bytes = 0;
 
+       spin_lock_irqsave(&ch->lock, flags);
        while (pkts < budget) {
                struct ltq_dma_desc *desc = &ch->dma.desc_base[ch->tx_free];
 
@@ -268,6 +271,8 @@ static int xrx200_tx_housekeeping(struct napi_struct *napi, 
int budget)
        net_dev->stats.tx_bytes += bytes;
        netdev_completed_queue(ch->priv->net_dev, pkts, bytes);
 
+       spin_unlock_irqrestore(&ch->lock, flags);
+
        if (netif_queue_stopped(net_dev))
                netif_wake_queue(net_dev);
 
@@ -284,7 +289,8 @@ static netdev_tx_t xrx200_start_xmit(struct sk_buff *skb,
 {
        struct xrx200_priv *priv = netdev_priv(net_dev);
        struct xrx200_chan *ch = &priv->chan_tx;
-       struct ltq_dma_desc *desc = &ch->dma.desc_base[ch->dma.desc];
+       struct ltq_dma_desc *desc;
+       unsigned long flags;
        u32 byte_offset;
        dma_addr_t mapping;
        int len;
@@ -297,8 +303,11 @@ static netdev_tx_t xrx200_start_xmit(struct sk_buff *skb,
 
        len = skb->len;
 
+       spin_lock_irqsave(&ch->lock, flags);
+       desc = &ch->dma.desc_base[ch->dma.desc];
        if ((desc->ctl & (LTQ_DMA_OWN | LTQ_DMA_C)) || ch->skb[ch->dma.desc]) {
                netdev_err(net_dev, "tx ring full\n");
+               spin_unlock_irqrestore(&ch->lock, flags);
                netif_stop_queue(net_dev);
                return NETDEV_TX_BUSY;
        }
@@ -306,8 +315,10 @@ static netdev_tx_t xrx200_start_xmit(struct sk_buff *skb,
        ch->skb[ch->dma.desc] = skb;
 
        mapping = dma_map_single(priv->dev, skb->data, len, DMA_TO_DEVICE);
-       if (unlikely(dma_mapping_error(priv->dev, mapping)))
+       if (unlikely(dma_mapping_error(priv->dev, mapping))) {
+               spin_unlock_irqrestore(&ch->lock, flags);
                goto err_drop;
+       }
 
        /* dma needs to start on a 16 byte aligned address */
        byte_offset = mapping % 16;
@@ -324,6 +335,8 @@ static netdev_tx_t xrx200_start_xmit(struct sk_buff *skb,
 
        netdev_sent_queue(net_dev, len);
 
+       spin_unlock_irqrestore(&ch->lock, flags);
+
        return NETDEV_TX_OK;
 
 err_drop:
@@ -367,6 +380,7 @@ static int xrx200_dma_init(struct xrx200_priv *priv)
        ch_rx->dma.nr = XRX200_DMA_RX;
        ch_rx->dma.dev = priv->dev;
        ch_rx->priv = priv;
+       spin_lock_init(&ch_rx->lock);
 
        ltq_dma_alloc_rx(&ch_rx->dma);
        for (ch_rx->dma.desc = 0; ch_rx->dma.desc < LTQ_DESC_NUM;
@@ -387,6 +401,7 @@ static int xrx200_dma_init(struct xrx200_priv *priv)
        ch_tx->dma.nr = XRX200_DMA_TX;
        ch_tx->dma.dev = priv->dev;
        ch_tx->priv = priv;
+       spin_lock_init(&ch_tx->lock);
 
        ltq_dma_alloc_tx(&ch_tx->dma);
        ret = devm_request_irq(priv->dev, ch_tx->dma.irq, xrx200_dma_irq, 0,
-- 
2.20.1