net: calxedaxgmac: fix xgmac_xmit DMA mapping error handling

On a DMA mapping error in xgmac_xmit, we should simply free the skb and
return NETDEV_TX_OK rather than -EIO. In the case of errors in mapping
frags, we need to undo everything that has been setup.

Reported-by: Andreas Herrmann <andreas.herrmann@calxeda.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 26 insertions, 5 deletions

diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
index cd5010b4a89c..78d6d6b970e1 100644
--- a/drivers/net/ethernet/calxeda/xgmac.c
+++ b/drivers/net/ethernet/calxeda/xgmac.c
@@ -466,6 +466,13 @@ static inline void desc_set_tx_owner(struct xgmac_dma_desc *p, u32 flags)
         p->flags = cpu_to_le32(tmpflags);
 }
 
+static inline void desc_clear_tx_owner(struct xgmac_dma_desc *p)
+{
+        u32 tmpflags = le32_to_cpu(p->flags);
+        tmpflags &= TXDESC_END_RING;
+        p->flags = cpu_to_le32(tmpflags);
+}
+
 static inline int desc_get_tx_ls(struct xgmac_dma_desc *p)
 {
         return le32_to_cpu(p->flags) & TXDESC_LAST_SEG;
@@ -1100,7 +1107,7 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb, struct net_device *dev)
         paddr = dma_map_single(priv->device, skb->data, len, DMA_TO_DEVICE);
         if (dma_mapping_error(priv->device, paddr)) {
                 dev_kfree_skb(skb);
-                return -EIO;
+                return NETDEV_TX_OK;
         }
         priv->tx_skbuff[entry] = skb;
         desc_set_buf_addr_and_size(desc, paddr, len);
@@ -1112,10 +1119,8 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb, struct net_device *dev)
 
                 paddr = skb_frag_dma_map(priv->device, frag, 0, len,
                                          DMA_TO_DEVICE);
-                if (dma_mapping_error(priv->device, paddr)) {
-                        dev_kfree_skb(skb);
-                        return -EIO;
-                }
+                if (dma_mapping_error(priv->device, paddr))
+                        goto dma_err;
 
                 entry = dma_ring_incr(entry, DMA_TX_RING_SZ);
                 desc = priv->dma_tx + entry;
@@ -1151,6 +1156,22 @@ static netdev_tx_t xgmac_xmit(struct sk_buff *skb, struct net_device *dev)
                         netif_start_queue(dev);
         }
         return NETDEV_TX_OK;
+
+dma_err:
+        entry = priv->tx_head;
+        for ( ; i > 0; i--) {
+                entry = dma_ring_incr(entry, DMA_TX_RING_SZ);
+                desc = priv->dma_tx + entry;
+                priv->tx_skbuff[entry] = NULL;
+                dma_unmap_page(priv->device, desc_get_buf_addr(desc),
+                               desc_get_buf_len(desc), DMA_TO_DEVICE);
+                desc_clear_tx_owner(desc);
+        }
+        desc = first;
+        dma_unmap_single(priv->device, desc_get_buf_addr(desc),
+                         desc_get_buf_len(desc), DMA_TO_DEVICE);
+        dev_kfree_skb(skb);
+        return NETDEV_TX_OK;
 }
 
 static int xgmac_rx(struct xgmac_priv *priv, int limit)