stmmac: do not perform zero-copy for rx frames

This patch is to allow this driver to copy tiny frames during the reception
process. This is giving more stability while stressing the driver on STi
embedded systems.

Signed-off-by: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Signed-off-by: Alexandre TORGUE <alexandre.torgue@st.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 46 insertions, 15 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 3cc135559a1d..2ffe8dd9ce99 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -91,6 +91,8 @@ static int buf_sz = DEFAULT_BUFSIZE;
 module_param(buf_sz, int, S_IRUGO | S_IWUSR);
 MODULE_PARM_DESC(buf_sz, "DMA buffer size");
 
+#define	STMMAC_RX_COPYBREAK	256
+
 static const u32 default_msg_level = (NETIF_MSG_DRV | NETIF_MSG_PROBE |
 				      NETIF_MSG_LINK | NETIF_MSG_IFUP |
 				      NETIF_MSG_IFDOWN | NETIF_MSG_TIMER);
@@ -1808,6 +1810,7 @@ static int stmmac_open(struct net_device *dev)
 	priv->xstats.threshold = tc;
 
 	priv->dma_buf_sz = STMMAC_ALIGN(buf_sz);
+	priv->rx_copybreak = STMMAC_RX_COPYBREAK;
 
 	ret = alloc_dma_desc_resources(priv);
 	if (ret < 0) {
@@ -2159,8 +2162,7 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv)
 			struct sk_buff *skb;
 
 			skb = netdev_alloc_skb_ip_align(priv->dev, bfsize);
-
-			if (unlikely(skb == NULL))
+			if (unlikely(!skb))
 				break;
 
 			priv->rx_skbuff[entry] = skb;
@@ -2282,23 +2284,52 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit)
 					pr_debug("\tframe size %d, COE: %d\n",
 						 frame_len, status);
 			}
-			skb = priv->rx_skbuff[entry];
-			if (unlikely(!skb)) {
-				pr_err("%s: Inconsistent Rx descriptor chain\n",
-				       priv->dev->name);
-				priv->dev->stats.rx_dropped++;
-				break;
+
+			if (unlikely(frame_len < priv->rx_copybreak)) {
+				skb = netdev_alloc_skb_ip_align(priv->dev,
+								frame_len);
+				if (unlikely(!skb)) {
+					if (net_ratelimit())
+						dev_warn(priv->device,
+							 "packet dropped\n");
+					priv->dev->stats.rx_dropped++;
+					break;
+				}
+
+				dma_sync_single_for_cpu(priv->device,
+							priv->rx_skbuff_dma
+							[entry], frame_len,
+							DMA_FROM_DEVICE);
+				skb_copy_to_linear_data(skb,
+							priv->
+							rx_skbuff[entry]->data,
+							frame_len);
+
+				skb_put(skb, frame_len);
+				dma_sync_single_for_device(priv->device,
+							   priv->rx_skbuff_dma
+							   [entry], frame_len,
+							   DMA_FROM_DEVICE);
+			} else {
+				skb = priv->rx_skbuff[entry];
+				if (unlikely(!skb)) {
+					pr_err("%s: Inconsistent Rx chain\n",
+					       priv->dev->name);
+					priv->dev->stats.rx_dropped++;
+					break;
+				}
+				prefetch(skb->data - NET_IP_ALIGN);
+				priv->rx_skbuff[entry] = NULL;
+
+				skb_put(skb, frame_len);
+				dma_unmap_single(priv->device,
+						 priv->rx_skbuff_dma[entry],
+						 priv->dma_buf_sz,
+						 DMA_FROM_DEVICE);
 			}
-			prefetch(skb->data - NET_IP_ALIGN);
-			priv->rx_skbuff[entry] = NULL;
 
 			stmmac_get_rx_hwtstamp(priv, entry, skb);
 
-			skb_put(skb, frame_len);
-			dma_unmap_single(priv->device,
-					 priv->rx_skbuff_dma[entry],
-					 priv->dma_buf_sz, DMA_FROM_DEVICE);
-
 			if (netif_msg_pktdata(priv)) {
 				pr_debug("frame received (%dbytes)", frame_len);
 				print_pkt(skb->data, frame_len);