net: calxedaxgmac: ip align receive buffers

On gcc 4.7, we will get alignment traps in the ip stack if we don't align
the ip headers on receive. The h/w can support this, so use ip aligned
allocations.

Cut down the unnecessary padding on the allocation. The buffer can start on
any byte alignment, but the size including the begining offset must be 8
byte aligned. So the h/w buffer size must include the NET_IP_ALIGN offset.

Thanks to Eric Dumazet for the initial patch highlighting the padding issues.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
index 362b35ed850b1fd9f0365e3cc9e3ed00e0f4aa92..b407043ce9b0df3c1286fb3c0051f012cfa5e5b0 100644 (file)
--- a/drivers/net/ethernet/calxeda/xgmac.c
+++ b/drivers/net/ethernet/calxeda/xgmac.c
@@ -665,6 +665,7 @@ static void xgmac_rx_refill(struct xgmac_priv *priv)
 {
        struct xgmac_dma_desc *p;
        dma_addr_t paddr;
+       int bufsz = priv->dev->mtu + ETH_HLEN + ETH_FCS_LEN;
 
        while (dma_ring_space(priv->rx_head, priv->rx_tail, DMA_RX_RING_SZ) > 1) {
                int entry = priv->rx_head;
@@ -673,13 +674,13 @@ static void xgmac_rx_refill(struct xgmac_priv *priv)
                p = priv->dma_rx + entry;
 
                if (priv->rx_skbuff[entry] == NULL) {
-                       skb = netdev_alloc_skb(priv->dev, priv->dma_buf_sz);
+                       skb = netdev_alloc_skb_ip_align(priv->dev, bufsz);
                        if (unlikely(skb == NULL))
                                break;
 
                        priv->rx_skbuff[entry] = skb;
                        paddr = dma_map_single(priv->device, skb->data,
-                                              priv->dma_buf_sz, DMA_FROM_DEVICE);
+                                              bufsz, DMA_FROM_DEVICE);
                        desc_set_buf_addr(p, paddr, priv->dma_buf_sz);
                }
 
@@ -703,10 +704,10 @@ static int xgmac_dma_desc_rings_init(struct net_device *dev)
        unsigned int bfsize;
 
        /* Set the Buffer size according to the MTU;
-        * indeed, in case of jumbo we need to bump-up the buffer sizes.
+        * The total buffer size including any IP offset must be a multiple
+        * of 8 bytes.
         */
-       bfsize = ALIGN(dev->mtu + ETH_HLEN + ETH_FCS_LEN + NET_IP_ALIGN + 64,
-                      64);
+       bfsize = ALIGN(dev->mtu + ETH_HLEN + ETH_FCS_LEN + NET_IP_ALIGN, 8);
 
        netdev_dbg(priv->dev, "mtu [%d] bfsize [%d]\n", dev->mtu, bfsize);