diff mbox

[v3,6/6] net: calxedaxgmac: ip align receive buffers

Message ID 1352132544-15809-7-git-send-email-robherring2@gmail.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Rob Herring Nov. 5, 2012, 4:22 p.m. UTC 
From: Rob Herring <rob.herring@calxeda.com>

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>
---
 drivers/net/ethernet/calxeda/xgmac.c |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

Comments

Eric Dumazet Nov. 5, 2012, 4:53 p.m. UTC | #1 
On Mon, 2012-11-05 at 10:22 -0600, Rob Herring wrote:
> From: Rob Herring <rob.herring@calxeda.com>
> 
> 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>


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diff mbox

Patch

diff --git a/drivers/net/ethernet/calxeda/xgmac.c b/drivers/net/ethernet/calxeda/xgmac.c
index 362b35e..b407043 100644
--- 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);