On Mon, Nov 15, 2004 at 04:32:43PM +0000, roger blofeld wrote:
> I'm trying to get a simple app running on a Lite5200 and am having a
> TCP/IP problem. Using tcpdump/ethereal I have learned that the Lite5200
> ethernet works fine until the client sends a TCP retransmission
> request. Then the Lite5200 replies with packets having incorrect
> checksums. Each successive Lite5200 packet appears to also lose two
> bytes of data (i.e., the packet size is correct, but the data is not
> the same for each retransmission because two bytes have been dropped
> from the start of the payload).
>
> Could this be a problem with the FEC driver? Bestcomm? How can I figure
> out what is broken here? Any help gladly accepted!
>
> I started with Sylvain Munaut's kernel at
> http://www.246tnt.com/mpc52xx/ and have also tried starting with the
> linux-2.5 tree and pulling Sylvain's tree into it to see if newer
> kernels worked better. I also tried using the recently updated bestcomm
> interface from denx.de with these kernels with the same result.
Try the following patch on top of Sylvain's tree. I sent it (and others)
to Sylvain a while back, but he must be busy with other things.
-Dale
--- linux-2.5-mpc52xx-devel/drivers/net/fec_mpc52xx/fec.c 2004-10-12
11:26:55.000000000 -0700
+++ linux-2.5-mpc52xx-devel-df/drivers/net/fec_mpc52xx/fec.c 2004-11-12
10:20:18.000000000 -0700
@@ -202,6 +202,41 @@
return -EAGAIN;
}
+/* The BestComm hardware requires data to be 32-bit aligned.
+ * We also pad to minimum ethernet packet length, ETH_ZLEN.
+ */
+static inline struct sk_buff *fec_skb_align_and_pad(struct sk_buff *skb)
+{
+ void *data = skb->data;
+ int len = skb->len;
+ int pad = (int)data & 0x3;
+ struct sk_buff *nskb;
+ int nlen;
+
+ if (pad == 0)
+ return skb;
+
+ if (!skb_cloned(skb)) {
+ skb_push(skb, pad);
+ memmove(skb->data, data, len);
+ skb_trim(skb, len);
+ skb = skb_padto(skb, ETH_ZLEN);
+ return skb;
+ }
+
+ /* ensure skb_padto doesn't have to reallocate */
+ nlen = (len >= ETH_ZLEN) ? len : ETH_ZLEN;
+
+ nskb = alloc_skb(nlen, GFP_ATOMIC);
+ if (nskb) {
+ skb_put(nskb, len);
+ memcpy(nskb->data, data, len);
+ nskb = skb_padto(nskb, ETH_ZLEN);
+ }
+ kfree_skb(skb);
+ return nskb;
+}
+
/* This will only be invoked if your driver is _not_ in XOFF state.
* What this means is that you need not check it, and that this
* invariant will hold if you make sure that the netif_*_queue()
@@ -210,30 +245,16 @@
static int fec_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
struct fec_priv *priv = (struct fec_priv *)dev->priv;
- int pad;
void *data;
- short length;
if (sdma_queue_full(priv->tx_sdma))
panic("MPC52xx transmit queue overrun\n");
- /* the BestComm hardware requires data to be 32-bit aligned */
- pad = (int)skb->data & 0x3;
- if (pad) {
- void *old_data = skb->data;
- length = skb->len;
-
- skb_push(skb, pad);
- memcpy(skb->data, old_data, length);
- skb_trim(skb, length);
- }
-
- /* Zero out up to the minimum length ethernet packet size,
- * so we don't inadvertently expose sensitive data
- */
- skb = skb_padto(skb, ETH_ZLEN);
- if (skb == 0)
+ skb = fec_skb_align_and_pad(skb);
+ if (!skb) {
+ priv->stats.tx_dropped++;
return 0;
+ }
spin_lock_irq(&priv->lock);
dev->trans_start = jiffies;
@@ -294,7 +315,8 @@
break;
rskb = sdma_retrieve_buffer(priv->rx_sdma, &length);
- skb_trim(rskb, length);
+ /* length included sizeof CRC32 */
+ skb_trim(rskb, length - sizeof(u32));
/* allocate replacement skb */
skb = dev_alloc_skb(FEC_RX_BUFFER_SIZE);
@@ -309,6 +331,7 @@
priv->stats.rx_dropped++;
skb_trim(rskb, 0);
+ skb = rskb;
}
skb->dev = dev;
