On Wed, May 6, 2009 at 2:15 PM, Wolfgang Denk <w...@denx.de> wrote:
> From: John Rigby <jri...@freescale.com>
>
> The FEC on 5121 has problems with misaligned tx buffers.
> The RM says any alignment is ok but empirical results
> show that packet buffers ending in 0x1E will sometimes
> hang the FEC. Other bad alignment does not hang but will
> cause silent TX failures resulting in about a 1% packet
> loss as tested by ping -f from a remote host.
>
> This patch is a work around that copies every tx packet
> to an aligned skb before sending.
OUCH!
> diff --git a/drivers/net/fs_enet/fs_enet-main.c
> b/drivers/net/fs_enet/fs_enet-main.c
> index 4170d33..c83ffc3 100644
> --- a/drivers/net/fs_enet/fs_enet-main.c
> +++ b/drivers/net/fs_enet/fs_enet-main.c
> @@ -594,6 +594,37 @@ void fs_cleanup_bds(struct net_device *dev)
>
> /**********************************************************************************/
>
> +#ifdef CONFIG_FS_ENET_FEC_TX_ALIGN_WORKAROUND
> +static struct sk_buff *tx_skb_align_workaround(struct net_device *dev,
> + struct sk_buff *skb)
> +{
> + struct sk_buff *new_skb;
> +
> + /* Alloc new skb */
> + new_skb = dev_alloc_skb(ENET_RX_FRSIZE + 32);
> + if (!new_skb) {
> + printk(KERN_WARNING DRV_MODULE_NAME
> + ": %s Memory squeeze, dropping tx packet.\n",
> + dev->name);
> + return NULL;
> + }
> +
> + /* Make sure new skb is properly aligned */
> + skb_align(new_skb, 32);
> +
> + /* Copy data to new skb ... */
> + skb_copy_from_linear_data(skb, new_skb->data, skb->len);
> + skb_put(new_skb, skb->len);
> +
> + /* ... and free an old one */
> + dev_kfree_skb_any(skb);
> +
> + return new_skb;
> +}
> +#else
> +#define tx_skb_align_workaround(dev, skb) (skb)
> +#endif
Another use of #ifdef blocks. What is the multiplatform impact?
g.
--
Grant Likely, B.Sc., P.Eng.
Secret Lab Technologies Ltd.
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