Re: [net-next-2.6 PATCH v2 3/3] fs_enet: add FEC TX buffer alignment workaround for MPC5121
From: Eric Dumazet <hidden>
Date: 2010-02-17 15:17:22
Also in:
netdev
Le mercredi 17 février 2010 à 15:55 +0100, Anatolij Gustschin a écrit :
quoted hunk ↗ jump to hunk
MPC5121 FEC requeries 4-byte alignmnent for TX data buffers. This patch is a work around that copies misaligned tx packets to an aligned skb before sending. Signed-off-by: John Rigby <redacted> Signed-off-by: Piotr Ziecik <redacted> Signed-off-by: Wolfgang Denk <redacted> Signed-off-by: Anatolij Gustschin <agust@denx.de> --- drivers/net/fs_enet/fs_enet-main.c | 44 ++++++++++++++++++++++++++++++++++++ 1 files changed, 44 insertions(+), 0 deletions(-)diff --git a/drivers/net/fs_enet/fs_enet-main.c b/drivers/net/fs_enet/fs_enet-main.c index 4297021..166a89d 100644 --- a/drivers/net/fs_enet/fs_enet-main.c +++ b/drivers/net/fs_enet/fs_enet-main.c@@ -580,6 +580,37 @@ void fs_cleanup_bds(struct net_device *dev) /**********************************************************************************/ +#ifdef CONFIG_FS_ENET_MPC5121_FEC +/* + * MPC5121 FEC requeries 4-byte alignment for TX data buffer! + */ +static struct sk_buff *tx_skb_align_workaround(struct net_device *dev, + struct sk_buff *skb) +{ + struct sk_buff *new_skb; + struct fs_enet_private *fep = netdev_priv(dev); + + /* Alloc new skb */ + new_skb = dev_alloc_skb(ENET_RX_FRSIZE + 4);
ENET_RX_FRSIZE looks strange in TX path Why not using skb->len + 4 instead of ENET_RX_FRSIZE + 4 ?
+ if (!new_skb) {
+ dev_warn(fep->dev, "Memory squeeze, dropping tx packet.\n");I am just wondering if this is ratelimited ?
+ return NULL; + } + + /* Make sure new skb is properly aligned */ + skb_align(new_skb, 4);
quoted hunk ↗ jump to hunk
+ + /* 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; +} +#endif + static int fs_enet_start_xmit(struct sk_buff *skb, struct net_device *dev) { struct fs_enet_private *fep = netdev_priv(dev);@@ -588,6 +619,19 @@ static int fs_enet_start_xmit(struct sk_buff *skb, struct net_device *dev) u16 sc; unsigned long flags; +#ifdef CONFIG_FS_ENET_MPC5121_FEC + if (((unsigned long)skb->data) & 0x3) { + skb = tx_skb_align_workaround(dev, skb); + if (!skb) { + /* + * We have lost packet due to memory allocation error + * in tx_skb_align_workaround(). Hopefully original + * skb is still valid, so try transmit it later. + */
Could you define 'try to transmit later' ? Who is responsible to trigger this event ?
+ return NETDEV_TX_BUSY; + } + } +#endif spin_lock_irqsave(&fep->tx_lock, flags); /*