From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bw0-f212.google.com (mail-bw0-f212.google.com [209.85.218.212]) by ozlabs.org (Postfix) with ESMTP id E2AFCB7D59 for ; Thu, 18 Feb 2010 02:17:22 +1100 (EST) Received: by bwz4 with SMTP id 4so118830bwz.22 for ; Wed, 17 Feb 2010 07:17:20 -0800 (PST) Subject: Re: [net-next-2.6 PATCH v2 3/3] fs_enet: add FEC TX buffer alignment workaround for MPC5121 From: Eric Dumazet To: Anatolij Gustschin In-Reply-To: <1266418530-2727-4-git-send-email-agust@denx.de> References: <1266418530-2727-1-git-send-email-agust@denx.de> <1266418530-2727-2-git-send-email-agust@denx.de> <1266418530-2727-3-git-send-email-agust@denx.de> <1266418530-2727-4-git-send-email-agust@denx.de> Content-Type: text/plain; charset="UTF-8" Date: Wed, 17 Feb 2010 16:17:16 +0100 Message-ID: <1266419836.3075.12.camel@edumazet-laptop> Mime-Version: 1.0 Cc: Wolfgang Denk , Detlev Zundel , netdev@vger.kernel.org, linuxppc-dev@ozlabs.org, "David S. Miller" , Piotr Ziecik List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Le mercredi 17 février 2010 à 15:55 +0100, Anatolij Gustschin a écrit : > 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 > Signed-off-by: Piotr Ziecik > Signed-off-by: Wolfgang Denk > Signed-off-by: Anatolij Gustschin > --- > 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); > + > + /* 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); > > /*