From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [net-next-2.6 PATCH v2 3/3] fs_enet: add FEC TX buffer alignment workaround for MPC5121 Date: Wed, 17 Feb 2010 16:17:16 +0100 Message-ID: <1266419836.3075.12.camel@edumazet-laptop> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: netdev@vger.kernel.org, linuxppc-dev@ozlabs.org, "David S. Miller" , Grant Likely , Detlev Zundel , Wolfgang Denk , John Rigby , Piotr Ziecik To: Anatolij Gustschin Return-path: Received: from mail-bw0-f219.google.com ([209.85.218.219]:36418 "EHLO mail-bw0-f219.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757346Ab0BQPRX (ORCPT ); Wed, 17 Feb 2010 10:17:23 -0500 Received: by bwz19 with SMTP id 19so5608901bwz.28 for ; Wed, 17 Feb 2010 07:17:20 -0800 (PST) In-Reply-To: <1266418530-2727-4-git-send-email-agust@denx.de> Sender: netdev-owner@vger.kernel.org List-ID: Le mercredi 17 f=C3=A9vrier 2010 =C3=A0 15:55 +0100, Anatolij Gustschin= a =C3=A9crit : > 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. >=20 > 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(-) >=20 > 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) > =20 > /*******************************************************************= ***************/ > =20 > +#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 *de= v, > + struct sk_buff *skb) > +{ > + struct sk_buff *new_skb; > + struct fs_enet_private *fep =3D netdev_priv(dev); > + > + /* Alloc new skb */ > + new_skb =3D 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 =3D netdev_priv(dev); > @@ -588,6 +619,19 @@ static int fs_enet_start_xmit(struct sk_buff *sk= b, struct net_device *dev) > u16 sc; > unsigned long flags; > =20 > +#ifdef CONFIG_FS_ENET_MPC5121_FEC > + if (((unsigned long)skb->data) & 0x3) { > + skb =3D 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); > =20 > /*