[PATCH v2] gianfar: Fall back to software tcp/udp checksum on older controllers

As specified by errata eTSEC49 of MPC8548 and errata eTSEC12 of MPC83xx,=0A=
older revisions of gianfar controllers will be unable to calculate a TCP/UD=
P=0Apacket checksum for some alignments of the appropriate FCB. This patch =
checks=0Afor FCB alignment on such controllers and falls back to software c=
hecksumming=0Aif the alignment is known to be bad.=0A=0ASigned-off-by: Alex=
 Dubov [off-list ref]=0A---=0ACan we, please, proceed with this patch?=
=0AThe issue is badly annoying, breaking quite a few of the MPC8548 chips.=
=0A=0AChanges for v2:=0A   - Make indentation slightly more consistent.=0A =
  - Replace bizarre switch-based condition with plain boring one.=0A=0A dri=
vers/net/gianfar.c |   16 ++++++++++++++--=0A drivers/net/gianfar.h |    1 =
+=0A 2 files changed, 15 insertions(+), 2 deletions(-)=0A=0Adiff --git a/dr=
ivers/net/gianfar.c b/drivers/net/gianfar.c=0Aindex 5ed8f9f..3da19a5 100644=
=0A--- a/drivers/net/gianfar.c=0A+++ b/drivers/net/gianfar.c=0A@@ -950,6 +9=
50,11 @@ static void gfar_detect_errata(struct gfar_private *priv)=0A =09=
=09=09(pvr =3D=3D 0x80861010 && (mod & 0xfff9) =3D=3D 0x80c0))=0A =09=09pri=
v->errata |=3D GFAR_ERRATA_A002;=0A =0A+=09/* MPC8313 Rev < 2.0, MPC8548 re=
v 2.0 */=0A+=09if ((pvr =3D=3D 0x80850010 && mod =3D=3D 0x80b0 && rev < 0x0=
020) ||=0A+=09=09=09(pvr =3D=3D 0x80210020 && mod =3D=3D 0x8030 && rev =3D=
=3D 0x0020))=0A+=09=09priv->errata |=3D GFAR_ERRATA_12;=0A+=0A =09if (priv-=

errata)=0A =09=09dev_info(dev, "enabled errata workarounds, flags: 0x%x\n"=

,=0A =09=09=09 priv->errata);=0A@@ -2156,8 +2161,15 @@ static int gfar_star=
t_xmit(struct sk_buff *skb, struct net_device *dev)=0A =09/* Set up checksu=
mming */=0A =09if (CHECKSUM_PARTIAL =3D=3D skb->ip_summed) {=0A =09=09fcb =
=3D gfar_add_fcb(skb);=0A-=09=09lstatus |=3D BD_LFLAG(TXBD_TOE);=0A-=09=09g=
far_tx_checksum(skb, fcb);=0A+=09=09/* as specified by errata */=0A+=09=09i=
f (unlikely(gfar_has_errata(priv, GFAR_ERRATA_12)=0A+=09=09=09     && ((uns=
igned long)fcb % 0x20) > 0x18)) {=0A+=09=09=09__skb_pull(skb, GMAC_FCB_LEN)=
;=0A+=09=09=09skb_checksum_help(skb);=0A+=09=09} else {=0A+=09=09=09lstatus=
 |=3D BD_LFLAG(TXBD_TOE);=0A+=09=09=09gfar_tx_checksum(skb, fcb);=0A+=09=09=
}=0A =09}=0A =0A =09if (vlan_tx_tag_present(skb)) {=0Adiff --git a/drivers/=
net/gianfar.h b/drivers/net/gianfar.h=0Aindex 54de413..ec5d595 100644=0A---=
 a/drivers/net/gianfar.h=0A+++ b/drivers/net/gianfar.h=0A@@ -1039,6 +1039,7=
 @@ enum gfar_errata {=0A =09GFAR_ERRATA_74=09=09=3D 0x01,=0A =09GFAR_ERRAT=
A_76=09=09=3D 0x02,=0A =09GFAR_ERRATA_A002=09=3D 0x04,=0A+=09GFAR_ERRATA_12=
=09=09=3D 0x08, /* a.k.a errata eTSEC49 */=0A };=0A =0A /* Struct stolen al=
most completely (and shamelessly) from the FCC enet source=0A-- =0A1.7.3.2=
=0A=0A=0A=0A=0A      

From: Alex Dubov <oakad@yahoo.com>
Date: Wed, 16 Mar 2011 20:57:13 -0700 (PDT)

As specified by errata eTSEC49 of MPC8548 and errata eTSEC12 of MPC83xx,
older revisions of gianfar controllers will be unable to calculate a TCP/UDP
packet checksum for some alignments of the appropriate FCB. This patch checks
for FCB alignment on such controllers and falls back to software checksumming
if the alignment is known to be bad.

Signed-off-by: Alex Dubov <oakad@yahoo.com>

Applied.