gianfar: Fix Tx csum generation errata handling

Both [eTSEC76] and [eTSEC12] errata relate to Tx checksum generation
(for some MPC83xx and MCP8548 older revisions). They require the same
workaround: manual checksum computation and insertion, and disabling
the H/W Tx csum acceleration feature (per frame) through Tx FCB
(Frame Control Block) csum offload settings.

The workaround for [eTSEC76] needs to be fixed because it currently
fails to disable H/W Tx csum insertion via FCB. This patch fixes it
and provides a common workaround implementation for both Tx csum errata.

Signed-off-by: Claudiu Manoil <claudiu.manoil@freescale.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 19 deletions

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index dbb34f7ce448..352035e440d8 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -2051,6 +2051,24 @@ static inline struct txbd8 *next_txbd(struct txbd8 *bdp, struct txbd8 *base,
         return skip_txbd(bdp, 1, base, ring_size);
 }
 
+/* eTSEC12: csum generation not supported for some fcb offsets */
+static inline bool gfar_csum_errata_12(struct gfar_private *priv,
+                                       unsigned long fcb_addr)
+{
+        return (gfar_has_errata(priv, GFAR_ERRATA_12) &&
+               (fcb_addr % 0x20) > 0x18);
+}
+
+/* eTSEC76: csum generation for frames larger than 2500 may
+ * cause excess delays before start of transmission
+ */
+static inline bool gfar_csum_errata_76(struct gfar_private *priv,
+                                       unsigned int len)
+{
+        return (gfar_has_errata(priv, GFAR_ERRATA_76) &&
+               (len > 2500));
+}
+
 /* This is called by the kernel when a frame is ready for transmission.
  * It is pointed to by the dev->hard_start_xmit function pointer
  */
@@ -2068,19 +2086,6 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         unsigned long flags;
         unsigned int nr_frags, nr_txbds, length, fcb_length = GMAC_FCB_LEN;
 
-        /* TOE=1 frames larger than 2500 bytes may see excess delays
-         * before start of transmission.
-         */
-        if (unlikely(gfar_has_errata(priv, GFAR_ERRATA_76) &&
-                     skb->ip_summed == CHECKSUM_PARTIAL &&
-                     skb->len > 2500)) {
-                int ret;
-
-                ret = skb_checksum_help(skb);
-                if (ret)
-                        return ret;
-        }
-
         rq = skb->queue_mapping;
         tx_queue = priv->tx_queue[rq];
         txq = netdev_get_tx_queue(dev, rq);
@@ -2187,14 +2192,15 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         /* Set up checksumming */
         if (CHECKSUM_PARTIAL == skb->ip_summed) {
                 fcb = gfar_add_fcb(skb);
-                /* as specified by errata */
-                if (unlikely(gfar_has_errata(priv, GFAR_ERRATA_12) &&
-                             ((unsigned long)fcb % 0x20) > 0x18)) {
+                lstatus |= BD_LFLAG(TXBD_TOE);
+                gfar_tx_checksum(skb, fcb, fcb_length);
+
+                if (unlikely(gfar_csum_errata_12(priv, (unsigned long)fcb)) ||
+                    unlikely(gfar_csum_errata_76(priv, skb->len))) {
                         __skb_pull(skb, GMAC_FCB_LEN);
                         skb_checksum_help(skb);
-                } else {
-                        lstatus |= BD_LFLAG(TXBD_TOE);
-                        gfar_tx_checksum(skb, fcb, fcb_length);
+                        lstatus &= ~(BD_LFLAG(TXBD_TOE));
+                        fcb = NULL;
                 }
         }