gianfar: Cleanup TxFCB insertion on xmit

Cleanup gfar_start_xmit()'s fast path by factoring out "redundant"
FCB insertion code (repeated gfar_add_fcb() calls and related)
and by reducing the number of if() clauses (i.e. if(fcb) checks).
Improve maintainability (e.g. there's less code and easier to read)
also by introducing do_csum and do_vlan to mark the other 2 Tx TOE
functionalities, following the same model as do_tstamp.
fcb_len may also be 0 now, to mark that Tx FCB insertion conditions
(do_csum, do_vlan, do_tstamp) have not been met.

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

1 files changed, 33 insertions, 29 deletions

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 352035e440d8..3cb464780777 100644
--- a/drivers/net/ethernet/freescale/gianfar.c
+++ b/drivers/net/ethernet/freescale/gianfar.c
@@ -2081,10 +2081,11 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         struct txfcb *fcb = NULL;
         struct txbd8 *txbdp, *txbdp_start, *base, *txbdp_tstamp = NULL;
         u32 lstatus;
-        int i, rq = 0, do_tstamp = 0;
+        int i, rq = 0;
+        int do_tstamp, do_csum, do_vlan;
         u32 bufaddr;
         unsigned long flags;
-        unsigned int nr_frags, nr_txbds, length, fcb_length = GMAC_FCB_LEN;
+        unsigned int nr_frags, nr_txbds, length, fcb_len = 0;
 
         rq = skb->queue_mapping;
         tx_queue = priv->tx_queue[rq];
@@ -2092,21 +2093,23 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
         base = tx_queue->tx_bd_base;
         regs = tx_queue->grp->regs;
 
+        do_csum = (CHECKSUM_PARTIAL == skb->ip_summed);
+        do_vlan = vlan_tx_tag_present(skb);
+        do_tstamp = (skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) &&
+                    priv->hwts_tx_en;
+
+        if (do_csum || do_vlan)
+                fcb_len = GMAC_FCB_LEN;
+
         /* check if time stamp should be generated */
-        if (unlikely(skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP &&
-                     priv->hwts_tx_en)) {
-                do_tstamp = 1;
-                fcb_length = GMAC_FCB_LEN + GMAC_TXPAL_LEN;
-        }
+        if (unlikely(do_tstamp))
+                fcb_len = GMAC_FCB_LEN + GMAC_TXPAL_LEN;
 
         /* make space for additional header when fcb is needed */
-        if (((skb->ip_summed == CHECKSUM_PARTIAL) ||
-             vlan_tx_tag_present(skb) ||
-             unlikely(do_tstamp)) &&
-            (skb_headroom(skb) < fcb_length)) {
+        if (fcb_len && unlikely(skb_headroom(skb) < fcb_len)) {
                 struct sk_buff *skb_new;
 
-                skb_new = skb_realloc_headroom(skb, fcb_length);
+                skb_new = skb_realloc_headroom(skb, fcb_len);
                 if (!skb_new) {
                         dev->stats.tx_errors++;
                         kfree_skb(skb);
@@ -2189,37 +2192,38 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
                 memset(skb->data, 0, GMAC_TXPAL_LEN);
         }
 
-        /* Set up checksumming */
-        if (CHECKSUM_PARTIAL == skb->ip_summed) {
+        /* Add TxFCB if required */
+        if (fcb_len) {
                 fcb = gfar_add_fcb(skb);
                 lstatus |= BD_LFLAG(TXBD_TOE);
-                gfar_tx_checksum(skb, fcb, fcb_length);
+        }
+
+        /* Set up checksumming */
+        if (do_csum) {
+                gfar_tx_checksum(skb, fcb, fcb_len);
 
                 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);
-                        lstatus &= ~(BD_LFLAG(TXBD_TOE));
-                        fcb = NULL;
+                        if (do_vlan || do_tstamp) {
+                                /* put back a new fcb for vlan/tstamp TOE */
+                                fcb = gfar_add_fcb(skb);
+                        } else {
+                                /* Tx TOE not used */
+                                lstatus &= ~(BD_LFLAG(TXBD_TOE));
+                                fcb = NULL;
+                        }
                 }
         }
 
-        if (vlan_tx_tag_present(skb)) {
-                if (unlikely(NULL == fcb)) {
-                        fcb = gfar_add_fcb(skb);
-                        lstatus |= BD_LFLAG(TXBD_TOE);
-                }
-
+        if (do_vlan)
                 gfar_tx_vlan(skb, fcb);
-        }
 
         /* Setup tx hardware time stamping if requested */
         if (unlikely(do_tstamp)) {
                 skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;
-                if (fcb == NULL)
-                        fcb = gfar_add_fcb(skb);
                 fcb->ptp = 1;
-                lstatus |= BD_LFLAG(TXBD_TOE);
         }
 
         txbdp_start->bufPtr = dma_map_single(priv->dev, skb->data,
@@ -2231,9 +2235,9 @@ static int gfar_start_xmit(struct sk_buff *skb, struct net_device *dev)
          * the full frame length.
          */
         if (unlikely(do_tstamp)) {
-                txbdp_tstamp->bufPtr = txbdp_start->bufPtr + fcb_length;
+                txbdp_tstamp->bufPtr = txbdp_start->bufPtr + fcb_len;
                 txbdp_tstamp->lstatus |= BD_LFLAG(TXBD_READY) |
-                                         (skb_headlen(skb) - fcb_length);
+                                         (skb_headlen(skb) - fcb_len);
                 lstatus |= BD_LFLAG(TXBD_CRC | TXBD_READY) | GMAC_FCB_LEN;
         } else {
                 lstatus |= BD_LFLAG(TXBD_CRC | TXBD_READY) | skb_headlen(skb);