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>

diff --git a/drivers/net/ethernet/freescale/gianfar.c b/drivers/net/ethernet/freescale/gianfar.c
index 352035e440d89fd1d8245fec0b3043ab69f7e163..3cb464780777cbcbe7b2be4567ed381150d58f0b 100644 (file)
--- 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);