From bdd7f3bbbe9aa2168cc8a6f56feee9b295facedb Mon Sep 17 00:00:00 2001
From: Ioana Radulescu <ruxandra.radulescu@freescale.com>
Date: Tue, 30 Jul 2013 16:20:57 +0300
Subject: dpaa_eth: Reorder recycling conditions

Reorganize a bit the recycling code without any actual changes in
the logic.
Reordering of conditions based on which is most likely to fail first
brings a bit of performance improvement in case no recycling is
actually done.

Signed-off-by: Ioana Radulescu <ruxandra.radulescu@freescale.com>
Change-Id: I6cf3995576b756d9aec678f92f679ee1fa461587
Reviewed-on: http://git.am.freescale.net:8181/4188
Tested-by: Review Code-CDREVIEW <CDREVIEW@freescale.com>
Reviewed-by: Bucur Madalin-Cristian-B32716 <madalin.bucur@freescale.com>
Reviewed-by: Rivera Jose-B46482 <German.Rivera@freescale.com>
Reviewed-on: http://git.am.freescale.net:8181/4465
Reviewed-by: Sovaiala Cristian-Constantin-B39531 <Cristian.Sovaiala@freescale.com>

diff --git a/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c b/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c
index 09214d3..a2fd990 100644
--- a/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c
+++ b/drivers/net/ethernet/freescale/dpa/dpaa_eth_sg.c
@@ -272,7 +272,11 @@ struct sk_buff *_dpa_cleanup_tx_fd(const struct dpa_priv_s *priv,
 #ifndef CONFIG_FSL_DPAA_TS
 static bool dpa_skb_is_recyclable(struct sk_buff *skb)
 {
-	/* No recycling possible if skb has an userspace buffer */
+	/* No recycling possible if skb buffer is kmalloc'ed  */
+	if (skb->head_frag == 0)
+		return false;
+
+	/* or if it's an userspace buffer */
 	if (skb_shinfo(skb)->tx_flags & SKBTX_DEV_ZEROCOPY)
 		return false;
 
@@ -281,10 +285,6 @@ static bool dpa_skb_is_recyclable(struct sk_buff *skb)
 	    skb->fclone != SKB_FCLONE_UNAVAILABLE)
 		return false;
 
-	/* or if it's kmalloc'ed  */
-	if (skb->head_frag == 0)
-		return false;
-
 	return true;
 }
 
@@ -602,40 +602,40 @@ static int __hot skb_to_contig_fd(struct dpa_priv_s *priv,
 	int *count_ptr = __this_cpu_ptr(dpa_bp->percpu_count);
 	unsigned char *rec_buf_start;
 
-	/* We are guaranteed to have at least tx_headroom bytes */
-	skbh = (struct sk_buff **)(skb->data - priv->tx_headroom);
-	fd->offset = priv->tx_headroom;
-
 #ifndef CONFIG_FSL_DPAA_TS
 	/* Check recycling conditions; only if timestamp support is not
 	 * enabled, otherwise we need the fd back on tx confirmation
 	 */
 
-	/* We cannot recycle the buffer if the pool is already full */
-	if (unlikely(*count_ptr >= dpa_bp->target_count))
-		goto no_recycle;
-
-	/* ... or if the skb doesn't meet the recycling criteria */
-	if (unlikely(!dpa_skb_is_recyclable(skb)))
-		goto no_recycle;
-
-	/* ... or if buffer recycling conditions are not met */
-	if (unlikely(!dpa_buf_is_recyclable(skb, dpa_bp->size,
-			priv->tx_headroom, &rec_buf_start)))
-		goto no_recycle;
-
-	/* Buffer is recyclable; use the new start address */
-	skbh = (struct sk_buff **)rec_buf_start;
-
-	/* and set fd parameters and DMA mapping direction */
-	fd->cmd |= FM_FD_CMD_FCO;
-	fd->bpid = dpa_bp->bpid;
-	BUG_ON(skb->data - rec_buf_start > DPA_MAX_FD_OFFSET);
-	fd->offset = (uint16_t)(skb->data - rec_buf_start);
-	dma_dir = DMA_BIDIRECTIONAL;
+	/* We can recycle the buffer if:
+	 * - the pool is not full
+	 * - the buffer meets the skb recycling conditions
+	 * - the buffer meets our own (size, offset, align) conditions
+	 */
+	if (likely((*count_ptr < dpa_bp->target_count) &&
+		   dpa_skb_is_recyclable(skb) &&
+		   dpa_buf_is_recyclable(skb, dpa_bp->size,
+					 priv->tx_headroom, &rec_buf_start))) {
+		/* Buffer is recyclable; use the new start address */
+		skbh = (struct sk_buff **)rec_buf_start;
+
+		/* and set fd parameters and DMA mapping direction */
+		fd->cmd |= FM_FD_CMD_FCO;
+		fd->bpid = dpa_bp->bpid;
+		BUG_ON(skb->data - rec_buf_start > DPA_MAX_FD_OFFSET);
+		fd->offset = (uint16_t)(skb->data - rec_buf_start);
+		dma_dir = DMA_BIDIRECTIONAL;
+	} else
 #endif
+	{
+		/* Not recyclable.
+		 * We are guaranteed to have at least tx_headroom bytes
+		 * available, so just use that for offset.
+		 */
+		skbh = (struct sk_buff **)(skb->data - priv->tx_headroom);
+		fd->offset = priv->tx_headroom;
+	}
 
-no_recycle:
 	*skbh = skb;
 
 	/* Enable L3/L4 hardware checksum computation.
@@ -651,7 +651,7 @@ no_recycle:
 		return err;
 	}
 
-	/* Fill in the FD */
+	/* Fill in the rest of the FD fields */
 	fd->format = qm_fd_contig;
 	fd->length20 = skb->len;
 
-- 
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