[PATCH net-next 1/4] dpaa_eth: fix SG mapping

[Madalin Bucur]

An issue in the code mapping the skb fragments into
scatter-gather frames was evidentiated by netperf
TCP_SENDFILE tests. This patch addresses the issue.

Signed-off-by: Madalin Bucur <madalin.bu...@nxp.com>
---
 drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 27 ++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c 
b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index a998c36..a5afa60 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -1889,7 +1889,7 @@ static int skb_to_sg_fd(struct dpaa_priv *priv,
        void *buffer_start;
        skb_frag_t *frag;
        dma_addr_t addr;
-       size_t frag_len;
+       size_t buff_len;
        void *sgt_buf;
 
        /* get a page frag to store the SGTable */
@@ -1916,8 +1916,10 @@ static int skb_to_sg_fd(struct dpaa_priv *priv,
                goto csum_failed;
        }
 
+       /* SGT[0] is used by the linear part */
        sgt = (struct qm_sg_entry *)(sgt_buf + priv->tx_headroom);
-       qm_sg_entry_set_len(&sgt[0], skb_headlen(skb));
+       buff_len = skb_headlen(skb);
+       qm_sg_entry_set_len(&sgt[0], buff_len);
        sgt[0].bpid = FSL_DPAA_BPID_INV;
        sgt[0].offset = 0;
        addr = dma_map_single(dev, skb->data,
@@ -1930,27 +1932,28 @@ static int skb_to_sg_fd(struct dpaa_priv *priv,
        qm_sg_entry_set64(&sgt[0], addr);
 
        /* populate the rest of SGT entries */
-       frag = &skb_shinfo(skb)->frags[0];
-       frag_len = frag->size;
-       for (i = 1; i <= nr_frags; i++, frag++) {
+       for (i = 0; i < nr_frags; i++) {
+               frag = &skb_shinfo(skb)->frags[i];
+               buff_len = frag->size;
                WARN_ON(!skb_frag_page(frag));
                addr = skb_frag_dma_map(dev, frag, 0,
-                                       frag_len, dma_dir);
+                                       buff_len, dma_dir);
                if (unlikely(dma_mapping_error(dev, addr))) {
                        dev_err(dev, "DMA mapping failed");
                        err = -EINVAL;
                        goto sg_map_failed;
                }
 
-               qm_sg_entry_set_len(&sgt[i], frag_len);
-               sgt[i].bpid = FSL_DPAA_BPID_INV;
-               sgt[i].offset = 0;
+               qm_sg_entry_set_len(&sgt[i + 1], buff_len);
+               sgt[i + 1].bpid = FSL_DPAA_BPID_INV;
+               sgt[i + 1].offset = 0;
 
                /* keep the offset in the address */
-               qm_sg_entry_set64(&sgt[i], addr);
-               frag_len = frag->size;
+               qm_sg_entry_set64(&sgt[i + 1], addr);
        }
-       qm_sg_entry_set_f(&sgt[i - 1], frag_len);
+
+       /* Set the final bit in the last used entry of the SGT */
+       qm_sg_entry_set_f(&sgt[nr_frags], buff_len);
 
        qm_fd_set_sg(fd, priv->tx_headroom, skb->len);
 
-- 
2.1.0