target/linux/layerscape/patches-5.4/701-net-0047-sdk_dpaa-update-comments-about-recycling-and-back-po.patch

   1 From 2d7b6e7daf076b63f461ce9c4ec6022ddc3d15bb Mon Sep 17 00:00:00 2001
   2 From: Camelia Groza <camelia.groza@nxp.com>
   3 Date: Mon, 15 Jan 2018 17:42:42 +0200
   4 Subject: [PATCH] sdk_dpaa: update comments about recycling and back-pointer
   5  storage
   6
   7 Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
   8 ---
   9  drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c | 18 ++++++++++++++++--
  10  1 file changed, 16 insertions(+), 2 deletions(-)
  11
  12 --- a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c
  13 +++ b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c
  14 @@ -121,6 +121,10 @@ static int _dpa_bp_add_8_bufs(const stru
  15                         put_page(virt_to_head_page(new_buf));
  16                         goto build_skb_failed;
  17                 }
  18 +
  19 +               /* Store the skb back-pointer before the start of the buffer.
  20 +                * Otherwise it will be overwritten by the FMan.
  21 +                */
  22                 DPA_WRITE_SKB_PTR(skb, skbh, new_buf, -1);
  23
  24                 addr = dma_map_single(dev, new_buf,
  25 @@ -344,7 +348,10 @@ bool dpa_buf_is_recyclable(struct sk_buf
  26          * - buffer address aligned to cacheline bytes
  27          * - offset of data from start of buffer no lower than a minimum value
  28          * - offset of data from start of buffer no higher than a maximum value
  29 +        * - the skb back-pointer is stored safely
  30          */
  31 +
  32 +       /* guarantee both the minimum size and the minimum data offset */
  33         new = min(skb_end_pointer(skb) - min_size, skb->data - min_offset);
  34
  35         /* left align to the nearest cacheline */
  36 @@ -694,6 +701,9 @@ int __hot skb_to_contig_fd(struct dpa_pr
  37                 dma_dir = DMA_BIDIRECTIONAL;
  38                 dma_map_size = dpa_bp->size;
  39
  40 +               /* Store the skb back-pointer before the start of the buffer.
  41 +                * Otherwise it will be overwritten by the FMan.
  42 +                */
  43                 DPA_WRITE_SKB_PTR(skb, skbh, buffer_start, -1);
  44                 *offset = skb_headroom(skb) - fd->offset;
  45         } else
  46 @@ -711,7 +721,7 @@ int __hot skb_to_contig_fd(struct dpa_pr
  47
  48                 /* The buffer will be Tx-confirmed, but the TxConf cb must
  49                  * necessarily look at our Tx private data to retrieve the
  50 -                * skbuff. (In short: can't use DPA_WRITE_SKB_PTR() here.)
  51 +                * skbuff. Store the back-pointer inside the buffer.
  52                  */
  53                 DPA_WRITE_SKB_PTR(skb, skbh, buffer_start, 0);
  54         }
  55 @@ -975,7 +985,11 @@ int __hot skb_to_sg_fd(struct dpa_priv_s
  56         fd->length20 = skb->len;
  57         fd->offset = priv->tx_headroom;
  58
  59 -       /* DMA map the SGT page */
  60 +       /* DMA map the SGT page
  61 +        *
  62 +        * It's safe to store the skb back-pointer inside the buffer since
  63 +        * S/G frames are non-recyclable.
  64 +        */
  65         DPA_WRITE_SKB_PTR(skb, skbh, sgt_buf, 0);
  66         addr = dma_map_single(dpa_bp->dev, sgt_buf,
  67                               priv->tx_headroom + sgt_size,