68 lines
2.5 KiB
Diff
68 lines
2.5 KiB
Diff
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From 2d7b6e7daf076b63f461ce9c4ec6022ddc3d15bb Mon Sep 17 00:00:00 2001
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From: Camelia Groza <camelia.groza@nxp.com>
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Date: Mon, 15 Jan 2018 17:42:42 +0200
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Subject: [PATCH] sdk_dpaa: update comments about recycling and back-pointer
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storage
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Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
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---
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drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c | 18 ++++++++++++++++--
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1 file changed, 16 insertions(+), 2 deletions(-)
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--- a/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c
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+++ b/drivers/net/ethernet/freescale/sdk_dpaa/dpaa_eth_sg.c
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@@ -121,6 +121,10 @@ static int _dpa_bp_add_8_bufs(const stru
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put_page(virt_to_head_page(new_buf));
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goto build_skb_failed;
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}
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+
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+ /* Store the skb back-pointer before the start of the buffer.
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+ * Otherwise it will be overwritten by the FMan.
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+ */
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DPA_WRITE_SKB_PTR(skb, skbh, new_buf, -1);
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addr = dma_map_single(dev, new_buf,
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@@ -344,7 +348,10 @@ bool dpa_buf_is_recyclable(struct sk_buf
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* - buffer address aligned to cacheline bytes
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* - offset of data from start of buffer no lower than a minimum value
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* - offset of data from start of buffer no higher than a maximum value
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+ * - the skb back-pointer is stored safely
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*/
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+
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+ /* guarantee both the minimum size and the minimum data offset */
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new = min(skb_end_pointer(skb) - min_size, skb->data - min_offset);
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/* left align to the nearest cacheline */
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@@ -694,6 +701,9 @@ int __hot skb_to_contig_fd(struct dpa_pr
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dma_dir = DMA_BIDIRECTIONAL;
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dma_map_size = dpa_bp->size;
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+ /* Store the skb back-pointer before the start of the buffer.
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+ * Otherwise it will be overwritten by the FMan.
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+ */
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DPA_WRITE_SKB_PTR(skb, skbh, buffer_start, -1);
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*offset = skb_headroom(skb) - fd->offset;
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} else
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@@ -711,7 +721,7 @@ int __hot skb_to_contig_fd(struct dpa_pr
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/* The buffer will be Tx-confirmed, but the TxConf cb must
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* necessarily look at our Tx private data to retrieve the
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- * skbuff. (In short: can't use DPA_WRITE_SKB_PTR() here.)
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+ * skbuff. Store the back-pointer inside the buffer.
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*/
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DPA_WRITE_SKB_PTR(skb, skbh, buffer_start, 0);
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}
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@@ -975,7 +985,11 @@ int __hot skb_to_sg_fd(struct dpa_priv_s
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fd->length20 = skb->len;
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fd->offset = priv->tx_headroom;
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- /* DMA map the SGT page */
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+ /* DMA map the SGT page
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+ *
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+ * It's safe to store the skb back-pointer inside the buffer since
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+ * S/G frames are non-recyclable.
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+ */
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DPA_WRITE_SKB_PTR(skb, skbh, sgt_buf, 0);
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addr = dma_map_single(dpa_bp->dev, sgt_buf,
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priv->tx_headroom + sgt_size,
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