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