| b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame] | 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, |