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net: fec: add dma_wmb to ensure correct descriptor values

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Two dma_wmb() are added in the XDP TX path to ensure proper ordering of
descriptor and buffer updates:
1. A dma_wmb() is added after updating the last BD to make sure
   the updates to rest of the descriptor are visible before
   transferring ownership to FEC.
2. A dma_wmb() is also added after updating the bdp to ensure these
   updates are visible before updating txq->bd.cur.
3. Start the xmit of the frame immediately right after configuring the
   tx descriptor.

Fixes: 6d6b39f180 ("net: fec: add initial XDP support")
Signed-off-by: Shenwei Wang <shenwei.wang@nxp.com>
Reviewed-by: Wei Fang <wei.fang@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Shenwei Wang 2023-05-18 10:02:02 -05:00 • committed by David S. Miller
parent 3be5f6cd4a
commit 9025944fdd
1 changed files with 11 additions and 6 deletions
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17
drivers/net/ethernet/freescale/fec_main.c
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@ -3834,6 +3834,11 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
index = fec_enet_get_bd_index(last_bdp, &txq->bd);
txq->tx_skbuff[index] = NULL;
/* Make sure the updates to rest of the descriptor are performed before
* transferring ownership.
*/
dma_wmb();
/* Send it on its way. Tell FEC it's ready, interrupt when done,
* it's the last BD of the frame, and to put the CRC on the end.
*/
@ -3843,8 +3848,14 @@ static int fec_enet_txq_xmit_frame(struct fec_enet_private *fep,
/* If this was the last BD in the ring, start at the beginning again. */
bdp = fec_enet_get_nextdesc(last_bdp, &txq->bd);
/* Make sure the update to bdp are performed before txq->bd.cur. */
dma_wmb();
txq->bd.cur = bdp;
/* Trigger transmission start */
writel(0, txq->bd.reg_desc_active);
return 0;
}
@ -3873,12 +3884,6 @@ static int fec_enet_xdp_xmit(struct net_device *dev,
sent_frames++;
}
/* Make sure the update to bdp and tx_skbuff are performed. */
wmb();
/* Trigger transmission start */
writel(0, txq->bd.reg_desc_active);
__netif_tx_unlock(nq);
return sent_frames;