netdev - [PATCH net v2 2/3] dpaa_eth: reduce data alignment requirements for the A050385 erratum

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Message-Id: <07da2fe94891ddaeed1140544a7c6ffa156a6711.1612456902.git.camelia.groza@nxp.com>
Date:   Thu,  4 Feb 2021 18:49:27 +0200
From:   Camelia Groza <camelia.groza@....com>
To:     kuba@...nel.org, davem@...emloft.net, maciej.fijalkowski@...el.com
Cc:     madalin.bucur@....nxp.com, netdev@...r.kernel.org,
        Camelia Groza <camelia.groza@....com>
Subject: [PATCH net v2 2/3] dpaa_eth: reduce data alignment requirements for the A050385 erratum

The 256 byte data alignment is required for preventing DMA transaction
splits when crossing 4K page boundaries. Since XDP deals only with page
sized buffers or less, this restriction isn't needed. Instead, the data
only needs to be aligned to 64 bytes to prevent DMA transaction splits.

These lessened restrictions can increase performance by widening the pool
of permitted data alignments and preventing unnecessary realignments.

Fixes: ae680bcbd06a ("dpaa_eth: implement the A050385 erratum workaround for XDP")
Signed-off-by: Camelia Groza <camelia.groza@....com>
Acked-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
---
 drivers/net/ethernet/freescale/dpaa/dpaa_eth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
index f3a879937d8d..2a2c7db23407 100644
--- a/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
+++ b/drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
@@ -2192,7 +2192,7 @@ static int dpaa_a050385_wa_xdpf(struct dpaa_priv *priv,
 	 * byte frame headroom. If the XDP program uses all of it, copy the
 	 * data to a new buffer and make room for storing the backpointer.
 	 */
-	if (PTR_IS_ALIGNED(xdpf->data, DPAA_A050385_ALIGN) &&
+	if (PTR_IS_ALIGNED(xdpf->data, DPAA_FD_DATA_ALIGNMENT) &&
 	    xdpf->headroom >= priv->tx_headroom) {
 		xdpf->headroom = priv->tx_headroom;
 		return 0;
-- 
2.17.1