dpaa2-eth: use the S/G table cache also for the normal S/G path

Instead of allocating memory for an S/G table each time a nonlinear skb
is processed, and then freeing it on the Tx confirmation path, use the
S/G table cache in order to reuse the memory.

For this to work we have to change the size of the cached buffers so
that it can hold the maximum number of scatterlist entries.

Other than that, each allocate/free call is replaced by a call to the
dpaa2_eth_sgt_get/dpaa2_eth_sgt_recycle functions, introduced in the
previous patch.
Signed-off-by: Ioana Ciornei <ioana.ciornei@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.c

@@ -767,7 +767,8 @@ static void *dpaa2_eth_sgt_get(struct dpaa2_eth_priv *priv)
 	int sgt_buf_size;
 
 	sgt_cache = this_cpu_ptr(priv->sgt_cache);
-	sgt_buf_size = priv->tx_data_offset + sizeof(struct dpaa2_sg_entry);
+	sgt_buf_size = priv->tx_data_offset +
+		DPAA2_ETH_SG_ENTRIES_MAX * sizeof(struct dpaa2_sg_entry);
 
 	if (sgt_cache->count == 0)
 		sgt_buf = napi_alloc_frag_align(sgt_buf_size, DPAA2_ETH_TX_BUF_ALIGN);
@@ -837,7 +838,7 @@ static int dpaa2_eth_build_sg_fd(struct dpaa2_eth_priv *priv,
 	/* Prepare the HW SGT structure */
 	sgt_buf_size = priv->tx_data_offset +
 		       sizeof(struct dpaa2_sg_entry) *  num_dma_bufs;
-	sgt_buf = napi_alloc_frag_align(sgt_buf_size, DPAA2_ETH_TX_BUF_ALIGN);
+	sgt_buf = dpaa2_eth_sgt_get(priv);
 	if (unlikely(!sgt_buf)) {
 		err = -ENOMEM;
 		goto sgt_buf_alloc_failed;
@@ -886,7 +887,7 @@ static int dpaa2_eth_build_sg_fd(struct dpaa2_eth_priv *priv,
 	return 0;
 
 dma_map_single_failed:
-	skb_free_frag(sgt_buf);
+	dpaa2_eth_sgt_recycle(priv, sgt_buf);
 sgt_buf_alloc_failed:
 	dma_unmap_sg(dev, scl, num_sg, DMA_BIDIRECTIONAL);
 dma_map_sg_failed:
@@ -1099,12 +1100,8 @@ static void dpaa2_eth_free_tx_fd(struct dpaa2_eth_priv *priv,
 	}
 
 	/* Free SGT buffer allocated on tx */
-	if (fd_format != dpaa2_fd_single) {
-		if (swa->type == DPAA2_ETH_SWA_SG)
-			skb_free_frag(buffer_start);
-		else
-			dpaa2_eth_sgt_recycle(priv, buffer_start);
-	}
+	if (fd_format != dpaa2_fd_single)
+		dpaa2_eth_sgt_recycle(priv, buffer_start);
 
 	/* Move on with skb release */
 	napi_consume_skb(skb, in_napi);

drivers/net/ethernet/freescale/dpaa2/dpaa2-eth.h

@@ -493,6 +493,8 @@ struct dpaa2_eth_trap_data {
 	struct dpaa2_eth_priv *priv;
 };
 
+#define DPAA2_ETH_SG_ENTRIES_MAX	(PAGE_SIZE / sizeof(struct scatterlist))
+
 #define DPAA2_ETH_DEFAULT_COPYBREAK	512
 
 /* Driver private data */