Commit 63ae7949 authored by Ilias Apalodimas's avatar Ilias Apalodimas Committed by David S. Miller
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net: socionext: Use descriptor info instead of MMIO reads on Rx 



MMIO reads for remaining packets in queue occur (at least)twice per
invocation of netsec_process_rx(). We can use the packet descriptor to
identify if it's owned by the hardware and break out, avoiding the more
expensive MMIO read operations. This has a ~2% increase on the pps of the
Rx path when tested with 64byte packets

Signed-off-by: default avatarIlias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 78aca3bb

drivers/net/ethernet/socionext/netsec.c

+10 −15
Original line number Diff line number Diff line
@@ -642,8 +642,6 @@ static struct sk_buff *netsec_get_rx_pkt_data(struct netsec_priv *priv, 


	tmp_skb = netsec_alloc_skb(priv, &td);



	dma_rmb();



	tail = dring->tail;



	if (!tmp_skb) {
@@ -657,8 +655,6 @@ static struct sk_buff *netsec_get_rx_pkt_data(struct netsec_priv *priv, 
	/* move tail ahead */

	dring->tail = (dring->tail + 1) % DESC_NUM;



	dring->pkt_cnt--;



	return skb;

}
@@ -731,25 +727,24 @@ static int netsec_process_rx(struct netsec_priv *priv, int budget) 
	struct netsec_desc_ring *dring = &priv->desc_ring[NETSEC_RING_RX];

	struct net_device *ndev = priv->ndev;

	struct netsec_rx_pkt_info rx_info;

	int done = 0, rx_num = 0;

	int done = 0;

	struct netsec_desc desc;

	struct sk_buff *skb;

	u16 len;



	while (done < budget) {

		if (!rx_num) {

			rx_num = netsec_read(priv, NETSEC_REG_NRM_RX_PKTCNT);

			dring->pkt_cnt += rx_num;



			/* move head 'rx_num' */

			dring->head = (dring->head + rx_num) % DESC_NUM;

		u16 idx = dring->tail;

		struct netsec_de *de = dring->vaddr + (DESC_SZ * idx);



			rx_num = dring->pkt_cnt;

			if (!rx_num)

		if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD))

			break;

		}



		/* This  barrier is needed to keep us from reading

		 * any other fields out of the netsec_de until we have

		 * verified the descriptor has been written back

		 */

		dma_rmb();

		done++;

		rx_num--;

		skb = netsec_get_rx_pkt_data(priv, &rx_info, &desc, &len);

		if (unlikely(!skb) || rx_info.err_flag) {

			netif_err(priv, drv, priv->ndev,

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