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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: Ilias Apalodimas <ilias.apalodimas@linaro.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Ilias Apalodimas 2018-08-10 09:12:38 +03:00 committed by David S. Miller
parent 78aca3bbee
commit 63ae7949e9
1 changed files with 10 additions and 15 deletions
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25
drivers/net/ethernet/socionext/netsec.c
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@ -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;
u16 idx = dring->tail;
struct netsec_de *de = dring->vaddr + (DESC_SZ * idx);
/* move head 'rx_num' */
dring->head = (dring->head + rx_num) % DESC_NUM;
if (de->attr & (1U << NETSEC_RX_PKT_OWN_FIELD))
break;
rx_num = dring->pkt_cnt;
if (!rx_num)
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,