From 63ae7949e94aad607c24d00b8ce3f5661c0a1e9d Mon Sep 17 00:00:00 2001 From: Ilias Apalodimas Date: Fri, 10 Aug 2018 09:12:38 +0300 Subject: [PATCH] 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 Signed-off-by: David S. Miller --- drivers/net/ethernet/socionext/netsec.c | 25 ++++++++++--------------- 1 file changed, 10 insertions(+), 15 deletions(-) diff --git a/drivers/net/ethernet/socionext/netsec.c b/drivers/net/ethernet/socionext/netsec.c index 01589b6982e4..334b6189b011 100644 --- a/drivers/net/ethernet/socionext/netsec.c +++ b/drivers/net/ethernet/socionext/netsec.c @@ -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,