sh_eth: Optimization for RX excess judgement

Both of 'boguscnt' and 'quota' have nearly meaning as the condition of
the reception loop.
In order to cut down redundant processing, this patch changes excess
judgement.

Signed-off-by: Mitsuhiro Kimura <mitsuhiro.kimura.kc@renesas.com>
Signed-off-by: Yoshihiro Kaneko <ykaneko0929@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/sh_eth.c

@@ -1395,10 +1395,13 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota)
 
 	int entry = mdp->cur_rx % mdp->num_rx_ring;
 	int boguscnt = (mdp->dirty_rx + mdp->num_rx_ring) - mdp->cur_rx;
+	int limit;
 	struct sk_buff *skb;
 	u16 pkt_len = 0;
 	u32 desc_status;
 
+	boguscnt = min(boguscnt, *quota);
+	limit = boguscnt;
 	rxdesc = &mdp->rx_ring[entry];
 	while (!(rxdesc->status & cpu_to_edmac(mdp, RD_RACT))) {
 		desc_status = edmac_to_cpu(mdp, rxdesc->status);
@@ -1407,11 +1410,6 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota)
 		if (--boguscnt < 0)
 			break;
 
-		if (*quota <= 0)
-			break;
-
-		(*quota)--;
-
 		if (!(desc_status & RDFEND))
 			ndev->stats.rx_length_errors++;
 
@@ -1502,6 +1500,8 @@ static int sh_eth_rx(struct net_device *ndev, u32 intr_status, int *quota)
 		sh_eth_write(ndev, EDRRR_R, EDRRR);
 	}
 
+	*quota -= limit - boguscnt - 1;
+
 	return *quota <= 0;
 }