r8169: improve rtl_rx

This patch improves few aspects of rtl_rx, no functional change intended.

1. inline rtl8169_try_rx_copy
2. make pkt_size unsigned
3. use constant ETH_FCS_LEN instead of value 4
4. We just created the skb, so we don't need the checks in skb_put.
   Also we don't need the return value of skb_put.
   Set skb->tail and skb->len directly.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/realtek/r8169_main.c

@@ -5908,23 +5908,6 @@ static inline void rtl8169_rx_csum(struct sk_buff *skb, u32 opts1)
 		skb_checksum_none_assert(skb);
 }
 
-static struct sk_buff *rtl8169_try_rx_copy(void *data,
-					   struct rtl8169_private *tp,
-					   int pkt_size,
-					   dma_addr_t addr)
-{
-	struct sk_buff *skb;
-	struct device *d = tp_to_dev(tp);
-
-	dma_sync_single_for_cpu(d, addr, pkt_size, DMA_FROM_DEVICE);
-	prefetch(data);
-	skb = napi_alloc_skb(&tp->napi, pkt_size);
-	if (skb)
-		skb_copy_to_linear_data(skb, data, pkt_size);
-
-	return skb;
-}
-
 static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, u32 budget)
 {
 	unsigned int cur_rx, rx_left;
@@ -5960,17 +5943,13 @@ static int rtl_rx(struct net_device *dev, struct rtl8169_private *tp, u32 budget
 				goto process_pkt;
 			}
 		} else {
+			unsigned int pkt_size;
 			struct sk_buff *skb;
-			dma_addr_t addr;
-			int pkt_size;
 
 process_pkt:
-			addr = le64_to_cpu(desc->addr);
+			pkt_size = status & GENMASK(13, 0);
 			if (likely(!(dev->features & NETIF_F_RXFCS)))
-				pkt_size = (status & 0x00003fff) - 4;
-			else
-				pkt_size = status & 0x00003fff;
-
+				pkt_size -= ETH_FCS_LEN;
 			/*
 			 * The driver does not support incoming fragmented
 			 * frames. They are seen as a symptom of over-mtu
@@ -5982,15 +5961,23 @@ process_pkt:
 				goto release_descriptor;
 			}
 
-			skb = rtl8169_try_rx_copy(tp->Rx_databuff[entry],
-						  tp, pkt_size, addr);
-			if (!skb) {
+			dma_sync_single_for_cpu(tp_to_dev(tp),
+						le64_to_cpu(desc->addr),
+						pkt_size, DMA_FROM_DEVICE);
+
+			skb = napi_alloc_skb(&tp->napi, pkt_size);
+			if (unlikely(!skb)) {
 				dev->stats.rx_dropped++;
 				goto release_descriptor;
 			}
 
+			prefetch(tp->Rx_databuff[entry]);
+			skb_copy_to_linear_data(skb, tp->Rx_databuff[entry],
+						pkt_size);
+			skb->tail += pkt_size;
+			skb->len = pkt_size;
+
 			rtl8169_rx_csum(skb, status);
-			skb_put(skb, pkt_size);
 			skb->protocol = eth_type_trans(skb, dev);
 
 			rtl8169_rx_vlan_tag(desc, skb);