netdev - [net-next RFC v3 4/7] net: ravb: Refactor GbEth RX code path

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Message-Id: <20240415094804.8016-5-paul.barker.ct@bp.renesas.com>
Date: Mon, 15 Apr 2024 10:48:01 +0100
From: Paul Barker <paul.barker.ct@...renesas.com>
To: Sergey Shtylyov <s.shtylyov@....ru>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>
Cc: Paul Barker <paul.barker.ct@...renesas.com>,
	Niklas Söderlund <niklas.soderlund+renesas@...natech.se>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	netdev@...r.kernel.org,
	linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [net-next RFC v3 4/7] net: ravb: Refactor GbEth RX code path

We can reduce code duplication in ravb_rx_gbeth() and add comments to
make the code flow easier to understand.

Signed-off-by: Paul Barker <paul.barker.ct@...renesas.com>
---
 drivers/net/ethernet/renesas/ravb_main.c | 70 ++++++++++++------------
 1 file changed, 35 insertions(+), 35 deletions(-)

diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
index baa01bd81f2d..12618171f6d5 100644
--- a/drivers/net/ethernet/renesas/ravb_main.c
+++ b/drivers/net/ethernet/renesas/ravb_main.c
@@ -818,47 +818,47 @@ static int ravb_rx_gbeth(struct net_device *ndev, int budget, int q)
 				stats->rx_missed_errors++;
 		} else {
 			die_dt = desc->die_dt & 0xF0;
-			switch (die_dt) {
-			case DT_FSINGLE:
-				skb = ravb_get_skb_gbeth(ndev, entry, desc);
+			skb = ravb_get_skb_gbeth(ndev, entry, desc);
+			if (die_dt == DT_FSINGLE || die_dt == DT_FSTART) {
+				/* Start of packet:
+				 * Set initial data length.
+				 */
 				skb_put(skb, desc_len);
+
+				/* Save this SKB if the packet spans multiple
+				 * descriptors.
+				 */
+				if (die_dt == DT_FSTART)
+					priv->rx_1st_skb = skb;
+			} else {
+				/* Continuing a packet:
+				 * Move data into the saved SKB.
+				 */
+				skb_copy_to_linear_data_offset(priv->rx_1st_skb,
+							       priv->rx_1st_skb->len,
+							       skb->data,
+							       desc_len);
+				skb_put(priv->rx_1st_skb, desc_len);
+				dev_kfree_skb(skb);
+
+				/* Set skb to point at the whole packet so that
+				 * we only need one code path for finishing a
+				 * packet.
+				 */
+				skb = priv->rx_1st_skb;
+			}
+
+			if (die_dt == DT_FSINGLE || die_dt == DT_FEND) {
+				/* Finishing a packet:
+				 * Determine protocol & checksum, hand off to
+				 * NAPI and update our stats.
+				 */
 				skb->protocol = eth_type_trans(skb, ndev);
 				if (ndev->features & NETIF_F_RXCSUM)
 					ravb_rx_csum_gbeth(skb);
+				stats->rx_bytes += skb->len;
 				napi_gro_receive(&priv->napi[q], skb);
 				rx_packets++;
-				stats->rx_bytes += desc_len;
-				break;
-			case DT_FSTART:
-				priv->rx_1st_skb = ravb_get_skb_gbeth(ndev, entry, desc);
-				skb_put(priv->rx_1st_skb, desc_len);
-				break;
-			case DT_FMID:
-				skb = ravb_get_skb_gbeth(ndev, entry, desc);
-				skb_copy_to_linear_data_offset(priv->rx_1st_skb,
-							       priv->rx_1st_skb->len,
-							       skb->data,
-							       desc_len);
-				skb_put(priv->rx_1st_skb, desc_len);
-				dev_kfree_skb(skb);
-				break;
-			case DT_FEND:
-				skb = ravb_get_skb_gbeth(ndev, entry, desc);
-				skb_copy_to_linear_data_offset(priv->rx_1st_skb,
-							       priv->rx_1st_skb->len,
-							       skb->data,
-							       desc_len);
-				skb_put(priv->rx_1st_skb, desc_len);
-				dev_kfree_skb(skb);
-				priv->rx_1st_skb->protocol =
-					eth_type_trans(priv->rx_1st_skb, ndev);
-				if (ndev->features & NETIF_F_RXCSUM)
-					ravb_rx_csum_gbeth(priv->rx_1st_skb);
-				stats->rx_bytes += priv->rx_1st_skb->len;
-				napi_gro_receive(&priv->napi[q],
-						 priv->rx_1st_skb);
-				rx_packets++;
-				break;
 			}
 		}
 	}
-- 
2.39.2