net: rswitch: Add jumbo frames handling for RX

If this hardware receives a jumbo frame like 2KiB or more, it will be
split into multiple queues. In the near future, to support this,
add handling specific descriptor types F{START,MID,END}. However, such
jumbo frames will not happen yet because the maximum MTU size is still
default for now.
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/rswitch.c

@@ -714,6 +714,80 @@ static int rswitch_gwca_halt(struct rswitch_private *priv)
 	return err;
 }
 
+static struct sk_buff *rswitch_rx_handle_desc(struct net_device *ndev,
+					      struct rswitch_gwca_queue *gq,
+					      struct rswitch_ext_ts_desc *desc)
+{
+	dma_addr_t dma_addr = rswitch_desc_get_dptr(&desc->desc);
+	u16 pkt_len = le16_to_cpu(desc->desc.info_ds) & RX_DS;
+	u8 die_dt = desc->desc.die_dt & DT_MASK;
+	struct sk_buff *skb = NULL;
+
+	dma_unmap_single(ndev->dev.parent, dma_addr, RSWITCH_MAP_BUF_SIZE,
+			 DMA_FROM_DEVICE);
+
+	/* The RX descriptor order will be one of the following:
+	 * - FSINGLE
+	 * - FSTART -> FEND
+	 * - FSTART -> FMID -> FEND
+	 */
+
+	/* Check whether the descriptor is unexpected order */
+	switch (die_dt) {
+	case DT_FSTART:
+	case DT_FSINGLE:
+		if (gq->skb_fstart) {
+			dev_kfree_skb_any(gq->skb_fstart);
+			gq->skb_fstart = NULL;
+			ndev->stats.rx_dropped++;
+		}
+		break;
+	case DT_FMID:
+	case DT_FEND:
+		if (!gq->skb_fstart) {
+			ndev->stats.rx_dropped++;
+			return NULL;
+		}
+		break;
+	default:
+		break;
+	}
+
+	/* Handle the descriptor */
+	switch (die_dt) {
+	case DT_FSTART:
+	case DT_FSINGLE:
+		skb = build_skb(gq->rx_bufs[gq->cur], RSWITCH_BUF_SIZE);
+		if (skb) {
+			skb_reserve(skb, RSWITCH_HEADROOM);
+			skb_put(skb, pkt_len);
+			gq->pkt_len = pkt_len;
+			if (die_dt == DT_FSTART) {
+				gq->skb_fstart = skb;
+				skb = NULL;
+			}
+		}
+		break;
+	case DT_FMID:
+	case DT_FEND:
+		skb_add_rx_frag(gq->skb_fstart, skb_shinfo(gq->skb_fstart)->nr_frags,
+				virt_to_page(gq->rx_bufs[gq->cur]),
+				offset_in_page(gq->rx_bufs[gq->cur]) + RSWITCH_HEADROOM,
+				pkt_len, RSWITCH_BUF_SIZE);
+		if (die_dt == DT_FEND) {
+			skb = gq->skb_fstart;
+			gq->skb_fstart = NULL;
+		}
+		gq->pkt_len += pkt_len;
+		break;
+	default:
+		netdev_err(ndev, "%s: unexpected value (%x)\n", __func__, die_dt);
+		break;
+	}
+
+	return skb;
+}
+
 static bool rswitch_rx(struct net_device *ndev, int *quota)
 {
 	struct rswitch_device *rdev = netdev_priv(ndev);
@@ -721,9 +795,7 @@ static bool rswitch_rx(struct net_device *ndev, int *quota)
 	struct rswitch_ext_ts_desc *desc;
 	int limit, boguscnt, ret;
 	struct sk_buff *skb;
-	dma_addr_t dma_addr;
 	unsigned int num;
-	u16 pkt_len;
 	u32 get_ts;
 
 	if (*quota <= 0)
@@ -735,15 +807,9 @@ static bool rswitch_rx(struct net_device *ndev, int *quota)
 	desc = &gq->rx_ring[gq->cur];
 	while ((desc->desc.die_dt & DT_MASK) != DT_FEMPTY) {
 		dma_rmb();
-		pkt_len = le16_to_cpu(desc->desc.info_ds) & RX_DS;
-		dma_addr = rswitch_desc_get_dptr(&desc->desc);
-		dma_unmap_single(ndev->dev.parent, dma_addr,
-				 RSWITCH_MAP_BUF_SIZE, DMA_FROM_DEVICE);
-		skb = build_skb(gq->rx_bufs[gq->cur], RSWITCH_BUF_SIZE);
+		skb = rswitch_rx_handle_desc(ndev, gq, desc);
 		if (!skb)
 			goto out;
-		skb_reserve(skb, RSWITCH_HEADROOM);
-		skb_put(skb, pkt_len);
 
 		get_ts = rdev->priv->ptp_priv->tstamp_rx_ctrl & RCAR_GEN4_RXTSTAMP_TYPE_V2_L2_EVENT;
 		if (get_ts) {
@@ -759,7 +825,7 @@ static bool rswitch_rx(struct net_device *ndev, int *quota)
 		skb->protocol = eth_type_trans(skb, ndev);
 		napi_gro_receive(&rdev->napi, skb);
 		rdev->ndev->stats.rx_packets++;
-		rdev->ndev->stats.rx_bytes += pkt_len;
+		rdev->ndev->stats.rx_bytes += gq->pkt_len;
 
 out:
 		gq->rx_bufs[gq->cur] = NULL;

drivers/net/ethernet/renesas/rswitch.h

@@ -965,6 +965,8 @@ struct rswitch_gwca_queue {
 		/* For RX */
 		struct {
 			void **rx_bufs;
+			struct sk_buff *skb_fstart;
+			u16 pkt_len;
 		};
 	};
 };