net: ethernet: mediatek: fix inconsistency between TXD and the used buffer

Fix inconsistency between the TXD descriptor and the used buffer that
would cause unexpected logic at mtk_tx_unmap() during skb housekeeping.

Signed-off-by: Sean Wang <sean.wang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -613,7 +613,7 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
 	struct mtk_mac *mac = netdev_priv(dev);
 	struct mtk_eth *eth = mac->hw;
 	struct mtk_tx_dma *itxd, *txd;
-	struct mtk_tx_buf *tx_buf;
+	struct mtk_tx_buf *itx_buf, *tx_buf;
 	dma_addr_t mapped_addr;
 	unsigned int nr_frags;
 	int i, n_desc = 1;
@@ -627,8 +627,8 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
 	fport = (mac->id + 1) << TX_DMA_FPORT_SHIFT;
 	txd4 |= fport;
 
-	tx_buf = mtk_desc_to_tx_buf(ring, itxd);
-	memset(tx_buf, 0, sizeof(*tx_buf));
+	itx_buf = mtk_desc_to_tx_buf(ring, itxd);
+	memset(itx_buf, 0, sizeof(*itx_buf));
 
 	if (gso)
 		txd4 |= TX_DMA_TSO;
@@ -647,9 +647,9 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
 		return -ENOMEM;
 
 	WRITE_ONCE(itxd->txd1, mapped_addr);
-	tx_buf->flags |= MTK_TX_FLAGS_SINGLE0;
-	dma_unmap_addr_set(tx_buf, dma_addr0, mapped_addr);
-	dma_unmap_len_set(tx_buf, dma_len0, skb_headlen(skb));
+	itx_buf->flags |= MTK_TX_FLAGS_SINGLE0;
+	dma_unmap_addr_set(itx_buf, dma_addr0, mapped_addr);
+	dma_unmap_len_set(itx_buf, dma_len0, skb_headlen(skb));
 
 	/* TX SG offload */
 	txd = itxd;
@@ -685,10 +685,9 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
 					       last_frag * TX_DMA_LS0));
 			WRITE_ONCE(txd->txd4, fport);
 
-			tx_buf->skb = (struct sk_buff *)MTK_DMA_DUMMY_DESC;
 			tx_buf = mtk_desc_to_tx_buf(ring, txd);
 			memset(tx_buf, 0, sizeof(*tx_buf));
-
+			tx_buf->skb = (struct sk_buff *)MTK_DMA_DUMMY_DESC;
 			tx_buf->flags |= MTK_TX_FLAGS_PAGE0;
 			dma_unmap_addr_set(tx_buf, dma_addr0, mapped_addr);
 			dma_unmap_len_set(tx_buf, dma_len0, frag_map_size);
@@ -698,7 +697,7 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
 	}
 
 	/* store skb to cleanup */
-	tx_buf->skb = skb;
+	itx_buf->skb = skb;
 
 	WRITE_ONCE(itxd->txd4, txd4);
 	WRITE_ONCE(itxd->txd3, (TX_DMA_SWC | TX_DMA_PLEN0(skb_headlen(skb)) |