net: ethernet: mtk_eth_soc: rely on txd_size in txd_to_idx

This is a preliminary patch to add mt7986 ethernet support.
Tested-by: Sam Shih <sam.shih@mediatek.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_eth_soc.c

@@ -876,9 +876,10 @@ static struct mtk_tx_dma *qdma_to_pdma(struct mtk_tx_ring *ring,
 	return ring->dma_pdma - ring->dma + dma;
 }
 
-static int txd_to_idx(struct mtk_tx_ring *ring, struct mtk_tx_dma *dma)
+static int txd_to_idx(struct mtk_tx_ring *ring, struct mtk_tx_dma *dma,
+		      u32 txd_size)
 {
-	return ((void *)dma - (void *)ring->dma) / sizeof(*dma);
+	return ((void *)dma - (void *)ring->dma) / txd_size;
 }
 
 static void mtk_tx_unmap(struct mtk_eth *eth, struct mtk_tx_buf *tx_buf,
@@ -1094,7 +1095,9 @@ static int mtk_tx_map(struct sk_buff *skb, struct net_device *dev,
 		    !netdev_xmit_more())
 			mtk_w32(eth, txd->txd2, MTK_QTX_CTX_PTR);
 	} else {
-		int next_idx = NEXT_DESP_IDX(txd_to_idx(ring, txd),
+		int next_idx;
+
+		next_idx = NEXT_DESP_IDX(txd_to_idx(ring, txd, soc->txrx.txd_size),
 					 ring->dma_size);
 		mtk_w32(eth, next_idx, MT7628_TX_CTX_IDX0);
 	}