net: ethernet: mtk_eth_soc: rely on rxd_size field in mtk_rx_alloc/mtk_rx_clean

Remove mtk_rx_dma structure layout dependency in mtk_rx_alloc/mtk_rx_clean.
Initialize to 0 rxd3 and rxd4 in mtk_rx_alloc.
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

@@ -1749,18 +1749,25 @@ static int mtk_rx_alloc(struct mtk_eth *eth, int ring_no, int rx_flag)
 		return -ENOMEM;
 
 	for (i = 0; i < rx_dma_size; i++) {
+		struct mtk_rx_dma *rxd;
+
 		dma_addr_t dma_addr = dma_map_single(eth->dma_dev,
 				ring->data[i] + NET_SKB_PAD + eth->ip_align,
 				ring->buf_size,
 				DMA_FROM_DEVICE);
 		if (unlikely(dma_mapping_error(eth->dma_dev, dma_addr)))
 			return -ENOMEM;
-		ring->dma[i].rxd1 = (unsigned int)dma_addr;
+
+		rxd = (void *)ring->dma + i * eth->soc->txrx.rxd_size;
+		rxd->rxd1 = (unsigned int)dma_addr;
 
 		if (MTK_HAS_CAPS(eth->soc->caps, MTK_SOC_MT7628))
-			ring->dma[i].rxd2 = RX_DMA_LSO;
+			rxd->rxd2 = RX_DMA_LSO;
 		else
-			ring->dma[i].rxd2 = RX_DMA_PLEN0(ring->buf_size);
+			rxd->rxd2 = RX_DMA_PLEN0(ring->buf_size);
+
+		rxd->rxd3 = 0;
+		rxd->rxd4 = 0;
 	}
 	ring->dma_size = rx_dma_size;
 	ring->calc_idx_update = false;
@@ -1785,14 +1792,17 @@ static void mtk_rx_clean(struct mtk_eth *eth, struct mtk_rx_ring *ring)
 
 	if (ring->data && ring->dma) {
 		for (i = 0; i < ring->dma_size; i++) {
+			struct mtk_rx_dma *rxd;
+
 			if (!ring->data[i])
 				continue;
-			if (!ring->dma[i].rxd1)
+
+			rxd = (void *)ring->dma + i * eth->soc->txrx.rxd_size;
+			if (!rxd->rxd1)
 				continue;
-			dma_unmap_single(eth->dma_dev,
-					 ring->dma[i].rxd1,
-					 ring->buf_size,
-					 DMA_FROM_DEVICE);
+
+			dma_unmap_single(eth->dma_dev, rxd->rxd1,
+					 ring->buf_size, DMA_FROM_DEVICE);
 			skb_free_frag(ring->data[i]);
 		}
 		kfree(ring->data);