Merge branch 'net-renesas-rswitch-several-fixes'

Nikita Yushchenko says:

====================
net: renesas: rswitch: several fixes

This series fixes several glitches found in the rswitch driver.

Repost of https://lore.kernel.org/20241206190015.4194153-1-nikita.yoush@cogentembedded.com
====================

Link: https://patch.msgid.link/20241208095004.69468-1-nikita.yoush@cogentembedded.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

drivers/net/ethernet/renesas/rswitch.c

@@ -862,13 +862,10 @@ static void rswitch_tx_free(struct net_device *ndev)
 	struct rswitch_ext_desc *desc;
 	struct sk_buff *skb;
 
-	for (; rswitch_get_num_cur_queues(gq) > 0;
-	     gq->dirty = rswitch_next_queue_index(gq, false, 1)) {
-		desc = &gq->tx_ring[gq->dirty];
-		if ((desc->desc.die_dt & DT_MASK) != DT_FEMPTY)
-			break;
-
+	desc = &gq->tx_ring[gq->dirty];
+	while ((desc->desc.die_dt & DT_MASK) == DT_FEMPTY) {
 		dma_rmb();
+
 		skb = gq->skbs[gq->dirty];
 		if (skb) {
 			rdev->ndev->stats.tx_packets++;
@@ -879,7 +876,10 @@ static void rswitch_tx_free(struct net_device *ndev)
 			dev_kfree_skb_any(gq->skbs[gq->dirty]);
 			gq->skbs[gq->dirty] = NULL;
 		}
+
 		desc->desc.die_dt = DT_EEMPTY;
+		gq->dirty = rswitch_next_queue_index(gq, false, 1);
+		desc = &gq->tx_ring[gq->dirty];
 	}
 }
 
@@ -1681,8 +1681,11 @@ static netdev_tx_t rswitch_start_xmit(struct sk_buff *skb, struct net_device *nd
 	if (dma_mapping_error(ndev->dev.parent, dma_addr_orig))
 		goto err_kfree;
 
-	gq->skbs[gq->cur] = skb;
-	gq->unmap_addrs[gq->cur] = dma_addr_orig;
+	/* Stored the skb at the last descriptor to avoid skb free before hardware completes send */
+	gq->skbs[(gq->cur + nr_desc - 1) % gq->ring_size] = skb;
+	gq->unmap_addrs[(gq->cur + nr_desc - 1) % gq->ring_size] = dma_addr_orig;
+
+	dma_wmb();
 
 	/* DT_FSTART should be set at last. So, this is reverse order. */
 	for (i = nr_desc; i-- > 0; ) {
@@ -1694,14 +1697,13 @@ static netdev_tx_t rswitch_start_xmit(struct sk_buff *skb, struct net_device *nd
 			goto err_unmap;
 	}
 
-	wmb();	/* gq->cur must be incremented after die_dt was set */
-
 	gq->cur = rswitch_next_queue_index(gq, true, nr_desc);
 	rswitch_modify(rdev->addr, GWTRC(gq->index), 0, BIT(gq->index % 32));
 
 	return ret;
 
 err_unmap:
+	gq->skbs[(gq->cur + nr_desc - 1) % gq->ring_size] = NULL;
 	dma_unmap_single(ndev->dev.parent, dma_addr_orig, skb->len, DMA_TO_DEVICE);
 
 err_kfree:
@@ -1889,7 +1891,6 @@ static int rswitch_device_alloc(struct rswitch_private *priv, unsigned int index
 	rdev->np_port = rswitch_get_port_node(rdev);
 	rdev->disabled = !rdev->np_port;
 	err = of_get_ethdev_address(rdev->np_port, ndev);
-	of_node_put(rdev->np_port);
 	if (err) {
 		if (is_valid_ether_addr(rdev->etha->mac_addr))
 			eth_hw_addr_set(ndev, rdev->etha->mac_addr);
@@ -1919,6 +1920,7 @@ static int rswitch_device_alloc(struct rswitch_private *priv, unsigned int index
 
 out_rxdmac:
 out_get_params:
+	of_node_put(rdev->np_port);
 	netif_napi_del(&rdev->napi);
 	free_netdev(ndev);
 
@@ -1932,6 +1934,7 @@ static void rswitch_device_free(struct rswitch_private *priv, unsigned int index
 
 	rswitch_txdmac_free(ndev);
 	rswitch_rxdmac_free(ndev);
+	of_node_put(rdev->np_port);
 	netif_napi_del(&rdev->napi);
 	free_netdev(ndev);
 }