[PATCH net v2] net: airoha: Add missing bits in airoha_qdma_cleanup_tx_queue()

[Lorenzo Bianconi]

Similar to airoha_qdma_cleanup_rx_queue(), reset DMA TX descriptors in
airoha_qdma_cleanup_tx_queue routine. Moreover, reset TX_DMA_IDX to
TX_CPU_IDX to notify the NIC the QDMA TX ring is empty.

Fixes: 23020f0493270 ("net: airoha: Introduce ethernet support for EN7581 SoC")
Signed-off-by: Lorenzo Bianconi <lorenzo at kernel.org>
---
Changes in v2:
- Move q->ndesc initialization at end of airoha_qdma_init_tx routine in
  order to avoid any possible NULL pointer dereference in
  airoha_qdma_cleanup_tx_queue()
- Check if q->tx_list is empty in airoha_qdma_cleanup_tx_queue()
- Link to v1: https://lore.kernel.org/r/20260410-airoha_qdma_cleanup_tx_queue-fix-net-v1-1-b7171c8f1e78@kernel.org
---
 drivers/net/ethernet/airoha/airoha_eth.c | 41 ++++++++++++++++++++++++++------
 1 file changed, 34 insertions(+), 7 deletions(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 9e995094c32a..3c1a2bc68c42 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -966,27 +966,27 @@ static int airoha_qdma_init_tx_queue(struct airoha_queue *q,
 	dma_addr_t dma_addr;
 
 	spin_lock_init(&q->lock);
-	q->ndesc = size;
 	q->qdma = qdma;
 	q->free_thr = 1 + MAX_SKB_FRAGS;
 	INIT_LIST_HEAD(&q->tx_list);
 
-	q->entry = devm_kzalloc(eth->dev, q->ndesc * sizeof(*q->entry),
+	q->entry = devm_kzalloc(eth->dev, size * sizeof(*q->entry),
 				GFP_KERNEL);
 	if (!q->entry)
 		return -ENOMEM;
 
-	q->desc = dmam_alloc_coherent(eth->dev, q->ndesc * sizeof(*q->desc),
+	q->desc = dmam_alloc_coherent(eth->dev, size * sizeof(*q->desc),
 				      &dma_addr, GFP_KERNEL);
 	if (!q->desc)
 		return -ENOMEM;
 
-	for (i = 0; i < q->ndesc; i++) {
+	for (i = 0; i < size; i++) {
 		u32 val = FIELD_PREP(QDMA_DESC_DONE_MASK, 1);
 
 		list_add_tail(&q->entry[i].list, &q->tx_list);
 		WRITE_ONCE(q->desc[i].ctrl, cpu_to_le32(val));
 	}
+	q->ndesc = size;
 
 	/* xmit ring drop default setting */
 	airoha_qdma_set(qdma, REG_TX_RING_BLOCKING(qid),
@@ -1051,13 +1051,17 @@ static int airoha_qdma_init_tx(struct airoha_qdma *qdma)
 
 static void airoha_qdma_cleanup_tx_queue(struct airoha_queue *q)
 {
-	struct airoha_eth *eth = q->qdma->eth;
-	int i;
+	struct airoha_qdma *qdma = q->qdma;
+	struct airoha_eth *eth = qdma->eth;
+	int i, qid = q - &qdma->q_tx[0];
+	struct airoha_queue_entry *e;
+	u16 index = 0;
 
 	spin_lock_bh(&q->lock);
 	for (i = 0; i < q->ndesc; i++) {
-		struct airoha_queue_entry *e = &q->entry[i];
+		struct airoha_qdma_desc *desc = &q->desc[i];
 
+		e = &q->entry[i];
 		if (!e->dma_addr)
 			continue;
 
@@ -1067,8 +1071,31 @@ static void airoha_qdma_cleanup_tx_queue(struct airoha_queue *q)
 		e->dma_addr = 0;
 		e->skb = NULL;
 		list_add_tail(&e->list, &q->tx_list);
+
+		/* Reset DMA descriptor */
+		WRITE_ONCE(desc->ctrl, 0);
+		WRITE_ONCE(desc->addr, 0);
+		WRITE_ONCE(desc->data, 0);
+		WRITE_ONCE(desc->msg0, 0);
+		WRITE_ONCE(desc->msg1, 0);
+		WRITE_ONCE(desc->msg2, 0);
+
 		q->queued--;
 	}
+
+	if (!list_empty(&q->tx_list)) {
+		e = list_first_entry(&q->tx_list, struct airoha_queue_entry,
+				     list);
+		index = e - q->entry;
+	}
+	/* Set TX_DMA_IDX to TX_CPU_IDX to notify the hw the QDMA TX ring is
+	 * empty.
+	 */
+	airoha_qdma_rmw(qdma, REG_TX_CPU_IDX(qid), TX_RING_CPU_IDX_MASK,
+			FIELD_PREP(TX_RING_CPU_IDX_MASK, index));
+	airoha_qdma_rmw(qdma, REG_TX_DMA_IDX(qid), TX_RING_DMA_IDX_MASK,
+			FIELD_PREP(TX_RING_DMA_IDX_MASK, index));
+
 	spin_unlock_bh(&q->lock);
 }
 

---
base-commit: 2cd7e6971fc2787408ceef17906ea152791448cf
change-id: 20260410-airoha_qdma_cleanup_tx_queue-fix-net-93375f5ee80f

Best regards,
-- 
Lorenzo Bianconi <lorenzo at kernel.org>