net: airoha: Add missing bits in airoha_qdma_cleanup_tx_queue()

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: 23020f0 ("net: airoha: Introduce ethernet support for EN7581 SoC")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260417-airoha_qdma_cleanup_tx_queue-fix-net-v4-2-e04bcc2c9642@kernel.org
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Author: LorenzoBianconi

drivers/net/ethernet/airoha/airoha_eth.c

@@ -1063,12 +1063,15 @@ 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];
+	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];
 
 		if (!e->dma_addr)
 			continue;
@@ -1079,8 +1082,33 @@ 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)) {
+		struct airoha_queue_entry *e;
+
+		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);
 }