Commit b94769eb authored by Lorenzo Bianconi's avatar Lorenzo Bianconi Committed by Jakub Kicinski
Browse files

net: airoha: Fix possible TX queue stall in airoha_qdma_tx_napi_poll() 



Since multiple net_device TX queues can share the same hw QDMA TX queue,
there is no guarantee we have inflight packets queued in hw belonging to a
net_device TX queue stopped in the xmit path because hw QDMA TX queue
can be full. In this corner case the net_device TX queue will never be
re-activated. In order to avoid any potential net_device TX queue stall,
we need to wake all the net_device TX queues feeding the same hw QDMA TX
queue in airoha_qdma_tx_napi_poll routine.

Fixes: 23020f04 ("net: airoha: Introduce ethernet support for EN7581 SoC")
Signed-off-by: default avatarLorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: default avatarSimon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20260416-airoha-txq-potential-stall-v2-1-42c732074540@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 2091c6aa

drivers/net/ethernet/airoha/airoha_eth.c

+32 −5
Original line number Diff line number Diff line
@@ -843,6 +843,21 @@ static int airoha_qdma_init_rx(struct airoha_qdma *qdma) 
	return 0;

}



static void airoha_qdma_wake_netdev_txqs(struct airoha_queue *q)

{

	struct airoha_qdma *qdma = q->qdma;

	struct airoha_eth *eth = qdma->eth;

	int i;



	for (i = 0; i < ARRAY_SIZE(eth->ports); i++) {

		struct airoha_gdm_port *port = eth->ports[i];



		if (port && port->qdma == qdma)

			netif_tx_wake_all_queues(port->dev);

	}

	q->txq_stopped = false;

}



static int airoha_qdma_tx_napi_poll(struct napi_struct *napi, int budget)

{

	struct airoha_tx_irq_queue *irq_q;
@@ -919,12 +934,21 @@ static int airoha_qdma_tx_napi_poll(struct napi_struct *napi, int budget) 


			txq = netdev_get_tx_queue(skb->dev, queue);

			netdev_tx_completed_queue(txq, 1, skb->len);

			if (netif_tx_queue_stopped(txq) &&

			    q->ndesc - q->queued >= q->free_thr)

				netif_tx_wake_queue(txq);



			dev_kfree_skb_any(skb);

		}



		if (q->txq_stopped && q->ndesc - q->queued >= q->free_thr) {

			/* Since multiple net_device TX queues can share the

			 * same hw QDMA TX queue, there is no guarantee we have

			 * inflight packets queued in hw belonging to a

			 * net_device TX queue stopped in the xmit path.

			 * In order to avoid any potential net_device TX queue

			 * stall, we need to wake all the net_device TX queues

			 * feeding the same hw QDMA TX queue.

			 */

			airoha_qdma_wake_netdev_txqs(q);

		}



unlock:

		spin_unlock_bh(&q->lock);

	}
@@ -1984,6 +2008,7 @@ static netdev_tx_t airoha_dev_xmit(struct sk_buff *skb, 
	if (q->queued + nr_frags >= q->ndesc) {

		/* not enough space in the queue */

		netif_tx_stop_queue(txq);

		q->txq_stopped = true;

		spin_unlock_bh(&q->lock);

		return NETDEV_TX_BUSY;

	}
@@ -2039,8 +2064,10 @@ static netdev_tx_t airoha_dev_xmit(struct sk_buff *skb, 
				TX_RING_CPU_IDX_MASK,

				FIELD_PREP(TX_RING_CPU_IDX_MASK, index));



	if (q->ndesc - q->queued < q->free_thr)

	if (q->ndesc - q->queued < q->free_thr) {

		netif_tx_stop_queue(txq);

		q->txq_stopped = true;

	}



	spin_unlock_bh(&q->lock);

drivers/net/ethernet/airoha/airoha_eth.h

+1 −0
Original line number Diff line number Diff line
@@ -193,6 +193,7 @@ struct airoha_queue { 
	int ndesc;

	int free_thr;

	int buf_size;

	bool txq_stopped;



	struct napi_struct napi;

	struct page_pool *page_pool;