netdev - [PATCH net] net: fec: avoid tx queue timeout when XDP is enabled

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Date: Fri, 21 Jul 2023 16:35:59 +0800
From: Wei Fang <wei.fang@....com>
To: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	shenwei.wang@....com,
	xiaoning.wang@....com,
	netdev@...r.kernel.org
Cc: linux-imx@....com,
	linux-kernel@...r.kernel.org
Subject: [PATCH net] net: fec: avoid tx queue timeout when XDP is enabled

According to the implementation of XDP of FEC driver, the XDP path
shares the transmit queues with the kernel network stack, so it is
possible to lead to a tx timeout event when XDP uses the tx queue
pretty much exclusively. And this event will cause the reset of the
FEC hardware.
To avoid timeout in this case, we use the txq_trans_cond_update()
interface to update txq->trans_start to jiffies so that watchdog
won't generate a transmit timeout warning.

Fixes: 6d6b39f180b8 ("net: fec: add initial XDP support")
Signed-off-by: Wei Fang <wei.fang@....com>
---
 drivers/net/ethernet/freescale/fec_main.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index ec9e4bdb0c06..073d61619336 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -3916,6 +3916,8 @@ static int fec_enet_xdp_xmit(struct net_device *dev,
 
 	__netif_tx_lock(nq, cpu);
 
+	/* Avoid tx timeout as XDP shares the queue with kernel stack */
+	txq_trans_cond_update(nq);
 	for (i = 0; i < num_frames; i++) {
 		if (fec_enet_txq_xmit_frame(fep, txq, frames[i]) < 0)
 			break;
-- 
2.25.1