netdev - [PATCH net-next v2 3/3] net: stmmac: generate software timestamp just before the doorbell

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Message-Id: <20250510134812.48199-4-kerneljasonxing@gmail.com>
Date: Sat, 10 May 2025 21:48:12 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: tariqt@...dia.com,
	andrew+netdev@...n.ch,
	davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	willemdebruijn.kernel@...il.com,
	irusskikh@...vell.com,
	bharat@...lsio.com,
	ayush.sawal@...lsio.com,
	mcoquelin.stm32@...il.com,
	alexandre.torgue@...s.st.com
Cc: linux-arm-kernel@...ts.infradead.org,
	netdev@...r.kernel.org,
	Jason Xing <kernelxing@...cent.com>
Subject: [PATCH net-next v2 3/3] net: stmmac: generate software timestamp just before the doorbell

From: Jason Xing <kernelxing@...cent.com>

Make sure the call of skb_tx_timestamp is as close as possbile to the
doorbell.

The patch also adjusts the order of setting SKBTX_IN_PROGRESS and
generate software timestamp so that without SOF_TIMESTAMPING_OPT_TX_SWHW
being set the software and hardware timestamps will not appear in the
error queue of socket nearly at the same time (Please see __skb_tstamp_tx()).

Signed-off-by: Jason Xing <kernelxing@...cent.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 28b62bd73e23..4446599ba6ee 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4497,8 +4497,6 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (priv->sarc_type)
 		stmmac_set_desc_sarc(priv, first, priv->sarc_type);
 
-	skb_tx_timestamp(skb);
-
 	if (unlikely((skb_shinfo(skb)->tx_flags & SKBTX_HW_TSTAMP) &&
 		     priv->hwts_tx_en)) {
 		/* declare that device is doing timestamping */
@@ -4531,6 +4529,7 @@ static netdev_tx_t stmmac_tso_xmit(struct sk_buff *skb, struct net_device *dev)
 	}
 
 	netdev_tx_sent_queue(netdev_get_tx_queue(dev, queue), skb->len);
+	skb_tx_timestamp(skb);
 
 	stmmac_flush_tx_descriptors(priv, queue);
 	stmmac_tx_timer_arm(priv, queue);
@@ -4774,8 +4773,6 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (priv->sarc_type)
 		stmmac_set_desc_sarc(priv, first, priv->sarc_type);
 
-	skb_tx_timestamp(skb);
-
 	/* Ready to fill the first descriptor and set the OWN bit w/o any
 	 * problems because all the descriptors are actually ready to be
 	 * passed to the DMA engine.
@@ -4822,7 +4819,7 @@ static netdev_tx_t stmmac_xmit(struct sk_buff *skb, struct net_device *dev)
 	netdev_tx_sent_queue(netdev_get_tx_queue(dev, queue), skb->len);
 
 	stmmac_enable_dma_transmission(priv, priv->ioaddr, queue);
-
+	skb_tx_timestamp(skb);
 	stmmac_flush_tx_descriptors(priv, queue);
 	stmmac_tx_timer_arm(priv, queue);
 
-- 
2.43.5