netdev - Re: [PATCH net-next v1 4/4] net: lan966x: generate software timestamp just before the doorbell

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Message-ID: <20250508070700.m3bufh2q4v4llbfx@DEN-DL-M31836.microchip.com>
Date: Thu, 8 May 2025 09:07:00 +0200
From: Horatiu Vultur <horatiu.vultur@...rochip.com>
To: Jason Xing <kerneljasonxing@...il.com>
CC: <irusskikh@...vell.com>, <andrew+netdev@...n.ch>, <bharat@...lsio.com>,
	<ayush.sawal@...lsio.com>, <UNGLinuxDriver@...rochip.com>,
	<mcoquelin.stm32@...il.com>, <alexandre.torgue@...s.st.com>,
	<davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
	<pabeni@...hat.com>, <horms@...nel.org>, <sgoutham@...vell.com>,
	<willemb@...gle.com>, <linux-stm32@...md-mailman.stormreply.com>,
	<linux-arm-kernel@...ts.infradead.org>, <netdev@...r.kernel.org>, Jason Xing
	<kernelxing@...cent.com>
Subject: Re: [PATCH net-next v1 4/4] net: lan966x: generate software
 timestamp just before the doorbell

The 05/08/2025 11:33, Jason Xing wrote:
> 
> From: Jason Xing <kernelxing@...cent.com>
> 
> Make sure the call of skb_tx_timestamp as close to the doorbell.
> 
> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> ---
>  drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> index 502670718104..e030f23e5145 100644
> --- a/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> +++ b/drivers/net/ethernet/microchip/lan966x/lan966x_fdma.c
> @@ -730,7 +730,6 @@ int lan966x_fdma_xmit(struct sk_buff *skb, __be32 *ifh, struct net_device *dev)
>                 }
>         }
> 
> -       skb_tx_timestamp(skb);

Changing this will break the PHY timestamping because the frame gets
modified in the next line, meaning that the classify function will
always return PTP_CLASS_NONE.

Nacked-by: Horatiu Vultur <horatiu.vultur@...rochip.com>

>         skb_push(skb, IFH_LEN_BYTES);
>         memcpy(skb->data, ifh, IFH_LEN_BYTES);
>         skb_put(skb, 4);
> @@ -768,6 +767,7 @@ int lan966x_fdma_xmit(struct sk_buff *skb, __be32 *ifh, struct net_device *dev)
>                 next_dcb_buf->ptp = true;
> 
>         /* Start the transmission */
> +       skb_tx_timestamp(skb);
>         lan966x_fdma_tx_start(tx);
> 
>         return NETDEV_TX_OK;
> --
> 2.43.5
> 

-- 
/Horatiu