linux-kernel - Re: [PATCH net] net: fec: correct rx_bytes statistic for the case SHIFT16 is set

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Message-ID: <aQzKhRDA7gvYZ/FZ@lizhi-Precision-Tower-5810>
Date: Thu, 6 Nov 2025 11:19:17 -0500
From: Frank Li <Frank.li@....com>
To: Wei Fang <wei.fang@....com>
Cc: shenwei.wang@....com, xiaoning.wang@....com, andrew+netdev@...n.ch,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, eric@...int.com, imx@...ts.linux.dev,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] net: fec: correct rx_bytes statistic for the case
 SHIFT16 is set

On Thu, Nov 06, 2025 at 10:14:21AM +0800, Wei Fang wrote:
> Two additional bytes in front of each frame received into the RX FIFO if
> SHIFT16 is set, so we need to subtract the extra two bytes from pkt_len
> to correct the statistic of rx_bytes.
>
> Fixes: 3ac72b7b63d5 ("net: fec: align IP header in hardware")
> Signed-off-by: Wei Fang <wei.fang@....com>

Reviewed-by: Frank Li <Frank.Li@....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 1edcfaee6819..3222359ac15b 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -1835,6 +1835,8 @@ fec_enet_rx_queue(struct net_device *ndev, u16 queue_id, int budget)
>  		ndev->stats.rx_packets++;
>  		pkt_len = fec16_to_cpu(bdp->cbd_datlen);
>  		ndev->stats.rx_bytes += pkt_len;
> +		if (fep->quirks & FEC_QUIRK_HAS_RACC)
> +			ndev->stats.rx_bytes -= 2;
>
>  		index = fec_enet_get_bd_index(bdp, &rxq->bd);
>  		page = rxq->rx_skb_info[index].page;
> --
> 2.34.1
>