linux-kernel - Re: [PATCH v5 net-next 3/5] net: fec: add rx_frame

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Message-ID: <aLoA9mVfYoGOfIUg@lizhi-Precision-Tower-5810>
Date: Thu, 4 Sep 2025 17:13:26 -0400
From: Frank Li <Frank.li@....com>
To: Shenwei Wang <shenwei.wang@....com>
Cc: Wei Fang <wei.fang@....com>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Alexei Starovoitov <ast@...nel.org>,
	Daniel Borkmann <daniel@...earbox.net>,
	Jesper Dangaard Brouer <hawk@...nel.org>,
	John Fastabend <john.fastabend@...il.com>,
	Clark Wang <xiaoning.wang@....com>,
	Stanislav Fomichev <sdf@...ichev.me>, imx@...ts.linux.dev,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-imx@....com
Subject: Re: [PATCH v5 net-next 3/5] net: fec: add rx_frame_size to support
 configurable RX length

On Thu, Sep 04, 2025 at 03:35:00PM -0500, Shenwei Wang wrote:
> Add a new rx_frame_size member in the fec_enet_private structure to
> track the RX buffer size. On the Jumbo frame enabled system, the value
> will be recalculated whenever the MTU is updated, allowing the driver
> to allocate RX buffer efficiently.
>
> Configure the MAX_FL (Maximum Frame Length) based on the current MTU,
> by changing the OPT_FRAME_SIZE macro.
>
> Configure the TRUNC_FL (Frame Truncation Length) based on the smaller
> value between max_buf_size and the rx_frame_size to maintain consistent
> RX error behavior, regardless of whether Jumbo frames are enabled.
>
> Signed-off-by: Shenwei Wang <shenwei.wang@....com>
> ---

Reviewed-by: Frank Li <Frank.Li@....com>

>  drivers/net/ethernet/freescale/fec.h      | 1 +
>  drivers/net/ethernet/freescale/fec_main.c | 5 +++--
>  2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/ethernet/freescale/fec.h b/drivers/net/ethernet/freescale/fec.h
> index 47317346b2f3..f1032a11aa76 100644
> --- a/drivers/net/ethernet/freescale/fec.h
> +++ b/drivers/net/ethernet/freescale/fec.h
> @@ -621,6 +621,7 @@ struct fec_enet_private {
>  	unsigned int total_rx_ring_size;
>  	unsigned int max_buf_size;
>  	unsigned int pagepool_order;
> +	unsigned int rx_frame_size;
>
>  	struct	platform_device *pdev;
>
> diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
> index f046d32a62fb..cf5118838f9c 100644
> --- a/drivers/net/ethernet/freescale/fec_main.c
> +++ b/drivers/net/ethernet/freescale/fec_main.c
> @@ -253,7 +253,7 @@ MODULE_PARM_DESC(macaddr, "FEC Ethernet MAC address");
>  #if defined(CONFIG_M523x) || defined(CONFIG_M527x) || defined(CONFIG_M528x) || \
>      defined(CONFIG_M520x) || defined(CONFIG_M532x) || defined(CONFIG_ARM) || \
>      defined(CONFIG_ARM64)
> -#define	OPT_FRAME_SIZE	(fep->max_buf_size << 16)
> +#define	OPT_FRAME_SIZE	((fep->netdev->mtu + ETH_HLEN + ETH_FCS_LEN) << 16)
>  #else
>  #define	OPT_FRAME_SIZE	0
>  #endif
> @@ -1191,7 +1191,7 @@ fec_restart(struct net_device *ndev)
>  		else
>  			val &= ~FEC_RACC_OPTIONS;
>  		writel(val, fep->hwp + FEC_RACC);
> -		writel(fep->max_buf_size, fep->hwp + FEC_FTRL);
> +		writel(min(fep->rx_frame_size, fep->max_buf_size), fep->hwp + FEC_FTRL);
>  	}
>  #endif
>
> @@ -4560,6 +4560,7 @@ fec_probe(struct platform_device *pdev)
>  	pinctrl_pm_select_sleep_state(&pdev->dev);
>
>  	fep->pagepool_order = 0;
> +	fep->rx_frame_size = FEC_ENET_RX_FRSIZE;
>  	fep->max_buf_size = PKT_MAXBUF_SIZE;
>  	ndev->max_mtu = fep->max_buf_size - ETH_HLEN - ETH_FCS_LEN;
>
> --
> 2.43.0
>