linux-kernel - Re: [net PATCH v2 2/2] net: ravb: Fix R-Car RX frame size limit

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Message-ID: <20240828150337.GA3306821@ragnatech.se>
Date: Wed, 28 Aug 2024 17:03:37 +0200
From: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>
To: Paul Barker <paul.barker.ct@...renesas.com>
Cc: Sergey Shtylyov <s.shtylyov@....ru>,
	"David S . Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Andrew Lunn <andrew@...n.ch>, Biju Das <biju.das.jz@...renesas.com>,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	Lad Prabhakar <prabhakar.mahadev-lad.rj@...renesas.com>,
	Mitsuhiro Kimura <mitsuhiro.kimura.kc@...esas.com>,
	Geert Uytterhoeven <geert+renesas@...der.be>,
	netdev@...r.kernel.org, linux-renesas-soc@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [net PATCH v2 2/2] net: ravb: Fix R-Car RX frame size limit

Hi Paul,

Thanks for your work.

On 2024-08-28 11:22:26 +0100, Paul Barker wrote:
> The RX frame size limit should not be based on the current MTU setting.
> Instead it should be based on the hardware capabilities.
> 
> Fixes: c156633f1353 ("Renesas Ethernet AVB driver proper")
> Reviewed-by: Sergey Shtylyov <s.shtylyov@....ru>
> Signed-off-by: Paul Barker <paul.barker.ct@...renesas.com>

Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@...natech.se>

> ---
>  drivers/net/ethernet/renesas/ravb_main.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/renesas/ravb_main.c b/drivers/net/ethernet/renesas/ravb_main.c
> index 471a68b0146e..b103632de4d4 100644
> --- a/drivers/net/ethernet/renesas/ravb_main.c
> +++ b/drivers/net/ethernet/renesas/ravb_main.c
> @@ -555,8 +555,10 @@ static void ravb_emac_init_gbeth(struct net_device *ndev)
>  
>  static void ravb_emac_init_rcar(struct net_device *ndev)
>  {
> +	struct ravb_private *priv = netdev_priv(ndev);
> +
>  	/* Receive frame limit set register */

I wonder if we also should expand this comment to explain the addition 
of ETH_FCS_LEN, I have to look this up every time :-) How would you feel 
about adding something like?

    /* Set receive frame length
     *
     * The length set here described the frame from the destination 
     * address up to and including the CRC data. However only the frame 
     * data, exuding the CRC, are transferred to memory. To allow for 
     * the largest frames add the CRC length to the maximum Rx 
     * descriptor size.
     */

> -	ravb_write(ndev, ndev->mtu + ETH_HLEN + VLAN_HLEN + ETH_FCS_LEN, RFLR);
> +	ravb_write(ndev, priv->info->rx_max_frame_size + ETH_FCS_LEN, RFLR);
>  
>  	/* EMAC Mode: PAUSE prohibition; Duplex; RX Checksum; TX; RX */
>  	ravb_write(ndev, ECMR_ZPF | ECMR_DM |
> -- 
> 2.43.0
> 

-- 
Kind Regards,
Niklas Söderlund