From: Vladimir Oltean <olteanv@gmail.com>
To: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Cc: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
netdev@vger.kernel.org, Zhao Qiang <qiang.zhao@nxp.com>,
Li Yang <leoyang.li@nxp.com>, Andrew Lunn <andrew@lunn.ch>,
linux-kernel@vger.kernel.org,
Vladimir Oltean <vladimir.oltean@nxp.com>
Subject: Re: [PATCH net v2 1/3] ethernet: ucc_geth: set dev->max_mtu to 1518
Date: Sun, 20 Dec 2020 10:05:55 +0200 [thread overview]
Message-ID: <20201220080555.tgv3ndlkhzbvcpx7@skbuf> (raw)
In-Reply-To: <20201218105538.30563-2-rasmus.villemoes@prevas.dk>
On Fri, Dec 18, 2020 at 11:55:36AM +0100, Rasmus Villemoes wrote:
> All the buffers and registers are already set up appropriately for an
> MTU slightly above 1500, so we just need to expose this to the
> networking stack. AFAICT, there's no need to implement .ndo_change_mtu
> when the receive buffers are always set up to support the max_mtu.
>
> This fixes several warnings during boot on our mpc8309-board with an
> embedded mv88e6250 switch:
>
> mv88e6085 mdio@e0102120:10: nonfatal error -34 setting MTU 1500 on port 0
> ...
> mv88e6085 mdio@e0102120:10: nonfatal error -34 setting MTU 1500 on port 4
> ucc_geth e0102000.ethernet eth1: error -22 setting MTU to 1504 to include DSA overhead
>
> The last line explains what the DSA stack tries to do: achieving an MTU
> of 1500 on-the-wire requires that the master netdevice connected to
> the CPU port supports an MTU of 1500+the tagging overhead.
>
> Fixes: bfcb813203e6 ("net: dsa: configure the MTU for switch ports")
> Cc: Vladimir Oltean <vladimir.oltean@nxp.com>
> Reviewed-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
> ---
Reviewed-by: Vladimir Oltean <vladimir.oltean@nxp.com>
next prev parent reply other threads:[~2020-12-20 8:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-18 10:55 [PATCH net v2 0/3] ucc_geth fixes Rasmus Villemoes
2020-12-18 10:55 ` [PATCH net v2 1/3] ethernet: ucc_geth: set dev->max_mtu to 1518 Rasmus Villemoes
2020-12-20 8:05 ` Vladimir Oltean [this message]
2020-12-18 10:55 ` [PATCH net v2 2/3] ethernet: ucc_geth: fix definition and size of ucc_geth_tx_global_pram Rasmus Villemoes
2020-12-18 10:55 ` [PATCH net v2 3/3] ethernet: ucc_geth: fix use-after-free in ucc_geth_remove() Rasmus Villemoes
2020-12-22 1:40 ` [PATCH net v2 0/3] ucc_geth fixes patchwork-bot+netdevbpf
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