Re: [PATCH v2] net: ethernet: mtk_eth_soc: fix mtu warning - Russell King

From: Russell King - ARM Linux admin <linux@armlinux.org.uk>
To: Andrew Lunn <andrew@lunn.ch>
Cc: "Frank Wunderlich" <frank-w@public-files.de>,
	netdev@vger.kernel.org, "Sean Wang" <sean.wang@mediatek.com>,
	linux-kernel@vger.kernel.org,
	"Mark Lee" <Mark-MC.Lee@mediatek.com>,
	"René van Dorst" <opensource@vdorst.com>,
	linux-mediatek@lists.infradead.org,
	"John Crispin" <john@phrozen.org>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	linux-arm-kernel@lists.infradead.org,
	"Felix Fietkau" <nbd@nbd.name>
Subject: Re: [PATCH v2] net: ethernet: mtk_eth_soc: fix mtu warning
Date: Thu, 9 Jul 2020 21:31:34 +0100	[thread overview]
Message-ID: <20200709203134.GI1551@shell.armlinux.org.uk> (raw)
In-Reply-To: <20200709134115.GK928075@lunn.ch>

On Thu, Jul 09, 2020 at 03:41:15PM +0200, Andrew Lunn wrote:
> On Thu, Jul 09, 2020 at 07:57:42AM +0200, Frank Wunderlich wrote:
> > From: René van Dorst <opensource@vdorst.com>
> > 
> > in recent Kernel-Versions there are warnings about incorrect MTU-Size
> > like these:
> > 
> > mt7530 mdio-bus:00: nonfatal error -95 setting MTU on port x
> > eth0: mtu greater than device maximum
> > mtk_soc_eth 1b100000.ethernet eth0: error -22 setting MTU to include DSA overhead
> > 
> > Fixes: bfcb813203e6 ("net: dsa: configure the MTU for switch ports")
> > Fixes: 72579e14a1d3 ("net: dsa: don't fail to probe if we couldn't set the MTU")
> > Fixes: 7a4c53bee332 ("net: report invalid mtu value via netlink extack")
> > Signed-off-by: René van Dorst <opensource@vdorst.com>
> > Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
> > ---
> > changes in v2:
> >   Fixes: tag show 12-chars of sha1 and moved above other tags
> > ---
> >  drivers/net/ethernet/mediatek/mtk_eth_soc.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > index 85735d32ecb0..00e3d70f7d07 100644
> > --- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > +++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
> > @@ -2891,6 +2891,10 @@ static int mtk_add_mac(struct mtk_eth *eth, struct device_node *np)
> >  	eth->netdev[id]->irq = eth->irq[0];
> >  	eth->netdev[id]->dev.of_node = np;
> > 
> > +	eth->netdev[id]->mtu = 1536;
> 
> Hi Frank
> 
> Don't change to MTU from the default. Anybody using this interface for
> non-DSA traffic expects the default MTU. DSA will change it as needed.
> 
> > +	eth->netdev[id]->min_mtu = ETH_MIN_MTU;
> 
> No need to set the minimum. ether_setup() will initialize it.
> 
> > +	eth->netdev[id]->max_mtu = 1536;
> 
> I assume this is enough to make the DSA warning go away, but it is the
> true max? I have a similar patch for the FEC driver which i should
> post sometime. Reviewing the FEC code and after some testing, i found
> the real max was 2K - 64.

Are there any plans to solve these warnings for Marvell 88e6xxx DSA ports?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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