Re: [PATCH net v5 3/6] net: dsa: mt7530: fix handling of BPDUs on MT7530 switch

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: arinc9.unal@gmail.com, "Arınç ÜNAL" <arinc.unal@arinc9.com>,
	"Daniel Golle" <daniel@makrotopia.org>,
	"Landen Chao" <Landen.Chao@mediatek.com>,
	"DENG Qingfang" <dqfext@gmail.com>,
	"Sean Wang" <sean.wang@mediatek.com>,
	"Andrew Lunn" <andrew@lunn.ch>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	"AngeloGioacchino Del Regno"
	<angelogioacchino.delregno@collabora.com>,
	"Frank Wunderlich" <frank-w@public-files.de>,
	"Bartel Eerdekens" <bartel.eerdekens@constell8.be>,
	mithat.guner@xeront.com, erkin.bozoglu@xeront.com,
	linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH net v5 3/6] net: dsa: mt7530: fix handling of BPDUs on MT7530 switch
Date: Fri, 16 Jun 2023 11:19:18 +0100	[thread overview]
Message-ID: <ZIw3JiJlnNZYf0/Z@shell.armlinux.org.uk> (raw)
In-Reply-To: <20230616101108.wq5aote3yjpekilu@skbuf>

On Fri, Jun 16, 2023 at 01:11:08PM +0300, Vladimir Oltean wrote:
> On Fri, Jun 16, 2023 at 05:53:24AM +0300, arinc9.unal@gmail.com wrote:
> > From: Arınç ÜNAL <arinc.unal@arinc9.com>
> > 
> > BPDUs are link-local frames, therefore they must be trapped to the CPU
> > port. Currently, the MT7530 switch treats BPDUs as regular multicast
> > frames, therefore flooding them to user ports. To fix this, set BPDUs to be
> > trapped to the CPU port.
> > 
> > Fixes: b8f126a8d543 ("net-next: dsa: add dsa support for Mediatek MT7530 switch")
> > Signed-off-by: Arınç ÜNAL <arinc.unal@arinc9.com>
> > ---
> >  drivers/net/dsa/mt7530.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/net/dsa/mt7530.c b/drivers/net/dsa/mt7530.c
> > index e9fbe7ae6c2c..7b72cf3a0e30 100644
> > --- a/drivers/net/dsa/mt7530.c
> > +++ b/drivers/net/dsa/mt7530.c
> > @@ -2262,6 +2262,10 @@ mt7530_setup(struct dsa_switch *ds)
> >  
> >  	priv->p6_interface = PHY_INTERFACE_MODE_NA;
> >  
> > +	/* Trap BPDUs to the CPU port */
> > +	mt7530_rmw(priv, MT753X_BPC, MT753X_BPDU_PORT_FW_MASK,
> > +		   MT753X_BPDU_CPU_ONLY);
> > +
> >  	/* Enable and reset MIB counters */
> >  	mt7530_mib_reset(ds);
> >  
> > -- 
> > 2.39.2
> > 
> 
> Ok, so this issue dates back to v4.12, but the patch won't apply that
> far due to the difference in patch context.
> 
> Since the definition itself of the MT753X_BPC register was added as part
> of commit c288575f7810 ("net: dsa: mt7530: Add the support of MT7531
> switch") - dated v5.10 - then this patch cannot be practically be
> backported beyond that.
> 
> So I see no possible objection to the request I'm about to make, which is:
> please group this and the identical logic from mt7531_setup() into a
> common function and call that.

I agree.

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