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

[Russell King (Oracle)]

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 at gmail.com wrote:
> > From: Arınç ÜNAL <arinc.unal at 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 at 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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