linux-kernel - Re: [PATCH net-next v2 7/7] arm64: dts: mt7622: add mt7531 dsa to bananapi-bpi-r64 board

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Message-ID: <20200819085122.wiuq3fi23rebja6d@skbuf>
Date:   Wed, 19 Aug 2020 11:51:22 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Landen Chao <landen.chao@...iatek.com>
Cc:     "andrew@...n.ch" <andrew@...n.ch>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "vivien.didelot@...oirfairelinux.com" 
        <vivien.didelot@...oirfairelinux.com>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Sean Wang <Sean.Wang@...iatek.com>,
        "opensource@...rst.com" <opensource@...rst.com>,
        "frank-w@...lic-files.de" <frank-w@...lic-files.de>,
        "dqfext@...il.com" <dqfext@...il.com>
Subject: Re: [PATCH net-next v2 7/7] arm64: dts: mt7622: add mt7531 dsa to
 bananapi-bpi-r64 board

On Wed, Aug 19, 2020 at 04:15:01PM +0800, Landen Chao wrote:
> On Wed, 2020-08-19 at 00:24 +0800, Vladimir Oltean wrote:
> > On Tue, Aug 18, 2020 at 03:14:12PM +0800, Landen Chao wrote:
> > > Add mt7531 dsa to bananapi-bpi-r64 board for 5 giga Ethernet ports support.
> > > 
> > > Signed-off-by: Landen Chao <landen.chao@...iatek.com>
> > > ---
> > >  .../dts/mediatek/mt7622-bananapi-bpi-r64.dts  | 44 +++++++++++++++++++
> > >  1 file changed, 44 insertions(+)
> > > 
> > > diff --git a/arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts b/arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts
> > > index d174ad214857..c57b2571165f 100644
> > > --- a/arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts
> > > +++ b/arch/arm64/boot/dts/mediatek/mt7622-bananapi-bpi-r64.dts
> > > @@ -143,6 +143,50 @@
> > >  	mdio: mdio-bus {
> > >  		#address-cells = <1>;
> > >  		#size-cells = <0>;
> > > +
> > > +		switch@0 {
> > > +			compatible = "mediatek,mt7531";
> > > +
> [snip]
> > > +				port@6 {
> > > +					reg = <6>;
> > > +					label = "cpu";
> > > +					ethernet = <&gmac0>;
> > > +					phy-mode = "2500base-x";
> > > +				};
> > 
> > Is there any reason why you're not specifying a fixed-link node here?
> I got the below feedback in v1, so I follow the DSA common design in v2.
> v2 can work with fixed-link node or without fixed-link node in CPU port
> node.
> 
>   "This fixed-link should not be needed. The DSA driver is supposed to
>    configure the CPU port to its fastest speed by default. 2500 is
>    the fastest speed a 2500Base-X link can do..."

See this discussion and the replies to it:

https://www.spinics.net/lists/netdev/msg630102.html

I think if mt7530 is using phylink for non-netdev ports (and it is), it
would be good to have standard bindings that phylink can parse. For
example, in lack of a "pause" specifier, will the CPU port use flow
control or won't it? Why? I think there's simply no good reason why
you'd omit 3 more lines now.

> > > +			};
> > > +		};
> > > +
> > >  	};
> > >  };
> > >  
> > > -- 
> > > 2.17.1
> > 
> > Thanks,
> > -Vladimir
> 

-Vladimir