linux-kernel - Re: [PATCH v10 4/4] net: dsa: mv88e6xxx: Add support for mv88e6393x family of Marvell

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Date:   Fri, 20 Nov 2020 02:54:36 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Marek Behun <marek.behun@....cz>
Cc:     Pavana Sharma <pavana.sharma@...i.com>, lkp@...el.com,
        ashkan.boldaji@...i.com, clang-built-linux@...glegroups.com,
        davem@...emloft.net, f.fainelli@...il.com,
        gregkh@...uxfoundation.org, kbuild-all@...ts.01.org,
        kuba@...nel.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org, robh+dt@...nel.org,
        devicetree@...r.kernel.org, vivien.didelot@...il.com
Subject: Re: [PATCH v10 4/4] net: dsa: mv88e6xxx: Add support for mv88e6393x
 family  of Marvell

On Fri, Nov 20, 2020 at 02:43:11AM +0100, Marek Behun wrote:
> Hi Andrew,
> 
> On Fri, 20 Nov 2020 02:29:06 +0100
> Andrew Lunn <andrew@...n.ch> wrote:
> 
> > > +	if (speed >= 2500 && port > 0 && port < 9)
> > > +		return -EOPNOTSUPP;  
> > 
> > Maybe i'm missing something, but it looks like at this point you can
> > call
> > 
> > 	return mv88e6xxx_port_set_speed_duplex(chip, port, speed, true, true, duplex);
> 
> He can't. That function does not support speed 5000. You can't simply
> add it, because it clashes with register value for speed 2500 on
> previous switches (Peridot, Topaz).
> 
> 	Amethyst reg val	Peridot + Topaz reg val
> 2500	SPD_1000 | ALT_BIT	SPD_10000 | ALT_BIT
> 5000	SPD_10000 | ALT_BIT	not supported
> 10000	SPD_UNFORCED		SPD_UNFORCED

Hi Marek

O.K, as i said, i might be missing something :-)

I think a comment would be nice, pointing this out. Otherwise somebody
might try refactoring it, and make the same mistake!

      Andrew