linux-kernel - Re: [net-next: PATCH] net: dsa: mv88e6xxx: fix speed setting for CPU/DSA ports

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Message-ID: <CAPv3WKdFNOPRg45TiJuAVuxM0LjEnB0qZH70J1rMenJs7eBJzw@mail.gmail.com>
Date:   Mon, 25 Jul 2022 02:18:45 +0200
From:   Marcin Wojtas <mw@...ihalf.com>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        netdev <netdev@...r.kernel.org>, Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Grzegorz Jaszczyk <jaz@...ihalf.com>,
        Tomasz Nowicki <tn@...ihalf.com>
Subject: Re: [net-next: PATCH] net: dsa: mv88e6xxx: fix speed setting for
 CPU/DSA ports

Hi Vladimir,


pon., 25 lip 2022 o 01:38 Vladimir Oltean <olteanv@...il.com> napisał(a):
>
> Hi Marcin,
>
> On Thu, Jul 14, 2022 at 03:00:21AM +0200, Marcin Wojtas wrote:
> > Commit 3c783b83bd0f ("net: dsa: mv88e6xxx: get rid of SPEED_MAX setting")
> > stopped relying on SPEED_MAX constant and hardcoded speed settings
> > for the switch ports and rely on phylink configuration.
> >
> > It turned out, however, that when the relevant code is called,
> > the mac_capabilites of CPU/DSA port remain unset.
> > mv88e6xxx_setup_port() is called via mv88e6xxx_setup() in
> > dsa_tree_setup_switches(), which precedes setting the caps in
> > phylink_get_caps down in the chain of dsa_tree_setup_ports().
> >
> > As a result the mac_capabilites are 0 and the default speed for CPU/DSA
> > port is 10M at the start. To fix that execute phylink_get_caps() callback
> > which fills port's mac_capabilities before they are processed.
> >
> > Fixes: 3c783b83bd0f ("net: dsa: mv88e6xxx: get rid of SPEED_MAX setting")
> > Signed-off-by: Marcin Wojtas <mw@...ihalf.com>
> > ---
> >  drivers/net/dsa/mv88e6xxx/chip.c | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
> > index 37b649501500..9fab76f256bb 100644
> > --- a/drivers/net/dsa/mv88e6xxx/chip.c
> > +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> > @@ -3293,7 +3293,12 @@ static int mv88e6xxx_setup_port(struct mv88e6xxx_chip *chip, int port)
> >        * port and all DSA ports to their maximum bandwidth and full duplex.
> >        */
> >       if (dsa_is_cpu_port(ds, port) || dsa_is_dsa_port(ds, port)) {
> > -             unsigned long caps = dp->pl_config.mac_capabilities;
> > +             unsigned long caps;
> > +
> > +             if (ds->ops->phylink_get_caps)
> > +                     ds->ops->phylink_get_caps(ds, port, &dp->pl_config);
> > +
> > +             caps = dp->pl_config.mac_capabilities;
>
> We'll need this bug fixed in net-next one way or another.
> If you resend this patch, please change the following:
>
> (1) it's silly to (a) check for the presence of ds->ops->phylink_get_caps and
>     (b) do an indirect function call when you know that the implementation is
>     mv88e6xxx_get_caps(). So just call that.
>
> (2) please don't touch &dp->pl_config, just create an on-stack
>     struct phylink_config pl_config, and let DSA do its thing with
>     &dp->pl_config whenever the timing of dsa_port_phylink_create() is.
>

I can of course apply both suggestions, however, I am wondering if I
should resend them at all, as Russell's series is still being
discussed. IMO it may be worth waiting whether it makes it before the
merge window - if not, I can resend this patch after v5.20-rc1,
targetting the net branch. What do you think?

Thanks,
Marcin

> >
> >               if (chip->info->ops->port_max_speed_mode)
> >                       mode = chip->info->ops->port_max_speed_mode(port);
> > --
> > 2.29.0
> >