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

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Date:   Thu, 14 Jul 2022 20:44:38 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Marcin Wojtas <mw@...ihalf.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>,
        Vladimir Oltean <olteanv@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        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

On Thu, Jul 14, 2022 at 07:18:57PM +0200, Marcin Wojtas wrote:
> Hi Russell,
> 
> czw., 14 lip 2022 o 14:32 Russell King (Oracle)
> <linux@...linux.org.uk> napisał(a):
> >
> > 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>
> >
> > Please don't merge this - the plan is to submit the RFC series I sent on
> > Wednesday which deletes this code, and I'd rather not re-spin the series
> > and go through the testing again because someone else changed the code.
> 
> Thank for the heads-up. Are you planning to resend the series or
> willing to get it merged as-is? I have perhaps one comment, but I can
> apply it later as a part of fwnode_/device_ migration.
> 
> >
> > Marcin - please can you test with my RFC series, which can be found at:
> >
> > https://lore.kernel.org/all/Ys7RdzGgHbYiPyB1@shell.armlinux.org.uk/
> >
> 
> The thing is my v2 of DSA fwnode_/device_ migration is tested and
> ready to send. There will be conflicts (rather easy) with your
> patchset - I volunteer to resolve it this way or another, depending on
> what lands first. I have 2 platforms to test it with + also ACPI case
> locally.
> 
> I'd like to make things as smooth as possible and make it before the
> upcoming merge window - please share your thoughts on this.

I've also been trying to get the mv88e6xxx PCS conversion in, but
it's been held up because there's a fundamental problem in DSA that
this series is addressing.

This series is addressing a faux pas on my part, where I had forgotten
that phylink doesn't get used in DSA unless firmware specifies a
fixed-link (or a PHY) - in other words when the firmware lacks a
description of the link.

So, what do we do...

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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