netdev - Re: [PATCH net-next 0/6] net: dsa: always use phylink

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Date:   Wed, 27 Jul 2022 16:38:24 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Marek Behún <kabel@...nel.org>
Cc:     "Russell King (Oracle)" <linux@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Alvin Šipraga <alsi@...g-olufsen.dk>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Daniel Scally <djrscally@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        DENG Qingfang <dqfext@...il.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        George McCollister <george.mccollister@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        Matthias Brugger <matthias.bgg@...il.com>,
        netdev@...r.kernel.org, Paolo Abeni <pabeni@...hat.com>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Sean Wang <sean.wang@...iatek.com>,
        UNGLinuxDriver@...rochip.com,
        Vivien Didelot <vivien.didelot@...il.com>,
        Woojung Huh <woojung.huh@...rochip.com>
Subject: Re: [PATCH net-next 0/6] net: dsa: always use phylink

Hello Marek,

On Wed, Jul 27, 2022 at 11:00:51AM +0200, Marek Behún wrote:
> Dear Vladimir,
> 
> am I understanding correctly that your main objection to this series is
> that it may break other drivers?

Yes, but I'm not saying this in a way that tries to make it impossible
to make progress. But rather, I've identified 8 drivers which may lack
complete device tree descriptions:
https://patchwork.kernel.org/project/netdevbpf/patch/20220723164635.1621911-1-vladimir.oltean@nxp.com/

Simply put, I have no indication that the changes presented here are a
step in the right direction for the remaining 7 drivers. Each and every
single one of them needs to be studied and discussed separately; the
discussion has already started for some.

> Do you think it would be okay if I changed it so that only mv88e6xxx
> driver would ask for phylink for CPU/DSA ports?

It would be a good start, yes. What I could do is I could move my
validation logic from the patch linked above into dsa_port_link_register_of().
Running that logic would let DSA know which properties are missing.
Then, for drivers that don't enforce validation, we could add new
dsa_switch_ops that separately ask the driver what phy-mode to use
(if missing) and what speed/duplex to use (if missing). Drivers can use
whatever heuristic is appropriate for their deployments to respond to this.
If the phy-mode and speed/duplex are finally resolved, DSA can create a
software_node and register with phylink that way. Otherwise, DSA will
continue to do what it does today, i.e. skip phylink registration.

How does that sound?