netdev - Re: [PATCH RFC net-next 5/5] net: dsa: always use phylink for CPU and DSA ports

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Message-ID: <YsW3KSeeQBiWQOz/@shell.armlinux.org.uk>
Date:   Wed, 6 Jul 2022 17:24:09 +0100
From:   "Russell King (Oracle)" <linux@...linux.org.uk>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Alvin __ipraga <alsi@...g-olufsen.dk>,
        Claudiu Manoil <claudiu.manoil@....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>,
        Hauke Mehrtens <hauke@...ke-m.de>,
        Jakub Kicinski <kuba@...nel.org>,
        Kurt Kanzenbach <kurt@...utronix.de>,
        Landen Chao <Landen.Chao@...iatek.com>,
        Linus Walleij <linus.walleij@...aro.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>,
        Sean Wang <sean.wang@...iatek.com>,
        UNGLinuxDriver@...rochip.com,
        Vivien Didelot <vivien.didelot@...il.com>,
        Woojung Huh <woojung.huh@...rochip.com>,
        Marek Behún <kabel@...nel.org>
Subject: Re: [PATCH RFC net-next 5/5] net: dsa: always use phylink for CPU
 and DSA ports

On Wed, Jul 06, 2022 at 01:26:21PM +0300, Vladimir Oltean wrote:
> Hello,
> 
> On Tue, Jul 05, 2022 at 10:48:07AM +0100, Russell King (Oracle) wrote:
> > diff --git a/net/dsa/port.c b/net/dsa/port.c
> > index 35b4e1f8dc05..34487e62eb03 100644
> > --- a/net/dsa/port.c
> > +++ b/net/dsa/port.c
> > @@ -1525,6 +1525,7 @@ int dsa_port_phylink_create(struct dsa_port *dp)
> >  {
> >  	struct dsa_switch *ds = dp->ds;
> >  	phy_interface_t mode, def_mode;
> > +	struct device_node *phy_np;
> >  	int err;
> >  
> >  	/* Presence of phylink_mac_link_state or phylink_mac_an_restart is
> > @@ -1559,6 +1560,13 @@ int dsa_port_phylink_create(struct dsa_port *dp)
> >  		return PTR_ERR(dp->pl);
> >  	}
> >  
> > +	if (dp->type == DSA_PORT_TYPE_CPU || dp->type == DSA_PORT_TYPE_DSA) {
> > +		phy_np = of_parse_phandle(dp->dn, "phy-handle", 0);
> > +		of_node_put(phy_np);
> > +		if (!phy_np)
> > +			err = phylink_set_max_fixed_link(dp->pl);
> 
> Can we please limit phylink_set_max_link_speed() to just the CPU ports
> where a fixed-link property is also missing, not just a phy-handle?
> Although to be entirely correct, we can also have MLO_AN_INBAND, which
> wouldn't be covered by these 2 checks and would still represent a valid
> DT binding.

phylink_set_max_fixed_link() already excludes itself:

        if (pl->cfg_link_an_mode != MLO_AN_PHY || pl->phydev || pl->sfp_bus)
                return -EBUSY;

intentionally so that if there is anything specified for the port, be
that a fixed link or in-band, then phylink_set_max_fixed_link() errors
out with -EBUSY.

The only case that it can't detect is if there is a PHY that may be
added to phylink at a later time, and that is what the check above
is for.

-- 
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