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

From: "Russell King (Oracle)" <linux@armlinux.org.uk>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: "Andrew Lunn" <andrew@lunn.ch>,
	"Heiner Kallweit" <hkallweit1@gmail.com>,
	"Alexandre Belloni" <alexandre.belloni@bootlin.com>,
	"Alvin __ipraga" <alsi@bang-olufsen.dk>,
	"Claudiu Manoil" <claudiu.manoil@nxp.com>,
	"David S. Miller" <davem@davemloft.net>,
	"DENG Qingfang" <dqfext@gmail.com>,
	"Eric Dumazet" <edumazet@google.com>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"George McCollister" <george.mccollister@gmail.com>,
	"Hauke Mehrtens" <hauke@hauke-m.de>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Kurt Kanzenbach" <kurt@linutronix.de>,
	"Landen Chao" <Landen.Chao@mediatek.com>,
	"Linus Walleij" <linus.walleij@linaro.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org,
	"Matthias Brugger" <matthias.bgg@gmail.com>,
	netdev@vger.kernel.org, "Paolo Abeni" <pabeni@redhat.com>,
	"Sean Wang" <sean.wang@mediatek.com>,
	UNGLinuxDriver@microchip.com,
	"Vivien Didelot" <vivien.didelot@gmail.com>,
	"Woojung Huh" <woojung.huh@microchip.com>,
	"Marek Behún" <kabel@kernel.org>
Subject: Re: [PATCH RFC net-next 5/5] net: dsa: always use phylink for CPU and DSA ports
Date: Wed, 6 Jul 2022 17:24:09 +0100	[thread overview]
Message-ID: <YsW3KSeeQBiWQOz/@shell.armlinux.org.uk> (raw)
In-Reply-To: <20220706102621.hfubvn3wa6wlw735@skbuf>

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.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 40Mbps down 10Mbps up. Decent connectivity at last!