Re: [PATCH net] net: dsa: microchip: keep compatibility with device tree blobs with no phy-mode

From: Rasmus Villemoes <linux@rasmusvillemoes.dk>
To: Vladimir Oltean <vladimir.oltean@nxp.com>, netdev@vger.kernel.org
Cc: "Woojung Huh" <woojung.huh@microchip.com>,
	UNGLinuxDriver@microchip.com, "Andrew Lunn" <andrew@lunn.ch>,
	"Vivien Didelot" <vivien.didelot@gmail.com>,
	"Florian Fainelli" <f.fainelli@gmail.com>,
	"Vladimir Oltean" <olteanv@gmail.com>,
	"David S. Miller" <davem@davemloft.net>,
	"Eric Dumazet" <edumazet@google.com>,
	"Jakub Kicinski" <kuba@kernel.org>,
	"Paolo Abeni" <pabeni@redhat.com>,
	"Russell King" <linux@armlinux.org.uk>,
	"Michael Grzeschik" <m.grzeschik@pengutronix.de>,
	"Oleksij Rempel" <linux@rempel-privat.de>,
	"Thorsten Leemhuis" <regressions@leemhuis.info>,
	"Alvin Šipraga" <alsi@bang-olufsen.dk>,
	"Craig McQueen" <craig@mcqueen.id.au>
Subject: Re: [PATCH net] net: dsa: microchip: keep compatibility with device tree blobs with no phy-mode
Date: Fri, 19 Aug 2022 12:19:12 +0200	[thread overview]
Message-ID: <095c6c01-d4dd-8275-19fc-f9fe1ea40ab8@rasmusvillemoes.dk> (raw)
In-Reply-To: <20220818143250.2797111-1-vladimir.oltean@nxp.com>

On 18/08/2022 16.32, Vladimir Oltean wrote:
> DSA has multiple ways of specifying a MAC connection to an internal PHY.
> One requires a DT description like this:
> 
> 	port@0 {
> 		reg = <0>;
> 		phy-handle = <&internal_phy>;
> 		phy-mode = "internal";
> 	};
> 
> (which is IMO the recommended approach, as it is the clearest
> description)
> 
> but it is also possible to leave the specification as just:
> 
> 	port@0 {
> 		reg = <0>;
> 	}
> 
> and if the driver implements ds->ops->phy_read and ds->ops->phy_write,
> the DSA framework "knows" it should create a ds->slave_mii_bus, and it
> should connect to a non-OF-based internal PHY on this MDIO bus, at an
> MDIO address equal to the port address.
> 
> There is also an intermediary way of describing things:
> 
> 	port@0 {
> 		reg = <0>;
> 		phy-handle = <&internal_phy>;
> 	};

Well, there's also e.g. arch/arm/boot/dts/at91-sama5d3_ksz9477_evb.dts
which sets the phy-mode but not the phy-handle:

                        port@0 {
                                reg = <0>;
                                label = "lan1";
                                phy-mode = "internal";
                        };

And doing that in my case seems to fix things (I wouldn't know what
phy-handle to point at anyway), so since we're still in development, I
think I'll do that. But if I want to follow the new-world-order to the
letter, should I also figure out a way to point at a phy-handle?
> Fixes: 2c709e0bdad4 ("net: dsa: microchip: ksz8795: add phylink support")
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=216320
> Reported-by: Craig McQueen <craig@mcqueen.id.au>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

I've also tested this patch on top of v5.19 without altering my .dts,
and that also seems to fix things, so I suppose you can add

Fixes: 65ac79e18120 ("net: dsa: microchip: add the phylink get_caps")
Tested-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>

Thanks,
Rasmus