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: Fri, 8 Jul 2022 16:25:03 +0100	[thread overview]
Message-ID: <YshMT3KP/B6BiEIg@shell.armlinux.org.uk> (raw)
In-Reply-To: <20220707193753.2j67ni3or3bfkt6k@skbuf>

Hi,

On Thu, Jul 07, 2022 at 10:37:53PM +0300, Vladimir Oltean wrote:
> +static int dsa_port_fixup_broken_dt(struct dsa_port *dp)

As I mentioned, I doubt that Andrew considers this "broken DT" as he's
been promoting this as a standard DSA feature.

> +{
> +	struct property_entry fixed_link_props[] = {
> +		PROPERTY_ENTRY_BOOL("full-duplex"),
> +		PROPERTY_ENTRY_U32("speed", 1000), /* TODO determine actual speed */
> +		{},
> +	};
> +	struct property_entry port_props[3] = {};
> +	struct fwnode_handle *fixed_link_fwnode;
> +	struct fwnode_handle *new_port_fwnode;
> +	struct device_node *dn = dp->dn;
> +	phy_interface_t mode;
> +	int err;
> +
> +	if (of_parse_phandle(dn, "phy-handle", 0) ||
> +	    of_phy_is_fixed_link(dn))
> +		/* Nothing broken, nothing to fix.
> +		 * TODO: As discussed with Russell, maybe phylink could provide
> +		 * a more comprehensive helper to determine what constitutes a
> +		 * valid fwnode binding than this guerilla kludge.
> +		 */
> +		return 0;

I think this is sufficient. Yes, phylink accepts "phy" and "phy-device"
because it has to for compatibility with other drivers, but the binding
document for DSA quite clearly states that "phy-handle" is what DSA
accepts, so DT in the kernel will be validated against the yaml file
and enforce correctness here.

We do need to check for "sfp" being present as well.

> +
> +	err = of_get_phy_mode(dn, &mode);
> +	if (err)
> +		/* TODO this may be missing too, ask the driver for the
> +		 * max-speed interface mode for this port
> +		 */
> +		mode = PHY_INTERFACE_MODE_NA;

I think it would be easier to omit the phy-mode property in the swnode
if it isn't present in DT, because then we can handle that in
dsa_port_phylink_create() as I've done in my patch series via the
ds->ops->phylink_get_caps() method.

> +
> +	port_props[0] = PROPERTY_ENTRY_U32("reg", dp->index);

You said in one of your other replies that this node we're constructing
is only for phylink, do we need the "reg" property? phylink doesn't care
about it.

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