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

From: Marek Behún <[email-masked]>
Date: Fri, 8 Jul 2022 17:40:30 +0200

On Fri, 8 Jul 2022 16:25:03 +0100
"Russell King (Oracle)" <[email-masked]> wrote:

> 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.

We don't. Vladimir wrote: "We don't even need the "reg" u32 property, I
just added that for no reason (I wasn't completely sure what the API
offers, then I didn't remove it)."

Marek