netdev - Re: [PATCH 1/3] net: ocelot: add support to get mac from device-tree

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Date:   Fri, 29 Oct 2021 11:35:43 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Clément Léger <clement.leger@...tlin.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] net: ocelot: add support to get mac from device-tree

On Fri, Oct 29, 2021 at 08:09:37AM +0200, Clément Léger wrote:
> Le Thu, 28 Oct 2021 14:51:43 +0000,
> Vladimir Oltean <vladimir.oltean@....com> a écrit :
>
> > On Thu, Oct 28, 2021 at 04:38:25PM +0200, Clément Léger wrote:
> > > Le Thu, 28 Oct 2021 14:22:55 +0000,
> > > Vladimir Oltean <vladimir.oltean@....com> a écrit :
> > >
> > > > On Thu, Oct 28, 2021 at 04:15:22PM +0200, Clément Léger wrote:
> > > > > Le Thu, 28 Oct 2021 14:06:12 +0000,
> > > > > Vladimir Oltean <vladimir.oltean@....com> a écrit :
> > > > >
> > > > > > On Thu, Oct 28, 2021 at 03:49:30PM +0200, Clément Léger
> > > > > > wrote:
> > > > > > > Add support to get mac from device-tree using
> > > > > > > of_get_mac_address.
> > > > > > >
> > > > > > > Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> > > > > > > ---
> > > > > > >  drivers/net/ethernet/mscc/ocelot_vsc7514.c | 5 ++++-
> > > > > > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > > > > >
> > > > > > > diff --git a/drivers/net/ethernet/mscc/ocelot_vsc7514.c
> > > > > > > b/drivers/net/ethernet/mscc/ocelot_vsc7514.c index
> > > > > > > d51f799e4e86..c39118e5b3ee 100644 ---
> > > > > > > a/drivers/net/ethernet/mscc/ocelot_vsc7514.c +++
> > > > > > > b/drivers/net/ethernet/mscc/ocelot_vsc7514.c @@ -526,7
> > > > > > > +526,10 @@ static int ocelot_chip_init(struct ocelot
> > > > > > > *ocelot, const struct ocelot_ops *ops)
> > > > > > > ocelot_pll5_init(ocelot);
> > > > > > > -	eth_random_addr(ocelot->base_mac);
> > > > > > > +	ret = of_get_mac_address(ocelot->dev->of_node,
> > > > > > > ocelot->base_mac);
> > > > > >
> > > > > > Why not per port? This is pretty strange, I think.
> > > > >
> > > > > Hi Vladimir,
> > > > >
> > > > > Currently, all ports share the same base mac address (5 first
> > > > > bytes). The final mac address per port is computed in
> > > > > ocelot_probe_port by adding the port number as the last byte of
> > > > > the mac_address provided.
> > > > >
> > > > > Clément
> > > >
> > > > Yes, I know that, but that's not my point.
> > > > Every switch port should be pretty much compliant with
> > > > ethernet-controller.yaml, if it could inherit that it would be
> > > > even better. And since mac-address is an ethernet-controller.yaml
> > > > property, it is pretty much non-obvious at all that you put the
> > > > mac-address property directly under the switch, and manually add
> > > > 0, 1, 2, 3 etc to it. My request was to parse the mac-address
> > > > property of each port. Like this:
> > > >
> > > > base_mac = random;
> > > >
> > > > for_each_port() {
> > > > 	err = of_get_mac_address(port_dn, &port_mac);
> > > > 	if (err)
> > > > 		port_mac = base_mac + port;
> > > > }
> > >
> > > Ok indeed. So I will parse each port for a mac-address property. Do
> > > you also want a fallback to use the switch base mac if not
> > > specified in port or should I keep the use of a default random mac
> > > as the base address anyway ?
> >
> > Isn't the pseudocode I posted above explicit enough? Sorry...
> > Keep doing what the driver is doing right now, with an optional
> > mac-address override per port.
> > Why would we read the mac-address property of the switch? Which other
> > switch driver does that? Are there device trees in circulation where
> > this is being done?
>
> BTW, this is actually done on sparx5 switch driver.

Highly inconsistent, but true. I'm saying that because
Documentation/devicetree/bindings/net/microchip,sparx5-switch.yaml says
that "mac-address" should be under "switch", but then proceeds to put it
under "port@64" in the example.

Most likely not caught during review, I'm not sure if this could be
considered good practice.

> > > > > > > +	if (ret)
> > > > > > > +		eth_random_addr(ocelot->base_mac);
> > > > > > > +
> > > > > > >  	ocelot->base_mac[5] &= 0xf0;
> > > > > > >
> > > > > > >  	return 0;
> > > > > > > --
> > > > > > > 2.33.0
> > > > > >
> > > >
> >
>
>
>
> --
> Clément Léger,
> Embedded Linux and Kernel engineer at Bootlin
> https://bootlin.com/