Subject: Re: [PATCH] net: dsa: mv88e6xxx: fix usable ports on 88e6020

From: Lukasz Majewski <[email-masked]>
Date: Tue, 26 Mar 2024 16:52:15 +0100

Hi Matthias,

> On Tue, 2024-03-26 at 14:34 +0100, Lukasz Majewski wrote:
> > Hi Matthias,
> >   
> > > From: Michael Krummsdorf <[email-masked]>
> > > 
> > > The switch has 4 ports with 2 internal PHYs, but ports are
> > > numbered up to 6, with ports 0, 1, 5 and 6 being usable.
> > > 
> > > Fixes: 71d94a432a15 ("net: dsa: mv88e6xxx: add support for
> > > MV88E6020 switch") Signed-off-by: Michael Krummsdorf
> > > <[email-masked]> Signed-off-by: Matthias Schiffer
> > > <[email-masked]> ---
> > > 
> > > I was unfortunately too busy to notice the issue when the patch
> > > this Fixes was resubmitted in my name. It would have been better
> > > to change my From into a Based-on-patch-by or similar when
> > > modifying it  
> > 
> > The "discussion" about this work was lasting at least a few months
> > with several iterations and changing the design decisions ...
> >   
> > > - and
> > > the final version obviously wasn't even tested on an 88E6020...  
> > 
> > 
> > Can you share on which kernel version have you tested the patch that
> > you claim that testing was omitted?  
> 
> Hi Lukasz,
> 
> we are currently testing with commit 71d94a432a15 backported onto a
> recent Linux 6.1.y. At least on this kernel version, the driver will
> reject a Device Tree configuration that uses the ports 5 and 6
> (rightfully so, as num_ports is set to 4), leaving only the
> internal-PHY ports 0 and 1, and none of the *MII ports that are
> likely to be used as CPU ports.
> 
> So if the accepted version worked fine for you, your configuration
> possibly only used the first two ports,

And then the penny has dropped....

	switch@10 {
			compatible = "marvell,mv88e6250";
			reg = <0x10>;

			ports {
				#address-cells = <1>;
				#size-cells = <0>;

				port@0 {
					reg = <0>;
					label = "lan1";
				};

				port@1 {
					reg = <1>;
					label = "lan2";
				};

				port@6 {
					reg = <6>;
					label = "cpu";
					phy-mode = "rmii";
					ethernet = <&fec2>;

					fixed-link {
						   speed = <100>;
						   full-duplex;
					};
				};
			};
		};

> or newer kernels somehow
> ignore num_ports when determining if a port number is valid.
> 
> We should be able to repeat our test on a newer kernel next week if
> needed.

I think that considering the above snippet - customer was using only
port 0 and 1.

> 
> Best regards,
> Matthias
> 
> 
> >   
> > > 
> > > 
> > >  drivers/net/dsa/mv88e6xxx/chip.c | 6 +++++-
> > >  1 file changed, 5 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/net/dsa/mv88e6xxx/chip.c
> > > b/drivers/net/dsa/mv88e6xxx/chip.c index
> > > 9ed1821184ece..c95787cb90867 100644 ---
> > > a/drivers/net/dsa/mv88e6xxx/chip.c +++
> > > b/drivers/net/dsa/mv88e6xxx/chip.c @@ -5503,8 +5503,12 @@ static
> > > const struct mv88e6xxx_info mv88e6xxx_table[] = { .family =
> > > MV88E6XXX_FAMILY_6250, .name = "Marvell 88E6020",
> > >  		.num_databases = 64,
> > > -		.num_ports = 4,
> > > +		/* Ports 2-4 are not routed to pins
> > > +		 * => usable ports 0, 1, 5, 6
> > > +		 */
> > > +		.num_ports = 7,
> > >  		.num_internal_phys = 2,
> > > +		.invalid_port_mask = BIT(2) | BIT(3) | BIT(4),
> > >  		.max_vid = 4095,
> > >  		.port_base_addr = 0x8,
> > >  		.phy_base_addr = 0x0,  
> > 
> > 
> > 
> > 
> > Best regards,
> > 
> > Lukasz Majewski
> > 
> > --
> > 
> > DENX Software Engineering GmbH,      Managing Director: Erika Unter
> > HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell,
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> >    
> 

Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Erika Unter
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: [email-masked]