Re: [PATCH net-next v2 1/3] net: macb: fix SGMII with inband aneg disabled

[Conor Dooley <conor@kernel.org>]

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On Thu, Mar 05, 2026 at 05:47:34AM -0800, Charles Perry wrote:
> On Wed, Mar 04, 2026 at 06:39:38PM +0000, Russell King (Oracle) wrote:
> > On Wed, Mar 04, 2026 at 06:06:20PM +0000, Conor Dooley wrote:
> > > On Wed, Mar 04, 2026 at 04:55:37PM +0000, Russell King (Oracle) wrote:
> > > > On Wed, Mar 04, 2026 at 04:23:30PM +0000, Conor Dooley wrote:
> > > > > On Wed, Mar 04, 2026 at 06:59:35AM -0800, Charles Perry wrote:
> > > > > > On Wed, Mar 04, 2026 at 11:15:43AM +0000, Conor Dooley wrote:
> > > > > > > On Tue, Feb 24, 2026 at 12:28:52PM -0800, Charles Perry wrote:
> > > > > > > > Make it possible to connect a PHY which does not use inband
> > > > > > > > autoneg to a gem MAC using phylink's information.
> > > > > > > > 
> > > > > > > > The previous implementation relied on whether or not the link
> > > > > > > > was a fixed-link to disable SGMII autoneg. This commit extend
> > > > > > > > this to all link which are not configured for inband
> > > > > > > > autonegotiation.
> > > > > > > > 
> > > > > > > > Signed-off-by: Charles Perry <charles.perry@microchip.com>
> > > > > > > 
> > > > > > > This breaks the macb on mpfs-icicle-kit, I get stuck with:
> > > > > > > 
> > > > > > > [    7.189102] mpfs-sys-controller syscontroller: Registered MPFS system controller
> > > > > > > [    7.260946] macb 20110000.ethernet eth0: PHY [20112000.ethernet-ffffffff:08] driver [Vitesse VSC8662] (irq=POLL)
> > > > > > > [    7.273881] macb 20110000.ethernet eth0: configuring for phy/sgmii link mode
> > > > > > > [    7.296580] macb 20110000.ethernet: gem-ptp-timer ptp clock registered.
> > > > > > > [    7.345782] macb 20112000.ethernet eth1: PHY [20112000.ethernet-ffffffff:09] driver [Vitesse VSC8662] (irq=POLL)
> > > > > > > [    7.358082] macb 20112000.ethernet eth1: configuring for phy/sgmii link mode
> > > > > > > [    7.380479] macb 20112000.ethernet: gem-ptp-timer ptp clock registered.
> > > > > > > [   11.376763] macb 20110000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
> > > > > > > [   11.398403] Sending DHCP requests .
> > > > > > > [   11.472699] macb 20112000.ethernet eth1: Link is Up - 1Gbps/Full - flow control off
> > > > > > > [   13.938425] ..... timed out!
> > > > > > > [   93.598491] macb 20110000.ethernet eth0: Link is Down
> > > > > > > [   93.641823] macb 20110000.ethernet: gem-ptp-timer ptp clock unregistered.
> > > > > > > [   93.659433] macb 20112000.ethernet eth1: Link is Down
> > > > > > > [   93.691724] macb 20112000.ethernet: gem-ptp-timer ptp clock unregistered.
> > > > > > > [   93.703977] IP-Config: Retrying forever (NFS root)...
> > > > > > > [   93.758382] macb 20110000.ethernet eth0: PHY [20112000.ethernet-ffffffff:08] driver [Vitesse VSC8662] (irq=POLL)
> > > > > > > [   93.770655] macb 20110000.ethernet eth0: configuring for phy/sgmii link mode
> > > > > > > [   93.786497] macb 20110000.ethernet eth0: Link is Up - 1Gbps/Full - flow control off
> > > > > > > [   93.795840] macb 20110000.ethernet: gem-ptp-timer ptp clock registered.
> > > > > > > [   93.844481] macb 20112000.ethernet eth1: PHY [20112000.ethernet-ffffffff:09] driver [Vitesse VSC8662] (irq=POLL)
> > > > > > > [   93.856769] macb 20112000.ethernet eth1: configuring for phy/sgmii link mode
> > > > > > > [   93.870926] macb 20112000.ethernet eth1: Link is Up - 1Gbps/Full - flow control off
> > > > > > > [   93.880302] macb 20112000.ethernet: gem-ptp-timer ptp clock registered.
> > > > > > > 
> > > > > > 
> > > > > > Hello Conor,
> > > > > > 
> > > > > > I checked the driver for the VSC8662 and it doesn't have the
> > > > > > ->inband_caps() and ->config_inband() callbacks so Linux leaves whatever
> > > > > > the bootloader puts or uses the defaults. Looking at the datasheet, this
> > > > > > should be register 23 (Extended PHY Control Set 1) bit 13 (MAC interface
> > > > > > auto-negotiation)
> > > > > > 
> > > > > > My guess is that this bit is set and since this patch disable inband
> > > > > > autonegotiation (because phylink decides it), there is a mismatch.
> > > > > > 
> > > > > > Can you add 'managed = "in-band-status"' in your device tree under the macb
> > > > > > node? That's not necessarily the fix, I just want to confirm my theory.
> > > > > 
> > > > > No, it just produces a different error:
> > > > > [    5.769864] mpfs-sys-controller syscontroller: Registered MPFS system controller
> > > > > [    5.829146] macb 20110000.ethernet eth0: Could not attach PHY (-19)
> > > > > [    5.854232] IP-Config: Failed to open eth0
> > > > > [    5.897152] macb 20112000.ethernet eth1: Could not attach PHY (-19)
> > > > > [    5.921061] IP-Config: Failed to open eth1
> > > > > [    5.925592] IP-Config: No network devices available
> > > > > [    5.938800] clk: Disabling unused clocks
> > > > > [    5.944156] PM: genpd: Disabling unused power domains
> > > > > [    5.961029] check access for rdinit=/usr/sbin/init failed: -2, ignoring
> > > > 
> > > > -19 is -ENODEV (I wish everyone would use %pe so we get english
> > > > error messages rather than having to look up errno codes in the
> > > > header files.)
> > > > 
> > > > macb uses either phylink_of_phy_connect() or phylink_connect_phy().
> > > > I don't think phylink_connect_phy() would return -ENODEV, but
> > > > phylink_of_phy_connect() would - but I can't see that adding
> > > > 'managed = "in-band-status";' to DT would cause that. The only
> > > > case I can see is that fwnode_phy_find_device() fails to find the
> > > > phydev, but there is a PHY node specified in DT, but that would
> > > > fail without in-band-status.
> > > 
> > > It's as you say, and fwnode_phy_find_device() is the source.
> > > fwnode_mdio_find_device() is what fails, returning NULL.
> > 
> > Ah, I've just found the reason:
> > 
> >         /* With fixed-link, we don't need to register the MDIO bus,
> >          * except if we have a child named "mdio" in the device tree.
> >          * In that case, some devices may be attached to the MACB's MDIO bus.
> >          */
> >         mdio_np = of_get_child_by_name(np, "mdio");
> >         if (!mdio_np && of_phy_is_fixed_link(np))
> >                 return macb_mii_probe(bp->dev);
> > 
> > of_phy_is_fixed_link() will return true as soon as you add that managed
> > property, and as the mac1 node just lists the PHYs without using a
> > mdio child:
> > 
> > &mac1 {
> >         phy-mode = "sgmii";
> >         phy-handle = <&phy1>;
> >         status = "okay";
> > 
> >         phy1: ethernet-phy@9 {
> >                 reg = <9>;
> >         };
> > 
> >         phy0: ethernet-phy@8 {
> >                 reg = <8>;
> >         };
> > };
> > 
> > it means mdio_np is NULL above. Hence, no MDIO bus will be created.
> 
> Thank you Russell for finding this.
> 
> Conor, can you try with this:
> 
> ````
> &mac0 {
> 	phy-mode = "sgmii";
> 	phy-handle = <&phy0>;
> 	status = "okay";
> 	managed = "in-band-status";
> };
> 
> &mac1 {
> 	phy-mode = "sgmii";
> 	phy-handle = <&phy1>;
> 	status = "okay";
> 	managed = "in-band-status";
> 
> 	mdio {
> 		phy1: ethernet-phy@9 {
> 			reg = <9>;
> 		};
> 	
> 		phy0: ethernet-phy@8 {
> 			reg = <8>;
> 		};
> 	};
> };
> ````
> 
> I think we're almost there.

With this, I can boot. Is that enough information for you to resolve the
problem?

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