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

[Charles Perry <charles.perry@microchip.com>]

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.
> 

Conor,

Can you send us a snippet of you device tree showing the gem node and the
phy?

The idea behind adding 'managed = "in-band-status"' in the device tree is
to hint phylink to use MLO_AN_INBAND. I'm afraid we'll get the same result
if we come up with a different workaround.

Thanks,
Charles

> > > Also '#define DEBUG' in 'drivers/net/phy/phylink.c' can help if you can
> > > recompile your kernel.
> > 
> > Setting this provided no further logs, seemingly.
> 
> It certainly would if you place it before the first #include - I
> routinely build kernels with it set as such. The messages are produced
> at debug level, so should appear via "dmesg". If you want to see them
> on the console, you need to add "debug" to the kernel command line.
> 
> However, the in-band-status thing needs to be root-caused first.
> 
> -- 
> RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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