Subject: Re: [PATCH] ARM: dts: imx6dl: SolidRun: add phy node with 100Mb/s max-speed

From: Russell King - ARM Linux admin <[email-masked]>
Date: Sun, 15 Sep 2019 15:15:52 +0100

On Sun, Sep 15, 2019 at 03:06:39PM +0100, Russell King - ARM Linux admin wrote:
> On Sun, Sep 15, 2019 at 03:56:52PM +0200, Andrew Lunn wrote:
> > > Tinywrkb confirmed to me in private communication that revert of
> > > 5502b218e001 fixes Ethernet for him on effected system.
> > > 
> > > He also referred me to an old Cubox-i spec that lists 10/100 Ethernet
> > > only for i.MX6 Solo/DualLite variants of Cubox-i. It turns out that
> > > there was a plan to use a different 10/100 PHY for Solo/DualLite
> > > SOMs. This plan never materialized. All SolidRun i.MX6 SOMs use the same
> > > AR8035 PHY that supports 1Gb.
> > > 
> > > Commit 5502b218e001 might be triggering a hardware issue on the affected
> > > Cubox-i. I could not reproduce the issue here with Cubox-i and a Dual
> > > SOM variant running v5.3-rc8. I have no Solo/DualLite variant handy at
> > > the moment.
> > 
> > Could somebody with an affected device show us the output of ethtool
> > with and without 5502b218e001. Does one show 1G has been negotiated,
> > and the other 100Mbps? If this is true, how does it get 100Mbps
> > without that patch? We are missing a piece of the puzzle.
> 
> Hang on.  5502b218e001 is in 5.2 already - it was merged as part of the
> v5.1 merge window.  That means my imx6 Solo Hummingboard is already
> running it with the AR8035 PHY, and it works fine.
> 
> # dmesg
> ...
> OF: fdt: Machine model: SolidRun HummingBoard Solo/DualLite
> ...
> # ethtool eth0
> Settings for eth0:
>         Supported ports: [ TP MII ]
>         Supported link modes:   10baseT/Half 10baseT/Full
>                                 100baseT/Half 100baseT/Full
>                                 1000baseT/Full
>         Supported pause frame use: Symmetric
>         Supports auto-negotiation: Yes
>         Supported FEC modes: Not reported
>         Advertised link modes:  10baseT/Half 10baseT/Full
>                                 100baseT/Half 100baseT/Full
>                                 1000baseT/Full
>         Advertised pause frame use: Symmetric
>         Advertised auto-negotiation: Yes
>         Advertised FEC modes: Not reported
>         Link partner advertised link modes:  10baseT/Half 10baseT/Full
>                                              100baseT/Half 100baseT/Full
>                                              1000baseT/Full
>         Link partner advertised pause frame use: Symmetric
>         Link partner advertised auto-negotiation: Yes
>         Link partner advertised FEC modes: Not reported
>         Speed: 1000Mb/s
>         Duplex: Full
>         Port: MII
>         PHYAD: 0
>         Transceiver: internal
>         Auto-negotiation: on
>         Supports Wake-on: d
>         Wake-on: d
>         Link detected: yes

For some further testing, by changing the advertisment on the DSA
switch (other end of this platform's link):

        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half 100baseT/Full
...
        Speed: 100Mb/s
        Duplex: Full
===============
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
                                             100baseT/Half
...
        Speed: 100Mb/s
        Duplex: Half
===============
        Link partner advertised link modes:  10baseT/Half 10baseT/Full
...
        Speed: 10Mb/s
        Duplex: Full
===============
        Link partner advertised link modes:  10baseT/Half
...
        Speed: 10Mb/s
        Duplex: Half

So it looks like the commit works as it should.  So there's something
else going on.

Note that the FEC does *not* support 1000baseT/Half.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line in suburbia: sync at 12.1Mbps down 622kbps up
According to speedtest.net: 11.9Mbps down 500kbps up

_______________________________________________
linux-arm-kernel mailing list
[email-masked]
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel