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

From: Andrew Lunn <[email-masked]>
Date: Tue, 17 Sep 2019 14:54:34 +0200

On Tue, Sep 17, 2019 at 03:41:01PM +0300, tinywrkb 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.
> > 
> > 	Andrew
> 
> linux-test-5.1rc1-a2703de70942-without_bad_commit
> 
> Settings for eth0:
> 	Supported ports: [ TP MII ]
> 	Supported link modes:   10baseT/Half 10baseT/Full
> 	                        100baseT/Half 100baseT/Full
> 	                        1000baseT/Full

So this means the local device says it can do 1000Mbps.

> 	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

The link peer can also do 1000Mbps.

> 	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: 100Mb/s

Yet they have decided to do 100Mbps. 

We need to understand Why? The generic PHY driver would not do this on
its own. So i'm thinking something has poked a PHY register with some
value, and this patch is causing it to be over written.

Please can you use mii-tool -v -v to dump the PHY registers in each
case.

Thanks
	Andrew

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