Subject: Re: [RFC] net: dsa: slave: Advertise correct EEE capabilities at slave PHY setup

From: Lukasz Majewski <[email-masked]>
Date: Tue, 30 May 2023 15:40:39 +0200

Hi Andrew,

> On Tue, May 30, 2023 at 02:26:21PM +0200, Lukasz Majewski wrote:
> > One can disable in device tree advertising of EEE capabilities of
> > PHY when 'eee-broken-100tx' property is present in DTS.
> > 
> > With DSA switch it also may happen that one would need to disable
> > EEE due to some network issues.  
> 
> Is EEE actually broken in the MAC/PHY combination?
> 

Problem is that when I connect on this project some non-manageable
switches (which by default have EEE enabled), then I observe very rare
and sporadic link loss and reconnection.

Disabling EEE solves the problem.

> You should not be using this DT option for configuration. It is there
> because there is some hardware which is truly broken, and needs EEE
> turned off.

Yes, I do think that the above sentence sums up my use case.

> 
> If EEE does work, but you need to turn it off because of latency etc,
> then please use ethtool.
> 

Yes, correct - it is possible to disable the EEE with 

ethtool --set-eee lan2 eee off

However, as I've stated in the mail, I cannot re-enable EEE once
disabled with:

ethtool --set-eee lan2 eee on

ethtool --show-eee lan2
EEE Settings for lan2:
        EEE status: not supported

As the capability register shows value of 0.

>      Andrew,

Best regards,

Lukasz Majewski

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