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

From: Lukasz Majewski
Date: Tue May 30 2023 - 09:40:57 EST

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


DENX Software Engineering GmbH, Managing Director: Erika Unter
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